| Summary: | <p><strong>Background:</strong> Pseudonormal T waves may be detected on stress electrocardiograms (ECGs) in hypertrophic cardiomyopathy (HCM). Either myocardial ischaemia or purely exercise-induced changes have been hypothesised to contribute to this phenomenon, but the precise electrophysiological mechanisms remain unknown.</p>
<p><strong>Methods:</strong> Computational models of human HCM ventricles (n = 20) with apical and asymmetric septal hypertrophy phenotypes with variable severities of repolarisation impairment were used to investigate the effects of acute myocardial ischaemia on ECGs with T wave inversions at baseline. Virtual 12-lead ECGs were derived from a total of 520 biventricular simulations, for cases with regionally ischaemic K<sup>+</sup> accumulation in hypertrophied segments, global exercise-induced serum K<sup>+</sup> increases, and/or increased pacing frequency, to analyse effects on ECG biomarkers including ST segments, T wave amplitudes, and QT intervals.</p>
<p><strong>Results:</strong> Regional ischaemic K<sup>+</sup> accumulation had a greater impact on T wave pseudonormalisation than exercise-induced serum K<sup>+</sup> increases, due to larger reductions in repolarisation gradients. Increases in serum K<sup>+</sup> and pacing rate partially corrected T waves in some anatomical and electrophysiological phenotypes. T wave morphology was more sensitive than ST segment elevation to regional K<sup>+</sup> increases, suggesting that T wave pseudonormalisation may sometimes be an early, or the only, ECG feature of myocardial ischaemia in HCM.</p>
<p><strong>Conclusions:</strong> Ischaemia-induced T wave pseudonormalisation can occur on stress ECG testing in HCM before significant ST segment changes. Some anatomical and electrophysiological phenotypes may enable T wave pseudonormalisation due to exercise-induced increased serum K<sup>+</sup> and pacing rate. Consideration of dynamic T wave abnormalities could improve the detection of myocardial ischaemia in HCM.</p>
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