Electromechanical dysfunction of the left atrium associated with interatrial block

Objectives Our purpose was to determine the effect of interatrial block (IA B, P-wave duration greater than or equal to 120 ms) on left atria[ (LA) dyn amics. IAB is associated with LA enlargement (LAE). LA dysfunction is assoc iated with decreased left ventricular filling, a propensity for LA appendag e thrombus formation, arid reduced atrial natriuretic peptide levels. We ev aluated LA function in patients with and without IAB matched for LA size. Methods Echocardiograms with LA enlargement were analyzed. Twenty-four pati ents had IAB, and 16 patients without IAB formed the control group. LA volu mes, A-wave acceleration times (At), LA stroke volume (LASV), ejection frac tion (LAEF), and kinetic energy (LAKE) were calculated. Results The control group and patients with IAB had comparable maximal LA v olume and diameter (P > .05). Patients. with IAB had significantly longer A t (115 +/- 39 ms vs 83 +/- 24 ms, P < .01) and smaller LASV (7 +/- 5 mL vs 17 +/- 6 mL, P < .01), LAEF (9% +/- 6% vs 25% +/- 8%, P < .01), and LAKE (2 0 +/- 14 vs 65 +/- 44 Kdyne/cm/s, P < .01). LAKE varied inversely with P-wa ve duration (r = -0.51, P < .01). P-wave duration and minimal LA volume wer e independent determinants of LAEF. Conclusions Patients with IAB have a sluggish, poorly contractile LA, and t he extent of dysfunction is related to the degree of electrical delay from IAB. IAB should be considered a marker of an electromechanically dysfunctio nal LA and hence a risk factor for atrial fibrillation and congestive heart failure.