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Biomedical subjects

N A Estes

Publications and source records attributed to N A Estes.

At least 55 records · Page 3Linked to original sources
PubMed1998

Neonatal radiofrequency catheter ablation of junctional tachycardias.

Junctional tachycardias comprise several arrhythmia types with differing mechanisms, principally involving the region of the atrioventricular (A-V) junction. Neonatal radiofrequency catheter ablation has typically been reserved for life-threatening, drug-refractory cases due to the unique concerns regarding patient size and development. We performed radiofrequency catheter ablation on two neonates with incessant, rapid junctional tachycardias and hemodynamic compromise after failing conventional medical therapy. This report describes 2 neonates who underwent emergent radiofrequency catheter ablation, and compares these two patients to a larger pediatric catheter ablation patient cohort. Both neonates had an acutely successful outcome and were able to be discharged within a week of the ablation procedure. Fluoroscopy time and total procedure time were shorter in these two patients than in the course of the average pediatric catheter ablation. Though long-term developmental consequences of neonatal catheter ablation are yet unknown, in unique extreme situations, radiofrequency catheter ablation can be performed in neonates, as in older children and adults, without excessive acute morbidity.

Adult↗
PubMed1998

Transcoronary ethanol ablation of the atrioventricular node in a young patient with tricuspid atresia.

Catheter ablation of AV conduction with radiofrequency energy can be challenging in the presence of structural abnormalities of the AV junction, either congenitally or after reconstructive surgery. We used transcoronary ethanol to ablate the AV node in a patient with classic tricuspid atresia and refractory intraatrial reentry tachycardia. This approach provides an alternative means of creating complete heart block with catheter-based techniques, when radiofrequency catheter ablation is technically impossible or ineffective.

Adult↗
PubMed1998

Commotio cordis: cardiovascular manifestations of a rare survivor.

Death due to low-energy chest wall trauma, commotio cordis, may occur in young athletes. Death is sudden and usually refractory to even immediate resuscitation efforts. Herein are described the clinical, angiographic, and hemodynamic data of a rare survivor. These observations suggest that commotio cordis not only may be secondary to ventricular fibrillation, but also may be associated with coronary vasospasm or segmental changes in myocardial contractility.

Adolescent↗
PubMed1997

Electrical alternans during rest and exercise as predictors of vulnerability to ventricular arrhythmias.

This investigation was performed to evaluate the feasibility of detecting repolarization alternans with the heart rate elevated with a bicycle exercise protocol. Sensitive spectral signal-processing techniques are able to detect beat-to-beat alternation of the amplitude of the T wave, which is not visible on standard electrocardiogram. Previous animal and human investigations using atrial or ventricular pacing have demonstrated that T-wave alternans is a marker of vulnerability to ventricular arrhythmias. Using a spectral analysis technique incorporating noise reduction signal-processing software, we evaluated electrical alternans at rest and with the heart rate elevated during a bicycle exercise protocol. In this study we defined optimal criteria for electrical alternans to separate patients from those without inducible arrhythmias. Alternans and signal-averaged electrocardiographic results were compared with the results of vulnerability to ventricular arrhythmias as defined by induction of sustained ventricular tachycardia or fibrillation at electrophysiologic evaluation. In 27 patients alternans recorded at rest and with exercise had a sensitivity of 89%, specificity of 75%, and overall clinical accuracy of 80% (p <0.003). In this patient population the signal-averaged electrocardiogram was not a significant predictor of arrhythmia vulnerability. This is the first study to report that repolarization alternans can be detected with heart rate elevated with a bicycle exercise protocol. Alternans measured using this technique is an accurate predictor of arrhythmia inducibility.

Adolescent↗
PubMed1997

Diagnosing syncope. Part 2: Unexplained syncope. Clinical Efficacy Assessment Project of the American College of Physicians.

PURPOSE: To review the literature on diagnostic testing in syncope that remains unexplained after initial clinical assessment. DATA SOURCES: MEDLINE search. STUDY SELECTION: Published papers were selected if they addressed diagnostic testing in syncope, near syncope, or dizziness. DATA EXTRACTION: Studies were identified as population studies, referral studies, or case series. DATA SYNTHESIS: After a thorough history, physical examination, and electrocardiography, the cause of syncope remains undiagnosed in 50% of patients. In such patients, information may be derived from the results of carefully selected diagnostic tests, especially 1) electrophysiologic studies in patients with organic heart disease, 2) Holter monitoring or telemetry in patients known to have or suspected of having heart disease, 3) loop monitoring in patients with frequent events and normal hearts, 4) psychiatric evaluation in patients with frequent events and no injury, and 5) tilt-table testing in patients who have infrequent events or in whom vasovagal syncope is suspected. Hospitalization is indicated for high-risk patients, especially those with known heart disease and elderly patients. CONCLUSIONS: A flexible, focused approach is required to diagnose syncope. Features of the initial history and physical examination help guide diagnostic testing.

