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Biomedical subjects

R J Bryg

Publications and source records attributed to R J Bryg.

At least 19 recordsLinked to original sources
PubMed1996

Effects of A1 adenosine receptor agonism using N6-cyclohexyl-2'-O-methyladenosine in patients with left ventricular dysfunction.

BACKGROUND: The role of adenosine as a neuromodulator in heart failure was studied with the use of a selective adenosine A1 receptor agonist, N6-cyclohexyl-2'-O-methyladenosine (SDZ-WAG 994). METHODS AND RESULTS: Fifty patients with heart failure symptoms and moderate left ventricular systolic dysfunction had a balloon flotation catheter inserted. Patients received placebo or a single oral dose of either 1, 2, or 5 mg SDZ-WAG 994. After baseline measurements were obtained, hemodynamic and electrophysiological recordings were repeated at 30-minute intervals for the next 4 hours, then every 6 hours for the next 24 hours. Blood samples for norepinephrine, epinephrine, aldosterone, atrial natriuretic peptide, and plasma renin activity were drawn at baseline and 2 hours after drug administration. A adenosine receptor agonism produced no important effects on systemic, right atrial, pulmonary artery, or pulmonary capillary wedge pressures; cardiac index; respiratory rate; or heart rate. The PR interval (a reflection of A1 receptor-mediated activity) increased significantly in a stepwise fashion. At the 5-mg dose of SDZ-WAG 994, significant increases in atrial natriuretic peptide (216 +/- 137 to 407 +/- 146 pg/mL) and norepinephrine (477 +/- 243 to 618 +/- 237 pg/mL) levels were noted. CONCLUSIONS: A1 adenosine receptor agonism with SDZ-WAG 994 resulted in no significant hemodynamic changes at rest in this subset of patients with left ventricular dysfunction. An increase in the PR interval and atrial natriuretic peptide level, consistent with adenosine A1 receptor-mediated activity, was observed. In addition, an increase in the norepinephrine level was observed, suggesting a role for adenosine as a peripheral nervous system neuromodulator.

Adenosine↗
PubMed1995

Left-ventricular diastolic function and hypertension.

Left-ventricular diastolic function is influenced by multiple factors in hypertension. These factors include age, left-ventricular hypertrophy, afterload, left-atrial pressure, blood pressure, and myocardial stiffness. The influences of and interactions among these factors change the filling characteristics of the left ventricle and characterize diastolic function. Despite the complex nature of these interactions, important clinical information can be noninvasively derived by Doppler echocardiography and nuclear scintigraphy. The entire spectrum of hypertension is involved with and may alter left-ventricular diastolic function.

Aged↗
PubMed1993

Valvular heart disease: medical therapy and experimental and animal models.

Vasodilators have been advocated for the treatment of regurgitant valvular heart diseases for more than 12 years, and new information on their mechanisms of action is available. Anticoagulants continue as a mainstay of therapy for patients with prosthetic heart valves, and the most desirable levels of anticoagulation for different conditions have been examined. Clinical and animal research studies of cardiac adaptation to mitral and aortic valve diseases are discussed.

Animals↗
PubMed1992

Effect of clinical pharmacy input on physician prescribing habits in the nursing home care unit.

The goal of this study was to evaluate any changes in medication use in our 60-bed nursing home care unit as a result of eliminating clinical pharmacy services during a 2-week period. Information was obtained on patient medications and number of doses dispensed. All patients were found to have a 6% increase in average number of scheduled medications, a 3% increase in average total medications, and an increase in scheduled doses dispensed by 10% during the absence of clinical pharmacy services. These numbers declined by 16, 18, and 9%, respectively, 2 weeks after the return of clinical pharmacy services. When evaluating only those 37 patients present the entire 4 week period, average scheduled medications rose 5% and total medications rose 4% during the absence of clinical pharmacy services and declined 13 and 17%, respectively, upon return of services. Eleven patients showed an increase in total number of medications during the absence of clinical pharmacy services whereas 21 patients showed a decline in medications after the return of clinical pharmacy services (P less than 0.001). The authors conclude that clinical pharmacy services must be provided on a continuous basis to maintain good physician prescribing habits in the nursing home care unit.

Drug Utilization↗
PubMed1990

Effects of transdermal scopolamine on heart rate variability in normal subjects.

A decrease in cardiac parasympathetic tone is a recognized finding in patients with ischemic heart disease, sudden cardiac death and heart failure, correlating closely with disease severity and overall survival. To study the clinical potential of vagomimetic intervention, the effect of transdermal scopolamine on fluctuations in heart rate was studied in 32 healthy adult subjects using both time-domain (mean RR interval, standard deviation of the mean RR interval, mean of the differences between consecutive RR intervals) and frequency-domain measures (spectrum analysis of 128 consecutive RR intervals) of heart rate variability. After an exposure of 24 hours, transdermal scopolamine resulted in a significant increase in all indexes tested. The increase was most pronounced in the 0.25-Hz respiratory peak of the RR interval power spectrum, compatible with a strong vagomimetic mode of action of transdermal scopolamine. Results indicate that transdermal scopolamine may have potential merit as a selective vagotonic agent in certain patients with myocardial infarction, heart failure or ventricular arrhythmias.

