Pacing and clinical electrophysiology : PACE
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Pacing Clin Electrophysiol · Apr 2005
Rate-dependent AV delay optimization in cardiac resynchronization therapy.
During cardiac resynchronization therapy (CRT), cardiac performance is dependent on an optimized atrioventricular delay (AVD). However, the optimal AVD at different heart rates has not been defined yet during CRT. ⋯ In conclusion, the systolic performance of the dilated ventricle, which depends on an elevated preload, is critically affected by the appropriate timing of the AVD during exercise. In contrast to normal pacemaker patients, in CRT the relatively short baseline AVD should be prolonged at increased heart rates. Further studies with other means of measuring exercise cardiac performance are needed to confirm these unexpected findings.
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Pacing Clin Electrophysiol · Feb 2005
Electrophysiological characteristics of junctional rhythm during ablation of the slow pathway in different types of atrioventricular nodal reentrant tachycardia.
Junctional rhythm (JR) is commonly observed during radiofrequency (RF) ablation of the slow pathway for atrioventricular (AV) nodal reentrant tachycardia. However, the atrial activation pattern and conduction time from the His-bundle region to the atria recorded during JR in different types of AV nodal reentrant tachycardia have not been fully defined. ⋯ In patients with slow-fast and slow-intermediate AV nodal reentrant tachycardia, the JR during ablation of the slow pathway conducted to the atria through the fast or intermediate pathway. In patients with fast-slow AV nodal reentrant tachycardia, there was no retrograde conduction during JR. These findings suggested there were different characteristics of the JR during slow-pathway ablation of different types of AV nodal reentrant tachycardia.
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Pacing Clin Electrophysiol · Dec 2004
Sample size, power calculations, and their implications for the cost of thorough studies of drug induced QT interval prolongation.
Regulatory authorities require new drugs to be investigated using a so-called "thorough QT/QTc study" to identify compounds with a potential of influencing cardiac repolarization in man. Presently drafted regulatory consensus requires these studies to be powered for the statistical detection of QTc interval changes as small as 5 ms. Since this translates into a noticeable drug development burden, strategies need to be identified allowing the size and thus the cost of thorough QT/QTc studies to be minimized. ⋯ In the data of this study, the average of standard deviations of QTc values calculated separately in each individual was only 5.2 ms. Such a variability in QTc data translates to only 18 subjects per study group (e.g., the size of a complete one-group crossover study) to detect 5 ms QTc change with an 80% power. Cost calculations show that by involving the most stringent ECG handling and measurement, the cost of a thorough QT/QTc study may be reduced to approximately 25%-30% of the cost imposed by the simple ECG reading (e.g., three complexes in one lead only).
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Pacing Clin Electrophysiol · Dec 2004
Randomized Controlled Trial Multicenter Study Clinical TrialShort-term efficacy of a telephone intervention by expert nurses after an implantable cardioverter defibrillator.
The ICD is a common therapy for treatment of ventricular arrhythmias and prevention of sudden cardiac death. After ICD therapy, 50% of survivors are known to have significantly elevated anxiety, depression, anger, and fear in getting back to normal physical activities. Despite these problems, few interventions to improve adjustment have been rigorously evaluated within a clinical trial format. ⋯ The intervention group, as compared to the control group, significantly reduced mean PCA symptoms at 1 month (11.3-8.8 vs 9.7-9.3, respectively, P < 0.02), and reduced state anxiety (36.1-31.9 vs 33.1-33.0, respectively, P < 0.08), and enhanced knowledge (21.8-22.4 vs 21.4-21.7, respectively, P < 0.02) at 3 months. The intervention did not significantly impact short-term health care use. A structured telephone intervention delivered during the first 8 weeks after ICD therapy by expert cardiovascular nurses decreased ICD related physical symptoms and anxiety, and increased SCA knowledge over 3 months.