Left Ventricular Relaxation Abnormality Is Detectable by Analysis of the Relaxation Time Constant in Patients With Atrial Fibrillation

Abstract

here has been increasing interest in atrial fibrillation (AF) in the fields of cardiology and cardiac surgery, 1 partly because of its high prevalence and partly because of the high morbidity associated with the risk of cerebral infarction. Unlike regular beats, indices of left ventricular (LV) contractility in arrhythmic beats, whether they may be load-dependent (peak LV dP/dt, the maximum rate of rise of LV pressure) 2 or load-independent (Emax), 3 have been shown to be constantly changing dependently on the force -interval relationship, 4 as well as on the FrankStarling relationship. 5 The force -interval relationships include the relations between indices of each beat and RR2 (the directly preceding RR intervals), which are referred to as mechanical restitution, and those between indices and RR1 (the pre-preceding RR intervals), which are referred to as postextrasystolic potentiation (PESP). 6-9 Moreover, Emax was shown to be reasonably predicted by RR2/RR1, 10 which combines mechanical restitution and PESP. In contrast, an earlier study suggested that LV relaxation abnormality could not be detected in patients with AF by means of analysis of the force -interval relationships. 11 Unfortunately, no information is currently available on LV relaxation in patients with both AF and impaired LV systolic function.Afterload-dependence of LV relaxation has been intensively investigated, 12-15 and accentuated afterload-dependence of the LV relaxation time constant ( ) has been attributed to one of the mechanisms underlying impaired LV relaxation observed in failing hearts. 16,17 Moreover, this method of analysis of LV relaxation was successfully applied to a tachycardia-induced heart failure model in dogs. 18 Therefore, in the present study we analyzed on a beat-to-beat basis in patients with both AF and impaired LV systolic function by means of the force (relaxation) -interval relationships, as well as afterload-dependence. To the best of our knowledge, this is the first report to study LV relaxation abnormality in such patients in detail. Methods PatientsOur subjects consisted of 7 men and 5 women with chronic AF, aged from 39 to 68 years old (mean, 53.7±2.5 years old), who had undergone diagnostic cardiac catheterization. Four patients had mitral stenosis, 6 had idiopathic dilated cardiomyopathy, 1 had a prosthetic mitral valve for mitral regurgitation, and 1 had no underlying disease except for AF. These patients were subdivided into 2 groups: group A (7 patients with LV ejection fraction [EF] <0.5) and group B (5 patients with LVEF ≥0.5). We excluded patients with mitral regurgitation that was more than mild because they had no isovolumic relaxation period. None of the patients had a history of angina or myocardial infarction, and all showed normal coronary angiograms. The investigation conformed with the principles outlined in the Declaration of Helsinki. Atsushi Yao, MD; Hiroshi Matsui, MD; Osami Kohmoto, MD*; Takashi Serizawa, MD**; Ryozo Nagai, MD; Toshiyuki Takahashi, MD Left ventricular (LV) contractility i...