A 58-year-old man with chronic hypertension presents with progressive left ventricular hypertrophy on echocardiography. All of the following represent adaptive responses to chronic pressure overload EXCEPT:

Explanation

## Cardiac Hypertrophy: Adaptation vs Maladaptation ### Pathophysiology of Pressure Overload Hypertrophy **Key Point:** Hypertrophy is an adaptive response to increased workload, but chronic hypertrophy paradoxically becomes maladaptive, leading to dysfunction and eventual heart failure. ### Adaptive Mechanisms in Early Hypertrophy | Mechanism | Purpose | Outcome | |-----------|---------|----------| | Parallel sarcomere addition | Increase contractile force | Initially maintains wall stress | | Increased protein synthesis | Build muscle mass | Compensates for increased load | | Fetal gene reactivation | Metabolic efficiency | Shifts to glucose metabolism | | Increased myocardial mass | Distribute workload | Reduces wall stress temporarily | ### The Hypertrophy Paradox: Why Adaptation Fails **High-Yield:** Although hypertrophy initially **reduces** wall stress (Laplace's law: Wall stress = Pressure × Radius / 2 × Wall thickness), chronic hypertrophy leads to: 1. **Increased myocardial stiffness** → diastolic dysfunction 2. **Fibrosis and collagen deposition** → reduced compliance 3. **Mitochondrial dysfunction** → impaired ATP production 4. **Apoptosis and cell death** → progressive loss of contractile tissue 5. **Increased susceptibility to ischemia** → despite normal coronary arteries **Warning:** The statement "restoration of normal wall stress and prevention of further myocardial injury" is **FALSE**. While hypertrophy initially reduces wall stress, it does NOT prevent injury. Instead, chronic hypertrophy: - Leads to progressive fibrosis - Causes diastolic dysfunction - Eventually progresses to systolic dysfunction and heart failure - Increases risk of sudden cardiac death ### Why Hypertrophy Becomes Pathologic **Clinical Pearl:** In chronic hypertension, the hypertrophied heart may have: - Normal or supranormal ejection fraction (EF 50–70%) - **Severely reduced diastolic function** (E/A ratio reversal, prolonged deceleration time) - Increased risk of atrial fibrillation - Increased myocardial oxygen demand despite normal coronary flow **Mnemonic:** **FAIL** = Fibrosis, Apoptosis, Ischemia, Loss of function (the progression of maladaptive hypertrophy) ```mermaid flowchart TD A[Chronic Hypertension]:::outcome --> B[Increased Pressure Load]:::outcome B --> C[Parallel Sarcomere Addition]:::action C --> D[Hypertrophy Develops]:::outcome D --> E{Early Compensation?}:::decision E -->|Yes| F[Wall Stress Reduced]:::action E -->|No| G[Progressive Dysfunction]:::urgent F --> H[Fibrosis Begins]:::outcome H --> I[Diastolic Dysfunction]:::urgent I --> J[Systolic Dysfunction]:::urgent J --> K[Heart Failure]:::urgent ``` [cite:Robbins 10e Ch 2]