The importance of magnesium status in the pathophysiology of mitral valve prolapse

Idiopathic mitral valve prolapse (IMVP) refers to the systolic displacement of one or both mitral leaflets into the left atrium, with or without mitral regurgitation. It is one of the most common forms of cardiac abnormalities among young people, especially in women. IMVP usually appears to be a benign condition and even capable of recovery. In a minority of cases IMVP may predispose to complications. The data suggest an autosomal dominant inheritance of IMVP that exhibits both sex- and age-dependent penetrance with variable expressivity and genetic heterogeneity. IMVP appear to be one form or aspect of latent tetany due to magnesium deficit (MDLT). The prevalence, latent nature, and symptomatology of these two conditions appear to be strictly similar. Primary magnesium (Mg) deficit may result from Mg deficiency (insufficient Mg intake) and Mg depletion (excessive urinary Mg loss). Constitutional factors (e.g. HLA-B35, type A behavior pattern) should be considered in the aetiology of Mg deficit (MD). MD may cause abnormal fibrosis, abnormalities in collagen synthesis as well as in the myocardium, capable of inducing mitral apparatus dyskinesia. MD is a part of a picture of metabolic abnormalities, alteration of immune and autonomic nervous systems, cardiac arrhythmias and thromboembolic phenomena in IMVP. Laboratory evaluation must involve plasma Mg, erythrocyte Mg, calcemia, calciuria, and daily magnesuria. Normal plasma Mg concentration does not rule out the diagnosis of primary chronic MD. The diagnosis of MD requires the oral Mg load test. Correction of symptomatology by this oral physiological Mg load (5 mg/kg/day) is the best proof that it was due to Mg deficiency. Mg therapy is essential and specific for IMVP. In the majority of cases MD is due to Mg depletion and the oral Mg supplementation must be combined with Mg-sparing diuretics or physiological doses of vitamin D. Partial "Mg analogues" (beta-blockers, verapamil, phenytoin) may prove to be useful in some cases.