Assessment of coronary reserve by transoesophageal Doppler echocardiography. Direct comparison between different modalities of dipyridamole and adenosine administration

Abstract

Background: This study was undertaken to compare the coronary vasodilator response to different application modalities of intravenous vasodilators, in order to identify the optimal pharmacological protocol for the evaluation of coronary reserve by means of transoesophageal Doppler echocardiography.

Methods: Blood flow velocity in the left anterior descending artery, coronary vascular resistance and left main coronary artery cross-sectional area were assessed by transoesophageal echo-Doppler during an i.v. adenosine bolus (5 mg), a 5-min adenosine infusion (infusion rate 140 micrograms. kg-1 min-1), and low (0.56 mg.kg-1. 4 min-1), and high-dose (0.84 mg.kg-1.9 min-1) dipyridamole infusions in 10 healthy normals (Group 1) and in 20 patients (Group 2) with either coronary microvascular disease (11 patients) or coronary artery disease (nine patients).

Results: In both groups, the highest flow velocity and the lowest coronary vascular resistance were observed during the adenosine infusion. Flow velocity values and indices of coronary vasodilator capacity observed after the adenosine bolus and the high-dose dipyridamole infusion were very close to those obtained during the adenosine infusion, especially in Group 1. Coronary flow velocity was lower and coronary vascular resistance higher after low-dose dipyridamole, significantly in Group 2. The maximal flow response to the adenosine bolus was observed within a few seconds after the injection, and was very short. The peak response to the adenosine infusion was observed 57 +/- 27 s after its start. The coronary flow velocity response to dipyridamole was dose dependent and differed between Groups 1 and 2.

Conclusion: In combination with transoesophageal Doppler echocardiography, a short-lasting adenosine infusion at a rate of 140 micrograms.kg-1.min-1 seems to be preferable to an adenosine bolus and dipyridamole infusion. The effect of the bolus is too short for an accurate measurement of coronary flow velocity, while the dipyridamole infusion, especially at a low dose, induces a submaximal vasodilator response.