Cardiovascular System Practice Questions

Q: The recording of cardiac cycle is drawn below. Which of the following is correct about $X$ and $Y$ shown in the image?

$X=$ Pre-ejection period and $Y=$ LV ejection time. ***X = Pre-ejection period and Y = LV ejection time*** - **X** corresponds to the **pre-ejection period (PEP)**, which is the time from the onset of ventricular depolarization (Q wave on ECG) to the opening of the aortic valve (AO). It includes the **isovolumetric contraction time**. - **Y** corresponds to the **left ventricular (LV) ejection time (LVET)**, which is the interval from the opening of the aortic valve (AO) to its closure (AC), during which blood is ejected into the aorta. *X = Pre-ejection period and Y = Electromechanical systole* - While X correctly represents the **pre-ejection period**, Y is not the **electromechanical systole**. - **Electromechanical systole** is the total time from the Q wave on the ECG to the closure of the aortic valve (AC), encompassing both PEP and LVET. *X = LV ejection Time and Y = Pre-ejection period* - This option incorrectly identifies X as **LV ejection time** and Y as the **pre-ejection period**. - The diagram clearly shows X precedes Y, with X representing the initial phase of ventricular contraction before ejection. *X = Electromechanical systole and Y = LV ejection time* - This option incorrectly identifies X as **electromechanical systole**. X is only a part of the electromechanical systole (the pre-ejection period). - While Y correctly identifies the **LV ejection time**, the initial part of the statement is incorrect.

Q: The following diagram represents flow in compliant versus non-compliant aorta. This shows operation of:

Windkessel effect. ***Windkessel effect*** - The diagram perfectly illustrates the **Windkessel effect**, where the **elasticity of the aorta** allows it to expand during systole to store blood and then recoil during diastole to maintain continuous blood flow. - In a **compliant aorta**, during systole, 100% of the blood enters, but only 50% immediately flows forward as the aorta expands. During diastole, the aortic valves close, and the stored blood (the other 50%) is propelled forward due to the aorta's retraction, maintaining distal blood flow. *Ohm's law* - Ohm's law, when applied to circulation, describes the relationship between **blood flow (I)**, **pressure difference (ΔP)**, and **vascular resistance (R)** (I = ΔP/R). - This diagram focuses on the aorta's physical properties and blood buffering, not primarily on resistance or pressure gradients due to flow. *Poiseuille's law* - Poiseuille's law calculates **fluid flow rate** through a cylindrical tube, heavily dependent on the **vessel radius**, length, and fluid viscosity. - While relevant to blood flow dynamics in general, it does not explain the specific phenomenon of elastic energy storage and release by the aorta during the cardiac cycle. *Frank-Starling mechanism* - The Frank-Starling mechanism describes the heart's ability to **change its force of contraction** in response to changes in **venous return** and **end-diastolic volume**. - This mechanism is about cardiac muscle physiology and pump function, not the vascular mechanics of the aorta, as depicted.

Q: Which of the following dissociation curve mentioned is for myoglobin?

Green. ***Green*** - The **green curve** represents **myoglobin**, which has a much higher affinity for oxygen than hemoglobin. It binds oxygen at very low partial pressures and releases it only when oxygen levels are significantly depleted, as in active muscle tissue. - Myoglobin's dissociation curve is typically **hyperbolic** due to its single oxygen-binding site, reflecting its role in oxygen storage rather than transport. *Purple* - The **purple curve** represents normal **hemoglobin**, which exhibits a **sigmoidal** shape due to its **cooperative binding** of oxygen. This allows hemoglobin to efficiently load oxygen in the lungs and unload it in tissues. - Hemoglobin has a lower oxygen affinity than myoglobin and is designed for oxygen transport, adapting its binding based on oxygen partial pressure. *Red* - The **red curve** likely represents a **right-shifted hemoglobin dissociation curve**, indicating **decreased oxygen affinity**. This shift facilitates oxygen unloading to tissues. - Right shifts occur due to increased temperature, decreased pH (Bohr effect), increased 2,3-DPG, or increased CO₂. These physiological adaptations help deliver more oxygen to metabolically active tissues. *None* - This option is incorrect because the **green curve** clearly represents the characteristic oxygen dissociation curve for myoglobin.

