Cardiovascular System — MCQs

Cardiovascular System Indian Medical PG Practice Questions and MCQs

Question 741: The central venous pressure (CVP) is low in

A. Massive pulmonary embolism
B. Tension pneumothorax (Correct Answer)
C. Acute left ventricular failure
D. Pericardial effusion

Explanation: ***Tension pneumothorax*** - A **tension pneumothorax** causes compression of the **superior and inferior vena cava** due to increased intrathoracic pressure and mediastinal shift. - This compression **impairs venous return** to the right atrium, leading to **decreased central venous pressure (CVP)**. - Despite elevated intrathoracic pressure, the net effect is **reduced venous return and low CVP**, along with hypotension and cardiac compromise. - This is a life-threatening emergency requiring immediate needle decompression. *Acute left ventricular failure* - In **acute left ventricular failure**, the left ventricle fails to pump blood effectively, causing backup into the pulmonary circulation. - However, the **right ventricle continues to pump** blood into the pulmonary circulation, leading to **increased right atrial pressure and elevated CVP**. - Patients typically present with **elevated CVP** along with pulmonary edema and dyspnea. *Massive pulmonary embolism* - A **massive pulmonary embolism** causes acute increase in **pulmonary vascular resistance** and right ventricular afterload. - The right ventricle becomes acutely strained and dilated, leading to **elevated right atrial pressure and increased CVP**. - Clinical features include hypotension, tachycardia, and jugular venous distension indicating high CVP. *Pericardial effusion* - A **pericardial effusion** causing **cardiac tamponade** compresses all cardiac chambers and restricts ventricular filling. - This leads to **equalization of diastolic pressures** in all chambers and **markedly elevated CVP**. - Classic Beck's triad includes hypotension, muffled heart sounds, and **jugular venous distension** (elevated CVP).

Question 742: In pregnancy, there is a physiological increase of the

A. cardiac output (Correct Answer)
B. blood viscosity
C. peripheral resistance of the blood vessels
D. blood pressure in the third trimester

Explanation: ***cardiac output*** - **Cardiac output** increases significantly in pregnancy, by approximately 30-50%, to meet the increased metabolic demands of the growing fetus and maternal tissues. - This increase is primarily due to increases in both **heart rate** and **stroke volume**. *blood viscosity* - **Blood viscosity** actually decreases in pregnancy due to a greater increase in **plasma volume** compared to the increase in red blood cell mass, leading to hemodilution. - This reduction in viscosity can contribute to a lower peripheral vascular resistance. *peripheral resistance of the blood vessels* - **Peripheral resistance** typically decreases in pregnancy due to the vasodilatory effects of hormones like **progesterone** and the establishment of the low-resistance uteroplacental circulation. - This vasodilation helps accommodate the increased blood volume and cardiac output without a significant rise in blood pressure. *blood pressure in the third trimester* - **Blood pressure** usually decreases or remains stable in the first and second trimesters, with a slight rise towards pre-pregnancy levels in the third trimester. - A significant increase in blood pressure, especially in the third trimester, is *not* physiological and can indicate complications like **gestational hypertension** or **preeclampsia**.

Question 743: Consider the following hemodynamic changes occurring during pregnancy: 1. Increase in cardiac output 2. Increase in stroke volume 3. Increase in colloid oncotic pressure 4. Increase in pulse rate Which of the statements given above are correct?

