Search PubMed⌕ Search

Biomedical subjects

R D Fletcher

Publications and source records attributed to R D Fletcher.

At least 73 records · Page 4Linked to original sources
PubMed1986

Supraventricular tachycardia emergencies: diagnosis and management.

A variety of acute supraventricular tachycardias may be encountered. In many instances the therapies for these rhythm disturbances overlap, but a rational approach to individual disturbances should be based on an understanding of the anatomy and physiology involved in the individual dysrhythmia. Numerous investigative approaches are underway at present, especially with regard to interruption of arrhythmia pathways by electroshock therapy or surgical therapy. In addition, pacing overdrive may be very effective, especially in patients with reentrant arrhythmias.

Atrial Fibrillation↗
PubMed1986

Cardiac pacemaker emergencies.

Each component of a pacemaker system is a potential weak link in the pacing chain. Whether or not pacing failure is caused by battery depletion or by electrode fracture, these malfunctions can be diagnosed with the help of intermittent and regular transtelephonic surveillance. Sufficiently large numbers of patients enrolled in such surveillance systems enable the early identification of faulty pacers and leads and alert the medical community against their use. Indeed, the pacemaker surveillance systems in operation at present form the cornerstone of defense against pacemaker malfunction emergencies.

Electrodes↗
PubMed1985

Echocardiographic assessment by computer-assisted analysis of diastolic left ventricular function and hypertrophy in borderline or mild systemic hypertension.

Systemic hypertension is a common cause of congestive heart failure. However, left ventricular (LV) systolic function remains normal for many years in patients with mild or moderate hypertension. In this study, high-quality M-mode echocardiograms were recorded in 7 patients with borderline hypertension, 14 patients with mild hypertension and 15 normal persons. Measures of systolic and diastolic LV function and the degree of LV hypertrophy were studied with the assistance of a tablet digitizer and dedicated microcomputer. Average blood pressure was 125 +/- 10/77 +/- 7 mm Hg in normal subjects, 146 +/- 18/92 +/- 2 mm Hg in patients with borderline hypertension and 150 +/- 11/102 +/- 4 in patients with mild hypertension. Indexes of systolic LV function were similar in all 3 groups. The peak rate of early relaxation of the LV posterior wall was significantly decreased in the group of patients with mild hypertension (4.7 vs 6.6 sec-1, p less than 0.01). The mitral valve closure rate was 150 +/- 32 mm/s in normal subjects, 119 +/- 35 mm/s in patients with borderline hypertension and 106 +/- 26 mm/s (p less than 0.001) in patients with mild hypertension. Mild LV hypertrophy was present in 6 of 7 patients with borderline and 13 of 14 patients with mild hypertension. The degree of hypertrophy and the level of blood pressure correlated poorly.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Effect of diuretic therapy on ventricular arrhythmias in hypertensive patients with or without left ventricular hypertrophy.

Recent studies have suggested that hypertensive patients with ECG evidence of left ventricular hypertrophy (LVH) may have increased risk of sudden death when treated with diuretics. In the present study echocardiography was used as a more sensitive index for the presence of LVH. Thirty-one patients with uncomplicated hypertension underwent 48-hour ambulatory ECG monitoring both before any treatment and after 4 weeks of hydrochlorothiazide, (HCTZ), 100 mg daily. In 18 patients with left ventricular posterior wall thickness (LVPWT) greater than or equal to 13 mm (average = 14.4 +/- 0.2 mm) on echocardiogram, plasma potassium decreased from 4.1 +/- 0.3 to 3.3 +/- 0.4 mEq/L with HCTZ (p less than 0.01). Premature ventricular contractions (PVCs) averaged 5.7 +/- 9.9/hr at baseline and 7.1 +/- 16.6/hr following HCTZ (p = NS). The total number of couplets was 29 before and 13 after HCTZ, while four brief runs of ventricular tachycardia occurred only before treatment. In the remaining 13 patients with LVPWT less than or equal to 12 mm (average = 11.2 +/- 0.1 mm), plasma potassium decreased from 4.1 +/- 0.3 to 3.4 +/- 0.5 mEq/L with HCTZ (p less than 0.01). The average number of PVCs was 4.3 +/- 8.0/hr after HCTZ (p = NS). One couplet and one 3-beat run of ventricular tachycardia occurred before and one 3-beat run of ventricular tachycardia after HCTZ. Although more complex arrhythmias were noted in the LVH group, the differences were not statistically significant. These results indicate that thiazide therapy does not increase ventricular arrhythmias either in patients with or without LVH.