Q: The pressure-volume loop of left ventricle tracing of the patient indicates:

Diastolic dysfunction. ***Diastolic dysfunction*** - The pressure-volume loop for the patient is shifted to the **left and upward** relative to the control loop, indicating higher left ventricular pressure for a given volume during diastole. - The **end-diastolic pressure-volume relationship (EDPVR)**, shown by the lower right curve, is steeper for the patient, meaning the ventricle is **stiffer or less compliant** during filling. *Systolic dysfunction* - Systolic dysfunction would be characterized by a **reduced stroke volume** (narrower loop horizontally) and a **lower ejection fraction**, often accompanied by a shift to the right due to increased end-diastolic volume. - The **end-systolic pressure-volume relationship (ESPVR)**, which represents contractility, would be shifted downwards and to the right in systolic dysfunction, indicating impaired contractility. *Decreased atrial compliance* - Decreased atrial compliance would primarily affect **atrial pressures** and the force of atrial contraction, which might indirectly impact ventricular filling, but is not directly represented by the ventricular pressure-volume loop's morphology in this manner. - The primary indicator of atrial compliance is often via atrial pressure-volume relationships or specific atrial function studies, not the ventricular loop's overall shift. *Increased atrial compliance* - Increased atrial compliance would allow the atria to accommodate more volume at lower pressures, potentially *improving* ventricular filling if the ventricle itself is compliant, but it would not explain the **elevated ventricular diastolic pressures** seen in the patient's tracing. - This condition would typically lead to lower atrial pressures, which is the opposite of what would contribute to the observed ventricular diastolic dysfunction.

Q: Which of the following is correct about the point marked $Z$ on the cardiac cycle?

Aortic valve opens. ***Aortic valve opens*** - At point Z, the **left ventricular pressure (LVP)** curve (solid red line) intersects and surpasses the **aortic pressure (AP)** curve (dashed line), marking the moment the **aortic valve opens** and blood begins to be ejected into the aorta. - This event signifies the transition from **isovolumetric contraction** to rapid **ventricular ejection phase** during systole. *Mitral valve opens* - The **mitral valve opens** during diastole, when the **left ventricular pressure (LVP)** falls below the **left atrial pressure (LAP)**, allowing ventricular filling. - This event would typically occur much later in the cardiac cycle, around point 5 or 6, after the aortic valve closes. *Tricuspid valve opens* - The **tricuspid valve opens** during diastole when the right ventricular pressure falls below the right atrial pressure. This event is not directly depicted for the left side of the heart in this Wigger's diagram. - It plays a role in right heart filling and is not related to the events occurring at point Z in the left heart cycle. *Mid systolic click* - A **mid-systolic click** is typically associated with **mitral valve prolapse**, occurring during mid-systole as the mitral leaflets prolapse into the left atrium. - Point Z represents the beginning of ejection, not a valvular abnormality.

Q: Which of the following is correct about the 'X' marking in Arterial Waveform?

Closure of aortic valve. ***Closure of aortic valve*** - The "X" marking in the arterial waveform, also known as the **dicrotic notch**, represents the brief reversal of blood flow in the aorta due to the **closure of the aortic valve**. - This event signifies the end of systole and the beginning of diastole in the arterial pressure waveform. *Closure of mitral valve* - The closure of the mitral valve occurs at the **beginning of ventricular systole** and is not directly represented as a dicrotic notch on an arterial pressure waveform. - Mitral valve closure is associated with the first heart sound (S1) and changes in left ventricular pressure, not a notch in the arterial waveform. *Closure of tricuspid valve* - The closure of the tricuspid valve also occurs at the **beginning of ventricular systole**, similar to the mitral valve, only on the right side of the heart. - This event is not reflected as a dicrotic notch in the systemic arterial pressure waveform. *Rapid filling of left ventricle* - Rapid filling of the left ventricle occurs during **early diastole**, when the mitral valve is open. - This phase is associated with changes in ventricular pressure, but not with the dicrotic notch, which signifies arterial pressure changes due to aortic valve closure.

