09 Jun 21. Featured Paper

Assessment of stunned & viable myocardium using manganese-enhanced MRI.

Link to paper on Open Heart

Authors

Nick B Spath, Trisha Singh, Giorgos Papanastasiou, Andrew Baker, Rob J Janiczek, Gerry P McCann, Marc R Dweck, Lucy Kershaw, David E Newby & Scott Semple

Abstract

Objective: In a proof-of-concept study, to quantify myocardial viability in patients with acute myocardial infarction using manganese-enhanced MRI (MEMRI), a measure of intracellular calcium handling.

Methods: Healthy volunteers (n=20) & patients with ST-elevation myocardial infarction (n=20) underwent late gadolinium enhancement (LGE) using gadobutrol & MEMRI using manganese dipyridoxyl diphosphate.

Patients were scanned ≤7 days after reperfusion & rescanned after 3 months.

Differential manganese uptake was described using a two-compartment model.

Results: After manganese administration, healthy control & remote non-infarcted myocardium showed a sustained 25% reduction in T1 values (mean reductions, 288±34 & 281±12 ms).

Infarcted myocardium demonstrated less T1 shortening than healthy control or remote myocardium (1157±74 vs 859±36 & 835±28 ms; both p<0.0001) with intermediate T1 values (1007±31 ms) in peri-infarct regions.

Compared with LGE, MEMRI was more sensitive in detecting dysfunctional myocardium (dysfunctional fraction 40.5±11.9 vs 34.9%±13.9%; p=0.02) & tracked more closely with abnormal wall motion (r2=0.72 vs 0.55; p<0.0001).

Kinetic modelling showed reduced myocardial manganese influx between remote, peri-infarct & infarct regions, enabling absolute discrimination of infarcted myocardium.

After 3 months, manganese uptake increased in peri-infarct regions (16.5±3.5 vs 22.8±3.5 mL/100 g/min, p<0.0001), but not the remote (23.3±2.8 vs 23.0±3.2 mL/100 g/min, p=0.8) or infarcted (11.5±3.7 vs 14.0±1.2 mL/100 g/min, p>0.1) myocardium.

Conclusions: Through visualisation of intracellular calcium handling, MEMRI accurately differentiates infarcted, stunned & viable myocardium, & correlates with myocardial dysfunction better than LGE.

MEMRI holds major promise in directly assessing myocardial viability, function & calcium handling across a range of cardiac diseases.

Keywords

• Acute myocardial infarction
• Late gadolinium enhancement (LGE)
• Manganese-enhanced MRI (MEMRI)