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Biomedical subjects

D D Watson

Publications and source records attributed to D D Watson.

At least 127 records · Page 7Linked to original sources
PubMed1980

Shunt detection with the short-lived radioactive gases.

Conventional radionuclide techniques are limited by their inability to deliver noninvasively a compact bolus of radionuclide indicator into the left heart. This can be accomplished by the inhalation of oxygen-15-labeled carbon dioxide. The inhaled carbon dioxide passes freely across the alveolar membrane and enters the carbonate cycle, which, under the accelerating influence of carbonic anhydrase, transfers the oxygen-15 tracer onto water in the pulmonary venous blood. The result is an abrupt tracer delivery to the pulmonary venous system with subsequent tracer input to the left heart at a rate limited only by the pulmonary blood flow. These properties of oxygen-15-labeled carbon dioxide have been used to develop a specialized indicator-dilution method for quantitation of left-to-right cardiac shunt flow. The results agree well with those obtained by oxymetry at cardiac catheterization. In clinical application, the ease and reliability of this technique are remarkable. Its use is presently limited to clinical facilities with the capability for on-line production of the short-lived gases. The techniques provide a good example of the utilization of biologically active radiopharmaceuticals and are a potentially useful source of information about the hemodynamic properties of the central circulatory system.

Carbon Dioxide↗
PubMed1980

Prognostic significance of resting anterior thallium-201 defects in patients with inferior myocardial infarction.

To determine whether Tl-201 scintigraphy performed at rest during the late hospital phase of inferior myocardial infarction can predict subsequent coronary events, 25 patients with historical, enzymatic, and electrocardiographic criteria of transmural inferior infarction underwent serial imaging with computer quantification 7-35 days after admission. All 25 patients had inferior defects, and 13 (52%) also had anterior defects implying stenosis of the left anterior descending coronary artery. The patients were divided into those with inferior and anterior perfusion defects (Group 1) and those with inferior defects alone (Group 2). In Group 1, three patients had persistent defects in the anterior wall and ten had initial defects with redistribution. New or recurrent coronary events--which included new onset or progression of angina pectoris, sudden death, reinfarction, and congestive heart failure--were recorded over an average 7.2 months of followup (range 3-9 mo) for all patients. Ten of 13 (77%) patients in Group 1 had 17 coronary events and four of 12 (33%) patients in Group 2 had six coronary events (p < 0.02). Nine patients in Group 1 and three in Group 2 developed angina (p < 0.03). The apparently increased prevalence in Group 1 of sudden death (8% against 0%), reinfarction (8% against 0%), and congestive heart failure (46% against 25%) was not statistically significant. Thus resting Tl-201 scintigraphy with computer quantification is a highly sensitive method to detect inferior myocardial infarction even in the late hospital phase. Moreover, it appears to identify those patients with inferior infarction at high risk for subsequent coronary events, presumably due to stenosis of the left anterior descending coronary artery.

Aged↗
PubMed1980

Thallium-201 scintigraphy at rest in ischemia and infarction.

Serial imaging of the myocardium in the resting state after intravenous administration of thallium-201 can be employed to differentiate between ischemia or under-perfusion and myocardial infarction or scar. Redistribution of thallium with filling-in of defects on delayed images or rest can be observed in myocardial regions supplied by stenotic coronary arteries (greater than or equal to 70% narrowing). These myocardial segments usually exhibit normal or hypokinetic wall motion. Persistent defects over a two to three hour imaging period at rest correlate highly with Q waves on the electrocardiogram and akinetic or dyskinetic wall motion on ventriculography. Thallium scintigraphy can be successfully utilized for detecting and localizing acutely infarcted myocardium. Sensitivity for infarct detection is higher in the first 24 hours after the onset of chest pain, although with computer-assisted quantitative analysis of images sensitivity for late detection (ten to fourteen days post myocardial infarction) may be improved. Multivessel disease can be predicted in many patients with acute inferior myocardial infarction by demonstrating anteroseptal wall defects with delayed redistribution on rest images prior to hospital discharge. Patients who demonstrate inferior wall persistent defects (infarction) with anterior wall redistribution (hypoperfusion/ischemia) have a worse prognosis characterized by an increased frequency of recurrent angina and infarction compared to the group with only inferior defects. Thallium scintigraphy may also be useful in assessing myocardial infarct size. Patients with large defects during the acute phase of infarction have significantly higher early and late mortality.

Acute Disease↗
PubMed1979

The relationship between treatment modality, demographic characteristics, and staff perceptions concerning their jobs in 26 Philadelphia drug treatment centers.

The staffs of 26 Philadelphia drug treatment centers, representing four major treatment modalities, were interviewed concerning their attitudes and perceptions of treatment and the treatment milieu. By employing canonical correlation, two basic modality contrasts were found that significantly differentiated these attitudes and perceptions: (1) staff in small therapeutic communities tended to manifest more positive attitudes than their counterparts in large methadone maintenance settings, and (2) outpatient drug-free staff tended to be more satisfied and optimistic than detoxification staff.

Adult↗
PubMed1977

Noninvasive detection and quantification of left-to-right shunts in children using oxygen-15 labeled carbon dioxide.

A method for the detection and quantification of left-to-right intracardiac shunts is described which utilizes a single breath inhalation of oxygen-15 labeled carbon dioxide (C15O2). The inhaled gas rapidly crosses the alveolar membrane and the oxygen-15 label is exchanged through the carbonate cycle to form oxygen-15 labeled water within the pulmonary capillary blood. Pulmonary indicator clearance curves are measured by external scintillation probes. A simplified method of shunt flow quantification was developed from indicator dilution principles and used for the analysis of the clearance curves. Inhalation studies were performed with 62 children on the day prior to cardiac catheterization. The presence or absence of left-to-right shunt was confirmed by contrast angiography in all cases. Twenty-six children were found to have no shunts by C15O2 inhalation, oximetry or angiography. Of the 36 with shunts, 34 were detected by C15O2. Two of these were designated as equivocal because they were considered to be less than the threshold of definitive detection by C15O2 (having Qp/Qs less than 1.2); 32 were positive and there were two false negatives with small ventricular septal defects. There were no false positives by C15O2. The correlation coefficient between C15O2 and oximetry values of shunt flow for those patients with proven shunts was 0.82.

Adolescent↗
PubMed1976

A noninvasive technique for the study of cardiac hemodynamics utilizing C15-O2 inhalation.

A new technique for the study of cardiac hemodynamics is described which utilizes single-breath inhalation of C15O2 (T 1/2 = 124 sec.) and the recording of activity vs. time curves with scintillation counters placed externally over the left ventricle and right lung. The results from 10 normal volunteers and 28 patients with acquired or congenital heart disease have been compared to the findings at cardiac catheterization. The technique is safe, rapid, and nontraumatic, and yielded no false positives or negatives in this series.

Aortic Valve↗
PubMed1976

Left heart imaging following inhalation of 15O-cabon dioxide: concise communication.

Accelerator-produced C15O2 (t 1/2 = 124 sec) is a uniquely useful radiopharmaceutical because it can be introduced rapidly and selectively into the left side of the heart by the simple noninvasive process of inhalation and breath-holding. A standard scintillation camera system was used to obtain images of the left heart by this technique. The procedure involves minimal radiation dose to the patient and may be repeated within a few minutes if necessary.

Adult↗