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Variability of negative T wave in hypertrophic cardiomyopathy: possible role of beta-adrenergic function
Insights
Negative T waves in hypertrophic cardiomyopathy (HCM) are variable and influenced by adrenergic function. Exercise and beta-adrenergic agonists can reverse these ECG changes, suggesting a key role for beta-adrenergic mechanisms.
Area of Science:
- Cardiology
- Electrophysiology
- Internal Medicine
Background:
- Hypertrophic cardiomyopathy (HCM) is associated with ECG abnormalities, including negative T waves.
- Giant negative T waves, particularly in apical hypertrophy, represent a significant clinical finding in HCM.
- The underlying mechanisms of these T wave changes, especially their variability, remain incompletely understood.
Purpose of the Study:
- To investigate the variability and mechanisms of negative T waves in hypertrophic cardiomyopathy (HCM).
- To explore the role of adrenergic function in the genesis of negative T waves in HCM, focusing on apical hypertrophy.
- To assess the impact of exercise and beta-adrenergic modulation on T wave inversions in HCM patients.
Main Methods:
- Electrocardiogram (ECG) analysis in 33 HCM patients with negative T waves.
- Treadmill exercise testing to evaluate ECG response during exertion.
- Administration of beta-adrenergic agonist (isoproterenol) and antagonist (propranolol) to assess adrenergic influence.
Main Results:
- Negative T waves became significantly less deep during treadmill exercise in all HCM patients (p < 0.001).
- Isoproterenol administration induced similar T wave reversal as exercise, though at lower physiological stress levels.
- Propranolol exacerbated negative T waves at rest and blunted the exercise-induced reversal, indicating a beta-adrenergic effect.
Conclusions:
- Negative T waves in HCM, especially giant ones in apical hypertrophy, exhibit significant variability.
- Beta-adrenergic function appears to be a key mechanism contributing to the development and modulation of negative T waves in HCM.
- These findings highlight the dynamic nature of ECG changes in HCM and their relationship with autonomic nervous system activity.
Abstract:
To investigate the variability and the mechanism of negative T waves in hypertrophic cardiomyopathy (HCM), especially giant negative T waves in apical hypertrophy, from view point of adrenergic function, ECG was studied by treadmill exercise test and under administrations of beta-adrenergic agonist (isoproterenol) and antagonist (propranolol) in 33 patients with HCM and negative T waves. Apical hypertrophy was seen in 16 cases, and giant negative T waves were seen in 24 cases. By treadmill exercise test, negative T waves became less deep in all cases of HCM (-1.2 +/- 0.5 mV-----0.6 +/- 0.5 mV, p less than 0.001). The higher exercise level the patients attained, the less deep the negative T waves became. Isoproterenol caused the same reversal of negative T waves as the exercise test, but heart rate and rate pressure product attained by isoproterenol were significantly smaller than those by exercise. R wave amplitude did not change with isoproterenol. Propranolol made negative T waves deeper at rest and inhibited the reversal of negative T waves caused by exercise. In conclusion, negative T wave in HCM, especially giant negative T wave in apical hypertrophy, is variable. Beta-adrenergic function may be at least one of its mechanisms.