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Biomedical subjects

H R Schelbert

Publications and source records attributed to H R Schelbert.

At least 199 records · Page 11Linked to original sources
PubMed1980

Emission tomography of the heart.

The utility and ultimate role of positron emission computed tomography in health care delivery is difficult to assess at present and needs to be defined in the future. It would seem that with improvements in instrumentation and physiologic indicators, and with the development of compact, reliable, and generator-like cyclotrons, "physiologic tomography" will become more widely applicable. Physiologic tomography of the heart undoubtedly represents an important new tool for investigative studies that will improve our understanding of cardiac physiology in health and disease. The quantiative aspects as well as simultaneous evaluation of more than one segment of myocardial performance, e.g., simultaneous study of mechanical function, blood flow, and metabolism and their interdependency, will provide new insights into myocardial physiology. Because many of the cardiovascular disorders may originate at the cellular or metabolic level, it is hoped that this technique will serve as a means for the early detection of cardiac disease, perhaps at a stage when it is still amenable to therapy.

Animals↗
PubMed1979

Electrocardiographic gating in positron emission computed tomography.

Electrocardiographic (ECG) synchronized multiple gated data acquisition was employed with positron emission computed tomography (ECT) to obtain images of myocardial blood pool and myocardium. The feasibility and requirements of multiple gated data acquisition in positron ECT were investigated for 13NH3, (18F)-2-fluoro-2-D-deoxyglucose, and (11C)-carboxyhemoglobin. Examples are shown in which image detail is enhanced and image interpretation is facilitated when ECG gating is employed in the data collection. Analysis of count rate data from a series of volunteers indicates that multiple, statistically adequate images can be obtained under a multiple gated data collection format without an increase in administered dose.

Carbon Radioisotopes↗
PubMed1978

Myocardial imaging with thallium-201: a multicenter study in patients with angina pectoris or acute myocardial infarction.

A multicenter study of rest and exercise thallium-201 myocardial imaging in 190 patients from five centers was performed. Exercise images were obtained after graded treadmill or bicycle stress with use of five different gamma camera models and were interpreted by the originating investigator without knowledge of other clinical data. Of 42 patients with less than 50 percent coronary stenosis, 4 (10 percent) had a resting image defect, 1 (2 percent) a new exercise defect and 5 (12 percent) either a resting or an exercise image defect, or both. Of 148 patients with coronary stenosis of 50 percent or greater, 64, (45 percent) had an image defect in the study at rest, 90 (61 percent) had new or increased defects after exercise, and 115 (78 percent) had resting or exercise defects, or both. New exercise image defects were more common than exercise S-T depression (90 of 148 [61 percent] versus 62 of 148[42 percent]; P less than 0.01). In a second group of 111 patients with acute myocardial infarction studied at three centers, 90 patients (81 percent) had image defects compared with 71 (64 percent) two had new electrocardiographic Q waves (P less than 0.01). Smaller infractions, as assessed with serum enzyme values, and diaphragmatic infarctions were less commonly detected than larger or anterior infarctions. These findings suggest that myocardial imaging complements the electrocardiographic identification of acute myocardial infarction of exericse-induced myocardial ischemia.

Acute Disease↗
PubMed1978

Right ventricular ejection fraction in patients with acute anterior and inferior myocardial infarction assessed by radionuclide angiography.

We measured right and left ventricular ejection fracttion (EF) from high frequency time-activity curves obtained during the initial passage of an intravenous bolus of 99mTc (Sn) pyrophosphate. In 22 normal controls right ventricular EF averaged 0.52 +/- 0.04 (SD). In 24 acute anterior or lateral infarction patients right ventricular EF was normal (0.56 +/- 0.10), while left ventricular EF was reduced (0.45 +/- 0.10, P less than 0.001 vs controls). In 19 acute inferior infarction patients left ventricular EF also was depressed (0.51 +/- 0.09, P less than 0.001 vs controls). Among 7 of 19 inferior infarction patients with right ventricular by scintigraphy, right ventricular EF was reduced (0.39 +/- 0.05; P less than 0.001 vs normals; P less than 0.01 vs inferior infarction patients without right ventricular involvement). In the latter group right ventricular EF averaged 0.51 +/- 0.10 (NS vs normals). We conclude 1) a single injection of 99mTc (Sn) pyrophosphate can identify right and left ventricular dysfunction and infarct location in acute myocardial infarction, 2) right ventricular EF is well-preserved except when inferior infarction involves the right ventricle.

Acute Disease↗
PubMed1977

Intravenous myocardial imaging performed serially early and late after acute myocardial infarction.

The accuracy and sensitivity of myocardial imaging using intravenous Rb-81 in delineating the extent and subsequent changes in regional myocardial perfusion abnormalities were examined serially in 12 patients one to 510 days after an acute myocardial infaraction. Definite regions of decreased Rb-81 uptake were noted in 10 patients with transmural infarction. There was excellent correlation between the site of perfusion abnormalities, the electrocardiographic infarct location and the region of segmental wall motion disorders. Follow-up studies revealed in 8 of 11 patients a decrease in the extent of the perfusion defect, which was associated with an improvement in the extent and/or severity of regional wall motion disorders. Conversly, wall motion abnormalities did not change in the remaining three patients in whom perfusion abnormalities persisted unchanged. We conclude that intravenous myocardial imaging permits visualization of myocardial perfusion abnormalities early after acute myocardial infaraction. Serial imaging allows detection of changes in the extent of perfusion abnormalities, and, thus, might provide useful information with respect to the patient's prognosis and the effects of therapeutic interventions.

