The role of nuclear medicine in assessments of cardiac dyssynchrony

Evaluation of biventricular function by cadmium-zinc-telluride SPECT gated tomographic radionuclide angiography: Comparison to conventional SPECT

We compared and analyzed the consistency and repeatability of left and right ventricular ((LV/RV) functions obtained by gated-equilibrium radionuclide ventriculography (ERNV) with cadmium-zinc-telluride single-photon emission computed tomography (CZT-SPECT) and conventional SPECT (C-SPECT) with sodium iodide crystal detectors. Seventy-seven patients were included in the retrospective study. Both C-SPECT and CZT-SPECT imaging were performed on the same day. Correlations and differences in LV/RV ejection fraction (LVEF and RVEF), peak ejection rate (PER), and peak filling rate (PFR) were compared between the 2 models. Cardiac magnetic resonance (CMR) was partially used as the gold standard, and ultrasound results were included for comparative analysis. Interobserver reproducibility of each parameter obtained by the 2 cameras was compared. Between the 2 cameras, there were no significant difference in LVEF, LVPER, LVPFR, and RVPER (P > .05) and there were in RVEF and RVPFR (P < .05 or .001). The correlations (R value) were 0.831 (LVEF, excellent), 0.619 (RVEF, good), 0.672 (LVPER, good), 0.700 (LVPFR, good), 0.463 (RVPER, normal), and 0.253 (RVPFR, poor). There were no significant difference between CMR and CZT-SPECT in LVEF (P > .05) while there were between CMR and both C-SPECT and ultrasound (P < .05). The correlations were all good (R = 0.660, 0.658, and 0.695). There were no significant difference between CMR and both C-SPECT and CZT-SPET in RVEF (P > .05) and the correlations were good (R = 0.771 and 0.745). For repeatability, the intraclass correlation coefficient of RVPFR by C-SPECT was good (intraclass correlation coefficient = 0.698) and excellent for the rest of the groups (0.823-0.989). The repeatability of LVEF and RVEF was better for CZT-SPECT than for C-SPECT. The repeatability of PER was better for both cameras than PFR. CZT-SPECT tomographic ERNV correlated well with C-SPECT planar ERNV in evaluation of biventricular systolic function and LV diastolic function. Compared with the "gold standard" CMR, both models had good correlation in measuring LV/RVEF. CZT-SPECT had better inter-group reproducibility than C-SPECT. The accuracy of RV diastolic function need further study. CZT-SPECT tomographic ERNV will play an important and unique role in the clinical application of accurate evaluation of biventricular function in the future.

Mechanical dyssynchrony: How do we measure it, what it means, and what we can do about it

Left ventricular mechanical dyssynchrony (LVMD) is defined by a difference in the timing of mechanical contraction or relaxation between different segments of the left ventricle (LV). Mechanical dyssynchrony is distinct from electrical dyssynchrony as measured by QRS duration and has been of increasing interest due to its association with worse prognosis and potential role in patient selection for cardiac resynchronization therapy (CRT). Although echocardiography is the most used modality to assess LVMD, some limitations apply to this modality. Compared to echo-based modalities, nuclear imaging by gated single-photon emission computed tomography (GSPECT) myocardial perfusion imaging (MPI) has clear advantages in evaluating systolic and diastolic LVMD. GSPECT MPI can determine systolic and diastolic mechanical dyssynchrony by the variability in the timing in which different LV segments contract or relax, which has prognostic impact in patients with coronary artery disease and heart failure. As such, by targeting mechanical dyssynchrony instead of electrical dyssynchrony, GSPECT MPI can potentially improve patient selection for CRT. So far, few studies have investigated the role of diastolic dyssynchrony, but recent evidence seems to suggest high prevalence and more prognostic impact than previously recognized. In the present review, we provide an oversight of mechanical dyssynchrony.

Gated single-photon emission computed tomography myocardial perfusion imaging phase analysis as an imaging biomarker for mortality prediction in heart failure patients undergoing cardiac resynchronization therapy

OBJECTIVE

Cardiac resynchronization therapy (CRT) reduces morbidity and mortality in heart failure patients. The purpose of this study was to assess the value of gated myocardial perfusion single-photon emission computed tomography (GMPS) phase analysis for predicting survival in heart failure patients undergoing CRT.

METHODS

This retrospective cohort study evaluated heart failure patients who underwent GMPS prior to CRT. Phase histogram bandwidth (PHB) and phase SD (PSD) were calculated using GMPS data. Cox proportional hazards model was used to identify independent predictors of overall survival (OS).

RESULTS

A total of 35 patients (age 65.1 ± 13.3, 27 men and 8 women), who were followed for mean of 4.1 ± 2.9 years, were enrolled in the study. PSD of greater than 45° was found to be an independent predictor of poor OS (hazard ratio = 12.63, P = 0.011) when compared with age (hazard ratio = 1.00, P = 0.922), gender (hazard ratio = 0.31, P = 0.155), NYHA class (hazard ratio = 0.45, P = 0.087), QRS duration greater than 150 ms (hazard ratio = 2.38, P = 0.401), pre-CRT left ventricular ejection fraction (LVEF) (hazard ratio = 0.95, P = 0.175) and etiology of heart failure (hazard ratio = 1.42, P = 0.641). Furthermore, PHB greater than 140° was also found to be an independent predictor of poor OS (hazard ratio = 5.63, P = 0.040) when compared with age, gender, NYHA class, QRS duration greater than 150 ms, pre-CRT LVEF and etiology of heart failure.

