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Biomedical subjects

J Hung

Publications and source records attributed to J Hung.

At least 91 records · Page 5Linked to original sources
PubMed1984

Noninvasive diagnostic test choices for the evaluation of coronary artery disease in women: a multivariate comparison of cardiac fluoroscopy, exercise electrocardiography and exercise thallium myocardial perfusion scintigraphy.

Several diagnostic noninvasive tests to detect coronary and multivessel coronary disease are available for women. However, all are imperfect and it is not yet clear whether one particular test provides substantially more information than others. The aim of this study was to evaluate clinical findings, exercise electrocardiography, exercise thallium myocardial scintigraphy and cardiac fluoroscopy in 92 symptomatic women without previous infarction and determine which tests were most useful in determining the presence of coronary disease and its severity. Univariate analysis revealed two clinical, eight exercise electrocardiographic, seven myocardial scintigraphic and seven fluoroscopic variables predictive of coronary or multivessel disease with 70% or greater stenosis. The multivariate discriminant function analysis selected a reversible thallium defect, coronary calcification and character of chest pain syndrome (p less than 0.05) as the variables most predictive of presence or absence of coronary disease. The ranked order of variables most predictive of multivessel disease were cardiac fluoroscopy score, thallium score and extent of ST segment depression in 14 electrocardiographic leads. Each provided statistically significant information to the model. The estimate of predictive accuracy was 89% for coronary disease and 97% for multivessel coronary disease. The results suggest that cardiac fluoroscopy or thallium scintigraphy provide significantly more diagnostic information than exercise electrocardiography in women over a wide range of clinical patient subsets.

Adult↗
PubMed1984

The Minnesota Diabetes Complications Clinical Trial cognitive functions under long-term maximized and standard metabolic controls.

We have studied memory (Wechsler Memory Scale) and mood states in 20 insulin dependent diabetics under maximized metabolic control (treated with multiple insulin injections daily or insulin pumps) and 12 patients under standard control (treated with one or more injections of insulin daily). Both groups of patients have been enrolled in the Minnesota Diabetes Complications Clinical Trial for two years or longer. The patients in the maximized control group (mean +/- SD) blood glucose 130 +/- 9 mg/dl) had hypoglycemic episodes much more frequently than the patients in the standard control group (mean +/- SD blood glucose 242 +/- 22 mg/dl). Both groups of patients had normal cognitive functions, including a few patients with numerous hypoglycemic episodes. Only one patient who developed a hypoglycemic coma for several weeks has had lasting abnormal cognitive functions including a few patients with numerous hypoglycemic episodes. We conclude that long-term maximized diabetic control (at least 2 years), although not devoid of danger, does not seem to affect cognitive functions in the patients tested according to the parameters used.

Adult↗
PubMed1983

Mechanisms for decreased exercise capacity after bed rest in normal middle-aged men.

The mechanisms responsible for the decrease in exercise capacity after bed rest were assessed in 12 apparently healthy men aged 50 +/- 4 years who underwent equilibrium gated blood pool scintigraphy during supine and upright multistage bicycle ergometry before and after 10 days of bed rest. After bed rest, echocardiographically measured supine resting left ventricular end-diastolic volume decreased by 16% (p less than 0.05). Peak oxygen uptake during supine effort after bed rest was diminished by 6% (p = not significant [NS]), whereas peak oxygen uptake during upright effort declined by 15% (p less than 0.05). After bed rest, increases in heart rate were also greater during exercise in the upright than in the supine position (p less than 0.05). Values of left ventricular ejection fraction increased normally during both supine and upright effort after bed rest and were higher than corresponding values before bed rest (p less than 0.05). After bed rest, increased left ventricular ejection fraction and heart rate largely compensated for the reduced cardiac volume during supine effort, but these mechanisms were insufficient to maintain oxygen transport capacity at levels during upright effort before bed rest. These results indicate that orthostatically induced cardiac underfilling, not physical deconditioning or left ventricular dysfunction, is the major cause of reduced effort tolerance after 10 days of bed rest in normal middle-aged men.

Bed Rest↗
PubMed1983

Prevention of cardiovascular events in variant angina by long-term diltiazem therapy.

