Comparison of visual scoring and quantitative planimetry methods for estimation of global infarct size on delayed enhanced cardiac MRI and validation with myocardial enzymes

Purpose: Although delayed enhanced CMR has become a reference method for infarct size quantification, there is no ideal method to quantify total infarct size in a routine clinical practice. In a prospective study we compared the performance and post-processing time of a global visual scoring method to standard quantitative planimetry and we compared both methods to the peak values of myocardial biomarkers.

Materials and methods: This study had local ethics committee approval; all patients gave written informed consent. One hundred and three patients admitted with reperfused AMI to our intensive care unit had a complete CMR study with gadolinium-contrast injection 4±2 days after admission. A global visual score was defined on a 17-segment model and compared with the quantitative planimetric evaluation of hyperenhancement. The peak values of serum Troponin I (TnI) and creatine kinase (CK) release were measured in each patient.

Results: The mean percentage of total left ventricular myocardium with hyperenhancement determined by the quantitative planimetry method was (20.1±14.6) with a range of 1-68%. There was an excellent correlation between quantitative planimetry and visual global scoring for the hyperenhancement extent's measurement (r=0.94; y=1.093x+0.87; SEE=1.2; P<0.001) The Bland-Altman plot showed a good concordance between the two approaches (mean of the differences=1.9% with a standard deviation of 4.7). Mean post-processing time for quantitative planimetry was significantly longer than visual scoring post-processing time (23.7±5.7min vs 5.0±1.1min respectively, P<0.001). Correlation between peak CK and quantitative planimetry was r=0.82 (P<0.001) and r=0.83 (P<0.001) with visual global scoring. Correlation between peak Troponin I and quantitative planimetry was r=0.86 (P<0.001) and r=0.85 (P<0.001) with visual global scoring.

Conclusion: A visual approach based on a 17-segment model allows a rapid and accurate assessment of the myocardial global delayed enhancement. This scoring method could be used on a daily practice and useful for the management strategy of post-MI patients.