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Biomedical subjects

D M Mirvis

Publications and source records attributed to D M Mirvis.

At least 55 records · Page 3Linked to original sources
PubMed1995

Effects of immature recruitable collaterals on myocardial blood flow and infarct size after acute coronary occlusion.

This study assessed the ability of immature recruitable coronary collateral vessels to alter regional myocardial blood flow and to protect jeopardized myocardium from infarction after acute coronary occlusion. An inflatable balloon occluder was placed around the left circumflex coronary artery of 7 dogs (group A), while nine dogs (group B) underwent placement of an Ameroid constrictor around the circumflex artery proximal to a balloon occluder. Group A dogs were studied 2 to 3 days after surgery; those in group B were studied 12 days after surgery, when partial collateralization had occurred. The circumflex artery was acutely occluded in both groups for 4 hours. Myocardial blood flow was measured with radioactive microspheres before, immediately after, and 4 hours after coronary occlusion. Infarct size, expressed as percent of left ventricular area at risk, was determined by triphenyl tetrazolium chloride staining after infusion of colored dyes to delineate perfusion beds. Flows in the ischemic circumflex bed 90 seconds after coronary occlusion decreased in both groups for both endocardial (0.04 +/- 0.02 ml/min/gm vs 0.09 +/- 0.04 ml/min/gm) and epicardial (0.19 +/- 0.07 ml/min/gm vs 0.26 +/- 0.08 ml/min/gm) layers. Four hours after coronary occlusion, endocardial flow did not rise significantly in group A (0.11 +/- 0.05 ml/min/gm), but increased significantly in group B to 0.52 +/- 0.13 ml/min/gm (p < 0.05). Epicardial flow at 4 hours was also significantly greater in group B (1.03 +/- 0.15 ml/min/gm) than in group A (0.55 +/- 0.13 ml/min/gm, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1994

Variation in utilization of cardiac procedures in the Department of Veterans Affairs health care system: effect of race.

OBJECTIVES: Utilization rates for cardiac catheterization and cardiac surgery in the Department of Veterans Affairs (VA) health care system were studied to determine whether racial differences existed in a delivery plan in which access is not determined by patient finances. BACKGROUND: Prior studies have demonstrated significant differences in utilization of cardiac diagnostic and therapeutic resources by white and black patients. Reasons for the reduced utilization by black patients include socioeconomic, biologic and sociocultural effects. METHODS: Computerized discharge records of 30,300 patients with coronary artery disease and 1,335 patients with valvular heart disease who were discharged from any of 172 VA Medical Centers between October 1, 1990 and September 30, 1991 were studied. RESULTS: For patients with coronary artery disease, utilization rates of cardiac catheterization were significantly greater for white patients (503.4 procedures/1,000 patients) than for black patients (433.2/1,000 patients), with a relative odds ratio of 1.33. Rates for surgery (179.0 vs. 124.5/1,000 patients) were also greater for whites than for blacks, with a relative odds ratio of 1.53. For the subset with valve disease, the catheterization rate was significantly greater for whites than for blacks (575.4 vs. 432.6 procedures/1,000 patients), with a relative odds ratio of 1.78. Surgical rates were not significantly different (423.8 vs. 354.6 operations/1,000 patients). Racial differences for both catheterization and surgery varied widely as a function of geographic region and the level of complexity of the local VA facility. CONCLUSIONS: Racial differences in resource utilization exist in a health care system in which economic influences are minimized. The pattern of these differences depends on numerous variables and suggests both biologic and sociocultural factors as underlying causes.

Black or African American↗
PubMed1994

Medical school affiliations with Department of Veterans Affairs medical centers: attitudes of medical center leadership.

Affiliations between Department of Veterans Affairs [VA] medical centers and colleges of medicine are important to both parties. Recently, the values and costs of these relations have come under increasing scrutiny. In this study, the authors attempted to determine the attitudes of local VA medical center leadership members toward these affiliations. A mail survey of directors, associate directors, and chiefs of staff of VA medical centers was undertaken. Respondents were asked to score their agreement or disagreement with each of eight statements defining various features and values of VA-medical school affiliations. Scores were reported on a Likert scale of 1 (strongly agree) to 7 (strongly disagree). Strongly positive general attitudes toward VA-university affiliations were found from the results. Mean scores averaged 2.02. However, responses to statements identifying specific concerns with these affiliations (eg, diversion of resources away from VA toward university goals and the lower status of VA-based faculty) were less positive. More positive general attitudes and less negativity about specific concerns were expressed by chiefs of staff than by medical center directors or associate medical center directors and by leaders of highly affiliated medical centers than by leaders of other types of centers. Therefore, local VA medical center leaders have very positive general attitudes toward university affiliations. However, specific problem areas do exist. These issues and attitudes are important for leaders of both the VA health-care system and academic medical centers to consider when developing and implementing local and national policies.

