Phase analysis on gated single photon emission computed tomography (SPECT) myocardial perfusion imaging with ^99mTc-Sestamibi as a prognostic marker for cardiovascular dysfunction in patients with end stage liver disease

Objectives: Phase analysis parameters on gated SPECT myocardial perfusion imaging (MPI) have been proven reliable in assessment of left ventricular mechanical dyssynchrony (LVMD). Patients with end-stage liver disease (ESLD) are known to develop cardiovascular complications, especially in the form of cirrhotic cardiomyopathy. This entity, while mostly occult can lead to major adverse cardiac events (MACEs), thus increasing morbidity and mortality in ESLD patients posted for liver transplantation (LT). As part of the pre-transplant workup, the patients are routinely subjected to echocardiography and stress SPECT MPI for coronary circulation and cardiac function assessment. However, since most patients have a reserved ejection fraction, regional wall motion and coronary perfusion, these modalities are of little help in identifying the at-risk patients at an early stage. The present study was conducted to evaluate the role of phase analysis parameters in assessment of LVMD in these patients versus the control population, and whether it could provide prognostic information in terms of risk of development of MACEs.

Methods: ESLD patients, undergoing stress MPI for pre-operative assessment for LT were evaluated for possible inclusion in the study. Patients with a prior cardiac ailment, history of hypertension, Diabetes mellitus, coronary intervention, arrhythmia on gating, abnormal QRS duration (>120 ms), perfusion defect (s) and wall motion abnormality in gated stress SPECT-MPI were excluded from the study. 64 candidates (32 patients with ESLD and 32 age and gender matched controls) were enrolled in the present study. Pharmacologic stress with adenosine was used for stress MPI in all candidates. The control population was used to assess the normal phase parameters on SPECT-MPI. Phase analysis was performed on post-stress acquired data with Emory Cardiac Toolbox-SyncTool. Phase standard deviation (PSD, unit: degree) and 95% width of phase bandwidth (PBW, unit: degree) were used as quantitative parameters for comparison between the two groups. Demographic and clinical variables were also compared between the two groups to exclude potential confounders. All candidates were followed up for the occurrence of any cardiac adverse events.

Results: Phase analysis on SPECT MPI was done in 32 patients of ESLD (25 men, 7 women, mean 46.13±8.9 years) and 32 controls (25 men, 7 women, mean 46.19±7.09 years). Mean PSD and PBW in patients with ESLD were 11.81±5.01 and 38.56±17.97 respectively while that in the control group were 7.08±1.63 and 23.19±5.47, respectively. The differences in both PSD and PBW values among the two groups were extremely statistically significant (P<0.0001). The PSD and PBW values from the control group were used to create a cut-off for defining significant LVMD, using mean + 2 SD which yielded PSD>10.34 and PBW>34.13. Based on these values, 16/32 patients with ESLD were found to have significant LVMD. On follow-up (mean 16.6±12.1 months), four candidates were found to develop MACEs, all of them being ESLD patients with significant LVMD. This difference in the occurrence of MACEs in patients of ESLD with and without significant LVMD was statistically significant (P<0.05).

Conclusions: ESLD patients with significant LVMD have a higher risk of developing MACEs compared to those without significant LVMD. Since both these group of patients had normal perfusion on stress SPECT MPI and a normal echocardiogram, phase analysis can be a potential prognostic marker in the identification of the at-risk patients.