Do Vasodilators Interfere with Left Ventricular Remodeling in Chronic Mitral Regurgitation?

Abstract

The influence of vasodilators in the natural history of mitral regurgitation is controversial. If, on the one hand, they may really interfere, on the other, they may mask left ventricular myocardial dysfunction.Three phases comprise the natural history of mitral regurgitation. In the first, increased atrial compliance and eccentric ventricular hypertrophy are observed in association with diastolic normotension. In the second phase, a transition phase, a slow increase in diastolic and left chamber pressures is observed. In the third phase, handicapping symptoms occur due to failure in compensating mechanisms and elevation in the systolic and pulmonary pressures.It is estimated that up to 82% of the patients with mitral regurgitation due to prolapse progress to surgical indication in a 10-year period, which is equivalent to a 20% rate of surgical indication per year 1 . Functional class (III or IV, New York Heart Association), advanced age, and ventricular dysfunction correlate with a greater mortality rate 1,2 .In regard to the qualification of the indicators of natural history progression in patients with asymptomatic chronic mitral regurgitation, no uniformity exists. Variations in the systolic diameter between 45 and 55 mm 2,3 , in the diastolic diameter above 70 mm 3 , or correlations between cavitary increase and body surface 4 are not satisfactory. However, signals of reduction in left ventricular function draw attention to the advanced character of the disease [1][2][3][4] .The type of drug, its dosage, and the period of time during which it is used influence the vasodilator effect on mitral regurgitation. Greenberg et al 5 , using hydralazine, and Schön et al 6 , using quinapril, reported a reduction in left ventricular diameter and improvement of symptoms. However, this behavior has not been confirmed by other researchers 7,8 .In this regard, we studied 47 patients with oligosymp- tomatic chronic mitral regurgitation, of whom 26 received enalapril maleate and 21 received placebo, in a randomized double-blind protocol. We observed a reduction in left ventricular and left atrial systolic and diastolic diameters 9 after 12 months in the patients who received enalapril maleate as compared with those who received placebo. How does one explain the alterations observed with the use of the vasodilator in this situation, in which an elevation of the preload and normality or reduction of the afterload exist? Hemodynamic alterations of the mitral defluxion volume, of the regurgitant volume, of the regurgitation orifice and fraction, and preservation of the systolic volume in patients who used enalapril could justify the reduction in the left cavity 9,10 . Left ventricular ejection fraction did not change with the use of the vasodilator, either at rest and on maximum exertion 9 .Hemodynamic improvement may cause alterations in ventricular geometry and reduction in the degree of mitral valve reflux. Cardiac remodeling results from alterations in gene, molecular, cellular, and interstitial expression, manifesting as c...