A 52-year-old man with hypertension and benign prostatic hyperplasia is prescribed an alpha-1 blocker. After 2 weeks, he reports new-onset syncope and orthostatic dizziness. Which investigation is most appropriate to confirm the suspected adverse effect and guide dose adjustment?

## Investigation of Choice for Alpha-Blocker–Induced Orthostatic Hypotension ### Clinical Scenario Alpha-1 blockers cause vasodilation and are notorious for **first-dose syncope** and **orthostatic hypotension**, especially in the first 2 weeks of therapy. The patient's presentation (syncope + dizziness shortly after initiation) is classic for this adverse effect. ### Why Supine and Standing BP (Orthostatic Vital Signs)? **Key Point:** Orthostatic vital signs (supine BP, then standing BP after 1–3 minutes) are the **gold standard, bedside investigation** to diagnose orthostatic hypotension. A drop of ≥20 mmHg systolic or ≥10 mmHg diastolic confirms the diagnosis. **High-Yield:** This is a **simple, non-invasive, reproducible test** that directly confirms alpha-blocker–induced vasodilation and guides immediate management (dose reduction, slower titration, or switch to alternative agent). **Clinical Pearl:** Orthostatic hypotension from alpha-blockers typically occurs within the first 30 minutes to 2 hours after the first dose or dose escalation. Checking orthostatic vitals at the time of symptoms is diagnostic. ### Comparison of Investigations | Investigation | Indication | Utility in This Case | |---|---|---| | **Orthostatic vital signs** | **Suspected orthostatic hypotension** | **Gold standard; immediate, bedside diagnosis** | | Tilt-table test | Recurrent syncope of unclear etiology; vasovagal syncope | Unnecessary; diagnosis is already clinically evident | | 24-hour ABPM | Hypertension control assessment; white-coat effect | Does not specifically diagnose orthostatic hypotension | | Echocardiography | Cardiac dysfunction, heart failure | Not indicated; no cardiac pathology suspected | ### Mechanism of Alpha-Blocker–Induced Orthostatic Hypotension **Mnemonic: ALPHA-INDUCED SYNCOPE (AIS)** - **A**rteriolar and venous vasodilation (α~1~ blockade) - **L**oss of sympathetic tone - **P**ostural shift → pooling of blood in lower extremities - **H**ypotension on standing - **A**cute reduction in cerebral perfusion → syncope ### Management Implications 1. **Confirm diagnosis** with orthostatic vital signs. 2. **Reduce dose** or extend dosing interval. 3. **Educate patient** on slow position changes, adequate hydration, salt intake. 4. **Consider alternative** (e.g., 5-alpha reductase inhibitor) if orthostatic hypotension persists. **Warning:** Do NOT perform tilt-table testing if orthostatic hypotension is already clinically evident—it is unnecessary and potentially dangerous.