Management of mild aortic stenosis in patients undergoing coronary bypass surgery.

Many patients with coronary artery disease who require myocardial revascularization have asymptomatic mild aortic stenosis. Mild valvular obstruction is defined as a valvular area greater than 1.5cm, maximum transvalvar gradient less than 30mmHg, and maximum flow velocity lower than 3m/s. Even though the management of patients with obstructive aortic valvular disease has already been defined for most situations, and basically depends on symptoms, the approach with these patients remains controversial as noted in the literature. Aortic valvular replacement occurring simultaneously with myocardial revascularization surgery is considered a class IIb indication according to the guidelines elaborated by the committee on management of patients with valvular disease of the American College of Cardiology/American Heart Association . Some authors have recommended valvular replacement simultaneously with revascularization, reasoning that progression of the aortic stenosis to a critical stage takes approximately 5 to 8 years. Therefore, a significant percentage of these patients undergo early reintervention caused only by the valvular disease, being exposed to an increased risk mainly due to age, even with previous bypasses . Other factors associated with higher risk could be the following: the possible need for redissection of the internal mammary artery, the possible embolization of calcium in the damaged saphenous veins, and suboptimal myocardial protection caused by left ventricular hypertrophy. However, other groups have argued that the simultaneous procedure in a patient with mild asymptomatic stenosis imposes morbidity and mortality related to the use of prostheses. This reasoning is supported by the evidence that, in an 8-year interval (period of valvular disease evolution), mechanical valves account for 30% of this morbidity and mortality, and biological valves for 15% to 20% . In addition, mortality rates as high as 18% have been reported for the isolated procedure . In 1988, Horstkotte et al , assessing 142 patients with mild aortic stenosis, valvular area greater than 1.5cm, and undergoing catheterization because of other causes, found a 10-year survival of 92%, with a 22% evolution to critical aortic stenosis in 20 years and 38% in 25 years. In addition, 88% of the patients remained with mild obstruction after 10 years and 63% after 20 years. Recently, Otto et al 6 reported the evolution of aortic valvular disease and showed that an increase of 0.32m/s/ year exists in the velocity of transvalvar flow, with an increase in the mean gradient of approximately 3.9 to 7mmHg/ year, and a reduction in the valvular area of 0.12cm per year. Collins et al , retrospectively assessing a group of 44 previously revascularized patients undergoing reoperation because of symptomatic aortic stenosis, reported symptoms in 75% of the patients in a 5-year period, with a mean evolution of 68 months, even though some cases evolved in 8 months (evolution ranging from 8 to 164 months). Several attempts were made to find adequate and more reliable markers of progression of aortic stenosis. Davies et al 8 showed that the progression rate was not related to age, sex, or initial gradient, but to the valvular anatomy and the degree of calcification, rheumatic valvular disease being accompanied by less calcification and a lower progression rate. Wagner and Selker 9 showed that the valvular fibrotic degeneration with calcification was associated with more rapid progression and greater degrees of calcification, unlike the congenital valvular disease, bicuspid valve, which remained in an intermediate position. However, Fiore et al 3 showed more rapid progression in congenital valvular disease as compared with rheumatic disease, and this fact was supported by Hoshtkotte et al . In 1988, Lytle et al , in a retrospective study with a cohort of 294 patients undergoing myocardial revascularization surgery and aortic valvular replacement, simultaneously, found an in-hospital mortality of 4.4% with a 2-year survival of 89% and a 10-year survival of 52%. Another group of patients was reviewed in the following decade, and