Variability of the ventricular response in atrial fibrillation and prognosis in chronic nonischemic mitral reurgitation

Abstract

Although reduced heart rate (HR) variability during sinus rhythm is associated with an adverse prognosis in a variety of clinical settings, the significance of measures of variability of the ventricular response in atrial fibrillation (AF) requires clarification. AF is common among patients with chronic severe mitral regurgitation (MR) and potentially limits the application of HR variability techniques in this population. Therefore, this study examined the physiologic correlates and prognostic significance of measures of HR variability in 21 patients with nonischemic causes of chronic severe MR who had chronic AF and underwent 24-hour ambulatory electrocardiography as part of a prospective study of the natural history of regurgitant valvular heart disease. Patients were followed for up to 9.1 years and end points of mortality and progression to mitral valve surgery were tabulated. Time- and frequency-domain measurements of high-, low-, and ultralow-frequency HR variability were computed and compared with resting ventricular function by radionuclide cineangiography and outcome. All measures of HR variability 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 to age, ventricular premature complex (VPC) density, or right or left ventricular ejection fraction. Reductions in time-domain measurements of ultra-low- and high-frequency HR variability were significant predictors of the combined risk of mortality or requirement for mitral valve surgery (p = 0.02 and p = 0.05, respectively). Thus, although measures of HR variability in AF with MR are not associated with age, VPC density, or ventricular performance, variability of the ventricular response in chronic AF is inversely related to risk in patients with chronic severe MR.