UWorld Step 1 Flashcards
(158 cards)
1
Q
Blood brain barrier
A
Formed by tight junctions between nonfenestrated capillary endothelial cells that prevent the paracellular passage of fluid and solutes. This barrier only permits passage of substances from the blood to the brain via trans cellular movement across the endothelial plasma membrane, which is limited by diffusion or carrier-mediated transport.
2
Q
Radial nerve injury - supinator canal
A
Injury to the radial nerve during its passage through the supinator canal may occur due to repetitive pronation/supination of the forearm, direct trauma, or subluxation of the radius. Patients typically have weakness during finger and thumb extension (“finger drop”) without wrist drop or sensory deficits.
3
Q
Common peroneal nerve injury
A
Trauma/sustained pressure to the neck of the fibula can injure the common peroneal nerve, causing weakness on foot dorsiflexion (“foot drop”) and eversion, as well as toe extension, and impaired sensation over the lateral shin and dorsal foot, and between the first and second toes.
4
Q
Femoral nerve block
A
A femoral nerve block at the inguinal crease will anesthetize the skin and muscles of the anterior thigh (eg, quadriceps), femur, and knee.
5
Q
Down syndrome Alzheimer risk
A
Patients with trisomy 21 (Down syndrome) have 3 copies of the amyloid precursor protein gene located on chromosome 21. This increases amyloid-beta accumulation in the brain, placing these patients at high risk for developing early-onset Alzheimer disease
6
Q
Iliohypogastric nerve injury - s/p appendectomy
A
The iliohypogastric nerve provides sensation to the suprapubic and gluteal regions and motor function to the anterolateral abdominal wall muscles. Abdominal surgery (eg, appendectomy) can damage the nerve and cause decreased sensation and/or burning pain at the suprapubic region.
7
Q
Complete contralateral sensory loss
A
The ventral posterior lateral nucleus (receives input from the spinothalamic tract and dorsal columns) and ventral posterior medial nucleus (receives input from the trigeminal pathway) of the thalamus send somatosensory projections to the cortex via thalamocortical fibers. Damage to these nuclei results in complete contralateral sensory loss.
8
Q
Lacunar infarcts
A
Lacunar infarctions are small ischemic infarcts (<15 mm in diameter) and are usually the result of small vessel occlusion (eg, due to lipohyalinosis, microatheroma formation, and hardening/thickening of the vessel wall - hypertensive arteriolar sclerosis) in the penetrating vessels supplying the deep brain structures (eg, basal ganglia, pons) and subcortical white matter (eg, internal capsule, corona radiata). Uncontrolled hypertension and diabetes mellitus are major risk factors for this condition.
9
Q
Focal seizure - postcentral gyrus
A
The primary somatosensory cortex (postcentral gyrus) is responsible for processing all somatic sensory modalities (eg, touch, temperature/pain, vibration/proprioception) of the contralateral body. A partial (focal) seizure originating in this cortical region can result in contralateral sensory disturbance (eg, numbness, paresthesias).
10
Q
Elevated levels of AFP and AChE on amniocentesis
A
Neural tube defects most often occur when the neural folds fail to fuse in the region of the anterior or posterior neuropores. Persistent communication between the spinal canal and the amniotic cavity allows leakage of alpha-feroprotein (AFP) and acetylcholinesterase (AChE) into the amniotic fluid, leading to elevated levels of AFP and AChE that can be detected on amniocentesis.
11
Q
Changes in membrane potential
A
Occur in response to changes in the neuronal membrane permeability to various cellular ions. The more permeable the membrane becomes for a cellular ion, the more that ion’s equilibrium potential contributes to total membrane potential.
12
Q
ACA occlusion
A
The anterior cerebral arteries supply the medial portions of the 2 hemispheres (frontal and parietal lobes). Occlusion can cause contralateral motor and sensory deficits of the lower extremities, behavioral changes, and urinary incontinence.
13
Q
Huntington disease - histone acetylation
A
Hypo-acetylated histones bind tightly to DNA and prevent transcription of genes in their associated regions. Alteration of gene expression in Huntington disease occurs in part due to deacetylation of histones. This prevents the transcription of certain genes that code for neurotrophic factors, contributing to neuronal cell death.
14
Q
Meyer’s loop - injury
A
Injury to Meyer’s loop in the temporal lobe results in contralateral superior quadrantanopia.
15
Q
Acute nausea s/p chemo
A
Acute nausea following administration of systemic chemotherapy results from stimulation of the chemoreceptor trigger zone (CTZ), which lies in the area postrema of the dorsal medulla near the fourth ventricle.
16
Q
Neuron action potential - K+ ion permeability
A
The action potential results from changes in the membrane permeability to K+ and Na+ ions. Depolarizations results from massive influx of Na+ through voltage-gated Na+ channels. Repolarization occurs due to closure of voltage-gated Na+ channels and opening of voltage-gated K+ channels. K+ ion permeable is highest during the repolarization phase of the action potential.
17
Q
Broca aphasia
A
Broca (motor, nonfluent) aphasia results from damage to the inferior frontal gyrus of the dominant hemisphere. Patients are often frustrated as they understand language but cannot properly formulate the motor commands to write or form words (eg, slow, fragmented speech). Aphasia may be associated with right upper limb and face weakness due to extension of the lesion into the primary motor cortex.
18
Q
PICA occlusion
A
Posterior inferior cerebellar artery occlusion causes lateral medullary (Wallenberg) syndrome, characterized by vertigo/nystagmus, ipsilateral cerebellar signs, loss of pain/temperature sensation in the ipsilateral face and contralateral body, bulbar weakness, and ipsilateral Horner syndrome. This condition can occur in the setting of cervical spine trauma with dissection of the vertebral artery.
19
Q
CN IV palsy
A
The trochlear nerve innervates the superior oblique muscle, which causes the eye to intort (internally rotate) and depress with adducted. Trochlear nerve palsy is typically traumatic or idiopathic and presents with vertical diplopia that worsens when the affected eye looks down and toward the nose (eg, walking downstairs, up-close reading). Patients may compensate by tucking the chin and tilting the head away from the affected eye.
