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PA26.1-10 | Cardiovascular System — PBL Case

CLINICAL SETTING

Suresh Yadav, a 48-year-old marginal farmer from a village in Bundelkhand district, Madhya Pradesh, is brought to the medicine casualty of a district hospital by his son after collapsing in the field. Three months earlier he had been seen at the PHC for swollen legs and breathlessness on walking. He was given diuretics but did not follow up. He is a non-smoker and does not drink alcohol. He has a history of repeated sore throats during childhood and received irregular treatment. At age 35 he was told he had a 'leaky valve' at a camp. His eldest daughter (age 14) was recently diagnosed with a small hole in her heart at a cardiac screening camp but is asymptomatic. On examination: Suresh is dyspnoeic at rest (RR 28/min), SpO2 87% on room air, BP 90/60 mmHg, heart rate 118/min and irregularly irregular. JVP elevated 6 cm above sternal angle. Bilateral basal fine crepitations. A loud diastolic rumbling murmur is best heard at the apex with the bell of the stethoscope in the left lateral decubitus position. Moderate bilateral pitting oedema to mid-shin. The liver is palpable 4 cm below the right costal margin, firm and slightly tender. His son mentions that Suresh's father died suddenly of 'heart attack' at age 52 while working.

Trigger 1: Initial Assessment

ECG: atrial fibrillation with ventricular rate 118/min, no acute ST changes. Chest X-ray: cardiomegaly (CTR 0.62), bilateral perihilar haziness with upper lobe diversion of pulmonary vessels, small bilateral pleural effusions. Kerley B lines at both bases. BNP 1,820 pg/mL (normal < 100). Echocardiogram: left atrium markedly enlarged (5.4 cm); mitral valve shows thickened, calcified leaflets with restricted opening — mitral valve area 0.9 cm² (severe mitral stenosis); heavy fibrosis of the subvalvular apparatus; LA thrombus present in the left atrial appendage; LV ejection fraction 35%. Troponin T: 0.06 ng/mL (mildly elevated). Blood: Hb 9.2 g/dL, WBC 11,200, CRP 48 mg/L, ASO titre 480 IU/mL (normal < 200).

DISCUSSION POINTS

  • Suresh has severe mitral stenosis with a history of childhood sore throats and irregular treatment. Reconstruct the pathological sequence from Group A streptococcal pharyngitis through acute rheumatic fever to chronic rheumatic heart disease. What is the immunological mechanism that causes cardiac valve damage, and which specific molecular structures are targeted?
  • The echocardiogram shows left atrial enlargement, fibrosis of the subvalvular apparatus, and LA thrombus. Describe the gross and microscopic pathology of chronic rheumatic mitral stenosis. Why does the left atrium dilate? How does LA thrombus formation occur, and what is its most dangerous consequence?
  • Suresh is in atrial fibrillation. Explain how mitral stenosis leads to AF. What is the haemodynamic consequence of AF in the setting of mitral stenosis, and how does AF worsen his existing heart failure?
  • His BNP is markedly elevated and he has bilateral crepitations and pleural effusions. Apply the heart failure classification framework: Is this left-sided, right-sided, or biventricular failure? Identify the cause, the haemodynamic mechanism, and the morphological changes you would expect in the lungs (pulmonary congestion) and liver (nutmeg liver) at this stage.
Click to reveal Trigger 2: New Complication Emerges (discuss previous trigger first!)

Trigger 2: New Complication Emerges

Suresh is stabilised on IV furosemide, digoxin, and anticoagulation. On day 5 of admission, he develops sudden high fever (39.8 °C), rigors, and a new systolic murmur (grade 3/6, harsh, best heard at the left sternal border). Blood cultures (three sets, 12 h apart) all grow Streptococcus viridans (alpha-haemolytic streptococcus). Repeat echo shows a 1.2 × 0.8 cm mobile, friable, irregular vegetation on the mitral valve — on the atrial surface of the posterior leaflet, larger than the vegetations described in pure rheumatic disease. His platelet count has dropped to 95,000/µL. CRP is now 180 mg/L. The treating team notes peripheral stigmata: Osler nodes on the fingertips, Janeway lesions on the palms, and splinter haemorrhages under three nails.

