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N A Mark Estes

Publications and source records attributed to N A Mark Estes.

At least 19 recordsLinked to original sources
PubMed2006

Comparing classifications of death in the Mode Selection Trial: agreement and disagreement among site investigators and a clinical events committee.

Clinical events committees (CECs) are the current standard for endpoint adjudication in clinical trials. However, little data exist with which to compare CEC and site investigator determinations or to evaluate internal agreement among CEC members. Using data from the Mode Selection Trial in Sinus Node Dysfunction (MOST), we analyzed classifications of death in order to compare internal agreement among CEC physician reviewers and agreement between the CEC and site investigators. Death was classified at 2 levels: by major cause (cardiac, noncardiac, or unknown) and by minor subclassification of the major classifications. Reviewer agreement was tabulated at the major and minor levels, and standard and weighted kappa statistics were calculated. Disagreement at both levels was also determined. Individual decision-making was tabulated in terms of frequency in classifying death as unknown. All 404 deaths were classified by the CEC. Site investigators determined major classifications in 382 cases and minor classification in 379 cases. The CEC and the site investigators disagreed in classifying 41 cases (10.7%) at the major level and 117 (30.9%) at the minor level. CEC reviewers disagreed internally at the major level in 64 cases (15.8%), at the minor level in 63 cases (15.6%), and at any level in 127 cases (31.4%) (kappa = 0.60, 95% confidence interval (CI) [0.55, 0.66]; weighted kappa = 0.66, 95% CI [0.62, 0.75]). In resolving internal disagreements, the full CEC agreed with 1 of 2 CEC reviewers in 85.9% of cases. Disagreements occurred between site investigators and CEC reviewers in classifying deaths. Endpoint determination and decision-making varied among individual CEC reviewers, but second-tier reviews by the full CEC resolved all disagreements. These findings support continued use of CECs for endpoint adjudication in clinical trials.

Cause of Death↗
PubMed2006

Failure of commercially available chest wall protectors to prevent sudden cardiac death induced by chest wall blows in an experimental model of commotio cordis.

OBJECTIVE: Sudden cardiac death that results from chest wall blows (commotio cordis) the second leading cause of death in young athletes. Most events are caused by blows from projectiles, such as baseballs or lacrosse balls, with a substantial proportion occurring despite the use of a chest protector. In the present experiment, we tested the effectiveness of commercially available chest protectors in preventing ventricular fibrillation (VF) that results from chest wall strikes with baseballs and lacrosse balls. METHODS: Twelve different baseball or lacrosse chest protectors were evaluated in juvenile swines that were subjected to 40-mph baseball or lacrosse ball blows to the precordium during the vulnerable period of repolarization for VF and were compared with control impacts without chest protectors. Seven baseball chest protectors were hit by regulation baseballs, and 5 lacrosse chest protectors were tested by blows with standard lacrosse balls. Each animal received 2 chest blows for each protector and 2 control impacts without a chest protector, with the sequence of impacts assigned randomly. RESULTS: VF was elicited by 12 (32%) of 37 strikes in control animals without baseball chest protectors. None of the baseball chest wall protectors tested were shown to decrease significantly the occurrence of VF when compared with controls. VF was elicited by 11 (46%) of 24 strikes in control animals without lacrosse chest protectors. None of the lacrosse chest wall protectors tested decreased significantly the occurrence of VF when compared with controls. CONCLUSION: In our experimental animal model of commotio cordis, commercially available baseball and lacrosse chest wall protectors were ineffective in protecting against VF that was triggered by chest blows and, by inference, sudden cardiac death. Improvements in materials and design of chest wall barriers are necessary to reduce the occurrence of these tragic events and make the athletic field safer for youths.

Adolescent↗
PubMed2006

Equivalent arrhythmic risk in patients recently diagnosed with dilated cardiomyopathy compared with patients diagnosed for 9 months or more.

BACKGROUND: The Centers for Medicare and Medicaid Services (CMS) recently expanded coverage for implantable cardioverter-defibrillators (ICDs) in patients with left ventricular ejection fraction < or =35% and nonischemic dilated cardiomyopathy for > or =9 months. To investigate the ramifications of these criteria, the ICD registry from Tufts-New England Medical Center was analyzed for arrhythmic events and death in patients with newly diagnosed (<9 months) vs late-diagnosed (> or =9 months) nonischemic dilated cardiomyopathy. OBJECTIVES: The purpose of this study was to analyze the arrhythmic risk in patients with recent vs late diagnosis of nonischemic dilated cardiomyopathy. METHODS: One hundred thirty-one patients with nonischemic dilated cardiomyopathy were divided into two cohorts (<9 or > or =9 months of symptoms) and analyzed for any occurrence of treated ventricular arrhythmia, potentially lethal arrhythmias defined as ventricular flutter rates > or =230 bpm, and ventricular fibrillation. Patients with documented sustained ventricular tachycardias (included in prior CMS coverage) were excluded. RESULTS: In the study group, the mean age was 58.1 +/- 15 years and ejection fraction 20.6% +/- 8%. In a follow-up period of 25.3 +/- 24 months, the 52 patients with a recent diagnosis (1.4 +/- 2 months) had no difference in the occurrence of ventricular arrhythmias (P = .49) and malignant ventricular arrhythmias (P = .16) compared with the 79 patients diagnosed > or =9 months (mean 58.1 +/- 39 months). CONCLUSION: Patients with nonischemic dilated cardiomyopathy experienced equivalent occurrences of treated and potentially lethal arrhythmias irrespective of diagnosis duration. These findings suggest that the 9-month time qualifier used in the CMS guidelines for ICD reimbursement may not reliably discriminate patients at high risk for sudden cardiac death in this selected population.

