Heart Failure & Cardiomyopathies: MBBS Guide

Heart failure is a clinical syndrome in which the heart cannot pump enough blood to meet the body's needs, or can do so only at abnormally high filling pressures. Patients develop breathlessness, fatigue, and fluid retention such as ankle swelling and lung congestion.

It matters because heart failure is one of the commonest causes of hospital admission in adults and carries high mortality when untreated. Cardiomyopathies - diseases of the heart muscle itself - are important causes, especially in younger patients. Understanding types and stages guides drug therapy, devices, and transplant decisions.

Key Concepts

• Ejection fraction (EF): the percentage of blood in the ventricle pumped out each beat; normal is 55-70%.
• HFrEF: heart failure with reduced EF (below 40%); the ventricle is weak and dilated.
• HFpEF: heart failure with preserved EF (50% or more); the ventricle is stiff and fills poorly.
• NYHA classes I to IV: I, no limitation; II, slight limitation; III, marked limitation with less-than-ordinary activity; IV, symptoms at rest.
• Dilated cardiomyopathy: enlarged, thin-walled, weak ventricles - the commonest cardiomyopathy.
• Hypertrophic cardiomyopathy: thickened walls, often asymmetric septal hypertrophy; a cause of sudden death in young athletes.
• Restrictive cardiomyopathy: stiff walls of normal thickness with poor filling; seen in amyloidosis.
• BNP / NT-proBNP: blood markers released by stretched heart muscle, used to diagnose and track heart failure.

Formulas

• Ejection fraction: EF = (stroke volume / end-diastolic volume) x 100. Stroke volume = end-diastolic volume - end-systolic volume.
• Cardiac output: CO = heart rate x stroke volume; normal resting CO is about 5 L/min.
• These assume accurate echo measurements; EF can look normal in HFpEF despite severe symptoms because the chamber is small and stiff.

Worked Example

An echocardiogram reports end-diastolic volume 120 mL and end-systolic volume 72 mL. Stroke volume = 120 - 72 = 48 mL. Ejection fraction = (48 / 120) x 100 = 40%. An EF of 40% is mildly reduced; with breathlessness and edema this patient fits heart failure with mildly reduced EF. If the heart rate is 80 beats/min, cardiac output = 80 x 48 = 3840 mL/min, about 3.8 L/min - below the normal 5 L/min.

Common Misconceptions

• Heart failure means the heart has stopped. It has not: the heart still beats but pumps inadequately. The heart stopping is cardiac arrest, a different emergency.
• A normal ejection fraction rules out heart failure. HFpEF has a normal EF; diagnosis rests on symptoms, signs, BNP, and echo evidence of diastolic dysfunction.
• All heart failure is treated the same. HFrEF benefits from ACE inhibitors, beta blockers, and mineralocorticoid antagonists; HFpEF management centres on diuretics, blood-pressure control, and SGLT2 inhibitors.

Real-World Applications

• Framingham criteria plus BNP testing diagnose heart failure in clinics and emergency rooms.
• Echocardiography classifies HFrEF vs HFpEF and screens families for hypertrophic cardiomyopathy.
• Implantable defibrillators and cardiac resynchronisation devices prevent sudden death in selected patients.
• End-stage dilated cardiomyopathy is a leading indication for heart transplantation.

Heart failure is the failing-pump syndrome behind breathlessness and fluid overload; cardiomyopathies are key muscle-level causes. Ejection fraction and NYHA class organise diagnosis and treatment, but preserved-EF failure reminds us that a normal number never overrules the patient's symptoms.