A 58-year-old man with a 10-year history of essential hypertension presents with a blood pressure of 168/105 mmHg. Which of the following is the most common mechanism responsible for the elevation in his diastolic blood pressure?

Explanation

## Mechanisms of Diastolic Hypertension in Essential Hypertension **Key Point:** Increased peripheral vascular resistance (PVR) is the primary and most common mechanism responsible for diastolic hypertension in essential hypertension, accounting for the sustained elevation in diastolic pressure. ### Hemodynamic Basis of Blood Pressure Blood pressure is determined by the fundamental relationship: $$BP = CO \times TPR$$ where CO = cardiac output and TPR = total peripheral resistance. ### Mechanisms in Essential Hypertension | Mechanism | Role in Early HTN | Role in Established HTN | Diastolic BP Effect | |---|---|---|---| | **↑ Peripheral Resistance** | **Primary** | **Dominant** | **↑↑ (sustained)** | | ↑ Cardiac Output | Early phase | Normalizes | Mild ↑ | | ↓ Arterial Compliance | Secondary | Contributes | ↑ Pulse pressure | | ↑ Sympathetic tone | Early | Persists | ↑↑ | ### Pathophysiology in This Patient **High-Yield:** In established essential hypertension (10-year history), the primary abnormality is **increased peripheral vascular resistance** due to: 1. **Structural changes** — Medial hypertrophy and inward remodeling of arterioles 2. **Functional abnormalities** — Enhanced sympathetic nervous system activity and increased vascular smooth muscle reactivity 3. **Endothelial dysfunction** — Reduced nitric oxide (NO) availability and increased endothelin-1 (ET-1) production 4. **Sodium-volume expansion** — Chronic sodium retention increases intravascular volume and vascular reactivity ### Why Diastolic Pressure Specifically? **Clinical Pearl:** Diastolic pressure reflects the resistance to flow during diastole when the aortic valve is closed. Increased PVR directly impedes forward flow, preventing adequate diastolic pressure decay. This is why diastolic hypertension is the hallmark of increased peripheral resistance. ### Progression Over Time ```mermaid flowchart TD A[Early Essential HTN]:::outcome --> B[↑ Sympathetic tone<br/>↑ Cardiac output]:::action B --> C[↑ BP, normal PVR]:::outcome C --> D[Chronic elevation]:::action D --> E[Arteriolar remodeling<br/>Structural changes]:::action E --> F[↑↑ Peripheral Resistance]:::urgent F --> G[Sustained ↑ Diastolic BP<br/>↑ Pulse Pressure]:::outcome ``` **Mnemonic:** **RESIST** — In essential hypertension, **Resistance** (peripheral vascular resistance) is the primary mechanism causing sustained **Diastolic** elevation.