Gated metabolic myocardial imaging, a surrogate for dual perfusion-metabolism imaging by positron emission tomography.

OBJECTIVE: Perfusion-metabolism mismatch pattern on positron emission tomography (PET) predicts hibernating myocardium. We assess the ECG-gated metabolic PET as a surrogate for the perfusion-metabolism mismatch pattern on PET imaging. METHODS: 13N-Ammonia (NH3) and 18F-fluorodeoxyglucose (FDG) are respectively perfusion and metabolism PET tracers. We used ECG gating to acquire FDG-PET to collect wall thickening (mechanical) data. These allow detection of metabolic activity in regions with reduced contraction (metabolism-mechanical mismatch pattern). We had two data sets on each patient: perfusion-metabolism and metabolism-mechanical data sets. We tested the hypothesis that metabolism-mechanical pattern on PET could predict perfusion-metabolism mismatch pattern. RESULTS: We studied 55 patients (48 males), mean age 62 years. All were in sinus rhythm, and had impaired left ventricular contraction. Perfusion-metabolism mismatch pattern was found in 26 patients. Metabolism-mechanical mismatch pattern was found in 25 patients. The results were concordant in 52 patients (95%). As a surrogate for perfusion-metabolism mismatch pattern, demonstration of metabolism-mechanical mismatch pattern is highly sensitive (92%) and specific (97%). In this cohort, the positive and negative predictive accuracy of the new method are 96% and 93%, respectively. CONCLUSION: Metabolism-mechanical mismatch pattern could predict perfusion-metabolism mismatch pattern in patients with myocardial viability criteria on PET. Prospective validation against the gold standard of improved myocardial contraction after revascularisation is needed.

Characterization of viability, scarring and hibernation of the myocardium supplied by epicardial coronary arteries with low flow grades.

OBJECTIVE: The aim of this study was to analyse the relationship between reduced coronary artery flow and myocardial viability, scarring and hibernation. PATIENTS AND METHODS: Coronary flow grades and collateral vessels were scored using the thrombolysis in myocardial infarction trial (TIMI) and the Rentrop and Cohen scoring systems, respectively. N-ammonia and fluorine-18-fluorodeoxyglucose (F-FDG) are the perfusion and metabolic markers on PET, respectively. The left ventricle was divided into three coronary territories. The area with the highest N-ammonia uptake was considered the reference region. Myocardial regions with F-FDG uptake of at least 50% of the reference region were considered viable and those with F-FDG uptake less than 50% of the reference region were considered scarred. Hibernation was considered present if the viable myocardium had significant wall motion abnormality. RESULTS: There were 80 (71 males) patients with 240 myocardial territories. TIMI 2-3 arteries supplied 151 regions (group A), and 89 regions were supplied by TIMI 0-1 arteries (group B). Viable myocardium was present in 140 (93%) regions of group A and in 76 (85%) regions of group B (P=0.068). Scarring was present in 40 (26%) regions in group A and in 49 (55%) regions in group B (P<0.0001). Wall motion data were available in 215 regions: 133 regions in group A and 82 regions in group B. Hibernating myocardium was predicted in 36 (28%) regions in group A and in 34 (41%) regions in group B (P<0.05). CONCLUSION: Myocardial regions supplied by arteries with TIMI 0-1 are characterized by significantly increased incidence of hibernation and scarring. Video abstract: http://links.lww.com/NMC/A115.

The relationship between transmural extent of infarction on contrast enhanced magnetic resonance imaging and recovery of contractile function in patients with first myocardial infarction treated with thrombolysis.

BACKGROUND: The aim of the current study was to assess the utility of transmurality of delayed enhancement on cardiac magnetic resonance imaging (MRI) in predicting functional recovery in patients with first ST-elevation myocardial infarction (MI) who had received thrombolysis. METHODS: Nineteen patients underwent cine and contrast-enhanced MRI 3 days and 8 weeks after MI. The transmural extent of infarction (TEI) was determined from the late enhancement component of the first scan. Segmental wall thickening was scored from the cine components of both the initial and follow-up scans. RESULTS: The TEI was inversely related to the likelihood of improvement in wall thickening; chi(2) test for trend = 53.9, p < 0.0001. Delayed enhancement with >50% transmurality predicted a lack of recovery with 82% sensitivity and 54% specificity. The equivalent values for >75% transmurality were 57 and 77%, respectively. The proportion of the left ventricular segments exhibiting functional recovery was related to the percentage of the left ventricle that was severely dysfunctional but had