Mechanical contraction to guide CRT left-ventricular lead placement instead of electrical activation in myocardial infarction with left ventricular dysfunction: An experimental study based on non-invasive gated myocardial perfusion imaging and invasive electroanatomic mapping

A novel method combining gated SPECT and vectorcardiography to guide left ventricular lead placement to improve response to cardiac resynchronization therapy: A proof of concept study

BACKGROUND

The segment of the latest mechanical contraction (LMC) does not always overlap with the site of the latest electrical activation (LEA). By integrating both mechanical and electrical dyssynchrony, this proof-of-concept study aimed to propose a new method for recommending left ventricular (LV) lead placements, with the goal of enhancing response to cardiac resynchronization therapy (CRT).

METHODS

The LMC segment was determined by single-photon emission computed tomography myocardial perfusion imaging (SPECT MPI) phase analysis. The LEA site was detected by vectorcardiogram. The recommended segments for LV lead placement were as follows: (1) the LMC viable segments that overlapped with the LEA site; (2) the LMC viable segments adjacent to the LEA site; (3) If no segment met either of the above, the LV lateral wall was recommended. The response was defined as ≥15% reduction in left ventricular end-systolic volume (LVESV) 6-months after CRT. Patients with LV lead located in the recommended site were assigned to the recommended group, and those located in the non-recommended site were assigned to the non-recommended group.

RESULTS

The cohort comprised of 76 patients, including 54 (71.1%) in the recommended group and 22 (28.9%) in the non-recommended group. Among the recommended group, 74.1% of the patients responded to CRT, while 36.4% in the non-recommended group were responders (P = .002). Compared to pacing at the non-recommended segments, pacing at the recommended segments showed an independent association with an increased response by univariate and multivariable analysis (odds ratio 5.00, 95% confidence interval 1.73-14.44, P = .003; odds ratio 7.33, 95% confidence interval 1.53-35.14, P = .013). Kaplan-Meier curves showed that pacing at the recommended LV lead position demonstrated a better long-term prognosis.

CONCLUSION

Our findings indicate that pacing at the recommended segments, by integrating of mechanical and electrical dyssynchrony, is significantly associated with an improved CRT response and better long-term prognosis.

Longitudinal evaluation of diastolic dyssynchrony by SPECT gated myocardial perfusion imaging early after acute myocardial infarction and the relationship with left ventricular remodeling progression in a swine model

BACKGROUND

Left ventricular diastolic dyssynchrony (LVDD), a dyssynchronous relaxation pattern, has been known to develop after myocardial damage. We aimed to evaluate the dynamic changes in LVDD in the early stage of acute myocardial infarction (AMI) by phase analysis of 99mtechnetium methoxyisobutylisonitrile (99mTc-MIBI) single-photon emission computed tomography (SPECT) gated myocardial perfusion imaging (GMPI) and explore its relationship with the progression of left ventricular remodeling (LVR).

METHODS

The left anterior descending coronary arteries of 16 Bama miniature swine were occluded with a balloon to build AMI models. Animals were imaged by SPECT GMPI before AMI and at 1 day, 1 week and 4 weeks after AMI, and quantitative analysis was performed to determine the extent of left ventricle (LV) perfusion defects, left ventricular systolic dyssynchrony (LVSD) and the LVDD parameters: phase histogram bandwidth (PBW) and phase standard deviation (PSD). Echocardiography was simultaneously applied to evaluate left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV), left ventricular ejection fraction (LVEF), and the LVDD parameters: Te-12-diff and Te-12-SD. Myocardial injury markers were measured, and 12-lead ECGs were performed. The degree of LVR progression was defined as ΔLVESV (%) = (LVESVAMI4weeks - LVESVAMI1day)/LVESVAMI1day.

