Peristalsis represents one way that animals can drive circulatory flow. Tubular hearts that drive flow peristaltically are present in many invertebrate circulatory systems, as well as early embryonic vertebrates. Although peristalsis is a well-studied system in many contexts, very few studies have examined the performance of peristaltic systems with different resistive circulatory systems. In this study, we examine the performance of peristaltic hearts with circulatory systems of various resistance through a computational fluid dynamics modeling. Two peristaltic mechanisms were used, opposing sine waves and opposing sharp Gaussian peaks, which allowed for investigating the role of heart tube flexibility. We found that increasing circulatory resistivity decrease flow rates and greatly increased the cost of transport. Additionally, flexibility of the heart tube allowed for greater flow speeds within the circulatory system and more consistent flows in additional resistivity. This provides potential insight into the action and physical limits of peristaltic pumps in terms of driving flow in resistive circulatory systems.