Plasma potassium concentration and cardiac repolarisation markers, Tpeak-Tend and Tpeak-Tend/QT, during and after exercise in healthy participants and in end-stage renal disease

Purpose The cardiac T-wave peak-to-end interval (T-pe) is thought to reflect dispersion in ventricular repolarisation, with abnormalities in T-pe associated with increased risk of arrhythmia. Extracellular K+ modulates cardiac repolarisation, and since arterial plasma K+ concentration ([K+]) rapidly increases during and declines following exercise, we investigated the relationship between [K+] and T-pe with exercise. Methods Serial ECGs (T-pe, T-pe/QT ratio) and [K+] were obtained from 8 healthy, normokalaemic volunteers and 22 patients with end-stage renal disease (ESRD), at rest, during, and after exhaustive exercise. Results Post-exercise [K+] nadir was 3.1 +/- 0.1, 5.0 +/- 0.2 and 4.0 +/- 0.1 mmol.L-1 (mean +/- SEM) for healthy participants and ESRD patients before and after haemodialysis, respectively. In healthy participants, compared to pre-exercise, recovery-induced low [K+] was associated with a prolongation of T-pe (110 +/- 8 vs. 87 +/- 5 ms, respectively, p = 0.03) and an increase in T-pe/QT ratio (0.28 +/- 0.01 vs. 0.23 +/- 0.01, respectively, p = 0.01). Analyses of serial data revealed [K+] as a predictor of T-pe in healthy participants (beta = -0.54 +/- 0.05, p < 0.0001), in ESRD patients (beta = -0.75 +/- 0.06, p < 0.0001) and for all data pooled (beta = -0.61 +/- 0.04, p < 0.0001). The [K+] was also a predictor of T-pe/QT ratio in healthy participants and ESRD patients. Conclusions T-pe and T-pe/QT ratio are predicted by [K+] during exercise. Low [K+] during recovery from exercise was associated with increased T-pe and T-pe/QT, indicating accentuated dispersion of ventricular repolarisation. The findings suggest that variations in [K+] with physical exertion may unmask electrophysiological vulnerabilities to arrhythmia.