Coronary dilation with standard dose dipyridamole and dipyridamole combined with handgrip.

Intravenous dipyridamole is widely used to produce coronary vasodilation during cardiac imaging procedures. However, the routinely used dose of dipyridamole (0.56 mg/kg IV over 4 min) does not always result in maximal coronary dilation. The addition of isometric handgrip during dipyridamole coronary dilation has been reported to substantially increase coronary blood flow over dipyridamole alone. We compared the coronary vasodilation resulting from infusion of the standard dose of dipyridamole with that resulting from a maximally dilating dose of intracoronary papaverine in 12 patients with angiographically normal coronary arteries. We also assessed the effect on coronary blood flow velocity of the addition of isometric handgrip during dipyridamole coronary dilation. Changes in coronary blood flow velocity were measured with a 3F coronary Doppler catheter. The coronary flow reserve (peak/resting coronary flow velocity ratio) after dipyridamole (3.7 +/- 1.2 [mean +/- SD] was less than that seen after papaverine (4.4 +/- 0.5, p less than 0.05), and the coronary vascular resistance index during dipyridamole coronary vasodilation (0.28 +/- 0.09) was greater than during papaverine (0.22 +/- 0.03, p less than 0.05). The dipyridamole coronary flow reserve was less than 3.0 in four subjects and was 2.0 or less in two subjects. The addition of isometric handgrip to dipyridamole coronary vasodilation produced an 8% increase in mean heart rate and a 17% increase in mean arterial pressure, but coronary flow reserve was unchanged (3.8 +/- 1.1 before handgrip vs. 4.0 +/- 1.1 with handgrip). Quantitative angiography in six patients revealed no change in coronary caliber with the addition of handgrip.(ABSTRACT TRUNCATED AT 250 WORDS)