Donuts are not usually very high on the list when talking about healthy hearts, but it turns out that they might be critical to proper coronary blood flow – at least in terms of their shape. Researchers from Johns Hopkins Medicine have recently found that the pattern blood takes while flowing through the heart's upper chamber can be a key indicator of blood clot formation and subsequent stroke risk.

In their study, the researchers conducted CT scans of two hearts: one healthy and one that was enlarged due to heart disease. They then fed the information they gleaned into a series of computer visualizations and created videos of the blood's fluid motion in the heart's left atrium where it enters from the pulmonary veins and passes into the lower-left chamber known as the ventricle.

They discovered that in the healthy heart, blood forms "eddies" that are shaped like corkscrews and resolve into vortices shaped like doughnuts. In the diseased heart, however, the blood failed to shape up into these formations and instead was falling in sheet-like patterns by the time it reached the bottom of the atrium. This can cause the blood to pool and form clots which can cause strokes if they travel to the brain.

"As the blood comes in contact with the atrium's surface, it slows down due to shearing forces similar to friction, and this appears to prevent the blood from exiting the chamber as smoothly as it might," says Hiroshi Ashikaga, M.D., Ph.D., assistant professor of medicine and member of the Heart and Vascular Institute at the Johns Hopkins University School of Medicine and one of the study authors. "The slower the blood moves and the more contact it has with the atrium, the more risk there is for a clot to form."

The researchers believe this discovery can help them better assess stroke risk and they are now conducting a long-term study with more participants to add to their body of knowledge.

"By looking at blood flow through the atrium, we think we can accurately assess stroke risk better than such risk factors as heart size and pumping strength," says Ashikaga. "Our study fills in a missing diagnostic link between heart function and fluid motion in our understanding of how each can affect stroke risk."

You can see simulations of blood flow through a healthy heart here and through a diseased heart here.

The research has been published in the journal Annals of Biomedical Engineering.