Aged↗
PubMed1997

Diagnosing syncope. Part 1: Value of history, physical examination, and electrocardiography. Clinical Efficacy Assessment Project of the American College of Physicians.

PURPOSE: To review the literature on diagnostic testing in syncope and provide recommendations for a comprehensive, cost-effective approach to establishing its cause. DATA SOURCES: Studies were identified through a MEDLINE search (1980 to present) and a manual review of bibliographies of identified articles. STUDY SELECTION: Papers were eligible if they addressed diagnostic testing in syncope or near syncope and reported results for at least 10 patients. DATA EXTRACTION: The usefulness of tests was assessed by calculating diagnostic yield: the number of patients with diagnostically positive test results divided by the number of patients tested or, in the case of monitoring studies, the sum of true-positive and true-negative test results divided by the number of patients tested. DATA SYNTHESIS: Despite the absence of a diagnostic gold standard and the paucity of data from randomized trials, several points emerge. First, history, physical examination, and electrocardiography are the core of the syncope workup (combined diagnostic yield, 50%). Second, neurologic testing is rarely helpful unless additional neurologic signs or symptoms are present (diagnostic yield of electroencephalography, computed tomography, and Doppler ultrasonography, 2% to 6%). Third, patients in whom heart disease is known or suspected or those with exertional syncope are at higher risk for adverse outcomes and should have cardiac testing, including echocardiography, stress testing. Holter monitoring, or intracardiac electrophysiologic studies, alone or in combination (diagnostic yields, 5% to 35%). Fourth, syncope in the elderly often results from polypharmacy and abnormal physiologic responses to daily events. Fifth, long-term loop electrocardiography (diagnostic yield, 25% to 35%) and tilt testing (diagnostic yield < or = 60%) are most useful in patients with recurrent syncope in whom heart disease is not suspected. Sixth, psychiatric evaluation can detect mental disorders associated with syncope in up to 25% of cases. Seventh, hospitalization may be indicated for patients at high risk for cardiac syncope (those with an abnormal electrocardiogram, organic heart disease, chest pain, history of arrhythmia, age > 70 years) or with acute neurologic signs. CONCLUSIONS: Many tests for syncope have a low diagnostic yield. A careful history, physical examination, and electrocardiography will provide a diagnosis or determine whether diagnostic testing is necessary in most patients.

Algorithms↗
PubMed1997

Baseline characteristics of patients in the coronary artery bypass graft (CABG) Patch Trial.

BACKGROUND: Patients with left ventricular dysfunction who undergo coronary artery bypass graft (CABG) surgery frequently have late sudden cardiac death. The CABG Patch Trial is a prospective, randomized, multicenter clinical trial that randomized patients at high risk at the completion of CABG surgery to implantation of an epicardial implantable cardioverter defibrillator (ICD) or to no antiarrhythmic treatment. The trial was designed to determine whether prophylactic implantation of an ICD at the time of CABG surgery would result in a lower total mortality in long-term follow-up. METHODS: Patients undergoing CABG surgery were eligible for the trial if they were younger than 80 years, had a left ventricular ejection fraction less than 0.36, and had an abnormal signal averaged electrocardiogram. Patients with a history of sustained ventricular tachycardia or ventricular fibrillation were excluded from the trial. All patients were scheduled to undergo follow-up at 3-month intervals until 42 months after surgery. RESULTS: Randomization of patients in the trial ended in February 1996. During the recruitment period 71,855 patients were screened, 1,422 were eligible, 1,055 were enrolled (signed consent forms), and 900 patients (76% of eligible patients) were randomized. The mean age of the 446 patients in the ICD group was 64 years versus 63 years for the 454 patients in the control group. A total of 87% of the participants in the ICD group were men versus 82% in the control group (p = NS). Most of the patients had a history of hypertension (55%), smoking (78%), and hypercholesterolemia (54%). Half of the patients had clinical heart failure, and the mean ejection fraction for both patient groups was 0.27 +/- 0.06. No difference was seen in the history of myocardial infarction (83%), congestive heart failure (50%), or atrial (11%) or ventricular (17%) arrhythmias between the two groups. Major clinical characteristics (age, sex, number of previous infarctions, incidence of heart failure, and mean left ventricular ejection fraction) were almost identical to those found in another ICD primary prevention trial, the Multicenter Automatic Defibrillator Implantation Trial (MADIT). CONCLUSIONS: A high risk sample of patients was enrolled in The CABG Patch Trial, as shown by examination of their baseline characteristics.