20
Q
Sciatic - S1 clinical presentation
A
Sciatica is a nonspecific term for low back pain that radiates down the leg due to compression of the lumbosacral nerve roots (eg, from vertebral disc herniation). The S1 nerve root is commonly involved, resulting in pain/sensory loss down the posterior thigh and calf to the lateral aspect of the foot. Patients may also have weakness on thigh extension, knee flexion, and foot plantarflexion with an absent ankle jerk reflex.
21
Q
Kinesin
A
Kinesin is a microtubule-associated, ATP-powered motor protein that facilitates the anterograde transport of neurotransmitter-containing secretory vesicles down axons to synaptic terminals.
22
Q
Spontaneous deep intracerebral hemorrhage
A
Spontaneous deep intracerebral hemorrhage is typically caused by hypertensive vasculopathy involving the penetrating branches of the major cerebral arteries. The most frequently affected locations include the basal ganglia (putamen), cerebellar nuclei, thalamus, and pons. The basal ganglia are supplied by the lenticulostriate arteries, which are small vessel branches off the middle cerebral artery.
23
Q
“Red ragged” muscle fibers
A
“Red ragged” muscle fibers are seen in mitochondrial diseases. Muscle fibers have this appearance because abnormal mitochondria accumulate under the sarcolemma. Mitochondrial diseases show maternal inheritance.
24
Q
Musculocutaneous nerve
A
The musculocutaneous nerve innervates the major forearm flexors (eg, biceps brachii, brachialis) and coracobrachialis (flexes and adducts the arm) and provides sensory innervation to the lateral forearm. It is derived from the upper trunk of the brachial plexus (C5-C7) and can be injured by trauma or strenuous upper extremity exercise.
25
Hydrocephalus - infant
Hydrocephalus in infants presents with macrocephaly and poor feeding. Imaging studies showing enlarged ventricles are characteristic. Untreated hydrocephalus leads to spasticity due to stretching of the periventricular pyramidal tracks, development delays, and seizures.
26
Alzheimer disease - ACh
Alzheimer disease is characterized by decreased levels of acetylcholine in the nucleus basalis of Meynert and the hippocampus, caused by diminished activity of choline acetyltransferase.
27
Acoustic neuromas
Acoustic neuromas are Schwann cell-derived tumors that typically arise from the vestibular portion of the vestibulocochlear nerve and are commonly located at the cerebellopontine angle (between the cerebellum and lateral pons). Patients usually present with unilateral sensorineural hearing loss and tinnitus.
28
Disrupted first and second pharyngeal arches
The development of derivatives of the first (eg, trigeminal nerve, mandible, maxilla, zygoma, incus, malleus) and second (eg, facial nerve, stapes, styloid process, lesser horn of hyoid) pharyngeal arches can by disrupted in genetic disorders (eg, Treacher-Collins syndrome), resulting in hypoplasia of the mandibular and zygomatic bones.
29
Interscalene nerve block
Interscalene nerve block anesthetizes the brachial plexus as it passes through the scalene triangle. It is used to provide anesthesia for the shoulder and upper arm. Nearly all patients develop transient ipsilateral diaphragmatic paralysis due to involvement of the phrenic nerve roots as they pass through the interscalene sheath.
30
Internuclear ophthalmoplegia
Internuclear ophthalmoplegia is a disorder of conjugate horizontal gaze in which the affected eye (ipsilateral to the lesion) is unable to adduction and the contralateral eye abducts with nystagmus. Convergence and the pupillary light reflex are preserved. This typically occurs with damage to the medial longitudinal fasciculus.
31
ICA aneurysm
An aneurysm of the internal carotid artery can laterally impinge on the optic chiasm. This can cause ipsilateral nasal hemianopia by damaging uncrossed optic fibers from the temporal portion of the retina.
32
NF-1
Neurofibromatosis type I (von Recklinghausen disease) is a single-gene autosomal dominant disorder caused by mutations in the NF1 tumor suppressor gene located on chromosome 17. Patients characteristically develop numerous cutaneous neurofibromas comprised mostly of Schwann cells, which are embryologically derived from the neural crest. Other common symptoms include café-au-lait spots and Lisch nodules.
33
Fragile X syndrome
Fragile X syndrome, an X-linked disorder, is the most common cause of inherited intellectual disability. The pathogenesis involves an unstable expansion of trinucleotide repeats (CGG) in the fragile X retardation 1 (FMR1) gene. Key physical findings include dysmorphic facial features (eg, large jaw, protruding ears, long face) and macroorchidism.
34
3-5 days after ischemic brain infarct
Microfilm move to the area of ischemic infarct approximately 3-5 days after the onset of ischemia and phagocytize the fragments of neurons, myelin, and necrotic debris. A cystic space replaces the necrosis, and astrocytes form a glial scar along the periphery.
35
Drug binding and activating GABA-A receptors
A drug that binds to activate GABA-A receptors (or enhances their activity) will increase the conductance of chloride ions, leading to increased passive transport of chloride into the cell interior. This causes the membrane potential to become hyperpolarized (more negative than the resting membrane potential) by approaching or reaching the equilibrium potential for chloride.
36
Schwannomas
Schwannomas present histologically with a biphasic pattern of cellularity (Antoni A and B areas) and S-100 positivity (indicating neural crest origin). Schwannomas can arise from the peripheral nerves, nerve roots, and cranial nerves (except CN II). Acoustic neuromas are the most common type of intracranial schwannoma and are located at the cerebellopontine angle at CN VIII.
37
ALS
Amyotrophic lateral sclerosis (ALS) causes both upper and lower motor neuron lesions. Loss of neurons of the anterior horns of the spinal cord (LMN lesion) causes muscle weakness and atrophy. Demyelination of the lateral corticospinal tract (UMN lesion) leads to spasticity and hyperreflexia.
38
Parkinson disease - high-frequency deep brain stimulation
Nigrostriatal degeneration in Parkinson disease reduces activity of the thalamus and its projections to the cortex, resulting in bradykinesia and rigidity. Patients with medically intractable symptoms of Parkinson disease may benefit from high-frequency deep brain stimulation of the globus pallidus internus or subthalamic nucleus as it promotes thalamo-cortical disinhibition with improved mobility
39
Direct and consensual pupillary light reflex
The upper midbrain contains neural structures (eg, optic nerve, pretectal nuclei, Edinger-Westphal nuclei, oculomotor nerve) that mediate the direct and consensual pupillary light reflex.
