Strokes kill someone every 4 minutes. To determine your risk, doctors measure certain characteristics of your heart, such as its size and pumping strength. However, researchers haven’t had the tools to study how disease-induced structural changes in the heart might be affecting heart function and blood flow. Now, an interdisciplinary team of scientists says it has found a new way to analyze blood flow through one of the heart’s upper blood collection chambers—the left atrium—which could lead to a better way to assess stroke risk in patients. The researchers used specialized computerized tomography scans to build visualizations of cardiac blood flow in two hearts: one with healthy blood flow (above) and another with abnormal blood flow because of heart disease. Their modeling shows that in the healthy heart, blood flows through the left atrium in a tight corkscrew shape, which allows blood to quickly exit that structure. However, in the enlarged, diseased heart, this corkscrew shape never fully forms, which causes blood to linger in the left atrium. As a result, the blood is more likely to pool there, forming a stroke-causing clot, the team reports this month in the Annals of Biomedical Engineering. The scientists hope that future work will enable them to equip medical practitioners with the ability to use computerized, personal cardiac blood flow visualizations to assess stroke risk in their patients.