A. 1, 3 and 4
B. 1, 2 and 4 (Correct Answer)
C. 2, 3 and 4
D. 1, 2 and 3

Explanation: ***Correct Answer: 1, 2 and 4*** **Statement 1: Increase in cardiac output** - CORRECT - Cardiac output increases by **30-50% during pregnancy**, peaking at 28-32 weeks - This increase is driven by increased blood volume (40-50% increase), higher metabolic demands, and the need to perfuse the uteroplacental unit **Statement 2: Increase in stroke volume** - CORRECT - Stroke volume increases by **20-30% during pregnancy**, particularly in the first and second trimesters - This contributes significantly to the overall increase in cardiac output alongside increased heart rate **Statement 3: Increase in colloid oncotic pressure** - INCORRECT - Colloid oncotic pressure actually **decreases during pregnancy** from normal values of 25-28 mmHg to approximately 22-24 mmHg - This occurs due to **hemodilution** (plasma volume increases more than red cell mass) and **decreased serum albumin concentration** (dilutional hypoalbuminemia) - The reduced oncotic pressure contributes to the **increased tendency for peripheral edema** in pregnant women **Statement 4: Increase in pulse rate** - CORRECT - Heart rate increases by **10-20 beats per minute** during pregnancy - This tachycardia helps maintain adequate cardiac output to meet the increased circulatory demands of pregnancy *Incorrect Options:* *1, 3 and 4* - Statement 3 is incorrect as colloid oncotic pressure decreases, not increases *2, 3 and 4* - Statement 3 is incorrect as colloid oncotic pressure decreases during pregnancy *1, 2 and 3* - Statement 3 is incorrect; colloid oncotic pressure falls due to hemodilution and hypoalbuminemia

Question 744: Regarding haemorrhagic shock, which one of the following statements is correct?

A. Tachycardia presents in 100% of hypovolemic patients
B. Clinically manifested when > 10% of loss of total blood volume occurs
C. Loss of 40% of circulating volume is life threatening (Correct Answer)
D. In acute stage of shock, systemic vasodilation becomes evident

Explanation: ***Loss of 40% of circulating volume is life threatening*** - A loss of **40% or more** of circulating blood volume corresponds to **Class IV haemorrhagic shock**, which is a severe, life-threatening condition requiring immediate and aggressive resuscitation. - At this stage, the body's compensatory mechanisms are overwhelmed, leading to profound systemic hypoperfusion, **organ dysfunction**, and a high risk of mortality. *Tachycardia presents in 100% of hypovolemic patients* - While **tachycardia** is a common compensatory mechanism in hypovolemia, it is not present in 100% of patients due to factors such as **beta-blocker use** or **pacemaker rhythm**. - In some early stages of blood loss, especially in young, healthy individuals, sufficient compensatory mechanisms may delay the onset of significant tachycardia. *Clinically manifested when > 10% of loss of total blood volume occurs* - Haemorrhagic shock is typically **clinically manifest** when there is a blood loss greater than **15%** (Class I shock), which represents approximately 750 mL in an average adult. - A loss of **less than 10%** often does not produce overt clinical signs as the body's compensatory mechanisms can effectively maintain vital signs within normal ranges. *In acute stage of shock, systemic vasodilation becomes evident* - In the acute stage of hemorrhagic shock, the body's primary compensatory mechanism is **systemic vasoconstriction**, not vasodilation, to maintain central blood pressure and perfuse vital organs. - **Vasodilation** can occur in the later, decompensated stages of shock, particularly in instances of **septic or neurogenic shock**, leading to a further drop in blood pressure.

Question 745: What is the function of the umbilical artery in fetal circulation?

A. Provide nutrients
B. None of the options
C. Carry oxygenated blood from the placenta to the fetus
D. Carry deoxygenated blood from the fetus to the placenta (Correct Answer)

Explanation: ***Carry deoxygenated blood from the fetus to the placenta*** - The **umbilical arteries** are responsible for transporting **deoxygenated blood** and waste products away from the fetal circulation to the placenta. - There are typically **two umbilical arteries** that branch off the internal iliac arteries of the fetus. *Provide nutrients* - **Nutrient delivery** to the fetus is primarily a function of the **umbilical vein**, which carries oxygenated and nutrient-rich blood from the placenta. - The umbilical arteries carry metabolic waste products away from the fetus, not nutrients to it. *None of the options* - This option is incorrect because one of the provided options accurately describes the function of the umbilical artery. - The specific role of the umbilical artery is distinct from other fetal circulatory components. *Carry oxygenated blood from the placenta to the fetus* - This function is performed by the **umbilical vein**, which brings **oxygen-rich blood** and nutrients from the placenta to the fetus. - The umbilical arteries carry blood in the opposite direction and with a different oxygenation status.

