HHD Pathophysiology - Pressure Overload
- Mechanism: Chronic ↑ afterload (e.g., systemic HTN, aortic stenosis) forces the left ventricle (LV) to generate higher pressures.
- Cellular Adaptation: Myocytes enlarge (hypertrophy) by adding new sarcomeres in parallel.
- This results in concentric hypertrophy → ↑ LV wall thickness, often with a ↓ in chamber radius.
- Physics: Compensatory hypertrophy normalizes wall stress per Laplace’s Law ($Wall Stress = (P \times r) / (2h)$) by increasing wall thickness (h).

⭐ The earliest manifestation of HHD is typically diastolic dysfunction, leading to Heart Failure with preserved Ejection Fraction (HFpEF). Systolic failure (HFrEF) is a late complication.
Systemic (Left) HHD - The Body's Burden
- Pathogenesis: Chronic systemic hypertension imposes a pressure overload (↑ afterload) on the left ventricle (LV), forcing it to work harder.
- LV Adaptation & Failure: The ventricle adapts via concentric hypertrophy (thickened wall) to normalize wall stress. This eventually leads to:
- Stiff LV → Impaired diastolic filling (diastolic dysfunction).
- ↑ Myocardial O₂ demand → Susceptibility to ischemia.
- Left atrial enlargement → Risk of atrial fibrillation.
- Morphology & Dx:
- Gross: Symmetrically thickened LV wall (>1.2 cm), ↑ heart weight.
- Micro: Enlarged myocytes with "boxcar" nuclei; interstitial fibrosis.
- ECG: May show LVH criteria (e.g., Sokolow-Lyon: S in V1 + R in V5/V6 > 35 mm).

⭐ The earliest manifestation is often diastolic dysfunction with preserved ejection fraction (HFpEF), as the stiff, hypertrophied ventricle cannot relax and fill properly.
Pulmonary (Right) HHD - Cor Pulmonale
- Definition: Right ventricular (RV) hypertrophy and/or dilation resulting from pulmonary hypertension (PH) caused by diseases of the lung parenchyma or vasculature.
- Pathophysiology Flow:
- Common Causes:
- COPD (most frequent)
- Interstitial lung disease
- Chronic thromboembolic disease (CTEPH)
- Obstructive sleep apnea
- Clinical Findings:
- Symptoms of underlying lung disease + signs of right heart failure (JVD, peripheral edema, hepatomegaly).
- Loud P2, tricuspid regurgitation murmur.
- Diagnosis:
- Echo: Shows RVH, estimates pulmonary artery pressure.
- Right Heart Cath: Gold standard to confirm PH.
⭐ The most common cause of right-sided heart failure is left-sided heart failure. Cor pulmonale is specifically right-sided failure due to lung pathology.

HHD Morphology - Sizing Up Damage
- Systemic (Left) HHD:
- Gross: Symmetrical, concentric left ventricular hypertrophy (LVH) without dilation initially. ↑ heart weight.
- Wall thickness can exceed 2.0 cm.
- Micro: Enlarged cardiomyocytes with prominent, hyperchromatic "boxcar" nuclei.
- Interstitial fibrosis develops over time.
- Pulmonary (Right) HHD / Cor Pulmonale:
- Gross: Right ventricular hypertrophy and dilation, often with wall thickness >1.0 cm.

⭐ A stiff, non-compliant LV from chronic hypertrophy leads to impaired diastolic filling, often manifesting as a prominent S4 heart sound.
High‑Yield Points - ⚡ Biggest Takeaways
- Systemic hypertension is the fundamental cause, creating pressure overload on the left ventricle.
- The heart adapts via concentric left ventricular hypertrophy (LVH).
- Histology classically shows enlarged myocytes with prominent "boxcar" nuclei.
- Clinically, it first manifests as diastolic dysfunction (HFpEF).
- An S4 gallop is a common auscultatory finding.
- Uncontrolled, it can progress to systolic dysfunction and overt heart failure.
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