Cardiovascular System Practice Questions

Q: Which ECG finding is indicative of hypercalcemia?

Decreased QT interval. **Explanation:** The correct answer is **Decreased QT interval**. **Mechanism:** The QT interval represents the total duration of ventricular depolarization and repolarization. In **hypercalcemia**, the increased extracellular calcium concentration shortens the Phase 2 (plateau phase) of the cardiac action potential. This occurs because the increased calcium gradient leads to faster calcium influx, which triggers an earlier activation of outward potassium channels, thereby accelerating repolarization. This shortened action potential duration manifests on the ECG as a **shortened QT interval**. **Analysis of Incorrect Options:** * **A. Increased QT interval:** This is a hallmark of **hypocalcemia**. Low calcium levels prolong Phase 2 of the action potential, leading to a lengthened QT interval, which increases the risk of Torsades de Pointes [1]. * **C. Increased PR interval:** While severe hypercalcemia can occasionally cause PR prolongation or heart blocks, it is not the classic or most diagnostic finding. PR prolongation is more typically associated with **hyperkalemia** or drugs like Beta-blockers and Digoxin [2]. * **D. Tall T waves:** "Tall, peaked T waves" are the classic early ECG sign of **hyperkalemia** [2]. In hypercalcemia, T waves are usually normal, though they may appear to "start" immediately after the QRS complex due to the absent ST segment. **High-Yield NEET-PG Pearls:** * **Hypercalcemia Mnemonic:** "Short QT, Short ST." In severe cases, you may also see **Osborn waves** (J waves), though these are more classic for hypothermia. * **Hypocalcemia Mnemonic:** "Long QT" (specifically a prolonged ST segment) [1]. * **Digoxin Effect:** Also causes a shortened QT interval but is distinguished by the "reverse tick" or "sagging" ST-segment depression.

Q: Which heart sound is almost pathological?

S4. **Explanation:** The correct answer is **S4 (Fourth Heart Sound)**. **1. Why S4 is the correct answer:** The S4, also known as the "atrial gallop," occurs during late diastole (active ventricular filling) when the atria contract against a **stiff, non-compliant ventricle**. While S4 can occasionally be heard in elderly individuals or elite athletes due to physiological hypertrophy, it is **almost always pathological** in clinical practice. It signifies decreased ventricular compliance, commonly seen in conditions like Left Ventricular Hypertrophy (LVH) due to systemic hypertension, aortic stenosis, or acute myocardial infarction. **2. Why the other options are incorrect:** * **S1 (First Heart Sound):** This is a **physiological** sound caused by the closure of the Atrioventricular (Mitral and Tricuspid) valves at the beginning of systole. * **S2 (Second Heart Sound):** This is a **physiological** sound caused by the closure of the Semilunar (Aortic and Pulmonary) valves at the beginning of diastole. * **S3 (Third Heart Sound):** While S3 can be pathological (ventricular gallop in heart failure), it is frequently **physiological** in children, young adults (under 40), and during pregnancy due to rapid ventricular filling. Therefore, it is not "almost always" pathological like S4. **3. High-Yield NEET-PG Pearls:** * **S4 Timing:** Occurs just before S1 (Presystolic). * **Best heard:** At the apex with the bell of the stethoscope in the left lateral decubitus position. * **The "Tennessee" Cadence:** S4-S1-S2. * **Rule of Thumb:** S4 is **never** heard in Atrial Fibrillation because atrial contraction is required to produce the sound. * **S3 vs. S4:** S3 = Volume overload (e.g., Dilated Cardiomyopathy); S4 = Pressure overload/Stiffness (e.g., Concentric Hypertrophy).

