CVS Most Important Viva Questions

A: The heart has four chambers, valves and a thick muscular wall called myocardium. Its main function is not only to hold blood but to actively pump it through pulmonary and systemic circulation by rhythmic contraction.

Q2. Why is the left ventricle thicker than the right ventricle?

A: The left ventricle pumps blood to the whole body against high systemic resistance. The right ventricle pumps blood only to the lungs, where vascular resistance is much lower, so its wall is thinner.

Q3. How does the structure of cardiac muscle support continuous heart function?

A: Cardiac muscle fibers are branched, striated and connected by intercalated discs. These connections allow rapid spread of electrical impulses, so the myocardium contracts as a coordinated unit.

Q4. Why are intercalated discs important in cardiac muscle?

A: Intercalated discs provide mechanical attachment and electrical communication between cardiac muscle cells. This allows the heart muscle to contract forcefully and synchronously instead of as separate isolated cells.

Q5. Why are valves essential for normal cardiac function?

A: Valves ensure one-way flow of blood through the heart. Without proper valve function, blood may flow backward, reducing effective pumping and increasing workload on the heart.

Q6. Why do papillary muscles and chordae tendineae support atrioventricular valves?

A: During ventricular systole, pressure rises inside the ventricles. Papillary muscles and chordae tendineae prevent mitral and tricuspid valve cusps from prolapsing back into the atria.

Topic 2 — Coronary Circulation and Pericardium

Q7. Why does the myocardium need coronary arteries if blood is already present inside the heart chambers?

A: Blood inside the chambers cannot adequately nourish the thick myocardium. Coronary arteries supply oxygen and nutrients directly to cardiac muscle cells, which have very high metabolic demand.

Q8. Why does most coronary blood flow to the left ventricle occur during diastole?

A: During systole, the contracting left ventricle compresses coronary vessels within the myocardium. In diastole, the muscle relaxes, allowing coronary vessels to open and receive blood flow.

Q9. Why is blockage of a coronary artery dangerous?

A: A coronary artery supplies oxygen to a specific area of myocardium. If it becomes blocked, that area becomes ischemic and may undergo necrosis, resulting in myocardial infarction.

Q10. How does the pericardium help normal heart function?

A: The pericardium protects the heart, anchors it in the mediastinum and reduces friction during beating. Its fluid-filled serous cavity allows the heart to move smoothly.

Q11. Why can pericardial fluid accumulation reduce cardiac output?

A: Excess fluid in the pericardial cavity compresses the heart because the fibrous pericardium is not very stretchable. This reduces ventricular filling and therefore reduces stroke volume and cardiac output.

Topic 3 — Coronary Artery Disease, Lipids and Cardiac Biomarkers

Q12. How does atherosclerosis lead to coronary artery disease?

A: Atherosclerosis causes lipid-rich plaque formation in arterial walls. In coronary arteries, this narrows the lumen, reduces blood flow to myocardium and may cause angina or myocardial infarction.

Q13. What is the difference between angina and myocardial infarction?

A: Angina is chest pain due to temporary myocardial ischemia without permanent cell death. Myocardial infarction occurs when ischemia is prolonged enough to cause death of cardiac muscle cells.

Q14. Why is LDL considered harmful in cardiovascular disease?

A: LDL carries cholesterol to tissues and can deposit cholesterol in arterial walls. High LDL favors plaque formation and increases the risk of atherosclerosis and coronary artery disease.

Q15. Why is HDL considered protective?

A: HDL helps remove excess cholesterol from tissues and transports it back to the liver. This reverse cholesterol transport lowers the tendency for cholesterol deposition in arteries.

Q16. Why are cardiac troponins important in suspected myocardial infarction?

A: Troponins are proteins found in cardiac muscle cells. When myocardial cells are damaged, troponins are released into the blood, making them useful markers of myocardial injury.

Q17. Why can pain from the heart be felt in the left arm or jaw?

A: Cardiac pain fibers enter spinal cord segments that also receive sensory input from the left arm, shoulder or jaw. The brain may interpret the pain as coming from these areas, producing referred pain.

Theme 2 — Breathlessness and Ankle Swelling

Topic 4 — Fetal Circulation, Congenital Heart Disease and Postnatal Circulatory Changes

Q18. Why does fetal circulation need special shunts?

