Myocardial perfusion in patients with transposition of the great arteries after arterial switch operation.

Abstract

To the Editor: Oskarsson et al1 recently reported normal coronary flow reserve (CFR) in children with transposition of the great arteries after anatomic repair assessed by intracoronary Doppler FloWire (Cardiometrics, Inc). CFR can be measured by several techniques, each one with distinct advantages and limitations. An important distinction is between techniques that measure coronary blood flow (eg, positron emission tomography) and those that measure blood flow velocity (eg, Doppler catheters), from which coronary velocity reserve is calculated. Under ideal conditions, there is a linear relation between flow velocity and flow, and therefore the peak-to-rest flow velocity ratio can be substituted for the flow ratio as a measure of CFR. However, coronary velocity reserve is affected by a number of factors, including rheological parameters, the entrance angle of the coronary arteries (which is important in patients after coronary reimplantation), and the shape of the flow profile. While basal coronary blood flow depends on the determinants of myocardial oxygen demand (heart rate, contractility, ventricular load), …