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Biomedical subjects

William H Maisel

Publications and source records attributed to William H Maisel.

At least 19 recordsLinked to original sources
PubMed2006

Pacemaker and ICD generator malfunctions: analysis of Food and Drug Administration annual reports.

CONTEXT: Pacemakers and implantable cardioverter-defibrillators (ICDs) are complex medical devices proven to reduce mortality in specific high-risk patient populations. It is not known if increasing device complexity is associated with decreased reliability. OBJECTIVES: To analyze postapproval annual reports submitted to the US Food and Drug Administration (FDA) by manufacturers of pacemakers and ICDs to determine the reported number and rate of pacemaker and ICD malfunctions and to assess trends in device performance. DESIGN AND SETTING: Pacemaker and ICD annual reports submitted to the FDA for the years 1990-2002 were reviewed. A pacemaker or ICD generator was defined as having malfunctioned if it was explanted due to an observed malfunction, returned to the manufacturer, and confirmed by the manufacturer to be functioning inappropriately. Leads and biventricular devices were not included in the study. Deaths were attributed to device malfunction only if they were witnessed, the malfunction immediately led to the death, and the malfunction was confirmed by the manufacturer. MAIN OUTCOME MEASURES: Number of implanted pacemaker and ICD generators; number of reported malfunctions; and annual malfunction replacement rates. Generator malfunction replacement rates were defined as the annual number of replacements due to confirmed malfunction divided by the annual number of implants. RESULTS: During the study period, 2.25 million pacemakers and 415,780 ICDs were implanted in the United States. Overall, 17,323 devices (8834 pacemakers and 8489 ICDs) were explanted due to confirmed malfunction. Battery/capacitor abnormalities (4085 malfunctions [23.6%]) and electrical issues (4708 malfunctions [27.1%]) accounted for half of the total device failures. The annual pacemaker malfunction replacement rate per 1000 implants decreased significantly during the study, from a peak of 9.0 in 1993 to a low of 1.4 in 2002 (P = .006 for trend). In contrast, the ICD malfunction replacement rate per 1000 implants, after decreasing from 38.6 in 1993 to 7.9 in 1996, increased markedly during the latter half of the study, peaking in 2001 at 36.4 (P = .04 for trend). More than half of the reported ICD malfunctions occurred in the last 3 years of the study. Overall, the annual ICD malfunction replacement rate was significantly higher than the pacemaker malfunction replacement rate (mean [SD], 20.7 [11.6] vs 4.6 [2.2] replacements per 1000 implants; P<.001; rate ratio, 5.9 [95% confidence interval, 2.7-9.1]). Sixty-one deaths (30 pacemaker patients, 31 ICD patients) were attributable to device malfunction. CONCLUSIONS: This study demonstrates that thousands of patients have been affected by pacemaker and ICD malfunctions, the pacemaker malfunction replacement rate has decreased, the ICD malfunction replacement rate increased during the latter half of the study, and the ICD malfunction replacement rate is significantly higher than that for pacemakers. Although pacemakers and ICDs are important life-sustaining devices that have saved many lives, careful monitoring of device performance is still required.

Defibrillators, Implantable↗
PubMed2006

Pacemaker and ICD generator reliability: meta-analysis of device registries.

