Experimental validation of contrast-enhanced SSFP cine CMR for quantification of myocardium at risk in acute myocardial infarction

Background: Accurate assessment of myocardium at risk (MaR) after acute myocardial infarction (AMI) is necessary when assessing myocardial salvage. Contrast-enhanced steady-state free precession (CE-SSFP) is a recently developed cardiovascular magnetic resonance (CMR) method for assessment of MaR up to 1 week after AMI. Our aim was to validate CE-SSFP for determination of MaR in an experimental porcine model using myocardial perfusion single-photon emission computed tomography (MPS) as a reference standard and to test the stability of MaR-quantification over time after injecting gadolinium-based contrast. Methods: Eleven pigs were subjected to either 35 or 40 min occlusion of the left anterior descending artery followed by six hours of reperfusion. A technetium-based perfusion tracer was administered intravenously ten minutes before reperfusion. In-vivo and ex-vivo CE-SSFP CMR was performed followed by ex-vivo MPS imaging. MaR was expressed as % of left ventricular mass (LVM). Results: There was good agreement between MaR by ex-vivo CMR and MaR by MPS (bias: 1 ± 3% LVM, r ² = 0.92, p < 0.001), between ex-vivo and in-vivo CMR (bias 0 ± 2% LVM, r ² = 0.94, p < 0.001) and between in-vivo CMR and MPS (bias -2 ± 3% LVM, r ² = 0.87, p < 0.001. No change in MaR was seen over the first 30 min after contrast injection (p = 0.95). Conclusions: Contrast-enhanced SSFP cine CMR can be used to measure MaR, both in vivo and ex vivo, in a porcine model with good accuracy and precision over the first 30 min after contrast injection. This offers the option to use the less complex ex-vivo imaging when determining myocardial salvage in experimental studies.