A: In the fetus, lungs are not used for gas exchange because oxygen comes from the placenta. Special shunts divert much of the blood away from the lungs and liver to maintain efficient fetal circulation.

Q19. What is the functional importance of the foramen ovale?

A: The foramen ovale allows blood to pass from the right atrium to the left atrium. This helps bypass the non-functioning fetal lungs and directs oxygenated blood toward systemic circulation.

Q20. What is the functional importance of the ductus arteriosus?

A: The ductus arteriosus connects the pulmonary trunk to the aorta. It allows blood to bypass the fetal lungs, where pulmonary vascular resistance is high before birth.

Q21. What major circulatory changes occur after birth?

A: After birth, lung expansion lowers pulmonary vascular resistance, while removal of the placenta increases systemic vascular resistance. These pressure changes help close fetal shunts and establish adult circulation.

Q22. Why does a ventricular septal defect usually cause a left-to-right shunt?

A: Left ventricular pressure is normally higher than right ventricular pressure. Therefore, blood tends to move from left ventricle to right ventricle through the defect.

Q23. Why can congenital heart disease cause cyanosis?

A: Cyanosis occurs when deoxygenated blood enters systemic circulation. This happens in right-to-left shunts or complex defects where oxygenated and deoxygenated blood mix.

Topic 5 — Cardiac Cycle, Heart Valves and Heart Sounds

Q24. How do pressure changes control valve opening and closure?

A: Heart valves open and close according to pressure differences. Atrioventricular valves close when ventricular pressure exceeds atrial pressure, while semilunar valves open when ventricular pressure exceeds arterial pressure.

Q25. Why is diastole important for the heart?

A: Diastole allows ventricles to relax and fill with blood. It is also the main period for left coronary blood flow, so adequate diastole is important for both filling and myocardial oxygen supply.

Q26. Why does the first heart sound occur?

A: The first heart sound occurs due to closure of the mitral and tricuspid valves at the beginning of ventricular systole. It marks the start of ventricular contraction.

Q27. Why does the second heart sound occur?

A: The second heart sound occurs due to closure of the aortic and pulmonary valves at the end of ventricular systole. It marks the beginning of ventricular diastole.

Q28. Why are heart sounds clinically useful?

A: Heart sounds give information about valve closure and timing of the cardiac cycle. Abnormal sounds or murmurs may suggest valve disease, abnormal flow or structural heart problems.

Topic 6 — Cardiac Output, Venous Return and Heart Failure

Q29. What is the relationship between stroke volume, heart rate and cardiac output?

A: Cardiac output is the volume pumped by one ventricle per minute. It depends on stroke volume and heart rate, so an increase in either can increase cardiac output.

Q30. Why is venous return important for cardiac output?

A: Venous return determines how much blood enters the heart. According to the Frank-Starling mechanism, increased venous return stretches the myocardium and increases force of contraction up to a limit.

Q31. Explain the Frank-Starling law in simple words.

A: The more the ventricle fills during diastole, the more forcefully it contracts during systole, within physiological limits. This helps the heart pump the blood it receives.

Q32. How do preload, afterload and contractility affect cardiac output?

A: Preload affects ventricular filling, afterload is the resistance against ejection and contractility is the strength of contraction. Cardiac output depends on proper balance between these factors.

Q33. Why does left heart failure cause breathlessness?

A: In left heart failure, the left ventricle cannot pump blood effectively into systemic circulation. Blood backs up into the lungs, causing pulmonary congestion and breathlessness.

Q34. Why does right heart failure cause ankle swelling?

A: In right heart failure, blood backs up into systemic veins. This increases venous and capillary pressure, causing fluid to collect in dependent areas such as the ankles.

Topic 7 — Blood Flow, Capillary Exchange, Lymphatics and Edema

Q35. Why are arterioles called resistance vessels?

A: Arterioles have smooth muscle and can change their diameter. Small changes in arteriolar radius produce large changes in resistance and control blood flow to tissues.

Q36. Why does vessel radius strongly affect blood flow?

A: Blood flow depends greatly on vessel radius. When radius increases, resistance falls markedly and flow increases; when radius decreases, resistance rises and flow decreases.

