ANGIOPLASTY GUIDEWIRE VELOCITY - A NEW SIMPLE METHOD TO CALCULATE ABSOLUTE CORONARY BLOOD VELOCITY AND FLOW

The Thrombolysis In Myocardial Infarction (TIMI) frame count is a rela tive index of coronary flow that measures time by counting the number of frames required for dye to travel from the ostium to a standardized coronary landmark in a cineangiogram filmed at a known speed (frames/ s). We describe a new method to measure distance along arteries so tha t absolute velocity (length divided by time) and absolute flow (area x velocity) may be calculated in patients undergoing percutaneous trans luminal coronary angiography (PTCA). After PTCA, the guidewire tip is placed at the coronary landmark and a Kelly clamp is placed on the gui dewire where it exits the Y-adapter. The guidewire tip is then withdra wn to the catheter tip and a second Kelly clamp is placed on the wire where it exits the Y-adapter. The distance between the 2 Kelly clamps outside the body is the distance between the catheter tip and the anat omic landmark inside the body. Velocity (cm/s) may be calculated as th is distance (cm) divided by TIMI frame count (frames) x film frame spe ed (frames/s). Flow (ml/s) may be calculated by multiplying this veloc ity (cm/s) and the mean cross-sectional lumen area (cm(2)) along the l ength of the artery to the TIMI landmark. In 30 patients, velocity inc reased from 13.9 +/- 8.5 cm/s before to 22.8 +/- 9.3 cm/s after PTCA ( p <0.001). Despite TIMI grade 3 flow both before and after PTCA in 18 patients, velocity actually increased 38%, from 17.0 +/- 5.4 to 23.5 /- 9.0 cm/s (p = 0.01). For all 30 patients, flow doubled from 0.6 +/- 0.4 ml/s before to 1.2 +/- 0.6 ml/s after PTCA (p <0.001). In the 18 patients with TIMI grade 3 flow both before and after PTCA, flow incre ased 86%, from 0.7 +/- 0.3 to 1.3 +/- 0.6 ml/s (p = 0.001). Distance a long coronary arteries (length) can be simply measured using a PTCA gu idewire. This length may be combined with the TIMI frame count to calc ulate measures of absolute velocity and flow that are sensitive to cha nges in perfusion. TIMI grade 3 flow is composed of a range of velocit ies and flows. (C) 1997 by Excerpta Medica, Inc.