CONCLUSIONS

PSD and PHB, measured by GMPS, may serve as biomarkers for the prediction of survival in patients undergoing CRT.

The rate of myocardial perfusion recovery after steroid therapy and its implication for cardiac events in cardiac sarcoidosis and primarily preserved left ventricular ejection fraction

BACKGROUND

Sarcoidosis is a multisystemic disorder of unknown cause characterized by immune granuloma formation in the involved organs. Few studies have reported on the myocardial perfusion changes by immunosuppression therapy in cardiac sarcoidosis (CS). Additionally, the relationship between myocardial perfusion changes and prognosis is unknown. Therefore, this study aimed to clarify myocardial perfusion recovery after steroid therapy and its prognostic value for major adverse cardiac events (MACE) in patients with CS.

METHODS AND RESULTS

Thirty-eight consecutive patients with CS {median age, 63 [interquartile range (IQR) 51-68] years; 10 men} underwent both 18F-fluorodeoxyglucose positron emission tomography/computed tomography (CT) and electrocardiography-gated single-photon emission CT (SPECT) pre- and post-steroid therapy. Patients with improved or preserved myocardial perfusion after post-therapy were defined as the recovery group and those with worsened myocardial perfusion as the non-recovery group. Twenty-six patients (68%) were categorized as the recovery group. MACE occurred in eight patients. The Kaplan-Meier curves revealed a significantly higher rate of MACE in the non-recovery group (17.4%/y vs 2.9%/y, P = 0.007).

CONCLUSIONS

Myocardial perfusion was recovered by steroid therapy in 61% and preserved in 8% of patients. Myocardial perfusion recovery after steroid therapy was significantly associated with a low incidence of MACE.

Prognostic value of phase analysis on gated single photon emission computed tomography in patients with cardiac sarcoidosis

BACKGROUND

We aimed to determine the correlation between phase analysis, reflecting the heterogeneity of perfusion defects, and the dyssynchrony of the left ventricle wall motion, and adverse cardiac events in cardiac sarcoidosis (CS) patients.

METHODS

Fifty-seven consecutive patients with diagnosed CS (64 [IQR 55-71] years old, 14 males), who underwent 18F-FDG PET/CT and ECG-gated SPECT, were studied. FDG PET was analysed to measure cardiac metabolic volume (CMV), and total lesion glycolysis (TLG). The SPECT findings, such as LVEF, Summed Rest Score (SRS), bandwidth (BW) were evaluated.

RESULTS

The median of BW was 56° (IQR 40-95). BW showed a strong inverse correlation with LVEF (r = - 0.60, P < 0.0001), and positive correlation with SRS (r = 0.82, P < 0.0001). However, there were no significant correlations between BW and CMV or TLG. The Kaplan-Meier curves revealed a significantly higher rate of MACE in the high BW group (BW > 56°) than the low BW group (BW ≤ 56°) (15.1%/years vs. 4.4%/years, P = 0.025). In multivariable analysis, BW was a significant independent predictor of MACE (P = 0.015).

CONCLUSION

Phase analysis on gated SPECT was a significant and independent predictor of MACE in patients with CS.

Prognostic value of SPECT myocardial perfusion entropy in high-risk type 2 diabetic patients

PURPOSE

Risk stratification of patients with type 2 diabetes mellitus (T2D) remains suboptimal. We hypothesized that myocardial perfusion entropy (MPE) quantified from SPECT myocardial perfusion images may provide incremental prognostic value in T2D patients independently from myocardial ischemia.

METHODS

T2D patients with very high and high cardiovascular risk were prospectively included (n = 166, 65 ± 12 years). Stress perfusion defect was quantified by visual evaluation of SPECT MPI. SPECT MPI was also used for the quantification of rest and stress MPE. The primary end point was major adverse cardiac events (MACEs) defined as cardiac death, myocardial infarction (MI), and myocardial revascularization > 3 months after SPECT.

RESULTS

Forty-four MACEs were observed during a 4.6-year median follow-up. Significant differences in stress MPE were observed between patients with and without MACEs (4.19 ± 0.46 vs. 3.93 ± 0.40; P ≤ .01). By Kaplan-Meier analysis, the risk of MACEs was significantly higher in patients with higher stress MPE (log-rank P ≤ 01). Stress MPE and stress perfusion defect (SSS ≥ 4) were significantly associated with the risk of MACEs (hazard ratio 2.77 and 2.06, respectively, P < .05 for both) after adjustment for clinical and imaging risk predictors as identified from preliminary univariate analysis. MPE demonstrated incremental prognostic value over clinical risk factors, stress test EKG and SSS as evidenced by nested models showing improved Akaike information criterion (AIC), reclassification (global continuous net reclassification improvement [NRI]: 63), global integrated discrimination improvement (IDI: 6%), and discrimination (change in c-statistic: 0.66 vs 0.74).

CONCLUSIONS

Stress MPE provided independent and incremental prognostic information for the prediction of MACEs in diabetic patients.

TRIAL REGISTRATION NUMBER

NCT02316054 (12/12/2014).