1.9 Hypertension: Classification, Diagnosis & Secondary Causes
Key Takeaways
- Hypertension is a 5% blueprint subsection cross-listed between Cardiovascular Disease and Nephrology and Urology, making it the single largest topic on the exam.
- Essential hypertension, renal and renovascular causes, coarctation of the aorta, hypertensive urgency and emergency, and undifferentiated hypertension are the enumerated blueprint topics.
- Ambulatory or home blood pressure monitoring is required to confirm the diagnosis and to identify white-coat and masked hypertension.
- Resistant hypertension is uncontrolled pressure on three agents including a diuretic, or controlled pressure requiring four agents, and warrants secondary evaluation.
- Adrenal vein sampling is required before adrenalectomy in most patients with primary aldosteronism because an incidentally imaged nodule may not be the source of excess aldosterone.
Last updated: August 2026
Hypertension and dyslipidemia are the two most prevalent modifiable risk factors for atherosclerotic cardiovascular disease (ASCVD), heart failure, stroke, and chronic kidney disease. This section provides an in-depth, board-focused synthesis of the ACC/AHA guidelines for blood pressure classification, secondary hypertension workup, hypertensive crises management, statin benefit groups, and non-statin lipid-lowering therapies.
1. Hypertension: Classification & Diagnostic Criteria
2017 ACC/AHA Blood Pressure Categories
Blood pressure classification is based on the average of >=2 careful readings obtained on >=2 separate occasions:
- Normal BP: Systolic < 120 mmHg AND Diastolic < 80 mmHg.
- Elevated BP: Systolic 120–129 mmHg AND Diastolic < 80 mmHg.
- Stage 1 Hypertension: Systolic 130–139 mmHg OR Diastolic 80–89 mmHg.
- Stage 2 Hypertension: Systolic >= 140 mmHg OR Diastolic >= 90 mmHg.
Out-of-Office Blood Pressure Monitoring
- Ambulatory Blood Pressure Monitoring (ABPM; Gold Standard): 24-hour mean >= 125/75 mmHg, Daytime (awake) mean >= 130/80 mmHg, or Nighttime (asleep) mean >= 110/65 mmHg diagnostic of HTN. Identifies non-dipping status (<10% nocturnal BP dip), which confers heightened cardiovascular and stroke risk.
- Home Blood Pressure Monitoring (HBPM): Mean >= 130/80 mmHg diagnostic of HTN.
- Phenotypes:
- White-Coat Hypertension: Elevated office BP (>=130/80) but normal out-of-office BP (<130/80 on ABPM/HBPM). No drug therapy indicated; manage with lifestyle and annual ABPM.
- Masked Hypertension: Normal office BP (<130/80) but elevated out-of-office BP (>=130/80). Carries cardiovascular risk equivalent to sustained HTN; requires pharmacologic therapy.
Initial Pharmacotherapy & Target Goals
- Treatment Thresholds:
- Stage 1 HTN (130-139/80-89) + 10-year ASCVD risk <10%: 3 to 6 months of non-pharmacologic lifestyle modification.
- Stage 1 HTN + 10-year ASCVD risk >=10%, or Stage 2 HTN (>=140/90 mmHg): Immediate pharmacotherapy + lifestyle.
- Stage 2 HTN with BP >20/10 mmHg above target (e.g., >=150/90 mmHg): Initiate two first-line antihypertensive agents of different classes (e.g., CCB + ACEi/ARB or Thiazide-like diuretic + ACEi/ARB).
- Target Blood Pressure Goal: < 130/80 mmHg for all adult populations with confirmed hypertension, including elderly patients and those with diabetes, CKD, or CAD (supported by the SPRINT trial).
First-Line Antihypertensive Classes
- Thiazide-Like Diuretics: Chlorthalidone (12.5-25 mg daily) or Indapamide preferred over Hydrochlorothiazide (HCTZ 25-50 mg daily) due to longer half-life (40-60 hours) and superior clinical trial evidence in preventing CV events (ALLHAT trial). Adverse effects: Hypokalemia, hyponatremia, hyperuricemia (precipitates gout flares), hyperglycemia, hypercalcemia.
- Dihydropyridine CCBs: Amlodipine (2.5-10 mg daily), Nifedipine ER. Potent vasodilators. Adverse effects: Dose-dependent peripheral dependent edema (pre-capillary arteriolar vasodilation; reduced by adding an ACEi/ARB which induces post-capillary venodilation), reflex tachycardia, gingival hyperplasia.
- ACE Inhibitors / ARBs: Lisinopril, Enalapril / Losartan, Valsartan. First-line for diabetes with albuminuria, CKD with proteinuria, and HFrEF. Adverse effects: Hyperkalemia, acute rise in serum creatinine (up to 30% increase is hemodynamically expected and acceptable), dry cough (ACEi, due to substance P and bradykinin accumulation), angioedema. Strictly contraindicated in pregnancy and bilateral renal artery stenosis. Never combine an ACEi and an ARB (increases renal failure and hyperkalemia without CV benefit; ONTARGET trial).
