The Wistar rat is a commonly used strain for experimental animal models. Recently it was shown that results vary between studies using Wistar rats of different suppliers. Therefore we studied whether Wistar rats obtained from Harlan Laboratories (Ha, n=24) and Charles River (CR, n=22) had a different outcome in an acute myocardial infarction (AMI) model. AMI was induced in both Ha and CR Wistar rats by one operator. This resulted in a significantly higher survival rate for Ha (79.2±10.2%) compared with CR rats (54.2±10.2%, p<0.05). Furthermore, CR rats had lost significantly more weight after 7 days (-5.9±3.1%) compared with Ha rats (-0.8±1.7%; p<0.001), indicating a worse health status of the CR rats. Paradoxically, the induced infarct was smaller in CR rats (7.3±3.6% of the heart) compared with Ha rats (12.1±4.7%, p<0.05). This indicates that CR rats were less sensitive for the cardiomyocyte damage subsequent to AMI induction, but remarkably showed more clinical side effects indicating that Wistar rats from two suppliers had a different response within the same AMI model.