Cardiovascular System — MCQs

Cardiovascular System Indian Medical PG Practice Questions and MCQs

Question 91: What is the formula for calculating ejection fraction?

A. Stroke Volume (SV) / End-Diastolic Volume (EDV) (Correct Answer)
B. End-Diastolic Volume (EDV) / Stroke Volume (SV)
C. End-Systolic Volume (ESV) / End-Diastolic Volume (EDV)
D. Stroke Volume (SV) / End-Diastolic Volume (EDV)

Explanation: **Explanation:** **Ejection Fraction (EF)** is a critical clinical index used to assess the pumping efficiency of the heart, specifically the ventricles. It represents the fraction of blood pumped out of the ventricle with each heartbeat relative to the total amount of blood available at the end of filling. **1. Why Option A is Correct:** The formula for EF is **Stroke Volume (SV) / End-Diastolic Volume (EDV)**. * **Stroke Volume (SV):** The volume of blood ejected per beat (EDV – ESV). * **End-Diastolic Volume (EDV):** The total volume of blood in the ventricle just before contraction. By dividing SV by EDV, we determine what percentage of the "full" ventricle was successfully ejected. It is usually expressed as a percentage (Normal range: 55%–70%). **2. Analysis of Incorrect Options:** * **Option B (EDV / SV):** This is the inverse of the correct formula and has no physiological significance. * **Option C (ESV / EDV):** This represents the "Residual Fraction"—the percentage of blood remaining in the heart after contraction. While mathematically related (EF = 1 - Residual Fraction), it is not the definition of Ejection Fraction. * **Option D:** (Duplicate of Option A). **3. Clinical Pearls for NEET-PG:** * **Gold Standard Measurement:** Transthoracic Echocardiography (ECHO) is the most common bedside tool, but **Cardiac MRI** is the gold standard for accurate volume assessment. * **Heart Failure Classification:** * **HFrEF (Reduced EF):** EF ≤ 40% (indicates systolic dysfunction). * **HFpEF (Preserved EF):** EF ≥ 50% (indicates diastolic dysfunction). * **Sympathetic Stimulation:** Increases contractility (Inotropy), which increases SV and subsequently increases the EF. * **Preload vs. Afterload:** EF is highly sensitive to afterload; an acute increase in systemic vascular resistance will decrease the EF.

Question 92: Which of the following is NOT true regarding endothelin-1?

A. Bronchodilatation (Correct Answer)
B. Vasoconstriction
C. Decreased GFR
D. Has inotropic effect

Explanation: **Explanation:** Endothelin-1 (ET-1) is a potent 21-amino acid peptide produced primarily by vascular endothelial cells. It acts as a powerful paracrine and autocrine mediator through two main receptors: $ET_A$ and $ET_B$. **Why Option A is the Correct Answer:** Endothelin-1 is a potent **bronchoconstrictor**, not a bronchodilator. It acts on $ET_A$ receptors located on bronchial smooth muscle, leading to airway narrowing. Elevated levels of ET-1 are often implicated in the pathophysiology of asthma and pulmonary hypertension. **Analysis of Incorrect Options:** * **B. Vasoconstriction:** This is the hallmark effect of ET-1. It is one of the most potent endogenous vasoconstrictors known (10 times more potent than Angiotensin II), acting via $ET_A$ receptors on vascular smooth muscle. * **C. Decreased GFR:** In the kidneys, ET-1 causes potent constriction of both afferent and efferent arterioles. This leads to a reduction in renal blood flow and a subsequent **decrease in Glomerular Filtration Rate (GFR)**. * **D. Inotropic effect:** ET-1 exerts a **positive inotropic effect** on the myocardium (increasing the force of contraction) and also possesses chronotropic properties, though its systemic vasoconstrictor effects usually dominate the clinical picture. **High-Yield Clinical Pearls for NEET-PG:** * **Stimulus for Release:** ET-1 release is stimulated by Thrombin, Epinephrine, Angiotensin II, and low shear stress. It is inhibited by Nitric Oxide (NO) and Prostacyclin. * **Receptor Specificity:** $ET_A$ receptors primarily mediate vasoconstriction and bronchoconstriction; $ET_B$ receptors (on endothelium) can stimulate NO release, causing transient vasodilation. * **Clinical Correlation:** **Bosentan** is a dual $ET_A/ET_B$ receptor antagonist used in the treatment of Pulmonary Arterial Hypertension (PAH).