Adult↗
PubMed1997

High incidence of appropriate implantable cardioverter-defibrillator therapy in patients with syncope of unknown etiology and inducible ventricular arrhythmias.

OBJECTIVES: This study evaluates the hypothesis that in patients with syncope of unknown origin, inducible ventricular arrhythmias are specific arrhythmias and therefore should be appropriately treated. BACKGROUND: Although syncope is a common clinical entity, the evaluation and treatment of patients with syncope without a clear etiology are not well defined. Many patients with syncope of undetermined origin undergo invasive electrophysiologic evaluation. Abnormalities of the sinus node, prolongation of conduction times or inducible arrhythmias found at these evaluations are usually assumed to be the cause of syncope and are therefore treated. However, whether tachyarrhythmias are truly the cause of syncope, and whether treatment of these tachyarrhythmias can prevent recurrent syncope and arrhythmic death, is unknown. METHODS: This study included 50 consecutive patients with syncope of undetermined origin, ventricular tachyarrhythmias at electrophysiologic evaluation and treatment with an implantable cardioverter-defibrillator. RESULTS: Ventricular stimulation led to sustained monomorphic ventricular tachycardia in 36 patients, nonsustained ventricular tachycardia in 5 and ventricular fibrillation in 9. Over a 23 +/- 15-month (mean +/- SD) follow-up period, 18 patients received appropriate implantable cardioverter-defibrillator shock. Actuarial probability of appropriate therapy was 22% at 1 year and 50% at 3 years. Recurrent syncope was seen in five patients, three of whom had appropriate defibrillatory detections at the time of syncope. Four patients died (sudden death in one, congestive heart failure in two). CONCLUSIONS: In patients with syncope of undetermined origin and inducible ventricular tachyarrhythmias, appropriate implantable cardioverter-defibrillator therapy is common at follow-up. Sudden cardiac death is uncommon. This low incidence of sudden cardiac death and high incidence of appropriate defibrillator therapy support the current practice of using implantable cardioverter-defibrillators in patients with syncope of unknown origin and inducible ventricular arrhythmias.

Adult↗
PubMed1997

Combined radiofrequency ablation-cooling catheter for reversible cryothermal mapping and ablation.

Reversible cryothermal mapping of cardiac arrhythmias has been performed intraoperatively. However, a steerable cooling catheter for reversible mapping has not yet been developed. We therefore developed and tested a cooling system consisting of a -15 degrees C hypertonic saline reservoir and a 7F steerable catheter also capable of radiofrequency (RF) ablation. Using excised ovine hearts placed in a 37 degrees C circulating saline bath, we measured the temperatures at depths of 0 mm, 1 mm, and 2 mm. The temperature after 90 seconds of cooling was 16.5 +/- 2.1 degrees C at 0 mm compared to 23.9 +/- 4.1 degrees C at 1 mm and 31.1 +/- 3.9 degrees C at 2 mm depth (p < 0.01). These data suggest that a 7F steerable combined RF ablation-cooling catheter may achieve temperatures suitable for mapping arrhythmias such as atrial tachycardias and right ventricular outflow tract tachycardias. Further enhancements to achieve lower temperatures at depth may be needed to reversibly map other arrhythmias such as left ventricular tachycardias.

Animals↗
PubMed1997

Arrhythmogenic right ventricular dysplasia: clinical results with implantable cardioverter defibrillators.

Arrhythmogenic right ventricular dysplasia is a clinical entity characterized by fatty infiltration of the right ventricle and left bundle morphology ventricular tachycardia occurring in young patients. The most common cause of death is tachyarrhythmic. Pharmacological and nonpharmacological therapies, including implantable cardioverter defibrillators, have been used to treat the arrhythmias. However, right ventricular endocardial leads in this population may be associated with an increased risk of perforation and suboptimal sensing and defibrillation efficacy due to the diseased right ventricle. We report on 12 patients with arrhythmogenic right ventricular dysplasia who were treated with implantable cardioverter defibrillators. The mean age was 31 +/- 9 years (range 15-48). Patients presented with presyncope (5), syncope (4), or cardiac arrest (3). All patients had electrocardiographic abnormalities characteristic of the condition. During programmed electrical stimulation nine patients had sustained ventricular tachycardia, while three patients had no inducible arrhythmia. Transvenous leads were placed in nine patients. In these patients pacing thresholds were significantly higher, R-wave amplitudes were significantly lower and defibrillation thresholds were not significantly different than in a cohort of patients without right ventricular dysplasia. There were no acute or chronic complications of right ventricular lead placement. Follow-up averaged 22 +/- 13 months (range 1-45). There was one sudden death at 1 month of follow-up. Of the 12 patients, 8 have had appropriate therapy delivered by the implantable defibrillator. Six patients are currently on sotalol to reduce the frequency of implantable defibrillator discharges. In conclusion, implantable cardioverter defibrillators with nonthoracotomy leads are feasible and safe in patients with arrhythmogenic right ventricular dysplasia. The frequency of appropriate therapy is high, supporting the use of implantable cardioverter defibrillators in this population.

