[Assessment of coronary stenosis severity using a Doppler guide wire in vivo: is the continuity equation applicable to moderate to severe coronary artery stenosis?].

The usefulness of a Doppler guide wire was evaluated in the estimation of coronary stenosis severity in patients with moderate to severe coronary stenosis using the continuity equation. The maximal coronary flow velocities (V) proximal to the stenosis (p), at the stenosis (s), and distal to the stenosis (d) were measured using a Doppler guide wire (12-MHz, 0.018-in) in 12 patients with mild coronary stenosis (less than 50% diameter stenosis: group A) and 12 patients with moderate to severe coronary stenosis (more than 50% diameter stenosis: group B). Percent diameter stenosis (%DS) was calculated from Vp/Vs by: %DS = (1 - square root of Vp/Vs) x 100 (%) (Vp = the maximal velocity proximal to the stenosis; Vs = the peak velocity at the stenotic site) Percent DS was calculated from Vd/Vs by: %DS = (1 - square root of Vd/Vs) x 100 (%) (Vd = the peak velocity distal to the stenosis) Regression of Doppler-derived %DS from Vp/Vs compared to quantitative coronary angiographic % DS were: Group A: y = 0.83x + 3.0 (r = 0.79), Group B: y = 0.63x + 9.4 (r = 0.81), Overall: y = 0.63x + 9.6 (r = 0.91) Regression of Doppler-derived %DS from Vd/Vs compared to quantitative coronary angiographic %DS were: Group A: y = 0.98x - 1.0 (r = 0.81), Group B: y = 0.67x + 14.6 (r = 0.84), Overall: y = 0.79x + 7.6 (r = 0.91) The continuity equation method using a Doppler guide wire underestimates coronary stenosis severity in patients with moderate to severe coronary stenosis, although Doppler-derived %DS is correlated with angiographic %DS.