DISCUSSION POINTS

  • Suresh has developed infective endocarditis (IE) superimposed on rheumatic mitral stenosis. Describe the pathogenesis of IE — how does bacteraemia seed the valve, and why are previously damaged valves particularly vulnerable? Compare the gross and microscopic features of infective vegetations with those of rheumatic (small, row-of-beads) vegetations.
  • The peripheral stigmata — Osler nodes, Janeway lesions, and splinter haemorrhages — have different pathological mechanisms. Explain the pathological mechanism of each. Which of these are embolic and which are immune-complex-mediated?
  • Compare Suresh's Streptococcus viridans IE (subacute IE) with acute IE caused by Staphylococcus aureus in an IV drug user. Contrast them across: organism virulence, valve initially affected, vegetation size and character, clinical tempo, and risk of systemic emboli.
  • IE has caused a new regurgitant lesion on the mitral valve. Explain the haemodynamic consequences of acute severe mitral regurgitation superimposed on existing mitral stenosis. How does this differ pathophysiologically from the slow haemodynamic deterioration of chronic rheumatic heart disease?
Click to reveal Trigger 3: Broader Family and Systemic Implications (discuss previous trigger first!)

Trigger 3: Broader Family and Systemic Implications

Suresh improves with IV antibiotics. His 14-year-old daughter, Priya, is brought for evaluation. Cardiac echo confirms a perimembranous ventricular septal defect (VSD) 0.8 cm diameter with left-to-right shunting. She has mild pulmonary hypertension (RVSP 42 mmHg). She is asymptomatic. Meanwhile, Suresh's son discovers that Suresh's father's death at age 52 was from a 'sudden massive heart attack' and that a post-mortem had shown a ruptured papillary muscle and haemopericardium. Suresh's own fasting lipid profile: total cholesterol 248 mg/dL, LDL 168 mg/dL, HDL 32 mg/dL, TG 310 mg/dL. Fasting glucose 128 mg/dL. The cardiologist notes that Suresh's aorta shows diffuse intimal thickening on echo.

DISCUSSION POINTS

  • Priya has a VSD with early pulmonary hypertension. Explain the pathophysiology of left-to-right shunting in VSD: why does blood flow from left to right, what structural changes develop in the pulmonary vasculature over time, and at what point could Eisenmenger syndrome develop? What are the histological changes in pulmonary vessels in Eisenmenger syndrome?
  • Suresh's father had a ruptured papillary muscle and haemopericardium — a complication of acute myocardial infarction. Describe the full pathological timeline of myocardial infarction (gross and microscopic changes from 0–6 hours to 6+ weeks) and explain why papillary muscle rupture occurs specifically at days 3–7 post-infarction. What features make the papillary muscle vulnerable?
  • Suresh has dyslipidaemia and borderline hyperglycaemia. Describe the response-to-injury hypothesis of atherosclerotic plaque formation. Which specific steps are driven by oxidised LDL, macrophage foam cells, and smooth muscle cell proliferation? Distinguish a vulnerable plaque (thin cap fibroatheroma) from a stable plaque and explain why vulnerable plaques cause MI despite causing less than 50% stenosis.
  • Suresh's LV ejection fraction is 35% — consistent with dilated cardiomyopathy (DCM) superimposed on valvular disease. Describe the gross and microscopic features of DCM. What are the major causes of DCM relevant to the Indian population, and how does it differ pathologically from hypertrophic cardiomyopathy (HCM)? Why is HCM a cause of sudden cardiac death in young athletes?

Group Task Assignments

Group 1: Atherosclerosis and Ischaemic Heart Disease

  • Construct a step-by-step diagram of the response-to-injury hypothesis of atherosclerosis, labelling: endothelial injury trigger, LDL oxidation, foam cell formation, fatty streak, fibrous cap development, plaque rupture, and thrombosis. Annotate each step with the cell type and mediator responsible.
  • Prepare the pathological timeline of myocardial infarction: tabulate gross and microscopic changes at < 4 h, 4–12 h, 12–24 h, 1–3 days, 3–7 days, 1–3 weeks, and > 2 months. Include complications expected at each phase and explain why troponin peaks at 24–48 h.

Competencies: PA26.1, PA26.6

Group 2: Rheumatic Fever and Infective Endocarditis

  • Draw a schematic of the molecular mimicry mechanism in acute rheumatic fever — from GABHS M-protein epitopes to cross-reactive antibodies against cardiac myosin and valve glycoproteins. Describe the Aschoff body and its cellular composition. List the Jones diagnostic criteria (major and minor).
  • Prepare a comparison table of the five types of cardiac vegetations: rheumatic (ARF), acute IE, subacute IE, NBTE, and Libman-Sacks — covering size, location on valve, sterility/infectivity, risk of systemic embolism, and the underlying mechanism of formation.

