The amount of dysfunctional but viable myocardium predicts long-term survival in patients with ischemic cardiomyopathy and left ventricular dysfunction

Abstract

To evaluate the prognostic significance of combined myocardial perfusion SPECT and [18F]FDG PET viability scanning for the prediction of survival in patients with ischemic cardiomyopathy (iCMP) and left ventricular dysfunction. 244 patients (64.0 ± 10.6 years, 86 % men) with iCMP and LVEF ≤ 45 % underwent SPECT/PET. Percent scar tissue and SPECT/PET-mismatch (%-mismatch) were calculated and correlated with event-free survival according to the type of therapy (medical therapy with/out revascularization) provided after imaging. Death from any cause was defined as the primary endpoint. Early revascularization (ER) was performed in 113/244 (46 %) patients within 32 ± 52 days (26 bypass surgeries and 87 percutaneous coronary interventions). 65 patients died during follow-up for a median of 33 months. Kaplan-Meier analysis showed that those patients with ≥ 5 % mismatch not undergoing ER had significantly higher mortality than did the group with similar mismatch who did receive ER. Cox analysis identified both SPECT/PET-mismatch and the interaction of SPECT/PET-mismatch with ER as independent predictors for death due to all causes. A threshold of ≥ 5 % SPECT/PET-mismatch predicted best which patients with iCMP and LV dysfunction would benefit from ER in terms of long-term survival.

Single Photon Emission Computed Tomography (SPECT) Myocardial Perfusion Imaging Guidelines: Instrumentation, Acquisition, Processing, and Interpretation

“…Pixels of perfusion defect with counts [ 2 standard deviations below gender matched normal limits database are considered nonviable. 145 Notably, the extent of viability (greater than 10% hibernating myocardium) 146 is an important determinant of recovery of LV function Optional Semiquantitative (small, 1-2 segments; medium 3-4 segments; large C 5 segments) Required Quantitative (small \10%; medium 10-20%; large C20%) Required Severity Qualitative (mild, moderate, severe, absent tracer uptake) Optional Semiquantitative (score 0 = normal; mild or score 1 = 10% to \25% count reduction; moderate or score 2 = 25% to \50% count reduction; severe or score 3 = C50% reduction in counts; severe or score 4 (background counts) Required Quantitative (computer generated scores) Recommended Reversibility (fixed = no reversibility; mildly reversible; moderately reversible; predominantly reversible; predominantly fixed) Table 9 lists the threshold values and the physiological basis for determination of myocardial viability using clinically used radionuclides.…”

Myocardial viability

“…The presence of viability by any imaging modality (although mainly DSE and nuclear techniques) appeared to confer a significantly improved outcome in those undergoing revascularisation. These values were considerably higher than the mismatch threshold of 7% for PET identified in the substudy of PET and Recovery following Revascularisation (PARR-2) study [81] (discussed below) and of >5% in another retrospective analysis [82], highlighting the uncertainty in this area and the limitations of retrospective data. The beneficial effect of revascularisation on survival in patients with viability appeared to correlate to the severity of LV dysfunction.…”

The role of PET quantification in cardiovascular imaging

“…In a subsequent substudy of PARR-2 trial, the investigators found that in 182 patients with ischemic LV dysfunction, the risk for cardiac death, myocardial infarction or cardiac-related re-hospitalization is reduced when a quantitative mismatch variable is above 7% (28). Quantitative analysis of mismatch and scar was also recently applied by Ubleis et al (29) in 244 patients to evaluate the prognostic significance of 18 FDG PET viability scanning for the prediction of patients with ischemic cardiomyopathy and left ventricular dysfunction. Their analysis has shown that the patients with mismatch greater than 5% (as established by the quantitative software) who did not undergo early revascularization had significantly higher mortality than the group who had similar mismatch (≥ 5%) and did undergo the intervention.…”