40
Wallerian degeneration
Wallerian degeneration refers to the process of axonal degeneration and breakdown of the myelin sheath that occurs distal to the site of injury. Axonal regeneration does not occur in the central nervous system due to the persistence of myelin debris, secretion of neuronal inhibitory factors, and development of dense glial scarring.
41
Uncal herniation
Transtentorial (i.e., uncal) herniation is a complication of an ipsilateral mass lesion, such as a hemorrhage or brain tumor. The first sign of uncal herniation is a fixed and dilated pupil on the side of the lesion. Ipsilateral paralysis of oculomotor muscles (compressed as it exits the midbrain, resulting in oculomotor nerve pays with fixed dilated pupil - due to preganglionic parasympathetic fiber damage), contralateral or ipsilateral hemiparesis, and contralateral homonymous hemianopsia with macular sparing may also occur.
42
Ectoderm adult derivatives
All adult cells and tissues can be traced back to the 3 primary germ layers (ectoderm, mesoderm, and endoderm). The ectoderm gives rise to the surface ectoderm, neural tube, and neural crest.
43
Tetanospasmin
Tetanospasmin is a neuro-exotoxin released by Clostridium tetani. The toxin blocks the release of glycine and gamma-aminobutyric acid (GABA) from the spinal inhibitory interneurons that regulate the lower motor neurons. These disinhibited motor neurons cause increased activation of muscles, leading to spasms and hyperreflexia.
44
Normal-pressure hydrocephalus
Normal-pressure hydrocephalus is the result of decreased cerebrospinal fluid (CSF) resorption by the arachnoid granulation. The classic triad of symptoms consists of progressive gait difficulties, cognitive disturbances, and urinary incontinence. Brain imaging reveals ventricular enlargement that is out of proportion to sulci enlargement.
45
Optic tract lesion
A lesion in the optic tract can produce contralateral homonymous hemianopia and a relative afferent pupillary defect (Marcus Gunn pupil) in the pupil contralateral to the tract lesion.
46
Cystic tumor in cerebellum - child
A cystic tumor in the cerebellum of a child is most likely pilocytic astrocytoma. Biopsy will show a well-differentiated neoplasm comprised of spindle cells with hair-like glial processes that are associated with microcysts. These cells are mixed with Rosenthal fibers and granular eosinophilic bodies.
47
Epidural hematoma
Epidural hematoma occurs due to tear of the middle meningeal artery. It is often associated with temporal bone fracture and is located between the bone and dura mater. Clinical presentation is characterized by a “lucid interval”, followed by loss of consciousness.
48
Herpes encephalitis - CSF
Viral infections of the central nervous system are usually characterized by elevated protein, normal glucose, and an elevated white blood cell count with a lymphocytic predominance. Patients with herpes encephalitis also usually have elevated erythrocytes in the cerebrospinal fluid due to hemorrhagic inflammation of the temporal lobes.
49
Muscarinic receptor activation
Activation of muscarinic receptors by acetylcholine or cholinergic agonist results in peripheral vasodilation due to synthesis of nitric oxide in endothelial cells, which leads to vascular smooth muscle relaxation (eg, hypotension). Muscarinic receptor activation in other sites causes smooth muscle contraction.
50
Wilson disease
Wilson disease (hepatolenticular degeneration) is an autosomal recessive condition of excess copper leading to toxic accumulation in the liver, basal ganglia, and cornea. Chelation therapy with D-penicillamine is indicated to remove excess loosely bound serum copper.
51
Tetanus
Tetanus is a clinical diagnosis that should be suspected in patients who have characteristic symptoms (eg, lockjaw, muscle pain/spasms, difficulty swallowing), particularly if they are unlikely to be adequately vaccinated or have an antecedent cutaneous injury.
52
Alzheimer disease
Alzheimer dementia typically presents insidiously with memory loss (especially of recent events), executive dysfunction, and visuospatial impairment. Classic histopathologic findings include amyloid plaques (central amyloid beta core surrounded by dystrophic neurites) and neurofibrillary tangles (aggregated of hyperphosphorylated tau protein).
53
Light reflex pathway - optic nerve damage
The afferent limb of the light reflex pathway is the optic nerve; the efferent limb is the parasympathetic fibers of the oculomotor nerve. Where an optic nerve is damaged, light in that eye will cause neither pupil to constrict (the nerve can’t see the light). However, light in the contralateral eye will cause both pupils to constrict (because the motor pathways are intact).
54
Thiamine deficiency
Thiamine (i.e., vitamin B1) deficiency acutely leads to Wernicke encephalopathy and chronically leads to Korsakoff psychosis. The neural structure most frequently affect in patients with Wernicke encephalopathy is the mammillary body, which is part of the Papez circuit. Alcoholic or malnourished patients should receive intravenous thiamine supplementation before intravenous dextrose administration because giving dextrose without prior thiamine can precipitate a Wernicke encephalopathy.
55
Speed of conduction down an axon
The speed of conduction down an axon depends on 2 constants: the length constant and the time constant (ie, velocity = length/time). Myelination increases the length constant and decreases the time constant, both of which improve axonal conduction speed. Demyelination thus impairs stimulus transmission.
56
Opsoclonus-myoclonus
Opsoclonus-myoclonus is a paraneoplastic syndrome associated with neuroblastoma, the most common extracranial solid neoplasm in children. The tumor typically arises from the neural crest cells of the adrenal medulla and presents with an abdominal mass and elevated catecholamine breakdown products.
57
Cerebellar hemisphere lesion
The cerebellar hemispheres are responsible for motor planning and coordination of the ipsilateral extremities via their connections with the lateral descending motor systems. Consequently, cerebellar hemispheres lesions typically result in ipsilateral dysdiadochokinesia, limb dysmetria, and intention tremor.
58
Neonatal intraventricular hemorrhage
Neonatal intraventricular hemorrhage usually occurs in the fragile germinal matrix and increases in frequency with decreasing age and birth weight. It is a common complication of prematurity that can lead to long-term neurodevelopmental impairment.
59
Neuroleptic malignant syndrome
Neuroleptic malignant syndrome is a life-threatening adverse reaction to antipsychotic medications characterized by diffuse muscle rigidity, hyperthermia, autonomic instability, and altered sensorium. The antipsychotic should be stopped and supportive care provided, and dantrolene can be used to reduce muscle rigidity.
