Journal of cardiovascular electrophysiology
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J. Cardiovasc. Electrophysiol. · Oct 2002
Comparative StudyPostresuscitation stunning: postfibrillatory myocardial dysfunction caused by reduced myofilament Ca2+ responsiveness after ventricular fibrillation-induced myocyte Ca2+ overload.
Resuscitation from ventricular fibrillation (VF), particularly from prolonged VF, frequently is complicated by postfibrillatory myocardial dysfunction (postresuscitation stunning). We tested whether this dysfunction can be caused by reduced myofilament Ca2+ responsiveness after VF-induced myocyte Ca2+ overload. We also tested whether electrical defibrillation shocks contribute to this dysfunction. ⋯ Postfibrillatory myocardial dysfunction can be caused by reduced myofilament Ca2+ responsiveness after VF-induced myocyte Ca2+ overload. Electrical defibrillation shocks (up to 15 J/g wet heart weight), however, do not significantly contribute to this dysfunction. Our findings suggest that early additional therapy targeting intracellular Ca2+ overload may normalize myocyte Ca2+ and partially prevent postresuscitation stunning.
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J. Cardiovasc. Electrophysiol. · May 2002
Effects of thoracic spinal cord stimulation on cardiac autonomic regulation of the sinus and atrioventricular nodes.
Thoracic spinal cord stimulation (SCS) has been used to treat angina pectoris and to produce cardiac autonomic control. We studied the effect of thoracic SCS on sinus node and AV nodal function to test the hypothesis that SCS modulated autonomic regulation of the electrophysiology of these structures. ⋯ SCS appears to enhance parasympathetic activity, mediated via the vagus. This may have implications for use of thoracic SCS to treat chronic angina and perhaps prevent sudden cardiac death.
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J. Cardiovasc. Electrophysiol. · May 2002
Discrimination of ventricular tachycardia from supraventricular tachycardia by a downloaded wavelet-transform morphology algorithm: a paradigm for development of implantable cardioverter defibrillator detection algorithms.
Present implantable cardioverter defibrillators (ICDs) have algorithms that discriminate supraventricular tachycardia (SVT) from ventricular tachycardia (VT). One type of algorithm is based on differences in morphology of ventricular electrograms during VT and SVT. Prior SVT-VT discrimination algorithms have not undergone real-time evaluation in ambulatory patients until they were incorporated permanently into ICDs. This approach may result in incomplete testing of electrogram morphology algorithms because they are influenced by posture, activity, and electrogram maturation. We downloaded software into implanted ICDs to study a novel algorithm that compares morphologies of baseline and tachycardia electrograms based on differences between corresponding coefficients of their wavelet transforms. This comparison is expressed as a match-percent score. ⋯ The wavelet morphology algorithm has high sensitivity for VT detection. Inappropriate detections of SVT as VT may be reduced by optimal programming. Downloadable software permits evaluation of new algorithms in implanted ICDs.
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J. Cardiovasc. Electrophysiol. · May 2002
Case ReportsOsborn waves associated with ventricular fibrillation in a patient with vasospastic angina.
A 52-year-old man with a history of vasospastic angina experienced a severe ischemic episode accompanied by a non-Q wave myocardial infarction. Two episodes of ventricular fibrillation (VF) occurred during the acute phase of the event. ⋯ The Osborn waves appeared to be related to the occurrence of VF. This case may provide clinical evidence that a prominent I(to) participates in the development of VF during myocardial ischemia.