Adult↗
PubMed2006

High risk of ventricular arrhythmias in patients with nonischemic dilated cardiomyopathy presenting with syncope.

It is not entirely clear whether the presentation of syncope in patients with nonischemic dilated cardiomyopathy (NIDC) is an ominous prognostic indicator, because randomized controlled implantable cardioverter-defibrillator (ICD) trials generally exclude such patients. This study compared 108 consecutive patients with NIDC presenting with syncope with 71 consecutive patients with NIDC who presented with sustained ventricular arrhythmias, with regard to freedom from any ventricular arrhythmias or life-threatening arrhythmias and all-cause mortality. There was no significant difference between the groups in the 3 outcomes during the follow-up of 43.5 +/- 32.1 months. Male gender and ICD therapy predicted increased risk for any ventricular arrhythmias. A reduced left ventricular ejection fraction and increased age were predictive of increased mortality. In conclusion, patients with NIDC presenting with syncope are a high-risk group, with event rates similar to patients with NIDC presenting with sustained arrhythmias, and should be considered for ICD therapy.

Aged↗
PubMed2006

Cryoablation of the pulmonary veins using a novel balloon catheter.

INTRODUCTION: Pulmonary vein (PV) isolation has emerged as a promising technique for the treatment of patients with drug-refractory atrial fibrillation, however, the achievement of transmural lesions has remained a challenge. We evaluated the ability of a novel balloon-based cryogenic catheter system in achieving transmural lesions for PV isolation. METHODS: Six pulmonary vein ostia from three excised ovine hearts and lungs were used in this study. The balloon catheter was deployed and positioned at the ostia of the PVs and a full 8-minute ablation was then performed, while the heart was bathed in a circulating bath of normal saline at 37 degrees. Thermocouples positioned on the endocardial (balloon surface-tissue interface) and epicardial surfaces of the ostia were used to determine whether transmural freezing was achieved. RESULTS: The mean temperatures measured on the endocardial and epicardial tissue in six PV ablations were -38.8 +/- 6.9 degrees C and -10.0 +/- 7.5 degrees C, respectively. The average pulmonary vein thickness was 3.3 +/- 1.4 mm. CONCLUSIONS: A novel cryoablation balloon catheter is capable of achieving transmural freezing of the pulmonary vein. The catheter has promise for future clinical therapy of atrial fibrillation.

Animals↗
PubMed2006

Preserved heart rate variability identifies low-risk patients with nonischemic dilated cardiomyopathy: results from the DEFINITE trial.

BACKGROUND: The recent expansion of indications for prophylactic implantable cardioverter-defibrillator (ICD) placement in subjects with nonischemic dilated cardiomyopathy has raised concerns about the cost-effectiveness of this therapy. OBJECTIVES: The purpose of this study was to identify low-risk patients with nonischemic dilated cardiomyopathy who may not require prophylactic ICD placement. METHODS: This was a prospective study of 274 participants in the Defibrillators in Non-Ischemic Cardiomyopathy Treatment Evaluation (DEFINITE) trial, a randomized controlled trial that evaluated the role of prophylactic ICD placement in patients with nonischemic dilated cardiomyopathy. The patients underwent 24-hour Holter recording for analysis of heart rate variability (HRV). The primary HRV variable was the standard deviation of normal R-R intervals (SDNN). Patients with atrial fibrillation and frequent ventricular ectopy (>25% of beats) were excluded from HRV analysis (23% of patients). SDNN was categorized in tertiles, and Kaplan-Meier analysis was performed to compare survival in the three tertiles and excluded patients. RESULTS: The study population was 73% male, with a mean age of 59 +/- 12 years and mean left ventricular ejection fraction of 21% +/- 6%. After 3-year follow-up, significant differences in mortality rates were observed: SDNN >113 ms: 0 (0%), SDNN 81-113 ms: 5 (7%), SDNN <81 ms: 7 (10%), excluded patients: 11 (17%) (P = .03). There were no deaths in the tertile with SDNN >113 ms regardless of treatment assignment (ICD vs control). CONCLUSION: Patients with nonischemic dilated cardiomyopathy and preserved HRV have an excellent prognosis and may not benefit from prophylactic ICD placement. Patients with severely depressed HRV and patients who are excluded from HRV analysis because of atrial fibrillation and frequent ventricular ectopy have the highest mortality.

Cardiomyopathy, Dilated↗
PubMed2006

Variant angina associated with bitter orange in a dietary supplement.

The Food and Drug Administration has banned the sale of ephedrine-based weight-loss products because of their association with many cardiovascular adverse effects. Bitter orange is now being used as a stimulant in "ephedra-free" weight-loss supplements but was recently implicated in adverse cardiovascular sequelae. To our knowledge, this report describes the first case of variant angina associated with bitter orange in a dietary supplement.

Angina Pectoris, Variant↗
PubMed2005

Effectiveness of automated external defibrillators in high schools in greater Boston.

A program using a strategy of donating a single automatic external defibrillator to 35 schools in the Boston area resulted in compliance with American Heart Association guidelines on automatic external defibrillator placement and training and 2 successful resuscitations from sudden cardiac arrest. Participating schools indicated a high degree of satisfaction with the program.

Adolescent↗
PubMed2005

New-onset ventricular tachycardia after cardiac resynchronization therapy.

It is well established that coronary artery disease with healed myocardial infarction is the most common backdrop for ventricular tachycardia (VT). Although the clinical benefits of biventricular pacing (BivP) in the treatment of severe heart failure are well documented, exact relation with ventricular arrhythmias remains still unclear. We describe a case of a patient, whitout a previous history of arrhythmic episodes, in which the onset of several episodes of VT presented immediatly after cardiac resynchronization therapy (CRT) and did not occur after BivP discontinuation.

Cardiac Pacing, Artificial↗