THE CHANGING UNNATURAL HISTORY OF VALVULAR REGURGITATION

In the past 15 years three major advancements have improved the lot of our patients with left-sided valvular regurgitation. First, the concept that mitral and aortic regurgitation were similar volume overloading lesions has changed. Mitral regurgitation constitutes a nearly pure volume overload wherein the excess volume is ejected against relatively low pressure into the left atrium. On the other hand, aortic regurgitation represents a combined pressure and volume overload in which the excess volume being pumped is ejected against the relatively high pressure of the aorta. These differences in loading between mitral and aortic regurgitation produce a different response to operation. Afterload reduction after correction of aortic regurgitation increases ejection performance if it was decreased preoperatively. Conversely, afterload increases after mitral valve replacement, decreasing ejection performance. These differences make the left ventricle in mitral regurgitation less tolerant of preoperative dysfunction than the left ventricle in aortic regurgitation. Second, with respect to aortic regurgitation, reproducible indexes have been developed that identify when left ventricular dysfunction is present, leading to earlier operation in an attempt to avoid permanent ventricular dysfunction. In turn, earlier operation has led to a fall in operative mortality rate and an almost universal increase in left ventricular function if it was depressed preoperatively. Third, with regard to mitral regurgitation, recognition of the importance of the mitral valve apparatus in maintaining left ventricular function has led to an increased emphasis on chordal preservation during mitral valve operations. Early indicators suggest that these techniques will lead to improved postoperative left ventricular function, reduced operative mortality, and enhanced long-term survivor-ship for patients with mitral regurgitation. Thus, a change in concept regarding the pathophysiology of these lesions, a change in referral for patients with aortic regurgitation, and a change in operation for patients with mitral regurgitation have led to a favorable alteration in the unnatural history of left-sided valvular regurgitation.