20181206-20181212 Flashcards
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 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 – 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
Learning objectives:
113a Link the function of the cardiac action potential to myocyte activation
114a Describe genesis of cardiac action potential
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
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
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.
Learning objectives:
115a-116a Explain the timing and mechanism of S1, S2, S3, S4, and murmurs
Draw the Wiggers diagram, and integrate the interrelationships among the components
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
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
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.
Learning objectives
108a
Describe the structures of the four valves, their names, and how they work. Give some examples of valve pathology and the effect on cardiac function.
115-116a
Explain the timing and mechanism of S1, S2, S3, S4, and murmurs
Draw the Wiggers diagram, and integrate the interrelationships among the components
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
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 – 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
Learning objectives:
113a Link the function of the cardiac action potential to myocyte activation
114a Describe genesis of cardiac action potential
A 10-year old boy is brought to the clinic by his parents due to chronic fatigue, shortness of breath and failure to gain weight. Physical examination reveals a systolic murmur. Echocardiogram shows pulmonary stenosis and subaortic ventricular septal defect with deviation of the origin of the aorta to the right. The parents describe several episodes of severe dyspnea and cyanosis, during which the child quickly assumes a squatting position. Which of the following mechanisms during squatting relieves the child’s symptoms?
a. Decreasing pulmonary blood flow
b. Decreasing pulmonary vascular resistance
c. Increases lung compliance
d. Increasing systemic vascular resistance
A 10-year old boy is brought to the clinic by his parents due to chronic fatigue, shortness of breath and failure to gain weight. Physical examination reveals a systolic murmur. Echocardiogram shows pulmonary stenosis and subaortic ventricular septal defect with deviation of the origin of the aorta to the right. The parents describe several episodes of severe dyspnea and cyanosis, during which the child quickly assumes a squatting position. Which of the following mechanisms during squatting relieves the child’s symptoms?
a. Decreasing pulmonary blood flow – this increases, due to lower pulmonary : systemic vascular resistance ratio, see explanation below
b. Decreasing pulmonary vascular resistance
c. Increases lung compliance – not affected by squatting
d. Increasing systemic vascular resistance – correct answer, see explanation below
Explanation: The child has Tetralogy of Fallot with ventricular septal defect, overriding aorta, pulmonary stenosis and right ventricular hypertrophy. The pulmonary stenosis increases the pulmonary vascular resistance, while the overriding aorta (overrides the septal defect) leads to a lower systemic vascular resistance than normal. Therefore, deoxygenated right ventricular output takes the low-resistance route to the systemic circulation, leading to hypoxemia. Children with tetralogy of Fallot quickly learn to squat to relieve these hypoxemic episodes. This posture quickly increases systemic vascular resistance (D is correct), without affecting pulmonary vascular resistance (choice B). This forces a higher proportion of right ventricular output to enter the pulmonary circulation and oxygenate blood before it is distributed to the rest of the body.
Learning objectives:
Predict how changes in venous tone will alter the shape of the vascular function curve, and consequently alter the setpoint of the Guyton diagram.
Predict how changes in systemic vascular resistance will alter the shape of the vascular function curve, and consequently alter the setpoint of the Guyton diagram.
o Describe how exercise modifies the Guyton diagram.
o Describe how heart failure modifeis the Guyton diagram.
A group of 60 year-old men volunteered for evaluation in a cardiovascular study. All appeared healthy with no history of cardiovascular disease. The loop-labeled “Patient A” was recorded from a 60-year-old man who recounts a mild viral infection four weeks ago. The loop labeled “Control” was from another volunteer. When compared to the control loop, the left ventricular pressure-volume loop from patient A demonstrates which of the following changes?
a. Drug related increased contractility
b. Viral myocarditis-related increased end-systolic pressure
c. Increased pulmonary artery wedge pressure due to valvular disease
d. Increased systemic vascular resistance from age-related vessel stiffening
e. Valve disease-related ventricular dilation
A group of 60 year-old men volunteered for evaluation in a cardiovascular study. All appeared healthy with no history of cardiovascular disease. The loop-labeled “Patient A” was recorded from a 60-year-old man who recounts a mild viral infection four weeks ago. The loop labeled “Control” was from another volunteer. When compared to the control loop, the left ventricular pressure-volume loop from patient A demonstrates which of the following changes?
a. Drug related increased contractility
b. Viral myocarditis-related increased end-systolic pressure
c. Increased pulmonary artery wedge pressure due to valvular disease
d. Increased systemic vascular resistance from age-related vessel stiffening
e. Valve disease-related ventricular dilation
Explanations:
E – Pt has incompetent aortic valve resulting in AR and LV dilatation. Regurgitant flow is evident from the isovolumetric phases of the graph (which are not isovolumetric – the volume increases when the valves should be closed). Pulse pressure also increases on the graph due to retrograde flow through an incompetent valve decreased DBP. Volume overload leads to increased compliance as the heart dilates.
