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Biomedical subjects

S F Horowitz

Publications and source records attributed to S F Horowitz.

At least 19 recordsLinked to original sources
PubMed1995

Serial myocardial perfusion imaging with dipyridamole and rubidium-82 to assess restenosis after angioplasty.

UNLABELLED: The purpose of this study was to determine whether patients at high risk for clinical restenosis, following coronary angioplasty, could be identified by myocardial perfusion imaging performed with dipyridamole- 82Rb PET. METHODS: Forty-five patients (34 men, 11 women; mean age 58.5 yr) who had successful single-vessel angioplasty and were asymptomatic had dipyridamole-82Rb PET at 1 and 3 mo after the procedure. Abnormal flow reserve in the distribution of the angioplasty artery on PET was considered to be a decrease of > or = 1 perfusion grade in response to dipyridamole (assessed qualitatively from tomographic images and polar coordinate maps). Follow-up was performed for 6 mo postangioplasty. Clinical restenosis was defined as recurrent angina similar to that occurring before angioplasty and/or > or = 50% stenosis at the angioplasty site documented angiographically. We analyzed abnormal flow reserve in the distribution of the angioplasty vessel to identify which patients were at high risk for clinical restenosis. RESULTS: Fourteen patients developed clinical restenosis between 1 and 6 mo postangioplasty. Abnormal relative flow reserve in the distribution of the angioplasty vessel was present prior to the development of symptoms in 13 of 14 patients with clinical restenosis and in 8 of 31 patients without clinical restenosis (sensitivity 93%, specificity 74%, p < 0.0001). PET imaging successfully separated postangioplasty patients into groups with high (62%) and low (4%) risk of clinical restenosis. CONCLUSION: Abnormal relative flow reserve in the distribution of the angioplasty vessel on dipyridamole PET identifies asymptomatic postangioplasty patients at risk for clinical restenosis.

Angioplasty, Balloon, Coronary↗
PubMed1995

Silent myocardial ischemia during PET.

A resting perfusion defect detected during radioisotope myocardial perfusion imaging is generally thought to represent myocardial infarction. The administration of nitroglycerin during cardiac PET imaging results in improved resting defects, which suggests transiently abnormal resting perfusion with silent myocardial ischemia.

Aged↗
PubMed1992

Lung and myocardial thallium-201 kinetics in resting patients with congestive heart failure: correlation with pulmonary capillary wedge pressure.

Increased lung thallium-201 activity occurs with exercise in patients with severe coronary artery disease as a result of increased pulmonary capillary wedge pressure. No study has shown resting lung kinetics in chronic congestive heart failure. To better understand the relationship between lung and myocardial thallium uptake and pulmonary capillary wedge pressure, this study was performed. Resting lung and myocardial thallium uptake, expressed as a ratio, were compared with simultaneous pulmonary capillary wedge pressure in 16 patients with congestive heart failure and cardiomyopathy, all New York Heart Association class IV. There were no variations in pulmonary capillary wedge pressure throughout the study protocol. There was a significant reduction in the lung/myocardium thallium ratio from 10 to 60 minutes (0.83 +/- 0.30 to 0.59 +/- 0.17; p less than 0.001). At 60 minutes after thallium injection there was a linear correlation between the lung/myocardium ratio and capillary wedge pressure with an r value of 0.62 (p less than 0.01). Thus thallium-201 washout is rapid despite persistence of pulmonary capillary wedge pressure elevation, indicating that clearance does not imply resolution of congestive heart failure. In addition, a significant but imprecise correlation was found between capillary pressure and the lung/myocardium ratio. Rapid changes in lung activity during the early postinjection period may limit the clinical use of the lung/myocardium ratio.

Catheterization, Swan-Ganz↗
PubMed1992

The effect of stress and fatigue on cardiac rhythm in medical interns.