- Compelling Indications:
- Black Adults without CKD/HF: Initial therapy should include a Thiazide-like diuretic and/or a CCB (superior BP lowering and stroke reduction compared to ACEi monotherapy; ALLHAT trial).
- Chronic Kidney Disease with Albuminuria (UACR >=300 mg/g or 30-299 mg/g): ACE inhibitor or ARB is Class 1 to slow renal progression.
2. Secondary Hypertension: Diagnostic Workup
Secondary hypertension accounts for ~10% of adult hypertension. Screen when patients present with: Resistant Hypertension (uncontrolled BP despite >=3 antihypertensive medications of different classes at maximal doses, one of which is a diuretic; or controlled on >=4 medications), sudden onset <30 years, abrupt loss of BP control in a previously stable patient, or unprovoked hypokalemia.
| Etiology | Clinical Clues | Initial Screening Test | Confirmatory / Localization Test | Definitive Management |
|---|---|---|---|---|
| Primary Aldosteronism (Conn Syndrome / Bilateral Hyperplasia) | Resistant HTN, spontaneous or diuretic-induced hypokalemia, metabolic alkalosis | Plasma Aldosterone Concentration (PAC) to Plasma Renin Activity (PRA) Ratio (ARR): ARR > 20 (with PAC > 15 ng/dL) | Confirmatory: 24h urinary aldosterone during oral sodium load or IV saline suppression test. Localization: Adrenal CT scan + Adrenal Venous Sampling (AVS) | Unilateral adenoma: Laparoscopic adrenalectomy. Bilateral hyperplasia: MRA (Spironolactone or Eplerenone) |
| Renal Artery Stenosis (RAS) | Flash pulmonary edema, refractory HTN, abdominal bruit, unexplained rise in serum Cr >30% after starting ACEi/ARB | Renal Duplex Ultrasonography, CT Angiography, or MR Angiography of renal arteries | Renal catheter angiography | Fibromuscular Dysplasia (FMD) in young women: Percutaneous balloon angioplasty without stent. Atherosclerotic RAS in older men: Medical therapy (stenting has no benefit over GDMT; ASTRAL/CORAL) |
| Pheochromocytoma / Paraganglioma | Paroxysmal "5 Ps": Pressure (severe HTN), Pain (headache), Perspiration (diaphoresis), Palpitations, Pallor | Plasma free metanephrines (high sensitivity) or 24-hour urine fractionated metanephrines | Abdominal/pelvic CT or MRI, 123I-MIBG scan, or 68Ga-DOTATATE PET | Preoperative: Alpha-blockade FIRST (Phenoxybenzamine or Doxazosin for 10-14 days), followed by Beta-blockade for reflex tachycardia. Surgical adrenalectomy. (Never start Beta-blocker before Alpha-blocker!) |
| Cushing Syndrome | Central obesity, moon facies, buffalo hump, purple abdominal striae, proximal muscle weakness | 24-hour urinary free cortisol, late-night salivary cortisol, or 1-mg overnight dexamethasone suppression test | Serum ACTH level, High-dose dexamethasone test, Pituitary MRI / Adrenal CT | Transsphenoidal resection of pituitary adenoma or adrenalectomy |
| Obstructive Sleep Apnea (OSA) | Loud snoring, witnessed apneas, daytime somnolence, resistant HTN, obesity | In-lab Polysomnography or Home Sleep Apnea Testing (AHI >= 5 events/hour) | Sleep study severity quantification | Nocturnal Continuous Positive Airway Pressure (CPAP), weight loss |
| Coarctation of the Aorta | Upper extremity HTN with diminished/delayed femoral pulses (brachial-femoral pulse delay), lower extremity SBP >20 mmHg lower than arms | 12-lead ECG (LVH), Chest X-ray (rib notching on ribs 3-8, 'figure-of-3' aortic sign), Echocardiogram | CT Angiography or MR Angiography of the chest | Percutaneous balloon angioplasty +/- stent or surgical resection |
Test Your Knowledge
A 48-year-old woman with a history of resistant hypertension presents for evaluation. She is currently taking Chlorthalidone 25 mg daily, Amlodipine 10 mg daily, and Lisinopril 40 mg daily. Her seated office blood pressure is 154/96 mmHg. Laboratory studies reveal: serum sodium 142 mEq/L, serum potassium 3.1 mEq/L, serum bicarbonate 30 mEq/L, and serum creatinine 0.8 mg/dL. Her plasma aldosterone concentration (PAC) is 28 ng/dL and plasma renin activity (PRA) is 0.4 ng/mL/h, resulting in a PAC/PRA ratio of 70. A 24-hour urine sodium loading test confirms autonomous aldosterone excretion. High-resolution CT scan of the abdomen reveals a normal left adrenal gland and a 1.2-cm right adrenal nodule. What is the most appropriate next step prior to surgical intervention?
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