60
CN III injury - aneurysm
The oculomotor nerve (CN III) courses between the posterior cerebral and superior cerebellar arteries as it exits the midbrain in the interpeduncular space and is particularly susceptible to injury from ipsilateral posterior communicating artery aneurysms. Aneurysmal compression of CN III produces mydriasis (due to superficial parasympathetic fiber damage) with diplopia, ptosis, and “down and out” deviation of the ipsilateral eye (due to somatic efferent fiber injury).
61
Status epilepticus - Tx
Intravenous benzodiazepines (eg, lorazepam) are the initial drug of choice for status epilepticus. They work by enhancing the effect of gamma-aminobutyric acid (GABA) at the GABA-A receptor, leading to increased chloride influx and suppression of action potential firing.
62
Obturator nerve injury
The obturator nerve is the only major nerve that exits the pelvis through the obturator foramen. Nerve injury typically results from compression (eg, due to pelvic trauma, surgery, or tumor) and presents with weakness on thigh adduction and sensory loss over the distal medial thigh.
63
Malignant tumor parotid gland - nerve compression
The facial nerve (CN VII) exits the stylomastoid foramen and courses through the substance of the parotid gland, where it divides into its 5 terminal branches that innervate the muscles of facial expression. Malignant tumors of the parotid gland often compress and disrupt the facial nerve and its branches, causing ipsilateral face droop.
64
Arteriovenous concentration gradient
The arteriovenous concentration gradient reflects the overall tissue solubility of an anesthetic. Anesthetics with high tissue solubility are characterized by large arteriovenous concentration gradients and slower onsets of action.
65
Essential tremor
Essential tremor is the most common movement disorder. Patients experience a slowly progressive, symmetric postural and/or kinetic tremor that most commonly affects the upper extremities. Essential tremor is often inherited in an autosomal dominant fashion (referred to as familial tremor). First-line treatment is the nonspecific beta-adrenergic antagonist propranolol.
66
Several months to years after ischemic brain infarct
Several months to years after ischemic brain infarction, the necrotic area appears as a cystic cavity surrounded by a wall composed of dense fibers formed by astrocytic processes (glial scar).
67
Isoniazid-induced neuropathy
Isoniazid is structurally similar to pyridoxine (vitamin B6). As a result, this antibiotic increases the urinary excretion of pyridoxine – often causing a frank deficiency of vitamin B6 – and competes for vitamin B6-binding sites, leading to the defective synthesis of neurotransmitters like GABA. Isoniazid-induced neuropathy can usually be prevented with pyridoxine supplementation.
68
Severe vasospasm s/p subarachnoid hemorrhage
Subarachnoid hemorrhage occurs due to rupture of saccular (berry) aneurysm or arteriovenous malformation. Severe vasospasm 4-12 days after the initial insult is the major cause of morbidity and mortality in patients recovering from SAH. Nimodipine, a selective calcium channel blocker, is often prescribed to prevent this vasospasm.
69
Opiate analgesics
Opiate analgesics reduce pain by binding to mu receptors and inhibiting synaptic activity in the central nervous system. Activation of presynaptic mu receptors on the primary afferent neuron leads to closure of voltage-gated calcium channels and reduced excitatory neurotransmitter release. Binding to mu receptors on the postsynaptic membrane causes opening of potassium channels and membrane hyperpolarization.
70
Auscultation - mitral stenosis
The classic cardiac auscultation findings in mitral valve stenosis include an early diastolic opening snap (caused by the sudden opening of the mitral valve leaflets when the left ventricular pressure falls below the left atrial pressure at the beginning of diastole) followed by a low-pitched diastolic rumbling murmur that is heard best over the apex of the heart. On the pressure-volume loop, mitral valve opening occurs at the point between isovolumetric relaxation and diastolic filling.
71
IVC filter
The inferior vena cava (IVC) courses through the abdomen and inferior thorax in a location anterior to the right half of the vertebral bodies. The renal veins join the IVC at the level of L1/L2, and the common iliac veins merge to become the IVC at the level of L5. IVC filters are placed in patients with deep venous thrombosis who have contraindications to anticoagulation therapy.
72
Auscultation - tricuspid regurgitation
An early systolic murmur best heard over the left lower sternal border that is accentuated by inspiration is most likely due to tricuspid regurgitation.
73
Patent foramen ovale - adult
The foramen ovale is patent in approximately 25% of normal adults. Although the foramen ovale usually remains functionally closed, transient increases of right atrial pressure above left atrial pressure can produce a right-to-left shunt, leading to paradoxical embolism of venous clots into the arterial circulation.
74
LA enlargement
The left atrium forms the majority of the posterior surface of the heart and resides adjacent to the esophagus. Enlargement of the left atrium can compress the esophagus and cause dysphasia.
75
Most deoxygenated blood in body
Myocardial oxygen extraction exceeds that of any other tissue or organ; therefore, the cardiac venous blood in the coronary sinus is the most deoxygenated blood in the body. Due to high degree of oxygen extraction, increases in myocardial oxygen demand can only be met by an increase in coronary blood flow.
76
Right-sided pressures in the heart
Right-sided pressures in the heart are lower than left-sided pressures due to lower resistance from pulmonary vasculature. Right ventricular diastolic pressure is similar to right atrial/central venous pressure (1-6 mm Hg), whereas pulmonary artery diastolic pressure is slightly higher (6-12 mm Hg) due to resistance to flow in the pulmonary circulation.
77
Chronic arteriovenous shunt
A chronic arteriovenous shunt would increase cardiac output because of increased sympathetic simulation to the heart, decreased total peripheral resistance, and increased venous return. It would also cause the venous return curve to shift to the right because the circulating blood volume is increased through renal retention of fluids and because venous pooling is reduced by increased sympathetic tone.
78
IV infusion - pressure-volume loop
Pressure-volume loops represent the relationship between pressure and volume in the left ventricle during systole and diastole. An increase in the circulating volume increases preload (left ventricular end-diastolic volume) and causes a rightward widening of the pressure-volume loop.
