Hypertension for USMLE Step 1
Hypertension for the USMLE Step 1 Exam
Overview of Hypertension
Hypertension is defined as persistently elevated blood pressure (BP), a significant risk factor for cardiovascular disease, stroke, and chronic kidney disease. The American College of Cardiology (ACC) and American Heart Association (AHA) define hypertension as systolic BP (SBP) ≥130 mm Hg or diastolic BP (DBP) ≥80 mm Hg.
Classification
- 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 underlying cause, accounts for ~90% of cases.
- Risk Factors: Family history, high sodium intake, obesity, sedentary lifestyle, increased age, and African American race.
- Pathophysiology: Involves genetic, environmental, and neurohormonal factors affecting vascular resistance, renal sodium handling, and cardiac output.
Secondary Hypertension
- Definition: Hypertension with an identifiable cause, making up ~10% of cases.
- Common Causes:
- Renal Parenchymal Disease: Most common cause of secondary hypertension.
- Renovascular Hypertension: Often due to renal artery stenosis.
- Endocrine Disorders: Hyperaldosteronism, pheochromocytoma, and Cushing’s syndrome.
- Obstructive Sleep Apnea: Associated with chronic sympathetic activation.
- Medications: NSAIDs, oral contraceptives, decongestants, and corticosteroids.
Diagnosis
Blood Pressure Measurement
- Office BP: Measured after the patient is seated for five minutes, confirmed with multiple readings.
- Ambulatory BP Monitoring (ABPM): Considered the gold standard for diagnosing white coat and masked hypertension, also useful for nocturnal BP assessment.
- Home BP Monitoring: Recommended for additional confirmation and monitoring.
Laboratory Workup
- Basic Tests:
- Electrolytes, Creatinine, and BUN: Evaluate renal function and electrolyte abnormalities.
- Urinalysis: Check for proteinuria and hematuria, indicative of kidney involvement.
- Lipid Panel and Fasting Glucose: Screen for diabetes and dyslipidemia, common comorbidities.
- ECG: May show signs of LV hypertrophy.
- Secondary Hypertension Screening:
- Aldosterone and Renin Levels: For suspected hyperaldosteronism.
- Plasma Metanephrines: Screen for pheochromocytoma.
- Renal Imaging: Evaluate for renal artery stenosis if renovascular hypertension is suspected.
Management
Lifestyle Modifications
- Weight Loss: Reduces BP by ~1 mm Hg per kg lost.
- Diet: The DASH diet (high in fruits, vegetables, and low-fat dairy) can lower BP by up to 11 mm Hg.
- Sodium Reduction: Aim for <1500 mg/day or at least <2400 mg/day.
- Physical Activity: 90–150 minutes of aerobic exercise per week, reducing BP by 4–8 mm Hg.
- Alcohol Moderation: ≤2 drinks per day for men, ≤1 drink per day for women.
Pharmacologic Therapy
- First-Line Medications:
- Thiazide Diuretics: Preferred for initial therapy; reduce fluid volume and peripheral resistance.
- ACE Inhibitors (ACEIs) / ARBs: Preferred in patients with diabetes, chronic kidney disease, or heart failure.
- Calcium Channel Blockers (CCBs): Beneficial for African American patients and older adults.
- Beta-Blockers: Not first-line for hypertension alone, but used in heart failure or post-MI patients.
- Indications for Therapy:
- Stage 1 Hypertension: Start medication if the patient has a history of cardiovascular disease or an ASCVD risk ≥10%.
- Stage 2 Hypertension: Start medication for all patients, regardless of ASCVD risk.
- Resistant Hypertension: Defined as BP ≥130/80 mm Hg despite using three antihypertensives at optimal doses, including a diuretic. Often managed with aldosterone antagonists (e.g., spironolactone) and evaluation for secondary causes.
Complications
- Cardiovascular: Left ventricular hypertrophy, coronary artery disease, heart failure.
- Cerebrovascular: Stroke and transient ischemic attacks.
- Renal: Nephrosclerosis and chronic kidney disease.
- Retinopathy: Ranging from mild AV nicking to papilledema in malignant hypertension.
Key Points
- Hypertension Classification: Defined as BP ≥130/80 mm Hg, with Stage 1 and Stage 2 categories guiding treatment.
- Diagnosis: BP measurement is essential, with confirmation via ABPM or home monitoring for accurate diagnosis.
- Management:
- Lifestyle Modifications: Essential for all patients, focusing on diet, exercise, and sodium reduction.
- Pharmacologic Therapy: Includes thiazide diuretics, ACEIs/ARBs, and CCBs as first-line agents.
- Resistant Hypertension: Evaluate for secondary causes and consider adding aldosterone antagonists.
- Complications: Hypertension increases the risk of cardiovascular disease, chronic kidney disease, stroke, and hypertensive retinopathy.
- Emergencies:
- Hypertensive Emergency: BP ≥180/120 mm Hg with end-organ damage requires immediate treatment with IV antihypertensives.
- Hypertensive Urgency: BP ≥180/120 mm Hg without end-organ damage, managed with oral antihypertensives.