Middle-aged male long-distance runners with exercise-induced hypertension have increased left atrial diameter and elevated E/E′ ratio, which are markers associated with a higher risk of atrial fibrillation, indicating an elevated risk for future arrhythmias despite normal systolic function.

During intense exercise, abnormally high blood pressure forces the heart's main pumping chamber to work harder, causing its walls to thicken and stiffen. This stiffness makes it harder for the chamber to relax and fill properly, increasing pressure in the upper chamber of the heart. The increased pressure stretches the upper chamber over time, making it larger and more prone to irregular rhythms.