CONTEXT: Despite there being millions of pacemaker and implantable cardioverter-defibrillator (ICD) generator implants worldwide, little is known about device reliability. OBJECTIVES: To perform a meta-analysis of prospective pacemaker and ICD registries to determine annual rates of pacemaker and ICD malfunction and to identify trends in these rates. DATA SOURCES: MEDLINE (January 1966 to April 2005), the Cochrane Central Register of Controlled Trials (through second quarter 2005), the Cochrane Database of Systematic Reviews (through second quarter 2005), and a bibliographic review of secondary sources. Search terms included pacemaker, artificial; defibrillators, implantable; registries; performance; and malfunction. STUDY SELECTION: Eligible registries were prospective; reported the number of patients with pacemaker, ICD, or both; and allowed determination of the annual number of device malfunctions. Of 1007 references screened, 3 registries meeting the selection criteria were identified and included 2.1 million pacemaker person-years and 14,821 ICD person-years of observation. DATA EXTRACTION: Included the annual number of patients with pacemakers and ICDs at risk of device failure and the annual number of generator malfunctions (1983-2004 for pacemakers, 1988-2004 for ICDs). A device malfunction was defined as an integral component failure that required device explantation prior to reaching elective replacement. Failures of pacemaker and ICD electrodes were not included in the study. DATA SYNTHESIS: There were 2981 pacemaker and 384 ICD generator malfunctions. Pacemaker reliability improved markedly during the 1980s (P for trend <.001) and the pacemaker malfunction rate remained low during the remainder of the study. Implantable cardioverter-defibrillator reliability improved during the first 10 study years (P for trend <.001). From 1998-2002, however, the ICD malfunction rate increased more than 4-fold (P for trend <.001), before decreasing substantially in the latter 2 years of the study. Overall, the mean (SE) annual ICD malfunction rate was about 20-fold higher than the pacemaker malfunction rate (26.5 [3.8] vs 1.3 [0.1] malfunctions per 1000 person-years, P<.001). Battery malfunctions were the most common cause of device failure. CONCLUSIONS: Pacemaker reliability has improved markedly. In contrast, after more than a decade of improving device reliability, the ICD malfunction rate transiently increased before experiencing substantial reductions in the latter 2 study years. Whether increasing device sophistication accounts for the observed decrease in reliability is not known. Continued monitoring of pacemaker and ICD performance is required.

Defibrillators, Implantable↗
PubMed2006

Predicting early mortality after implantable defibrillator implantation: a clinical risk score for optimal patient selection.

BACKGROUND: Patients with advanced heart disease are at risk from sudden death; however, benefit from implantable cardioverter defibrillators (ICDs) may be limited as a result of early mortality from other causes. The objective of this study was to develop a model to predict mortality within the first year after ICD implantation. METHODS AND RESULTS: A retrospective analysis was performed of 469 consecutive patients who underwent ICD implantation at a single tertiary-care center from 1999 to 2002. Vital status was determined from the Social Security Death Index. Patients were randomized into prediction and validation cohorts. A risk score was derived from the prediction cohort by multivariate logistic regression and applied to the validation cohort. One point was assigned for each variable in the risk score (age > 80 years, history of atrial fibrillation, creatinine > 1.8 mg/dL, New York Heart Association class III or IV). One-year mortality significantly increased with increasing risk score in both the prediction and validation cohorts. Validation cohort mortality was 3.4% for 0 points, 4.3% for 1 point, 17% for 2 points, and 33% for > or = 3 points (P for trend < .0001). A risk score > or = 2 predicted a 1-year mortality rate of 21%, whereas a risk score < 2 predicted a mortality rate of 4% at 1 year (P < .0001). CONCLUSION: A risk score using simple clinical criteria may identify patients at high risk of early mortality after ICD implantation. This may be helpful in consideration of ICD risk/benefit for individual patients. Further studies conducted in a prospective manner using these clinical criteria are warranted.

Aged↗
PubMed2005

Impact of changing activation sequence on bipolar electrogram amplitude for voltage mapping of left ventricular infarcts causing ventricular tachycardia.