In 43 patients with variant angina, the cardiovascular event rate during diltiazem therapy was compared with that in an equal time period before initiation of therapy. Cardiovascular events, that is, myocardial infarction, sudden death and hospitalization for prolonged angina, were decreased significantly (p less than 0.01) during the initial 6 months and mean 19.6 months of therapy. Based on the binomial principle, there were 22 events during the mean 19.6 months before therapy and 2 events during the equal time period on therapy. No patient died during follow-up. The frequency of angina was decreased by 94%. Diltiazem was well tolerated by all patients and no patient had to discontinue therapy because of adverse effects. It is concluded that long-term diltiazem therapy reduces cardiovascular events in patients with variant angina.

Adult↗
PubMed1983

Intracellular bile acid transport in rat liver as visualized by electron microscope autoradiography using a bile acid analogue.

The role of hepatocyte organelles in the intracellular transport and secretion of conjugated bile acids has not been defined. Therefore we studied the transport and observed the subcellular localization of the bile acid analogue 125I-cholylglycyltyrosine by electron microscope autoradiography to further understand the possible compartmentation of bile acids within the hepatocyte. 125I-cholylglycyltyrosine, which retains a net negative charge, exhibited transport properties similar to native bile acids. After portal vein injection, the compound was recovered intact from bile, and the pattern of excretion paralleled that of [14C]cholylglycine. In addition, cholylglycyltyrosine uptake by isolated hepatocytes was sodium dependent. For autoradiography the analogue was injected into the portal vein, and the liver was perfusion fixed after 30 or 300 s. Light microscope autoradiography performed 30 s after isotope injection demonstrated a steep periportal-to-centrilobular gradient for 125I-cholylglycyltyrosine uptake. At 30 s quantitative grain analysis of electron microscope autoradiographs showed predominant labeling of the plasma membrane and the smooth endoplasmic reticulum (SER). The grain distribution over the region of the plasma membrane decreased from 15% at 30 s to 7% by 300 s and was associated with a sevenfold increase in labeling of the Golgi apparatus and a sixfold increase in labeling of the pericanalicular region. Grain distribution over the SER at 300 s was the same as that noted at 30 s. The hypothesis is presented that bile acids move from the sinusoidal plasma membrane to bile via a pathway that includes the SER and Golgi apparatus.

Animals↗
PubMed1983

Exercise conditioning in middle-aged men after 10 days of bed rest.

Of 12 healthy men with a mean age 50 +/- 4 years who had been at bed rest for 10 days, six were randomly assigned to perform individually prescribed physical exercise daily for 60 days after bed rest (exercise group) and six simply resumed their customary activities (control group). Exercise group subjects were significantly more active than control subjects during this interval (p less than .05). Two classic training effects observed in the 60 days after bed rest were significantly larger among exercise than among control group subjects; compared with values immediately after bed rest, heart rate at a constant submaximal workload declined by 36 +/- 11 beats/min in the exercise group vs 16 +/- 8 beats/min in the control group and peak oxygen consumption increased by 4.8 +/- 4.2 vs 2.2 +/- 5.0 ml/kg/min (both p less than .05). Despite these differences in the cardiovascular response to exercise, peak oxygen consumption in both groups returned to before-bed rest levels by 30 days after bed rest, and this was accompanied by significant (p less than .05) and similar increases in resting left ventricular end-diastolic and stroke volumes in both groups. Simple resumption of usual physical activities after bed rest was as effective as formal exercise conditioning in restoring functional capacity to before-bed rest levels.

Bed Rest↗
PubMed1982

Diltiazem for long-term therapy of coronary arterial spasm.

The first 36 patients with coronary arterial spasm treated with diltiazem and followed up at the Stanford University Coronary Artery Spasm Clinic for 6 months or longer are described. There were 13 men and 23 women with a mean age of 50.2 years; the mean duration of angina was 36.1 months. All patients had angina at rest with a good or fail response to sublingual nitroglycerin. During a mean of 17.5 months of diltiazem therapy, the frequency of angina was reduced from a mean of 21.5 to 1.3 attacks/week. This 94 percent reduction in pain frequency occurred when either 240 or 360 mg of diltiazem was administered daily. Sixteen patients required the addition of isosorbide dinitrate to achieve a painfree state. Pain breakthrough occurred a mean of 1.7 times during the 17.5 month follow-up period but tended to be of short duration. Six patients had trace to 1+ pedal edema and no other adverse effects occurred. It is concluded that diltiazem is highly effective and well tolerated for the long-term prophylaxis and treatment of angina in patients with coronary spasm.