Q37. How does capillary structure help exchange?

A: Capillaries have very thin endothelial walls and slow blood flow. This allows efficient exchange of oxygen, carbon dioxide, nutrients, waste products and fluid between blood and tissues.

Q38. How do hydrostatic and oncotic pressures affect capillary fluid movement?

A: Capillary hydrostatic pressure pushes fluid out of capillaries, while plasma oncotic pressure pulls fluid back in. The balance between these forces determines filtration and reabsorption.

Q39. Why does low plasma albumin cause edema?

A: Albumin maintains plasma oncotic pressure. When albumin is low, less fluid returns to capillaries, so fluid remains in tissues and causes edema.

Q40. Why are lymphatics important in preventing edema?

A: Lymphatics return excess interstitial fluid and proteins to the bloodstream. If lymphatic drainage is blocked, fluid accumulates in tissues and causes edema.

Theme 3 — Blood Pressure

Topic 8 — Blood Vessels: Histology, Development and Congenital Abnormalities

Q41. How can an artery and a vein be differentiated histologically?

A: Arteries have thicker walls, prominent tunica media and smaller rounded lumens because they carry blood under pressure. Veins have thinner walls, wider irregular lumens and often valves.

Q42. Why is tunica media well developed in arteries?

A: Arteries must withstand high pressure and regulate blood flow. A thick tunica media with smooth muscle and elastic tissue helps them constrict, dilate and maintain pressure.

Q43. Why do elastic arteries like the aorta contain many elastic fibers?

A: Elastic arteries stretch during systole and recoil during diastole. This elastic recoil maintains continuous blood flow and helps smooth out pressure changes from each heartbeat.

Q44. Why are veins called capacitance vessels?

A: Veins can hold a large volume of blood because they have thin walls and high compliance. They act as blood reservoirs and help regulate venous return to the heart.

Q45. Why can congenital abnormalities of blood vessels affect circulation?

A: Abnormal development of vessels can change blood flow pathways, pressure relationships or oxygen delivery. This may lead to shunts, obstruction or abnormal workload on the heart.

Topic 9 — Blood Pressure Regulation and Hypertension

Q46. What are the main determinants of arterial blood pressure?

A: Arterial blood pressure mainly depends on cardiac output and total peripheral resistance. Changes in heart pumping or arteriolar resistance can therefore alter blood pressure.

Q47. Why is mean arterial pressure important?

A: Mean arterial pressure represents the average pressure driving blood through tissues. It is more important for organ perfusion than systolic pressure alone.

Q48. How does the baroreceptor reflex respond to a sudden fall in blood pressure?

A: A fall in blood pressure decreases baroreceptor firing from the carotid sinus and aortic arch. This increases sympathetic activity, raising heart rate, contractility and vasoconstriction.

Q49. Why are kidneys important in long-term blood pressure control?

A: Kidneys regulate salt and water balance, which controls blood volume. Increased blood volume raises venous return and cardiac output, contributing to higher blood pressure.

Q50. Why is hypertension harmful even if the patient has no symptoms?

A: Hypertension silently increases afterload and damages blood vessels over time. It increases risk of left ventricular hypertrophy, stroke, kidney disease, heart failure and atherosclerosis.

Topic 10 — Circulatory Shock: Types, Stages and Physiological Basis of Treatment

Q51. What is the basic physiological problem in shock?

A: Shock is inadequate tissue perfusion leading to cellular hypoxia. The main issue is not only low blood pressure but failure to deliver enough oxygen and nutrients to tissues.

Q52. How does hypovolemic shock reduce cardiac output?

A: Loss of blood or fluid reduces venous return. Reduced venous return lowers preload, stroke volume and cardiac output, causing poor tissue perfusion.

Q53. Why does cardiogenic shock occur even when blood volume is normal?

A: In cardiogenic shock, the heart fails as a pump, commonly due to severe myocardial damage. Even with normal blood volume, the heart cannot eject enough blood to maintain perfusion.

Q54. Why does septic shock cause warm skin early but poor perfusion later?

A: Early septic shock causes widespread vasodilation, so skin may feel warm. Later, capillary leakage, poor cardiac function and maldistribution of blood flow cause severe tissue hypoxia.

