The transmural extent of late gadolinium enhancement detected with cardiovascular magnetic resonance in collateral dependent myocardium. Does a good collateral supply predict myocardial viability?

Ripley DP1,2, Gosling OE1,2, Bhatia L3, Peebles CR3, Shore A2, Curzen NP3, Bellenger NG1,2

1 Royal Devon & Exeter NHS Foundation Trust, Exeter 2 University of Exeter Medical School, Exeter, 3University Hospital Southampton NHS Trust

INTRODUCTIONDysfunctional myocardium which has the potential for contractile recovery after revascularisation is deemed viable tissue. A collateral circulation can be assessed visually at invasive coronary angiography using the Cohen and Rentrop grade. The prognostic and protective role of such collateralisation has been described and the multi-centre TOAST-GISE trial revealed revascularisation of chronic total occlusion provides a survival benefit. There is however debate in the literature as to whether collateralisation can predict myocardial viability after vessel occlusion.

Myocardial viability can be assessed with late gadolinium enhancement (LGE) imaging by cardiac magnetic resonance (CMR) scanning. We aimed to assess the collateral grade of patients with an occluded coronary artery at invasive coronary angiography with the degree of myocardial viability as assessed with CMR scanning.

DPR and OEG were granted fellowships by the Gawthorn Cardiac Charitable Trust

RESULTSOf the 71 patients with an occluded artery, 13 had poor or no-flow, 22 had moderate collaterals and 36 good collaterals.

CMR detected a median LGE score of 1 (0% mural thickness) in 35 patients (49%). 6 (8%) had a median LGE score of 2 (1-25% mural thickness); 9 (13%) median LGE score of 3 (26-50% mural thickness); 8 (11%) median LGE score of 4 (51-75% mural thickness) and 13 (18%) median LGE score of 5 (75%+ mural thickness). Therefore 50 coronary territories (70%) were deemed to be viable (ie≤3) and the remaining 21 (30%) non-viable.

Increasing LGE score was significantly associated with higher mean WMSI representing increasing dysfunctional myocardium (p<0.001). A good collateral circulation with high Rentrop score was more likely to have viable myocardium in the territory supplied; conversely a poor Rentrop score was associated with a higher risk of having non-viable myocardium (p=0.01) (Table 1).

CONCLUSIONS Myocardium subtended by an occluded artery in the presence of good coronary collateralisation has an increased chance of viability as documented by CMR LGE imaging. This association may explain the mechanism of improved survival in CAD patients with well-developed collaterals.

METHODS71 patients from two centres were retrospectively identified as having both invasive coronary angiography and a late gadolinium enhancement (LGE) CMR study performed. The degree of LGE was assessed with each myocardial segment scored as 1 (0% of mural thickness), 2 (1-25%), 3 (26-50%), 4 (51-75%) and 5 (76-100%); a median score of ≤3 was considered viable. Myocardial segments were also scored for wall motion with each segment scored as 1 (normal / hyperkinetic), 2 (hypokinetic), 3 (akinetic), or 4 (dyskinetic) and wall motion score index (WMSI) calculated. The collateral circulation was graded with the Cohen and Rentrop classification and classified as poor or no flow (grades 0-1), moderate flow (grade 2) or good flow (grade 3) to the occluded vessel. The scoring of the LGE and collateral flow was performed blinded to the result of the other test.

Median LGE score for each vascular territory was compared with the Rentrop score and WMSI.

Poor/No Flow

(n=13)

Moderate Flow

(n=22)

Good Flow

(n=36)

Viable, n(%)

5 (38%)

15 (68%)

30 (83%)

Table 1 - The presence of collateral circulation and its relationship with myocardial viability determined by the transmural thickness of the late gadolinium enhancement on cardiovascular MRI (p=0.01)