Question 93: All of the following are true regarding ECG findings, except:

A. Heart block causes an increase in the PR interval.
B. The QRS wave represents ventricular repolarization. (Correct Answer)
C. The T wave represents ventricular repolarization.
D. Ventricular depolarization and repolarization occur during the QT interval.

Explanation: **Explanation:** The correct answer is **B** because it is a false statement. In a standard ECG, the **QRS complex represents ventricular depolarization**, not repolarization. Ventricular depolarization triggers the contraction of the ventricles. **Analysis of Options:** * **Option A (True):** The PR interval (normal: 0.12–0.20s) represents the time taken for the impulse to travel from the SA node to the ventricles. In first-degree heart block, there is a delay in AV conduction, leading to a **prolonged PR interval**. * **Option C (True):** The **T wave** is the electrical representation of **ventricular repolarization**, during which the ventricles recover and prepare for the next cycle. * **Option D (True):** The **QT interval** (from the start of the QRS to the end of the T wave) encompasses the entire period of ventricular electrical activity, including both **depolarization and repolarization**. **Clinical Pearls for NEET-PG:** 1. **Atrial Repolarization:** It occurs during the QRS complex but is not visible on a standard ECG because it is masked by the much larger electrical signal of ventricular depolarization. 2. **U Wave:** If present, it represents the repolarization of the **Purkinje fibers** or papillary muscles; it is most commonly seen in **hypokalemia**. 3. **ST Segment:** This represents the "plateau phase" (Phase 2) of the ventricular action potential. Elevation or depression is a critical marker for myocardial ischemia/infarction. 4. **QT Interval Rule:** A rough guide is that the QT interval should be less than half of the preceding R-R interval. Prolongation can predispose patients to *Torsades de Pointes*.

Question 94: Electromechanical systole is best defined as the interval between?

A. The Q wave and S2 (Q-S2 Interval) (Correct Answer)
B. The Q wave and SI (Q-Sl Interval)
C. The Q wave and the beginning of the T wave
D. The Q wave and the R wave

Explanation: ### Explanation **Electromechanical Systole (EMS)** represents the total duration of ventricular systole, encompassing both the electrical activation and the subsequent mechanical contraction of the heart. **1. Why Option A is Correct:** The **Q-S2 interval** is the standard measure for EMS. It begins at the onset of ventricular depolarization (the **Q wave** on the ECG) and ends with the closure of the semilunar valves (the **second heart sound, S2**), which marks the end of mechanical ejection. This interval accounts for: * **Pre-ejection period (PEP):** Electrical onset to the opening of the aortic valve. * **Left Ventricular Ejection Time (LVET):** Opening to the closure of the aortic valve. **2. Why the Other Options are Incorrect:** * **Option B (Q-S1 Interval):** This represents the **Electromechanical Delay**. It is the time between electrical depolarization and the closure of the AV valves (S1). It only covers the very beginning of systole. * **Option C (Q to beginning of T wave):** This is purely an electrical measurement. While the T wave represents repolarization, mechanical systole continues until the end of the T wave (S2 occurs at the end of the T wave). * **Option D (Q to R wave):** This is merely a component of the QRS complex, representing the initial phase of ventricular depolarization, not the mechanical function. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Systolic Time Intervals (STI):** EMS is a sensitive indicator of left ventricular performance. * **Effect of Heart Rate:** The Q-S2 interval is inversely proportional to heart rate (it shortens as heart rate increases). * **Heart Failure:** In conditions like heart failure, the PEP (Pre-ejection period) increases while the LVET (Ejection time) decreases, though the total EMS may remain relatively constant or shorten. * **S2 Timing:** Remember that S2 occurs at the **end of the T wave** on an ECG, signifying the end of mechanical systole.

