Effectiveness and safety of intracoronary papaverine, alprostadil, and high dosages of nicorandil and adenosine triphosphate for measurement of the index of coronary microcirculatory resistance in a pig model.

BACKGROUND

Papaverine is used to induce maximal hyperemia for index of coronary microcirculatory resistance (IMR) measurement in animal experiments, although it can lead to polymorphic ventricular tachycardia and ventricular fibrillation.

OBJECTIVES

This study investigated the effect of an intracoronary (IC) bolus of high adenosine triphosphate (ATP) and nicorandil doses for IMR measurement and explored the possibility of inducing maximal hyperemia with an IC alprostadil bolus.

MATERIAL AND

METHODS

Index of coronary microcirculatory resistance was measured in a hyperemic state induced by 7 experimental conditions in 21 pigs (IC bolus of papaverine (18 mg), ATP (40 μg, 80 μg, 160 μg, and 240 μg), and nicorandil (2 mg and 4 mg)). The 7 conditions were induced sequentially, and the average IMR was calculated. Because of the long-term hyperemic condition in the pilot experiments, the IMR was measured 1, 3, 5, 8, and 10 min after an IC bolus of alprostadil (10 μg) in another 7 pigs.

RESULTS

The IMR induced by 240 μg of ATP or 4 mg of nicorandil was not significantly different from that induced by 18 mg of papaverine (both p > 0.05). A strong linear correlation was observed between IMRs with papaverine (18 mg) and nicorandil (4 mg) (R2 = 0.936, p < 0.001) and with papaverine (18 mg) and ATP (240 μg) (R2 = 0.838, p < 0.05). The IC bolus of nicorandil (4 mg) produced the smallest changes, whereas papaverine caused the most significant changes in mean blood pressure and heart rate (p < 0.05). Tachypnea and transient ST depression were more common with increasing ATP dosages (especially 240 μg). Alprostadil (5 min) yielded a significant hyperemic response but reduced baseline blood pressure by almost 40% for a long time.

CONCLUSIONS

Intracoronary bolus administration of 4 mg of nicorandil was better than 18 mg of papaverine or 240 μg of ATP for induction of maximal hyperemia and IMR measurement in a pig model, whereas alprostadil was not suitable for IMR measurement.