Ventricular fibrillation and polymorphic ventricular tachycardia with critical coronary artery stenosis: does bypass surgery suffice?

INTRODUCTION: Previous studies have suggested that coronary artery bypass surgery is sufficient to prevent recurrence of sudden death in patients with critical coronary artery stenosis presenting with ventricular fibrillation or polymorphic ventricular tachycardia. We present our experience in patients with one or more episodes of sudden death associated with documented ventricular fibrillation or polymorphic ventricular tachycardia and severe operable coronary artery disease who underwent defibrillator implant at the time of bypass surgery. METHODS AND RESULTS: Fifty-eight consecutive patients (age 63 +/- 8 years) were included in this study. Eighteen of the 58 patients had no evidence of previous myocardial infarction. The mean ejection fraction was 37 +/- 13%. All patients underwent electrophysiologic study before and after revascularization. At the time of first defibrillator discharge, each patient was reevaluated to exclude the presence of ischemia. The benefits of defibrillator implant were estimated comparing the projected survival based upon defibrillator discharge preceded by syncope or presyncope with survival curves generated including total death and sudden plus cardiac death. After a mean follow-up of 4.6 +/- 2 years, 22 patients received appropriate shocks preceded by syncope or presyncope, and an additional 19 patients received asymptomatic shocks. At 4 years, survival free of total death was 71.2%, and the projected survival was 58.8% (P < 0.05). Multivariate analysis showed that ejection fraction lower than 30% and induction of arrhythmia with one or two extrastimuli (S2, S3) were independent predictors for defibrillator discharge. None of the remaining variables including age, gender, number of bypasses, history of myocardial infarction, and type of arrhythmias induced were predictive for death and occurrence of shocks. CONCLUSIONS: In patients with ventricular fibrillation and polymorphic ventricular tachycardia, bypass surgery does not protect from recurrence of life-threatening arrhythmias, and, as in our population, defibrillator implant may have significant impact on survival.

Feasibility of concomitant implantation of permanent transvenous pacemaker and defibrillator systems.

In 17 patients (14 men and 3 women aged 69 +/- 10 years), a transvenous pacemaker was implanted before (8 patients), following (7 patients), or simultaneously (2 patients) with the insertion of a transvenous defibrillator. Indications included malignant ventricular arrhythmias and symptomatic bradycardia in all patients. All patients had structural heart disease. All pacemakers were non-programmable bipolar, either single chamber (n = 7) or dual chamber (n = 10). Eleven pacemakers were rate responsive. The Transvene system was implanted in 7 patients (Pacer-Cardioverter-Defibrillator in 6 patients and the Cadence defibrillator in 1). The Endotak lead system was implanted in 10 patients (Ventak in 7 patients and the Cadence in 3). The mean defibrillation threshold was 16 +/- 5 J. Repositioning of the pacemaker leads eliminated undersensing of ventricular fibrillation by the defibrillator, which occurred during asynchronous pacing in 2 patients. During a mean follow-up of 11 +/- 6 months, 2 patients died because of pump failure and 7 patients received defibrillator therapy for ventricular arrhythmias. No significant complications were noted. Successful concomitant implantation of transvenous pacemakers and defibrillators was thus accomplished in 17 patients, which suggests that insertion of a second transvenous device can be safely accomplished.

Experience with two different nonthoracotomy systems for implantable defibrillator in 170 patients.

Implantation of a nonthoracotomy system (Medtronic PCD or CPI Endotak) was attempted in 170 patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) not requiring concomitant cardiac surgery. A nonthoracotomy system could be successfully implanted in 95 of the 115 patients with the PCD system and 49 of 55 patients receiving the Endotak lead system. In 26 patients with failed nonthoracotomy system because of defibrillation threshold (DFT) > 25 joules (J), an epicardial system was implanted at the same setting. Patients receiving the two lead systems were comparable with regard to age, sex, and ejection fraction. However, since the PCD system offers tiered therapy multiprogrammable options, all attempts were made to implant this lead system in patients with VT that could be pace terminated. Mean DFT (15 +/- 4.7 vs 17 +/- 4.6 J; P = 0.03) and implant time (2.5 +/- 0.6 vs 3.3 +/- 0.7 hours; P = 0.02) were less with the Endotak lead system. There was no perioperative mortality. During a mean follow-up of 20 +/- 4 months, there were eight instances of lead dislodgment in patients receiving the PCD system. There were four nonsudden cardiac deaths and one sudden death in the Endotak group and three nonsudden deaths in the PCD group. Sudden cardiac death and total survival using the intention-to-treat analysis during this follow-up period were 99% and 95%, respectively. In conclusion, successful implantation, perioperative mortality, and survival rate are comparable with both lead systems; however, incorporating two defibrillating electrodes in one lead minimizes lead dislodgment and reduces implant time.