79
ANP
Atrial netriuretic peptide (ANP) is secreted by atrial cardiomyocytes in response to atrial stretch induced by hypertension or hypervolemia. ANP causes peripheral vasodilation and increased urinary excretion of sodium and water. Neprilsyin inhibitors (eg, sacubitril) prevent the degradation of ANP, enhancing its beneficial hemodynamic effects in heart failure patients.
80
Aortic valve opening - ventricular pressure and volume curves
Ventricular pressure and volume curves allow one to identify the phases of the cardiac cycle and to determine the exact time of opening and closure of the cardiac valves. The aortic valve opens when left ventricular pressure exceeds the central aortic pressure at the end of isovolumetric contraction.
81
NO
Nitric oxide is the most important mediator of coronary artery vascular dilation in large arteries and pre-arteriolar vessels. It is synthesized from arginine (supplementation of arginine may play an adjunct role in the treatment of conditions that improve with vasodilation, such as stable angina) and oxygen by endothelial cells and causes vascular smooth muscle relaxation by guanylate cyclase-mediated cGMP second messenger system. Adenosine, a product of ATP metabolism, acts as a vasodilator element in the small coronary arterioles.
82
TGA - echocardiogram
An echocardiogram showing an aorta lying anterior to the pulmonary artery is diagnostic of transposition of the great arteries (TGA). This life-threatening cyanotic condition results from failure of the fetal aorticopulmonary septum to spiral normally during septation of the truncus arterious.
83
Inferior epigastric artery
The inferior epigastric artery is 1 of 2 branches of the external iliac artery and takes off immediately proximal to the inguinal ligament. It provides blood supply to the lower anterior abdominal wall as it runs superiorly and medially up the abdomen.
84
Stanford type A vs B aortic dissection
The intimal tear in Stanford type A aortic dissection (involving the ascending aorta) usually originates in the sinotubular junction whereas the intimal flap in Stanford type B aortic dissection usually starts near the origin of the left subclavian artery. Dissections can propagate distally to the thoracoabdominal aorta.
85
Papillary muscle rupture s/p MI
Papillary muscle rupture is a life-threatening complication that typically occurs 3-5 days after myocardial infarction and presents with acute mitral regurgitation and pulmonary edema. The posteromedial papillary muscle is supplied solely by the posterior descending artery, making it susceptible to ischemic rupture.
86
ST elevation - leads I and avL
Leads I and aVL correspond to the lateral limb leads on ECG. Therefore, ST elevation or Q waves in these leads are indicative of infarction involving the lateral aspect of the left ventricle, which is supplied by the left circumflex artery.
87
Great saphenous vein
The great saphenous vein is a superficial vein of the leg that originates on the medial side of the foot, courses anterior to the medial malleolus, and then travels up the medial aspect of the leg and thigh. It drains into the femoral vein within the region of the femoral triangle, a few centimeters inferolateral to the pubic tubercle.
88
Cardiac pacemaker action potential - phase 4
The phase 4 slow depolarization in cardiac pacemaker cells occurs due to the closure of repolarizing K+ channels, the slow influx of Na+ through funny channels, and the opening of T-type Ca2+ channels. Acetylcholine and adenosine reduce the rate of spontaneous depolarization in cardiac pacemaker cells by prolonging phase 4.
89
Patent ductus arteriosus
The ductus arteriosus is derived from the sixth embryonic aortic arch. A patent ductus arteriosus causes left-to-right shunting of blood that can be heard as a continuous murmur over the left infraclavicular region. Indomethacin (a PGE2 inhibitor) can be used to close a PDA in premature infants, but surgical ligation is often necessary in older patients.
90
Cardiac/smooth vs skeletal muscle - calcium-channel blockers
Contraction inhibition in cardiac and smooth muscle cells is dependent on extracellular calcium influx through L-type calcium channels, which can be prevented by calcium-channel blockers (eg, verapamil). Skeletal muscle is resistant to calcium channel blockers, as calcium release by the sarcoplasmic reticulum is triggered by a mechanical interaction between L-type and RyR calcium channels.
91
S3 heart sound
The third heart sound (S3) is a low-frequency sound occurring during early diastole after S2. Left ventricular gallops (S3 and/or S4) are best heard with the bell of the stethoscope over the cardiac apex while the patient is in the left lateral decubitus position at end expiration.
92
Volume output - LV vs RV
The circulatory system is a continuous circuit, and therefore the volume output of the left ventricle must closely match the output of the right ventricle. This balance is necessary to maintain continuous blood flow through the body and exists both at rest and during exercise.
93
Vessel radius - effects on blood flow and resistance
Blood flow is directly proportional to the vessel radius raised to the fourth power. Resistance to blood flow is inversely proportional to the vessel radius raised to the fourth power.
94
Aortic regurgitation
Aortic regurgitation causes an increase in total stroke volume with abrupt distension and rapid falloff of peripheral arterial pulses, resulting in a wide pulse pressure. This leads to bounding peripheral pulses and head bobbing with each heartbeat.
95
SA node
The sinoatrial node consists of specialized pacemaker cells located at the junction of the right atrium and superior vena cava. It is the site of earliest activation in patients with sinus rhythm.
96
Cardiac myocyte action potential
The cardiac myocyte action potential consists of rapid depolarization (phase 0), initial rapid repolarization (phase 1), plateau (phase 2), late rapid repolarization (phase 3), and resting potential (phase 4). The action potential is associated with increased membrane permeability to Na+ and Ca2+ and decreased permeability to K+.
97
Nitoprusside
Nitroprusside is a short-acting balanced venous and arterial vasodilator that decreases both preload and afterload. Since these changes are balanced, stroke volume is maintained.
98
Skull fracture - subsequent hematoma
The middle meningeal artery is a branch of the maxillary artery, which enters the skull at the foramen spinosum and courses intracranially deep to the pterion (where the frontal, parietal, temporal and sphenoid bones meet). Skull fractures at this site may cause laceration of this vessel, leading to an epidural hematoma.
99
Ca2+ efflux - cardiac cells
Calcium efflux from cardiac cells prior to relaxation is primarily mediated via an Na+/Ca2+ exchange pump and sarcoplasmic reticulum Ca2+-ATPase pump.
