First Pass Miss Flashcards
What is the formula for wall stress? What increases / decreases it?
Wall stress = (Pressure x Radius) / 2(wall thickness)
-> force with cardiomyocytes must push against
Increased by greater radius from center to wall of ventricle, and systolic pressure (afterload)
Stress is normalized via increasing wall thickness
Why is afterload approximated by mean arterial pressure?
Afterload can basically be thought of as the force per unit area the heart must push against
However, we assume that ventricular radius and wall thickness are pretty much constant, so pressure (in the numerator of wall stress equation) is a pretty good proxy.
Pressure = Force per area
Radius = length (i.e. cm)
Wall thickness = length (i.e. cm)
(F/A * cm) / cm = F/A, Laplace’s law
How does wall stress change during ejection?
It decreases because
- The size of the LV cavity decreases -> Radius decreases
- LV wall thickness increases -> more sarcomeres pushed together
Give a few conditions causing concentric hypertrophy?
Uncontrolled HTN
Aortic valve stenosis
Pulmonic valve stenosis (thickening of RV)
-> laying down of fibers in parallel to reduce wall stress by increasing thickness and reducing radius of ventricles
What does eccentric hypertrophy happen in response to, and what is its pathogenesis?
In response to chronically increased preload
- > Lay down more sarcomeres in series to accommodate increased volume
- > Increased volume increases wall stress (radius is larger)
- > Lay down sarcomeres in parallel to increase wall thickness and decrease cavity size
Why is LV hypertrophy bad?
- Volume of myocytes increases disproportionately to capillary growth -> decreased coronary reserve in situations of high demand (i.e. tachycardia)
- Sarcomeres increase more than mitochondria -> inefficient energy use
- Decreased contraction efficiency in myosin ATPase
- Increased collagen deposition -> increased LV stiffness
What is the Fick equation and how is it used to measure cardiac output?
Cardiac output = VO2 (measured via inspiration / expiration, in mL/min) / AV oxygen difference (mL O2 / liter of blood)
Measure the patients arterial and venous O2 concentrations for the AV oxygen difference.
How is vascular resistance measured? Units?
Mean pressure difference across a vascular bed / mean blood flow (Delta P / CO = TPR)
Mean blood flow is measured in volume / time (cm^3/sec)
Thus, units are (Dynes/cm^2) / (cm^3 / sec) = dynesseccm^-5
Dyne is a force per unit area
What does pulmonary capillary wedge pressure (PCWP) approximate?
Left atrial pressure (diastolic pressure from a balloon catheter inserted into the pulmonary artery) -> LVEDP -> implies LVEDV -> preload
How is vascular resistance measured? Units?
Mean pressure difference across a vascular bed / mean blood flow (Delta P / CO = TPR)
Mean blood flow is measured in volume / time (cm^3/sec)
Thus, units are (Dynes/cm^2) / (cm^3 / sec) = dynesseccm^-5
Dyne is a force per unit area
What does pulmonary capillary wedge pressure (PCWP) approximate?
Left atrial pressure (diastolic pressure from a balloon catheter inserted into the pulmonary artery) -> LVEDP -> preload
How is the systemic vascular resistance calculated and what is the normal range?
SVR = (MAP - Mean RAP) / CO
RAP = right atrial pressure
Normal = 900-1300 dynesseccm^-5
What is the definition of hypertensive crisis?
SBP > 180
or
DBP > 110
Urgency = without end-organ damage Emergency = with evidence of end-organ damage
How is the pulmonary vascular resistance calculated and what is the normal range?
PVR = (Mean PAP - Mean LAP) / CO
LAP = Left atrial pressure = PCWP
Normal = 40 to 90 dynesseccm^-5
Who is most likely to get fibromuscular dysplasia and renal artery stenosis?
Fibromuscular dysplasia -> especially young women, developmental defective in large and medium muscular arteries, especially affecting renal artery
Renal artery stenosis -> especially older men, due to atherosclerosis of renal arteries
Other than adrenal disorders, give four endocrine disorders or conditions which can cause hypertension?
- Acromegaly - GH excess
- Hypothyroidism -> Increases sodium, also increases lipid levels for hardening of arteries
- Hyperparathyroidism -> increases renin / kidney dysfunction
- Exogenous hormones -> steroids / oral contraceptives
What are the best antihypertensives to use post-MI and in heart failure / CAD?
