Inclination of the pulmonary veins when reaching the heart and risk of blood clots

The shape of the heart chambers or the inclination with which the pulmonary veins reach it are not always the same, but vary according to the anatomical characteristics of each person.

Recently, pioneering research by the Pompeu Fabra University (UPF) in Barcelona and the Inria Epione research institute (linked to the University of the Côte d’Azur in France) has analyzed how these morphological characteristics determine the risk of suffering blood clots in the heart among patients suffering from atrial fibrillation. This is the most common type of arrhythmia and one of the main causes of thrombi.

The study has determined that the risk of suffering blood clots in this group of patients is influenced by the shape of the heart chambers and, especially, by the inclination with which the pulmonary veins reach the appendage of the left atrium, a small irregularly shaped cavity found in that part of the heart.

The relationship between the morphological characteristics of the heart and pulmonary veins and blood circulation patterns had been poorly investigated until now and with a very small number of patients. In fact, the sample of this research, with 130 patients, is the largest that has been used so far in studies of this type. The main researchers of the study are Oscar Cámara, head of the PhySense (Sensing in Physiology and Biomedicine) research group at the UPF Department of Engineering, and Maxime Sermesant, director of computational cardiology at the Inria Epione center.

Blood thrombi, the object of study in this research, are the result of blood stagnation in the appendage of the left atrium, which can cause serious health damage such as a stroke or even death. Thrombi can be triggered by multiple factors and, in fact, one of their main risk factors currently is atrial fibrillation, which alters the normal rhythm with which the heart should pump blood. However, it is not known why there are certain patients who suffer from atrial fibrillation and do not develop thrombi and others who do.

This research shows that the orientation of the pulmonary veins could be key to explaining the speed of blood and why it stagnates or not in the appendage of the left atrium.

Among the 130 people in the sample, there was a group that had developed blood clots and another that had never suffered them. The objective was to determine, with the support of personalized computer simulations, if there were morphological differences of the heart and pulmonary veins between the first and second groups, as well as variations in their blood circulation patterns. For this reason, several parameters have been measured for each patient related to the anatomical characteristics of the left atrium and its appendix; the inclination, configuration and number of pulmonary veins (the number is also not homogeneous between individuals); blood circulation patterns; blood flow tracking particles, etc.

As a result of this analysis, the research team has come to the conclusion that the angle of inclination with which the pulmonary veins are oriented towards the left atrial appendage is of primary importance in the flow of blood circulation and, therefore, in the risk of thrombus formation. Between the two groups of patients (with thrombi and without thrombi) differences have been detected, especially with regard to the alignment of the left superior pulmonary vein and the right pulmonary vein.

Morphological descriptors of the left atrium and its appendage in the heart: curvature (above) and gyrification index (below). (Images: Jordi Mill, Josquin Harrison, Marta Saiz-Vivo, Carlos Albors, Xabier Morales, Andy L. Olivares, Xavier Iriart, Hubert Cochet, Jerome Noailly, Maxime Sermesant, Oscar Camara)

Jordi Mill, co-author of the study and researcher in the PhySense group at UPF, concludes: “The results of the research open the door to better stratification of patients at risk of suffering stroke among people who have atrial fibrillation, as well as treatments. “more precise to prevent and treat cardiac thrombosis in the left atrium.”

The study is titled “The role of the pulmonary veins on left atrial flow patterns and thrombus formation.” And it has been published in the academic journal Scientific Reports. (Source: Pompeu Fabra University)