Estimation of left ventricular contractile performance in atrial fibrillation: experimental and clinical studies

There are few studies regarding the assessment of left ventricular contractile function in patients with atrial fibrillation (AF). The aim of this study was to assess the left ventricular (LV) contractile function, i.e., the end-systolic pressure-volume relation (Ees) and a recently developed LV systolic myocardial stiffness constant (Ksm), without load manipulation in AF. In an experimental study of acute AF in dogs (n = 5), we were able to assess these indexes of the LV contractile function during acute AF, and found that the values were similar to those obtained during occlusion of the inferior vena cava (IVC) at the baseline state. During rapid ventricular pacing (140 or 160 bpm), the indices of LV contractile function increased due to the force-frequency relation (4.56 +/- 1.85, Ees baseline; 6.42 +/- 2.54*+, Ees pacing; 5.15 +/- 2.01 mmHg/ml, Ees AF; *P < 0.05 vs baseline, +P < 0.05 vs. AF)(4.73 +/- 0.48, Ksm baseline; 6.24 +/- 1.12*+, Ksm pacing; 3.99 +/- 1.14, Ksm AF; *P < 0.05 vs baseline, +P < 0.05 vs AF). In a study of chronic clinical AF in patients without heart disease (lone AF, n = 7), the indexes of LV contractile function were preserved compared with those of control patients (CTL, n = 10) obtained during IVC occlusion; the values were decreased in patients with both AF and dilated cardiomyopathy (AFDCM, n = 5)(2.5 +/- 1.1, Ees CTL; 2.4 +/- 0.4, Ees lone AF; 1.1 +/- 0.3 mmHg/ml*+, Ees AFDCM; *P < 0.05 vs CTL, +P < 0.05 vs lone AF)(5.3 +/- 1.8, Ksm CTL; 4.9 +/- 1.6, Ksm lone AF; 2.7 +/- 0.2*+, Ksm AFDCM; *P < 0.05 vs CTL, +P < 0.05 vs lone AF). Thus, during acute AF in dogs and in chronic AF patients, LV contractile function was assessed without load manipulation. In both the acute AF dogs and the chronic lone AF patients, LV contractile function was preserved, and in the AFDCM patients it was depressed.