REGIONAL CARDIAC ADRENERGIC-FUNCTION USING I-123 METAIODOBENZYLGUANIDINE TOMOGRAPHIC IMAGING AFTER ACUTE MYOCARDIAL-INFARCTION

The effect of acute myocardial infarction (AMI) on regional cardiac adrenergic function was studied in 27 patients mean +/- standard deviation 10 +/- 4 days after AMI. Regional adrenergic function was evaluated noninvasively with I-123 meta-iodobenzylguanidine (MIBG) using a dedicated 3-detector tomograph. Four hours after its administration, there was reduced MIBG uptake in the region of infarction, 0.38 +/- 0.31 counts/pixel/mCi X 103 compared with 0.60 +/- 0.30 counts/pixel/mCi X 103 and 0.92 +/- 0.35 counts/pixel/mCi X 103 in the zones bordering and distant from the infarct area, respectively, p < 0.001. In all patients, the area of reduced MIBG uptake after 4 hours was more extensive than the associated thallium-201 perfusion defect with defect scores of 52 +/- 22 and 23 +/- 18%, respectively, p < 0.001. After anterior wall AMI, the 4-hour MIBG defect score was 70 +/- 13% and the degree of mismatch between myocardial perfusion and MIBG uptake was 30 +/- 9% compared with 39 +/- 17 and 21 +/- 17% after inferior AMI, p < 0.001 and p = 0.016, respectively. The 4-hour MIBG defect score correlated inversely with the predischarge left ventricular ejection fraction, r = -0.73, p < 0.001. Patients with ventricular arrhythmia of greater-than-or-equal-to 1 ventricular premature complexes per hour, paired ventricular premature complexes or ventricular tachycardia detected during the late hospital phase had higher 4-hour MIBG defect scores, 62.5 +/- 15.0%, than patients with no detectable complex ventricular ectopic activity and a ventricular premature complex frequency of < 1 per hour, 44.6 +/- 23.4%, p = 0.036. These data suggest that after acute AMI in humans (1) the abnormality in adrenergic function is more extensive than the associated abnormality in myocardial perfusion; (2) anterior wall AMI is associated with greater disruption of cardiac adrenergic function than other infarcts; (3) the severity of cardiac adrenergic dysfunction correlates with the degree of left ventricular dysfunction; and (4) the abnormality in regional adrenergic function may be associated with the presence of ventricular ectopic activity after AMI.