Comparison of SSFP and IR GRE techniques for measurement of total myocardial mass-influence of applied contrast dosage and implication for relative infarct size assessment.
OBJECTIVE
To compare total left ventricular mass assessment using steady state free precession (SSFP) and inversion recovery fast gradient echo (IR GRE) imaging and further to assess the influence of contrast dosage on mass by IR GRE and its implications on relative infarct size assessment with both methods.


METHODS
Forty-three patients with first documented myocardial infarction and single vessel disease underwent measurement of total myocardial mass using SSFP technique and an IR GRE sequence. As part of a Phase 2 multi-center dose ranging study for infarct identification patients received 1 of 4 possible dosages (0.05, 0.1, 0.2 or 0.3 mmol/kg body weight) of the contrast agent gadoversetamide (OptiMARK, Tyco Healthcare Mallinckrodt, St. Louis, MO, USA).


RESULTS
Left ventricular mass assessment using IR GRE resulted in a slightly greater detection of myocardial mass than from the SSFP images (160.1 and 156.4 g, respectively, p < 0.001). The overall good correlation of both methods (R2 = 0.97 for the total study group, p < 0.001) was further improved by using gadoversetamide at doses of 0.2 or 0.3 mmol/kg (R2= 0.99, p < 0.001), mainly as a result of a considerably higher blood-myocardial contrast-to-noise ratio (CNR) in the IR GRE images. Bland-Altman analysis in these subgroups showed very little scatter of the residuals over the mean (3.5 +/- 5.4 g and 1.3 +/- 6.9 g respectively, 95% confidence interval). The observed differences in total mass calculation, while statistically significant, were not correlated with clinically relevant differences in estimation of relative infarct size.


CONCLUSION
Total LV mass calculations using SSFP and IR GRE techniques are interchangeable when using appropriate contrast media, such as gadoversetamide. Late gadolinium enhancement results in good blood myocardial CNR. Hence, for relative infarct size assessment either method for calculation of total myocardial mass can be used.