Individual exercise training response and ECG morphology in patients after an acute coronary syndrome

Patients after an acute coronary syndrome (ACS) with preserved left ventricle ejection fraction (LVEF) (n = 45, 10 female) were guided by exercise training for 6 months after percutaneous coronary intervention. Exercise capacity, LVEF, standard resting ECG, and 24-h Holter recording were measured at baseline. Time and frequency domain heart rate variability were analyzed over 24 h. Sokolow-Lyon index, as a marker of left ventricular hypertrophy and P wave Terminal Force in lead V₁ (PTF), a marker of left atrial dilatation, along with the standard parameters were analyzed from ECG. A training load of over 6 months (TRIMP) was calculated. Subjects were categorized according to training responses in exercise capacity as low (-3 ± 4%), average (6 ± 2%), and high (15 ± 6%) responders. PTF and P wave duration at baseline differed between the groups: 0.051 ± 0.018, 0.028 ± 0.023, and 0.016 ± 0.015 ms (p < 0.0001) and 120 ± 11, 113 ± 12 and 104 ± 13 ms (p = 0.002) for low, average, and high groups, respectively. Other ECG variables, or any clinical parameters (e.g., sex, age, baseline fitness, LVEF) at baseline or TRIMP were not associated with the training response. Left atrial dilatation, as indicated by PTF on surface ECG, is associated with a low training response in exercise capacity in patients after ACS.