Determination of Myocardial Viability with ECG-Gated Fluorodeoxyglucose F-18 Positron Emission Tomography

Incremental value of myocardial wall motion and thickening to perfusion alone by gated SPECT myocardial perfusion imaging for viability assessment in patients with ischemic heart failure

PURPOSE

The objective of this study was to assess the incremental value of myocardial wall motion and thickening compared with perfusion alone obtained from gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) in diagnosing myocardial viability in patients with ischemic heart failure.

METHODS

Eighty-three consecutive patients with ischemic heart failure who underwent both 99mTc-MIBI gated SPECT MPI and 18F-FDG positron emission tomography (PET) myocardial metabolic imaging were retrospectively enrolled. SPECT/PET myocardial viability was defined as the reference standard. Segmental myocardial perfusion, wall motion, and thickening were measured by an automated algorithm from gated SPECT MPI. Univariate and stepwise multivariate analysis were conducted to establish an optimal multivariate model for predicting hibernating myocardium and scar.

RESULTS

Among the 1411 segments evaluated, 774 segments had normal perfusion and 637 segments had decreased perfusion. The latter were classified by 18F-FDG PET into 338 hibernating segments and 299 scarred segments. The multivariate regression analysis showed that the model that combined myocardial perfusion uptake with wall motion and thickening scores had the optimal predictive efficiency to distinguish hibernating myocardium from scar in the segments with decreased perfusion. The model had the largest C-statistic (0.753 vs 0.666, P < 0.0001), and the global chi-square was increased from 53.281 to 111.234 when compared with perfusion alone (P < 0.001).

CONCLUSIONS

Assessment of myocardial wall motion and thickening in addition to conventional perfusion uptake in the segments with decreased perfusion enables better differentiation of hibernating myocardium from scar in patients with ischemic heart failure. Considering wide availability and high cost-effectiveness, regional myocardial function integrated with perfusion on gated SPECT MPI has great promise to become a clinical tool in the assessment of myocardial viability.

Prognostic performance of quantitative PET tools for stratification of patients with ischemic cardiomyopathy undergoing myocardial viability assessment

OBJECTIVES

This study was performed to determine the prognostic performance of quantitative PET tools in the stratification of patients with ischemic cardiomyopathy undergoing myocardial viability assessment.

METHODS

We applied four different quantitative tools to 104 consecutive patients with coronary artery disease and previous myocardial infarction who had undergone rest Rb/gated F-fluorodeoxyglucose (FDG) PET, to assess myocardial viability for potential revascularization. One of these tools was based on the FDG study alone and the other three tools assessed the extent of match/mismatch defects using FDG in comparison with a perfusion reference database. The four quantitative tools used in this research to define viability were (i) FDG alone, which calculates the percentage of left ventricular myocardium (LVM) that is above the 50% of the maximum LVM FDG counts, (ii) low flow match/mismatch, which determines the area with a 5% increase in normalized FDG counts in relation to defined resting perfusion defects as compared with a reference database, (iii) all regions match/mismatch, which computes the area with a 10% increase in normalized FDG counts in relation to the left ventricle resting perfusion distribution, and (iv) percentage max FDG match/mismatch, which defines the area with FDG uptake greater than 60% of the maximum LVM FDG counts within defined perfusion defects as determined by the reference database. The primary endpoint for this analysis was cardiac death.

RESULTS

During the follow-up period (22+/-14 months), 19 patients (18%) died; in 17 of these the cause of death was cardiac. Using univariate analysis, none of the methods were predictive of cardiac death. Receiver operating characteristic analysis defined the optimal thresholds for the extent of myocardial viability for the four tools in the prediction of cardiac death: FDG alone=20%, low flow match/mismatch=15%, all regions match/mismatch=35%, and percentage max FDG match/mismatch=20%. A censored survival analysis using a Kaplan-Meier method showed a statistically significant difference between patients with cardiac death and those with no cardiac death using only the low flow match/mismatch (hazard ratio=0.29, P=0.01) and percentage max FDG match/mismatch criteria (hazard ratio=0.23, P=0.005) tools.

CONCLUSION

The low flow match/mismatch and percentage max FDG match/mismatch quantitative PET tools are useful for prognostic stratification of patients with ischemic cardiomyopathy undergoing myocardial viability assessment.

Gated Listmode Acquisition with the QuadHIDAC Animal PET to Image Mouse Hearts* *This work was partly supported by grants from the Deutsche Forschungsgemeinschaft (DFG), Sonderforschungsbereich 656 MoBil Münster, Germany (project B3)

PURPOSE

The aim of this study was to develop ECG and respiratory gating in combination with listmode acquisition for the quadHIDAC small-animal PET scanner.

METHODS

ECG and respiratory gating was realized with the help of an external trigger device (BioVET) synchronized with the listmode acquisition. Listmode data of a mouse acquisition (injected with 6.5 MBq of 18F-FDG) were sorted according to three different gating definitions: 12 cardiac gates, 8 respiratory gates and a combination of 8 cardiac and 8 respiratory gates. Images were reconstructed with filtered back-projection (ramp filter), and parameters like left ventricular wall thickness (WT), wall-to-wall separation (WS) and blood to myocardium activity ratios (BMR) were calculated.

RESULTS

Cardiac gated images show improvement of all parameters (WT 2.6 mm, WS 4.1 mm, BRM 2.3) in diastole compared to ungated images (WT 3.0 mm, WS 3.4 mm, BMR 1.3). Respiratory gating had little effect on calculated parameters.

CONCLUSION

ECG gating with the quadHIDAC can improve myocardial image quality in mice. This could have a major impact on the calculation of an image-derived input function for kinetic modelling.

Incremental prognostic value of left ventricular function by myocardial ECG-gated FDG PET imaging in patients with ischemic cardiomyopathy

BACKGROUND

The purpose of this study was to determine the independent value of left ventricular (LV) functional parameters derived from gated fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) to predict prognosis in patients with ischemic cardiomyopathy undergoing myocardial viability assessment.

METHODS AND RESULTS

We studied 90 consecutive patients with coronary artery disease and low LV ejection fraction (26% +/- 7%) undergoing gated FDG PET to assess myocardial viability for potential revascularization. The primary endpoint for this analysis was the occurrence of cardiac death, myocardial infarction, or worsening heart failure (HF) to New York Heart Association class IV. During follow-up (22 +/- 14 months), 21 patients had an event (17 died, 4 had myocardial infarctions, and 4 had worsening HF). On Cox regression analysis, the event-free survival rate at 2 years was lower for patients with an end-diastolic volume (EDV) of 260 mL or greater (relative risk, 2.7; P = .014), end-systolic volume (ESV) of 200 mL or greater (relative risk, 2.5; P = .021), and LV mass of 143 g or greater (relative risk, 1.6; P = .009). In a risk-adjusted model, EDV (chi 2 = 68, P < .0001) and ESV (chi 2 = 75, P = .035) added a significant amount in the estimation of events over the perfusion-FDG mismatch pattern (chi 2 = 40, P < .001). In a stratified Cox model, patients with PET mismatch, LV ejection fraction lower than 25%, and EDV of 260 mL or greater had the lowest survival rate (P = .006). These patients showed an apparent survival benefit with revascularization but without an improvement in HF symptoms.

CONCLUSION

LV functional parameters determined by gated FDG PET have incremental prognostic value over viability information in patients with ischemic cardiomyopathy. Our data suggest that patients with residual viability and advanced cardiac remodeling are at high clinical risk. In these patients the apparent survival benefit of revascularization may not be associated with a measurable improvement in HF symptoms.