[Phase variations in the left coronary transstenotic pressure gradient before and after dilatation by percutaneous...

The concept of significant coronary stenosis may be approached by studying the effects of the narrowing not in absolute values of pressure and flow but by studying the mode of blood flow across the stenosis. Ten patients with isolated stenosis of the LAD were studied for phasic variations of the transstenotic pressure gradient before and after dilatation. The material used was a ST 3.7 catheter with a 0.12 inch guide. Instantaneous pressure recording throughout the cardiac cycle were obtained using a computer. After dilatation, the area of the stenosis minus the area of transverse section of the dilating catheter increased from 0.5 +/- 0.3 to 2.2 +/- 0.3 mm2, the average gradient between the aorta and the post stenotic LAD decreased from 75 +/- 10 to 12 +/- 8 mmHg, and the ratio between the mean diastolic gradient and mean gradient increased from 75 +/- 7 to 245 +/- 30% (p less than 0.01 for the 3 parameters, paired t test). These results show that the LAD transstenotic pressure gradient is not phasic in severe stenosis. It becomes phasic, only in diastole, after dilatation of the stenosis (slight residual stenosis due to the catheter). This difference may be due to the type of flow, continuous and dependent on the stenosis before dilatation, or phasic dependent on the distal coronary circulation after dilatation. Analysis of the phasic changes of coronary flow may be useful for the evaluation of the severity of left coronary stenosis in the absence of pressure measurements.