Question 746: Which among the following organs has the least arteriovenous oxygen difference?

A. Liver
B. Skin
C. Kidney (Correct Answer)
D. Brain

Explanation: ***Kidney*** - The **kidney** has the lowest arteriovenous oxygen difference among these organs because its metabolic activity, relative to its blood supply, is designed for filtration rather than high oxygen extraction for work. - A significant portion of the kidney's oxygen consumption is related to **active transport** and **reabsorption**, but its unusually high blood flow (about 20-25% of cardiac output) ensures that the oxygen content of venous blood remains high. *Liver* - The liver receives a **dual blood supply** (hepatic artery and portal vein) and is highly metabolically active due to its roles in synthesis, detoxification, and nutrient processing, leading to a substantial oxygen extraction and thus a larger arteriovenous oxygen difference. - It has a significant oxygen demand for its numerous physiological functions, resulting in a lower oxygen content in its venous outflow compared to arterial blood. *Skin* - Skin blood flow is highly variable and plays a crucial role in **thermoregulation** in addition to metabolic needs. - While its baseline metabolic rate is moderate, its oxygen extraction can vary, but generally, it has a larger arteriovenous oxygen difference due to the oxygen demand of its various cellular layers and structures. *Brain* - The **brain** has a consistently high metabolic rate and continuous oxygen demand, consuming about 20% of the body's total oxygen at rest. - This consistent and high demand for oxygen results in a relatively large arteriovenous oxygen difference as it extracts a significant portion of oxygen from the arterial blood.

Question 747: Blood pressure changes in radial artery were measured. Which of the following is the reason for initial rise in BP while performing Valsalva maneuver?

A. Increase in Left ventricular volume
B. Increase in Left ventricular pressure
C. Decrease in aortic pressure
D. Increase in aortic pressure (Correct Answer)

Explanation: ***Increase in aortic pressure*** - During the initial phase (Phase I) of the Valsalva maneuver, the sudden **increase in intrathoracic pressure** is transmitted directly to the aorta and other large arteries. - This transient increase in external pressure on the great vessels directly causes a brief **rise in aortic blood pressure** before other compensatory mechanisms take effect. *Increase in Left ventricular volume* - The Valsalva maneuver actually **decreases left ventricular volume** over time due to reduced venous return. - An increase in left ventricular volume would typically lead to a sustained increase in cardiac output and blood pressure, which is not what is observed initially during the Valsalva maneuver. *Increase in Left ventricular pressure* - While increased intrathoracic pressure can transiently affect left ventricular pressure, the initial blood pressure rise is primarily due to direct compression of the **aorta and systemic arteries**, not an intrinsic increase in myocardial contractility or ventricular filling pressure. - Ultimately, the Valsalva maneuver generally leads to a decrease in **left ventricular preload** and subsequent decrease in stroke volume during the prolonged straining phase. *Decrease in aortic pressure* - The graph clearly shows an **initial spike in mean aortic pressure** (Phase I) at the onset of the Valsalva maneuver. - A decrease in aortic pressure is characteristic of the later part of the straining phase (Phase II) due to **reduced cardiac output**.

Question 748: Windkessel effect is not shown by which of the following vessel?

