Effect of Intracoronary Nicardipine on the Spontaneous Coronary Slow Flow Phenomenon

Aims: An under-recognized cause of chest pain, the coronary slow flow (CSF) phenomenon is characterized by delayed coronary opacification during diagnostic angiography in the absence of obstructive CAD. Because of its angiographic resemblance to no-reflow during PCI (a condition associated with microvascular spasm), we hypothesized that spontaneous CSF may be reversed by pharmacological intervention with intracoronary (IC) nicardipine. Method: The effect of IC nicardipine on CSF was assessed in 26 consecutive patients. CSF was defined as spontaneously delayed flow (<TIMI 3) during diagnostic angiography in the absence of epicardial CAD or other conditions potentially associated with impaired flow. Nicardipine was administered directly via the coronary catheter as a 200 mcg bolus after which repeat angiography was performed. Coronary flow before and after nicardipine was assessed by TIMI flow grade and corrected TIMI frame count (TFC) assessments. Results: The study population consisted of 18 men and 8 women, aged 53 +/- 12 years. The clinical presentation was rest angina in 18 (69%) of patients. At baseline, CSF with <TIMI 3 flow was observed in 46 vessels (24 LAD, 7 LCX, 13 RCA). TFC was prolonged (>27) in 58/78 (74%) epicardial vessels. IC nicardipine characteristically produced markedly accelerated coronary filling; this observation was corroborated by TFC analysis. TFC was 53 +/- 17 before versus 15 +/- 5 after nicardipine (p<0.001). All vessels demonstrated TIMI 3 flow and TFC<28 after nicardipine. Conclusion: Intracoronary nicardipine appears highly effective in reversing spontaneous CSF and implicates microvascular spasm in its pathogenesis. Future studies of oral calcium blockers in the management of patients with CSF are needed.