The phenomenon of "no-reflow" has been described frequently after rotational atherectomy. The aim of this study was to determine the coronary hemodynamic changes by Doppler flow wire before and after rotational atherectomy and adjunctive balloon angioplasty in 10 patients. All patients had TIMI-III flow at baseline. After rotational atherectomy alone, two patients had TIMI-I, four patients had TIMI-II, and four patients had TIMI-III flow. In addition, the number of Cineframes to Opacification of a preselected distal landmark increased twofold (from 49 +/- 12 to 118 +/- 27 frames; P < 0.05). Intracoronary nitroglycerin and verapamil was associated with return to baseline of both measurements. Following adjunctive balloon angioplasty, there was an increase in lumen diameter (1.29 +/- 0.1 vs. 2.6 +/- 0.1 mm; P < 0.05), coronary flow (81 +/- 14 to 154 +/- 18 ml/min; P < 0.05), maximal absolute velocity (23 +/- 4 to 52 +/- 4 cm/sec; P < 0.05), and vascular resistance decreased (1.74 +/- 0.4 to 0.74 +/- 0.4 mm Hg/ml/min; P < 0.05). However, no change in coronary flow reserve was noted (1.24 +/- 0.1 vs. 1.5 +/- 0.3). Immediately after rotational atherectomy alone, there is a reduction in angiographically determined coronary flow, suggesting either distal microvascular spasm or distal microvascular obstruction. Regardless of the mechanism, the transient reduction of coronary flow was rapidly reversed by coronary vasodilators. Despite the significant improvement of coronary hemodynamics noted immediately after combined rotational atherectomy and balloon angioplasty, coronary flow reserve remained abnormal. Similarly, no change in coronary flow reserve has been reported immediately after balloon angioplasty alone. The lack of improvement in flow reserve after both balloon angioplasty and rotational atherectomy suggests that the mechanisms of improved flow reserve may be device independent, and remain unexplained.