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Biomedical subjects

R R Miller

Publications and source records attributed to R R Miller.

At least 235 records · Page 13Linked to original sources
PubMed1981

A new, simplified and accurate method for determining ejection fraction with two-dimensional echocardiography.

A new method to determine left ventricular (LV) ejection fraction (EF) with wide-angle, two-dimensional echocardiography (2-D echo) has been developed using the parasternal long-axis, apical four-chamber and apical long-axis views. End-diastolic and end-systolic measurements of LV short axes at the base and mid-LV cavity in the parasternal long-axis view and at the upper, middle and lower thirds of the cavity in the apical views are made, from which an averaged minor axis at end-diastolic and at end-systole is calculated. Fractional shortening of the LV long axis (delta L) is estimated from apical contraction. Satisfactory 2-D echoes were obtained in 55 of 58 nonselected patients (all three views in 32 patients, two views in 22 and one view in one); 42 of 55 patients had coronary artery disease. EF by 2-D echo was compared with EF by gated cardiac blood pool imaging in all patients (r = 0.927, SEE = 6.7%) and to EF by single-plane cineangiography (angio) in 35 of 55 patients (r = 0.913, SEE = 7.4%). LV dyssynergy was frequently present and involved the apex in 29 of 55 patients. Using angio as the standard for evaluating wall motion at the apex, 2-D echo was 100% sensitive and specific in detecting abnormal apical wall motion. We conclude that EF can be determined accurately with 2-D echo in a large group of patients with and without dyssynergy by a simple method that eliminates the need for planimetry or computer assistance.

Adult↗
PubMed1981

Demonstration of training effect during chronic beta-adrenergic blockade in patients with coronary artery disease.

Attenuation of exercise-induced increases in heart rate and cardiac output by chronic beta-adrenergic blockade has been thought to compromise benefit of exercise training in patients with coronary artery disease (CAD). To assess this important issue, 35 CAD patients were evaluated by a 3-month walk-jog-cycle training program: 14 patients received no beta blocker (group 1), 14 received propranolol, 30-80 mg/day (group 2), and seven patients received propranolol, 120-240 mg/day (group 3). The extent of CAD, resting heart rate before training blood pressure and VO2 max were similar (p = NS) in each group. The maximal exercise heart rate (mean +/- SD, 147 +/- 21 beats/min in group 1 vs 120 +/- 10 beats/min in group 2 and 115 +/- 12 beats/min in group 3 (both p less than 0.05 vs group 1). The VO2 max before training was 25 +/- 5.0 ml/kg/min in group 1 vs 23 +/- 3.2 ml/kg/min in group 2 and 26 +/- 2.8 ml/Kg/min in group 3 (all p = NS). Training consisted of three 1-hour periods per week at a heart rate of 70-85% of the maximal pretraining heart rate. In each group, VO2 increased (p less than 0.05) after training: group 1, 27%; group 2, 30%; group 3, 46%. The double product was unchanged after training (p = NS) in each group. These data indicate that substantial training effects may be achieved in CAD patients despite therapeutic doses of beta blockers and a reduced training HR. Thus, there appears to be no indication to reduce beta blockers in CAD patients engaged in cardiac rehabilitation.

Adrenergic beta-Antagonists↗
PubMed1981

Early post-myocardial infarction treadmill stress testing. An accurate predictor of multivessel coronary disease and subsequent cardiac events.

Limited (heart rate to less than or equal to 120 beats/min) standardized treadmill stress testing was done before hospital discharge in 40 survivors of uncomplicated acute myocardial infarction. Each patient had subsequent coronary arteriography. Twenty-one had inferior, 10, anterior, and nine, nontransmural infarctions; in 30 patients this was their first infarction. A positive electrocardiographic response or angina, or both, occurred in 15 patients and correctly detected most patients with multivessel disease (sensitivity 67%, predictive value 87%) and patients at risk for coronary events: 35% of positive responders admitted for angina in the first month after discharge versus 4% of patients with a negative test (p less than 0.05). During a 7-month follow-up period, 73% of patients with a positive test result developed angina versus 16% of those with negative test results (p less than 0.001). Thus, predischarge post-myocardial infarction limited stress testing correctly identifies the high-risk subset of patients with multivessel coronary disease and thereby allows intelligent selection of patients for early coronary arteriography.

Adult↗
PubMed1981

Associations to contextual stimuli as a determinant of long-term habituation.

A series of experiments was performed to determine whether long-term habituation of the acoustic startle response in rats is mediated by conditioned associations between contextual cues and the test stimulus. Experiment 1 established parameters yielding demonstrable long-term habituation of the startle response. Experiment 2 attempted to overshadow the hypothesized associations to contextual cues by providing a more reliable predictor of the acoustic stimulus. Experiment 3 investigated the effect of changes in contextual cues on long-term habituation. Experiment 4 provided treatments designed to extinguish the hypothesized associations between the context and the habituated stimulus. Experiment 5 sought latent inhibition of the hypothesized association between the contextual cues and the acoustic stimulus. The results of these experiments uniformly failed to support an associative model of long-term habituation of the startle response, but they are consistent with a nonassociative model emphasizing habituation to the entire experimental situation rather than exclusively to the iterated stimulus.

Animals↗
PubMed1980

Hemorrhage from carcinoma of the lung.

