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[Post-extrasystolic long QT: evaluation and significance]
M Haissaguerre1, P Lemetayer, P Montserrat
1Service de Cardiologie, Hôpital Saint-André, Bordeaux.
Annales De Cardiologie Et D'Angeiologie
|January 1, 1991
Summary
Patients with abnormal post-extrasystolic T waves show poor QT interval adaptation to autonomic stress. Hydroquinidine, a common heart medication, significantly prolonged the corrected QT (QTc) interval in nearly half of these patients.
Area of Science:
- Cardiology
- Electrophysiology
- Pharmacology
Context:
- The QT interval reflects ventricular repolarization, crucial for cardiac rhythm.
- Post-extrasystolic pauses can unmask repolarization abnormalities.
- Autonomic nervous system influences cardiac repolarization dynamics.
Purpose:
- To investigate the dynamic behavior of the QT interval in patients with post-extrasystolic T-wave abnormalities.
- To assess QT interval response to autonomic stimulation (exercise, Valsalva) and hydroquinidine therapy.
Summary:
- 13 patients with prolonged QT intervals post-extrasystole were studied.
- Basal corrected QT (QTc) was normal, but significantly prolonged after pauses (512 ms).
- Exercise and Valsalva maneuvers prolonged QTc (>460 ms) in 11/13 patients.
- Hydroquinidine (mean 729 mg) induced QTc >500 ms in 6/13 patients (46%).
Impact:
- Identifies impaired QT interval adaptation to autonomic stress in this patient group.
- Highlights potential proarrhythmic risk with hydroquinidine in susceptible individuals.
- Suggests careful consideration of hydroquinidine dosage and monitoring in patients with repolarization abnormalities.