Competencies: PA26.5, PA26.7

Group 3: Heart Failure and Congenital Heart Disease

  • Construct a table comparing left heart failure and right heart failure: primary cause, haemodynamic mechanism, pulmonary consequences (for LHF), systemic venous consequences (for RHF), liver changes (nutmeg liver → cardiac cirrhosis), and NYHA classification stages.
  • Classify congenital heart defects into left-to-right shunts, right-to-left shunts, and obstructive lesions. For each major defect (VSD, ASD, PDA, ToF, coarctation), describe the haemodynamic mechanism, direction of shunt, cyanosis timing, and the Eisenmenger sequence applicable to shunt lesions.

Competencies: PA26.3, PA26.4

Group 4: Aneurysms, Cardiomyopathies, and Pericardial Disease

  • Compare abdominal aortic aneurysm (AAA) and aortic dissection: aetiology, location, type (true vs false), Laplace's law explanation for progression, gross pathology, clinical presentation, and life-threatening complication. Include syphilitic aortitis as a historical differential.
  • Classify cardiomyopathies (dilated, hypertrophic, restrictive) by gross and microscopic features, primary aetiology, haemodynamic consequence, and risk of sudden death. Describe endomyocardial fibrosis as an Indian-specific restrictive cardiomyopathy and explain its pathogenesis.

Competencies: PA26.2, PA26.8, PA26.9

Group 5: Cardiac Tumours and Pericarditis

  • Describe cardiac myxoma: location (left atrium, near fossa ovalis), gross appearance, microscopic features (stellate cells in myxoid stroma), clinical consequences (ball-valve obstruction, tumour embolism, constitutional symptoms), and its distinction from organised thrombus.
  • Describe the six morphological types of pericarditis (serous, fibrinous, purulent, haemorrhagic, caseous, constrictive) and map each to its most common aetiology. Explain the pathophysiology of cardiac tamponade and constrictive pericarditis, distinguishing them by haemodynamic and morphological criteria.

Competencies: PA26.8, PA26.10

Learning Issues

Research these questions and bring your findings to the discussion.

  1. [PA26.1] Distinguish arteriosclerosis from atherosclerosis. Describe the response-to-injury hypothesis of atherosclerotic plaque formation, the morphology of the atheromatous plaque, the concept of the vulnerable plaque, and the systemic complications of atherosclerosis.
  2. [PA26.2] Define aneurysm and classify true vs false aneurysms. Describe the aetiology, pathology, and complications of AAA and aortic dissection. Apply Laplace's law to explain why aneurysms enlarge progressively.
  3. [PA26.3] Define heart failure and describe its compensatory mechanisms and their maladaptation. Classify heart failure (left vs right, systolic vs diastolic, high-output vs low-output) and describe the pathological changes in lungs (pulmonary oedema) and liver (nutmeg liver, cardiac cirrhosis).
  4. [PA26.4] Classify congenital heart disease into left-to-right shunts, right-to-left shunts, and obstructive lesions. Describe the pathophysiology and complications of VSD, ASD, PDA, and Tetralogy of Fallot. Explain Eisenmenger syndrome and paradoxical embolism.
  5. [PA26.5] Describe the pathogenesis of acute rheumatic fever via molecular mimicry. List the Jones criteria. Describe the pancarditis of ARF including the Aschoff body. Describe the gross and microscopic pathology of chronic rheumatic mitral stenosis and its complications.
  6. [PA26.6] Describe the epidemiology, pathophysiology, and pathology of ischaemic heart disease. Describe the gross and microscopic timeline of myocardial infarction. Explain the ACS spectrum (stable angina, unstable angina, NSTEMI, STEMI) and interpret troponin and ECG changes in ACS.
  7. [PA26.7] Classify infective endocarditis into acute and subacute forms. Describe the pathogenesis, gross features of vegetations, peripheral stigmata (Osler nodes, Janeway lesions, Roth spots, splinter haemorrhages), Duke criteria, and complications including systemic embolism and valve destruction.
  8. [PA26.8] Describe the aetiology and morphological types of pericarditis. Explain the pathophysiology of cardiac tamponade and constrictive pericarditis. Describe pericardial effusion and its classification by fluid type.
  9. [PA26.9] Classify cardiomyopathies into dilated, hypertrophic, and restrictive types. For each, describe the aetiology, gross and microscopic pathology, haemodynamic consequences, and risk of sudden death. Describe endomyocardial fibrosis as an Indian example of restrictive cardiomyopathy.
  10. [PA26.10] Describe the pathology, location, clinical consequences, and microscopic features of cardiac myxoma. Classify primary malignant cardiac tumours and describe the route and frequency of cardiac metastases.