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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 23 (2000), S. 0 
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The analysis oft wave alternans (TWA) was introduced to identify patients with an increased risk of ventricular tachyarrhythmias. The inducibility of ventricular tach-yarrhythmias and the spontaneous arrhythmic events are correlated with a positive TWA in patients with a reduced left ventricular ejection fraction and survived myocardial infarction. In contrast, this study is the first to investigate the correlation of a survived sudden cardiac death and TWA in patients without coronary heart disease and only slightly decreased left ventricular function. Sixty patients were included in the study. The TWA analysis was performed using the Cambridge Heart system (CH2000). Patients were sitting on a bicycle ergometer and exercised with a gradual increase of workload to maintain a heart rate of at least 105 beats/min. The exercise test was stopped after recording 254 consecutive low noise level heart beats. The electrocardiographic signals were digitally processed using a spectral analysis method. The magnitude of TWA was measured at a frequency of 0.5 cycles/beat. A TWA was defined as positive if the ratio between TWA and noise level was 〉 3.0 and the amplitude of the TWA was 〉 1.8 μV. Twelve (20%) of the included 60 patients showed a positive TWA. The sensitivity concerning a previous arrhythmic event amounted to 65%, the specificity up to 98%, respectively. The alternans ratio was significantly higher in patients with a previous event (30.3 ± 53.2 vs 2.9 ± 5.9, P 〈 0.001) and cumulative alternans voltage (4.67 ± 3.55 vs 1.75 ± 1.88 μV, P 〈 0.001). In 19 patients, invasively investigated by an electro-physiological study, a significant correlation between inducibility of tachyarrhythmias and a positive TWA result was found (Spearman R = 0.51, P = 0.01). In conclusion, the TWA analysis seems to identify patients with nonischemic Cardiomyopathy who are at an increased risk of ventricular tachyarrhythmias.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: For evaluation of patients with an increased risk of sudden cardiac death, the analyses of ventricular late potentials, heart rate variability, and baroreflexsensitivity are helpful. But so far, the prediction of a malignant arrhythmic event is not possible with sufficient accuracy, For a better risk stratification other methods are necessary. In this study the importance of the ChRS for the identification of patients at risk for ventricular tachyarrhythmic events should be investigated. Of 41 patients included in the study, 26 were survivors of sudden cardiac arrest. Fifteen patients were not resuscitated, of whom 6 patients had documented monomorphic ventricular tachycardia and 9 had no ventricular tachyarrhythmias in their prior history. All patients had a history of an old myocardial infarction (〉 1 year ago). For determination of the ChRS the ratio between the difference of the RR intervals in the ECG and the venous pO2 before and after a 5-minute oxygen inhalation via a nose mask was measured (ms/mmHg). The 26 patients with survived sudden cardiac death showed a significantly decreased ChRS compared to those patients without a tachyarrhythmic event (1.74 ± 1.02 vs 6.97 ± 7.14 ms/mmHg, P 〈 0.0001). The sensitivity concerning a survived sudden cardiac death amounted to 88% for a ChRS below 3.0 ms/mmHg. During a 12-month follow-up period, the ChRS was significantly different between patients with and without an arrhythmic event (1.64 ± 1.06 vs 4.82 ± 5.83 ms/mmHg, P 〈 0.01). As a further method for evaluation of patients with increased risk of sudden cardiac death after myocardial infarction the analysis of ChRS seems to be suitable and predicts arrhythmias possibly more sensitive than other tests of neurovegetative imbalance. The predictive importance has to be examined by prospective investigations in larger patient populations.
    Type of Medium: Electronic Resource
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