A – Contractility decreases, B – end systolic pressure decreases, C – mean pulmonary artery wedge pressure is estimated by the end diastolic pressure – which is identical in both loops, D – DBP (which is largely determined by SVR) is lower in patient A than in the control
Learning objectives:
115-116a Draw the pressure-volume loop
115-116a Diagram the effects of increased preload, afterload, and contractility on the pressure-volume loop
A 72-yr-old man with a history of type II diabetes and hypertension is brought to the ED because of sudden onset chest pain and dyspnea. His pulse is 110/min and blood pressure is 90/60 mm Hg. Cardiac auscultation reveals no murmurs, rubs, or gallops. Because of his hemodynamic instability, a central venous catheter is placed. The image shows the central line tracings from a normal patient during one cardiac cycle with corresponding aortic, left ventricular, and left atrial pressures. At which of the following points on the curve is the sarcomere length of the left ventricular muscle fibers the smallest?
A
B
C
D
E
F
A 72-yr-old man with a history of type II diabetes and hypertension is brought to the ED because of sudden onset chest pain and dyspnea. His pulse is 110/min and blood pressure is 90/60 mm Hg. Cardiac auscultation reveals no murmurs, rubs, or gallops. Because of his hemodynamic instability, a central venous catheter is placed. The image shows the central line tracings from a normal patient during one cardiac cycle with corresponding aortic, left ventricular, and left atrial pressures. At which of the following points on the curve is the sarcomere length of the left ventricular muscle fibers the smallest?
A
B
C
D
E
F
Explanation: Sarcomere length is smallest when the left ventricle is at maximal contraction
Learning objectives:
115-116a Draw the Wiggers diagram, and integrate the interrelationships among the components
113a Sketch the ultrastructure of cardiomyocytes, including the structure of the sarcomere, T-tubules, the sarcoplasmic reticulum, mitochondria, denoting functions of each.
113a Map the contractile cycle
A middle-aged woman reports episodes of fainting and dizziness while standing at her job. Her seated blood pressure is 123/72 mm Hg and pulse is regular at 75/min. Hemodynamic studies are performed to evaluate her. Her blood volume is 4.2 L and resting cardiac output is 4.2 L/min. In the supine posture at rest, which of the following vascular structures will most likely contain the largest proportion of the total blood volume in this patient?
a. Aorta and larger arteries
b. Arterioles
c. Capillaries
d. Chambers of the heart
e. Pulmonary vasculature
f. Vena Cavae
g. Venules and veins
A middle-aged woman reports episodes of fainting and dizziness while standing at her job. Her seated blood pressure is 123/72 mm Hg and pulse is regular at 75/min. Hemodynamic studies are performed to evaluate her. Her blood volume is 4.2 L and resting cardiac output is 4.2 L/min. In the supine posture at rest, which of the following vascular structures will most likely contain the largest proportion of the total blood volume in this patient?
a. Aorta and larger arteries
b. Arterioles
c. Capillaries
d. Chambers of the heart
e. Pulmonary vasculature
f. Vena Cavae
g. Venules and veins
Explanation: Just a fact that venous system has the most capacitance and is the reservoir for blood
Learning objectives:
110a
Define the following: shear, compliance, pulse pressure, systolic pressure, diastolic pressure, stroke volume, and cardiac output.
118a
Predict how changes in venous tone will alter the shape of the vascular function curve, and consequently alter the setpoint of the Guyton diagram.
A healthy 25-yr-old woman begins a program that includes weight lifting and high-intensity static exercise. Which of the following is most likely to occur within her skeletal muscles during contraction while performing this type of exercise?
a. Decreased blood flow and increased vascular resistance
b. Decreased extracellular potassium concentration
c. Increased arteriolar diameter and increased flow
d. Increased ADP/ATP ratio
e. Increased intracellular potassium concentration
A healthy 25-yr-old woman begins a program that includes weight lifting and high-intensity static exercise. Which of the following is most likely to occur within her skeletal muscles during contraction while performing this type of exercise?
a. Decreased blood flow and increased vascular resistance
b. Decreased extracellular potassium concentration
c. Increased arteriolar diameter and increased flow
d. Increased ADP/ATP ratio
e. Increased intracellular potassium concentration
Explanation: Muscle contraction compresses and collapses vessels leading to increased resistance and decreased blood flow.
