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Biomedical subjects

J Barry

Publications and source records attributed to J Barry.

At least 109 records · Page 6Linked to original sources
PubMed1988

Variability of transient myocardial ischemia in ambulatory patients with coronary artery disease.

Ambulatory electrocardiographic (ECG) monitoring of patients with chronic stable angina has demonstrated frequent and prolonged episodes of ischemic ST segment depression, but its clinical use requires an understanding of the components and extent of variability. Therefore, variations in the frequency and duration of episodes of ST segment depression were evaluated with ambulatory ECG recording at daily, weekly, and monthly intervals in 42 patients with chronic stable angina and known coronary artery disease. Data were analyzed with a nested analysis of variance design that yields estimates of variance components. From the estimates of variance components, power calculations and minimum significant percent reductions in frequency and duration of ischemia were derived. During 4,656 hours of ambulatory ECG monitoring, 1,262 episodes of ischemic ST segment depression were detected. The frequency of episodes was 6.3 +/- 0.45/24 hr (mean +/- SEM), and the duration of episodes was 18.3 +/- 2.8/24 hr. Because of variability over time, the ability to detect significant changes was dependent upon the number of subjects, length of monitoring period, and intervals between monitoring periods. In a clinical trial, for example, a sample size of 25 patients monitored for 48 hours with 1 week between control and test conditions would require a 65% reduction in frequency, whereas a sample size of 50 patients monitored under similar conditions would require a 46% reduction in frequency, to attribute the change with 90% power to a therapeutic intervention rather than to a spontaneous variation. When monitoring a single patient for 48 hours with 1 week or 1 month between control and repeat monitoring sessions, episodes of ischemic ST depression must be eliminated to detect significant therapeutic changes in ischemic activity at the 95% confidence level.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Prognostic importance of myocardial ischemia detected by ambulatory monitoring in patients with stable coronary artery disease.

To assess the relations of electrocardiographic measures of ischemia with the development of adverse coronary events, 86 patients with stable coronary artery disease and positive exercise tests for myocardial ischemia underwent ambulatory monitoring of the electrocardiogram. Monitoring was performed after withdrawal of antianginal medications, and prospective follow-up was obtained on routine medical care as prescribed by physicians who were unaware of monitor results. Forty-nine patients (57%) had a total of 426 episodes of ST segment depression; only 60 episodes (14%) were associated with symptoms of angina or an equivalent. During a mean follow-up of 12.5 +/- 7.5 months, there were two cardiac deaths, four myocardial infarctions, four hospitalizations for unstable angina, and 11 revascularization procedures required for new or worsening symptoms in 15 patients. All but one of these events (a hospitalization for unstable angina) occurred in the group of patients with ST segment depression on monitoring (p = 0.003). In multivariate analysis controlling for age, sex, and clinical descriptions of angina, the presence of ischemia on ambulatory monitoring was a significant predictor of outcome, while exercise test characteristics were not. Therefore, ischemia detected by ambulatory monitoring was common in patients with stable symptoms of coronary artery disease, and its presence identified a high-risk group for the development of subsequent unfavorable outcomes while on routine medical therapies.

Adult↗
PubMed1988

Variability of the perceived sense of effort in breathing during exercise in patients with chronic obstructive pulmonary disease.

The present study examined the reproducibility with which subjects with stable chronic obstructive pulmonary disease (COPD) scale the sense of effort involved in breathing during exercise. The sense of effort was assessed in 6 subjects with COPD during bicycle exercise continued to a symptom-limited maximal work load using a conventional category scale. Reproducibility of the sensory experience was assessed by comparing results obtained from 3 incremental work tests, 2 on the same day and a subsequent test performed within 1 to 10 days. During all trials in all subjects, sensory scores correlated closely with both minute ventilation and oxygen consumption (r greater than or equal to 0.92 for both VE and VO2). The average coefficients of variation for the maximal Borg Score and Borg Score at 2 min of exercise for the group as a whole were 3 +/- 1 and 3 +/- 2% (SE), respectively. Variability in sensory scores was not significantly different on exercise trials performed either within or between days. Furthermore, variability of sensory scores, oxygen consumption, heart rate, or minute ventilation were similar. We conclude that when using a category scale in subjects with COPD, the perceived sense of effort in breathing during exercise is highly reproducible, correlates closely with physiologic measures defining the intensity of exercise, and is no more variable than physiologic parameters typically measured during an exercise test.