Adult↗
PubMed1985

Effect of acebutolol on left ventricular performance.

The effect of acebutolol on left ventricular performance was examined by various noninvasive means in three studies. M-mode echocardiographic measurements were made in 21 patients with coronary artery disease who were receiving placebo, acebutolol, and propranolol in a double-blind, randomized, crossover study. In these patients with normal or near-normal resting left ventricular function, neither drug induced depression of left ventricular function. In 26 patients with chronic angina pectoris receiving acebutolol under double-blind, placebo-controlled conditions, gated (equilibrium) myocardial blood pool imaging using red blood cells labeled with technetium 99m showed acebutolol to have no clinically significant negative effect on left ventricular performance at rest or during supine bicycle exercise. Acebutolol at effective antianginal doses modestly improved resting global and regional myocardial function. In 13 patients with stable angina pectoris, single-pass studies of left ventricular function with indium 113 under double-blind, placebo-controlled conditions similarly showed acebutolol to have no clinically significant negative inotropic effects. In conclusion, acebutolol is safe for use in patients with coronary disease and a wide range of ejection fractions but, as with all beta blockers, should be used cautiously in patients with markedly reduced resting left ventricular function.

Acebutolol↗
PubMed1985

Increased right ventricular wall thickness in left ventricular pressure overload: echocardiographic determination of hypertrophic response of the "nonstressed" ventricle.

Left ventricular hypertrophy in left ventricular pressure overload occurs in response to excessive work load imposed on the left ventricle by increased impedance to ejection. Right ventricular hypertrophy may occur in patients with these findings, but has been considered to be secondary to pulmonary hypertension. To determine the frequency of right ventricular hypertrophy and its relation to increased left ventricular wall thickness in patients with left ventricular pressure overload, right ventricular wall thickness was measured using M-mode echocardiography with two-dimensional echocardiographic guidance in 65 patients with left ventricular pressure overload; 49 patients had essential hypertension and 16 had aortic valve stenosis. These measurements were compared with data from 13 patients with "thin-walled" dilated cardiomyopathy and 20 normal subjects. Average right ventricular wall thickness in hypertensive patients (7 +/- 2 mm) and patients with aortic stenosis (6 +/- 2 mm) was significantly greater than that in normal subjects (4 +/- 1 mm) and patients with dilated cardiomyopathy (4 +/- 1 mm) who had normal left ventricular wall thickness, even though left ventricular mass was increased in all patient groups. Increased right ventricular wall thickness was present in 40 (80%) of 49 patients with hypertension and 10 (63%) of 16 patients with aortic stenosis. The magnitude of increase in right ventricular wall thickness was linearly correlated (r = 0.76, p less than 0.005) with left ventricular wall thickness, but was not associated with pulmonary hypertension. It is concluded that increased right ventricular wall thickness is common in patients with left ventricular pressure overload, is directly related to increases in left ventricular wall thickness, and is independent of right ventricular hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Inhibition of a physiologic pacing system due to its anti-pacemaker-mediated tachycardia mode.

Newer programmable DDD pacemakers prevent pacemaker-mediated tachycardia by automatic extension of the atrial refractory period after a detected premature ventricular contraction. We present an example in which the automatic extension of the atrial refractory period resulted in pacemaker inhibition, which should not automatically be assumed to represent pacemaker malfunction. A careful understanding of pacemaker timing intervals may allow for identification and correction of this problem.

Cardiac Pacing, Artificial↗
PubMed1985

Transcatheter ablation: comparison between laser photoablation and electrode shock ablation in the dog.