Question 95: Which of the following statements is not true regarding the measurement of blood pressure?

A. The cuff length should be 80% and the width should be 40% of the mid-arm circumference.
B. Diastolic pressure is indicated by the disappearance of Korotkoff sounds. (Correct Answer)
C. Using a cuff that is too small will result in a falsely high blood pressure reading.
D. The cuff should be tied at the level of the heart.

Explanation: **Explanation** The measurement of blood pressure via the auscultatory method relies on identifying **Korotkoff sounds**, which are produced by turbulent blood flow. **Why Option B is the "Not True" statement:** While the disappearance of sounds (Phase V) is commonly used in clinical practice to denote diastolic blood pressure (DBP) in adults, the **gold standard** for DBP—especially in physiological terms and specific populations (like children, pregnant women, or patients with high cardiac output)—is actually the **muffling of sounds (Phase IV)**. In many individuals, sounds may persist down to 0 mmHg; therefore, Phase IV is the more consistent physiological indicator of the transition from turbulent to laminar flow. **Analysis of other options:** * **Option A:** This follows the standard AHA guidelines. For accurate pressure transmission, the bladder length should encircle 80% and the width should be 40% of the arm circumference. * **Option C:** A cuff that is too small (narrow) requires more pressure to occlude the artery, leading to a **falsely high** reading (Cuff Hypertension). Conversely, a cuff that is too large gives a falsely low reading. * **Option D:** The cuff must be at heart level to eliminate the effects of **hydrostatic pressure**. If the arm is below heart level, the BP will be falsely elevated. **High-Yield Clinical Pearls for NEET-PG:** * **Phase I:** First clear tapping sound (Systolic BP). * **Phase IV:** Muffling of sounds (True Diastolic BP). * **Phase V:** Disappearance of sounds (Clinical Diastolic BP). * **Auscultatory Gap:** A silent interval between Phase I and II, often seen in hypertensive patients; failure to recognize it leads to underestimating SBP.

Question 96: Which of the following proteins inhibits heme loss from plasma?

A. Ferritin
B. Hemopexin (Correct Answer)
C. Ceruloplasmin
D. Hemosiderin

Explanation: **Explanation:** The correct answer is **Hemopexin**. **1. Why Hemopexin is correct:** Hemopexin is a plasma glycoprotein synthesized by the liver with the highest known affinity for **heme**. When intravascular hemolysis occurs, hemoglobin is released and quickly dissociates into globin and heme. While **Haptoglobin** binds to free hemoglobin, **Hemopexin** specifically binds to the free heme (ferriheme). This binding prevents heme-mediated oxidative damage to tissues and, crucially, prevents the loss of iron via urinary excretion. The heme-hemopexin complex is then transported to the liver, where it is internalized via receptor-mediated endocytosis (CD91 receptor). **2. Why the other options are incorrect:** * **Ferritin:** This is the primary **intracellular** storage form of iron found in the liver, spleen, and bone marrow. While small amounts circulate in the plasma (reflecting total body iron stores), its role is storage, not heme transport. * **Ceruloplasmin:** This is a ferroxidase enzyme containing copper. Its primary role is to oxidize ferrous iron ($Fe^{2+}$) to ferric iron ($Fe^{3+}$) so it can bind to transferrin. It does not bind heme. * **Hemosiderin:** This is an insoluble iron-storage complex, usually derived from the partial digestion of ferritin. It is found within cells (macrophages) during states of iron overload, not as a plasma transport protein. **Clinical Pearls for NEET-PG:** * **Haptoglobin vs. Hemopexin:** Haptoglobin is the first line of defense (binds Hb). Once haptoglobin is saturated, free heme is released and bound by Hemopexin. * **Hemolysis Marker:** Low serum levels of Haptoglobin and Hemopexin are diagnostic markers for **intravascular hemolysis**. * **Transferrin:** Remember that Transferrin transports **ionic iron**, not heme or hemoglobin.