Aged↗
PubMed1987

Ambulatory monitoring of the digitized electrocardiogram for detection and early warning of transient myocardial ischemia in angina pectoris.

Patients with coronary artery disease have frequent asymptomatic episodes of ischemic ST-segment depression. A new solid-state recorder that analyzes the digitized electrocardiogram (ECG) in real time has been tested for accuracy in detection and quantitation of these events by comparison with a direct ECG during exercise testing and a frequency-modulated recorder during ambulatory monitoring. The device can also be programmed to produce a tone at the onset of ischemic ST-segment depression, and this tone is used to initiate self-administration of nitroglycerin in an attempt to control myocardial ischemic events. The solid-state recorder demonstrated adequate sensitivity and specificity during exercise (100% and 92%, respectively) for detection and quantitation of episodes of ischemic ST-segment depression. In addition, Monitor One accurately measured the duration of ischemic events during exercise testing (r = 0.95, p = 0.001) and the number (r = 0.92, p = 0.001) and duration (r = 0.97, p = 0.001) of ischemic events during ambulatory monitoring. When the audible tone was used to initiate use of nitroglycerin, the duration of episodes of ischemic ST-segment depression was reduced from 105 +/- 74 min/24 hours to 58 +/- 49 min/24 hours (p = 0.02). Thus, a solid-state ECG recorder capable of long-term monitoring appears to accurately detect and quantify episodes of ischemic ST-segment depression in patients with coronary artery disease. Also, patients can interact with an audible tone to key self-administration of therapy in an attempt to control asymptomatic episodes of transient myocardial ischemia.

Adult↗
PubMed1987

The oldest old.

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Aged↗
PubMed1987

Selective therapeutic embolization of renal cell carcinoma in solitary kidneys.

We report 3 cases of renal cell carcinoma in a solitary kidney treated by selective tumor embolization. Embolization resulted in occlusion of the majority of the vascular supply of the tumor, with preservation of normal renal parenchyma and sufficient renal function. Selective tumor embolization is a good therapeutic alternative in patients in whom partial nephrectomy cannot be performed. Owing to the limited availability of bucrylate, absolute ethanol is recommended as the preferred embolic agent.

Aged↗
PubMed1987

Circadian variation of transient myocardial ischemia in patients with coronary artery disease.

To examine whether a significant circadian variation of transient myocardial ischemia exists and to better understand the character of such variation, 32 patients with chronic stable symptoms of coronary artery disease underwent one or more days of ambulatory monitoring of ischemic ST segment changes during daily life. A total of 251 episodes of ischemic ST segment depression occurred in 24 (75%) of the 32 patients with a median duration of 5 min (range 1 to 253). A significant circadian increase in ischemic activity was found with 39% of episodes and 46% of total ischemic time occurring between 6 A.M. and 12 P.M. (p less than .05 and p = .02, respectively). In 21 patients with ST segment depression during the 6 hr after waking and the 6 hr before sleep, 68% of episodes occurred in the morning compared with 32% in the evening. There were no significant differences in heart rate at onset, heart rate at 1 min before onset, and activity score associated with ST segment depression. The proportion of minutes showing ST segment depression when the heart rate was above the lowest rate associated with ST segment depression was significantly greater in the morning compared with the evening (26% vs 15%; p = .03). Thus the early morning increase in ST segment depression does not appear to be explained by differences in extrinsic activity and/or stress measured by physical activity score and heart rate response. More importantly, this phenomenon is often ignored by the usual patterns of drug administration for angina.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Active transient myocardial ischemia during daily life in asymptomatic patients with positive exercise tests and coronary artery disease.