INTRODUCTION: Wavefront direction is a determinant of bipolar electrogram amplitude that could influence identification of low amplitude regions indicating infarction or scar. METHODS: To assess the importance of activation sequence on electrogram amplitude 11 patients with prior infarction and ventricular tachycardia were studied. At 819 left ventricular sites bipolar electrograms were recorded during atrial pacing and ventricular pacing, followed by unipolar pacing with a stimulus of 10 mA at 2 ms. Sites with a pacing threshold > 10 mA were designated electrically unexcitable scar. RESULTS: Areas of low voltage (< or =1.5 mV) were present in all patients. Atrial paced and ventricular paced electrogram amplitudes were strongly correlated (r = 0.77; P < 0.0001). Changing the activation sequence (from atrial pacing to ventricular pacing) produced a > 50% change in electrogram amplitude at 28% of sites and a > 100% change at 10% of sites, but only 8% of sites had an electrogram amplitude classified as abnormal (< or =1.5 mV) with one activation sequence and normal (> 1.5 mV) with the other activation sequence. Electrically unexcitable scar (6% of sites) was associated with lower electrogram amplitude but could not be reliably identified based on electrogram amplitude alone for either activation sequence. CONCLUSION: Voltage maps created with bipolar recordings using these methods should be relatively robust depictions of abnormal ventricular regions despite variable catheter orientation and activation sequences that might be produced by different rhythms.

Aged↗
PubMed2005

Atrial fibrillation in heart failure: high mortality risk even if ventricular function is preserved.

BACKGROUND: The purpose of this study was to determine if patients with atrial fibrillation (AF) and heart failure (HF) have a better prognosis when systolic function is preserved as compared with those with depressed systolic function. METHODS: Data from consecutive patients presenting to the emergency department at Brigham and Women's Hospital from January 1997 to December 2002 who had a diagnosis of AF and HF and a measure of ejection fraction (EF) were reviewed. Vital status was determined from the Social Security Death Index. RESULTS: Of 478 patients (mean age 74 +/- 13 years; 47% women), EF was preserved (> 50%) in 46%. Those with preserved left ventricular (LV) function were older (76 vs 72 years, P < .0020), included more women (62 vs 35%, P < .0001), more likely to have a history of hypertension and pulmonary disease and less likely to have had a prior myocardial infarction. At 5 years, mortality was similar between the preserved and depressed EF groups (50% vs 48%, P = .74). In multivariable analysis, age > 75 years, history of cancer, cerebrovascular disease, aortic valve disease, serum creatinine > 2.0 mg/dL, and serum sodium < 130 mmol/L were associated with increased mortality. Therapy with beta-blockers and angiotensin-converting enzyme inhibitors/angiotensin receptor blocker were associated with lower mortality. CONCLUSION: Patients who present to the emergency department with AF, HF, and preserved LVEF have a similarly high mortality as compared with those with depressed LVEF. Further study is needed to assess the impact of therapies and clarify the reasons for the poor prognosis.

Aged↗
PubMed2005

Impact of implantable cardioverter defibrillators on survival and recurrent hospitalization in advanced heart failure.

BACKGROUND: Although implantable cardioverter defibrillators (ICDs) are increasingly used in advanced (class III/IV) heart failure, their benefits may be limited by death from pump failure and data are limited. The aim of this study was to assess the impact of QRS duration and disease etiology on survival and rehospitalization in advanced heart failure patients with ICDs. METHODS: A retrospective study of 438 patients with heart failure (age 56 +/- 15, ejection fraction 29 +/- 15, 76% class III/IV) discharged between 1996 and 2000 was performed. RESULTS: An ICD was placed in 94 of the 438 patients for nonsustained (51.1%) or sustained (24.4%) ventricular arrhythmia, syncope (16.0%), or prophylaxis (8.5%). Patients with ICDs had a lower mean baseline ejection fraction (25% vs 30%, P = .007) but a trend toward fewer class IV symptoms (33% vs 44%, P = .164). Patients with ICDs had better survival (RR 0.48, P = .001) but increased rehospitalization (RR 1.41, P = .031). In both the ischemic and nonischemic subgroups, survival was superior in patients with ICDs (RR 0.38, P = .003 and RR 0.54, P = .042). Patients with QRS < 120 milliseconds had a trend toward better survival with an ICD (RR 0.42, P = .119) but increased rehospitalization (RR 2.13, P = .021). Patients with QRS > or = 120 milliseconds had better survival with an ICD (RR 0.45, P = .001) without increased risk of rehospitalization (RR 1.22, P = .314). CONCLUSIONS: Patients with advanced heart failure selected to receive ICDs have better survival trends but shorter time to rehospitalization than patients without ICDs. Benefit appears greater for those with prolonged QRS duration.