Q: Which of the following is correct about the pressure volume loop of left ventricle?

Aortic valve opens at 2. ***Aortic valve opens at 2*** - Point 2 marks the moment when **left ventricular pressure exceeds aortic pressure**, causing the aortic valve to open. - This is the transition point between **isovolumetric contraction** (1→2) and **ventricular ejection** (2→3). - From point 2 onwards, blood is actively ejected from the left ventricle into the aorta during **systole**. *1 to 2 indicates isovolumetric relaxation* - The phase from point 1 to point 2 shows an increase in **pressure at constant volume**, which represents **isovolumetric contraction**, not relaxation. - During **isovolumetric contraction**, both the mitral and aortic valves are closed, and the ventricle contracts without changing volume, building up pressure. - **Isovolumetric relaxation** occurs from point 3 to point 4, where pressure drops at constant volume after the aortic valve closes. *2 to 3 indicates ventricular diastole* - The period from point 2 to point 3 represents **ventricular ejection**, which is part of **ventricular systole**, not diastole. - During this phase, the aortic valve is open, and blood is being ejected from the left ventricle into the aorta while ventricular volume decreases. - **Ventricular diastole** includes isovolumetric relaxation (3→4) and ventricular filling (4→1). *Pulmonic valve opens at 3* - Point 3 represents the **closure of the aortic valve** at the end of ventricular ejection, not its opening. - The **pulmonic valve** is part of the right ventricular circuit, not the left ventricle; it opens during right ventricular ejection into the pulmonary artery. - This question specifically addresses the **left ventricular** pressure-volume loop.

Q: The A wave in His bundle electrogram shows presence of:

Atrial depolarization. ***Atrial depolarization*** - The **A wave** in a His bundle electrogram represents the electrical activity corresponding to **atrial depolarization**. This is the first electrical event recorded prior to ventricular activation. - It signifies the activation of the atria, preceding the impulse transmission through the AV node and His bundle. *Atrial repolarization* - **Atrial repolarization** is generally not clearly visible as a distinct wave in a His bundle electrogram, as its electrical signal is usually small and often obscured by the much larger QRS complex from ventricular depolarization. - The T-wave on a surface ECG corresponds to ventricular repolarization, and there isn't a directly analogous, easily identifiable wave for atrial repolarization in standard His bundle recordings. *AV node activation* - **AV node activation** itself is a slow electrical process that does not generate a distinct, sharply defined wave in the His bundle electrogram. - The time taken for conduction through the AV node is represented by the **AH interval**, which is the duration between the A wave (atrial activation) and the H wave (His bundle activation). *Atrial depolarization to AV node activation* - This option describes a **duration or interval**, specifically the **AH interval**, which reflects the time from the beginning of atrial activation (A wave) to the beginning of His bundle activation (H wave) and primarily represents AV nodal conduction. - The A wave itself signifies a specific electrical event (**atrial depolarization**), not the entire period from atrial depolarization up to AV node activation.

Q: The lead of ECG marked as $X$ is called:

Lewis lead. ***Lewis lead*** - This image displays the placement of electrodes for a **Lewis lead** ECG, used to enhance the detection of **atrial activity**, particularly for P waves. - The Lewis lead involves placing the right arm electrode (usually from a standard ECG setup) at the **right sternal border in the second intercostal space**, and the left arm electrode at the **right parasternal border in the fourth intercostal space**. *V4R* - **V4R** is a right-sided precordial lead used to detect **right ventricular infarction** and is placed in the fifth intercostal space at the right midclavicular line. - The electrode placement shown in the image is not consistent with V4R. *aVR* - **aVR** is an augmented unipolar limb lead that records electrical activity from the **right arm** relative to the average of the left arm and left leg electrodes. - It is not a chest lead placement, and therefore does not correspond to the image. *V_{a}* - **V_{a}** is not a standard or recognized ECG lead designation in clinical practice. - The commonly used precordial leads are denoted as V1 through V6.

