Week 1 Flashcards
A patient presents to the trauma bay with gunshot wounds in his chest. He appears confused, has jugular venous distention, and his blood pressure is 80/50. During inspiration his systolic blood pressure drops to 68. What is the most likely cause of this patient’s symptoms? A) blood loss from trauma B) inflammation of the epicardium C) acute hemorrhage into the pericardial cavity D) collection of fluid outside the fibrous pericardium
The correct answer is C. The patient is presenting with acute cardiac tamponade, most likely from acute hemorrhage into the pericardium resulting from penetrating chest trauma. The accumulation of fluid in the pericardial cavity increases the pressure because of the low compliance of the fibrous pericardium, and compresses the heart. Classic clinical features of cardiac tamponade include jugular venous distention, hypotension with pulsus paradoxus (exaggerated drop in systolic blood pressure upon inspiration), a “quiet”heart, and sinus tachycardia. Acute tamponade can lead to symptoms of confusion and agitation due to hypotension. A is incorrect. Blood loss is most likely also a cause of the patient’s hypotension, but does not explain his other symptoms B is incorrect. Acute pericarditis can lead to cardiac tamponade, but the patient’s history makes this less likely. There are infectious causes of acute pericarditis (viral, tuberculosis, and pyogenic bacteria) and noninfectious causes (postmyocardial infarction, neoplastic disease, etc.) D is incorrect. Collection of fluid outside the fibrous pericardium which is part of the parietal pericardium will not lead to cardiac tamponade. Cardiac tamponade is caused by accumulation of fluid within the pericardial space between the fibrous pericardium and visceral pericardium (epicardium) SM 106a: Heart and Mediastinum Anatomy Learning objective: Describe the relationship between parietal and visceral pericardium and how it differs from pleura. Define epicardium and fibrous pericardium; and describe the anatomical basis of cardiac tamponade. (MKS1a)
Which of the following is correct about blood flow? A) As the radius of the blood vessel is doubled, the resistance is halved B) The total resistance of resistances in parallel is more than any individual resistance C) A heart murmur is an example of laminar flow while Korotkoff sounds are an example of turbulent flow D) Blood flow is equal to the pressure difference divided by resistance.
The correct answer is D. This is Ohm’s Law, where Q= ΔP/R where Q is the blood flow, ΔP is the pressure difference between two points in circulation, and R is the resistance. A is incorrect. By the Poiseuille Equation, when the radius is doubled, the resistance becomes one-sixteenth the original amount of resistance. B is incorrect. The total resistance of resistances in parallel is less than any individual resistance C is incorrect. Both heart murmurs and Korotkoff sounds are examples of turbulent blood flow. SM 107a. Fundamental Hemodynamics. Learning objectives: Apply Ohm’s law (Q = delta P / R) to basic hemodynamics problems. Apply Poiseuille’s law to understand resistance to blood flow. Contrast serial resistance with parallel resistance. Correlate the concepts of Reynolds number and Korotkoff sounds.
A 50 year old patient presents to your clinic with a stroke due to paradoxical emboli. What is the most likely cause of the stroke? A) failure of the septum primum and septum secundum to fuse B) unequal division of the truncus arteriosus by the spiral septum C) defect in the membranous ventricular septum D) failure to develop the tricuspid valve
The correct answer is A. Paradoxical emboli, where venous thromboemboli enter the arterial circulation, is most likely due to a patent foramen ovale. The foramen ovale usually closes after birth because of increased left atrial pressure. The septum primum and septum secundum will fuse after birth. B is incorrect. Unequal division of the truncus arteriosus by the spiral septum can lead to conotruncal abnormalities such as Tetralogy of Fallot. Clinically, the infant will present with cyanosis because of too little blood flow to the lungs. C is incorrect. Defects in the membranous ventricular septum usually leads to ventricular septal defects. This can lead to congestive heart failure due to fluid overload in the left side of the heart. The membranous septum forms from the fusion of the endocardial cushions, the aorticopulmonary septum, and the muscular interventricular septum. D is incorrect. Failure to develop the tricuspid valve can lead to tricuspid atresia, with clinical symptoms of shortness of breath and cyanosis. SM 110. Cardiovascular embryology. Learning objective: Describe how the embryonic heart tube gets partitioned into the four chambers and the kinds of congenital heart defects that might arise from abnormal development.
