Cardiac MRI viability study and its role in revascularization- Excerpts from a tertiary care cardiac centre
Authors: Ruia A , Muralidharan TR , Jebaraj R , Vinodkumar B , Murthy J S N , Thanikachalam S 
Published: July 2021

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
Assessment of cardiac viability based revascularization has not convincingly demonstrated, to improve patient outcomes statistically even by large trials like STITCH and PPAR-2 using SPECT and PET analysis. Here we used cardiac viability by cardiac MRI to guide us for revascularization and also found out problems arising in the statistical analysis for the same

Methods
It is a retrospective observational longitudinal follow up study whereby patients who had ischemic cardiomyopathy (confirmed with coronary angiogram) and who were admitted with features of heart failure or with acute coronary syndrome and who subsequently underwent cardiac MRI viability testing during the period from 1/02/2017 to 31/01/2020 were included. Patients were excluded who had non ischemic cardiomyopathy. Using cardiac MRI- LVEF, RVEF, Wall motion severity Index and Total viability percentage were additionally computed and analyzed. Patients were deemed having viable myocardium on ≤50% LGE in cardiac MRI and final treatment of CABG, PCI or only medical management was analyzed for the Primary end points of CV mortality, non-fatal CVA and non-fatal AMI

Results
Based on the criteria total of 94 patients were selected for the study, 53 patients kept on only medical management, 19 patients underwent PCI and 22 patients had CABG. The baseline characteristics of the study population were an average age of 60years, male (76%) with Diabetes Mellitus(69%) and Hypertension (41.5%) in them. Coronary Angiogram showed that 10.6% patients had LM involvement, 92% had LAD disease, 72% patients had LCX lesion and 74% had RCA disease. While average Echo LVEF was 35.82%, Cardiac MRI based mean LVEF was 30.78%. It was found that patients who were kept only on medical management had higher Wall motion Severity Index (2.05) over patients who were treated with PCI (1.94) or CABG (1.80) (p = 0.006). Also it was found that the Total viability percentage was less in patients kept only on medical management (74%) vs patients who were treated with PCI (78%) or CABG (77.8%)(p = 0.08) .It was found by cardiac MRI that patients with significant LAD lesions with viable LAD territory, those who underwent CABG or PCI based therapy had lesser mortality(7.69%,10%) over patients kept only on medical management (23%) (p = 0.407). Among patients with significant LAD lesions with non-viable LAD territory, those who underwent CABG or only medical management had lesser mortality (11.5%) than patients who underwent PCI (50%) (p = 0.137).
Conclusion(s)
Cardiac MRI based viability testing may guide the physician for optimal treatment but it does not reach statistical significance. The reasons maybe different arterial segments having different viability and anatomical hazards acting as cofounding factors. Viability being a continuum process does not follow a strict cut off of 50% LGE and 100% acute occluded vessel may not allow LGE.