The management of asymptomatic patients with coronary artery disease (CAD) is controversial, and the level of "activity" of their CAD during normal daily life remains largely unknown. To examine this question, ambulatory Holter monitoring of ST segments was performed out of the hospital in 7 asymptomatic subjects with CAD during normal daily activities. Their condition was detected because they all had a silent positive exercise test and angiographically proved CAD. During a total of 384 hours of monitoring, 37 asymptomatic episodes of ST depression (1 mm or greater and lasting at least 30 seconds) were recorded in 5 of the patients. Most episodes (68%) were 10 minutes or less in duration but ranged from 1 to 253 minutes, and most (70%) had a maximal ST depression of 1 to 2 mm. A small increase in heart rate, ranging from 1 to 34 beats/min, preceded 65% of the episodes, but 35% were associated with no change or even a decline before the onset of ischemia. Fifty-four percent of the episodes occurred during rest or usual light physical activity, 8% during sleep and only 38% during exercise, including 1 prolonged bout while jogging. During 78% of the episodes, the subjects rated their mental activity as usual and only 14% occurred during mental stress. In addition, a distinct diurnal variation was noted with 57% of the ischemia occurring between 0600 and 1200 hours (p = 0.008). Therefore, most asymptomatic subjects had active transient ischemia during daily life, with many of the characteristics already described in symptomatic subjects with CAD.

Activities of Daily Living↗
PubMed1986

Factors determining the activity of ischemic heart disease.

Transient regional myocardial ischemia appears to underlie symptoms such as angina pectoris and represents a key pathophysiologic step, since it is an objective marker of disease activity and is capable of causing disabling symptoms and damage to left ventricular myocardium. A study of the characteristics of transient ischemia in and out of the hospital has shown that symptoms are an inconsistent underestimation of these events. Ischemia is generally prolonged, mostly asymptomatic, and usually accompanied by a regional decrease in myocardial perfusion. Studies out of the hospital have also shown that these episodes are frequently triggered by a wide range of ordinary everyday activities. These new features of transient ischemia are worth noting when searching for relevant causes that are present during everyday life and when trying to choose more rational therapy. More detailed studies of patient activity have shown that different levels of mental arousal are the most common triggering mechanism causing ischemia out of the hospital. In addition, the occurrence of transient ischemia during everyday life displays a circadian rhythm, with an increase and peak occurrence between 6:00 A.M. and 12 noon each day. The day-to-day variability of ischemia is marked, indicating functional disturbances of coronary stenoses against a background of a severe reduction in cross-sectional area. The examination of proximal stenoses has shown that the reduction in cross-sectional area is usually underestimated by conventional angiography; pressure gradients across coronary stenoses are common and, with reduced poststenotic blood pressure, can jeopardize perfusion; disturbances of vessel caliber and antegrade flow can accompany many of the ordinary everyday activities known to trigger ischemia detected in Holter tapes studied out of the hospital; and there is clear-cut evidence of endothelial dysfunction in these patients, with reversal of the normal dilator response to acetylcholine and paradoxical constriction of stenoses. This evidence of endothelial dysfunction in humans could be central to the problems of atheromatous narrowing, thrombus, and disturbed vasomotion.

Angina Pectoris↗
PubMed1986

Cardiopulmonary resuscitation (CPR) training. Consequences for family members of high-risk cardiac patients.

A prospective, controlled trial was conducted to document the psychological risks and benefits of teaching cardiopulmonary resuscitation (CPR) techniques to family members of patients at high risk for a sudden death event. Clinical outcomes for the high-risk patients were also measured. Cardiac patients (n = 65) and their family members (n = 69) were randomized to one of three groups: CPR training, risk factor education, and control. Patients did not attend either intervention group. No adverse psychological effects for family members were documented. The patients in the CPR group, however, were more anxious at three months' follow-up than patients in either the educational or control groups. Patients in both CPR and risk factor education groups reported poorer adjustment to illness at six months' follow-up than did control patients. These results suggest that CPR training for family members may have an adverse psychological effect on high-risk cardiac patients.

Adaptation, Psychological↗
PubMed1986

Features of the exercise test that reflect the activity of ischemic heart disease out of hospital.

