Transthoracic echocardiographic measurement of coronary blood flow and reserve

The objectives of this study were to evaluate the use of high-frequency (5 MHz) transthoracic echocardiography for the noninvasive measurement of coronary blood flow and to test its ability to detect small changes in blood flow that may accompany pharmacologic intervention. High-frequency (5 MHz) transthoracic echocardiography was performed on the distal segment of the left anterior descending coronary artery of 32 consecutive patients (23 men and nine women; mean age 60 +/- 10 years) before and after the administration of 0.4 mg sublingual nitroglycerin. The results were compared with those of 10 patients (eight men and two women; mean age 59 +/- 6 years) in whom the ungrafted left internal mammary artery was studied. Doppler velocity profiles of the left anterior descending coronary artery were detected in 18 (56%) of the 32 Study patients. Left anterior descending coronary artery diameter and blood flow were measured in 14 patients (44%). There was no significant difference in blood flow between the left anterior descending artery (74 +/- 35 ml/min) and the internal mammary artery (52 +/- 25 ml/min). After administration of nitroglycerin, there was a 24% decrease in coronary blood flow from 74 +/- 35 ml/min to 56 +/- 30 ml/min (p < 0.05). This study suggests that high frequency transthoracic echocardiography may allow noninvasive identification of the left anterior descending coronary artery and detection of small changes in blood flow that accompany pharmacologic and mechanical intervention.