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Electromechanical dysfunction of the left atrium associated with interatrial block
1Cardiovascular Division, Department of Medicine, University of Massachusetts Medical School-St Vincent Hospital, Worcester, MA 01608, USA.
Objectives:
Our purpose was to determine the effect of interatrial block (IAB, P-wave duration >/=120 ms) on left atrial (LA) dynamics. IAB is associated with LA enlargement (LAE). LA dysfunction is associated with decreased left ventricular filling, a propensity for LA appendage thrombus formation, and reduced atrial natriuretic peptide levels. We evaluated LA function in patients with and without IAB matched for LA size.
Methods:
Echocardiograms with LA enlargement were analyzed. Twenty-four patients had IAB, and 16 patients without IAB formed the control group. LA volumes, A-wave acceleration times (At), LA stroke volume (LASV), ejection fraction (LAEF), and kinetic energy (LAKE) were calculated.
Results:
The control group and patients with IAB had comparable maximal LA volume and diameter (P >.05). Patients with IAB had significantly longer At (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 (20 +/- 14 vs 65 +/- 44 Kdyne/cm/s, P <.01). LAKE varied inversely with P-wave duration (r = -0.51, P <.01). P-wave duration and minimal LA volume were independent determinants of LAEF.
Conclusions:
Patients with IAB have a sluggish, poorly contractile LA, and the extent of dysfunction is related to the degree of electrical delay from IAB. IAB should be considered a marker of an electromechanically dysfunctional LA and hence a risk factor for atrial fibrillation and congestive heart failure.