Biomedical subjects
Publications and source records attributed to R E Patterson.
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A totally occluded coronary vessel subtending a noninfarcted, entirely collateral-dependent myocardial region (NIECDMR) provides an opportunity to assess collateral perfusion during exercise stress. Collateral function was determined by analysis of exercise thallium-201 myocardial perfusion images from 31 patients who had at least one NIECDMR (total 41 NIECDMRs) documented during catheterization. Twenty-two of 41 NIECDMRs manifested exercise-induced perfusion defects and 19 were normally perfused. The exercise-negative NIECDMRs were further categorized: Group 1 NIECDMRs (n = 13) were associated with defects in other myocardial regions supplied by diseased vessels and were considered negative relative to other jeopardized regions; group 2 NIECDMRs (n = 6) were not associated with exercise-induced defects in other myocardial regions, which suggests that collateral perfusion was adequate during maximal exercise. Regions supplied by a diseased left anterior descending coronary artery manifested exercise defects regardless of collaterals, possibly because these regions were larger and required more perfusion. Angiographic indexes of collateral function did not clearly predict exercise results.
To investigate the relation between electrical instability and myocardial infarct size, 20 foxhounds were studied in the awake state 3 to 5 days after closed chest coronary occlusion. Programmed right ventricular stimulation was performed with use of an epicardial electrode. After six paced beats at 10 percent greater than control rate, single and then double extrastimuli were introduced, scanning from late diastole to ventricular refractoriness in steps of 10 to 20 ms. Abnormal responses observed after this provocation were repetitive ventricular response, unsustained ventricular tachycardia, sustained ventricular tachycardia and ventricular fibrillation. Scores for electrical instability were determined for each dog, with higher scores assigned for more hazardous tachyarrhythmias (ventricular fibrillation greater than sustained ventricular tachycardia greater than unsustained ventricular tachycardia greater than repetitive ventricular response) and for those provokable later in diastole. An electrical instability index derived from these scores correlated well with infarct size measured with tetrazolium staining (r = 0.94). When scores were given only for the type of abnormal response elicited, excluding the effect of diastolic timing and the number of extrastimuli or vice versa, there was no significant difference in correlation with infarct size (r = 0.85 versus 0.92). Thus the results demonstrate that inducible electrical instability early after infarction is directly related to infarct size. Further, these data demonstrate the usefulness of an electrical instability index derived from the results of programmed right ventricular stimulation in assessing the severity of ischemic damage to the heart.
Radionuclide gated cardiac blood pool imaging was used to quantify the severity of valve regurgitation in 20 patients, by calculating the ratio of left ventricular to right ventricular stroke counts (end-diastolic minus end-systolic counts in right and left ventricular regions of interest). This ratio (the stroke index ratio) was substantially higher in patients with aortic and mitral regurgitation (3.91 +/- 1.45) than in a control group of 10 patients without regurgitation (1.32 +/- 0.15), p less than 0.001. The stroke index ratio correlated closely (r = 0.947) with measurements of regurgitant fraction derived from simultaneous determinations of total and forward stroke volumes during cardiac catheterization. After aortic and mitral valve replacement in 18 patients, the stroke index ratio decreased from 4.03 +/- 1.46 to 1.38 +/- 0.23 (p less than 0.001), a value not significantly different from that observed in patients without regurgitation. All three patients with residual postoperative regurgitation had a stroke index ratio greater than 2 standard deviations above the mean values for the control group (greater than 1.62), whereas the remaining 15 patients, who had no evidence of regurgitation, had values within the normal range. Therefore, radionuclide gated blood pool scanning provides a noninvasive method of quantifying valve regurgitation and assessing the results of medical or surgical interventions.
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This review is directed at the clinically useful highlights of ultrasound and radionuclide testing in adults with coronary and valvular heart disease, intracardiac shunts, and hypertrophic and congestive cardiomyopathies. As a clinical toto, the radionuclide procedures are currently more useful than ultrasound examination in evaluating patients with known or suspected coronary artery disease. This includes both primary diagnosis and the more accurate estimation of left ventricular function in the presence of segmental asynergy. In patients with valvular disease, the radionuclide procedures are only indirectly useful, while the ultrasound examination is more often diagnostic. These two techniques are complimentary to one another in their ability to noninvasively evaluate and monitor both chamber size and ventricular function in virtually all patients. Recent research involving noninvasive ventricular imaging during physiologic and pharmacologic intervention holds promise for a more sophisticated noninvasive approach to patient management.
