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Biomedical subjects

Stephen C Vlay

Publications and source records attributed to Stephen C Vlay.

12 recordsLinked to original sources
PubMed2006

Multicenter experience with failed and recalled implantable cardioverter-defibrillator pulse generators.

BACKGROUND: Despite the widespread and growing use of implantable cardioverter-defibrillators (ICDs), little information is available regarding their performance or the impact of advanced pacing functions on ICD reliability and longevity. OBJECTIVES: The purpose of this study was to examine the performance of contemporary ICD pulse generators that failed or were replaced because of manufacturers recalls. METHODS: ICD data were entered prospectively by nine participating centers. ICD pulse generator failure was defined as removal from service because the device was not functioning according to the manufacturer's specifications. A recalled ICD was a normally functioning pulse generator that was replaced as the result of a recall or advisory. RESULTS: From 1998 to 2005, 1,220 ICDs failed and 135 were recalled and replaced. The average implant time of failed ICDs was 4.4 +/- 1.5 years and of recalled ICDs was 1.7 +/- 0.8 years. The average implant time of single- and dual-chamber ICDs with rate responsive or cardiac resynchronization (CRT-D) pacing capabilities was significantly shorter than the average implant time of single- or dual-chamber devices without these features (P <.001). ICDs that provided rate responsive or CRT-D pacing failed earlier because of battery depletion (P <.001) and were significantly more prone to unexpected electronic or housing failure (9% vs 5%, P = .008) and recalls (25% vs 1%, P <.0001). Major adverse events included death (n = 2), failure to convert ventricular tachyarrhythmias (n = 6), and inappropriate shocks (n = 11). CONCLUSION: Based on our analysis of failed and recalled devices, the performance of contemporary ICDs has been adversely affected by premature battery depletion, electronic failure, and manufacturers' recalls. Additional studies are needed to precisely estimate ICD longevity and to determine the incidence of unexpected ICD failure.

Defibrillators, Implantable↗
PubMed2006

Biventricular pacing using dual-site right ventricular stimulation: is it placebo effect?

Alternate site lead placement in cardiac resynchronization therapy has been used successfully but remains to be validated. A 62-year-old heart failure patient in whom coronary sinus lead placement was not possible underwent implantation of the lead in the right ventricular outflow tract (RVOT) and demonstrated clinical improvement as measured by New York Heart Association class and noninvasive parameters. When heart failure recurred, it was determined that his RVOT electrode had been pulled back (Twiddler's syndrome). Repositioning again improved his clinical status and noninvasive hemodynamic measurements. With dual-site right ventricular (RV) pacing there was no echocardiographic measurable intraventricular dyssynchrony. Tissue Doppler imaging correlated with clinical improvement using dual-site RV pacing, providing evidence that this technique may represent a viable alternative in cardiac resynchronization therapy.

Cardiac Pacing, Artificial↗
PubMed2006

Right ventricular outflow tract pacing: practical and beneficial. A 9-year experience of 460 consecutive implants.

BACKGROUND: Pacing from the right ventricular apex (RVA) in patients with ventricular dysfunction has been identified as a possible contributor to deterioration of ventricular function. Therefore, alternative pacing sites such as the right ventricular outflow tract (RVOT) are receiving intensified scrutiny. An unresolved question is whether technical, procedural, and stability issues are comparable for the RVA and the RVOT. METHODS: This report details 460 consecutive ventricular pacing lead implants with the primary intended site in the RVOT. Patients were evaluated for success, complication rates, and followed-up for stability of pacing parameters. The total patient implant population included 300 male and 170 female patients with a mean age of 70.6 years. Ten patients were excluded from the analysis, since there was a primary indication and intention to implant in the RVA, leaving a total of 460 patients for analysis. The indications for pacing were symptomatic bradycardia due to any cause and/or Mobitz II or complete heart block. There was no clinical evidence of heart failure in 420 patients. In 40 patients with heart failure, the indication for pacing was cardiac resynchronization therapy using the RVOT as an alternate site when pacing from a branch vein of the coronary sinus was not possible. Outcome information was obtained from the implanter's clinic. RESULTS: The overall success rate in the RVOT was 84% over the total 9-year period with a 92% success rate in the last 4(1/2) years, using the RVOT technique described. At 20 months in a subgroup comparison of RVOT and RVA implants, there was no significant difference in pacing threshold, R-wave sensing, or pacing lead impedance. Dislodgment occurred in only 1 of 460 patients. Reasons for failure to implant in the RVOT include inability to find a stable position with adequate pacing and sensing thresholds (related to anatomy, scarred myocardium, pulmonary hypertension, tricuspid regurgitation), hemodynamic instability limiting time for implant, and a learning curve. Long-term stability and lead performance were excellent, and certain acute and chronic complications of RV pacing did not occur.

Aged↗
PubMed2004

Orthotripsy mimicking asystole.

An insertable loop recorder implanted to evaluate dizziness, documented an apparent arrhythmia during an orthotripsy procedure. Review of the tracing revealed artefact related to an electrostatic discharge that should not be mistaken for ventricular asystole.

Diagnosis, Differential↗
PubMed2003

Alternatives when coronary sinus pacing is not possible.

Biventricular pacing via a branch vein of the coronary sinus is not always possible due to anatomical reasons including phrenic nerve stimulation, scarred myocardium unable to sense or pace, and distorted anatomy prohibiting entry into the coronary sinus. Three patients are described in which alternative site pacing with an electrode in the right ventricular outflow tract alone or as a part of biventricular pacing system in the right ventricle provided a major improvement in dyspnea, congestive heart failure, New York Heart Association functional class, and ability to ambulate.

Aged↗
PubMed2002

Ventricular tachycardia as the initial manifestation of ischemia: Documentation of a Mechanism presaging sustained tachyarrhythmias.

Nonsustained ventricular tachycardia was the initial and only clinical manifestation of myocardial ischemia in a 64-year-old woman evaluated for new onset palpitations. There was no ECG or echocardiographic evidence of ischemia but emergent coronary angiography revealed critical lesions. After angioplasty and stenting of the right coronary artery, ventricular ectopy disappeared. This report documents a mechanism of initiation of sustained ventricular arrhythmias.

Angioplasty↗
PubMed2002

Long-term structural failure of coaxial polyurethane implantable cardioverter defibrillator leads.

Transvene models 6936/6966, a coaxial polyurethane ICD lead, may be prone to structural failure. These models comprise 54% of ICD lead failures in the authors' Multicenter Registry database. Because ICD leads perform a vital function, the clinical features, causes, and probability of Transvene 6936/6966 lead failure were determined. The Registry and United States Food and Drug Administration databases were queried for the clinical features and structural causes of the Transvene 6936/6966 lead failure, and a five-center substudy estimated the survival probability for 521 Transvene 6936/6966 implants. The mean time to failure was 4.8 +/- 2.1 years, and the estimated survival at 60 and 84 months after implant were 92% and 84%, respectively. Oversensing was the most common sign of failure (76%), and 24 patients experienced inappropriate shocks. The manufacturer's reports indicated that high voltage coil fracture and 80A polyurethane defects were the predominant causes of lead failure. Transvene models 6936 and 6966 coaxial polyurethane ICD leads are prone to failure over time. Patients who have these leads should be evaluated frequently. Additional studies are needed to identify safe management strategies.

Death, Sudden, Cardiac↗