The effect of sleep apnea on QT interval, QT dispersion, and arrhythmias.

BACKGROUND: QT interval (QT) and QT dispersion (QTd) are electrocardiograph (ECG) parameters for the evaluation of myocardial repolarization. The inhomogeneity of ventricular repolarization is associated with ventricular arrhythmias. An increased QT, QTd, and increased incidence of nocturnal cardiac rhythm disturbances have been described in patients with obstructive sleep apnea (OSA), while other investigators did not find a relationship between ventricular arrhythmias and OSA. HYPOTHESIS: The aim of this study was to examine the occurrence of ventricular arrhythmias and to measure QT parameters in patients with untreated OSA using an ambulatory Holter-ECG. METHODS: A total of 25 patients with untreated OSA were studied. After routine biochemical investigation and 2-dimensional, M-mode echocardiography, a 24-hour Holter-ECG was recorded to detect cardiac arrhythmias and QT parameters. QT parameters were measured by the QT Guard system. RESULTS: Only the QT interval increased significantly during the nighttime period (nocturnal QT interval: 423.1 +/- 34.6 ms, daytime QT interval: 381.6 +/- 33.8 ms, 24-hour QT interval: 394.7 +/- 31.1 ms). However, during the nighttime QT interval (422.8 +/- 14.9 ms), QTd (31.2 +/- 11.0 ms) and QT dispersion (30.5 +/- 10.2 ms) did not show any change compared to 24-hour (QTc interval: 423.7 +/- 14.2 ms, QTd: 28.8 +/- 9.4 ms, QTcd: 30.5 +/- 9.43 ms) and daytime levels (QTc interval: 423.9 +/- 14.3 ms, QTd: 27.3 +/- 10.7 ms, QTcd: 29.9 +/- 11.1 ms). None of the patients had ventricular arrhythmias. CONCLUSIONS: QTd and QTcd did not increase during the nighttime period. Our study did not show an increased risk of ventricular arrhythmias in this population during the monitoring period.

[Arrhythmias in patients with obstructive sleep apnea]. / Szívritmuszavarok obstruktív alvási apnoéban.

The authors summarize the current knowledge on the types, prevalence, reasons, diagnosis and current therapy of arrhythmias occurring in patients with obstructive sleep apnea. Most of the patients with obstructive sleep apnea have nocturnal bradycardia (5-50%), paroxysmal tachyarrhythmia (atrial 35%; ventricular 0-15%), or both. The frequency of rhythm disturbances associated with the severity of the sleeping disorder. It is important to recognize the factors predisposing to arrhythmias and the early appropriate therapy of patients is essential, in order to protect patients from life threatening arrhythmias which may worsen the clinical outcome.

[Effect of flumazenil on the regional cerebral blood flow measured by [15O]-butanol PET scan and transcranial Doppler ultrasonography]. / Flumazenil hatása a regionális agyi perfusióra [15O]-butanol-PET- és transcranialis Doppler-UH-vizsgálatok alapján.

The authors investigated the role of the cBZD/GABA-A receptor-complex in the regulation of rCBF by simultaneously applying [15O]-butanol-PET and TCD in therapy-resistant TLE patients. It is known that the density of the cBZD/GABA-A-receptors is reduced in the epileptogenic area of the temporal lobe, but there are no data available about the impact of this phenomenon on rCBF. FMZ is a well-known BZD-receptor antagonist which can be used to inhibit the effect mediated by cBZD/GABA-A-receptors, offering a way to study the contribution of these receptors in the determination of rCBF. The authors examined the possible correlation between the rCBF values obtained by PET and the blood flow speed readings measured by TCD in MCAs. The results show that FMZ does not cause any change in rCBF on the side of the epileptogenic focus but it significantly raises rCBF (p < 0.001) in the intact brain tissue on the other side. The TCD measurements showed no significant differences between the blood flow in the MCAs supplying the affected and the contralateral lobe.