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Dietary potassium depletion plus high sodium intake has been reported to elevate resting heart rate and cardiac output and to cause heart failure during exercise. We implanted aortic root electromagnetic flowmeters and aortic and pulmonary artery catheters in five splenectomized dogs condition-trained to run at 9 km/h on an 11% grade for 20 min. Postoperatively, the dogs ate a potassium-enriched diet until completion of control studies; then potassium was withdrawn. During 4 wk of depletion, skeletal muscle potassium fell from 380 +/- 22 to 311 +/- 8 meq/kg, and muscle sodium rose from 142 +/- 14 to 207 +/- 27 meq/kg (mean +/- SE). Cardiac output, aortic blood pressure, heart rate, acceleration of aortic blood flow at rest or during exercise, and the oxygen cost of exercise remained at control levels. Serum creatine phosphokinase at rest, an indicator of rhabdomyolysis, was never elevated. A 24% dietary depletion of muscle potassium in the dog did not change resting and exercise hemodynamics and exercise performance from control.
Sera from bisalbuminemic chicken-turkey hybrids contain two albumins in equal amounts. These are observed as inherited electrophoretic variants and originate from the respective chicken and turkey parents. Sera from the hybrid birds served as a model system by which fractionating and indentification procedures for evaluating serum albumin variants were compared. The two albumins in the hybrid were isolated with preparative polyacrylamide gel electrophoresis (PAGE) and starch block preparative electrophoresis. Isoelectric focusing of the hybrid albumins resulted in the isolation of the turkey albumin. Interference of ampholines prevented the complete isolation of the chicken albumin. The two albumins in the hybrid have identical molecular weights and cannot be identified by sedimentation coefficient, gel filtration behavior, or sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Because of the close relatedness the chicken and turkey albumins in the hybrid cross reacted with rabbit anti-hybrid serum as well as with rabbit anti-chicken anti-turkey sera.
Adenosine and theophylline were linked covalently to oxidized stachyose to produce compounds too large to penetrate cell membranes. These compounds were used in two conscious and six open-chest anesthetized dogs to test the hypothesis that there is an adenosine receptor on the surface of the coronary myocyte. Intracoronary infusions of the adenosine derivative produced dose-dependent coronary vasodilation which was antagonized by theophylline; two types of theophylline derivative antagonized the coronary vasodilatory action of adenosine. Although these results show that both adenosine and theophylline exert their coronary effects at the surface of the smooth muscle cells, this evidence does not establish that they are competing for a common receptor.
We studied phasic right coronary blood flow in well trained normal dogs and dogs with pulmonic stenosis. We installed electromagnetic flow transducers and pressure tubes under anesthesia to monitor right coronary blood flow, cardiac output, central aortic blood pressure, and right ventribular pressure. In normotensive dogs, systolic flow amplitude equaled early diastolic flow levels. The ratio of systolic to diastolic flow at rest was substantially greater in the right coronary bed (36+/-1.3%) than in the left circumflex bed (13+/-3.6%). Right diastolid flow runoff, including the cove late in diastole, resembled left circumflex runoff. Blood flow to the normotensive right (37+/-1.1 ml/min 100(-1) g) and the left (35+/-1.0 ml/min(-1) g) ventricular myocardium indicated equal perfusion of both cardiac walls. Throttling of systolic flow was related directly to the right ventricular systolic pressure level in the dogs with pulmonic stenosis. Retrograde systolic flow occurred in severe right ventricular hypertension. The late diastolic runoff pattern in dogs with pulmonic stenosis appeared the same as for the normotensive dogs. We obtained systolic to diastolic flow ratios of 1/3 the value of normotensive hearts in high and severe pulmonic hypertension. Electrocardiograms and studies of pathology suggested restricted blood flow to the inner layers of the right myocardium in the dogs with severe and high right ventricular hypertension. Normotensive and hypertensive peak hyperemic flow responses were similar, except for an increased magnitude of diastolic flow, with proportionately less systolic flow in hypertensive states.
