Quantifying Cumulative Diastolic Deprivation: A Physiological Model Linking Lifetime Endurance Training to Atrial Fibrillation Risk

Background: Long-term endurance training is associated with an elevated risk of atrial fibrillation, but the underlying mechanisms remain fragmented. We quantified cumulative diastolic deprivation, defined as the lifetime reduction in diastolic perfusion time produced by training at elevated heart rates. Methods: We built a physiological model from published cardiac time intervals. Total electromechanical systole was estimated with the Weissler equation, validated against Copenhagen City Heart Study data. A second model incorporated a 58-ms correction for QRS-to-mitral-valve-closure delay. A third model used published diastolic time fractions. Training volume and intensity distribution followed standard endurance training patterns, with primary and conservative scenarios. Results: Resting diastolic time per beat was 538 ms at 63 bpm, falling to 169 ms at 150 bpm. Over a 20-year career, the main, corrected, and empirical models estimated cumulative diastolic time losses of 1,536, 985, and 1,867 hours, respectively. A conservative training scenario yielded 922, 591, and 1,067 hours. Across models, the 20-year loss was approximately 1,000-1,900 hours, equivalent to 40-80 days. Published studies were directionally consistent: lifetime training load associated with atrial fibrillation, sport type influenced remodeling, and autonomic factors dominated over fibrosis. Conclusion: Endurance training produces a large and quantifiable reduction in lifetime diastolic perfusion time, providing a unifying physiological basis for the dose-response relationship between endurance exercise and atrial fibrillation.