Question 97: The P2 sound is best appreciated in which of the following locations?

A. 2nd left intercostal space (Correct Answer)
B. 2nd right intercostal space
C. 4th left intercostal space
D. 5th left intercostal space

Explanation: **Explanation:** The second heart sound (S2) is produced by the closure of the semilunar valves (Aortic and Pulmonary) at the beginning of ventricular diastole. It consists of two components: **A2** (Aortic valve closure) and **P2** (Pulmonary valve closure). **Why Option A is Correct:** The **Pulmonary Area** is located at the **2nd left intercostal space (ICS)**, just lateral to the sternal border. Because the pulmonary artery is closest to the chest wall at this specific anatomical location, the vibrations produced by the closure of the pulmonary valve (P2) are best transmitted and auscultated here. **Analysis of Incorrect Options:** * **Option B (2nd right ICS):** This is the **Aortic Area**. While S2 is heard here, it is primarily the A2 component. * **Option C (4th left ICS):** This is the **Tricuspid Area** (lower left sternal border), where the S1 sound and tricuspid murmurs are best appreciated. * **Option D (5th left ICS):** This is the **Mitral Area** (apex), located in the mid-clavicular line. It is the best site for hearing S1 and mitral valve sounds. **High-Yield Clinical Pearls for NEET-PG:** * **Physiological Splitting:** During inspiration, P2 is delayed due to increased venous return to the right heart, causing S2 to split into A2 and P2. * **P2 Intensity:** A loud or palpable P2 at the 2nd left ICS is a classic clinical sign of **Pulmonary Hypertension**. * **Order of Closure:** Under normal conditions, A2 precedes P2 because the systemic resistance is higher than pulmonary resistance, causing the aortic valve to close slightly earlier.

Question 98: What is the most common non-cardiac peripheral factor that leads to decreased cardiac output?

A. Decreased blood volume (Correct Answer)
B. Acute venous dilation
C. Obstruction of the large veins
D. Decreased tissue mass, especially decreased skeletal muscle mass

Explanation: **Explanation:** Cardiac output (CO) is determined by the product of Heart Rate and Stroke Volume. From a peripheral standpoint, CO is governed by **Venous Return (VR)**. According to the Frank-Starling law, the heart pumps whatever volume of blood flows into it from the veins. **1. Why Decreased Blood Volume is Correct:** Decreased blood volume (hemorrhage or dehydration) is the **most common** peripheral factor leading to low CO. A reduction in blood volume decreases the **Mean Systemic Filling Pressure (MSFP)**—the pressure that pushes blood toward the heart. When MSFP drops, the pressure gradient for venous return falls, leading to decreased end-diastolic volume, reduced stroke volume, and ultimately, a fall in cardiac output. **2. Analysis of Incorrect Options:** * **Acute Venous Dilation (B):** This increases the vascular capacity (venous pooling), which decreases MSFP and VR. While a valid cause, it is clinically less common than simple hypovolemia. * **Obstruction of Large Veins (C):** Obstruction (e.g., IVC syndrome) increases resistance to venous return. While it reduces CO, it is a localized pathological event rather than the "most common" factor. * **Decreased Tissue/Muscle Mass (D):** This occurs in aging or prolonged bed rest. It reduces the metabolic demand and the size of the vascular bed, leading to a lower CO, but it is a chronic physiological adaptation rather than an acute clinical cause of decreased output. **Clinical Pearls for NEET-PG:** * **MSFP:** The normal value is **7 mmHg**. It is the primary determinant of venous return. * **Venous Return Curve:** A decrease in blood volume shifts the venous return curve to the **left and downward**. * **The "Gold Standard":** In clinical practice, the most common cause of "Shock" (low CO leading to tissue hypoxia) is **Hypovolemic Shock**.

Question 99: Which of the following increases turbulence in blood flow?