A patient presents to the clinic with a severe crescendo-decrescendo systolic heart murmur and shortness of breath upon exertion. What would be the best cardiac imaging modality to order first? A) Cardiac magnetic resonance B) Echocardiography C) Cardiac CT D) Electrocardiogram
The correct answer is B, Echocardiography. The patient is presenting with a murmur characteristic for aortic stenosis. Echocardiography would be the best noninvasive cardiac imaging modality to evaluate the severity of aortic stenosis (aortic valve area and transvalvular pressure gradient) and left ventricular wall thickness. A is incorrect. Cardiac magnetic resonance is useful for assessing cardiac anatomy, left and right ventricular size and function, and myocardial scarring and viability. It is not indicated for evaluation of aortic stenosis. C is incorrect. Cardiac CT and cardiac catheterization may be necessary for visualization of the coronary arteries, since coronary artery bypass surgery may be needed to be done concurrently. However, this is not the best imaging modality for evaluation of aortic stenosis. D is incorrect. An electrocardiogram is an useful test to evaluate for left ventricular hypertrophy, but is not a noninvasive cardiac imaging modality. SM 109a. Cardiac imaging. Learning objectives: Describe how imaging methods are used to understand normal anatomy and identify anatomic abnormalities (MKS1d). List strengths and weaknesses of cardiac ultrasound, computed tomography and magnetic resonance imaging of the heart. (MKS1d)
How does digoxin improve cardiac contractility? A) increasing the heart rate through the ascending staircase effect B) phosphorylation of troponin I C) inhibits the membrane Na+/K+ ATPase D) phosphorylation of phospholamban
The correct answer is C. Digoxin blocks the Na+/K+ ATPase, leading to an increase in intracellular Na+. This decreases the activity of the Na+/Ca2+ exchanger, so intracellular calcium levels increase, increasing the contractility. A is in correct. Increasing the heart rate causes increased intracellular calcium to accumulate in the sarcoplasmic reticulum, which increases contractility. However, digoxin is vagomimetic and so usually slows the heart rate, not increase it. B and D are incorrect. Phosphorylation of troponin I and phospholamban are two mechanisms for improving contractility after activation of Beta1 receptors with beta agonists such as epinephrine. Phospholamban phosphorylation leads to dissociation of phospholamban from SERCA, so Ca2+ reuptake increases. Phosphorylation of troponin I increase force generation by myofilaments. SM 112a. Cardiac Muscle Contraction. Learning objective: Map the contractile cycle.
Which of the following explains why cardiac action potentials have a plateau in Phase 2 of the potential? A) voltage-gated Na+ channels opened B) voltage-gated Ca2+channels open and the Ca2+ influx balances K+ efflux C) voltage-gated K+ channels open D) opening of slow K+ channels and closure of voltage-gated Ca2+ channels
The correct answer is B. In phase 2, voltage gated Ca2+ channels open leading to an influx of Ca2+ from sarcoplasmic reticulum in Phase 2. A is in correct. Voltage-gated Na+ channels open in phase 0, leading to a rapid depolarization. C is incorrect. The voltage gated K+ channels open in phase 1, phase 3, and phase 4. D is incorrect. The opening of slow K+ channels and closure of voltage-gated Ca2+ channels leads to rapid repolarization in Phase 3 of the cardiac action potential. SM 113. Normal Cardiac Electrical activity. Learning objective: Describe genesis of cardiac action potential (MKS-1a)
During which part of the jugular venous pulse does the right ventricle contract? A) a wave B) x descent C) y descent D) v wave E) c wave
The correct answer is E. During the c wave, the right ventricle contracts and the closed tricuspid valve bulges into the right atrium. A is incorrect. During the a wave, there is atrial contraction. B is incorrect. During the x descent, there is atrial relaxation and the closed tricuspid valve moves downward C is incorrect. During the y descent, the right atrium is emptying into the right ventricle. D is incorrect. The v wave is caused by an increase in right atrial pressure as the right atrium fills against a closed tricuspid valve. SM 111a. Pressure volume loops and the cardiac cycle. Draw the contour of the jugular venous pulsation, marking the a wave, c wave, x descent, v wave, and y descent
How is the action potential of the sinus node and AV node different from the ventricular action potential? A) In Phase 4 voltage gated K+ channels open. B) There is no Phase 1 or 2. C) The upstroke in Phase 0 is caused by the opening of voltage gated Na channels in the SA and AV node D) In Phase 3 Ca2+ channels are inactivated and K+ channels are activated leading to K+ efflux
The correct answer is B. Phase 1 and 2 are absent in the SA and AV nodes A is incorrect. In both potentials voltage gated K+ channels open in Phase 4. In the SA and AV nodes phase 4 activates the funny current If, leading to the opening of K+ channels and Na+ channels. C is incorrect. The upstroke in Phase 0 is caused by the opening of voltage gated Ca channels D is incorrect. In Phase 3 Ca2+ channels are inactivated and K+ channels are activated leading to K+ efflux for both action potentials. SM 114a. Impulse Propagation and Pace-making. Explain the differences in action potential characteristics in different parts of the heart (sinus node and AV node compared with the atrial and ventricular myocardium (MKS1a)
After a patient begins running, there are shifts in the cardiac output and vascular function curves in the Guyton diagram. What is a correct reason for this shift? A) Venoconstriction shifts the vascular function curve rightward and upward B) The cardiac output curve decreases because of improved contractility and an increased heart rate C) The peripheral vascular resistance increases with improved contractility and an increased heart rate D) The plasma volume increases shifting the vascular function curve rightward and upward.
