ESTIMATION OF CORONARY BLOOD-FLOW BY ECG GATED CARDIAC THERMOGRAPHY IN OPEN-CHEST CONDITIONS

Thermography is suggested as a tool to estimate myocardial and coronar y epicardial how in open-chest heart surgery. To test the feasibility and compare various methods for coronary flow estimation in open-chest surgery, thermographic imaging was applied to eight open-chest dogs w hich were injected with cold saline into the aortic root. Blood flow i n the left arterial descending (LAD) coronary vessel was measured by a transit-time flowmeter. ECG gated images were acquired for 20-30 s, w hile the cold saline (20 mi) was injected into the aortic root. Severa l flow levels were achieved during repeated hyperaemic response to tra nsient occlusions of the LAD. A temperature response curve for each fl ow level was obtained by averaging over an edge-detected arterial segm ent for each image frame. Several indices were calculated from the tem perature curve and correlated with the measured coronary flow. These i nclude: an index based on a corrective heat transfer model (r = 0.69, p < 0.001), the slope of the descending part of the response curve (I = 0.76, p < 0.001), the peak temperature difference (r = 0.66, p < 0.0 01), and the area above the temperature response curve (r = 0.61, p < 0.01). As shown, coronary flow can be estimated quantitatively by intr aoperative epicardial thermography, and may therefore provide importan t on-line information regarding blood flow during open-chest surgical procedures. Further studies are required for optimal application of th is technique so as to increase its potential as a valid clinical tool.