Learning objective:
118a Describe how exercise modifies the Guyton diagram.
122a List two systemic and three local mechanisms for control of local blood flow.
122a Elaborate on myogenic and metabolic control of local circulation.
Which of the following occurs if a patient is given a low dose of epinephrine?
- Increase in heart rate and contractility
- Increase in total peripheral resistance
- Decrease in arterial blood pressure
- Vascular effects of alpha receptors dominate
The correct answer is A. Epinephrine binds to both beta and alpha receptors with a greater effect on beta receptors. Its effects on beta1 receptors will lead to an increased heart rate and contractility, which leads to greater cardiac output and an increase in arterial blood pressure.
B is incorrect. When given a low dose of epinephrine, beta2-receptor effects dominate over alpha1 receptor effects. So vasodilation dominates leading to a net effect of a decrease in total peripheral resistance, not an increase.
C is incorrect. Epinephrine increases the arterial blood pressure by increasing cardiac output.
D is incorrect. At a low dose, vascular effects of the beta receptors dominate. At a high dose, the alpha effects predominate.
Learning issues covered:
119a Describe the roles of oxygen, vasoactive tissue metabolites, physical factors and others in the regulation of tissue blood flow.
A 23 year-old woman presents to the emergency department with trauma to her leg and blood loss. When she is supine, her blood pressure is 88/60 mmHg and her heart rate is 98 bpm. When she is upright, her heart rate further increases to 115 bpm. Which of the following explains her further increase in heart rate?
- Increased afferent baroreceptor firing
- Decreased venous return
- Decreased efferent sympathetic firing
- Increased afterload
The correct answer is B. The patient is hemorrhaging and thus has decreased venous return to the heart. This leads to decreased arterial pressure, decreased stretch of the blood vessel , decreased afferent baroreceptor firing, increased efferent sympathetic firing and decreased efferent parasympathetic stimulation, resulting in vasoconstriction through alpha 1 receptors, an increase in heart rate through beta 1 receptors, and an increase in blood pressure.
When the patient stands up, venous return is further decreased due to blood pooling in her legs leading to a further decrease in blood pressure. Through the same baroreceptor mechanism, the heart rate thus further increases.
Thus, the physiological response to standing upright from a supine position is similar to the response to mild hemorrhage or loss of intravascular volume (severe diarrhea, etc.).
A is incorrect. The decreased arterial pressure would lead to decreased afferent baroreceptor firing, not increased.
C is incorrect. Increased efferent sympathetic firing, not decreased sympathetic firing leads to increased systemic vascular resistance and increased heart rate through alpha1 and beta 1 receptors.
D is incorrect. Hemorrhage would lead to decreased afterload (decreased mean arterial pressure), not increased.
Learning issue covered:
118a-119a
- Explain the arterial baroreceptor reflex. 5. Explain the circulatory adjustments that occur as a result of normal activities of the body (standing, changing position, etc.).
In which of the following organs is autoregulation not primarily determined by the production of local metabolites?
- Brain
- Heart
- Skeletal muscle
- Skin
The correct answer is D. Autoregulation of vascular beds in the skin is predominantly controlled by sympathetic stimulation, not by local metabolites. These cutaneous sympathetic nerves are regulated by temperature. For example, increased temperature leads to vasodilation to allow for dissipation of heat.
A is incorrect. Autoregulation in the brain is determined by local metabolites that are vasodilatory including CO2 which is affected by the blood pH. Autoregulation in the brain is also influenced by tissue pressure since there is limited compliance in the brain interstitium.
B is incorrect. Autoregulation in the heart is determined by local metabolites that are vasodilatory including adenosine from ATP metabolism, nitric oxide, carbon dioxide, and decreased oxygen levels.
C is incorrect. Autoregulation in the skeletal muscle is determined by local metabolites that are produced during exercise including lactate, adenosine, potassium, hydrogen ions, and carbon dioxide. This is also an example of active hyperemia.
Learning issues covered:
122a
Describe autoregulation, active hyperemia, and reactive hyperemia.
Define autoregulation of blood flow and define which vascular beds exhibit this.
