Hypertension for USMLE Step 3
Hypertension for the USMLE Step 3 Exam
Overview of Hypertension
Hypertension is defined as a systolic blood pressure (SBP) ≥130 mm Hg or a diastolic blood pressure (DBP) ≥80 mm Hg, according to ACC/AHA guidelines. It is a key modifiable risk factor for cardiovascular disease, stroke, and renal impairment.
Classification of Hypertension
- Normal: SBP <120 mm Hg and DBP <80 mm Hg
- Elevated: SBP 120–129 mm Hg and DBP <80 mm Hg
- Stage 1 Hypertension: SBP 130–139 mm Hg or DBP 80–89 mm Hg
- Stage 2 Hypertension: SBP ≥140 mm Hg or DBP ≥90 mm Hg
Types of Hypertension
Primary (Essential) Hypertension
- Definition: No identifiable cause, accounting for approximately 90% of cases.
- Risk Factors: Family history, high sodium diet, obesity, sedentary lifestyle, age, and African American ethnicity.
- Pathophysiology: Multifactorial, involving genetic predisposition, neurohormonal dysregulation, and environmental factors affecting vascular tone and renal sodium handling.
Secondary Hypertension
- Definition: Hypertension with a specific underlying cause, present in ~10% of cases.
- Causes:
- Renal Parenchymal Disease: Most common cause of secondary hypertension.
- Renovascular Hypertension: Due to renal artery stenosis, from atherosclerosis or fibromuscular dysplasia.
- Endocrine Disorders: Includes hyperaldosteronism, pheochromocytoma, and Cushing’s syndrome.
- Obstructive Sleep Apnea: Linked with chronic sympathetic activation.
- Medications: NSAIDs, corticosteroids, oral contraceptives, and decongestants.
Diagnosis
Blood Pressure Measurement
- Office BP: Obtain after five minutes of rest, confirmed with multiple readings across separate visits.
- Ambulatory BP Monitoring (ABPM): Gold standard for diagnosing white coat and masked hypertension, as well as nocturnal hypertension.
- Home BP Monitoring: Recommended for additional data and confirmation in cases of suspected white coat hypertension.
Laboratory Workup
- Basic Tests:
- Electrolytes, BUN, and Creatinine: To evaluate renal function and electrolyte status.
- Fasting Glucose and Lipid Profile: Screening for metabolic syndrome, diabetes, and dyslipidemia.
- Urinalysis: Detects proteinuria or hematuria, indicating renal involvement.
- ECG: Assesses for left ventricular hypertrophy (LVH) and other signs of long-standing hypertension.
- Secondary Hypertension Workup:
- Aldosterone-to-Renin Ratio: For primary hyperaldosteronism.
- 24-Hour Urine Metanephrines: For suspected pheochromocytoma.
- Renal Imaging: For renovascular hypertension, especially in younger patients or those with resistant hypertension.
Management
Lifestyle Modifications
- Weight Loss: Reduces BP by approximately 1 mm Hg per kg of weight lost.
- DASH Diet: Emphasizes fruits, vegetables, and low-fat dairy; can lower BP by 8–11 mm Hg.
- Sodium Restriction: Target of <1500 mg/day, with <2400 mg/day as an initial goal.
- Physical Activity: 90–150 minutes of moderate-intensity aerobic exercise weekly.
- Alcohol Limitation: ≤2 drinks per day for men, ≤1 drink per day for women.
Pharmacologic Therapy
- First-Line Agents:
- Thiazide Diuretics: Effective for volume reduction; chlorthalidone is preferred due to its long half-life.
- ACE Inhibitors (ACEIs) / ARBs: Preferred in patients with diabetes, chronic kidney disease, or heart failure.
- Calcium Channel Blockers (CCBs): Particularly effective in African American and elderly patients.
- Beta-Blockers: Not first-line but indicated in heart failure, post-myocardial infarction, and certain arrhythmias.
- Indications for Therapy:
- Stage 1 Hypertension: Start medication if there is established cardiovascular disease (CVD) or a 10-year ASCVD risk ≥10%.
- Stage 2 Hypertension: Initiate therapy in all patients regardless of ASCVD risk.
- Resistant Hypertension: Defined as BP ≥130/80 mm Hg despite optimal doses of three antihypertensives, including a diuretic.
- Management: Consider adding an aldosterone antagonist (e.g., spironolactone) and evaluate for secondary causes.
Complications
- Cardiovascular: Left ventricular hypertrophy, coronary artery disease, heart failure.
- Cerebrovascular: Stroke and transient ischemic attack.
- Renal: Chronic kidney disease and nephrosclerosis.
- Retinopathy: Progresses from mild AV nicking to papilledema in malignant hypertension.
Key Points
- Classification: Hypertension is defined as BP ≥130/80 mm Hg, with Stage 1 and Stage 2 categories for guiding management.
- Diagnosis: Accurate BP measurement with confirmation through ABPM or home monitoring, especially for suspected white coat or masked hypertension.
- Management:
- Lifestyle Modifications: Key for all patients, including DASH diet, weight reduction, and sodium restriction.
- Pharmacologic Therapy: First-line agents are thiazides, ACEIs/ARBs, and CCBs.
- Resistant Hypertension: Screen for secondary causes and consider aldosterone antagonists.
- Complications: Hypertension significantly increases the risk of cardiovascular, cerebrovascular, and renal disease.
- Emergencies:
- Hypertensive Emergency: BP ≥180/120 mm Hg with end-organ damage, requiring immediate IV antihypertensives.
- Hypertensive Urgency: BP ≥180/120 mm Hg without end-organ damage, managed with oral antihypertensives over 24–48 hours.