Beta blocker and ACE inhibitor
Use diuretics in heart failure and CAD
What is the definition of resistant HTN? Causes?
Persistently elevated BP despite 3+ medications
Causes:
Noncompliance or medications at not max dose, use of other drugs which elevate BP, volume overload, or undiagnosed OSA
When are ACE inhibitors contraindicated?
- C1 esterase inhibitor deficiency (C1 esterase inhibitor also cleaves kallikrein, responsible for converting HMW kininogen to bradykinin. Only other enzyme which breaks down bradykinin is ACE)
- Bilateral renal artery stenosis -> angiotensin II is the only thing maintaining GFR by constricting efferent arteriole
- Pregnancy
What areas of the brain are most susceptible to microaneurysm rupture in systemic hypertension?
Putamen (BG), thalamus, and pons
Rupture.PPT
What can be seen pathologically in hyerplastic arteriolosclerosis? Grossly in kidney?
Concentric proliferation of myofibroblastic cells into intima - “onion-skin” appearance
Accompanied by fibrinoid necrosis and petechial hemorrhages.
Grossly: Kidney will have a flea-bitten appearance due to hemorrhages on cortical surface
How does benign nephrosclerosis appear microscopically in larger arteries? What is benign nephrosclerosis?
Larger arteries include interlobular and arcuate
Fibroelastic hyperplasia -> myofibroblast hyperplasia, reduplication of elastic lamina, medial smooth muscle hypertrophy, and luminal narrowing (large arteries respond somewhat like hyperplastic arteriolosclerosis)
Benign nephrosclerosis occurs in longstanding essential hypertension and diabetes mellitus
How does benign nephrosclerosis appear microscopically in small arteries / arterioles and renal parenchyma?
Small arteries / arterioles - hyaline arteriolosclerosis
Renal parenchyma - ischemic changes - interstitial / glomerular fibrosis and accompanying tubular atrophy
What are the microscopic features of malignant nephrosclerosis? (Grossly = flea-bitten appearance)
Small arteries / arterioles -> hyperplastic arteriolosclerosis with fibrinoid necrosis
Renal parenchyma -> infarction and/or ischemic atrophy (if you had prior benign hypertension) -> infarction due to rapid death of arterioles
As vascular walls weaken, forming microaneurysms and hemorrhages in the retina, how do you know if a hemorrhage is superficial vs deep?
Flame-shaped hemorrhages - more superficial, as the nerve fiber layer runs perpendicular to the rods and cones in the back of the retina, and the hemorrhage follows these.
(we are seeing their long axis).
Dot hemorrhages - more deep, as the hemorrhage runs between the plexiform layers which are parallel to the rods / cods in the retina.(we are seeing their short axis)
How serious are hard exudates in the retina and what are they? How about cotton wool spots?
Very serious -> represent a severe, acute increase in blood pressure which has resulted in the breakdown of the blood-retinal barrier
-> leakage of lipid and protein into the retina, causing small, yellow, oval lesions deep in the retina
Cotton wool spots are less serious microinfarcts of the nerve fiber layer leading to damaged “cytoid bodies”
What are the most severe findings of malignant hypertension in the retina? Will vision changes occur?
Optic disc swelling (papilledema), associated with macular star
-> macular star due to how nerve fibers are arranged around the fovea, and complete loss of outer blood-retinal barrier causing many hard exudates to deposit around.
Papilledema due to very high ICP.
-> this is where we will see blurred vision typically
What retinal changes of hyaline arteriolosclerosis can be seen very early on?
- Narrowing / tortuosity of retinal arteries
- Copper-wire / silver-wire appearance -> due to thickened wall and narrowed blood column, altering light reflex
- AV nicking
What are the four biochemical labs which, when elevated, are associated with atherosclerosis?
- C-reactive protein (inflammation)
- Homocysteine
- Lipoprotein (a)
- Plasminogen activator inhibitor (PAI) -> released by endothelial cells in prothrombotic states
What is an atheroma? How does it appear grossly?
Uncomplicated fibrofatty plaque (within the intima)
Grossly - raised, yellow-white lesion protruding into blood vessel
How do macrophages amplify the atherosclerosis response?
