Measurement of coronary reactive hyperemia during clinical angiography by video dilution technique

In order to further quantitate the severity of coronary lesions, the reactive hyperemic response in the coronary circulation was measured utilizing video dilution densitometry performed during routine coronary angiography in 16 patients. Two ml of contrast medium were selectively injected from a prefilled syringe attached to the coronary manifold. After ten seconds passed, a second 2 ml of contrast medium was selectively injected during the hyperemia induced by the previous injection. The fluoroscopic image from these two injections was recorded on videotape. The videotape was subsequently replayed through the videodensitometer, and contrast medium versus time curves were obtained from the coronary artery. The area under each curve was measured by planimetry, and for each pair, the flow ratio was determined as the inverse ratio of the area under each curve. An angiographically significant lesion was defined as a loss greater than 75 per cent of the coronary cross-sectional area. The hyperemic flow ratio was 1.57 ± 0.28 (mean ± SD) in 14 right or left coronary systems with no significant disease, 1.1 ± 0.09 in 4 patients with lesions in the left anterior descending coronary (LAD) or the left circumflex artery (LCX), and 0.89 ± 0.19 in 6 coronary systems with either significant right coronary disease or combined LAD and LCX disease. Thus, reactive hyperemia ratios obtained by the video dilution technique during coronary angiography provided flow data to complement the anatomic description of the lesions. In 3 patients, a decrease in coronary blood flow after contrast medium confirmed a phenomenon noted with severe experimental coronary obstruction.