Left ventricular relaxation abnormality is detectable by analysis of the relaxation time constant in patients with atrial fibrillation

Left ventricular (LV) contractility is constantly changing during atrial fi brillation (AF), which is dependent on the force-interval relationships. Ho wever, no information has been available on LV relaxation in patients with both AF and impaired LV systolic function. LV pressure was measured with a catheter-tipped micromanometer and the time constant of isovolumic LV press ure decline (tau (bf)) was calculated with best exponential fitting from mo re than 10 consecutive beats. Patients with AF (5 with mitral valvular dise ase, 6 with idiopathic dilated cardiomyopathy, and 1 with no underlying dis ease) were subdivided into 2 groups: group A, with ejection fraction (EF) < 0.5 (n=7): and group B, with EF <greater than or equal to>0.5 (n=5). Linear correlation coefficients (r) between tau and RR2, RR2/RR1, LV peak systoli c pressure (peak LVP) were calculated. Although tau did not show a discrepa ncy between the 2 groups, tau (bf) correlated better with RR2/RR1 only in t he group A patients. The relation between tau and peak LVP showed a good co rrelation with a steep slope (R, Delta tau/Delta peak LVP) only in the grou p A patients (accentuated afterload-dependence). R was significantly differ ent between the 2 groups. Thus, a beat-to-beat analysis of tau may be a pra ctical and feasible way for detecting LV relaxation abnormality in patients with AF.