RESULTS

Thirteen swine completed the study. LVDD parameters changed dynamically at different time points after AMI. LVDD occurred as early as 1 day after AMI, peaked at 1 week, and trended toward a partial recovery at 4 weeks. Phase analysis on SPECT GMPI showed a significant correlation with tissue Doppler imaging for the assessment of LVDD during the longitudinal evaluation (r = 0.569 to 0.787, both P <0.05). During the univariate and multivariate regression analyses, the LVDD parameters PBW and PSD as of 1 day after AMI were significantly associated with the progression of LVR, respectively (PBW, β = 0.004, 95% CI 0.001 to 0.007, P = 0.024; PSD, β = 0.008, 95% CI 0.000 to 0.017, P = 0.049). Adjusted smooth curve fitting and threshold effect analysis indicated PBW and PSD break-point values of 142° and 60.4°, respectively, to predict the progression of LVR after AMI.

CONCLUSIONS

Phase analysis of SPECT GMPI can accurately and reliably characterize LVDD. LVDD occurred on the first day after AMI, reached its peak at 1 week, and partially recovered at 4 weeks after AMI. LVDD as evaluated by phase analysis of SPECT GMPI early after AMI was significantly associated with the progression of LVR. The early assessment of LVDD after AMI may provide helpful information for predicting the progression of LVR in the future.

Left ventricular mechanical dyssynchrony analzyed by Tc-99m sestamibi SPECT and F-18 FDG PET in patients with ischemic cardiomyopathy and the prognostic value

To compare the left ventricular (LV) phase dyssynchrony parameters obtained from Tc-99m Sestamibi SPECT (GSPECT) and F-18 FDG PET(GPET), as well as the prognostic values in patients with ischemic cardiomyopathy (ICM). Consecutive ICM patients referred for myocardial viability assessment were retrospectively evaluated and were followed-up for 21 ± 5 months. Phase parameter from both GSPECT and GPET were analyzed by QGS software, including histogram bandwidth (BW), standard deviation (SD) and entropy. Independent predictor for cardiac death was analyzed by Cox regression analysis. The estimated cardiac survival curve was analyzed by and was compared with the log-rank test. Eight-eight (mean age 56 ± 10, male 94%, LVEFSPECT23 ± 10%) ICM patients were included for analysis. Moderate correlations were observed for BW (r = 0.65; p < 0.001), SD (r = 0.63; p < 0.001) and entropy (r = 0.73; p < 0.001) between GSPECT and GPET. Among all covariates, the extent of myocardial scar was significantly associated with the differences of SD (r = 0.22; p < 0.05) and entropy (r = - 0.7; p < 0.05), whereas the extent of myocardial viability was not (all p > 0.05). Entropy measured by GSPECT was the predictor for cardiac death (p = 0.037) while QRS duration was not. The cardiac survival of patients with a high entropy (≥ 59%) was significantly lower than that of patients with low entropy (< 59%) (p < 0.05). GSPECT and GPET-derived phase parameters were not interchangeable in ICM patients. Patients with LV dyssynchrony measured by gated SPECT were associated with a worse outcome.

Functional significance of post-myocardial infarction inflammation evaluated by 18F-fluorodeoxyglucose imaging in swine model

BACKGROUND

The aim of the study was to investigate the relationship between post-myocardial infarction (MI) inflammation and left ventricular (LV) remodeling in a swine model by 18F-fluorodeoxyglucose (FDG) imaging.

METHODS

MI was induced in swine by balloon occlusion of the left anterior descending coronary artery. A series of FDG positron emission tomography (PET) images were taken within 2 weeks post-MI, employing a comprehensive strategy to suppress the physiological uptake of cardiomyocytes. Echocardiography was applied to evaluate LV volume, global and regional function. CD68+ macrophage and glucose transporters (GLUT-1, -3 and -4) were investigated by immunostaining.

RESULTS

The physiological uptake of myocardium was adequately suppressed in 92.3% of PET scans verified by visual analysis, which was further confirmed by the minimal expression of myocardial GLUT-4. Higher FDG uptake was observed in the infarct than in the remote area and persisted within the observational period of 2 weeks. The FDG uptake of infarcted myocardium on day 1 post-MI was correlated with LV global remodeling, and the FDG uptake of infarcted myocardium on days 1 and 8 post-MI had a trend of correlating with regional remodeling of the infarct area.

CONCLUSIONS

We here report a feasible swine model for investigating post-MI inflammation. FDG signal in the infarct area of swine persisted for a longer duration than has been reported in small animals. FDG activity in the infarct area could predict LV remodeling.