Determinants of contractile reserve in the infarction area. A quantitativestudy using dobutamine contrast in left ventriculography

Objective. The aim of this study was to relate the contractile reserve in i nfarction segments to the dysfunction at rest and to the residual coronary stenosis. Methods. The study group consisted of 95 patients with a first myocardial i nfarction. Contrast left ventricular at baseline and after dobutamine infus ion at 7.5 mu g/kg/min and coronary angiograms were performed. The centerli ne method was used to quantify the extent of dysfunction (percentage of cho rds with dysfunction in the territory of the infarction artery) and its max imum severity (maximum units of standard deviation [SD] below the normal wa ll motion reference). Reduction of dysfunction extent with dobutamine was m easured. Results. On increasing baseline dysfunction severity, both the magnitude of the response to dobutamine (less than or equal to 2 SD [n = 12] = 33 +/- 1 9%, > 2 SD less than or equal to 3 SD [n = 20] = 20 +/- 16%, > 3 SD less th an or equal to 4 SD [n = 35] = 16 +/- 19%, > 4 SD +/- 5 SD [n = 15] = 9 +/- 13%, > 5 SD [n = 13] = 3 +/- 4%, p = 0,0001), and the number of patients w ith a significant (greater than or equal to 15%) positive response (less th an or equal to 2 SD = 12 [100%], > 2 SD 13 SD = 11 [55%], > 3 SD less than or equal to 4 SD = 17 [49%], > 4 SD less than or equal to 5 SD = 3 [20%]; > 5 SD = 0%, p < 0,0001) decreased. There were no differences in dobutamine improvement among the subgroups with (n = 84) or without (n = 11) significa nt stenosis in the infarction artery (18 +/- 15 vs 16 +/- 18%), or between the subgroups with a patent (n = 76, 18 +/- 19%) or occluded (n = 19, 11 +/ - 11%) artery. Conclusions. Dobutamine response is related to dysfunction severity in the infarction area: when the severity is less than or equal to 2 (high positiv e response prevalence) or > 5 (high negative response prevalence), dobutami ne testing does not seem indicate. The existence of residual coronary steno sis does not attenuate contractile reserve at low dobutamine doses.