PubMed Health⌕ Search

Biomedical subjects

R D Fletcher

Publications and source records attributed to R D Fletcher.

At least 19 recordsLinked to original sources
PubMed1992

Catheter ablation of hemodynamically compromising incessant atrioventricular tachycardia.

A 27-year-old woman was admitted to the Georgetown University Hospital with refractory hemodynamically compromising incessant atrioventricular tachycardia. A single left-sided accessory pathway was identified and successfully modified acutely. Endocardial delivery of direct current energy provided an extremely effective therapeutic intervention resulting in termination of atrioventricular tachycardia and restoration of stable hemodynamic status. Although a second ablation procedure was necessary to permanently interrupt accessory pathway conduction, the patient has remained free of symptoms without medications for 13 months.

Adult↗
PubMed1992

Congestive heart failure: survival trial of antiarrhythmic therapy (CHF STAT). The CHF STAT Investigators.

This study is a prospective, double-masked, randomized, clinical trial to determine the effect of anti-arrhythmic drug therapy on mortality in patients with congestive heart failure and ventricular arrhythmia. Patients will be assigned to receive either amiodarone or placebo. Eligible patients include those with ischemic and nonischemic congestive heart failure (New York Heart Association class III or VI) and with 10 or more ventricular premature beats per hour. All patients must have shortness of breath with minimal exertion or paroxysmal nocturnal dyspnea, a left ventricular internal dimension (LVIDd) by echocardiogram of 55 mm or greater (> or = 55 mm) or a CT ratio of greater than 0.5, and an ejection fraction of 40% of less. Patients will be entered into the study for 2.5 years and followed for an additional 2 years. Drug therapy will be continued for all patients throughout the entire study unless adverse reactions occur that necessitate individualized treatment. The expectation is that 674 patients are to be entered into the study from 25 participating centers. This sample size will allow for the detection of a 33% decrease in 2-year mortality (20% vs. 30%) in the treated patients as compared to those in the placebo group with a power of 0.90 and a two-sided alpha level of 0.05. Intermittent Holter monitoring, radionuclide ventriculograms, pulmonary function tests, echocardiograms, and blood tests, including arterial blood gases, will be required for each patient. The study analysis will address differences in total mortality, cardiac mortality, and sudden cardiac death between patients receiving anti-arrhythmic drug therapy and those receiving placebo. Other factors to be examined include the effects of antiarrhythmic therapy on suppression of arrhythmias, on ejection fraction, and relation of ischemic events to mortality.

Amiodarone↗
PubMed1991

Ventricular late potentials in myotonic dystrophy.

OBJECTIVE: To determine the prevalence of ventricular late potentials, as determined by signal-averaged electrocardiography, in patients with myotonic dystrophy. DESIGN: Cross sectional, with blinded analysis of all electrocardiographic data. SETTING: Outpatient departments of a Veterans Affairs medical center and a tertiary care private hospital. PARTICIPANTS: Twenty-four patients with myotonic dystrophy. Patients were excluded from the study if they had either a history suggestive of significant ventricular arrhythmias or electrocardiographic evidence of a bundle-branch block. Two comparison groups were also formed; one group included 44 healthy employees at the tertiary hospital and the other, 30 cardiac patients with inducible ventricular tachycardia. MAIN RESULTS: A time-domain analysis of the signal-averaged electrocardiograms showed that 75% of patients with myotonic dystrophy met one criterion for the presence of late potentials, 67% met two criteria, and 29% met all three criteria. Spectrotemporal mapping in these patients showed markedly abnormal spectral peaks with a mean factor of normality that was significantly lower than that of the normal volunteers; the frequency of electrocardiographic abnormalities approached that seen in patients with known ventricular tachycardia. The presence of late potentials correlated directly with the length of the PR interval and inversely with left ventricular fractional shortening. CONCLUSIONS: In our study, the prevalence of late potentials on signal-averaged electrocardiography in patients with myotonic dystrophy approached that seen in cardiac patients with inducible ventricular tachycardia. It is possible that ventricular arrhythmias play a role in the occurrence of sudden death in some patients with myotonic dystrophy.