Adult↗
PubMed1982

Cardiovascular responses to exercise in middle-aged men after 10 days of bedrest.

The cardiorespiratory response to 10 days of continuous recumbency was assessed in 12 healthy men, age 50 +/- 4 years, who underwent supine and upright graded maximal exercise testing before and after bedrest. The decrease in peak oxygen uptake after bedrest was greater during upright exercise (15.1%, p less than 0.05) than during supine exercise (6.1%, NS): from 25.8 +/- 5.2 to 21.9 +/- 4.5 ml/kg/min and from 24.6 +/- 5.2 to 23.1 +/- 4.8 ml/kg/min. The decrease in submaximal work was also greater in the upright than in the supine position ( p less than 0.05). Ventilation volume was significantly elevated (p less than 0.05) after bedrest during maximal and submaximal effort in both the supine and upright positions. After bedrest, peak heart rate increased 5.7% and 5.9% during supine and upright testing, respectively (p less than 0.05). The increases in rate-pressure product after bedrest were significantly larger (p less than 0.05) during upright than during supine exercise. These results indicate that orthostatic stress is the most important factor limiting exercise tolerance after bedrest in normal middle-aged men. This mechanism also increases the myocardial oxygen demands during submaximal effort after bedrest. Intermittent exposure to gravitational stress during the bedrest stage of hospital convalescence may obviate much of the deterioration in cardiovascular performance that follows myocardial infarction.

Bed Rest↗
PubMed1982

Comparison of cardiovascular response to combined static-dynamic effort, postprandial dynamic effort and dynamic effort alone in patients with chronic ischemic heart disease.

The cardiovascular responses to combined static-dynamic effort, postprandial dynamic effort and dynamic effort alone were evaluated by upright bicycle ergometry during equilibrium-gated blood pool scintigraphy in 24 men, mean age 59 +/- 8 years, with chronic ischemic heart disease. Combined static-dynamic effort and the postprandial state elicited a peak cardiovascular response similar to that of dynamic effort alone; work load 643 +/- 156 and 638 +/- 161 vs 650 +/- 153 kg-m/min, respectively; heart rate 147 +/- 14 and 145 +/- 14 vs 143 +/- 17 beats/min; systolic pressure 195 +/- 26 and 200 +/- 25 vs 197 +/- 25 mm Hg; and rate-pressure product 286 +/- 48 and 292 +/- 55 vs 282 +/- 52. Heart rate, intraarterial systolic and diastolic pressures, rate-pressure product and ejection fraction were similar for the three test conditions at the onset of ischemia and at peak effort. The prevalence and extent of exercise-induced ischemic left ventricular dysfunction, ST-segment depression, angina pectoris and ventricular ectopic activity were also similar during the three test conditions. Direct and indirect measurements of systolic and diastolic blood pressure were highly correlated. The onset of ischemic ST-segment depression and angina pectoris correlated as strongly with heart rate alone as with the rate-pressure product during all three test conditions. The cardiovascular response to combined static-dynamic effort and to postprandial dynamic effort becomes more similar to that of dynamic effort alone as dynamic effort reaches a symptom limit. If significant ischemic and arrhythmic abnormalities are absent during symptom-limited dynamic exercise testing, they are unlikely to appear during combined static-dynamic or postprandial dynamic effort. This simplifies, the task of formulating guidelines for physical effort in patients with chronic ischemic heart disease, especially in providing "clearance" to perform avocational and vocational tasks involving combined static-dynamic and postprandial dynamic effort.

Aged↗
PubMed1981

Influence of heart rate and atrial transport on left ventricular volume and function: relation to hemodynamic changes produced by supraventricular arrhythmia.