Q: All of the following favor filtration at the arteriolar end of the capillary bed, EXCEPT:

Negative net filtration pressure (NFP). ### Explanation The movement of fluid across a capillary membrane is governed by **Starling’s Forces**. The Net Filtration Pressure (NFP) determines whether fluid moves out of the capillary (filtration) or into the capillary (reabsorption). The formula for NFP is: **NFP = (Pc - Pi) - (πc - πi)** *(Where P = Hydrostatic Pressure, π = Oncotic/Osmotic Pressure, c = capillary, i = interstitial fluid)* **1. Why Option D is the Correct Answer:** A **Negative NFP** indicates that the forces favoring reabsorption (primarily capillary oncotic pressure) exceed the forces favoring filtration. This occurs at the **venular end** of the capillary, where fluid is pulled back into the vessel. Therefore, it does **not** favor filtration. **2. Analysis of Incorrect Options:** * **Option A:** An **increase in capillary hydrostatic pressure (Pc)** directly increases the outward force, pushing fluid into the interstitium, thus favoring filtration. * **Option B:** Filtration occurs when the **hydrostatic pressure gradient (Pc - Pi)** is greater than the **osmotic pressure gradient (πc - πi)**. This is the physiological state at the arteriolar end. * **Option C:** A **Positive NFP** means the sum of outward forces is greater than inward forces, which is the definition of filtration. **3. NEET-PG High-Yield Pearls:** * **Arteriolar End:** Hydrostatic pressure (~35 mmHg) > Oncotic pressure (~25 mmHg) → **Filtration.** * **Venular End:** Hydrostatic pressure (~15 mmHg) < Oncotic pressure (~25 mmHg) → **Reabsorption.** * **Edema Pathophysiology:** Edema is caused by factors favoring filtration: increased Pc (Heart Failure), decreased πc (Nephrotic syndrome/Hypoproteinemia), or increased capillary permeability (Inflammation). * **Lymphatics:** Not all filtered fluid is reabsorbed at the venular end; the excess (~2-4 L/day) is returned to circulation via the lymphatic system.

Q: In an isolated muscle piece fiber, repolarization proceeds from which layer to which layer?

Endocardium to epicardium. ### Explanation The direction of electrical activity in the heart depends on whether we are looking at an **intact heart in situ** or an **isolated muscle fiber**. **1. Why Option B is Correct:** In an **isolated muscle fiber** (or a simple strip of cardiac muscle), the sequence of repolarization follows the sequence of depolarization. The first cell to depolarize is the first to recover. Since depolarization spreads from the endocardium to the epicardium, repolarization naturally follows the same path: **Endocardium to Epicardium**. In this scenario, the action potential duration (APD) is uniform across all cells. **2. Why Other Options are Incorrect:** * **Option A (Epicardium to Endocardium):** This is the direction of repolarization in the **intact living heart**. In a whole heart, the epicardial cells have a shorter APD due to a higher density of transient outward potassium currents ($I_{to}$). Additionally, high sub-endocardial pressure during systole delays endocardial recovery. Thus, the epicardium repolarizes first. * **Options C & D:** These refer to lateral conduction across the septum or walls, which is relevant for depolarization (e.g., septal depolarization from left to right), but not the standard transmural sequence of repolarization. **3. High-Yield Clinical Pearls for NEET-PG:** * **The "Rule of Opposites":** In an isolated fiber, the T-wave would be inverted (opposite to QRS) because repolarization moves in the same direction as depolarization. * **The Normal ECG:** In a healthy intact heart, the T-wave is **upright** (concordant with QRS) because repolarization moves in the **opposite direction** (Epicardium $\rightarrow$ Endocardium) to depolarization. * **Ventricular Gradient:** The difference in APD between the endocardium and epicardium is what prevents T-wave inversion in a normal ECG.

Q: The pressure-volume curve is shifted to the left in which of the following conditions?

