Hypertension for USMLE Step 2
Hypertension for the USMLE Step 2 Exam
Overview of Hypertension
Hypertension, defined as a blood pressure (BP) of ≥130/80 mm Hg, is a major modifiable risk factor for cardiovascular disease, stroke, and chronic kidney disease. The American College of Cardiology (ACC) and American Heart Association (AHA) have established hypertension categories to guide treatment and management.
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: Hypertension with no identifiable cause, accounting for approximately 90% of cases.
- Risk Factors: Family history, high sodium intake, obesity, alcohol use, sedentary lifestyle, age, and African American race.
- Pathophysiology: Involves complex interactions of genetic, environmental, and neurohormonal factors, affecting vascular resistance and sodium regulation.
Secondary Hypertension
- Definition: Hypertension due to a specific underlying condition, representing ~10% of cases.
- Causes:
- Renal Parenchymal Disease: Most common cause of secondary hypertension.
- Renovascular Disease: Renal artery stenosis, often from atherosclerosis or fibromuscular dysplasia.
- Endocrine Disorders: Hyperaldosteronism, pheochromocytoma, and Cushing’s syndrome.
- Medications: NSAIDs, corticosteroids, oral contraceptives, and decongestants.
- Obstructive Sleep Apnea: Associated with chronic sympathetic activation.
Diagnosis
Blood Pressure Measurement
- Office BP: BP should be measured after the patient has rested for five minutes, confirmed with two or more readings.
- Home BP Monitoring: Recommended to confirm diagnosis in patients with suspected white coat or masked hypertension.
- Ambulatory BP Monitoring (ABPM): Gold standard for evaluating white coat and masked hypertension, as well as assessing nocturnal BP.
Laboratory Workup
- Basic Tests:
- Electrolytes, BUN, and Creatinine: To assess renal function.
- Fasting Glucose and Lipid Profile: To screen for diabetes and hyperlipidemia, common in hypertensive patients.
- Urinalysis: To detect proteinuria or hematuria as indicators of renal involvement.
- ECG: May show signs of left ventricular hypertrophy (LVH) due to longstanding hypertension.
- Secondary Hypertension Workup:
- Aldosterone-to-Renin Ratio: For suspected hyperaldosteronism.
- 24-Hour Urine Metanephrines: For suspected pheochromocytoma.
- Renal Imaging: For suspected renovascular disease in young patients or those with resistant hypertension.
Management
Lifestyle Modifications
- Weight Reduction: Lowers BP by ~1 mm Hg per kg of weight lost.
- DASH Diet: High in fruits, vegetables, and low-fat dairy, and low in saturated fats; reduces BP by ~8–11 mm Hg.
- Sodium Restriction: Target <1500 mg/day, or <2400 mg/day for gradual reduction.
- Exercise: 90–150 minutes per week of aerobic activity, reducing BP by ~4–8 mm Hg.
- Alcohol Limitation: ≤2 drinks/day for men and ≤1 drink/day for women.
Pharmacologic Therapy
- First-Line Medications:
- Thiazide Diuretics: Preferred for most patients, effective in volume reduction.
- ACE Inhibitors (ACEIs) and ARBs: Preferred for patients with diabetes, chronic kidney disease, or heart failure.
- Calcium Channel Blockers (CCBs): Effective, especially in African American and older patients.
- Beta-Blockers: Not first-line for hypertension alone but indicated for heart failure, post-MI, and arrhythmias.
- When to Initiate Therapy:
- Stage 1 Hypertension: Start medication if there is a history of cardiovascular disease (CVD) or a 10-year ASCVD risk ≥10%.
- Stage 2 Hypertension: Start medication for all patients, regardless of risk.
- Resistant Hypertension: Defined as BP ≥130/80 mm Hg on three optimally dosed antihypertensives, including a diuretic.
- Management: Evaluate for secondary causes; add an aldosterone antagonist (e.g., spironolactone) if needed.
Complications
- Cardiovascular: Left ventricular hypertrophy, coronary artery disease, heart failure.
- Cerebrovascular: Stroke and transient ischemic attack.
- Renal: Chronic kidney disease and nephrosclerosis.
- Retinopathy: Ranges from mild AV nicking to severe papilledema in malignant hypertension.
Key Points
- Hypertension Classification: Defined as BP ≥130/80 mm Hg, with Stage 1 and Stage 2 categories guiding management.
- Diagnosis: Confirmed with multiple measurements, including ambulatory or home monitoring for suspected white coat or masked hypertension.
- Management:
- Lifestyle Modifications: Recommended for all patients, emphasizing diet, weight loss, exercise, and sodium reduction.
- Pharmacologic Therapy: First-line agents include thiazides, ACE inhibitors/ARBs, and CCBs.
- Resistant Hypertension: Investigate secondary causes and consider aldosterone antagonists.
- Complications: Hypertension significantly increases the risk of cardiovascular events, kidney disease, stroke, and hypertensive retinopathy.
- Emergencies:
- Hypertensive Emergency: BP ≥180/120 mm Hg with end-organ damage, requiring IV antihypertensives.
- Hypertensive Urgency: BP ≥180/120 mm Hg without end-organ damage, managed with oral antihypertensives over 24–48 hours.