Objective Primary aldosteronism (PA) is a potentially curable cause of hypertension associated with worse cardiovascular prognosis than blood pressure‐matched essential hypertension (EH). Effective targeted treatment for PA is available with the greatest benefit seen if treatment is started early, prior to the development of end‐organ damage. However, PA is currently substantially under‐diagnosed. The standard screening test for PA, the aldosterone‐to‐renin ratio (ARR), is performed infrequently in both primary and tertiary care. In contrast, ambulatory blood pressure monitoring (ABPM) is frequently utilized in the assessment of hypertension. The aim of this study was to compare ABPM parameters in hypertensive patients with and without PA, in order to identify features of ABPM associated with PA that can prompt screening. Study design Patients with PA (n = 55) were identified from a tertiary clinic specializing in the management of endocrine causes of hypertension whilst the controls (n = 389) were consecutive patients with hypertension but without a known diagnosis of PA who were referred for ABPM. Results In this study, PA patients were younger and had higher 24‐h, day, and night‐time blood pressure compared with controls despite similar number of antihypertensive medications. However, there was no significant difference in nocturnal dipping or day‐night blood pressure variability between the two groups. Conclusions An elevated ambulatory blood pressure in patients on multiple antihypertensives could suggest underlying PA but in the absence of other distinguishing features, ABPM could not reliably differentiate PA from other forms of hypertension. Routine biochemical screening for PA remained the most reliable way of detecting this treatable secondary cause of hypertension.

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Background: Primary aldosteronism (PA) has a reported prevalence of up to 30% in cases of resistant hypertension and is associated with worse cardiovascular outcomes than BP-matched essential hypertension (EH), but is substantially under-diagnosed due to the lack of specific symptoms and signs. Ambulatory blood pressure monitoring (ABPM) provides a non-invasive method for evaluating circadian BP variations, offers valuable prognostic information and may help to differentiate PA from EH in patients referred with non-specific hypertension for investigation. Aims: To compare AMBP parameters in hypertensive patients with established PA and those without, and correlate these parameters with cardiovascular outcomes. Methods: AMBP readings were evaluated retrospectively in 453 patients assessed at Monash Heart (the largest cardiology service in Victoria, Australia). Patient demographics, screening aldosterone and renin concentrations and medications were retrieved from medical records. 414 hypertensive patients with presumed EH and 39 PA patients were identified and their cardiovascular events (myocardial infarction, left ventricular hypertrophy, coronary artery disease, atrial fibrillation) were recorded. All parameters are reported as the median [interquartile range], unless stated otherwise. Statistical significance was set at p<0.05. Results: Compared to hypertensive patients who are presumed to have EH, PA patients were significantly younger (55 yr [50, 66] vs 63 yr [53, 72]), had higher systolic (149 mmHg [134, 156] vs 133 mmHg [124, 145]) and diastolic BP readings (87 mmHg [82, 92] vs 75 mmHg [68, 82]) with similar patterns observed for average daytime and night-time BP. BP load (% daytime and night-time SBP/DBP readings over 135/85 and 120/70 mmHg, respectively) was significantly higher for both systolic and diastolic in PA (83% [61, 92] and 57% [35, 76]) compared with the non-PA group (48% [23, 75] and 14% [5, 35]). 77% of patients with PA (30/39) had loss of physiological nocturnal BP dipping compared with 44% of the non-PA group (184/414). Rates of cardiovascular events were similar in both groups but may be confounded by the retrospective nature of this study and lack of long-term follow-up. Conclusion: In our study, PA is associated with a distinctive 24-hour BP profile, including a significant increase in BP load and loss of nocturnal BP dipping which are known risk factors for adverse cardiovascular events. A prospective study is needed to better define AMBP parameters in PA and evaluate their ability to unveil underlying PA amongst hypertensive patients.