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BACKGROUND: The Working Well Trial (WWT) emphasized employee participation in the planning and implementation of the health promotion intervention. These participatory strategies were intended to promote institutionalization of the health promotion program and thereby encourage maintenance of the intervention activities. We used data from 107 worksites in the WWT to test whether the nutrition intervention activities were maintained after the research program (i.e., durability) or were adopted by control sites (i.e., diffusion). METHODS: At baseline, upon the completion of the 2-year intervention, and 2 years later, we conducted organization surveys regarding worksite health promotion activities. A nutrition activity score from 0 to 3 was calculated based on availability of nutrition-related programs, self-help manuals or guides, and videos, tapes, brochures, or posters. RESULTS: From baseline to the end of the intervention, there was a significant increase in the nutrition activity score in intervention worksites compared with the controls (P < 0.001). However, 2 years later, there was no difference between intervention and control worksites. In addition, there was no significant increase in the nutrition activity score in control site 2 years after they received the intervention protocols and materials. CONCLUSIONS: Research is needed to develop and test worksite-based interventions to promote institutionalization, durability, and diffusion.
This article reviews selected literature that can be useful for analysis of cost-effectiveness (CE) of diagnostic procedures in patients with known or suspected coronary artery disease. First, a clinical example illustrates some of the issues involved. Four questions are used to organize the material: (1) What is CE analysis? (2) Why should we use CE analysis? (3) Who should perform CE analysis? and (4) How should CE analysis be performed? (1) What is CE analysis? CE analysis differs from cost-reduction or cost-benefit analysis but may encompass cost-utility analysis. Marginal CE emphasizes differences in CE between different strategies. (2) Why should we use CE analysis? Nuclear cardiology depends on the fruits of medical technology, and many policy makers blame technology for escalating costs of health care. This situation requires us to reduce the absolute cost or the increment in cost, as well as to assess the true value of the technology we use. (3) Who should perform CE analysis? A team approach is the best answer to combine the expertise from clinicians and economists. A team approach and detailed definitions of assumptions can help minimize potential bias. (4) How should CE analysis be performed? CE analysis requires formulating important questions, designing alternative scenarios or strategies, selecting values for the numeric variables and including the probability that an event will occur, calculating cost per outcome, and sensitivity analysis of the model. The appropriate goal of CE analysis of the clinical use of cardiac imaging procedures is, first, to help improve patient outcome and, second, to limit costs.
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One hundred four adults completed a multiple choice food label comprehension questionnaire and a food frequency questionnaire. Most respondents were able to accurately rate the fat content of five different foods using only the food label information. However, some underestimated food content for some foods. Also, only 29% correctly selected the definition of % daily value for fat (%DV), as "percent of the maximum daily recommended amount of fat."
PURPOSE: To examine the effect of lifestyle on the effectiveness of a low-intensity dietary intervention. DESIGN: A secondary data analysis was performed using data from the Eating Patterns Study, a randomized controlled trial that found that self-help materials with physician advice was effective in changing dietary intake and behavior. SETTING: Primary care clinics in a large health maintenance organization. SUBJECTS: A total of 2111 patients with a routine scheduled appointment with their primary care physicians. MEASURES: Participants were grouped into one of six health lifestyle patterns based on similarities in baseline measures of alcohol intake, smoking, diet quality, and exercise. Within each lifestyle pattern, changes from baseline in usual fat and fiber intake (based on a food frequency) and a fat and fiber behavior score were compared at 3 months and 12 months for intervention vs. control participants. INTERVENTION: Self-help materials delivered by a physician with advice to change diet. RESULTS: Intervention participants in the fitness lifestyle group made the largest changes relative to controls for each dietary outcome at 3 and 12 months. For intervention participants defined by their alcohol intake or current smoking, either no changes in diet were observed compared with controls, or early changes were not sustained over time. Intervention-control comparisons within the remaining lifestyle patterns showed smaller dietary changes compared with the fitness lifestyle. This finding was similar to previously published results. CONCLUSIONS: This randomized controlled trial had limited power to detect subgroup differences; however, these results suggest that lifestyle patterns may be useful in the development of effective, targeted interventions to change behavior.