VARIABILITY OF THE VENTRICULAR RESPONSE IN ATRIAL-FIBRILLATION AND PROGNOSIS IN CHRONIC NONISCHEMIC MITRAL REGURGITATION

Although reduced heart rate (HR) variability during sinus rhythm is as sociated with an adverse prognosis in a variety of clinical settings, the significance of measures of variability of the ventricular respons e in atrial fibrillation (AF) requires clarification. AF is common amo ng patients with chronic severe mitral regurgitation (MR) and potentia lly limits the application of HR variability techniques in this popula tion. Therefore, this study examined the physiologic correlates and pr ognostic significance of measures of HR variability in 21 patients wit h nonischemic causes of chronic severe MR who had chronic AF and under went 24-hour ambulatory electrocardiography as part of a prospective study of the natural history of regurgitant valvular heart disease. Pa tients were followed for up to 9.1 years and end points of mortality a nd progression to mitral valve surgery were tabulated. Time- and frequ ency-domain measurements of high-, low-, and ultra- low-frequency HR v ariability were computed and compared with resting ventricular functio n by radionuclide cineangiography and outcome. All measures of HR vari ability were covariate (pair-wise r values between 0.48 and 0.99, all p values <0.03), and none of the variables was significantly related t o age, ventricular premature complex (VPC) density, or right or left v entricular ejection fraction. Reductions in time-domain measurements o f ultra-low- and high-frequency HR variability were significant predic tors of the combined risk of mortality or requirement for mitral valve surgery (p = 0.02 and p = 0.05, respectively). Thus, although measure s of HR variability in AF with MR are not associated with age, VPC den sity, or ventricular performance, variability of the ventricular respo nse in chronic Ar is inversely related to risk in patients with chroni c severe MR.