Pathomechanism of cardiac insufficiency

1. Definition

• Cardiac insufficiency (heart failure) = the heart cannot pump enough blood for the body → blood backs up (congestion) and/or forward under-perfusion.
• Left HF → pulmonary congestion (dyspnea); Right HF → systemic congestion (edema, ascites).

2. Left-Sided Heart Failure

Type	EF	Mechanism
Systolic (HFrEF)	↓ reduced	LV can’t contract forcefully; weak/thin LV → backward flow
Diastolic (HFpEF)	preserved	Stiff/thick LV can’t fill → ↓output

• Causes: coronary artery disease, MI, valvular disease, hypertension (→ LVH → loss of elasticity → failure).
• Hypertrophy pattern reflects stimulus: concentric (pressure overload — HTN, aortic stenosis; ↑wall, ↓cavity) vs eccentric (volume overload — aortic insufficiency; dilation).
• Symptoms: cough, dyspnea/orthopnea, pulmonary edema; later cardiomegaly, arrhythmia, cardiogenic shock.

3. Right-Sided Heart Failure (Cor Pulmonale)

• RV too weak against ↑pulmonary resistance/BP → RV hypertrophy → failure → venous backup → systemic edema.
• Causes: pulmonary hypertension, PE, COPD, CF/interstitial fibrosis, emphysema; left HF = most common cause.
• Symptoms: peripheral edema, ascites, hepatic congestion, dyspnea, ↑HR.
• Acute cor pulmonale (PE >50% obstruction → RV dilation only) vs chronic (prolonged overload → RV hypertrophy ± dilation).

4. Compensatory Mechanisms

• Sympathetic activation + RAAS → vasoconstriction + Na⁺/water retention → ↑preload/afterload → eventual decompensation.
• ANP/BNP counter-regulate (natriuresis/vasodilation); BNP is a diagnostic marker.

💡 High-yield: Left HF → lungs (dyspnea, S3, orthopnea/PND); Right HF → systemic (edema, ascites, nutmeg liver). Left HF is the commonest cause of right HF. Systolic = ↓EF, diastolic = preserved EF. RAAS/sympathetic compensation eventually worsens failure.