To better understand the relationship between the transient myocardial ischemia seen during an exercise test and ischemic activity out of hospital, 39 patients with well-documented coronary artery disease underwent standard treadmill exercise testing (Bruce protocol) and 24 to 48 hr of continuous ambulatory electrocardiographic monitoring during normal daily activities. A total of 245 episodes of transient ischemia were recorded in 21 of 32 patients with positive exercise electrocardiograms (group I), whereas seven patients with negative test results (group II) had no episodes of transient ischemia, during monitoring out of hospital (p less than .01). Certain measures in the exercise test were related to the severity of ischemia out of hospital: there were more episodes and a greater total duration of transient ischemia per 24 hr of ambulatory monitoring in patients who developed ischemic electrocardiographic changes before 6 min of exercise (p less than or equal to .021) or at a heart rate of less than 150 beats/min (p = .005) and in those in whom these ST segment changes persisted for more than 5 min after exercise (p less than or equal to .016). In contrast, there was no relationship between transient ischemia out of hospital and the commonly quoted exercise variables: chest pain, total exercise duration, and the maximum levels of heart rate, systolic blood pressure, and double product. Thus, patients with coronary artery disease and negative exercise electrocardiograms are most unlikely to experience active ischemia during normal daily life.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗
PubMed1986

Potential for real-time processing of the continuously monitored electrocardiogram in the detection, quantitation, and intervention of silent myocardial ischemia.

Current technology for monitoring and analyzing the ST segment allows for accurate description of ST-segment deviation, which in most cases is a valid measure of myocardial ischemia. In this article, the authors describe a new method that utilizes microprocessor analysis of the electrocardiogram to detect ST-segment deviation in ambulatory subjects. This technique results in the ability to characterize the total ischemic burden over long periods of time and to intervene acutely in order to treat myocardial ischemia and possibly to prevent complications of coronary artery disease.

Algorithms↗
PubMed1985

Activity of transient myocardial ischemia out of hospital in coronary artery disease and implications for management.

The management of patients with angina pectoris is based largely on the severity of symptoms, coronary anatomy and left ventricular function. The outcome for these patients is highly variable and depends largely on the degree of ischemic damage to the left ventricular myocardium. Recent work suggests that exercise-induced myocardial ischemia with or without angina is associated with a poor prognosis. Ambulatory monitoring of the electrocardiogram has revealed that most patients have frequent and prolonged episodes of transient ischemia out of hospital. These episodes are often asymptomatic and associated with ordinary everyday activities. In addition, ambulatory monitoring has demonstrated that transient ischemia during daily life has a circadian variation with exacerbations and peak density of ischemia in the first 4 to 6 waking hours of the day. Further studies have demonstrated that regional decreases in coronary blood flow occur during these ischemic episodes and have the same features seen out of hospital on continuous monitoring. These newly noted characteristics of transient ischemia raise a number of practical questions for treatment. Is it necessary to relieve all ischemic activity quite apart from that which occurs with chest pain? Does present use of antianginal medication neglect the early morning increases in transient ischemia that occur, and are different dosage regimens required to treat ischemia adequately? Does suppression of all ischemic activity further protect myocardium and improve prognosis for the patient?

Angina Pectoris↗
PubMed1985

Purification and properties of the bacteriophage T4 gene 61 RNA priming protein.

The bacteriophage T4 gene 61 protein is required, together with the gene 41 protein and single-stranded DNA, for the synthesis of the pentaribonucleotides that are used as primers for the start of each new Okazaki DNA fragment during T4 DNA replication. Using this priming activity as an assay, we have purified the 61 protein to essential homogeneity in milligram amounts. The priming activity was identified with the product of T4 gene 61 by using two-dimensional polyacrylamide gel electrophoresis to compare all of the T4-induced proteins in wild-type and mutant infections; the purified protein co-migrates with the only detectable protein missing in a 61- mutant infection. The purified 61 protein is shown to bind to the T4 helix-destabilizing protein (gene 32 protein) and to both single-stranded and double-stranded DNA. We have failed to detect any ribonucleotide polymerizing activity in either the 61 protein or the 41 protein alone; both the 61 and 41 proteins must be present to observe any synthesis of oligoribonucleotides.

Chromatography↗