Efficacy of an angiotensin II receptor antagonist in managing hyperaldosteronism

Treatment of primary aldosteronism: Where are we now?

Primary aldosteronism (PA) is an important cause of secondary hypertension, is being increasingly diagnosed and may account for more than 10% of hypertensive patients, both in primary care and in referral centers. Aldosterone excess is associated with adverse cardiovascular, renal and metabolic effects that are in part hypertension-independent. Laparoscopic adrenalectomy remains the mainstay of treatment for unilateral forms of PA, whereas medical treatment is recommended for bilateral forms of PA. However, a favourable surgical outcome depends on several factors and many patients are not suitable for this treatment. On the other hand, surgery in patients considered to have bilateral PA may contribute to better blood pressure control. In this review, established and novel strategies for the management of different types of PA are discussed.

Prediction of successful outcome in patients with primary aldosteronism

Primary aldosteronism is one of the most common causes of secondary hypertension. In recent years the prevalence has risen dramatically, from 1% to 14% of all hypertensive patients. This has been largely attributed to an increase in diagnosis. Primary aldosteronism is characterized by hypertension with or without hypokalemia and a high plasma aldosterone concentration (PAC) with a concurrent low plasma renin activity (PRA). The most common subtypes of primary aldosteronism are aldosterone-producing adenoma (42%) and bilateral idiopathic hyperaldosteronism (58%). Other less common subtypes (<1%) are glucocorticoid-remediable aldosteronism, and unilateral primary hyperplasia. Current treatment for primary aldosteronism relies on accurate subtype distinction and assessment of unilateral versus bilateral disease. Bilateral idiopathic hyperaldosteronism is best managed pharmacologically and improves with the use of aldosterone receptor antagonists. Combined treatment with sodium-channel blockers and calcium-channel blockers has also shown satisfactory results. Glucocorticoid-remediable aldosteronism responds well to treatment with low-dose glucocorticoids. Aldosterone producing adenoma and unilateral adrenal hyperplasia are appropriately treated with laparoscopic adrenalectomy. Following adrenalectomy blood pressure improves in 98% of these patients, but only about 33% require no further antihypertensive medication. Identifying the subgroups that will most benefit from adrenalectomy is paramount to formulating individual treatment strategies. In the past, treatment focused mainly on the correction of hypertension and electrolyte disturbances. Now, with accumulating evidence of the detrimental effects of aldosterone to the myocardium, vascular endothelium and kidneys, treatment also focuses on normalizing aldosterone levels or blocking aldosterone action at the receptor level. Therefore, it is essential to accurately identify the specific subtype of primary aldosteronism in order to select optimal treatment and to achieve successful patient outcomes.

The pharmacological treatment of primary aldosteronism

Aldosterone is increasingly considered to have a fundamental role in the pathophysiology of cardiovascular disease. Primary aldosteronism is a much more common cause of secondary hypertension than once suspected, accounting for approximately 10% of cases. Screening for primary aldosteronism should be considered even in the presence of normokalaemia. The non-classical effects of aldosterone, some of which are transcription-independent, may be of similar or greater importance than its traditional effects on the kidney. Treatment of primary aldosteronism should be specific and aim to ameliorate all hormone-related effects of aldosterone, not just the most obvious manifestation of hypertension. Mineralocorticoid antagonism, shown to lead to significant additional survival advantage in heart failure, offers the best prospect for achieving therapeutic goals. For the increasing proportion of patients with primary aldosteronism suitable for long-term medical treatment, mineralocorticoid receptor blockade (better tolerated with eplerenone) should be considered the most appropriate choice of treatment, pending the development of better alternatives.

Aldosterone: a risk factor for vascular disease

Blockade of the renin-angiotensin-aldosterone system with angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor antagonists has resulted in beneficial effects in essential hypertensive patients. However, occurrence of cardiovascular events has not been appropriately controlled beyond a certain percentage. One reason could be the effects of aldosterone, the final component of the system. The aldosterone escape phenomenon could explain undesirable outcomes observed in hypertensive patients even under treatment with ACE inhibitors or angiotensin antagonists. Aldosterone has direct effects on the vasculature and has been associated with vascular smooth muscle cell hypertrophy, endothelial dysfunction, cardiac fibrosis, proteinuria, and renal vascular injury. Animal models and clinical trials have proven the benefit of aldosterone receptor antagonism. With increased recognition of the prevalence of hyperaldosteronism in patients thought to have "essential" hypertension, the use of drugs that block aldosterone action may become more widespread and protect the vasculature from the deleterious effects of aldosterone.