Increase IL-1/TNF levels to increase leukocyte adhesion, give chemotactic cytokines, and oxidize LDL via oxygen-free radicals. They also secrete growth factors.
What is the first stage of the increasing size of the atheroma / what is this called? When can the vessel lumen start getting smaller?
Positive remodeling -> vessel gets larger due to plaque formation, but the vessel is not stenosed at all
-> lumen shrinks once the plaque occupies greater than 40% of the circular intima
How do preload and afterload increases affect myocardial oxygen demand?
By increasing wall tension, they increase myocardial oxygen demand
What is a good, rapid measure of myocardial oxygen demand?
Rate Pressure Product (RPP)
RPP = HR * SBP
SBP = systolic blood pressure
How is unstable angina defined?
New onset angina of at least class III severity (within 2 months of initial presentation), increase in frequency or severity, or angina at REST.
What is the first stage of the increasing size of the atheroma / what is this called? When can the vessel lumen start getting smaller?
Positive remodeling -> vessel gets larger due to plaque formation, but the vessel is not stenosed at all
-> lumen shrinks once the plaque occupies greater than 40% of the circular intima
How do preload and afterload increases affect myocardial oxygen demand?
By increasing wall tension, they increase myocardial oxygen demand
What areas does the right coronary artery supply (other than the right / left dominant areas)?
Anterior right ventricle
-always, via the right marginal artery
Right dominant hearts usually have the posterior descending coronary artery, sometimes it comes off of left circumflex
What areas are supplied by either the left heart or the right heart depending on dominance?
Posterior descending coronary artery
- > supplies posterior 1/3 of IV septum, posterior and inferior walls of left ventricle
- > AV node and proximal HIS bundle
- > posteromedial papillary muscle
What symptoms are most compatible with infarction due to ACS?
Prolonged chest discomfort >30 minutes, with radiation to left arm or neck.
- > precipitated by exertion and relieved by rest / nitroglycerin
- > nausea, vomiting, diaphoresis, palpitations are common
Women may have SHARP pain, fatigue, or weakness
Elderly may have AMS
What is the general treatment plan for chronic stable angina?
Beta blocker. Use non-DHP calcium channel blocker if not working or contraindicated
Use sublingual nitroglycerin for acute events
What areas does the right coronary artery supply (other than the right / left dominant areas?
- Anterior right ventricle
- Posterior 1/3 of interventricular sptum
- Posterior wall of LV
- Posteromedial papillary muscle of LV - near septum
(anterolateral supplied by LAD / circumflex dual supply)
What areas are supplied by either the left heart or the right heart depending on dominance?
Inferior LV
Proximal HIS bundle
AV node
Posterior left bundle
What symptoms are most compatible with infarction due to ACS?
Prolonged chest discomfort >30 minutes, with radiation to left arm or neck.
- > precipitated by exertion and relieved by rest / nitroglycerin
- > nausea, vomiting, diaphoresis, palpitations are common
Should PCI be done in NSTEMI or unstable angina?
Yes, this is okay -> just no thrombolytic therapy unless STEMI
When myocardial ischemia occurs, how quick is function lost, and when does irreversible injury occur? When is infarct size determined?
Functional loss: within 1-2 minutes after myocardium has to switch to anaerobic glycolysis and lactic acid accumulates
-> organelle and cytosolic swelling occurs with loss of function and irritability
Irreversible injury: Begins at 30 minutes, infarct size is determined by around 6 hours
What is the general treatment plan for Prinzmetal angina?
Use DHP calcium channel blockers (i.e. amlodipine, relax the coronary arteries), with sublingual nitroglycerin for acute events.
In what ACS’s should thrombolytic therapy be used?
Only in STEMI, and only if PCI capability is unavailable for greater than 90 minutes.
Must be done within 12 hours of symptoms onset.
Should PCI be done in NSTEMI or unstable angina?
Yes, this is okay -> just no thrombolytic therapy unless STEMI
When myocardial ischemia occurs, how quick is function lost, and when does irreversible injury occur? When is infarct size determined?
Functional loss: within 1-2 minutes after myocardium has to switch to anaerobic glycolysis and lactic acid accumulates
-> organelle and cytosolic swelling occurs with loss of function and irritability
Irreversible injury: Begins at 30 minutes, infarct size is determined by around 6 hours
What are some reperfusion-induced injuries?
