Phasic coronary blood flow velocity pattern and flow reserve in the atrium: regulation of left atrial myocardial perfusion.

OBJECTIVES The purpose of this study was to assess rest and stress atrial coronary blood flow (CBF) velocity and flow reserve. BACKGROUND Because of the limitations of the methods used until now for assessing myocardial perfusion (MP) in the small mass of atrial tissue, data are lacking for human atrial MP. METHODS Seventeen patients with suitable coronary anatomy underwent CBF velocity measurements with the use of a Doppler guide wire in the proximal left circumflex coronary artery (LCx) and left atrial circumflex branch (LACB), at baseline and after adenosine administration. All measurements were performed at resting heart rate and at 100 and 120 beats/min. RESULTS Coronary blood flow velocity in the LACB showed a predominant systolic pattern in contrast to the diastolic pattern of the LCx. There was a disproportionate increase in baseline time-averaged peak coronary flow velocity (cm/s) between the LACB and LCx during the two levels of pacing-induced stress (16.8 +/- 5.5 vs. 16.2 +/- 5.1 at rest; 22.9 +/- 7.9 vs. 18.4 +/- 5.2 at 100 beats/min; and 27.1 +/- 8.0 vs. 20.4 +/- 5.1 at 120 beats/min; significant interaction, p < 0.001), but there were no significant differences in coronary flow reserve (CFR). CONCLUSIONS Coronary blood flow in the left atrium is out of phase with that in the ventricular myocardium, showing a predominant systolic pattern. Although atrial and ventricular CFR show no significant differences at rest and with two levels of stress, the disproportionate increase in atrial blood flow velocity during stress indicates a peculiarity of atrial perfusion regulation.