A. Reynolds number < 2000
B. Decrease in velocity of blood
C. Decrease in density of blood
D. Increase in diameter of blood vessel (Correct Answer)

Explanation: The tendency for blood flow to become turbulent is determined by the **Reynolds number (Re)**. This dimensionless value is calculated using the formula: $$Re = \frac{\rho \cdot d \cdot v}{\eta}$$ *(Where $\rho$ = density, $d$ = diameter, $v$ = velocity, and $\eta$ = viscosity)* ### Why Option D is Correct According to the formula, the Reynolds number is **directly proportional** to the diameter of the vessel. As the diameter increases, the Reynolds number increases. When $Re$ exceeds a critical threshold (typically >2000–3000), laminar flow transitions into turbulent flow, characterized by eddies and whorls. This is why turbulence is commonly seen in large vessels like the **ascending aorta**. ### Explanation of Incorrect Options * **A. Reynolds number < 2000:** At values below 2000, blood flow is typically **laminar** (smooth and streamlined). Turbulence generally begins when $Re$ exceeds 2000 and becomes significant above 3000. * **B. Decrease in velocity:** Velocity is directly proportional to $Re$. A decrease in velocity reduces the kinetic energy of the blood, making it more likely to remain laminar. * **C. Decrease in density:** Density is directly proportional to $Re$. A decrease in density (though rare in clinical scenarios) would mathematically decrease the Reynolds number and reduce turbulence. ### NEET-PG High-Yield Pearls * **Anemia & Turbulence:** In anemia, blood viscosity ($\eta$) decreases. Since viscosity is in the denominator, a decrease in viscosity **increases** the Reynolds number, explaining why "hemic murmurs" (turbulent flow) are heard in anemic patients. * **Bruits and Murmurs:** Turbulent flow is clinically significant because it generates sound. In peripheral arteries, this is called a **bruit**; in the heart, it is a **murmur**. * **Most common site of turbulence:** The root of the aorta and the pulmonary artery during ejection, due to high velocity and large diameter.

Question 100: When a person changes position from standing to lying down, which of the following changes is observed?

A. Heart rate increases
B. Venous return to the heart increases immediately (Correct Answer)
C. Cerebral blood flow increases
D. Blood flow at the apices of the lungs decreases

Explanation: ### Explanation **1. Why Option B is Correct:** When a person moves from a standing to a lying (supine) position, the effect of gravity on the column of blood is abolished. In the standing position, approximately 500–800 mL of blood pools in the lower extremities due to gravity. Upon lying down, this pooled blood is displaced centrally toward the heart. This results in an **immediate increase in venous return**, which increases the central venous pressure (CVP) and right ventricular end-diastolic volume (Preload). According to the **Frank-Starling Law**, this increased preload leads to an increase in stroke volume. **2. Why the Other Options are Incorrect:** * **Option A:** Heart rate actually **decreases**. The sudden increase in venous return and stroke volume raises the mean arterial pressure. This stimulates the **baroreceptors** (carotid sinus and aortic arch), leading to increased vagal tone and a compensatory decrease in heart rate (the Baroreceptor Reflex). * **Option C:** Cerebral blood flow remains **constant**. Due to powerful **autoregulation** mechanisms, cerebral blood flow is maintained at a steady rate (approx. 50 mL/100g/min) despite changes in posture or systemic blood pressure (within the range of 60–160 mmHg). * **Option D:** Blood flow at the apices **increases**. In the standing position, the apices are poorly perfused due to gravity (Zone 1/2 of West). In the supine position, the lungs are at the same horizontal level as the heart, leading to a more uniform distribution of blood flow and increased perfusion to the apices. **3. High-Yield NEET-PG Pearls:** * **Bainbridge Reflex:** An increase in venous return can sometimes trigger an increase in heart rate to prevent "clogging" of the heart; however, in a healthy human changing posture, the **Baroreceptor Reflex** usually dominates, resulting in a net decrease in heart rate. * **Orthostatic Hypotension:** Defined as a drop in systolic BP >20 mmHg or diastolic BP >10 mmHg within 3 minutes of standing. * **ANP Release:** The stretch of the atria due to increased venous return in the supine position leads to the release of **Atrial Natriuretic Peptide (ANP)**, promoting diuresis.

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