Frequency of slow coronary flow following successful stent implantation and effect of Nitroprusside

Nitroprusside (NTP) is used for the treatment of slow coronary flow (SCF) after coronary interventions. The wide variation in dosage, route, and timing of its administration in the reported studies prevents an objective assessment of its efficacy. We report the incidence and response to a standardized NTP protocol of SCF after successful stent implantation. Selective intracoronary administration of incremental doses (initial bolus of 80 microg incremented by 40 microg) of NPT was assessed in 21 patients who developed SCF in a series of 2,212 consecutive patients who underwent successful stent placement from January to October 2005. SCF was observed only in patients treated for acute myocardial infarction (AMI; 11.5%, 12 of 105) or saphenous vein graft (SVG) stenosis (8.2%, 9 of 109). An intracoronary bolus of nitroglycerin did not restore normal Thrombolysis In Myocardial Infarction (TIMI) flow in any patient. The first 80-microg dose of NTP restored normal TIMI flow in 58% of patients (7 of 12) with AMI and in 44% of patients (4 of 9)with SVG stenosis. The maximal dose (120/160 microg) restored normal TIMI flow in all remaining patients with AMI but in only 1 additional patient with SVG stenosis. At the end of the procedure, the percent decrease in corrected TIMI frame count was significantly larger in patients with AMI (-44+/-10%) than in those with SVG stenosis (-24+/-16%, p=0.02). In a large consecutive series of successful stent procedures, SCF was found only in patients with ST-elevation AMI (11.5%) or with a stenosed SVG (8.2%). In conclusion, the standardized protocol of intracoronary NTP administration succeeded in normalizing SCF in all patients with AMI but in only 5 of 9 patients with SVG stenosis. This latter subgroup requires other therapeutic strategies.