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PubMed2004

Effect of exercise training in patients with an implantable cardioverter defibrillator.

AIMS: Little research exists on exercise performance and training in patients with an implemented cardioverter defibrillator (ICD) and only in a limited number of patients. This study aims to investigate the effect of exercise training in ICD patients in comparison to the effects in other cardiac patients without an ICD. METHODS AND RESULTS: 92 ICD patients were compared with a control group of 473 patients. A maximal cycle-spiroergometric test was performed until exhaustion before and after an ambulatory exercise training programme. Exercise training was offered 3 times a week for 3 months. The cut-off heart rate was set at (ICD detection rate -20 beats/min). At baseline, the ICD patients had a lower peak oxygen uptake (VO(2)) compared to the control group. Training effects were smaller for peak VO(2) (mL/min/kg) and oxygen pulse in the ICD group (18 vs. 27%, p = 0.006 and 11 vs. 17%, p = 0.016, respectively). Several appropriate shocks were delivered during (n = 5), and in between (n = 7), testing or training and one inappropriate shock during training. CONCLUSIONS: ICD patients can safely participate in an exercise training programme with favorable results. A randomised control study with evaluation of the physical and the psychosocial effects is warranted.

Defibrillators, Implantable↗
PubMed2004

Verification of implantable cardioverter defibrillator (ICD) interventions by nonlinear analysis of heart rate variability -- preliminary results.

AIMS: Conventional ICD algorithms yield approximately 10-30% of spurious interventions. Our aim was to check whether nonlinear dynamics methods might be useful in the verification of ICD interventions. METHODS AND RESULTS: We extracted 190 consecutive RR files (approximately 2000-9000 RR intervals long) from the ICDs of 70 patients (36 with coronary artery disease, 8 with hypertrophic cardiomyopathy, 19 with dilated cardiomyopathy and 7 with other diseases). The 3D phase space trajectories in delay coordinates, window pattern entropy, and algorithmic complexity of the RR intervals were examined within a 50 beat sliding window. Data were not filtered for arrhythmia and artefacts. Of the 83 recordings with appropriate interventions 79 were correctly recognised in a blind test. Two interventions were not identified in patients with fast atrial fibrillation and two in cases of complex and frequent forms of arrhythmia. There were nine spurious interventions. In all except one case (atrial fibrillation with a fast ventricular response) the analysis by nonlinear methods showed that the intervention was not necessary. All of the 98 control recordings were correctly identified in the blind test. CONCLUSIONS: The results show that nonlinear dynamics methods may be used to supplement the existing ICD detection algorithms to enhance the detection success rate.

Adult↗
PubMed2004

The Impact of Event Scale--Revised: evaluation of the subscales and correlations to psychophysiological startle response patterns in survivors of a life-threatening cardiac event: an analysis of 129 patients with an implanted cardioverter defibrillator.

BACKGROUND: The aim of the present study was to examine the reliability and validity of the Impact of Event Scale-Revised (IES-R) with special emphasis on the evaluation of the hyperarousal subscale against a standardized psychophysiological measurement. METHODS: A total of 129 survivors of a life-threatening cardiac event underwent a psychodiagnostic evaluation and a psychophysiological acoustic startle reflex (ASR) paradigm. The ASR assessed the magnitude and habituation of electromyogram (EMG) and skin conductance responses (SCR) in response to the delivery of 15 acoustic startle trials. Pearson correlation and factor analysis was used to measure reliability and construct validity. The hyperarousal subscale was validated against the ASR in terms of sensitivity and specificity mainly using receiver operating characteristic (ROC) curve analysis. RESULTS: A high reliability was found for the intrusion and avoidance subscale (alpha>0.8); however, the hyperarousal subscale showed a weaker reliability (alpha=0.66). No avoidance item, one intrusion item but four hyperarousal items revealed higher correlations to another than its assigned subscale. The hyperarousal subscale was not able to discriminate sufficiently between patients with and without exaggerated startle reactions as indicated by ROC curves running near the diagonal line. LIMITATIONS: The scores in all three subscales are lower compared to subjects traumatized by non-cardiac events. CONCLUSIONS: Reliability and construct validity for the intrusion and avoidance subscale proved to be high but was only sufficient for the hyperarousal subscale. Moreover, the criterion validity of the hyperarousal subscale regarding psychophysiological measurements is arguable and indicates further investigations in this area.

Acoustic Stimulation↗