Testing for Poorly Controlled Hypertension
For patients with poorly controlled hypertension, immediately confirm true treatment resistance using out-of-office blood pressure monitoring (home BP ≥135/85 mmHg or 24-hour ambulatory BP ≥130/80 mmHg), assess medication adherence through pharmacy records and pill counts, and systematically screen for secondary causes including obstructive sleep apnea, primary aldosteronism, chronic kidney disease, and renal artery stenosis. 1, 2, 3
Confirm True Treatment Resistance
Define resistant hypertension as office BP >140/90 mmHg (or >130/80 mmHg in patients with diabetes or chronic kidney disease) despite treatment with 3 or more antihypertensive medications at optimal doses, including a diuretic. 1
Exclude pseudoresistance first:
- Obtain out-of-office BP measurements using home monitoring (threshold ≥135/85 mmHg) or 24-hour ambulatory monitoring (threshold ≥130/80 mmHg) to exclude white coat hypertension 1, 3, 4
- Verify proper BP measurement technique: use validated automated upper arm cuff with appropriate cuff size, measure in both arms, and use the arm with higher readings for subsequent measurements 3, 4
- Assess medication adherence objectively through pharmacy records, pill counts, or electronic monitoring devices rather than relying on patient self-report 1, 2, 5
Systematic Screening for Secondary Causes
Screen for obstructive sleep apnea in all patients with resistant hypertension by asking about snoring, witnessed apnea, and excessive daytime sleepiness. This is one of the most common contributors to treatment resistance. 1, 2
Test for primary aldosteronism by measuring the aldosterone-to-renin ratio (ARR), particularly in patients with hypokalemia or those requiring 4 or more medications. This is the most common endocrine cause of resistant hypertension. 1, 2
Evaluate renal function by measuring serum creatinine and calculating creatinine clearance. Chronic kidney disease with clearance <30 mL/min is a frequent contributor to resistant hypertension and requires loop diuretics rather than thiazides. 1, 2
Consider renal artery stenosis in young females, patients with known atherosclerotic disease, those with worsening renal function after starting ACE inhibitors or ARBs, or those with an epigastric/upper abdominal bruit. Initial screening can use duplex ultrasound, though MRA, CT angiography, or renal scintigraphy may be needed if clinical suspicion is high. 1
Screen for pheochromocytoma if the patient has episodic hypertension accompanied by palpitations, diaphoresis, or headache. 1
Evaluate for Cushing's syndrome if physical examination reveals moon facies, central obesity, abdominal striae, or interscapular fat deposition. 1
Check for aortic coarctation by assessing for differential brachial or femoral pulses and listening for systolic bruits, particularly in younger patients. 1
Medical History and Physical Examination
Obtain detailed medication history including all prescription medications, over-the-counter drugs, and herbal supplements that may interfere with BP control (NSAIDs, decongestants, stimulants, licorice, oral contraceptives). 1, 2
Document cardiovascular risk factors including history of peripheral or coronary atherosclerotic disease (increases likelihood of renal artery stenosis), diabetes (predicts lack of BP control and requires lower BP goals), and obesity (common contributor to resistant hypertension). 1
Assess dietary sodium intake through detailed nutritional history, including salt added at the table, sodium in processed foods, and fast food consumption. High sodium intake is strongly linked to resistant hypertension. 1, 2
Laboratory and Diagnostic Testing
Initial screening tests should include: 1, 2
- Serum creatinine and estimated GFR
- Serum potassium
- Fasting glucose or HbA1c
- Lipid panel
- Urinalysis for proteinuria
- Aldosterone-to-renin ratio if clinically indicated
Document target organ damage: 1
- Obtain electrocardiogram to assess for left ventricular hypertrophy
- Consider echocardiography if LVH is suspected, as it supports diagnosis of poorly controlled hypertension and influences treatment goals
- Fundoscopic examination for hypertensive retinopathy
- Assessment for chronic kidney disease through creatinine clearance and proteinuria
Common Pitfalls to Avoid
Do not assume treatment failure without confirming adherence. Non-adherence is the primary cause of apparent resistant hypertension. Use objective measures rather than patient self-report. 2, 5
Do not overlook inadequate diuretic therapy. Nearly half of patients with resistant hypertension have suboptimal diuretic dosing or are not receiving appropriate diuretics for their level of renal function. Patients with CKD and creatinine clearance <30 mL/min require loop diuretics, not thiazides. 1, 5
Do not miss obstructive sleep apnea. This is one of the most common and treatable causes of resistant hypertension but is frequently overlooked. Screen all patients with resistant hypertension for symptoms. 1, 2
Do not fail to screen for primary aldosteronism. This condition is present in 10-20% of patients with resistant hypertension and is often missed because hypokalemia is not always present. 1, 2
Do not delay intensification of therapy once pseudoresistance and secondary causes are excluded. Therapeutic inertia—failing to intensify treatment when BP remains uncontrolled—is a major barrier to achieving BP goals. 1, 2
Follow-Up and Monitoring Strategy
Schedule follow-up every 2-4 weeks until BP control is achieved, then extend intervals to every 3-4 months once at goal. 1, 2, 3
Implement home BP monitoring to guide therapy adjustments and improve patient engagement. This provides more accurate assessment of BP control than office measurements alone. 1, 2
Consider team-based care involving physicians, nurses, pharmacists, and health coaches. Pharmacist-led interventions with home BP telemonitoring have shown superior results, with SBP reductions of 21.6 mmHg greater than usual care. 1, 2