The response of the left ventricle to pacing-induced changes in heart rate and the atrioventricular (A-V) relation was examined with equilibrium gated radionuclide ventriculography in 20 patients who had normal ventricular function after surgery for recurrent supraventricular tachycardia. In 10 patients count-derived left ventricular ejection fraction, end-diastolic volume and stroke volume were measured during sinus rhythm and during atrial pacing at 120, 140 and 160 beats/min. In the other 10 patients similar determinations were made during sequential A-V and simultaneous ventricular and atrial (V/A) pacing, both at rates of 100 and 160 beats/min. Left ventricular ejection fraction did not change significantly with atrial pacing (from 0.65 +/- 0.02 [mean +/- standard error of the mean] at a baseline sinus rate of 91 +/- 3 beats/min to 0.62 +/- 0.03 at 160 beats/min) despite a progressive decrease in end-diastolic volume. The percent reduction in end-diastolic volume (% delta EDV) and stroke volume (+ delta SV) from the baseline values was linear and related to change in heart rate (delta HR) as % delta EDV = -0.60 delta HR + 5.19 (r = 0.71; p less than 0.01) and % delta SV = -0.62 delta HR + 5.03 (r = 0.76; p less than 0.001). Left ventricular ejection fraction with baseline sequential A-V pacing at 100 beats/min was 0.67 +/- 0.03 and not significantly altered by either sequential A-V or simultaneous V/A pacing at 160 beats/min. At 100 beats/min, loss of atrial transport with simultaneous V/A pacing resulted in a small reduction in end-diastolic volume from a baseline value of -9.0 +/- 1.9 percent (p less than 0.01) and a nonsignificant reduction in stroke volume of -3.7 +/- 1.6 percent. During simultaneous V/A pacing at 160 beats/min, the reduction in end-diastolic and stroke volumes from the baseline value was -26.6 +/- 3.8 percent and -28.8 +/- 4.3 percent, respectively (both p less than 0.01), but was significantly smaller (-16.1 +/- 3.6 percent and -19.2 +/- 4.1 percent, respectively [p less than 0.05]) when atrial transport was maintained during sequential A-V pacing at the same heart rate. During simultaneous V/A pacing at 160 beats/min, two thirds of the reduction in end-diastolic and stroke volumes from the baseline value was due to the increment in heart rate as assessed from sequential A-V pacing and the other third was due to loss of atrial transport. The data indicate that the hemodynamic consequences of supraventricular tachyarrhythmias in patients with normal ventricular function are due primarily to decreases in ventricular volume as heart rate is increased and atrial contribution is lost rather than to any changes in left ventricular ejection fraction.

Adult↗
PubMed1980

Uremic cardiomyopathy--effect of hemodialysis on left ventricular function in end-stage renal failure.

Left ventricular ejection fraction was measured by radionuclide left ventriculography before and immediately after hemodialysis in 20 uremic patients, 11 of whom presented with congestive heart failure. Ejection fraction and contraction were normal in 15 patients (Group A), six of whom had signs of congestive failure; they were abnormal in five patients (Group B), all of whom were in clinical heart failure. Mean arterial pressure and body weight decreased by a similar amount after dialysis in both groups, and heart rate did not change. In Group A ejection fraction was unchanged by dialysis (0.63 +/- before vs. 0.62 +/- 0.09 after) (mean +/- S.D.), but in Group B it was improved significantly (0.32 +/- 0.04 before vs. 0.44 0.08 after) (P less than 0.01). In three patients in Group B cardiomegaly and ejection fraction returned to normal with long-term hemodialysis. In end-state renal failure, radionuclide left ventriculography can separate patients with circulatory congestion due to fluid overload from patients with left ventricular dysfunction in whom hemodialysis can provide immediate and long-term improvement.

Adolescent↗
PubMed1979

Preoperative and postoperative technetium-99m pyrophosphate myocardial scintigraphy in the assessment of operative infarction in coronary artery surgery.

The incidence of operative myocardial infarction was assessed by electrocardiogram (ECG) and technetium-99m pyrophosphate (99mTc-PyP) myocardial scintigrams in 89 consecutive patients undergoing coronary artery bypass grafting (CABG). Myocardial scintigrams were performed on the day before operation and repeated 2 to 3 days postoperatively. All patients survived operation, with three in-hospital deaths not related to myocardial infarction (mortality rate 3 percent). Operative infarction was assessed to have occurred in four of 89 patients (4 percent). Two had new Q waves and positive scintigrams; one, major ST-T wave changes and a positive scintigram; and the fourth, new Q waves without a positive scintigram. Three further patients (3 percent) had Q waves and positive scintigrams postoperatively, but myocardial infarction was evolving before anesthesia and operation. Twenty-seven of 89 patients (30 percent) were found to have abnormal scintigrams preoperatively. In two patients, both operated upon with evolving myocardial infarction, the scintigram was worse postoperatively. In 13 patients the scintigram was improved after operation. In 12 patients (13 percent) the abnormal preoperative scintigram was unchanged after operation. Preoperative and postoperative myocardial scintigrams and ECG's must be compared to assess the incidence of operative myocardial infarction in patients undergoing CABG.

Adult↗