100
Intracardiac fistula between aortic root and RV
During the normal cardiac cycle, central aortic pressure is higher than right ventricular pressure during systole and diastole. Consequently, an intracardiac fistula between the aortic root and the right ventricle will most likely demonstrate a left-to-right cardiac shunt as blood continuously flows from the aortic root (high pressure) to the right ventricle (low pressure)
101
Compensated HF
In patients with heart failure, compensatory activation of the renin-angiotensin-aldosterone pathway and sympathetic nervous system results in increased afterload (from excessive vasoconstriction), excess fluid retention, and deleterious cardiac remodeling.
102
Isolated systolic HTN
Isolated systolic hypertension (systolic blood pressure >140 mmHg with diastolic blood pressure <90 mmHg) is due to age-related stiffness and decrease in compliance of the aorta and major peripheral arteries.
103
Common cardinal veins - adult derivatives
The common cardinal veins of the developing embryo drain directly into the sinus venosus. These cardinal veins ultimately give rise to the superior vena cava and other constituents of systemic venous circulation.
104
Subclavian steal syndrome
Subclavian steal syndrome occurs due to severe stenosis of the proximal subclavian artery, which leads to reversal in blood flow from the contralateral vertebral artery to the ipsilateral vertebral artery. Patients may have symptoms related to arm ischemia in the affected extremity (eg, exercise-induced fatigue, pain, paresthesias) or vertebrobasilar insufficiency (eg, dizziness, vertigo).
105
Tetralogy of Fallot - squatting
In patients with Tetralogy of Fallot, squatting during a Tet spell increases systemic vascular resistance and decreases right-to-left shunting, thereby increasing pulmonary blood flow and improving oxygenation status.
106
Heart in relation to L midclavicular line
The left ventricle forms the apex of the heart and can reach as far as the fifth intercostal space at the left midclavicular line (MCL). All other chambers of the heart lie medial to the left MCL. The lungs overlap much of the anterior surface of the heart.
107
Carotid sinus reflex
The carotid sinus is a dilation of the internal carotid artery located just above the bifurcation of the common carotid artery. The carotid sinus reflex has an afferent limb that arises from the baroreceptors in the carotid sinus and travels to the vagal nucleus and medullary centers via the glossopharyngeal nerve (CN IX); the efferent limb carries parasympathetic impulses via the vagus nerve (CN X).
108
Biventricular pacemakers - L leads
Left ventricular leads in biventricular pacemakers course through the coronary sinus, which resides in the atrioventricular groove on the posterior aspect of their heart.
109
Brachiocephalic vein obstruction
The brachiocephalic vein drains the ipsilateral jugular and subclavian veins. The bilateral brachiocephalic veins combine to form the superior vena cava (SVC). Brachiocephalic vein obstruction causes symptoms similar to those seen in SVC syndrome, but on only one side of the body.
110
Carotid sinus massage
Carotid sinus massage leads to an increase in parasympathetic tone causing temporary inhibition of sinoatrial node activity, slowing of conduction through the atrioventricular (AV) node, and prolongation of the AV node refractory period. It is a useful vagal maneuver for termination of paroxysmal supraventricular tachycardia.
111
Cardiac pacemaker impulse generation
Cardiac pacemaker impulse generation normally occurs in the SA node, which has the fastest firing rate of all conductive cells. The cells in other areas of the conduction system (eg, AV node, bundle of His, and Purkinje fibers) may serve as pacemakers if normal impulse conduction is impaired.
112
HCM
Hypertrophic cardiomyopathy (HCM) typically involves asymmetric interventricular septal hypertrophy that obstructs left ventricular (LV) outflow and creates a systolic murmur that decreases in intensity with maneuvers that increase LV end-diastolic volume (eg, hand grip, passive leg elevation that increase preload or afterload). HCM is characterized by increased LV muscle mass with a small LV cavity, preserved ejection fraction, and impaired LV relaxation leading to diastolic dysfunction.
113
Cardiac action potential speed
The cardiac action potential conduction speed is slowest in the atrioventricular node and fastest in the Purkinje system. Conduction speed of the atrial muscle is faster than that of the ventricular muscle.
114
Afib
Atrial fibrillation occurs due to irregular, chaotic activity within the atria and presents with absent P waves, irregularly irregular R-R intervals, and narrow QRS complexes. The atrioventricular node refractory period regulates the number of atrial impulses that reach the ventricle and determines the ventricular contraction rate in conditions where the atria undergo rapid depolarization.
115
Retinal artery occlusion
Retinal artery occlusion is a cause of acute, painless, mononuclear vision loss. It is usually caused by thromboembolic complications of atherosclerosis traveling from the internal carotid artery and through the ophthalmic artery.
116
IV infusion - Frank-Starling mechanism
Intravenous fluids increase the intravascular and left ventricular end-diastolic volumes. The increase in preload stretches the myocardium and increases the end-diastolic sarcomere length, leading to an increase in stroke volume and cardiac output by the Frank-Starling mechanism.
117
Myxomas
Myxomas are the most common primary cardiac neoplasm, and approximately 80% originate in the left atrium. Patients may have systemic embolization (eg, stroke) or symptomatic mitral valve obstruction that may be worse with certain body positions. Histopathologic examination reveals amorphous extracellular matrix with scattered stellate or globular myxoma cells with abundant mucopolysaccharide ground substance.
118
Germinomas
Germinomas are the most common pineal gland tumor and present with obstructive hydrocephalus and dorsal midbrain (Parinaud) syndrome. Germinomas in the suprasellar region cause endocrinopathies due to pituitary/hypothalamic dysfunction.
119
Severe chronic mitral regurgitation
Patients with severe mitral regurgitation develop left-sided volume overload with an S3 gallop due to the large volume of regurgitant flow reentering the ventricle during mid-diastole. The absence of an S3 gallop excludes severe chronic MR.
120
Mechanical complication 5-14 days s/p MI
Rupture of the left ventricular free wall is a catastrophic mechanical complication of anterior wall myocardial infarction (MI) that usually occurs within the first 5-14 days after MI. Rupture leads to hemopericardium and cardiac tamponade, causing profound hypotension and shock with rapid progression to pulseless electrical activity and death.