Administration, Cutaneous↗
PubMed1990

Dietary calcium induces regression of left ventricular hypertrophy in hypertensive non-insulin-dependent diabetic blacks.

Recent data from this laboratory indicate that dietary calcium supplementation causes reduced intracellular calcium in type II diabetic hypertensives. Consequently, we have assessed the effects of calcium supplementation on forearm blood flow (FBF) and vascular resistance (FVR) and left ventricular mass (LVM) in seven type II diabetic hypertensive black men with left ventricular hypertrophy (LVH) maintained off antihypertensive treatment for four weeks and then supplemented with 600 mg calcium per day for three months. A comparable group of black diabetic hypertensive patients treated with atenolol (50 mg) served as controls. LVM was determined by M-mode echocardiography and FBF and FVR by electrical impedance plethysmography at the end of the four week baseline and the 12 week supplementation periods. Calcium supplementation resulted in a decrease (P less than .05) in mean arterial pressure (from 121 +/- 4 to 114 +/- 3 mm Hg) which was accompanied by an 18% increase in FBF and a 20% reduction in FVR (P less than .05). LVM decreased from 289 +/- 22 at baseline to 240 +/- 22 g at the end of the supplementation period (P less than .02) and there was a significant correlation between changes in FBF and LVM (r = 0.82). Left ventricular end diastolic dimension decreased by 11% (P less than .05). These data indicate that calcium supplementation sufficient to normalize dietary calcium in black hypertensive diabetic men significantly reduces vascular resistance and causes partial regression of LVH.

Black People↗
PubMed1989

Effect of passive tilt on sympathetic and parasympathetic components of heart rate variability in normal subjects.

Decreased heart rate (HR) variability has been shown to be an independent predictor of poor outcome after acute myocardial infarction. Presumably, both reduced parasympathetic activity and increased sympathetic activity contribute to this observed HR variability response. To elucidate the physiologic contributions of the sympathetic and parasympathetic nervous systems to HR variability, the effect of passive head-up tilt (+70 degrees) was investigated on 4 indexes of HR variability in 17 healthy subjects. The standard deviation of the mean of 512 consecutive RR intervals, a traditional marker of HR variability and a purported index of cardiac parasympathetic neural tone, was compared with the mean difference of 512 consecutive RR intervals, with the maximal expiratory RR interval to minimal inspiratory RR interval ratio (respiratory RR ratio) and with the low- and high-frequency components of the power spectrum of 512 consecutive RR intervals. Passive tilt produced a nonsignificant decrease in the standard deviation of RR intervals. There was, however, a highly significant decrease in the mean difference of consecutive RR intervals and the high-frequency component of the RR-interval spectrum. Both the respiratory RR ratio and the low-frequency component of the RR-interval spectrum increased with tilt. It was concluded that the mean difference of consecutive RR intervals and the high-frequency component of the RR-interval spectrum are potentially superior indexes of "pure" parasympathetic neural tone and may be preferable for future use in cardiovascular studies of autonomic dysfunction.

Adult↗
PubMed1989

Reassessment of the association between gastrointestinal arteriovenous malformations and aortic stenosis.

PURPOSE AND PATIENTS AND METHODS: The purported association between aortic stenosis and gastrointestinal arteriovenous malformations (AVMs) has not been rigorously evaluated. The diagnosis of aortic stenosis in most the prior studies has been based on clinical examination. We therefore utilized two-dimensional and Doppler echocardiography to document the presence or absence of aortic stenosis in 29 men with gastrointestinal AVMs documented by endoscopy. RESULTS: Of the 29 patients studied, 22 (76 percent) had ejection systolic murmurs and 18 (62 percent) had echocardiographic evidence of aortic sclerosis. However, none of the patients had any evidence of aortic stenosis as assessed by Doppler echocardiography. CONCLUSION: Although previous case reports and retrospective studies have suggested an association between gastrointestinal AVMs and aortic stenosis, our study does not support this association and suggests the need for a prospective trial.

Aortic Valve Stenosis↗
PubMed1987

Tricuspid regurgitation by Doppler echocardiography after orthotopic cardiac transplantation.

The incidence and severity of Doppler-detected tricuspid regurgitation (TR) and associated clinical variables was studied in 20 patients who underwent cardiac transplantation. Eighteen of the 20 patients had Doppler detectable TR after cardiac transplantation, 14 had moderate to severe TR and 4 mild TR. Echocardiographic evidence of right ventricular volume overload was present in 13 of 14 patients with moderate to severe TR and in none of the other 6 patients. Patient age, primary disease process, cold ischemic time of the transplanted heart, and the frequency or severity of organ rejection did not correlate with the development of TR. Two patients with significant TR had a torn or partially torn tricuspid chordae, indicating an organic etiology, and the remaining patients had functional TR. All 8 patients with a pulmonary artery systolic pressure of 55 mm Hg or more before transplantation had significant functional TR after transplantation (p less than or equal to 0.05). Pulmonary vascular resistance before transplantation was not predictive; however, after transplantation pulmonary vascular resistance was significantly greater in patients with moderate to severe TR (101.6 +/- 41.3 vs 50.2 +/- 16.6 dynes s cm-5, p less than or equal to 0.01).