Adult↗
PubMed1991

Sudden cardiac death after myocardial infarction.

Recent advances in the understanding of the mechanisms of sudden cardiac death have been paralleled by technical advances in diagnosis and treatment, involving ambulatory Holter monitoring and the use of implantable defibrillators. Risk factors predisposing toward sudden cardiac death in the postmyocardial infarction setting and in patients with congestive heart failure include the presence of ventricular ectopy [greater than 10 premature ventricular contractions (PVC) per hour], frequent episodes of ventricular pairs and nonsustained ventricular tachycardia on 24-hour Holter monitoring, and a depressed left ventricular ejection fraction. Additional risk factors for sudden cardiac death in coronary artery disease include arterial stenosis in coronary vessels supplying intact myocardium remote from the infarction site, the presence of late potentials on the signal averaged ECG, and attenuation of the normal variation in heart rate. The ability to induce sustained ventricular tachycardia (SVT) on electrophysiological testing is highly predictive of sudden cardiac death after myocardial infarction. Conversely, the ease of suppression of the induced tachycardia with antiarrhythmic agents is correlated with the risk of subsequent lethal ventricular arrhythmia. The detrimental effect of frequent ventricular ectopy (greater than 10 PVC/h) on survival in coronary artery disease is particularly pronounced in patients with moderately well preserved left ventricular function [ejection fraction (EF) greater than 30%], thereby suggesting that these patients may be better served by antiarrhythmic therapy than those with severely depressed left ventricular function.(ABSTRACT TRUNCATED AT 250 WORDS)

Death, Sudden↗
PubMed1991

Providing an integrated clinical data view in a hospital information system that manages multimedia data.

The VA's hospital information system, the Decentralized Hospital Computer Program (DHCP), is an integrated system based on a powerful set of software tools with shared data accessible from any of its application modules. It includes many functionally specific application subsystems such as laboratory, pharmacy, radiology, and dietetics. Physicians need applications that cross these application boundaries to provide useful and convenient patient data. One of these multi-specialty applications, the DHCP Imaging System, integrates multimedia data to provide clinicians with comprehensive patient-oriented information. User requirements for cross-disciplinary image access can be studied to define needs for similar text data access. Integration approaches must be evaluated both for their ability to deliver patient-oriented text data rapidly and their ability to integrate multimedia data objects. Several potential integration approaches are described as they relate to the DHCP Imaging System.

Computer Communication Networks↗
PubMed1990

Left ventricular hypertrophy in men with normal blood pressure: relation to exaggerated blood pressure response to exercise.

OBJECTIVE: To determine whether normal, nonhypertensive subjects who have unusually large increases of systolic blood pressure with exercise have left ventricular hypertrophy (LVH). DESIGN: Case-comparison using echocardiography as a criterion standard for measurement of left ventricular mass and the diagnosis of LVH. SETTING: Population-based health fitness screening program and referral Veterans Affairs Hospital. SUBJECTS: Thirty-nine men (average age, 44.6 +/- 8.5 years; range, 34 to 71 years) were studied, including 25 participants in a health fitness screening program and an additional 14 normal men with atypical chest pain. Twenty-two subjects with a systolic blood pressure during peak exercise of 210 mm Hg or greater were compared with 17 others with systolic pressure less than 210 mm Hg during exercise. MEASUREMENTS AND MAIN RESULTS: Left ventricular hypertrophy (left ventricular mass index greater than 134 g/m2) was found in 14 of 22 men with a systolic blood pressure of 210 mm Hg or greater (present in 6.3% of normotensive healthy male volunteers in a health screening program) but in only 1 person with a lower exercise blood pressure. Left ventricular mass index was linearly correlated (r = 0.65, n = 39, P less than 0.001) with maximum exercise blood pressure. Whereas LVH was mild in about 50%, substantial LVH was present in the others. The presence of LVH was not related to superior physical conditioning and was accompanied by increased left atrial size suggesting impaired left ventricular filling. CONCLUSIONS: Even in the absence of hypertension, exaggerated blood pressure responses during exercise testing suggest a probability of 0.64 (95% CI, 0.41 to 0.83) of LVH, a finding associated with the cardiac "end-organ" manifestations of hypertension.