Twenty-four-hour ambulatory electrocardiographic monitoring was used to determine the incidence of arrhythmia while on-call and its relationship to stress and fatigue in 20 healthy medical interns. Mitral valve prolapse was present in 8 of 19 interns (42%). Heart rates ranged from a maximum of 103-167 beats/min (135 +/- 16) to a minimum of 38-61 beats/min (47 +/- 5). Interns had at least one episode of sinus tachycardia/h during 57% +/- 21% (range, 8-88%) of their hours on-call. Atrial premature beats (APB) were present in 19 of 20 (95%) and ventricular premature beats (VPB) in 12 of 20 (60%) subjects. APB/h ranged from 0 to 1.2 (0.4 +/- 0.3) and VPB/h from 0 to 23 (2 +/- 6). Three interns had multiform VPB and two had ventricular couplets. More APB/h occurred in interns under greater stress (0.5 +/- 0.4/h vs 0.3 +/- 0.1/h, p < 0.05) and combined stress and fatigue (0.6 +/- 0.4/h vs 0.2 +/- 0.2/h, p < 0.01). More VPB/h (5 +/- 9/h vs 0.5 +/- 0.6/h, p < 0.05) and higher (Lown) grade ventricular ectopy (2.3 +/- 1.6 vs 0.8 +/- 1.1; p < 0.05) occurred in interns under greater combined stress and fatigue. Mitral valve prolapse, sleep deprivation and caffeine intake were not associated with increased arrhythmia. The authors conclude that (1) rapid sinus tachycardia is frequent in interns while on-call and (2) interns experiencing greater stress and fatigue have more APB/h, VPB/h, and higher grade ventricular ectopy. These data support the notion that stress and fatigue may contribute to arrhythmia in healthy normal subjects.

Adult↗
PubMed1992

Chagas cardiomyopathy and captopril.

Chagas disease is a leading cause of heart failure in Latin America. Sudden death occurs in approximately 40% of patients with heart failure due to Chagas disease. We report a single blind, cross-over trial of prolonged treatment with captopril and placebo in 18 Chagas disease patients with class IV NYHA heart failure. Ventricular dimensions, neurohormones, electrolytes and ventricular arrhythmias were analysed in 11 men and seven women receiving stable doses of digoxin and frusemide who were randomly divided into two intervention groups. Group I patients were given increasing doses of captopril up to 150 mg.day-1 maintained for 6 weeks, group II received the placebo. A 24 h Holter, 2-D echocardiogram, urinary catecholamines, plasma renin and electrolyte determinations were performed at the end of each phase. After a 2-week washout period, the two groups crossed over and another period of 6 weeks was observed. Ventricular arrhythmias were analysed by either Mann-Whitney or the Wilcoxon test. Remaining data were assessed by the Student t-test. A significant reduction in heart rate and urinary catecholamine levels, and enhanced plasma levels of renin, together with a reduction in ventricular couplets was found in the captopril-treated group. We conclude that captopril has a beneficial effect on neurohormones with a subsequently reduced heart rate and diminished incidence of ventricular arrhythmias in patients with Chagas disease. This effect might result in a reduction of mortality caused by the disease, suggesting the need for further investigations.

Adult↗
PubMed1992

Large pericardial effusions in the acquired immunodeficiency syndrome.

The increasing importance of the acquired immunodeficiency syndrome (AIDS) as a cause of large, clinically significant pericardial effusions has not been well documented. To determine the frequency and characteristics of large AIDS-associated pericardial effusions, we reviewed the records of 50 consecutive patients undergoing pericardiocentesis between 1985 and 1990; AIDS was the most common underlying illness and was present in 14 patients (28 percent). The pericardial fluid was diagnostic in three (21 percent) of the 14 cases (one bacterial, one positive for acid-fast bacilli, and one lymphoma). Of the 11 patients with nondiagnostic fluid, one underwent a pericardial biopsy which revealed granuloma consistent with mycobacterial disease, four had active pulmonary tuberculosis (TB), and two responded clinically to anti-TB therapy. Thus, in 8 (57 percent) of the 14 patients with AIDS, there was either definitive or suggestive evidence of mycobacterial disease. We conclude that AIDS is now a common underlying illness associated with large pericardial effusions and that mycobacterial disease may frequently be the etiology.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Total serum cholesterol levels in Asians living in New York City: results of a self-referred cholesterol screening.

Asians historically have low total cholesterol levels and low incidence of coronary heart disease. In performing a coronary heart disease and total cholesterol screening in New York City's Chinatown, we obtained data supportive of previous studies, which focused on Japanese populations and described the influence of environment on total cholesterol. In the present study, Chinese living in Chinatown have higher levels of total cholesterol than would be expected from studies of Chinese living in Shanghai. For every age group examined, Asian-born Chinese living in Chinatown had higher total cholesterol levels than both urban and rural Chinese in Shanghai. In subjects less than or equal to 30 years of age, urban males in Shanghai had cholesterol levels of 160 +/- 34 mg/dL, compared with 206 +/- 38 mg/dL for Asian-born males in Chinatown. For females in the same age category, cholesterol levels were 162 +/- 35 mg/dL vs 224 +/- 45 mg/dL, respectively. Applying National Cholesterol Education Panel (NCEP) guidelines, the distribution of desirable, borderline-high, and high blood cholesterol levels for the Chinese in Chinatown (41%, 35%, and 23%, respectively) were similar to a group of Caucasians screened (42%, 32%, and 26%) and the group recently used to determine the prevalence of high blood cholesterol in American adults (43%, 30%, and 27%). Studies are needed to stratify the risk of coronary heart disease in other groups that traditionally have a low incidence of coronary heart disease, but which now have adopted Western lifestyles.