Adolescent↗
PubMed1997

Pulsing microwave energy: a method to create more uniform myocardial temperature gradients.

Microwave energy has been proposed as a possible technique to create large myocardial lesions. Achieving a uniform myocardial temperature gradient during microwave ablation may prevent excessive endocardial temperatures while maintaining temperatures at depth. The goal of the current study was to examine the ability of microwave (MW) pulsing to achieve a more uniform myocardial temperature gradient. Using an in-vitro ovine endocardial model, we measured tissue temperature at 0.5-mm, 2.0-mm, and 3.5-mm depths in a circulating saline bath. MW energy was delivered at 20 W at 915 MHz for 30 seconds. Pulse configurations of 1 second on-1 second off, 3 seconds on-3 seconds off, and 5 seconds on-5 seconds off, with 30 seconds of total MW time were compared with 30-seconds continuous. Maximum temperatures at 0.5 mm were significantly lower at 63.2 +/- 5.89 degrees C for the 1-second pulse compared with 83.5 +/- 7.31 degrees C for the continuous-energy delivery. Pulse configurations 3 seconds on-3 seconds off and 5 seconds on-5 seconds off also resulted in a significantly lower surface temperature than continuous-energy delivery. However, temperature at the 2.0-mm and 3.5-mm depth created by the pulsing delivery were similar to those achieved during continuous-energy delivery. Thus, microwave pulsing achieves a lower endocardial temperature and results in a more uniform temperature gradient. These techniques may prevent the excessive endocardial damage that may result in an increased risk of thrombus formation and embolization.

Animals↗
PubMed1996

Perioperative and long-term results with mapping-guided subendocardial resection and left ventricular endoaneurysmorrhaphy.

BACKGROUND: Surgical ablation of the arrhythmogenic focus in patients with life-threatening ventricular tachyarrhythmias can be curative. However, the surgical techniques have been plagued by a high perioperative mortality rate (averaging approximately 12%). Reconstruction of the left ventricle may reduce mortality. METHODS AND RESULTS: Reconstruction of the left ventricle with a pericardial patch, or endoaneurysmorrhaphy, was performed with mapping-guided subendocardial resection for recurrent ventricular tachycardia in 25 patients over a 5-year period. Postoperatively, electrophysiological studies were conducted to assess the results of surgery, which were further evaluated during long-term follow-up with survival analyses. The study included 25 patients, 60 +/- 9 years of age, with coronary artery disease, discrete left ventricle aneurysms, and malignant ventricular tacharrhythmias. Left ventricular ejection fraction was 24 +/- 6% preoperatively. Left ventricular endocardial mapping, endocardial resection, and endoaneurysmorrhaphy were performed in all patients. There was no operative or postoperative (30-day) mortality. Postoperative ventricular tachycardia was induced in 2 of the 25 patients (8%); left ventricular function increased to 32 +/- 9% (range, 19% to 52%). At a mean follow-up of 37 +/- 16 months (range, 6 to 65 months), there had been 6 deaths, including 1 sudden cardiac death, 2 congestive heart failure deaths, and 3 noncardiac deaths. Analysis of multiple variables failed to identify predictors of postoperative inducibility, sudden cardiac death, cardiac death, or total mortality. CONCLUSIONS: Endoaneurysmorrhaphy with a pericardial patch combined with mapping-guided subendocardial resection frequently cures recurrent ventricular tachycardia with low operative mortality and improvement of ventricular function. Long-term follow-up demonstrates low sudden cardiac death rates.

Aged↗
PubMed1996

Atrioventricular junctional ablation and modification for atrial fibrillation.

RF catheter ablation is a safe and extremely effective method of achieving complete A-V block in patients with difficult-to-control ventricular rates in atrial fibrillation. In selected patients, A-V junction ablation may improve exercise capacity and functional status while reducing the need for emergency care and hospitalization. Prospective, randomized studies are needed, however, to compare A-V junction ablation as a management strategy to pharmacologic therapy to control ventricular rate or to maintain sinus rhythm. Similarly, additional data are needed to assess methods of achieving A-V junction modification with the lowest risk for A-V block.

Atrial Fibrillation↗