The correct answer is A. Venoconstriction increases the stressed volume of the circulation, shifting the vascular function curve rightward and upward (to the curve with point C on the diagram above. The curve with point D on the diagram above also includes the effects on the vascular function curve from the drop in SVR). B is incorrect. The cardiac output curve increases during acute exercise because of improved contractility and an increased heart rate. C is incorrect. The peripheral vascular resistance decreases because vasodilation occurs to increase blood flow to the muscles D is incorrect. Increased plasma volume does shift the vascular function curve rightward and upward, but this does not happen in acute exercise but in other cases such as heart failure. SM 115a. Cardiac output and venous return. Learning objectives: Describe how exercise modifies the Guyton diagram. Describe how heart failure modifies the Guyton diagram.
The structure indicated by arrow 1 in the figure below (insert bottom right indicates level of the section) is which of the following vessels?
a. Brachiocephalic artery (trunk)
b. Left subclavian artery
c. Left common carotid artery
d. Right brachiocephalic vein
e. Superior vena cava
a. Brachiocephalic artery (trunk) – arrow 2
b. Left subclavian artery – arrow 3 ( posterior and to the left of the left common carotid artery)
c. Left common carotid artery – in between arrow 2 and 3 (posterior to brachiocephalic artery)
d. Right brachiocephalic vein – correct answer, arrow 1
e. Superior vena cava – not seen at this level, notice that the right and left brachiocephalic veins (elongated structure immediately posterior to manubrium) are still separate
Card from 2018-2019 Lectures
A 24-year old healthy medical student enrolls in a study assessing healthy parameters of human circulatory physiology. During the study, the blood oxygen content of the aorta and several other vessels is measured at rest. The greatest difference in these measurements will be between the aorta and which of the following blood vessels?
a. Internal jugular vein
b. Portal vein
c. Coronary sinus
d. Pulmonary artery
e. Pulmonary vein
c. Coronary sinus
Arterial blood supply to the cardiac muscle is provided by the right and left coronary arteries, which arise directly from the aortic root. Most cardiac venous blood drains into the right atrium via the coronary sinus.
Myocardial oxygen extraction is very high, the resting myocardium extract 60-75% of oxygen from blood, much higher than any other tissue or organ in the body. As a result, the cardiac venous blood in the coronary sinus is the most deoxygenated blood in the body, more deoxygenated than that carried by other veins like the internal jugular (A) or portal vein (B).
The pulmonary vein (E) carries oxygenated blood to the left atrium.
Deoxygenated systemic blood returning via the vena cava contains more oxygen than the coronary sinus venous blood. Pulmonary artery (D) contains an admixture of blood from the vena cava and coronary sinus, so its oxygen content is higher than pure coronary venous return
Card from 2018 - 2019 lectures
A failure of the aortico-pulmonary septum to follow a spiral course results in which of the following conditions?
a. Common atrium
b. Persistent atrioventricular canal
c. Persistent truncus arteriosus
d. Tetralogy of Fallot
e. Transposition of the great vessels
a. Common atrium – results from complete failure of the septum primum to form
b. Persistent atrioventricular canal – Results from failure of endocardial cushions to fuse and partition the AV canal into right and left components
c. Persistent truncus arteriosus – results from total failure of the aorticopulmonary ridges to develop in the first place and partition the outflow tract. Notice similarity but important distinction from E
d. Tetralogy of Fallot – primary malformation is unequal division of outflow tract, resulting in pulmonary stenosis. Other features are an interventricular septal defect, overriding aorta, RV hypertrophy.