Adult↗
PubMed1991

Exercise-induced myocardial dysfunction in patients with coronary artery disease with and without angina.

Left ventricular dysfunction during exercise is considered a relatively sensitive marker of ischemia in patients with coronary artery disease. The purpose of this study was to determine whether exercise-induced myocardial dysfunction was more severe in patients with angina than in patients with ischemia without angina. Seventy-seven patients with angiographically documented coronary artery disease and an abnormal left ventricular response to exercise were studied by means of gated blood pool imaging. The arteriographic and functional parameters of 24 patients with angina during exercise testing imaging. The arteriographic and functional parameters of 24 patients with angina during exercise testing were compared with those of 53 patients who were pain free at the time of the test. Both groups were similar with regard to rate of multivessel disease (50% vs 51%, p = NS) and prior myocardial infarction (46% vs 51%, p = NS), as well as age, sex, and history of angina. Mean global ejection fraction remained unchanged (but abnormal) in both groups of patients during exercise. Furthermore, evidence of new regional asynergy during exercise assessed by a five-point scoring system was found to be equally abnormal in the two groups. Results of this study suggest that the severity of exercise-induced global and regional left ventricular dysfunction is independent of the presence of absence of angina during exercise testing.

Angina Pectoris↗
PubMed1991

Skeletal involvement in children who have chronic granulomatous disease.

Chronic granulomatous disease is a rare disorder of the oxidative metabolism of the white blood cells that results in immunodeficiency. In a retrospective review of the records of forty-two patients who had chronic granulomatous disease, we identified thirteen patients who had a total of twenty skeletal infections. Two types of infection were noted: Type 1, which resulted from a direct spread of the infection from an adjacent focus, usually of fungus or mycobacteria, and Type 2, which resulted from hematogenous spread, usually of Nocardia or more common bacteria. The thoracic vertebrae, ribs, and metatarsals were the most commonly involved bones. All four patients in whom the vertebrae were involved had a Type-1 fungal infection. Paresis developed in three of these patients, and two of them died. Antibiotics alone effectively eradicated the infection in only one patient. Wide operative débridement combined with administration of antibiotics was the most successful treatment. Comprehensive preoperative imaging and several cultures are necessary to locate the infection in the bone and to identify the organism.

Adolescent↗
PubMed1989

Exercise-induced pulmonary blood volume changes and diastolic dysfunction of the aged heart.

Impaired diastolic function has been described in healthy elderly subjects. Pulmonary blood volume (PBV) changes with exercise have been associated with left ventricular dysfunction, but not directly related to diastolic abnormalities. Exercise-induced relative changes in PBV were measured using gated blood pool imaging with count density comparisons over the lung in 20 healthy volunteers: 13 elderly, age 76 +/- 5 years and seven young, age 27 +/- 4 years. Serial (first exercise stage, peak exercise, and post exercise) PBV ratios were measured and correlated to peak early filling rate, peak late filling rate, and percent atrial filling obtained from the resting left ventricular time-activity curve analysis. PBV ratios tended to be higher in elderly subjects, but reached significance only at the first stage of exercise (1.04 +/- 0.07 vs. 0.93 +/- 0.10, p less than 0.01). Significant correlations were found between PBV ratios at first exercise stage and peak early filling rate (r = -0.64), peak late filling rate (r = 0.47), and percent atrial filling (r = 0.48). A significant correlation was found between PBV changes at peak exercise and resting diastolic parameters. Exercise-induced PBV changes are associated with left ventricular diastolic dysfunction at rest. Diastolic abnormalities of the aged heart may explain the differential PBV response early into exercise between young and elderly healthy subjects.

Adult↗
PubMed1989

Importance of epidemiology and biostatistics in deciding clinical strategies for using diagnostic tests: a simplified approach using examples from coronary artery disease.

