CORONARY-ARTERY FLOW MONITORING FOLLOWING CORONARY INTERVENTIONS

Technologic innovations have made it possible to measure coronary artery blood flow in awake patients. Both flow velocity as well as flow reserve can be assessed. In particular, the period of time immediately following coronary interventions offers a unique opportunity to study important features of coronary flow behavior. In 22 patients, coronary flow reserve was measured before and after an intervention, either angioplasty or atherectomy, using a 0.018-in Doppler guidewire (Flowire). The minimum lumen diameter (MLD) was increased from 1.0 +/- 0.4 to 1.7 +/- 0.4 mm, while coronary flow velocity increased significantly, rising from 29 +/- 13 to 39 +/- 14 cm/sec (p < 0.025). The maximum hyperemic velocity also increased, from 44 +/- 16 to 69 +/- 21 cm/sec. Using only the preintervention or postintervention values, the flow reserve ratio was 1.53 +/- 0.4 prior to intervention and 1.84 +/- 0.5 after intervention (p = nonsignificant). However, the postintervention value may have been artifactually reduced by the fact that both resting as well as hyperemic velocities increased. When the postintervention flow reserve ratio was recalculated, using the preintervention resting value, flow reserve ratio was seen to increase from 1.53 +/- 0.4 to 2.73 +/- 1.2 (p < 0.001). Measurements of coronary flow in the postintervention period also revealed several interesting phenomena. Spasm of a coronary artery was documented, and its resolution in response to intracoronary nitroglycerin was observed. Elastic recoil following angioplasty was documented by gradual decline in coronary flow over 30 minutes. Cyclic flow variations were observed; these are due to the accumulation and dislodgement of platelet aggregates at sites of coronary stenosis with endothelial injury. Their prompt abolition with the administration of a monoclonal antiplatelet antibody [c7E3 F(ab)] was documented- In conclusion, we have begun to characterize several interesting and potentially useful coronary flow phenomena that may occur following coronary interventions. We have found this information to be clinically useful.