A. Radial (Correct Answer)
B. Renal
C. Aorta
D. Abdominal aorta

Explanation: ***Radial*** - The **radial artery** is a muscular artery, and these vessels primarily regulate blood flow and pressure through vasoconstriction and vasodilation, rather than storing elastic energy. - While all arteries have some elasticity, the **Windkessel effect** is most prominent in large elastic arteries, which are structurally different from muscular arteries like the radial artery. *Renal* - The **renal artery** is a highly compliant, distensible artery that assists in dampening pulsatile flow and ensuring continuous, stable perfusion to the kidneys. - As a major artery off the aorta, it contributes to the **Windkessel effect** by accommodating changes in pressure during the cardiac cycle. *Aorta* - The **aorta** is the primary vessel demonstrating the **Windkessel effect** due to its high elasticity and large diameter. - During systole, it stretches and stores a significant volume of blood, releasing it during diastole to maintain a continuous flow. *Abdominal* - The **abdominal aorta** is a large elastic artery that, like the thoracic aorta, is crucial for expressing the **Windkessel effect**. - Its elastic recoil during diastole helps to sustain blood flow to the lower body and abdominal organs.

Question 749: If the contractility of the heart is decreased, which of the following is seen ?

A. Increased ejection fraction
B. Increased stroke work
C. Decreased stroke volume (Correct Answer)
D. Increased cardiac output

Explanation: ***Decreased stroke volume*** - A decrease in the **contractility** of the heart directly reduces the force of myocardial contraction. - This weaker contraction results in less blood being ejected from the ventricle per beat, leading to a **decreased stroke volume**. *Increased ejection fraction* - **Ejection fraction** is the percentage of blood ejected from the ventricle with each beat, calculated as (stroke volume / end-diastolic volume) x 100. - When contractility decreases, **stroke volume** decreases, which would typically lead to a *decreased* ejection fraction, not an increased one. *Increased stroke work* - **Stroke work** is a measure of the work done by the ventricle to eject blood, and it depends on both stroke volume and aortic pressure. - With decreased contractility, **stroke volume** falls, which would *decrease* the stroke work, assuming afterload remains constant. *Increased cardiac output* - **Cardiac output** is the product of stroke volume and heart rate (CO = SV x HR). - Since decreased contractility leads to a **decreased stroke volume**, without a compensatory increase in heart rate, cardiac output would *decrease*, not increase.

Question 750: Which factor most strongly influences coronary blood flow during exercise?

A. Endothelin release
B. Metabolic demand (Correct Answer)
C. Myogenic response
D. Neural regulation
E. Baroreceptor reflex

Explanation: **Metabolic demand** - During exercise, increased **myocardial activity** leads to a higher demand for oxygen and nutrients, prompting a significant increase in coronary blood flow. - Local release of **metabolites** such as adenosine, nitric oxide, and hydrogen ions causes powerful vasodilation of coronary arteries, closely matching blood supply to demand. *Endothelin release* - **Endothelin** is a potent vasoconstrictor and plays a role in regulating vascular tone, but its primary influence is not the immediate or strongest factor dictating increased coronary flow during exercise. - While it can modulate flow, metabolic changes are the dominant driver for the rapid and substantial increases needed during exertion. *Myogenic response* - The **myogenic response** is an intrinsic property of vascular smooth muscle cells to contract when stretched (due to increased pressure) and relax when pressure decreases, helping to maintain relatively constant blood flow. - This mechanism primarily contributes to **autoregulation** and flow stability, but it does not account for the massive increase in flow required by the heart during exercise. *Neural regulation* - **Neural regulation**, primarily sympathetic stimulation, increases heart rate and contractility, which indirectly increases metabolic demand. - However, direct neural effects on coronary arteries can be complex (both vasodilation and vasoconstriction depending on receptor type), and the overriding control during exercise is typically metabolic.

Practice by Chapter

Cardiac Electrophysiology

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Cardiac Cycle

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Cardiac Output and Its Regulation

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Hemodynamics and Blood Flow

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Arterial System Physiology

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Microcirculation and Lymphatics

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Venous Return and Central Venous Pressure

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Cardiovascular Reflexes

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Regional Circulations

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Cardiovascular Responses to Exercise and Stress

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