Introduction: An aneurysm is an acquired, abnormal dilation of a blood vessel. Computational fluid dynamics (CFD) have been used to try and understand this phenomena. CFD studies use assumptions in the simulation model and pick variables to look at. A variable that seldom gets much attention in these studies is the heart rate. We have investigated the differences between high and low heart rate.Method: We used twelve different patient specific aneurysms. Three simulations were done per aneurysm. 1) Newtonian fluid with high heart rate, 2) Newtonian fluid with low heart rate and 3) non-Newtonian fluid with low heart rate.We compared the average wall shear stress (WSS) magnitude and direction between high and low heart rate. We also used the proper orthogonal decomposition (POD) to differentiate the flow pattern and complexity of the flow.We also looked at Pearson correlation on the average WSS magnitude.To set the changes in perspective we compared the changes to changes in non-Newtonian flow. Results: We found that the POD error was greater for high heart rate. The changes in complexity did not result in large differences in the average WSS for the most of the aneurysms. In one aneurysm we found considerable differences in the direction of the average WSS.This we did not find in the non-Newtonian case.The Pearson correlation were high for both high/low heart rate and Newtonian/non-Newtonian modeling for blood.Conclusion: The WSS changes between the heart rates were small and of same order as changes is WSS between Newtonian and non-Newtonian flow. Since non-Newtonian effects have been found to be negligible compared to other variables we conclude that varying heart rate is not important to consider in further studies.