Quantitative contrast echo cardiographic assessment of collateral derived myocardial perfusion during elective coronary angioplasty

Objective-To determine whether myocardial contrast echocardiography can be used to quantify collateral derived myocardial flow in humans. Methods-In 25 patients undergoing coronary angioplasty, a collateral flow i ndex (CFI) was determined using intracoronary wedge pressure distal to the stenosis to be dilated, with simultaneous mean aortic pressure measurements . During balloon occlusion, echo contrast was injected into both main coron ary arteries simultaneously. Echocardiography of the collateral receiving m yocardial area was performed. The time course of myocardial contrast enhanc ement in images acquired at end diastole was quantified by measuring pixel intensities (256 grey units) within a region of interest. Perfusion variabl es, such as background subtracted peak pixel intensity and contrast transit rate. were obtained from a fitted gamma variate curve. Results-16 patients had a left anterior descending coronary artery stenosis , four had a left circumflex coronary artery stenosis, and five had a right coronary artery stenosis. The mean (SD) CFI was 19 (12)% (range 0-47%). Me an contrast transit rate was 11 (8) seconds. In 17 patients, a significant collateral contrast effect was observed (defined as peak pixel intensity mo re than the mean + 2 SD of background). Peak pixel intensity was linearly r elated to CFI in patients with a significant contrast effect (p = 0.002, r = 0.69) as well as in all patients (p = 0.0003, r = 0.66). Conclusions-Collateral derived perfusion of myocardial areas at risk can be demonstrated using intracoronary echo contrast injections. The peak echo c ontrast effect is directly related to the magnitude of collateral flow.