Administrative Personnel↗
PubMed1994

Attitudes of local VA leadership toward the VA health care system.

A nationwide survey of directors, associate directors, and chiefs of staff of Department of Veterans Affairs (VA) Medical Centers was conducted to (1) determine the attitudes of these local health care executives toward the public's perception of the VA health care system, their own job satisfaction, and the level of job support they receive; and (2) assess how these attitudes relate to the stated intention of the local leadership to leave the VA health care system before retirement. A total of 268 responses were analyzed. Significant differences between local executive positions were identified, including a less favorable perception of the public's attitude toward the VA system and less satisfaction with the VA system by chiefs of staff; and less general job satisfaction and satisfaction with the local VA facility by associate directors. Variables related to public perception, job satisfaction, and job support were significant predictors of plans for each group to leave the VA; 34 to 49 percent of the variance in a multiple linear regression model could be explained by these factors.

Adult↗
PubMed1993

Left ventricular hypertrophy: effect on survival.

OBJECTIVES: The aim of the study was to determine whether left ventricular hypertrophy has an independent adverse effect on survival. BACKGROUND: Left ventricular hypertrophy is considered to be a significant risk factor for coronary heart disease mortality; however, the impact of coexisting coronary artery stenosis on survival statistics is not clear. METHODS: The relations among electrocardiographic (ECG) left ventricular hypertrophy, ST-T segment abnormality, coronary artery disease and survival were examined in 18,969 patients undergoing coronary arteriography between 1972 and 1985. Patients were excluded if they underwent coronary revascularization or had unstable angina, rheumatic or congenital heart disease, cardiomyopathy, pericardial disease or ECG changes other than left ventricular hypertrophy or repolarization abnormalities, leaving 4,824 patients for analysis. RESULTS: Left ventricular hypertrophy was present in 249 patients, whereas 4,575 were free of left ventricular hypertrophy. Five-year survival was 90.2% in the group without left ventricular hypertrophy and was significantly lower (81.9%, p < 0.001) in the group with left ventricular hypertrophy. Five-year survival was significantly lower in patients with left ventricular hypertrophy, regardless of whether coronary artery disease was present: 84.4% versus 94.5% (p = 0.016) in the absence of coronary artery disease and 81.0% versus 87.7% (p < 0.001) in the presence of coronary artery disease. The presence of ST segment abnormalities was not associated with a significant reduction in survival in patients without coronary disease, although mortality was less in those without ST changes who had coronary disease (p = 0.012). CONCLUSIONS: It is concluded that ECG left ventricular hypertrophy has an adverse effect on survival, even in patients who are free of coronary artery disease.

Adult↗
PubMed1992

Anatomic basis for the injury current producing ST-segment shifts on the body surface ECG.

ST-segment depression is the characteristic electrocardiographic response to myocardial ischemia. A hypothesis is presented defining the structural and functional requirements for ischemic blood flow and ST-T wave potential gradients for ST-segment depression to occur. Both flow and potential gradients may be either transmural or transventricular. ST-segment depression results only when both are concordant (e.g., both transmural); however, ischemic ST-segment depression does not follow when flow and potential gradients are discordant (e.g., one transmural and one transventricular).

Animals↗
PubMed1991

Effects of myocardial infarction on cardiac electrical field properties using a numerical expansion technique.

This study was undertaken to quantify basic cardiac electrical field properties using the Karhounen-Loeve (K-L) numerical expansion technique after experimental myocardial infarction. Transmural anterior myocardial infarction was produced in seven dogs by injection of liquid latex into the anterior descending artery; posterior myocardial infarction was produced in five dogs by injection of the circumflex artery. Body surface potentials from 84 electrodes were recorded during sinus rhythm prior to and 1 week after infarction. Electrical field properties during the QRS, ST, and QRST intervals were computed by the K-L method based upon areas calculated for each lead. The ratio of the sum of magnitude of the first three eigenvectors to the sum of all computed eigenvectors expressed as a percentage was used as a measure analogous to field dipolarity. Values before infarction were high during the QRS (97.1% +/- 2.0%, mean +/- 1SD), ST (96.0% +/- 5.1%), and QRST (97.7% +/- 2.7%) intervals, with no significant difference between the three periods. After infarction, the ratio during QRS decreased significantly, with lower values after posterior (61.9% +/- 11.7%) than after anterior (91.1% +/- 6.0%) infarction (p less than 0.001). Values during ST and QRST intervals were not significantly changed by infarction. Spatial patterns of the first eigenvector indicated that the derived QRS area electric field is directed away from the myocardial lesion for both anterior and posterior infarcts. Thus, experimental myocardial infarction produces significant changes in cardiac electrical field properties as measured by the K-L technique.

