The renin-angiotensin-aldosterone system (RAAS) plays a vital role in cardiovascular homeostasis by regulating blood pressure, salt, and water balance. The kidneys produce renin which converts angiotensinogen to angiotensin-1 (AT-I) and angiotensin-converting enzyme (ACE) to angiotensin-II (AT-II). AT-II binds to receptors in the adrenal cortex to release aldosterone. AT-II and aldosterone promote water and salt retention, vascular tone, and myocardial contractility. These physiological changes raise blood pressure and circulation. Reduced renal perfusion pressure sensed by baroreceptors and the sympathetic nervous system's β-adrenergic receptors trigger renin release and RAAS activation. RAAS restores hemodynamic stability in pathological states associated with low perfusion. This adaptive response is important for restoring perfusion and hemodynamic stability, but prolonged RAAS activation has deleterious effects on the cardiovascular system. Long-term mineralocorticoid exposure has been linked to left ventricular hypertrophy (LVH) and remodeling. AT-II activates fibroblasts and cardiac myocytes to promote cardiac remodeling. Blocking RAAS can eliminate the long-term negative effects of RAAS activation. Direct renin inhibitors, ACE inhibitors, angiotensin receptor blockers, and aldosterone antagonists are RAAS blockers. RAAS blockade improves mortality and hospitalization in systolic heart failure and acute myocardial infarction. RAAS blockade has not demonstrated the same benefits in other cardiac populations, such as those with preserved ejection fraction. Hypertrophic cardiomyopathy (HCM) causes LVH and asymmetric septal hypertrophy. When the outflow tract gradient exceeds 30 mmHg and is associated with septal hypertrophy, it is known as obstructive HCM. Dyspnea on exertion, syncope, and exertional angina are symptoms of HCM. RAAS activation worsens LVH by increasing blood pressure and by directly affecting cardiac myocytes with AT-II and aldosterone. RAAS blockade reverses myocardial fibrosis and slows HCM progression in animal models. We performed a meta-analysis of randomized clinical trials to further investigate the potential benefit of RAAS blockade in HCM patients. Although our findings included significant results for some of the RAAS blockade agents, these findings were not consistent throughout all the studies. Mavacamten, one of the newest treatments, has shown promising outcomes.
Keywords: functional status; left ventricular diastolic dysfunction; left ventricular hypertrophy (lvh); raas inhibitors; systematic review.
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