The explosion of costly new medical diagnostic technologies demands a common sense approach to help physicians decide appropriate indications and strategies for use of these tests. This simple, nonmathematical review focuses on the assessment of coronary artery disease, but the approach can be generalized to other medical problems. This clinical approach to diagnostic testing strategies is based on seven sequential questions: 1. What is the clinical probability that this patient has a specific disease characteristic based on clinical data? 2. What is the overall objective for management of this patient based on the overall status of the patient? 3. Most importantly, what specific questions need to be answered about the patient's condition before the physician can recommend the most appropriate management (e.g., whether the patient has coronary disease, whether an anatomic lesion is functionally significant, whether a myocardial region is reversibly ischemic or irreversibly infarcted, whether a particular therapy has had good or bad effects or what is the patient's prognosis)? The key point is for the physician to formulate a specific clinical question about the patient before the test. 4. The physician must then ask how well does the test answer the particular clinical question about the patient. Here the physician needs to understand the sensitivity and specificity of the test, especially because they are influenced by various clinical biases. 5. Next, the physician must ask how to interpret the reliability of a positive or negative test result in the individual patient. This requires understanding predictive value and predictive error of a given result and how they are influenced by the clinical data as described by Bayes' theorem. 6. Next, the physician must ask what further tests or therapies will be recommended for the patient. The physician can estimate in advance how different test results would alter management plans and he can then allow this estimate to help determine indications for the test. There is some controversy concerning whether to use Bayes' theorem or multivariate analysis to estimate the final probability of a disease characteristic. 7. Finally, in this era of quality assurance, professional review and cost containment, it behooves each physician to ask whether the data provided by the particular tests were worth the cost, inconvenience and risk for that particular patient.

Bayes Theorem↗
PubMed1989

Peripartum cardiomyopathy. A role for cardiac stress determinants other than pregnancy?

Peripartum cardiomyopathy is a syndrome of undetermined etiology whose most common initial symptoms are those of congestive heart failure. The syndrome carries a five-year mortality estimated at 40%. Single noxious factors, such as viral infection, have been proposed as direct precipitants of this syndrome, but none have been conclusively linked to it. The cases of two patients with identifiable cardiac stress factors who developed peripartum cardiomyopathy are presented here: one with sepsis complicated by disseminated intravascular coagulopathy and severe anemia, and a second with an otherwise normal pregnancy who engaged in strenuous aerobic exercise throughout the last trimester. A review of previously published cases reveals the frequent association of multiple nonspecific cardiac stress factors that may predispose women to peripartum cardiomyopathy. Various cardiac stress factors may act synergistically with the stress of pregnancy to precipitate peripartum cardiomyopathy in susceptible women.

Adolescent↗
PubMed1988

The role of ischemia and ventricular asynergy in the genesis of exercise-induced ST elevation.

Sixty-five patients with ST elevation were retrospectively studied in order to evaluate the clinical significance and underlying mechanisms of ST-segment elevation during exercise. Of these, 50 patients had previous myocardial infarction (Group I) and 15 patients did not (Group II). Exercise thallium-201 imaging was performed on 30 patients, resting gated blood pool imaging was performed on 33 patients, and 23 underwent cardiac catheterization for clinical indications. When the two groups were compared, patients in Group I had more frequent multivessel disease (9/13 vs. 3/10, p less than 0.05), anterior infarctions (33/50 vs. 4/10, p less than 0.02), while Group II patients had more frequent single-vessel disease (7/10 vs. 4/13, p less than 0.05). For Group I patients, the most common reason for termination of exercise was fatigue and/or dyspnea (35/50 vs. 0/15, p less than 0.05), with an irreversible defect noted in both stress and delayed views on thallium imaging (20/24 vs. 1/6, p less than 0.05). In Group II, the most common reason for termination was angina (15/15 vs. 2/50, p less than 0.001), with reversible thallium defects noted more frequently (4/6 vs. 3/24, p less than 0.01). Thus, we conclude that in patients with Q waves, left ventricular dysfunction rather than ischemia is the mechanism for ST elevation. In these patients angina is rare, but fatigue, dyspnea, multivessel disease, and fixed thallium defects are common. In patients with non-Q-wave exertional ST elevation, ischemia is the rule, manifested by frequent chest pain and reversible thallium defects.

Adult↗
PubMed1988

Serial pulmonary blood volume changes with supine exercise in normal subjects and in coronary artery disease patients.