Molecular cloning and expression of a cDNA encoding human electron transfer flavoprotein-ubiquinone oxidoreductase.

Electron-transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO) in the inner mitochondrial membrane accepts electrons from electron-transfer flavoprotein which is located in the mitochondrial matrix and reduces ubiquinone in the mitochondrial membrane. The two redox centers in the protein, FAD and a [4Fe4S]+2,+1 cluster, are present in a 64-kDa monomer. We cloned several cDNA sequences encoding the majority of porcine ETF-QO and used these as probes to clone a full-length human ETF-QO cDNA. The deduced human ETF-QO sequence predicts a protein containing 617 amino acids (67 kDa), two domains associated with the binding of the AMP moiety of the FAD prosthetic group, two membrane helices and a motif containing four cysteine residues that is frequently associated with the liganding of ferredoxin-like iron-sulfur clusters. A cleavable 33-amino-acid sequence is also predicted at the amino terminus of the 67-kDa protein which targets the protein to mitochondria. In vitro transcription and translation yielded a 67-kDa immunoprecipitable product as predicted from the open reading frame of the cDNA. The human cDNA was expressed in Saccharomyces cerevisiae, which does not normally synthesize the protein. The ETF-QO is synthesized as a 67-kDa precursor which is targeted to mitochondria and processed in a single step to a 64-kDa mature form located in the mitochondrial membrane. The detergent-solubilized protein transfers electrons from ETF to the ubiquinone homolog, Q1, indicating that both the FAD and iron-sulfur cluster are properly inserted into the heterologously expressed protein.

Implantable cardioverter defibrillator for prevention of sudden cardiac death in patients with ventricular tachycardia and ventricular fibrillation: ICD therapy in sudden cardiac death.

Among the various therapy options for survivors of ventricular tachycardia-ventricular fibrillation (VT-VF), the implantable cardioverter defibrillator (ICD) seems most promising. It reliably terminates VT-VF and thus significantly impacts sudden cardiac death (SCD) survival. It is more effective than any of the known antiarrhythmic drugs in prevention of SCD, particularly among survivors of cardiac arrest. Compared to VT surgery, the ICD therapy can be offered to a larger pool of patients and can be placed at a lower surgical risk. With proper patient selection, ICD therapy is of major benefits to its recipients since it markedly reduces the chances of VT-VF related mortality; the main cause of premature death in this population. The ICD therapy is cost effective when compared to other medical interventions and could be more so if the implant is carried out early in the course of VT-VF management.

Reemployment following implantation of the automatic cardioverter defibrillator.

One hundred one patients who received an implantable automatic cardioverter defibrillator (ACD) were evaluated to determine the reemployment rate and factors associated with return to work. Forty-seven were employed before ACD implantation. Their mean (+/- standard deviation) age was 53 +/- 11 years, 83% were men, 75% had coronary artery disease, 76% presented with cardiac arrest and 28% had concomitant cardiac surgery. The mean ejection fraction of these patients was 0.41 +/- 0.15. At follow-up, 29 patients (62%) had resumed work at 11 +/- 9 weeks after implantation. Those who returned to work were better educated (15 vs 11 years, p less than 0.001) and less likely to have a history of prior myocardial infarction (p less than 0.05). There were no significant differences between patients who returned to work and those who did not in terms of age, sex, race, functional class, ejection fraction, extent of coronary artery disease, reason for ACD, or concomitant surgery. Multivariate analysis revealed that level of education was the single best predictor of reemployment status. The only other factors found to add significant predictive power in a stepwise analysis were extent of coronary artery disease and marital status. The model using these 3 variables had a sensitivity of 83% and a specificity of 72%. It was concluded that (1) most patients employed before ACD implantation are able to return to work after the procedure, and (2) nonmedical factors play an important role in the resumption of work-related activities. These findings have important quality-of-life and cost-effectiveness implications for ACD implantees.