Dynamic change in collateral flow associated with myocardial ischemia in humans

Background: This study sought to investigate how collateral flow changes du ring myocardial ischemia in patients. Methods: Myocardial contrast echocard iography (MCE) and rapid atrial pacing were performed in 20 patients with a ngiographically evidenced coronary collaterals from the right coronary arte ry (RCA) to the occluded left anterior descending coronary artery. Sonicate d contrast medium was injected into the RCA before and immediately after at rial pacing to determine the peak background-subtracted contrast intensity (PI) in the collateral territory (PIA) and its ratio to PI in the control t erritory (PI ratio) as parameters of collateral blood flow. Lactate product ion in the coronary circulation during pacing was determined to assess myoc ardial ischemia in the collateral territory. Results: PIA showed a signific ant correlation with regional wall motion either before (r(squared) = -0.64 , P < 0.01) or after pacing (r(squared) = -0.65, P < 0.01). Similarly, PI r atio was significantly correlated with regional wall motion either before ( r(squared) = -0.54, P < 0.05) or after pacing (r(squared) = -0.64, P < 0.01 ). Rapid atrial pacing decreased both PIA and PI ratio significantly greate r in patients with lactate production than in those without (PIA: -67 +/- 5 3 vs. -15 +/- 34%, P < 0.05; PI ratio: -68 +/- 49 vs. -8.2 +/- 32%, P < 0.0 5, respectively), while neither PIA nor PI ratio differ between the two gro ups of patients before pacing (PIA: 13.8 +/- 19. vs. 16.2 +/- 13.3U, P = 0. 75: PI ratio: 0.70 +/- 0.71 vs. 0.87 +/- 0.65, P = 0.58, respectively). Con clusions: We concluded that (1) collateral flow determined by MCE was close ly associated with regional cardiac function, and (2) not the amount of col lateral flow at rest, but pacing-induced change of collateral flow seemed t o be a determinant of regional ischemia in patients with coronary collatera ls. (C) 2001 Elsevier Science Ireland Ltd. Ail rights reserved.