- Additional cell death
- Microvascular injury w/ endothelial swelling
- Cardiac arrhythmias
What is a likely complication 2-3 days after a transmural infarct? Why is it specific to this type of infarct?
Fibrinous percarditis, due to inflammatory response entering the pericardial sac
Subendocardial infarcts will not allow access of inflammatory cells to the pericardial sac
Other than rupture, what are a few other reasons for papillary muscle dysfunction in MI? What’s the result of all of these?
Mitral valve regurgitation is the outcome
- Acute ischemia -> can’t contract
- Chronic fibrosis and shortening -> due to healing with fibrosis post-MI
- LV dilatation -> weak, healing wall must dilate.
In 2/3 the valve leaflets won’t be able to reach to close.
What is a left ventricular aneurysm? When after an MI does this occur? What is the most likely complication?
Occurs very late, after an anterior, transmural myocardial infarct. The wall repairs via fibrous scarring and stretches outward.
Likely complication -> mural thrombosis (Due to exposed collagen) but NOT rupture because it is dense collagen (vs false aneurysm)
-> rupture causing hemopericardium or false aneurysm is most likely 4-5 days post MI
How should a patient coming in with ACS be treated with aspirin?
An initial loading dose of 2-4 baby aspirins (81mg each) should be given, via chewing an uncoated pill
-> rapid antithrombic effect due to almost complete inhibition of TXA2
-> contraindicated in In patients >60 years of age with peptic ulcer bleeding
What are some reperfusion-induced injuries?
- Additional cell death
- Microvascular injury w/ endothelial swelling
- Cardiac arrhythmias
What are the contraindications for nitroglycerin? There are four, three were covered in sketchy, the other is intuitive, but be specific about it.
- Hypotension (SBP < 90 mmHg) -> avoid when this may be possible, as it will worsen this
- Right ventricular infarction -> reduction in preload may cause cardiogenic shock (think of sketchy no right turn sign)
- Aortic stenosis -> Need the preload into the left heart to maintain blood flow -> think of the curled smokestack in sketchy
- Phosphodiesterase inhibitors (PDE5) taken within the last 24 hours -> i.e. sildenafil -> fill = coal truck in sketchy
What are the beta blockers of choice for ACS? How quickly should they be started? What types should be used?
Cardioselective agents: Metoprolol and Atenolol
Should be started within 24 hours
Early: Use short-acting and low dose, titrating upwards for tighter control
Discharge: Give long-acting beta blockers
-> give IV for hypertensive emergencies or Afib with RVR
What are the anticoagulant therapies of choice for early hospital care in ACS? When are these used?
- Enoxaparin (think of the pair of foxes held by fido for fondaparinux or enoxaparin)
- > inhibit the factor Xa fox by holding it in close association with ATIII - Unfractionated heparin can also hold onto thrombin
Only in thrombus related NSTEMI -> not indicated for STEMI
What is the typical secondary prevention therapy for ACS?
- Dual therapy for 1 year: aspirin / P2Y12
- Beta blockers
- Ace inhibitor / ARB - if indicated (HTN, Diabetes, or HFrEF)
- Statin
- Standard risk factor management
Where are the precordial / chest leads placed?
V1: Right 4th intercostal space
V2: Left 4th intercostal space
V3: Between V2 and V4
V4: Midclavicular line, 5th intercostal space
V5: Between V4 and V6, anterior axillary line
V6: Midaxillary line, 5th intercostal space
How does ticagrelor differ from prasugrel? How is it similar?
Differs - binds REVERSIBLY -> clopidogrel and prasugrel are irreversible
Similar - rapid onset, more intense inhibition, same contraindications:
Prior TIA or stroke
>75 years of age (elderly)
When are GP IIb/IIIa inhibitors used? Which one is recommended?
Used for patients undergoing early cardiac catheterization to prevent thrombus formation
Eptifibatide - think TIED score in sketchy
Preferred over abciximab or TIrofiban - “tie”
What are the common causes of prolonged QT?
Drugs (macrolides, Class IA and III antiarrhythmics, antipsychotics, TCAs, ondansetron)
Hypomagnesia, hypokalemia, hypocalcemia
Congenital long QT syndrome
Increased ICP
What is a normal P wave duration, and what leads should always be up or down?
80-200 msec
Upright in leads I and II
Inverted in aVR
What is the definition of Mobitz I, second degree AV block?