To characterize and compare the effects of transcatheter laser and electrical energy on endocardium, 35 laser pulses were delivered to the endocardial surfaces of isolated canine hearts, and 33 endocardial lesions were produced by the transarterial delivery of either transcatheter laser irradiation or electrical shock in closed-chest anesthetized dogs. Laser-induced lesion dimensions in vitro and in vivo increased with increased total dose of energy; however, the lesions produced in vivo were different in morphology and were significantly larger than lesions produced by equivalent doses of energy delivered in vitro (p less than .05). Endocardial lesions produced in vivo by laser at 40 and 80 J (7.9 X 5.4 X 6.6 and 7.9 X 5.1 X 7.5 mm) were comparable in gross morphology and size to those produced by electrical shock at 100 and 200 J (8.5 X 6.6 X 6.6 and 10.0 X 8.5 X 8.2 mm, respectively; p = NS), but transcatheter electrode shock produced significantly more ventricular tachycardia (p less than .003), premature ventricular beats in the 7 min after energy discharge (p less than .05), and wall motion abnormality (p less than .005). Transcatheter laser photoablation can create controlled endocardial lesions with less energy and fewer deleterious effects than transcatheter electrode shock.

Animals↗
PubMed1984

Lorcainide for high-frequency ventricular arrhythmia: preliminary results of a short-term double-blind and placebo-controlled crossover study and long-term follow-up.

Lorcainide, 100 mg twice daily was compared with placebo in 39 patients with frequent ventricular arrhythmias in a randomized double-blind crossover trial. A mean frequency of ventricular premature beats (VPBs) of at least 30 VPBs/hour was required during a drug-free period of 48 hours. Holter monitoring and a maximal symptom-limited exercise test were performed at the end of each of the 2-week double-blind treatment phase. The group averaged 350 +/- 361 (standard deviation) VPBs/hour. Lorcainide decreased the mean VPB frequency of the group by 46% (p less than 0.01), with VPB reduction beyond the expected variation in 22 of 39 patients. In 13 patients VPBs were unchanged and in 4 they increased. Eight additional patients responded during drug titration, for an overall response rate of 77% (30 of 39). Lorcainide did not significantly reduce the exercise-related VPB frequency. At 6 months 61% of patients had significant VPB suppression. Thus, lorcainide was effective in reducing the frequency and grade of spontaneous ventricular arrhythmias during short- and long-term evaluation.

Adult↗
PubMed1984

Effect of moricizine hydrochloride in reducing chronic high-frequency ventricular arrhythmia: results of a prospective, controlled trial.

The antiarrhythmic efficacy of moracizin HCl (Ethmozine), a new oral phenothiazine derivative, was evaluated in 20 patients with chronic high-frequency ventricular arrhythmia confirmed by multiple ambulatory electrocardiographic recordings. Comparison with 72 +/- 24 hours (+/- standard deviation) of ambulatory recordings on moracizin treatment (average dose 295 +/- 58 mg 3 times daily or 9.8 +/- 1.0 mg/kg/day) was made. Maximal treadmill exercise provocation of arrhythmia and echocardiographic studies to detect effects on left ventricular function were also compared. The group had an average of 378 +/- 97 ventricular premature beats (VPBs) per hour while receiving placebo, with a mean VPB grade of 3.4 +/- 1.1 (modified Lown). When the patients received moracizin HCl, VPB frequency was reduced 53% (p less than 0.01), to a mean VPB grade of 2.2 +/- 1.4 (p less than 0.05). Seventy percent of the patients (14 of 20) showed a reduction in VPB frequency that exceeded the maximal expected variation; in 3 the frequency did not change and in 3 it increased with moracizin HCl. Resting electrocardiographic changes consisted of modest prolongations of PR interval (0.03 second) and QRS duration (0.02 second); however, QT prolongation was not observed. Heart rate and blood pressure at rest and peak exercise, exercise-related arrhythmia, exercise durations and echocardiographic measures of left ventricular function were unchanged by moracizin HCl compared with placebo. Side effects of moracizin++ HCl at these dosages were minimal (diarrhea in 1 patient, dizziness in 1 and diaphoresis in 1), although 2 patients tested at higher dosages had sustained ventricular tachycardia that may have been related to moracizin HCl.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Frequency and embolic potential of left ventricular thrombus in dilated cardiomyopathy: assessment by 2-dimensional echocardiography.