Adult↗
PubMed1989

Effects of diuretic therapy and exercise-related arrhythmias in systemic hypertension.

The effect of aerobic exercise on cardiac arrhythmias, plasma catecholamines, potassium and magnesium in patients with systemic hypertension was assessed. Twenty patients (age 54 +/- 8 years) with uncomplicated hypertension underwent exercise treadmill testing twice while receiving placebo and twice while receiving hydrochlorothiazide 100 mg daily. Blood samples for electrolytes and catecholamines were obtained at rest, at peak exercise and 10 minutes after exercise. There were no substantial differences comparing the first to the second placebo phase or the first to the second treatment period. As expected, hydrochlorothiazide treatment caused a significant decrease in serum potassium (4.00 +/- 0.44 to 3.32 +/- 0.49 mEq/liter, p less than 0.001). Serum magnesium did not change with treatment. Serum potassium, serum magnesium and plasma catecholamines increased significantly with exercise. No rebound hypokalemia occurred during recovery. Occasional ventricular premature contractions were noted at rest during all phases of the study, with only a slight increase in frequency during exercise. Couplets were noted only rarely. No difference in the frequency or complexity of arrhythmias was noted between placebo and treatment periods. Diuretic therapy or diuretic-induced hypokalemia has no profound effect on cardiac arrhythmias during or after exercise in patients with uncomplicated systemic hypertension.

Blood Pressure↗
PubMed1989

Transdiaphragmatic implantation of the automatic implantable cardioverter defibrillator.

A new surgical approach for implantation of the automatic implantable cardioverter defibrillator without thoracotomy was used in 12 patients, aged 46 to 72 years. Preimplantation arrhythmia was ventricular tachycardia in 7 patients and ventricular fibrillation in 5 patients. The mean ejection fraction was 19%. Six patients were at high risk for general anesthesia for a variety of medical problems, and 2 patients had had a previous cardiac operation. Epidural anesthesia was used in 8 patients without intubation. The surgical approach used a longitudinal epigastric extraperitoneal incision with access to the heart through an incision made in the central tendon of the diaphragm. Two patches and two epicardial sensing leads were placed in all patients. All patients but one could be defibrillated with 20 J or less. There was no operative mortality and minimal morbidity. There were two late deaths due to heart failure. Thus, the transdiaphragmatic approach provides an excellent exposure for automatic implantable cardioverter defibrillator implantation, avoids general anesthesia and thoracotomy, and can be used after a previous cardiac operation.

Aged↗
PubMed1988

Sotalol for refractory sustained ventricular tachycardia and nonfatal cardiac arrest.

The efficacy and safety of sotalol were assessed by electrophysiologic testing and ambulatory recordings in 16 patients with recurrent sustained ventricular tachycardia (VT) or nonfatal cardiac arrest who were refractory to an average of 4.8 conventional antiarrhythmic agents. Twenty-four-hour ambulatory recordings were performed before and after sotalol therapy. Fourteen patients underwent baseline electrophysiologic study and sustained VT was inducible in 12. Oral sotalol (320 to 960 mg/day) completely suppressed inducible sustained VT in 7 patients (58%), with modification in 3 (25%). Ventricular premature complexes were suppressed from baseline (mean +/- standard deviation) 431 +/- 616 to 60 +/- 110/hr (p less than 0.03). After a mean follow-up of 19 +/- 7 months, 12 of 14 patients receiving sotalol treatment had successful suppression of ventricular premature complexes (60 +/- 85/hr) and remained clinically free of sustained VT, except 2 who needed additional antiarrhythmic drugs to suppress the recurrent sustained VT. One patient died suddenly after 25 months of sotalol treatment. No severe side effects were noted during sotalol therapy. This study demonstrates that sotalol is a well-tolerated, effective antiarrhythmic agent in patients at high-risk for sudden death. It appears to be beneficial in patients who did not benefit from multiple drug treatment.