Q55. What is the physiological basis of fluid therapy in hypovolemic shock?

A: Fluid therapy increases circulating blood volume, improves venous return and raises stroke volume. This helps restore cardiac output and tissue perfusion.

Theme 4 — Palpitations

Topic 11 — Cardiac Conduction System and Functional Organization of the Heart

Q56. Why is the SA node called the natural pacemaker?

A: The SA node has the fastest spontaneous depolarization among cardiac conducting tissues. Therefore, it normally initiates each heartbeat and controls the rhythm of the heart.

Q57. Why is AV nodal delay important?

A: AV nodal delay allows the atria to contract and empty blood into the ventricles before ventricular systole begins. This improves ventricular filling and pumping efficiency.

Q58. How does the conduction system produce coordinated ventricular contraction?

A: Impulses pass from the AV node to the bundle of His, bundle branches and Purkinje fibers. This rapidly spreads excitation through ventricles, allowing coordinated contraction.

Q59. Why is the heart called a functional syncytium?

A: Cardiac cells are connected electrically through gap junctions. This allows excitation to spread from cell to cell, so the heart muscle contracts as a coordinated unit.

Topic 12 — Cardiac Action Potential and Excitation–Contraction Coupling

Q60. Why is the ventricular action potential longer than a skeletal muscle action potential?

A: The ventricular action potential has a plateau phase due to calcium entry. This prolongs contraction and prevents tetany, allowing the heart to relax and fill before the next beat.

Q61. What is the importance of calcium in cardiac contraction?

A: Calcium enters during the action potential and triggers further calcium release inside the cell. Calcium binds to troponin, allowing actin and myosin interaction and cardiac muscle contraction.

Q62. Why can cardiac muscle not undergo sustained tetanic contraction?

A: Cardiac muscle has a long refractory period due to the plateau phase. This prevents repeated rapid stimulation and allows alternating contraction and relaxation, which is essential for pumping.

Q63. How does sympathetic stimulation increase cardiac performance?

A: Sympathetic stimulation increases heart rate, conduction velocity and contractility. It increases calcium availability in cardiac cells, producing stronger and faster contractions.

Topic 13 — Electrocardiography and Cardiovascular Risk Factors

Q64. What does an ECG actually record?

A: ECG records the electrical activity of the heart from the body surface. It does not directly record contraction but reflects the electrical events that lead to contraction.

Q65. What do the P wave, QRS complex and T wave represent?

A: The P wave represents atrial depolarization, QRS complex represents ventricular depolarization and T wave represents ventricular repolarization. These waves help assess rhythm and conduction.

Q66. Why is atrial repolarization not clearly visible on ECG?

A: Atrial repolarization occurs around the same time as ventricular depolarization. It is hidden by the larger QRS complex and is usually not seen separately.

Q67. Why is the PR interval important?

A: The PR interval reflects conduction from the atria through the AV node to the ventricles. Abnormal prolongation may suggest delayed AV conduction.

Q68. Why is the ST segment clinically important?

A: The ST segment represents the period when ventricles are depolarized. Abnormal elevation or depression may suggest myocardial injury or ischemia in a clinical setting.

Q69. How can lifestyle factors increase cardiovascular risk?

A: Smoking, unhealthy diet, physical inactivity, obesity and stress can damage vessels, increase blood pressure, worsen lipid profile and promote atherosclerosis. These factors increase risk of coronary artery disease.

Q70. Why is hypertension considered a major cardiovascular risk factor?

A: Hypertension increases workload on the heart and damages arterial walls. Over time, it promotes left ventricular hypertrophy, atherosclerosis, stroke, heart failure and kidney disease.

Q71. Why is smoking dangerous for the cardiovascular system?

A: Smoking damages endothelium, increases sympathetic activity, promotes thrombosis and accelerates atherosclerosis. It significantly increases risk of coronary artery disease and myocardial infarction.

Q72. How does exercise protect the cardiovascular system?

A: Regular exercise improves cardiac efficiency, lowers blood pressure, improves lipid profile, increases insulin sensitivity and helps weight control. It reduces long-term cardiovascular risk.