121
Unilateral renal artery stenosis
In unilateral renal artery stenosis, the affected kidney is protected from high blood pressure by the narrowing of its renal artery and may suffer ischemic damage. In contrast, the contralateral well-perfused kidney typically shows changes of hypertensive nephropathy (eg, hyaline or hyperplastic arteriosclerosis)
122
Chronic aortic regurgitation
Chronic aortic regurgitation (AR) causes a reduction in diastolic blood pressure and a compensatory increase in left ventricular stroke volume. These changes create a high-amplitude, rapid rise-rapid fall pulsation (ie, widened pulse pressure) and the other characteristic findings of AR (eg, head bobbing, “pistol-shot” femoral pulses)
123
Paradoxical embolism
Paradoxical embolism occurs when a thrombus from the venous system crosses into the arterial circulation via an abnormal connection between the right and left cardiac chambers (eg, patent foramen ovale, atrial septal defect, or ventricular septal defect). Atrial left-to-right shunts cause wide and fixed splitting of S2 and can facilitate paradoxical embolism due to periods of transient shunt reversal (eg, during straining or coughing).
124
Reversing muscarinic overstimulation in myasthenia gravis
The treatment of myasthenia gravis involves the use of a cholinesterase inhibitor, immunosuppressants, and possible thymectomy. Cholinesterase inhibitors may cause adverse effects related to muscarinic overstimulation, which can be ameliorated by the use of an antimuscarinic agent such as glycopyrrolate, hyoscyamine, or propantheline.
125
CAVD
Aortic stenosis most commonly results from age-related calcification aortic valve disease (CAVD). The early pathogenesis of CAVD closely mimics that of arterial atherosclerosis. In the later stages, fibroblasts differentiate into osteoblast-like cells and deposit bone matrix, leading to progressive valvular calcification and stenosis.
126
Dystrophic calcification
Dystrophic calcification occurs in damaged or necrotic tissue in the setting of normal calcium levels; metastatic calcification occurs in normal tissue in the setting of hypercalcemia.
127
Jugular foramen (Vernet) syndrome
Lesions of the jugular foramen can result in jugular foramen (Vernet) syndrome, which is characterized by the dysfunction of cranial nerves IX, X, and XI. Symptoms include dysphagia, hoarseness, loss of gag reflex on the ipsilateral side, and deviation of the uvula toward the normal side.
128
Peripheral edema
Peripheral edema results from the accumulation of fluid in the interstitial spaces. Factors that promote edema include elevated capillary hydrostatic pressure, decreased plasma oncotic pressure, sodium and water retention, and impaired lymphatic drainage. In chronic heart failure, increased lymphatic drainage initially offsets factors favoring edema, whereas acute changes (eg, venous thrombosis, heart failure decompensation) are more likely to produce edema.
129
Auscultation - aortic stenosis
The murmur of valvular aortic stenosis is typically an ejection or midsystolic murmur of crescendo-decrescendo configuration that starts after the first heart sounds and typically ends before the A2 component of the second heart sound, with maximum intensity over the right second interspace and radiation to the neck and carotid arteries. The intensity of the murmur is proportional to the magnitude of the left ventricle to aorta pressure gradient during systole. The most common cause of aortic stenosis in elderly patients (age >70) is degenerative calcification of the aortic valve leaflets.
130
Costosternal syndrome
Costosternal syndrome (costochondritis) usually occurs after repetitive activity and is characterized by pain that is reproducible with palpation and worsened with movement or changes in position.
131
HCM - LVOT obstruction
In patients with hypertrophic cardiomyopathy, dynamic left ventricular outflow tract obstruction is due to abnormal systolic anterior motion of the anterior
132
Incompetent venous valves
Chronically elevated venous pressure in the lower extremities can lead to incompetent venous valve and venous dilation (varicose veins). Venous congestion and tissue ischemia can result in venous stasis dermatitis.
133
Cavernous hemangioma
Cavernous hemangioma are vascular malformations composed of abnormally dilated capillaries separated by thin connective tissue septa. The lack of structure support gives them a tendency to bleed, and those that occur in the brain can present with neurological deficits and seizures.
134
Pressure tracing - aortic regurgitation
Aortic regurgitation causes a decrescendo diastolic murmur with maximal intensity occurring just after closure of the aortic valve, when the pressure gradient between the aorta and left ventricle is the highest. The pressure tracing for aortic regurgitation is characterized by loss of the aortic decorticate notch, steep diastolic decline in aortic pressure, and high-peaking systolic pressures.
135
Nonbacterial thrombotic endocarditis
Nonbacterial thrombotic endocarditis is a form of noninfectious endocarditis characterized by valvular deposition of sterile platelet-rich thrombi. It likely results from valvular damage due to inflammatory cytokines in the setting of underlying hypercoagulable state, and it is most commonly seen with advanced malignancy (especially mucinous adenocarcinoma) or systemic lupus erythematosus.
136
Pulsus paradoxus
Pulsus paradoxus is defined by a decrease in systolic blood pressure of >10 mmHg with inspiration. It is most commonly seen in patients with cardiac tamponade by can also occur in severe asthma, chronic obstructive pulmonary disease, and constrictive pericarditis. Asthma and chronic obstructive pulmonary disease (COPD) exacerbation are the most frequent causes of pulsus paradoxus in the absence of significant pericardial disease. Beta-adrenergic agonists control acute asthma and COPD exacerbations by causing bronchial smooth muscle relaxation via increased intracellular cAMP.
137
Tetralogy of Fallot - severity
In patients with Tetralogy of Fallot, the degree of right ventricular outflow obstruction is the major determinant of the degree of right-to-left intracardiac shunting and resulting cyanosis.
138
Carcinoid syndrome
Carcinoid syndrome typically presents with episodic flushing, secretory diarrhea, and wheezing. It can lead to pathognomonic plaque-like deposits of fibrous tissue on the right-sided endocardium, causing tricuspid regurgitation and right-sided heart failure. Elevated 24-hour urinary 5-hydroxyindoleacetic acid can confirm the diagnosis.
139
Constrictive pericarditis
In constrictive pericarditis, normal pericardium is replaced by dense, rigid pericardial tissue that restricts ventricular filling, leading to low cardiac output and progressive right-sided heart failure. Physical examination findings in such patients include elevated jugular venous pressure (JVP), pericardial knock, pulsus paradoxus, and a paradoxical rise in JVP with inspiration (Kussmaul sign). Calcification and thickening of the pericardium are common features of constrictive pericarditis on CT. Clinical findings include slowly progressive dyspnea, peripheral edema, and ascites.
