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Biomedical subjects

L M Porterfield

Publications and source records attributed to L M Porterfield.

At least 37 records · Page 2Linked to original sources
PubMed1994

A new approach: a single triple electrode lead system interfaced with a third generation defibrillator.

The efficacy of implantable third generation cardioverter defibrillators has been well established for the treatment of patients with malignant ventricular arrhythmias and survivors of cardiac arrest. However, many patients have been reluctant or unwilling to endure the discomfort of an open chest procedure, despite their need for the device. Furthermore, morbidity (pneumothorax, pneumonia, sepsis, pleural effusion, hemorrhage, pericarditis, etc.) and mortality associated with the application of epicardial lead systems is of concern. Finally, the mean overall expense of $80,433 for the epicardial method of defibrillator implantation is a consideration in an era of increasing cost-awareness in health care. Fortunately, the recent market-release of a single lead transvenous defibrillation system [Endotak, Cardiac Pacemakers, Inc. (CPI), St. Paul, Minnesota] may address these pressing issues. The specific purpose of this report is to demonstrate the patient benefit derived from interfacing a single endocardial lead system with a biphasic third generation defibrillator.

Defibrillators, Implantable↗
PubMed1993

Experience with three different third-generation cardioverter-defibrillators in patients with coronary artery disease or cardiomyopathy.

Clinical investigations are being performed in multiprogrammable devices whose therapeutic options include antitachycardia pacing, cardioversion, defibrillation and bradycardia pacing. Three different third-generation devices were implanted in 46 research patients at 1 clinical center to document their safety and efficacy for the treatment of malignant ventricular arrhythmias. Additionally, the purpose of the study was to determine if antitachycardia pacing is a desirable and frequently used feature of tiered devices. The Medtronic PCD was implanted in 15 patients (12 men, mean age 60 +/- 13 years, mean ejection fraction 40 +/- 15%), the Ventritex Cadence in 21 patients (17 men, mean age 65 +/- 10 years, mean ejection fraction 38 +/- 12%), and the CPI VENTAK PRx in 10 patients (8 men, mean age 63 +/- 14 years, mean ejection fraction 31 +/- 8%). All patients presented with cardiac arrest or ventricular tachycardia. During follow-up of 10 +/- 6 months (range 1 to 19), 70% of the 20 patients with antitachycardia pacing activated used the feature for spontaneous ventricular tachycardia. The antitachycardia pacing parameters were reprogrammed 20 times in 15 patients. Two thousand six hundred thirty-eight of 2,675 (98%) antitachycardia pacing attempts successfully terminated spontaneous tachyarrhythmias. Low-energy cardioversion or defibrillation terminated tachyarrhythmias in patients where pacing was unsuccessful. One hundred forty-eight episodes of tachycardia were successfully treated directly by shocks in 16 of 46 patients (35%). There were no deaths due to device failure. This initial single-center clinical experience suggests that the PCD, Cadence and VENTAK PRx are all safe and effective tiered therapy devices for the treatment of malignant ventricular arrhythmias. Antitachycardia pacing successfully terminated most episodes of ventricular tachycardia; in patients with this feature activated, it was used frequently but required reprogramming to achieve high levels of success.

Aged↗
PubMed1993

Conversion rates of induced versus spontaneous ventricular tachycardia by a third generation cardioverter defibrillator. The VENTAK PRx Phase I Investigators.

Seventy consecutive patients received the first VENTAK PRx pulse generators (Cardiac Pacemakers, Inc.) implanted in the United States. This multiprogrammable device has therapeutic options that include: (1) antitachycardia pacing; (2) low energy cardioversion; (3) defibrillation shocks; and (4) bradycardia pacing. There were 60 males and 10 females with a mean age of 65.3 +/- 9.4 years. The anatomical diagnoses were coronary artery disease in 55 patients, cardiomyopathy in 7 patients, congenital heart disease in 2 patients, and miscellaneous disease in the remaining 6 patients. Thirty-six percent had a history of sudden cardiac death and 90% had documented monomorphic ventricular tachycardia. The mean ejection fraction was 32.7% +/- 12.2%. Thirty-three (49.3%) had an ejection fraction < or = 30%. Electrophysiological testing was done preimplant, predischarge, and 1 to 2 months postimplant to define a specific electrical therapy and evaluate the efficacy of the device. Two hundred ninety-three of 367 (80%) episodes of induced ventricular tachycardia were successfully terminated by the VENTAK PRx programmed for antitachycardia pacing. There were 1,794 total therapy episodes for spontaneous ventricular tachycardia; 91% (1,641 episodes) were terminated by antitachycardia pacing and 153 episodes were converted by shocks during a minimal 6-month follow-up per patient. We conclude that documentation of a successful antitachycardia pacing modality in the electrophysiology laboratory predicts conversion of spontaneous episodes of ventricular tachycardia. Furthermore, antitachycardia pacing by the VENTAK PRx can terminate the majority of episodes of ventricular tachycardia.

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