Adult↗
PubMed1988

Serial electrocardiographic changes in idiopathic dilated cardiomyopathy confirmed at necropsy.

Serial electrocardiographic changes in necropsy-proven idiopathic dilated cardiomyopathy are evaluated and a method of predicting heart weight using QRS amplitudes is described. In 34 patients with multiple electrocardiograms (mean 3/patient) progressive prolongation of PR interval (0.18 +/- 0.03 to 0.21 +/- 0.03, p less than 0.001) and QRS duration (0.10 +/- 0.02 to 0.13 +/- 0.03, p less than 0.0001) was noted. Progressive conduction abnormalities were common (82%). QTc interval and QRS- and T-wave axes did not change. In 50 patients with electrocardiograms within 60 days of death, total 12-lead QRS and V1 through V6 QRS amplitude correlated better with heart weight (r = 0.51, p less than 0.0001 and r = 0.55, p less than 0.0001) than the Estes-Romhilt score did. The mean total 12-lead QRS amplitude was 138 mm with a mean of 106 for V1 through V6. In 31 patients cardiac mass index was calculated and showed significant correlation with 12-lead and V1 through V6 QRS amplitudes (r = 0.68, p less than 0.0001 and r = 0.75, p less than 0.0001, respectively). The QRS amplitudes remained constant during the illness. By using total 12-lead QRS or frontal plane QRS amplitude, heart weight can be predicted as early as 2 years before death. Use of body surface area and QRS amplitude criteria increases the accuracy of heart weight prediction. Thus, progressive electrocardiographic changes are common in patients with idiopathic dilated cardiomyopathy and QRS amplitude criteria are more accurate in the prediction of left ventricular hypertrophy than standard criteria.

Adolescent↗
PubMed1988

M-mode echocardiograms for determination of optimal left atrial timing in patients with dual chamber pacemakers.

To determine if the A wave of the mitral valve echocardiogram can be used as a marker for left atrial (LA) activity and assist in the programming of dual chamber pacemakers, 156 echocardiograms with the mitral A wave present were obtained from 23 patients with dual chamber pacemakers, all of whom had bipolar esophageal recordings of LA depolarization. Twelve of these patients also underwent hemodynamic study with cardiac function determined at 5 different pacemaker settings: ventricular demand pacing and dual chamber sequential pacing at 0 or 25, 150, 200 and 250 ms programming atrioventricular (AV) delay. The time delay from right atrial pacing artifact to onset and peak of mitral A wave was linearly related to the time from atrial pacing artifact to LA depolarization on the esophageal lead (p less than 0.001). As pacing mode changed from dual chamber sequential pacing (DVI) mode to atrial synchronous-ventricular pacing (VDD), the A wave came earlier relative to the ventricular pacing spike, linearly related to the LA to ventricular extension with mode change determined with the esophageal lead (r = 0.94, p less than 0.001). The time from atrial pacing to peak of A wave was shorter in patients whose optimal programmed AV delay was 150 ms compared with those whose optimal AV delay was 200 or 250 ms (p less than 0.02). At the optimal programmed delay for cardiac output, the peak of the A wave was an average of 13 +/- 36 ms after the ventricular pacing spike.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

The use and interaction of permanent pacemakers and the automatic implantable cardioverter defibrillator.

The adverse interactions of permanent pacemakers and automatic implantable cardioverter defibrillators (AICD) were studied in nine patients in whom both devices were implanted. Both unipolar and bipolar pacemakers were evaluated. The permanent pacemakers were also used to do noninvasive electrophysiological studies and to induce ventricular fibrillation. Undersensing of ventricular fibrillation by the permanent pacemakers caused inappropriate pacemaker stimuli, which caused undersensing of ventricular fibrillation by the AICD in three of four patients with unipolar pacemakers. After an AICD discharge, pacemaker noncapture was seen in eight of 22 episodes for an average 4.9 seconds and inability to sense was seen in 11 of 20 episodes for an average 9.0 seconds. Counting of pacemaker stimuli and QRS by the AICD caused inappropriate discharges. Noninvasive electrophysiological testing by the pacemakers correlated with invasive testing. Furthermore, induction of ventricular fibrillation was successful in four of five patients attempted, though requiring long bursts at high outputs at the shortest cycle lengths obtainable by these pacemakers. Operation of the AICD and permanent pacemakers must be clearly understood to avoid adverse interactions of these devices.

