Journal of electrocardiology
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Case Reports
Intraatrial conduction delay associated with an epicardial implantable cardioverter-defibrillator.
The implantable cardioverter-defibrillator (ICD) has become an important mode of therapy for patients at risk for sustained ventricular arrhythmias. While the survival benefit of these devices is clear, adverse consequences are coming to light. The authors report a case of dramatic intraatrial conduction delay associated with repeated ICD shocks, resulting in pacemaker syndrome in a patient who had received both an ICD and a dual-chamber pacemaker. This and other conduction disturbances may become more common as experience with ICDs grows, and may demand adjunctive or alternative therapies to prevent frequent shocks.
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The authors have investigated potential applications of artificial neural networks for electrocardiographic QRS detection and beat classification. For the task of QRS detection, the authors used an adaptive multilayer perceptron structure to model the nonlinear background noise so as to enhance the QRS complex. ⋯ For electrocardiographic QRS complex pattern classification, an artificial neural network adaptive multilayer perceptron was used as a pattern classifier to distinguish between normal and abnormal beat patterns, as well as to classify 12 different abnormal beat morphologies. Preliminary results using the MIT/BIH (Massachusetts Institute of Technology/Beth Israel Hospital, Cambridge, MA) arrhythmia database are encouraging.
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The objective of this study was to prospectively determine the utility, efficiency, and reliability of early prehospital 12-lead electrocardiogram (ECG) application, the improvement in prehospital diagnostic accuracy, and paramedic and base physician opinions regarding early application of prehospital 12-lead ECGs in a broad range of stable chest pain patients. The patient population consisted of cooperative, stable adult prehospital patients with a chief complaint of nontraumatic chest pain of presumed ischemic origin. From July 17, 1989 through January 1, 1990 paramedics acquired prehospital 12-lead ECGs on 680 stable adult chest pain patients. ⋯ Paramedic application of prehospital 12-lead ECGs was found to be efficient and reliable, and it can be applied to most cooperative stable adult prehospital chest pain patients. Prehospital 12-lead ECGs significantly improve base physicians' diagnostic accuracy in myocardial infarction, angina, and nonischemic chest pain patients. Paramedic and base physicians' opinions regarding early application of prehospital 12-lead ECGs during patient evaluation were favorable.
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A case is presented in which markedly low surface electrocardiographic (ECG) voltage and an infarction pattern are rapidly reversed with renal hemodialysis for pulmonary edema. A patient presenting with QRS voltages below 0.1 mV in all the limb and augmented limb leads and a waveform pattern suggestive of an anterior and inferior myocardial infarction experienced a dramatic increase in voltage and a reversal of the infarction pattern after dialysis. ⋯ This case illustrates one source of diagnostic error, and that dialysis may result in large, rapid changes in the ECG. Diagnostic errors may be avoided by obtaining serial ECGs in patients undergoing dialysis.
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Clinical Trial
QT interval and repolarization time in patients with intraventricular conduction delay.
A prolonged QT interval is an important prognostic indicator for cardiac arrhythmias and sudden death. The conventional QT interval measurement, however, includes in its measure the cardiac depolarization (QRS) as well as the cardiac repolarization (JT) intervals. To evaluate the relative contribution of the depolarization and the repolarization time prolongation to the prolonged QT interval in patients with intraventricular conduction delay (IVCD), the QRS, QT, and JT intervals were measured in 72 subjects with various types of IVCD. ⋯ All of these intervals were significantly prolonged compared to 430 +/- 4.3 msec in the control group. The prolongation of QTc interval in each category of IVCD subjects was entirely secondary to a prolonged depolarization time, as the repolarization intervals were not significantly different from those observed in the control group (F = 0.5, p = NS). These observations may provide an explanation for the differential prognosis for subjects with prolonged QT interval with prolonged repolarization time as compared to those with prolonged QT interval with prolonged depolarization time.