Defibrillators, Implantable↗
PubMed2005

The role of cardiac pacing: American College of Chest Physicians guidelines for the prevention and management of postoperative atrial fibrillation after cardiac surgery.

New-onset atrial fibrillation (AF) occurs frequently after cardiac surgery. The utility of prophylactic atrial pacing to prevent AF following cardiac surgery has been investigated in a number of trials, but clinical guidelines for its use are lacking. Trials of prophylactic atrial pacing to prevent AF following cardiac surgery were identified by searching PubMed, the Cochrane database, selected medical journals, and references in selected articles. Nine randomized controlled trials were identified that addressed prophylactic atrial pacing after cardiac surgery to prevent AF. Prophylactic right atrial pacing and prophylactic left atrial pacing have yielded inconclusive results. Prophylactic biatrial pacing (BAP) reduced the incidence of AF significantly in four studies, reduced it nonsignificantly in one study, and had no effect in one study. On the basis of the literature that was reviewed and graded for quality, it was concluded that prophylactic atrial pacing to prevent AF after cardiac surgery is safe. We recommend that BAP be considered, particularly in patients who are at high risk for the development of postoperative AF.

Atrial Fibrillation↗
PubMed2004

Implantable defibrillators for the prevention of mortality in patients with nonischemic cardiomyopathy: a meta-analysis of randomized controlled trials.

CONTEXT: Implantable cardioverter defibrillator (ICD) therapy is effective in primary and secondary prevention of sudden cardiac death among patients with prior myocardial infarction and depressed ejection fraction. However, conclusive evidence of survival benefit in patients with nonischemic cardiomyopathy (NICM) is still lacking. OBJECTIVE: To determine whether ICD therapy reduces all-cause mortality in patients with NICM. DATA SOURCES: MEDLINE (1966-2004), EMBASE (1991-2004), the Cochrane Central Register of Controlled Trials (through first quarter, 2004), reports presented at scientific meetings (2003-2004), and bibliographic review of secondary sources. Search terms included defibrillator, randomized controlled trials, clinical trials, and sudden death. STUDY SELECTION: Eligible studies were prospective randomized controlled trials of ICD or combined cardiac resynchronization therapy and defibrillator (CRT-D) vs medical therapy enrolling at least some individuals with NICM and reporting all-cause mortality as an outcome. Of 675 potentially relevant articles screened initially, 8 reports of randomized trials enrolling a total of 2146 patients with NICM were included. DATA EXTRACTION: Included studies were reviewed to determine the number of patients randomized, mean duration of follow-up, primary end point, mortality of ICD cohort, and mortality of control cohort. DATA SYNTHESIS: Five primary prevention trials enrolling 1854 patients with NICM were identified; pooled analysis suggested a significant reduction in total mortality among patients randomized to ICD or CRT-D vs medical therapy (risk ratio [RR], 0.69; 95% confidence interval [CI], 0.55-0.87; P = .002). Mortality reduction remained significant even after elimination of CRT-D trials. Two of the 3 secondary prevention trials presented subgroup estimates for ICD efficacy in NICM. Pooled analysis of these secondary prevention trials (n = 256 patients with NICM) indicated an equivalent but nonsignificant mortality reduction with ICD therapy (RR, 0.69; 95% CI, 0.39-1.24; P = .22). Analysis of all 7 trials combined demonstrated a statistically significant 31% overall reduction in mortality with ICD therapy (RR, 0.69; 95% CI, 0.56-0.86; P = .002). CONCLUSION: ICD therapy appears to significantly reduce mortality in selected patients with NICM.