Electric Countershock↗
PubMed1988

Thiazide therapy is not a cause of arrhythmia in patients with systemic hypertension.

Forty-four patients with uncomplicated systemic hypertension underwent 48-hour electrocardiographic monitoring before and after four weeks of treatment with hydrochlorothiazide, 100 mg daily. Plasma potassium concentration decreased from 4.07 +/- 0.26 mmol/L (4.07 +/- 0.26 mEq/L) to 3.36 +/- 0.44 mmol/L (3.36 +/- 0.44 mEq/L). The average number of premature ventricular contractions, couplets, or ventricular tachycardia episodes did not change significantly. Twenty patients had more than minimal ventricular ectopy (class 2 to 5) before and 17 after diuretic therapy. Further analysis revealed that following diuretic therapy, neither patients with plasma potassium levels of 3.4 mmol/L or less (less than or equal to 3.4 mEq/L) nor patients with left ventricular hypertrophy had increased ectopy as compared with baseline. At baseline, patients with left ventricular hypertrophy had more arrhythmias than patients without. We conclude that the results of this study provide no evidence that diuretic therapy or diuretic-induced hypokalemia results in increased ventricular ectopy, and that patients with left ventricular hypertrophy may have more ventricular ectopy than patients without, but these arrhythmias are not adversely effected by diuretic therapy.

Cardiac Complexes, Premature↗
PubMed1987

The NASPE/BPEG generic pacemaker code for antibradyarrhythmia and adaptive-rate pacing and antitachyarrhythmia devices.

A new generic pacemaker code, derived from and compatible with the Revised ICHD Code, was proposed jointly by the North American Society of Pacing and Electrophysiology (NASPE) Mode Code Committee and the British Pacing and Electrophysiology Group (BPEG), and has been adopted by the NASPE Board of Trustees. It is abbreviated as the NBG (for "NASPE/BPEG Generic") Code, and was developed to permit extension of the generic-code concept to pacemakers whose escape rate is continuously controlled by monitoring some physiologic variable, rather than determined by fixed escape intervals measured from stimuli or sensed depolarizations, and to antitachyarrhythmia devices including cardioverters and defibrillators. The NASPE/BPEG Code incorporates an "R" in the fourth position to signify rate modulation (adaptive-rate pacing), and one of four letters in the fifth position to indicate the presence of antitachyarrhythmia-pacing capability or of cardioversion or defibrillation functions.

Bradycardia↗
PubMed1987

Viadent, ethanol, and pH effects upon gingival epithelial-like cells, in vitro.

Interest has recently been directed towards the use of antiplaque mouthrinses. Most published material concerns the antimicrobial effects of these agents rather than their effects upon oral tissue. This study was conducted to evaluate the effect of a sanguinarine-containing mouthrinse called Viadent upon epithelial-like gingival cells. The cells were grown for 24 hours in supplemented Earle's medium, with and without different Viadent dilutions. Cell counts were made with a hematocytometer. It was found that 50% of the cells were inhibited at 1.2% Viadent. In similar studies, it was found that 70% ethanol and two pH buffers were less toxic than Viadent. Exposure of preformed cell monolayers to Viadent also showed significant inhibition. The relative toxicity of different antiplaque agents may be compared using such cells as a model system. In conclusion, it was observed that Viadent significantly affected gingival cell growth in vitro, that viable cell numbers were greatly reduced by short time exposure, and that the toxic effect of Viadent could only partially be accounted for by ethanol content and/or pH.

Adult↗