Cyclic coronary artery flow in dogs after coronary angioplasty

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Abstract
Coronary artery cyclic flow variations, caused by accumulation and dislodgement of platelet aggregates, are known to occur in dogs with coronary stenosis and endothelial injury. Thromboxane A2 and serotonin appear to be mediators of cyclic flows. We tested the hypotheses that cyclic flows occur in dogs after coronary angioplasty and may be reduced or eliminated by a thromboxane A2 or serotonin-receptor antagonist. Stable cyclic flows were established following angioplasty in 19 open-chest dogs fitted with Doppler coronary flow probes and external coronary constrictors. Prior to cyclic flows, phasic and mean coronary flows had been reduced by the constrictors to 69±7% (mean±SE) and 83±7% of control, respectively. Hemodynamic variables were unchanged, and cyclic flows continued uninterrupted at 10 to 12 cycles per hour in 6 of the dogs that were monitored for 3 hours before treatment. All 19 treated dogs had cyclic flows abolished within 1 to 8 minutes after intravenous injections of either a thromboxane A2 or serotonin-receptor antagonist (SQ29548, 0.2 to 0.4 mg/kg body weight, or LY53857, 0.1 to 0.2 mg/kg, respectively). Histologic examination confirmed the presence of intimal and medial arterial wall damage at dilated sites, with early necrosis, inflammatory cell infiltrates, and occasional adherent platelets. One other dog with established cyclic flows, killed at a nadir of coronary artery flow, was also found to have occlusive thrombus at the angioplasty site. Thus, coronary artery cyclic flow variations, similar to those described in other preparations of coronary stenosis and endothelial injury, also occur after coronary angioplasty in dogs with residual coronary artery stenoses, and they appear to be mediated by thromboxane A2 and serotonin.

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