140
Adult-type coarctation of the aorta
Patients with adult-type coarctation of the aorta commonly die of hypertension-associated complications, including left-ventricular failure, ruptured dissecting aortic aneurysm, and intracranial hemorrhage. These patients are at increased risk for ruptured intracranial aneurysms because of the increased incidence of congenital berry aneurysms of the Circle of Willis as well as aortic arch hypertension.
141
Vfib
Ventricular fibrillation is the most frequent mechanism of sudden cardiac death in the first 48 hours after acute myocardial infarction and is related to electrical instability in the ischemic myocardium.
142
Acute pericarditis
Acute-onset, sharp and pleuritic chest pain that decreases with leaning forward is characteristic of acute pericarditis. Fibrinous/serofibrinous pericarditis is the most common form of pericarditis and a pericardial friction rub is the most specific physical finding. Viral pericarditis is often preceded by an upper respiratory infection.
143
Coronary plaque rupture
The likelihood of plaque rupture is related to plaque stability rather than plaque size or the degree of luminal narrowing. Plaque stability largely depends on the mechanical strength of the fibrous cap. Inflammatory macrophages in the intima may reduce plaque stability by secreting metalloproteinases, which degrade extracellular matrix proteins (eg, collagen).
144
Varicose veins
Varicose veins are dilated, tortuous veins most commonly found in the superficial veins of the leg. They are caused by chronically increased intraluminal pressure and/or loss of tensile strength in the vessel wall, leading to incompetence of the venous valves. Common complications include edema, stasis dermatitis, skin ulceration, poor wound healing, and infections.
145
Osler-Weber-Rendu syndrome
Osler-Weber-Rendu syndrome (hereditary hemorrhagic telangiectasia) is an autosomal dominant condition marked by the presence of telangiectasias in the skin as well as the mucous membranes of the lips, oronasopharynx, respiratory tract, gastrointestinal tract, and urinary tract. Rupture of these telangiectasias may cause epistaxis, gastrointestinal bleeding, or hematuria.
146
Intimal tear risk factor
Hypertension is the single most important risk factor for the development of intimal tears leading to aortic dissection. Hypertension, smoking, diabetes mellitus, and hypercholesterolemia are all major risk factors for atherosclerosis, which predisposes more to aortic aneurysm formation than aortic dissection.
147
PDA complicated by Eisenmenger syndrome
Differential clubbing and cyanosis without blood pressure or pulse discrepancy are pathognomonic for a large patent ductus arteriosus complicated by Eisenmenger syndrome (reversal of shunt flow from left-to-right to right-to-left). Severe coarctation of the aorta can cause lower extremity cyanosis. Right-to-left shunting in patients with large septal defects and tetralogy of Fallot results in whole-body cyanosis.
148
Coagulative necrosis
Lethal tissue ischemia causes coagulative necrosis in most tissues, including the myocardium. The exception is ischemic cell death in the central nervous system, which causes liquefactive necrosis.
149
Diastolic HF
Diastolic heart failure is caused by decreased ventricular compliance and is characterized by normal left ventricular (LV) ejection fraction, normal LV end-diastolic volume, and elevated LV filling pressures.
150
WPW
Wolf-Parkinson-White (WPW) pattern is characterized by a shortened PR interval, widening of the QRS complex, and slurred initial upstroke of the QRS complex (delta wave). It is caused by an accessory pathway that bypasses the atrioventricular node, causing preexcitation of the ventricles. Patients with WPW pattern can develop symptomatic arrhythmia (eg, atrioventricular reentrant tachycardia) due to reentry of electrical impulses through the accessory conduction pathway.
151
ADPKD - nervous system
Intracranial berry aneurysms of the circle of Willis are often seen in patients with ADPKD; when ruptured, they cause subarachnoid hemorrhage that presents with sudden onset of “thunderclap headache”.
152
Auscultation - aortic regurgitation
Aortic regurgitation (AR) causes a high pitched, blowing, diastolic murmur with a decrescendo intensity pattern. The murmur is best heart at the right upper sternal border, whereas the murmur of AR due to valvular pathology is best heard at the left third intercostal space.
153
S4 heart sound
A low-frequency, late diastolic sound on cardiac auscultation that immediately precedes the first heart sound (S1) is most often a fourth heart sound (S4). An abnormal S4 can be heard in patients with reduced ventricular compliance (eg, hypertensive heart disease, aortic stenosis, hypertrophic cardiomyopathy) due to a sudden rise in end-diastolic pressure with atrial contraction.
154
CN IX lesion
Lesions of the glossopharyngeal nerve result in loss of the gag reflex (afferent limb); loss of the sensation in the upper pharynx, posterior tongue, tonsils, and middle ear cavity; and loss of taste sensation on the posterior third of the tongue.
155
ACE inhibitors/ARBs - CKD
Angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) reduce the risk of chronic kidney disease in patients with hypertension and diabetes. ACE inhibitors raise levels of bradykinin and can cause a nonproductive cough, an effect not seen with ARBs.
156
Atherosclerosis - proffered vessels
Atherosclerosis is a pathophysiologic process involving endothelial cell dysfunction and it develops most rapidly in areas with bends and branch points that encourage turbulent blood flow. The lower abdominal aorta and coronary arteries are the vascular beds most susceptible to atherosclerosis; they tend to develop atherosclerosis earliest in life and have the highest overall atherosclerotic burden.
157
Pericarditis s/p recent MI
In contrast to angina, the chest pain of pericarditis is sharp and pleuritic and may be exacerbated by swallowing or coughing. Peri-infarction pericarditis (PIP) occurs between 2 and 4 days following a transmural myocardial infarction (MI). PIP is an inflammatory reaction to cardiac muscle necrosis that occurs in the adjacent pericardium.
158
Prolonged PT w normal aPTT
A normal bleeding time indicates adequate platelet hemostatic function. A normal activated partial thromboplastin time (aPTT) indicates an intact intrinsic coagulation system. Prolonged prothrombin time in the setting of normal aPTT indicates a defect in the extrinsic coagulation system at a step that is not shared with the intrinsic system