Aortic stenosis. **Explanation:** The **Pressure-Volume (PV) loop** represents the relationship between left ventricular (LV) pressure and volume during a single cardiac cycle. A **shift to the left** indicates a decrease in ventricular volumes (specifically End-Diastolic Volume and End-Systolic Volume). **Why Aortic Stenosis is Correct:** In **Aortic Stenosis (AS)**, the left ventricle must overcome high resistance to eject blood through a narrowed valve. This leads to **concentric LV hypertrophy**, which reduces ventricular compliance and decreases the internal chamber size. Consequently, the PV loop shifts to the left and upward (due to significantly higher systolic pressures). **Analysis of Incorrect Options:** * **Mitral Regurgitation (MR):** This causes volume overload. The LV receives blood from both the pulmonary veins and the regurgitant volume from the previous cycle, leading to eccentric hypertrophy and a **shift to the right**. * **Aortic Regurgitation (AR):** This is the classic example of extreme volume overload. The LV must accommodate the stroke volume plus the blood leaking back from the aorta, causing massive dilation (bovine heart) and a significant **shift to the right**. * **Mitral Stenosis (MS):** In MS, LV filling is impaired. While this reduces volumes, it does not typically cause the compensatory structural "shift" seen in pressure-overload states like AS. The loop simply becomes smaller. **High-Yield NEET-PG Pearls:** * **Shift to the Right:** Seen in Volume Overload (AR, MR, Dilated Cardiomyopathy). * **Shift to the Left:** Seen in Pressure Overload/Reduced Compliance (AS, Hypertension, Hypertrophic Cardiomyopathy). * **Width of the Loop:** Represents Stroke Volume (SV). SV is increased in AR and decreased in Heart Failure. * **Area of the Loop:** Represents Stroke Work. This is highest in Aortic Stenosis due to the extreme pressures required for ejection.

Question 1

Which ECG finding is indicative of hypercalcemia?

Accepted Answer

Decreased QT interval

Answer

Increased QT interval

Answer

Increased PR interval

Answer

Tall T waves

Question 2

Which heart sound is almost pathological?

Accepted Answer

S4

Answer

S1

Answer

S2

Answer

S3

Question 3

Cardiac output is not affected by which of the following factors?

Accepted Answer

Systolic blood pressure

Answer

Heart rate

Answer

Peripheral resistance

Answer

Venous return

Question 4

What physiological changes are expected when the carotid sinus is digitally compressed?

Accepted Answer

Heart rate and peripheral resistance decrease

Answer

Heart rate decreases, peripheral resistance increases

Answer

Peripheral resistance and contractility decrease

Answer

Peripheral resistance and contractility increase

Question 5

All of the following favor filtration at the arteriolar end of the capillary bed, EXCEPT:

Accepted Answer

Negative net filtration pressure (NFP)

Answer

Increase in hydrostatic pressure of capillaries

Answer

Hydrostatic pressure gradient more than osmotic pressure gradient

Answer

Positive net filtration pressure (PFP)

Question 6

A physician monitoring a newborn infant's heart sounds using a stethoscope hears the characteristic murmur of a patent ductus arteriosus. How soon after birth should this murmur normally disappear?

Accepted Answer

Immediate closure

Answer

1-2 months

Answer

1-2 weeks

Answer

1-2 days

Question 7

In an isolated muscle piece fiber, repolarization proceeds from which layer to which layer?

Accepted Answer

Endocardium to epicardium

Answer

Epicardium to endocardium

Answer

Left to right

Answer

Right to left

Question 8

The pressure-volume curve is shifted to the left in which of the following conditions?

Accepted Answer

Aortic stenosis

Answer

Mitral regurgitation

Answer

Aortic regurgitation

Answer

Mitral stenosis

Question 9

What is the reception for the Bezold-Jarisch reflex?

Accepted Answer

Terminal ends of C fibers

Answer

Stretch receptors

Answer

Mechanical receptors

Answer

All of the above

Question 10

Vagal stimulation decreases heart rate by?

Accepted Answer

Decrease in the slope of prepotential

Answer

Decrease in action potential amplitude

Answer

Increase in repolarization phase duration

Answer

Decrease in conduction velocity

Cardiovascular System — MCQs

Cardiovascular System — MCQs

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