Resistant Hypertension: Epidemiology, Mechanisms and Contemporary Therapeutic Strategies

esistant hypertension (RH), defined as uncontrolled blood pressure on three or more antihypertensive agents (including a diuretic) or controlled blood pressure on four or more, poses a major clinical challenge.It disproportionately drives adverse cardiovascular outcomes, including stroke, heart failure and chronic kidney disease.Accurate diagnosis first requires distinguishing true RH from pseudo-resistance, which stems from inaccurate measurement, poor medication adherence and clinical inertia.The pathophysiology is multifactorial, driven by mechanisms such as sympathetic nervous system overactivity, renin-angiotensin-aldosterone system dysregulation, obesity and obstructive sleep apnoea.Consequently, effective management extends beyond mere drug intensification.It demands a comprehensive strategy that addresses lifestyle factors, ensures therapeutic adherence and treats secondary causes.For eligible patients, device-based therapies, such as renal denervation, are emerging as valuable adjuncts to pharmacological treatment.This article synthesizes the current understanding of RH's epidemiology, pathophysiology and diagnostic workup.It also critically examines the evolving landscape of integrated therapeutic strategies, discussing on-going controversies and future research directions to improve patient outcomes.Hypertension affects over 1.4 billion adults worldwide and remains the leading modifiable risk factor for global cardiovascular (CV) morbidity and mortality.It is responsible for an estimated 10.8 million deaths annually and contributes significantly to the global burden of ischaemic heart disease, stroke, heart failure and chronic kidney disease (CKD). 1 Despite the availability of safe, effective antihypertensive therapies, a substantial proportion of patients exhibit persistent blood pressure (BP) elevation despite multi-drug treatment, a condition termed resistant hypertension (RH).This particularly challenging subset is often associated with poor BP control rates, high CV risk and substantial healthcare utilization.This comprehensive article examines the current understanding of RH from epidemiological patterns and pathophysiological mechanisms to diagnostic challenges and evolving therapeutic strategies.We critically evaluate the evidence base for contemporary management approaches and discuss future directions for improving outcomes in this high-risk patient population. Definition and terminologyThe American Heart Association (AHA) and the European Society of Hypertension (ESH) define RH as uncontrolled BP that remains elevated above goal despite adherence to an optimal triple-drug regimen that includes:• a renin-angiotensin-aldosterone system (RAAS) blocker (an angiotensin-converting enzyme [ACE] inhibitor or angiotensin receptor blocker)• a calcium channel blocker (CCB)• a thiazide/thiazide-like diuretic, wherein all agents have been administered at maximum or maximally tolerated doses and at the appropriate dosing frequency (Table 1).2,3 Controlled RH refers to BP at target levels while receiving four or more agents, whereas refractory hypertension denotes uncontrolled BP despite ≥5 antihypertensives, including a diuretic and a mineralocorticoid receptor antagonist (MRA). 2 The term RH includes both the subset of patients with hypertension, wherein BP is either controlled or uncontrolled, depending on the number of antihypertensive agents used.Patients with difficult-to-treat hypertension are often referred to as patients with 'resistant' or 'refractory' hypertension.2 Until recently, refractory hypertension was not historically differentiated from RH. Refractory hypertension, an extreme phenotype of antihypertensive treatment failure, has been defined as hypertension uncontrolled with the use of five or more antihypertensive agents, including a long-acting thiazide diuretic and an MRA. 4 Review Hypertension Heart International EpidemiologyRH represents a significant global health problem, with estimates suggesting that between 100 and 500 million individuals worldwide may be affected.2 This wide range reflects differences in diagnostic criteria, study methodologies and population characteristics across regions.In a comprehensive meta-analysis that included 91 cohort and cross-sectional studies involving more than 3.2 million patients with hypertension, the prevalence of RH was estimated to be approximately 10%. 5 Data suggest that the prevalence of RH is around 8.5-20% among US adults with hypertension.[6][7][8] Insights from the largest analysis of patients with RH (Cardiovascular Quality Improvement and Care Innovation Consortium [CV-QUIC]) reported a prevalence of RH to be 8.5% using the contemporary BP cutoff of 130/80 mmHg.7 Contemporary data from the National Health and Nutrition Examination Survey (NHANES) found that 15.9% of adult patients with hypertension met the criteria for RH, highlighting the widespread impact of this entity.9 The burden of RH is particularly pronounced in low-and middle-income countries, where the prevalence of hypertension is rising rapidly and control rates remain suboptimal.Data from the Jaipur Heart Watch study in India reported the prevalence of RH to be 19.4%. 10 RH is more common among older adults, males, individuals of African ancestry and those with comorbid metabolic syndromes or CKD.Data from the Research Action for Health Network (REACHnet) reported that patients with RH had a significantly higher prevalence of diabetes, dyslipidaemia, coronary artery disease, stroke, heart failure with preserved ejection fraction, heart failure with reduced ejection fraction, myocardial infarction (MI), CKD, sleep apnoea and other comorbidities when compared with patients with controlled hypertension.8 RH carries a significant clinical burden, as these patients are at greater risk for target-organ damage, including left ventricular hypertrophy, diastolic dysfunction, carotid intimal-medial thickening and microalbuminuria.11 Patients with RH have a twofold increased risk of CV disease events compared with patients whose hypertension is responsive to treatment.Longitudinal cohort studies demonstrate that RH confers an elevated risk of MI (hazard ratio [HR]: 1.47), stroke (HR: 1.42), heart failure (HR:1.70) and all-cause mortality (HR: 1.33) compared with controlled hypertension.12 RH significantly accelerates renal decline, conferring an increased risk for advanced CKD and nearly doubling the likelihood of progressing to end-stage renal disease.13 The burden of RH extends beyond individual patients to healthcare systems, with increased rates of hospitalizations, healthcare utilization and medication costs.14 Effective identification and management of RH is, therefore, a public health priority.