Contractile Reserve versus Cell Membrane Integrity for Predicting Contractile Recovery after Reperfusion in Acute Myocardial Infarction and Their Relationship

ABSTRACT

BACKGROUND: Early prediction of functional recovery could have very important prognostic and therapeutic implication. Modalities evaluating functional recovery of dysynergic segments have included metabolic and perfusion imaging as well as assessment of contractile reserve in response to inotropic agent. Dobutamine stress echocardiography(DSE) assesses contractile reserve whereas rest and 24hr delayed Tl-201 SPECT(T1-201) assesses cell membrane integrity. Does contractile reserve always imply cell membrane integrity? If not, which one could be more useful predictor of contractile recovery of the infarcted segment after restoration of the infarct related artery(IRA) in acute myocardial infarction(AMI)? The aim of this study was to evaluate comparative accuracy of contractile reserve and cell membrane integrity in predicting contractile recovery and their relation. METHODS: We prospectively compared DSE with Tl-201 in 22 of 34 patients with acute myocardial infarction from August 1996 to September 1997. AU patients underwent coronary angiography and got revascularization treatment if they had significant stenosis. DSE and Tl-201 were done within 24hrs after successful restoration without flow limiting residual stenosis. An intravenous infusion of dobutamine(5(mg/kg/min) was started with an infusion pump and continued in 3-minute dose increment up to 20(mg/kg/min under continuous ECG and echocardiographic monitoring. Regional wall motion was assessed according to 16-segment model from American Society of Echocardiography recommendation. Wall motion was scored as 1 (normal), 2(mild to moderate hypokinesia), 3(severe hypokinesia), 4(akinesia), 5(dyskinesia). The improvement of wall motion score(WMS) more than 1 from asynergy during dobutmine infusion was considered to have contractile reserve. SPECT images were obtained at rest and 24hours later. The Tl-201 images were analyzed visually according to 16 segment model, scored by grade 0: normal uptake, 1: mild to moderate decreased, 2: severe decreased, 3: defect. Those segments were considered to have a cellular integrity if the defect at rest improved more than grade 1 on delayed images. All patients underwent 1 month follow up echocardiography after discharge. The improvement of WMS more than score 1 from asynergy at follow up was considered to have contractile recovery. RESULTS: 71 akinetic segments out of total of 352 segments were analyzed. There was no significant difference of sensitivity(88 vs 82%), specificity(82 vs 82%), and accuracy(86 vs 81%) in predicting contractile recovery between DSE and Tl-201. The agreement between contractile reserve and cellular integrity was 73% with kappa value of 0.42(p=0.001). CONCLUSION: Contractile reserve has similar sensitivity, specificity and predictive value with cell membrane integrity in predicting contractile recovery. However contractile reserve immediately after restoration does not necessarily imply cell membrane integrity in acute myocardial inFarction.