Cardiomyopathies↗
PubMed2004

Identification of the ventricular tachycardia isthmus after infarction by pace mapping.

BACKGROUND: Ventricular tachycardia (VT) isthmuses can be defined by fixed or functional block. During sinus rhythm, pace mapping near the exit of an isthmus should produce a QRS similar to that of VT. Pace mapping at sites proximal to the exit may produce a similar QRS with a longer stimulus-to-QRS interval (S-QRS). The aim of the study was to determine whether a VT isthmus could be identified and followed by pace mapping. METHODS AND RESULTS: Left ventricular pace mapping during sinus rhythm was performed at 819 sites in 11 patients with VT late after infarction, and corresponding CARTO maps were reconstructed. An isthmus site was defined by entrainment and/or VT termination by ablation. Pace-mapping data were analyzed from the identified isthmus site and from sites at progressively increasing distances from this initial isthmus site. Sites where pace mapping produced the same QRS with different S-QRS delays were identified to attempt to trace the course of the isthmus. In 11 patients, 13 confluent low-voltage infarct regions were present. In all these regions, parts of VT isthmuses were identified by pace mapping. In 11 of 13 of the identified isthmus parts, the QRS morphology of the pace map matched a VT QRS. In 10 of 11 patients, radiofrequency ablation rendered clinical VTs noninducible. Successful ablation sites were localized within an isthmus identified by pace mapping in all of these 10 patients. CONCLUSIONS: VT isthmuses can be identified and part of their course delineated by pace mapping during sinus rhythm. This method could help target isthmus sites for ablation during stable sinus rhythm.

Aged↗
PubMed2004

Medical device regulation: an introduction for the practicing physician.

Patient care for the practicing physician increasingly relies on medical devices. The U.S. Food and Drug Administration is responsible for the safety and effectiveness of medical devices in the United States. In addition to playing a role in the clinical use of devices, physicians may also participate in their design, production, use, and safety by expressing their need for certain products, by providing practical input and feedback into product design, by participating in device-related research, and by reporting device-related adverse events. Physicians should understand the rules that govern the approved and unapproved use of medical devices as well as device premarket evaluation and approval processes and device postmarket surveillance.

Consumer Product Safety↗
PubMed2004

Identification and ablation of three types of ventricular tachycardia involving the his-purkinje system in patients with heart disease.

INTRODUCTION: Ventricular tachycardia (VT) with involvement of the His-Purkinje system (HPS) can be difficult to recognize in patients with heart disease, but it may be particularly susceptible to ablation targeting the HPS. This study defines the incidence and types of HPS involvement in VT. METHODS AND RESULTS: Involvement of the HPS was sought during electrophysiologic study with catheter mapping in 234 consecutive patients referred for catheter ablation of recurrent VT associated with heart disease. HPS VT was observed in 20 (8.5%) patients (mean ejection fraction 29%+/- 17%); in 9 (11%) of 81 patients with nonischemic heart disease and 11 (7.1%) of 153 patients with coronary artery disease (P = NS). Three types of HPS VT were observed: 16 patients (group 1) had typical bundle branch reentry, 2 patients (group 2) had bundle branch reentry and interfascicular reentry, and 2 patients (group 3) had VT consistent with a focal origin in the distal HPS. In all three groups, the VT QRS had morphologic similarity to the sinus rhythm QRS. Ablation of HPS VT was successful in all patients in whom it was attempted but produced high-degree AV block in 6 (30%). In 12 patients (60%), other VTs due to reentry through scar also were inducible. CONCLUSION: Involvement of the HPS in VT associated with heart disease has three distinct clinical forms, all of which are susceptible to ablation. Ablation often is not sufficient as the sole therapy due to other induced VT's and conduction abnormalities, requiring pacemaker and/or defibrillator implantation.

Adult↗