Left ventricular (LV) thrombus at autopsy and systemic emboli during life have been frequent findings in patients with dilated cardiomyopathy. Since anticoagulation has substantial risk, noninvasive identification of those patients likely to have emboli is important. Therefore, wide-angle 2-dimensional (2-D) echocardiograms in 123 patients (average age 56 +/- 6 years) with chronic dilated cardiomyopathy were analyzed for the presence of LV thrombus; these findings were compared with the clinical course in 96 patients. On 2-D echocardiography, thrombus was present in 44 patients (36%). Events compatible with systemic emboli occurred in 11 patients (11%), and were not more frequent in those patients with than in those without LV thrombus. In addition, neither the presence of thrombus nor the frequency of systemic emboli differed between patients with and those without associated coronary artery disease. Thus, although 2-D echocardiography shows a high frequency of LV thrombus in patients with dilated cardiomyopathy irrespective of the presence of coronary artery disease, clinical events compatible with systemic emboli are not more frequent in those with than those without LV thrombus.

Adult↗
PubMed1983

Effects of disopyramide on left ventricular function: assessment by radionuclide cineangiography.

To determine the effects of disopyramide on resting systolic left ventricular (LV) function and LV functional reserve, gated equilibrium radionuclide cineangiography was performed at rest and during maximal symptom-limited supine bicycle exercise in 12 patients after a single 300 mg oral loading dose of disopyramide, and in 22 patients (including the 12 patients just mentioned) after they received disopyramide 150 mg 4 times daily for 5 to 10 days (average 7). The oral loading dose (average serum level 3.6 +/- 1.3 micrograms/ml [standard deviation] produced decreases in ejection fraction in 9 of 12 patients with a decrease in average resting ejection fraction from 40 +/- 15% to 33 +/- 11% (p less than 0.005). However, the lower, sustained dosage of disopyramide was associated with a lower average serum level of 2.5 +/- 0.8 micrograms/ml and with smaller but significant decreases in ejection fraction in 3 of 22 patients during exercise only. At this dosage there was no significant decrease in average ejection fraction for the group at rest or during exercise. Adverse effects of disopyramide on ejection fraction occurred even in patients with previously normal LV function at rest. Hence, disopyramide may be associated with significant decreases in LV systolic function, particularly when given in high, oral "loading" doses. However, sustained therapy with lower dosages as well as lower drug levels is also associated with less depression of LV function.

Adult↗
PubMed1983

The impact of an ECG computer analysis program on the cardiologist's interpretation. A cooperative study.

Nine experienced electrocardiographers and the ECG computer program developed in the Veterans Administration (AVA 4.0) were evaluated against ECG-independent evidence of 180 patients' true diagnoses. A cross section of cardiac abnormalities was included. Each reader was given the 12-lead and orthogonal 3-lead ECG. The impact of ECG computer reports on the interpretations by the nine readers was evaluated by comparing their interpretations before and after the addition of a computer report. Using only high probability statements, the average accuracy of ECG diagnosis by the nine readers was 54%. It increased to 62% when the computer report was added. Computer interpretation was correct in 76%. It was shown that the Bayesian classification method together with multivariate analysis, used in the VA program, are mainly responsible for the improvement in diagnostic accuracy.

Angina Pectoris↗
PubMed1983

Adverse acute and chronic effects of electrical defibrillation and cardioversion on implanted unipolar cardiac pacing systems.

Six cases are presented in which a transient or chronic rise in the stimulation threshold of a permanently implanted unipolar pacemaker resulted in the loss of effective pacing after therapeutic defibrillation or cardioversion. Although damage to the pulse generator may still occur, leading to a loss of function as demonstrated in a seventh patient, improvements in the internal protection circuits of the present generation of pacemakers makes this less likely while possibly predisposing to endocardial burns and increased fibrosis at the electrode-endocardial interface. The theoretical explanations for this phenomenon are discussed, along with recommendations for the prospective and retrospective management of the pacemaker patient who requires defibrillation or cardioversion.

Adult↗