Relative changes in pulmonary blood volume (PBV) were assessed serially at first stage, peak and post-supine exercise in 13 young normal volunteers and 33 coronary artery disease (CAD) patients. Gated blood pool imaging was used with time corrected count calculation of a region over the lung and comparison to the rest image. In normal subjects, the PBV ratio did not change with exercise but dropped significantly immediately post-exercise. In CAD patients, the PBV ratio increased in the first exercise stage, increased further at peak exercise, and fell significantly following exercise cessation. In the three stages studied, significantly higher PBV ratios were demonstrated in the CAD patients compared to normal subjects, but with significant overlap between the two groups. No significant relation was found between PBV changes and the number of diseased vessels, severity score (Gensini), left ventricular end-diastolic pressure, exercise-limiting symptoms, and left and right ventricular ejection fraction at rest and with exercise. Despite the different response of the PBV ratio to exercise between normals and CAD patients, a significant overlap limits the value of this ratio as a discriminator of the presence, severity or location of CAD.

Adult↗
PubMed1988

Evaluation of right and left ventricular function in hard metal workers.

Ingested cobalt has previously been associated with the development of a congestive cardiomyopathy. Despite occasional reports of cardiomyopathy after industrial exposure to cobalt, this association remains controversial. In a study of 30 cemented tungsten carbide workers with a mean duration of exposure to cobalt of 9.9 +/- 5.3 years radionuclide ventriculography was performed to study right and left ventricular ejection fractions at rest and exercise. For the entire group, rest and exercise biventricular function was normal. There was, however, a weak but significant inverse correlation between duration of exposure and resting left ventricular function (r = -0.40, p less than 0.03). Workers with abnormal chest x ray findings (9/30) had relatively lower exercise right ventricular ejection fractions (45% +/- 6 v 52% +/- 7, p less than 0.02). An inverse relation was also found between rest and exercise right ventricular ejection fraction and severity of parenchymal abnormalities on x ray examination (r = -0.44, p less than 0.01 and r = -0.41, p less than 0.02). Diminished right ventricular reserve was probably due to fibrotic lung disease and early cor pulmonale. Although overt left ventricular dysfunction was not present, prolonged exposure to industrial cobalt may be a weak cardiomyopathic agent with unknown long term significance.

Adult↗
PubMed1987

Relation of late potentials to ejection fraction and wall motion abnormalities in acute myocardial infarction.

A prospective study was performed to determine the relation between quantitative signal-averaged parameters and ejection fraction (EF) and wall motion abnormalities determined by radionuclide ventriculography in patients with acute myocardial infarction (AMI). In 50 patients with AMI, signal-averaging of the surface QRS complex (200 beats; filter frequencies of 40 to 250 Hz and 80 to 250 Hz) was performed and radionuclide ventriculograms were recorded 8 +/- 5 days after AMI. Twenty-five of these patients (50%) had anterior wall AMI, 20 (40%) had inferior wall AMI and 5 (10%) had non-Q-wave AMI. The duration of the low-amplitude signals of less than 40 microV, the signal-averaged QRS complex and the root-mean-square voltage of the terminal 40 ms were determined. In addition to EF determinations, wall motion abnormalities were assessed for the presence or absence of dyskinetic, akinetic and hypokinetic segments. A wall motion score was constructed by separating the left and right ventricles into 21 segments in the anterior, left anterior oblique and lateral views. On the basis of the presence or absence of late potentials, the patients were separated into 2 groups: group I comprised 15 patients (30%) with late potentials and group II 35 patients (70%) without late potentials. The low-amplitude signals (49 +/- 12 vs 24 +/- 8 ms) and the signal-averaged QRS complex (122 +/- 20 vs 96 +/- 15 ms) were significantly longer and the root-mean-square voltage (13.8 +/- 4.9 vs 54.3 +/- 27.4 microV) significantly lower in group I than in group II.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1987

The effect of heart rate and contractility on the measurement of left ventricular mass by 201Tl SPECT.

Left ventricular myocardial mass can be measured by 201Tl SPECT, but the effects of changes in heart rate and contractility have not been determined. We constructed a dynamic computer model simulating the contracting left ventricle. Thirty two summed static views at each of 3 heart rates and 3 ejection fractions were manufactured to simulate a 180 degrees acquisition. Each image set underwent tomographic reconstruction. Left ventricular mass was measured at a fixed percent threshold in each slice. The results show that left ventricular mass varied little with heart rate (4%) and only slightly more (8%) with ejection fraction. Thus, in the normal clinical setting, left ventricular mass measurements by SPECT are minimally affected by the dynamic state of the heart.

Computer Simulation↗