Aged↗
PubMed1977

Tissue distribution studies with radioactive manganese: a potential agent for myocardial imaging.

Manganese, a trace metal, is known to localize in mitochondria. Because mitochondria are abundant in heart muscle, the possible utility of radioactive manganese as a myocardial imaging agent was examined in 25 rats and six dogs. Myocardial uptake of Mn-54 in rats was found to exceed that of thallium-201; myocardium-to-blood ratios averaged 306:1 versus 48:1 for Tl-201. In the dog, uptake of Mn-54 by ischemic myocardium was reduced by 17-75% compared with normal myocardium. Thus, radioactive manganese appears promising as an intravenous myocardial imaging agent, and might be useful in studying the function of myocardial mitochondria by external imaging.

Animals↗
PubMed1976

Serial measurements of left ventricular ejection fraction by radionuclide angiography early and late after myocardial infarction.

The left ventricular ejection fraction was determined serially with radioisotope angiography in 63 patients with acute myocardial infarction. After the peripheral injection of a bolus of technetium-99m, precordial radioactivity was recorded with a gamma scintillation camera and the ejection fraction calculated from the high frequency left ventricular time-activity curve. Since this technique requires no assumptions with respect to left ventricular geometry, it is particularly useful in patients with segmental left ventricular dysfunction. Serial measurements during the first 5 days after hospital admission were made in 50 patients, 30 of whom were studied during the subsequent 2 to 39 months (mean 19.9 months). Late follow-up serial studies were also performed in an additional 13 patients who had only one measurement of the left ventricular ejection fraction during the early postinfarction period. Early after infarction, the left ventricular ejection fraction was normal (more than 0.52) in only 15 of the 63 patients, and averaged 0.52 +/- 0.05 (standard deviation) in the 27 patients with an uncomplicated infarct. The ejection fraction was reduced in 24 patients with mild to moderate left ventricular failure (0.40 +/- 0.05, P less than 0.0001) and in the 12 patients with overt pulmonary edema (0.33 +/- 0.07, P less than 0.0001). In 35 patients the ejection fraction correlated with the mean pulmonary arterial wedge pressure (r = 0.72). In 15 patients with normal left ventricular wall motion by heart motion videotracking, the ejection fraction was significantly higher (0.53 +/- 0.08) than in the 26 patients with regional left ventricular dysfunction (0.41 +/- 0.10, P less than 0.0001). During the early postinfarction period, the left ventricular ejection fraction improved in 55 percent of patients and remained unchanged or decreased in 45 percent. A further increase in the ejection fraction was noted in 61 percent of patients during the late follow-up period. Patients with an initially low or decreasing ejection fraction had a significantly greater incidence of early mortality and left ventricular dysfunction (P less than 0.02) than those whose ejection fraction was normal or improved to normal early after infarction. These data indicate that the ejection fraction is a sensitive indicator of left ventricular function after acute myocardial infarction and that serial measurements are helpful in predicting early mortality and morbidity.

Acute Disease↗
PubMed1976

Uptake of infarct-imaging agents in reversibly and irreversibly injured myocardium in cultured fetal mouse heart.

We studied the specificity of uptake of infarct-imaging agents for reversibly or irreversibly injured myocardium independently of blood flow by using intact beating fetal mouse hearts in organ culture. Reversible injury resulted from deprivation of oxygen and glucose for 4 hours at 37 degrees C; irreversible injury, from similar deprivation at 42 degrees C. At the end of the insult, uptake of 99mTc(Sc)-labeled pyrophosphate, glucoheptonate, or tetracycline was markedly increased in irreversibly damaged and, to a lesser degree, in reversibly injured hearts. After 24 hours of recovery, necrotic hearts accumulated even more pyrophosphate and tatracycline but less glucoheptonate. Uptake of radioiodinated tetracycline increased only in irreversibly injured hearts. Pyrophosphate uptake was not reduced in hearts cultured in calcium-free medium. These finding suggest that 99mTc(Sn)-labeled pyrophosphate, tetracycline, and glucoheptonate preferentially localize in irreversibly damaged myocardium; the 99mTc(Sn) complex modifies the specificity of uptake; and the uptake of 99mTc(Sn)-pyrophosphate appears unrelated to calcium uptake.

Animals↗
PubMed1975

An "air-cart" for scintillation camera positioning.

An air-cart that operates on the laminar air flow principle was designed to permit easy movement of a scintillation camera detector by one operator. Air flow is obtained from the hospital main supply which is available to each room.

Air↗
PubMed1975

Cardiac norepinephrine stores and chronotropic reflex response after thoracotomy.

Although alterations in cardiac reflex activity, as well as in cardiac norepinephrine stores, have been shown following thoracic operations, the physiological relationship between these alterations has not been investigated. Cardiac norepinephrine stores were examined in 17 normal dogs, and in 16 dogs 1-6 wk after a right thoracotomy. The heart rate response to induced arterial hypotension (mean decrease 17-20 mmHg) prior to and following surgery was also examined in 10 dogs. A significant depression in right atrial norepinephrine stores from normal levels of 1.95 +/- 0.13 mug/g to 1.30 +/- 0.25 mug/g (33%) (P less than 0.05) was observed during the first wk following surgery. During the same period the heart rate response to a fall of 17-20 mmHg systolic arterial pressure was clearly reduced from 52.8 +/- 6.9 beats/min to 17.0 +/- 4.8 beats/min (67.8%; P less than 0.05). Right atrial norepinephrine stores at the time of the initial operation and when reflex responses were most markedly depressed demonstrated that the decrease in norepinephrine stores was paralleled by attenuation of the chronotropic response to hypotension.

Animals↗