Effects of slow coronary artery flow on P-wave dispersion and atrial electromechanical coupling

Slow coronary flow (SCF) is characterized by angiographically normal coronary arteries with delayed opacification of the distal vasculature. The purpose of this study was to evaluate atrial electromechanical couplings and P-wave dispersion (Pd) reflecting intraatrial and interatrial conduction delays in SCF patients and the relationship between these parameters and Thrombolysis in Myocardial Infarction (TIMI) frame count.

Thirty-four patients with SCF and 40 controls were enrolled. From 12-lead surface electrocardiograms, Pd was calculated. Atrial electromechanical coupling (PA), intraatrial, and interatrial electromechanical delay were measured with tissue Doppler imaging.

Maximum P-wave duration (Pmax) and Pd were higher in SCF patients than those of controls (109.2 +/- 9.3 vs 92.3 +/- 13.5 milliseconds; P < .0001 and 50.4 +/- 9.4 vs 34.4 +/- 8.9 milliseconds; P < .0001). Atrial electromechanical coupling at the left lateral mitral annulus (lateral PA), septal mitral annulus (septal PA), and right ventricular tricuspid annulus (RV PA) were significantly higher in SCF patients than controls (68.1 +/- 8.1 vs 52.6 +/- 7.3 milliseconds; P < .0001; 49.3 +/- 9.8 vs 38.2 +/- 5.3 milliseconds; P < .0001; 47.5 +/- 9.0 vs 37.6 +/- 4.6 milliseconds, P < .0001, respectively). Interatrial electromechanical delay (lateral PA - RV PA) was significantly longer in SCF patients (20.6 +/- 9.1 vs 15.0 +/- 6.0 milliseconds; P = .0002). A positive correlation was detected between circumflex coronary artery TIMI frame count and interatrial electromechanical delay (r = 0.45; P < .01).

Prolongation of interatrial electromechanical delay, Pmax, and Pd suggest that SCF might contribute to development of adverse functional and electrophysiologic atrial characteristics in these patients.