Adolescent↗
PubMed1987

Left ventricular systolic and diastolic flow abnormalities determined by Doppler echocardiography in obstructive hypertrophic cardiomyopathy.

To analyze the relation of systolic anterior motion (SAM) of the mitral valve, peak left ventricular (LV) outflow tract velocity, aortic flow and mitral flow, 17 patients with obstructive hypertrophic cardiomyopathy (HC) (8 men, 9 women), aged 19 to 88 years (mean 45), were studied using M-mode and 2-dimensional echocardiography and pulsed and continuous-wave Doppler echocardiography and results were compared with those from 18 age-matched normal subjects. SAM was present in all patients with HC and absent in normal subjects. Time to peak outflow velocity as a percentage of LV ejection time was 63% in patients with HC and 29% in normal subjects (p less than 0.001). In 13 patients, time from the R-wave peak to the closest approximation of the mitral valve to the ventricular septum or initial contact during SAM was determined and was 242 +/- 66 ms and time from the R-wave peak to the peak LV outflow tract velocity was 242 +/- 73 ms (r = 0.90). In 11 patients time from the R-wave peak to cessation of flow in the ascending aorta was measured and was 286 +/- 80 ms; time from the R-wave peak to the peak LV outflow tract velocity was 246 +/- 75 ms. The ratio of early to late diastolic filling velocities of the left ventricle was 1.47 +/- 0.40 in the normal subjects and 1.26 +/- 0.84 in patients with HC (difference not significant). The early to late ratio of the 12 patients without mitral regurgitation was 0.99 +/- 0.52 (p less than 0.01 vs normal subjects).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Effect of aging on left ventricular diastolic filling in normal subjects.

To determine the effect of aging on left ventricular filling, mitral valve flow was evaluated with real-time (color flow) and conventional pulsed Doppler echocardiography in 32 subjects, aged 24 to 68 years, who had no evidence of cardiovascular disease. The diameter of mitral valve flow was measured in early and late diastole in the apical 4-chamber view. Transmitral velocities were measured in early and late diastole with pulsed Doppler echocardiography. The early flow diameter was significantly smaller in patients older than 50 than in those aged 20 to 29 years (p less than 0.05), while atrial flow diameter was significantly larger in patients older than 50 than in those aged 20 to 29 years (p less than 0.05). The ratio of early flow diameter to atrial flow diameter was 1.85 +/- 0.33 in patients 20 to 29 years old and 1.17 +/- 0.28 in those older than 50 (p less than 0.001). The ratio of early to atrial diastolic velocities was 1.98 +/- 0.53 in the younger patients and 1.07 +/- 0.41 in those older than 50 years (p less than 0.001). The ratio of early flow diameter to atrial flow diameter decreased significantly with aging, and this decrease had a negative correlation with aging (r = -0.64). Qualitatively, in these normal subjects, early diastolic flow filled the ventricle centrally, while with atrial contraction, flow entered the ventricle toward the posterolateral wall and was associated with flow moving toward the aortic valve along the ventricular septum.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Evaluation of left ventricular function during upright exercise: correlation of exercise Doppler with postexercise two-dimensional echocardiographic results.

The relationship of regional and global left ventricular function to aortic flow dynamics during exercise was determined in 14 normal subjects and 14 patients with coronary artery disease. Doppler and two-dimensional echocardiographic studies were performed before, during, and immediately after an exercise test by the Bruce protocol. Two-dimensional echocardiography was used to determine the ejection fraction and new wall motion abnormalities. The peak ejection velocity, stroke index, and cardiac index were calculated from the pulsed Doppler tracing. In normal subjects the ejection fraction increased significantly (p less than .001) from rest (0.51 +/- 0.07) to peak exercise (0.61 +/- 0.07), while the response in coronary patients was blunted (0.49 +/- 0.11 vs 0.48 +/- 0.16). Similarly, the change in peak ejection velocity throughout exercise in normal subjects (from 0.71 +/- 0.12 to 1.50 +/- 0.35 m/sec) was significantly (p less than .01) greater than that in patients with coronary artery disease (from 0.61 +/- 0.13 to 0.90 +/- 0.29 m/sec). There was a good correlation between the percent change in peak ejection velocity and the percent change in ejection fraction from rest to peak exercise in the entire study group (rs = .64) and in the patients with coronary artery disease (rs = .84). These preliminary data suggest that exercise-induced changes in Doppler echocardiographic variables may offer a potential adjunct in the evaluation of patients with ischemic heart disease.

Adult↗