e. Transposition of the great vessels – Correct answer. Occurs when the aorticopulmonary ridges fail to spiral as they divide the outflow tract into two channels. This produces two totally independent circulatory loops, with the RV feeding into the aorta and the LV feeding the pulmonary artery
Card from 2018-2019 lectures
During the first week of life, the umbilical vein can be catheterized and used for central venous pressure monitoring. The umbilical vein leads to which of the following vessels?
a. Descending aorta
b. Ductus arteriosus
c. Ductus venosus
d. Inferior vena cava
e. Umbilical arteries
a. Descending aorta – in the fetus, distributes a mixture of oxygenated blood from IVC (via umbilical vein and ductus venosus) directed via foramen ovale (inferior vena cava -> right atrium -> patent foramen ovale -> left atrium -> left ventricle -> aorta) and deoxygenated blood from SVC (SVC -> RA -> RV - > pulmonary artery -> ductus arteriosus -> descending aorta)
b. Ductus arteriosus – allows bypass of deoxygenated blood from pulmonary trunk to descending aorta, due to high fetal pulmonary artery resistance
c. Ductus venosus – correct answer. In the fetus, umbilical vein connects directly to the ductus venosus, which bypasses the liver to bring oxygenated blood to the inferior vena cava (choice D)
d. Inferior vena cava – see explanation for C above
e. Umbilical arteries – carry blood from descending aorta for return to the placenta for oxygenation
Card from 2018-2019 lectures
A 4th year medical student is learning to place a central line. She knows that the central venous catheter is inserted into the subclavian vein and subsequently threaded into the superior vena cava. To prepare for this procedure, she reviews the CT scan below, taken at the level indicated by the bottom right insert. What is the structure pointed to by arrow 3?
a. Ascending aorta
b. Azygous vein
c. Descending aorta
d. Superior vena cava
a. Ascending aorta – arrow 4
b. Azygous vein – indicated by arrow 1, at same posterior level as descending aorta but on right side
c. Descending aorta – arrow 5, posterior to ascending aorta
d. Superior vena cava – arrow 3 points to superior vena cava, this is the correct answer.
Note: Arrow 2 indicates the right bronchus.
Card from 2018-2019 lectures
You are concerned that your patient may have compromised function of the mitral valve. The sound of the mitral valve is best heard at which of the following locations?
a. At the apex in the left fifth intercostal space in the midclavicular line
b. In the fifth intercostal space to the right of the sternum
c. In the second intercostal space to the left of the sternum
d. In the second intercostal space to the right of the sternum
a. At the apex in the left fifth intercostal space in the midclavicular line – correct answer
b. In the fifth intercostal space to the right of the sternum – tricuspid valve best heard here
c. In the second intercostal space to the left of the sternum – pulmonary valve best heard here
d. In the second intercostal space to the right of the sternum – aortic valve best heard here
Card from 2018-2019 lectures
A 38-year old man is evaluated for palpitations provoked by anxiety. The patient describes a sudden-onset pounding sensation in the chest, followed by lightheadedness and shortness of breath. The patient has no history of heart disease and family history is unremarkable. After evaluation, he is treated with verapamil (Calcium channel blocker) and reports marked improvement in the frequency of palpitation episodes. The tracing below shows the electrical activity of a specific type of cardiac cell in the patient’s heart.
Which of the following effects would verapamil administration most likely have on these cells?
a. Increased action potential amplitude
b. Decreased excitation and contraction coupling
c. Lowered threshold potential
d. Reduced refractory period
e. Slowed spontaneous depolarization
a. Increased action potential amplitude – see C below
b. Decreased excitation and contraction coupling - Verapamil does decrease the amount of intracellular calcium available for excitation-contraction coupling in cardiac myocytes. This is why verapamil can be harmful in patients with impaired ventricular function. However, the tracing shown corresponds to pacemaker action potentials (nodal cells), not cardiac myocyte action potential (non-nodal cells)
c. Lowered threshold potential – Threshold potential refers to amount of depolarization required to initiate an action potential. Class I (Na channel blockers) and class IV (Ca channel blockers) antiarrhythmics raise the threshold potential of non-nodal and nodal cells, respectively, by blocking the channels that trigger and action potential. This effect also results in decreased action potential amplitude(A) and decreased upslope.
d. Reduced refractory period – Verapamil would increase refractory period by slowing the recovery of inactivated calcium channels. Class III antiarrhythmics (K channel blockers) also increase the refractory period.
e. Slowed spontaneous depolarization – correct answer.
