What is the most common cause of resistant hypertension?

Most Common Causes of Resistant Hypertension

Poor medication adherence is the most common cause of resistant hypertension, accounting for approximately 50% of cases of apparent treatment-resistant hypertension. 1

Definition of Resistant Hypertension

Resistant hypertension is defined as blood pressure that remains above goal despite concurrent use of 3 antihypertensive agents of different classes (ideally including a diuretic) at optimal doses, or when 4 or more medications are needed to achieve blood pressure control 1.

Primary Causes of Resistant Hypertension

1. Pseudoresistance (Most Common)

• Poor medication adherence: Accounts for approximately 50% of apparent treatment-resistant hypertension cases 1, 2
• White coat effect: Affects 20-30% of patients with resistant hypertension 1
• Improper blood pressure measurement technique: Using too small a cuff or measuring before allowing the patient to sit quietly 1

2. Lifestyle Factors

• Excessive dietary sodium: Common in patients with resistant hypertension, with average intake exceeding 10g per day 1
• Obesity: Associated with more severe hypertension and need for increased number of medications 1
• Heavy alcohol intake: Significantly reduces likelihood of blood pressure control 1

3. Secondary Causes of Hypertension

• Obstructive sleep apnea: A frequent contributor to resistant hypertension 1
• Primary aldosteronism: Common among patients with resistant hypertension 3
• Chronic kidney disease: Impairs sodium excretion and complicates hypertension management 1
• Renal artery stenosis: Can lead to blood pressure refractory to therapy 1

4. Medication-Related Causes

• Interfering medications: NSAIDs, decongestants, oral contraceptives, stimulants, and certain herbal compounds can interfere with blood pressure control 1, 3
• Suboptimal medication regimens: Not using complementary medications or appropriate diuretics 1

Diagnostic Approach

1. Confirm true resistance:

   • Verify medication adherence (consider directly observed therapy) 2
   • Obtain out-of-office blood pressure measurements to exclude white coat effect 4
   • Ensure proper blood pressure measurement technique 1

2. Evaluate for contributing factors:

   • Review medication list for interfering substances 1
   • Assess dietary sodium intake and alcohol consumption 1
   • Screen for obstructive sleep apnea, especially in obese patients 1

3. Screen for secondary causes:

   • Evaluate for primary aldosteronism, chronic kidney disease, and renal artery stenosis 3

Management Approach

1. Address adherence issues:

   • Simplify regimen with single-pill combinations when possible 4
   • Educate patients about importance of medication adherence 1

2. Optimize lifestyle modifications:

   • Sodium restriction (<2g/day) 1
   • Weight loss for overweight/obese patients 1
   • Limit alcohol consumption 1

3. Optimize medication regimen:

   • Ensure one of the medications is an appropriate diuretic 1
   • Include complementary drug classes (ACE inhibitor/ARB, calcium channel blocker, diuretic) 4
   • Add mineralocorticoid receptor antagonist (spironolactone) as fourth-line agent 4

Clinical Pearls

• Non-adherence is extremely common and often underestimated; studies show approximately 50% of patients with apparent resistant hypertension are either completely or partially non-adherent 2
• Polypharmacy itself can contribute to non-adherence, creating a vicious cycle in resistant hypertension management 1
• Thiazide-like diuretics (particularly chlorthalidone) may be more effective than hydrochlorothiazide in resistant hypertension 5
• Spironolactone has shown significant benefit in resistant hypertension regardless of aldosterone levels 5

Remember that identifying and addressing the underlying cause(s) of resistant hypertension is crucial for achieving blood pressure control and reducing cardiovascular risk.