Non-invasive assessment of myocardial perfusion by intravenous contrast echocardiography: state of the art.

Many technical problems, related to both imaging instrumentation and contrast agents, have to be taken into account before attempting non-invasive evaluation of myocardial perfusion by intravenous contrast media injection. Potentials and pitfalls of first generation contrast agents (i.e. Levovist, Schering AG, Berlin, Germany) using intermittent harmonic angio imaging and of second generation contrast media (i.e. SonoVue, Bracco SpA, Milan, Italy) using real-time perfusion imaging in the non-invasive assessment of myocardial perfusion were described and discussed. We still need more solid data before introducing intravenous myocardial echocardiography into the clinical arena. However, convincing data from several research laboratories are paving the way for the widespread use of this new method in clinical practice.

Detection of residual tissue viability within the infarct zone in patients with acute myocardial infarction: ultrasonic integrated backscatter analysis versus dobutamine stress echocardiography.

OBJECTIVES: The goals of this study were to analyze temporal changes in cardiac cyclic variation of integrated backscatter (CVIB) in acute myocardial infarction (AMI) and to investigate the predictive value of CVIB normalization compared with that of dobutamine stress echocardiography (DSE) in the assessment of functional recovery after revascularization. BACKGROUND: The normal CVIB is blunted by ischemia and recovers early after reperfusion, faster than wall motion improvement. Analysis of CVIB has been widely investigated for its potential to detect viable myocardium in the early stage of infarction. No studies have compared CVIB analysis with other techniques for viability assessment in patients with acute ischemic. METHODS AND RESULTS: Integrated backscatter images were obtained in 12 patients with AMI on days 1, 3, and 7 after admission and 1 month after revascularization. On day 7, DSE was performed in all patients. On admission, 22 of 144 segments were dyssynergic. On day 1, CVIB was abnormal in all 22 infarcted segments, on day 3, in 16, and on day 7, in only 10 infarcted segments. Eight of 10 segments nonviable by CVIB (CVIB-nonviable) were also nonrespondent by DSE; whereas 12 of 14 segments viable by DSE (DSE-viable) were also CVIB-viable. At follow-up, 10 CVIB-viable segments and 1 CVIB-nonviable segment showed functional recovery; whereas 10 of 14 DSE-viable segments showed functional recovery. Thus the positive predictive value of CVIB and DSE was 83% and 72%, respectively, with a diagnostic agreement between techniques in 77% of segments. CONCLUSIONS: Our data suggest that the normalization in CVIB in the first week after AMI accurately predicts residual tissue viability within the infarct zone. We also observed that the initial pattern of cyclic variation may be predictive of functional recovery. Finally, we found a good correlation between the recovery of a normal CVIB in segments that were still dysfunctional and a more validated method to assess tissue viability, such as the dobutamine test.

The complex relation between myocardial viability and functional recovery in chronic left ventricular dysfunction.

Preserved myocardial viability and recurrent symptomatic ischemia are the most widely accepted criteria indicating that coronary revascularization should take place in patients with postischemic left ventricular dysfunction. However, the presence of viable myocardium within the infarct zone does not necessarily imply recovery of function after coronary revascularization. The complex relation between the extent of transmural necrosis and the degree of residual perfusion within the infarct area plays an important role. However, independently of functional recovery, cell viability may have important clinical implications, since it may improve long-term prognosis by attenuating left ventricular remodeling processes. Several different methods are used to detect hibernating myocardium. Mounting evidence suggests that thallium-201 scintigraphy is most sensitive in identifying tissue viability, whereas dobutamine echocardiography is most specific in predicting functional recovery after revascularization. In between, myocardial contrast echocardiography is the only technique able to evaluate the microvascular integrity that is a condition sine qua non for both cell viability and later functional recovery. Combined information derived from these 3 different approaches might be considered as the best way to understand how the combination of contractile, viable but noncontractile, and dead tissue affect resultant function and prognosis.