Explanation: the above tracing demonstrates the action potential of cardiac pacemaker cells such as the sinoatrial (SA) or atrioventricular(AV) nodes. The pacemaker action potential includes the following phases:
Phase 4 = spontaneous depolarization – slow influx of Na+ions (funny current) makes the membrane potential become more and more positive, which allows T-type (transient) Ca2+channels to open. This Ca2+influx further contributes to depolarization. As the pacemaker cell approaches threshold, L-type (long lasting) Ca2+channels begin to open, which further increases Ca2+ influx and significantly decreases time until threshold is reached.
Phase 0 = upstroke. Characterized by continuous opening of L-type Ca2+ channels. In cardiac pacemaker tissue, action potential upstroke is slow and gradual due to relatively slow influx of Ca2+ into the cell
Phase 3 = repolarization. Characterized by the opening of K+channels and efflux of K+ from the cell, in conjunction with closure of Ca channels, which lead to repolarization of the cell membrane
Card from 2018-2019 lectures
A 5-year old girl is diagnosed with atrial septal defect. Her right heart is hypertrophied, with a fixed split of the second heart sound, a pulmonic diastolic murmur and a systolic murmur. Figure below shows the right ventricular pressures during a single heart beat. At what point is the fixed split of the second heart sound heard?
A
B
C
D
E
D
Explanation: The second heart sounds occurs with the closing of the outlet valves of the right and left ventricles: the aortic and pulmonic valves, as the ventricle pressure is decreasing from the peak systolic pressure (choice D is correct). Increased right ventricular pressure will delay the closing of the pulmonic valve component of the second heart sound, so that a splitting of the sound will occur on auscultation.
Choice A = time of atrial contraction, which if it is heard, will represent the fourth heart sound (S4).
Choice B represents the closing of the AV valves of right and left heart (tricuspid and mitral), this is heard as the first heart sound.
Choice C = opening of outlet valves of heard, not heard on auscultation.
Choice E = opening of AV valves, not heard as well.
Card from 2018 - 2019 lectures
A 34-year old man comes to the clinic for evaluation of a heart murmur. The patient has no chest pain, palpitations, dizziness, shortness of breath at rest. He exercises regularly without any symptoms. Cardiac auscultation in the second right intercostal space reveals and ejection click along with a soft systolic murmur radiating to the neck. A normal volume and pressure tracing of the left ventricle is shown in the tracing below. Which of the following letters corresponds to the opening of the valve most likely affected in this patient?
A
B
C
D
D
Explanation: This young, asymptomatic patient with a soft systolic ejection murmur at the right second intercostal space most likely has a bicuspid aortic valve. Aortic valve opening occurs when the LV pressure exceeds the central aortic pressure at the end of the isovolumetric contraction (B is correct).
Subsequently, LV pressure continues to rise with forward blood flow into the aorta, until the pressure in the LV falls below aortic pressure, leading to aortic valve closure (choice C).
Choice A = initial part of LV pressure and volume curve corresponds to atrial systole, which results in slight increase in LV volume and pressure. This is immediately followed by mitral valve closure and the beginning of isovolumetric contraction.
Choice D = left atrial pressure gradually increases from passive filling from the pulmonary veins and exceeds LV pressure at the end of isovolumetric relaxation, leading to the opening of the mitral valve.
Card from 2018-2019 lectures
Special electrodes are used to detect the changes in membrane potential of a specific type of cardiac cell. These changes are recorded on the graph below. The deflection indicated by the arrow is most likely caused by movement of which of the following ions?
a. Sodium
b. Potassium
c. Calcium
d. Chloride
a. Sodium – pacemaker cells have automaticity, made possible by a slow, inward sodium current that occurs during phase 4 of the action potential
b. Potassium – phase 3 repolarization is caused by an outward potassium channel
c. Calcium – correct answer. Graph illustrates action potential typical of cardiac pacemaker cells, like those found in the SA node. Arrow points to phase 0 depolarization caused by increased calcium conductance.
d. Chloride – does not contribute to any of the phases of the cardiac pacemaker AP
Card from 2018 - 2019 lectures
