Abstract Aim 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. Methods 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. Results 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 P P P P P = .0002). A positive correlation was detected between circumflex coronary artery TIMI frame count and interatrial electromechanical delay ( r = 0.45; P Conclusions 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.