Q: The phase of cardiac action potential marked Green is related to which of the following?

Calcium entry, L channels. ***Calcium entry, L channels*** - The green phase represents **Phase 0 (rapid depolarization)** of the **SA node action potential**, which is primarily mediated by **L-type calcium channels** rather than sodium channels. - **SA node cells lack fast voltage-gated sodium channels (Nav1.5)**, making them dependent on **slow calcium influx** through L-type channels for depolarization, unlike ventricular myocytes. *Sodium entry* - **Fast sodium channels** are responsible for Phase 0 in **ventricular and atrial myocytes**, but are **absent in SA node cells**. - The rapid sodium influx creates the characteristic steep upstroke in non-pacemaker cardiac cells, which differs from the slower calcium-dependent depolarization in pacemaker cells. *Calcium entry, T channels* - **T-type calcium channels** contribute to **Phase 4 (pacemaker depolarization)** and help bring the membrane potential to threshold, not Phase 0. - These channels have **faster inactivation kinetics** compared to L-type channels and are not the primary contributors to the depolarization phase marked in green. *Mixed sodium and potassium current* - **If (funny current)** involving mixed **sodium and potassium influx** occurs during **Phase 4** and is responsible for the **spontaneous diastolic depolarization** in pacemaker cells. - This current gradually brings the membrane potential to threshold but does not mediate the actual depolarization phase shown in the green marking.

Question 1

The recording of cardiac cycle is drawn below. Which of the following is correct about $X$ and $Y$ shown in the image?

Accepted Answer

$X=$ Pre-ejection period and $Y=$ LV ejection time

Answer

$X=$ Pre-ejection period and $Y=$ Electromechanical systole

Answer

$X=$ LV ejection time and $Y=$ Pre-ejection period

Answer

$X=$ Electromechanical systole and $Y=$ LV ejection time

Question 2

The following diagram represents flow in compliant versus non-compliant aorta. This shows operation of:

Accepted Answer

Windkessel effect

Answer

Ohm's law

Answer

Poiseuille's law

Answer

Frank-Starling mechanism

Question 3

Which of the following dissociation curve mentioned is for myoglobin?

Accepted Answer

Green

Answer

Purple

Answer

Red

Answer

None

Question 4

The pressure-volume loop of left ventricle tracing of the patient indicates:

Accepted Answer

Diastolic dysfunction

Answer

Systolic dysfunction

Answer

Decreased atrial compliance

Answer

Increased atrial compliance

Question 5

Which of the following is correct about the point marked $Z$ on the cardiac cycle?

Accepted Answer

Aortic valve opens

Answer

Mitral valve opens

Answer

Tricuspid valve opens

Answer

Mid systolic click

Question 6

Which of the following is correct about the 'X' marking in Arterial Waveform?

Accepted Answer

Closure of aortic valve

Answer

Closure of mitral valve

Answer

Closure of tricuspid valve

Answer

Rapid filling of left ventricle

Question 7

Which of the following is correct about the pressure volume loop of left ventricle?

Accepted Answer

Aortic valve opens at 2

Answer

1 to 2 indicates isovolumetric relaxation

Answer

2 to 3 indicates ventricular diastole

Answer

Pulmonic valve opens at 3

Question 8

The A wave in His bundle electrogram shows presence of:

Accepted Answer

Atrial depolarization

Answer

Atrial repolarization

Answer

AV node activation

Answer

Atrial depolarization to AV node activation

Question 9

The lead of ECG marked as $X$ is called:

Accepted Answer

Lewis lead

Answer

V4R

Answer

aVR

Answer

V_{a}

Question 10

The phase of cardiac action potential marked Green is related to which of the following?

Accepted Answer

Calcium entry, L channels

Answer

Sodium entry

Answer

Calcium entry, T channels

Answer

Mixed sodium and potassium current

Cardiovascular System — MCQs

Cardiovascular System — MCQs

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