Also called Wenckebach
-> Mobitz 1 cuz its my #1 favorite arrhythmia
Gradually lengthening PR intervals, until QRS is dropped. Longest PR interval just before dropped beat, shortest after dropping a beat.
What is the ECG definition for left atrial enlargement?
This is the criteria of 1s.
- P wave in V1 is -1.0 mm in depth for at least 1 small box
- P wave is notched (humped) in lead I with a duration of >120 msec (3 small boxes).
What is the ECG definition for right atrial enlargement?
P wave is tall and peaked, with a height of 2.5 mm or more in leads II, II, and aVF (all inferior leads).
-> P wave is >2.5 small boxes in inferior leads
How is atrial flutter diagnosed via ECG?
- Narrow QRS tachycardia - usually around 150 bpm. May be slower if on medications to slow AV node conduction
- Regular atrial activity at about 300 bpm
- Flutter waves “saw tooth” seen in leads II, III, and aVF
(inferior leads)
What is a normal P wave duration, and what leads should always be up or down?
80-200 msec
Upright in leads I and II
Inverted in aVR
What is the primary toxicity of concern with class Ib antiarrhythmics?
Brain hat on the trucker -> neurologic issues
Lowers the seizure threshold, tremor, slurred speech, convulsions
Includes Mexiletine and Lidocaine
What is the primary interval on ECG which class IC drugs will prolongate? What is their use?
Primarily the QRS interval -> strongly bind Na+ channels, leaving K+ channels untouched (curtain untouched) -> no QT effect really
Use: Atrial fibrillation rhythm control - guy sitting in bed changing channel on TV (2nd line to amiodarone)’
-> Propafenone and Flecainide
What is the ECG definition for right atrial enlargement?
P wave is tall and peaked, with a height of 2.5 mm or more in leads II, II, and aVF (all inferior leads).
-> P wave is >2.5 small boxes in inferior leads
How is atrial flutter diagnosed via ECG?
- Narrow QRS tachycardia - usually around 150 bpm. May be slower if on medications to slow AV node conduction
- Regular atrial activity at about 300 bpm
- Flutter waves “saw tooth” seen in leads II, III, and aVF
(inferior leads)
What are the ECG characteristics of multifocal atrial tachycardia?
- At least 3 different P wave forms in the same lead, with no dominant atrial pacemaker
- Atrial rate > 100 bmp.
- PR and RR intervals will vary, but P waves are more obvious than in atrial fibrillation and are ALL transmitted to the ventricles
-> seen in COPD / asthma
What is the primary toxicity of concern with class Ib antiarrhythmics?
Brain hat on the trucker -> neurologic issues
Lowers the seizure threshold, tremor, slurred speech, convulsions
Includes Mexiletine and Lidocaine
What is the primary interval on ECG which class IC drugs will prolongate? What is their use?
Primarily the QRS interval -> strongly bind Na+ channels, leaving K+ channels untouched (curtain untouched) -> no QT effect really
Use: Atrial fibrillation rhythm control - guy sitting in bed changing channel on TV (2nd line to amiodarone)’
-> Propafenone and Flecainide
What drugs can be used for pharmacological cardioversion?
Class 1C = Flecainide, propafenone
Class 3 = Dofetilide, Ibutilide, amiodarone
What is the first line treatment for Rate control in Afib with and without heart failure?
Afib w/ heart failure = Digoxin, add beta-blocker if needed
Afib w/o heart failure = non-DHP CCBs, add digoxin if needed
Can consider Beta blockers instead of CCBs for Afib w/o HF, but not calcium channel blockers in heart failure (think of guy holding balloon outside sketchy)
What is the primary use of amiodarone, and what are its drug interactions / half life?
Use - Most effective anti-arrhythmic for maintaining sinus rhythm in AF, as well as termination of ventricular tachycardias
- > Inhibits many CYP450s -> think of the CYP450 truck holding cow, especially warfarin problem
- > Half life ~60 days = need a huge loading dose.
Why might Dronedarone be preferred to amiodarone, and when should it be avoided?
Has a shorter halflife due to lack of iodine moieties, good for non-permanent Afib (paroxysmal <7 days or persistent >7 days but cardiovertable)
Avoid: HFrEF, and PERMANENT Afib (dumb)