Animals↗
PubMed1991

Interactive effects of ST-T wave abnormalities on survival of patients with coronary artery disease.

Previous studies have documented a reduced survival time in patients with an electrocardiographic (ECG) ST-T wave abnormality. This study was designed to determine the clinical, hemodynamic and angiographic correlates of this observation. Data from 9,731 patients undergoing cardiac catheterization from 1976 through 1986 were analyzed; 5,531 had severe (greater than 70%) obstruction of at least one major coronary artery, 1,706 had mild (10 to 69%) obstruction and 2,494 had no obstruction. Of the patients with severe obstruction, 2,536 were treated medically and 2,995 were treated by surgical revascularization. Patients with an ST-T abnormality had more clinical risk factors (including older age and greater prevalence of diabetes mellitus, hypertension and prior myocardial infarction) and greater left ventricular dysfunction (including higher end-diastolic pressure and ventricular volume, reduced ejection fraction and greater prevalence of contraction abnormality) than did those without this ECG pattern. Survival time was significantly (p less than 0.01) reduced in subsets of patients with an ST-T abnormality and with severe or mild coronary artery disease; in those without coronary disease, ST-T changes did not correlate with reduced survival. Stepwise regression analysis was applied to each group to determine the independent predictors of 5-year survival. In patients with severe disease or no disease, an ST-T abnormality was not chosen as an independent predictor of 5-year survival; in the group with mild disease, ST-T changes were an independent predictor of reduced survival. Thus, the independent impact of an ST-T abnormality on survival is dependent on the severity of underlying coronary artery disease.

Cardiomegaly↗
PubMed1991

A placebo-controlled trial of continuous intravenous diltiazem infusion for 24-hour heart rate control during atrial fibrillation and atrial flutter: a multicenter study.

The safety and efficacy of a 10- to 15-mg/h continuous infusion of intravenous diltiazem were evaluated in 47 patients with atrial fibrillation or flutter who first responded to 20 mg or 20 mg followed by one or more 25-mg bolus doses of open label intravenous diltiazem. Of the 47 patients, 44 responded to the bolus injection and were randomized under double-blind conditions to receive either a continuous infusion of intravenous diltiazem (10 to 15 mg/h) (23 patients) or placebo (21 patients) for up to 24 h. Seventeen (74%) of the 23 patients receiving diltiazem infusion and none of the 21 with placebo infusion maintained a therapeutic response for 24 h (p less than 0.001). Over 24 h, patients receiving diltiazem infusion lost response significantly more slowly than did those receiving placebo infusion (p less than 0.001). Nonresponders to the double-blind infusion were given an additional bolus injection of open label intravenous diltiazem and administered an open label 24-h intravenous diltiazem infusion. The overall proportion of patients maintaining a response to a 24-h infusion of intravenous diltiazem under double-blind or open label conditions combined was 83% (34 of 41). Efficacy of the 24-h infusion of intravenous diltiazem was similar in elderly versus young patients, those who did versus those who did not receive digoxin and those weighing less than 84 versus greater than or equal to 84 kg. However, intravenous diltiazem appeared to be more effective in atrial fibrillation than in atrial flutter. No significant untoward effects were noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Clinical and pathophysiologic correlates of ST-T-wave abnormalities in coronary artery disease.

Clinical, hemodynamic and coronary angiographic data from 9,801 patients were evaluated to determine the correlates of ST-segment depression, with or without T-wave inversion, on the resting routine electrocardiogram. The relative risk (RR) of having a measured clinical or angiographic variable was computed whether or not ST-T-wave abnormalities were observed. ST-segment depression was seen significantly more often in subjects greater than 55 years of age (RR = 1.4) who were women (RR = 1.3) or nonwhite (RR = 1.5), were hypertensive (RR = 1.8), had diabetes mellitus (RR = 1.6) or who smoked cigarettes (RR = 1.5). Angiographic findings related to presence of ST-T-wave abnormalities included severe coronary obstruction (less than 70%), higher number of diseased vessels, and the presence of obstruction in the left anterior descending coronary artery. In a multivariate model, the most significant correlates of ST-T-wave abnormalities were presence of left ventricular contraction abnormality, followed by age, gender, presence of left anterior descending coronary artery disease, elevated end-systolic volume index, and a diagnosis of hypertension. Thus, electrocardiographic ST-T abnormalities has specific and significant clinical and pathophysiologic correlates.

Cardiac Catheterization↗
PubMed1990

Physicians in organizations. Dilemma of the academic VA staff physician.