During a retrospective analysis of 877 cases of lung cancer, we explored the relationships between cell type, site, cavitation, varying degrees of hemoptysis, and radiation therapy. Massive terminal hemoptysis (29 cases) was found to be significantly associated with cavitated (P less than 0.0001 squamous cell carcinoma (P = 0.0002), ARISING IN EITHER THE RIGHT OR LEFT MAIN BRONCHI (P less than 0.0001). Lesser, nonlethal degrees of hemoptysis (140 cases) were not cell-type associated, occurring in approximately 15% of cases of all major tumor types. Radiotherapy, although employed more frequently in the massive-hemoptysis population, did not appear to be causally related to hemoptysis of any degree. An interesting case, which provoked the above study, is described: a patient with bronchogenic squamous cell carcinoma and terminal hemoptysis due to a tumor fistula between the primary lesion and the left atrial chamber. The forms of cardiac involvement in lung cancer are discussed.

Adenocarcinoma↗
PubMed1980

Clinical effects of parenteral narcotics in hospitalized medical patients.

Of 38,221 hospitalized medical patients monitored by a drug surveillance program, 1821 (4.8 per cent) received morphine, 504 (1.3 per cent) received codeine, 493 (1.3 per cent) received papaveretum, 115 (0.3 per cent) received hydromorphone, and 101 (0.3 per cent) received methadone parenterally. Hydromorphone had an unusually high adverse reaction rate (18 per cent); therefore, it probably should not be used since other equally effective strong analgesics are available. Adverse reactions occurred in 2 per cent of papaveretum recipients, in 4 per cent of methadone and codeine recipients, and in 6 per cent of morphine recipients. Gastrointestinal reactions (primarily nausea, vomiting, and constipation) were most common. Central nervous system disturbances (primarily respiratory depression, drowsiness, and confusion) were second most common. Adverse reactions occurred more often with higher doses of morphine and codeine; the dose-response relationship could not be evaluated for the other three drugs. Life-threatening adverse reactions were reported in 28 patients. Respiratory depression was the most common life-threatening reaction. Most patients with these reactions were seriously ill, and many received other drugs that may have contributed to the event.

Codeine↗
PubMed1980

Improved methodology for generating controlled test atmospheres.

Improved methodology has been developed for generating controlled test atmospheres. Vaporization of volatile liquids is accomplished in a 28 mm (O.D.) glass J-tube in conjunction with a compressed air flameless heat torch, a pressure-sensitive switch, and a positive displacement piston pump. The vaporization system has been very reliable with a variety of test materials in studies ranging from a few days to several months. The J-tube vaporization assembly minimizes the possibility of thermal decomposition of the test material and affords a better margin of safety when vaporizing potentially explosive materials.

Environment, Controlled↗
PubMed1980

Quantification of hyperaemia bordering ischaemic myocardium in experimental myocardial infarction.

To quantify and determine the time course of hyperaemia adjacent to acutely ischaemic myocardium, 19 dogs underwent open-chest coronary-artery occlusion and 4 had sham-occlusion. At 15 min (19 animals) and 45 min (9 animals) post-occlusion regional myocardial blood flow (RMBF) was measured by the radionuclide-labelled microsphere technique. The dogs were sacrificed after 24 hours, the hearts were excised, sectioned into four segments from apex to base, and stained with triphenyl tetrazolium chloride (TTC). Transmural samples were taken from necrotic areas, normal areas, and the zone bordering the infarct. Each sample was divided into an endocardial and epicardial layer. At 15 min post-occlusion RMBF in the border zone was 16% greater than in the normal myocardium (116+/-16 vs 100+/-12 cm3xmin(-1)x100g(-1);P<0.05). In addition, the ratio of endocardial to epicardial flow was lower in the border zone (0.87+/-0.05) compared with normal myocardium (1.01+/-0.02; P<0.05) indicating that the hyperaemia observed was predominantly epicardial. From 15 to 45 min hyperaemic endocardial flow tended to decline: 126 to 108 cm3xmin(-1)x100g(-1) (P<0.05). In four sham-occlusion dogs there were no differences (P>0.05) in RMBF between sites equivalent to those sampled in occluded animals. These studies document a hyperaemic border zone persisting at least 45 min post-occlusion. Hyperaemia appears to be more prominent and of longer duration in the epicardium than endocardium.

Animals↗
PubMed1980

Assessment of pulsed Doppler echocardiography in detection and quantification of aortic and mitral regurgitation.

Pulsed Doppler echocardiography was employed to detect disturbed or turbulent flow diagnostic of aortic or mitral regurgitation. Sensitivity, specificity, diagnostic accuracy, and predictive value were assessed by the independent interpretation and comparison of aortic root angiograms (91 patients) and left ventriculograms (94 patients) to the time interval histogram display of the pulsed Doppler. Sensitivity of Doppler in detecting mitral regurgitation was 94 per cent, with specificity 89 per cent, predictive value 81 per cent, and diagnostic accuracy 90 per cent (32 patients with, 62 without regurgitation). In aortic regurgitation, sensitivity was also 94 per cent, specificity 82 per cent, predictive value 94 per cent, and the diagnostic accuracy was 91 per cent (69 patients with, 22 without aortic regurgitation). Additionally, no Doppler evidence of mitral or aortic regurgitation was present in 20 normal subjects. The aetiology of left-sided valvular regurgitation varied widely, with prosthetic valvular insufficiency being the cause of mitral and aortic regurgitation in seven and 10 patients, respectively. Sixteen of 17 (94%) paraprosthetic leaks were correctly identified by pulsed Doppler. In patients with aortic regurgitation the flow-velocity curve recorded in the ascending aorta frequently showed a negative (or reversed) diastolic component, the magnitude of which (expressed as percentage negative area) correlated significantly with angiographic severity of regurgitation. Thus, pulsed Doppler echocardiography is a highly accurate and objective non-invasive technique for detecting mitral and aortic regurgitation. In aortic regurgitation, estimation of severity is possible from inspection of the Doppler ascending aortic flow velocity curve.

Aortic Valve Insufficiency↗