The relationship between cardiac autonomic tone and T-wave morphology during ambulatory monitoring

Intermittent T-wave inversions are known to occur during ambulatory monitoring in the absence of myocardial ischemia. The purpose of this study was to determine if T-wave inversions are associated with alterations in cardiac autonomic nervous system tone by examining the power spectrum of heart rate variability (HRV) during ambulatory monitoring. Twenty-eight episodes of T-wave inversions were analyzed from 17 youthful patients (8 men, 9 women; mean age 33.7 ± 7.3 years) who had no clinical evidence of coronary disease. Mean heart rate and total HRV (standard deviation of mean heart rate) increased during T-wave inversion from 83 ± 13 to 90 ± 13 bpm, p < 0.05, and from 56.6 ± 29.6 to 73.6 ± 36.8 ms, p < 0.015, respectively. The power spectrum of the HRV showed an increase in the low frequency components (9.28 ± 6.70 bpm² before vs. 16.45 ± 11.63 bpm² during T-wave inversion; p < 0.05). In contrast, the high frequency components did not change significantly during T-wave inversion (3.46 ± 3.52 bpm² before vs. 3.53 ± 4.30 bpm² during T-wave inversion). Three patients experienced dizziness, dyspnea or palpitations during T-wave inversion. In conclusion, T-wave inversions, recorded during ambulatory monitoring in patients with a low probability of coronary disease, are associated with an increase in the HRV which is predominantly due to augmentation of the low frequency components without significant change in the high frequency components of the power spectrum. These data suggest that augmentation in cardiac sympathetic tone may influence T-wave morphology in the absence of myocardial ischemia.