More physicians are assuming salaried positions within large health care organizations. In this report, we discuss the influence of such organizational changes on physician behavior in one large health care system--the Department of Veterans Affairs (VA) system--which employs more than 14,000 physicians. Conflicting pressures on these physicians in VA facilities affiliated with academic medical centers include differences between professional and organizational needs plus differences between the roles of the VA hospital and of the affiliate academic medical center. An analysis of these issues, based on organizational theory, suggests that these clashes are consequences of fundamental differences between the parties involved. Because the outcome of the conflicts may be fatal to the organizations, they must be managed, not ignored. This involves recognizing the existence and the nature of the differences as well as actively sharing the responsibilities and the issues usually charged to one of the two conflicting groups to form a conjoint organization between the "two sides of the street."

Academic Medical Centers↗
PubMed1990

Interactive effects of age and other risk factors on long-term survival after coronary artery surgery.

The effect of age at the time of coronary artery bypass graft surgery on postoperative survival was studied in 2,507 patients with significant coronary artery disease. Patients were subdivided into five groups based on age at the time of surgery: 20 to 39, 40 to 49, 50 to 59, 60 to 69 and greater than or equal to 70 years. The observed death rate was compared with that expected for subjects from the general U.S. population matched for age, gender, race and calendar year. For patients less than or equal to 59 years of age, the ratio of observed to expected death rates was significantly greater than unity (observed/expected = 4.9 for ages 20 to 39, 1.9 for ages 40 to 49 and 1.3 for ages 50 to 59 years, p less than 0.01). The prevalence of risk factors, including diabetes mellitus, hypertension, hypercholesterolemia and cigarette smoking, was evaluated in the different age subgroups. When patients were subdivided on the basis of history of cigarette smoking, the decreased relative survival rate of younger (less than 60 years old) patients existed only in those who smoked (observed/expected = 6.0 for ages 20 to 39, 2.2 for ages 40 to 49 and 1.4 for ages 50 to 59 years). In nonsmokers, observed/expected ratios for every age group were not significantly different from unity. Thus, the reduced relative survival rate of younger patients after coronary artery bypass graft surgery may be attributed to the interactive harmful effects of cigarette smoking.

Adult↗
PubMed1990

Chronic therapy for congestive heart failure with benazepril HCl, a new angiotensin converting enzyme inhibitor.

Benazepril HCl is an orally effective angiotensin converting enzyme (ACE) inhibitor previously shown to have significant acute hemodynamic benefits in patients with congestive heart failure. In this study, 21 patients with New York Heart Association Class III or IV congestive heart failure were treated with 2 to 15 mg of benazepril HCl as a single daily oral dose for 28 days to determine the clinical and hemodynamic value of chronic therapy. Each patient underwent clinical evaluation during the 28-day period, as well as invasive hemodynamic studies on the first two and last two days of the trial. Plasma ACE activity and aldosterone levels fell significantly and renin levels rose after therapy. Benazepril HCl produced significant (p less than 0.01) reductions in arterial pressure and systemic vascular resistance, with corresponding increases in cardiac output and decreases in pulmonary artery wedge pressure. Responses after 28 days of therapy were equivalent to those after the initial doses. Clinical effects included reduced rest, exertional and paroxysmal nocturnal dyspnea, as well as reduced peripheral edema. Only one patient developed symptomatic orthostatic hypotension. Thus, benazepril HCl, given once daily, is an effective and well tolerated oral agent for the chronic treatment of advanced congestive heart failure.

Aged↗
PubMed1990

Estrogen replacement and coronary artery disease. Effect on survival in postmenopausal women.

The relationship among postmenopausal estrogen use, coronary stenosis, and survival was examined retrospectively in 2268 women undergoing coronary angiography. The patients were selected for study if their age was 55 years or older at the time of angiography or if they had previously undergone bilateral oophorectomy. Postmenopausal estrogen use in 1178 patients with coronary artery disease (greater than 70% stenosis) and 644 patients with mild to moderate coronary artery disease (5% to 69% stenosis) was compared with 446 control subjects (0% stenosis) using life-table analysis. Over 10 years of follow-up, there was no significant difference in survival among patients initially free of coronary lesions on arteriography who had either never used (377) or ever used (69) estrogens. Among patients with mild to moderate coronary stenosis, 10-year survival of those who had never used estrogens was 85.0% and it was 95.6% among 99 "ever users." Survival was 60.0% among those with more than 70% coronary stenosis who had never used estrogen and it was 97.0% among 70 ever users. The "never users" group were older (65 vs 59 years), had a lower proportion of cigarette smokers (40% vs 57.1%), a higher proportion of subjects with diabetes (21.7% vs 12.9%) and hyperlipidemia (58% vs 44%), and approximately equal numbers of hypertensives (56.0% vs 54.3%). Cox's proportional hazards model was used to estimate survival as a function of multiple covariables. Estrogen use was found to have a significant, independent effect on survival in women. We conclude that estrogen replacement after menopause prolongs survival when coronary artery disease is present, but it has less effect in the absence of coronary artery disease.

Aged↗