Changes in diameter of coronary narrowings and translesional hemodynamics after intracoronary nitroglycerin

The effect of intracoronary nitroglycerin on coronary stenosis dimensions and translesional hemodynamics was evaluated in 38 subjects (74 stenoses) referred for diagnostic coronary arteriography. Quantitative coronary arteriography was performed with standard Newtonian fluid dynamic equations used to estimate transstenotic gradients. Since intracoronary nitroglycerin can induce significant myocardial hyperemia (increased flow velocity), with increased translesional pressure gradients and a decrease in distal intraluminal pressure, the potential effect on subendocardial flow distribution was also analyzed. Minimum stenotic diameter significantly increased postnitroglycerin (NTG) (preNTG 1.42 vs postNTG 1.82 mm, p less than 0.01), with a decrease in relative percent diameter stenosis (preNTG 45.7 vs postNTG 40.7%, p less than 0.05). When changes in minimum stenotic diameter were analyzed according to stenosis severity (quartiles), the greatest effect was noted in those lesions with the least severe stenosis (quartile no. 1, 0.49 vs quartile no. 4, 0.32 mm, p less than 0.05). If coronary blood flow velocity remains at baseline values (4 cm/s), intracoronary nitroglycerin was predicted to significantly decrease transstenotic pressure gradients (preNTG 1.01 vs postNTG 0.82 mm Hg, p less than 0.05), with the greatest change shown in severe lesions (quartile no. 4, preNTG 3.79 to postNTG 2.28 mm Hg, p less than 0.01). Accelerated coronary flow velocity (myocardial hyperemia) increased calculated translesional pressure gradients (4 cm/s, 0.82 mm Hg vs 20 cm/s, 8.00 mm Hg, p less than 0.01), despite simultaneous stenotic vasodilation. Hemodynamic obstruction was particularly dependent on coronary flow velocity in the most severe stenoses (quartile no. 4, 4 cm/s, 2.28 vs 20 cm/s, 28.78 mm Hg, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)