Interatrial conduction time and left atrial function in patients with left ventricular systolic dysfunction: effects of cardiac resynchronization therapy.

BACKGROUND: Prolonged interatrial conduction time (IACT) can be associated with abnormal left atrial (LA) function but has not been characterized in patients with left ventricular (LV) systolic dysfunction (LVSD) and QRS intervals >130 ms.
METHODS: Two-dimensional Doppler echocardiography and Doppler tissue imaging (DTI) were performed in 41 patients with LVSD (mean LV ejection fraction, 26 +/- 5%) and 41 similarly aged normal controls. Two-dimensional measurements included LV volume and ejection fraction and LA volume for the determination of LA emptying fraction and LA ejection fraction. IACT was defined as the time from the onset of the P wave to the onset of the DTI-derived late diastolic (A') velocity at the lateral mitral annulus. Two-dimensional Doppler measurements were reassessed in patients with LVSD 4 +/- 2 months after cardiac resynchronization therapy (CRT).
RESULTS: IACT was longer in patients with compared to controls (105 +/- 25 vs 74 +/- 12 ms, P < .001); none of the controls had an IACT > 100 ms. In patients with LVSD, IACT was correlated modestly with measurements of LA volume (r = .41-.48, all P values < .009) but not with measurements of LA function. Patients with LVSD with IACTs > 100 ms (n = 20) prior to CRT had larger LA volumes and lower indices of LA function after CRT compared to those with IACTs < or = 100 ms. Significant reductions in LV end-systolic volumes and increases in LV ejection fractions occurred in both groups after CRT.
CONCLUSION: DTI-derived IACT can be prolonged in patients with severe LVSD and wide QRS intervals. An IACT > 100 ms can affect LA remodeling and function at early follow-up after CRT but does not influence the response in LV end-systolic volume or ejection fraction.