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Biomedical subjects

A J Buda

Publications and source records attributed to A J Buda.

At least 73 records · Page 4Linked to original sources
PubMed1986

Radionuclide assessment of regional left ventricular function in acute myocardial infarction.

To determine changes in global and regional left ventricular function following acute myocardial function, 17 patients underwent radionuclide angiography at 3 and 10 days post infarction. Five patients had nontransmural myocardial infarction and 12 had transmural infarction (six anterior and six inferior). There were no previous infarctions in 16 (94%) patients. Regional ejection fractions were calculated by dividing the left ventricle into four quadrants using the geometric center of the left ventricle on the end-diastolic frame as a reference point. At 3 days post infarction, 8 of 17 (47%) patients had an abnormality of global left ventricular ejection fraction (LVEF), whereas 16 of 17 (94%) patients had abnormalities of one or more regional ejection fractions (p less than 0.01). Between 3 and 10 days, global LVEF did not change (51% to 49%, p = NS). However, there were significant changes in 23 of 68 (34%) regional LVEFs. These changes did not relate to type, ECG location, creatine kinase (CK) size of infarction, or initial global LVEF. These data suggest that regional LVEF is a sensitive technique for identifying segmental dysfunction associated with myocardial infarction. In addition, significant changes occur in regional LV function during acute myocardial infarction despite stable serial global LV performance.

Adult↗
PubMed1986

Immediate rebound followed by deterioration of regional left ventricular function with coronary reperfusion.

The immediate and early effects of coronary artery reperfusion initiated 1 and 3 hours after coronary artery occlusion were evaluated by two-dimensional echocardiographic measurements of overall and regional left ventricular function. A total of 29 anesthetized open chest dogs underwent one of the following: 1 hour occlusion followed by reperfusion (Group I, n = 9), 3 hour occlusion followed by reperfusion (Group II, n = 12) or 5 hour occlusion without reperfusion (Group III, n = 8). Serial two-dimensional echocardiography was performed at baseline; at 1, 3 and 5 hours of coronary occlusion; within 5 minutes of reperfusion; and at 2 hours of reperfusion. After occlusion, all groups manifested significant (p less than 0.01) increases in left ventricular diastolic and systolic area and decreases in left ventricular area ejection fraction. With coronary reperfusion, there was no improvement in these global variables in Groups I and II. However, immediately after reperfusion, there was improvement in the regional extent of dysfunction (Group I, 138 +/- 35 to 66 +/- 62 degrees, p less than 0.05; Group II, 156 +/- 51 to 85 +/- 77 degrees, p less than 0.05) as well as improvement in the regional degree of dyskinesia (p less than 0.05). These regional improvements were transient and resolved by 2 hours of coronary reperfusion. This immediate rebound of function was not associated with the duration of coronary occlusion, hemodynamic variables or ultimate infarct size. Thus, in the anesthetized open chest dog model, coronary artery reperfusion at 1 or 3 hours produces an immediate but transient improvement in regional systolic myocardial function.

Animals↗
PubMed1986

Characterization of the functional border zone around regionally ischemic myocardium using circumferential flow-function maps.

Previous studies have suggested that there exists a functional border zone in myocardium at the lateral margins of an ischemic area. The functional border zone is normally perfused but is characterized by abnormal contractile function. To define the spatial characteristics of this border zone, circumferential maps of left ventricular function by two-dimensional echocardiography and of coronary flow using radioactive microspheres were generated in 18 dogs at baseline and after circumflex coronary occlusion. Circumferential left ventricular wall thickening was measured in all dogs at 22.5 degrees intervals over 360 degrees. In seven dogs, the pathologic slice corresponding to the two-dimensional echocardiographic image was circumferentially dissected into 16 segments corresponding to 22.5 degrees intervals and a subendocardial myocardial blood flow map was derived. In the other 11 dogs, autoradiography was performed of the pathologic slice corresponding to the two-dimensional echocardiographic image, and the hypoperfusion zone was directly measured. There was no difference between the circumferential extent of hypoperfusion zones by either perfusion measurement technique in the five dogs that had both techniques performed (140 +/- 12 versus 124 +/- 7 degrees, p = NS). The hypofunctional zone by two-dimensional echocardiography was significantly larger than the hypoperfusion zone (174 +/- 4 versus 125 +/- 26 degrees, p less than 0.0005), indicating that a zone of normally perfused but abnormally contracting muscle surrounds the ischemic area. However, this border zone in our model was small, measuring 49 +/- 34 degrees (approximately 8 to 9 mm on either lateral border). This suggests that the functional border zone lateral to ischemic myocardium exists, but is relatively discrete.

Animals↗
PubMed1986

Prevention of subsequent exercise-induced periinfarct ischemia by emergency coronary angioplasty in acute myocardial infarction: comparison with intracoronary streptokinase.

To compare the efficacy of emergency percutaneous transluminal coronary angioplasty and intracoronary streptokinase in preventing exercise-induced periinfarct ischemia, 28 patients presenting within 12 hours of the onset of symptoms of acute myocardial infarction were prospectively randomized. Of these, 14 patients were treated with emergency angioplasty and 14 patients received intracoronary streptokinase. Recatheterization and submaximal exercise thallium-201 single photon emission computed tomography were performed before hospital discharge. Periinfarct ischemia was defined as a reversible thallium defect adjacent to a fixed defect assessed qualitatively. Successful reperfusion was achieved in 86% of patients treated with emergency angioplasty and 86% of patients treated with intracoronary streptokinase (p = NS). Residual stenosis of the infarct-related coronary artery shown at predischarge angiography was 43.8 +/- 31.4% for the angioplasty group and 75.0 +/- 15.6% for the streptokinase group (p less than 0.05). Of the angioplasty group, 9% developed exercise-induced periinfarct ischemia compared with 60% of the streptokinase group (p less than 0.05). Thus, patients with acute myocardial infarction treated with emergency angioplasty had significantly less severe residual coronary stenosis and exercise-induced periinfarct ischemia than did those treated with intracoronary streptokinase. These results suggest further application of coronary angioplasty in the management of acute myocardial infarction.

Adult↗
PubMed1986

Scintigraphic phase analysis of left anterior hemiblock.

Left anterior hemiblock (LAHB) is a relatively common disturbance of ventricular conduction which can be an indicator of early conduction system disease. In an effort to better understand this condition, phase analysis of resting radionuclide ventriculograms (RVG) was used to evaluate five patients with LAHB and six normal patients with particular reference to the phase angle difference between the septum and the postero-lateral wall. All patients had normal ejection fractions and visually normal wall motion on RVG. Visual analysis of phase images showed significant differences between the LAHB and normal patients' LV contraction synergy (p less than 0.03) with a delay in septal contraction versus the postero-lateral wall. Four of five patients with LAHB were outside 2 standard deviations of the normal range. Regional quantitative analysis of phase angle differences between posterolateral and septal walls tended to show this difference between normals and LAHB (p = 0.08) as well. Three of five patients with LAHB were outside 2 standard deviations from the normals' mean. There were no significant differences between the standard deviations, skewness, or kurtoses of phase angle histograms of LAHB versus normal patients. Phase analysis can identify some patients with LAHB by both visual and quantitative analysis. The ability to detect and possibly quantitate subtle conduction abnormalities such as LAHB may result in a better understanding of such conduction system diseases.

Electrocardiography↗
PubMed1986

Failure of superoxide dismutase and catalase to alter size of infarction in conscious dogs after 3 hours of occlusion followed by reperfusion.

Superoxide dismutase (SOD) and catalase (CAT), enzymes that degrade superoxide anion and hydrogen peroxide, respectively, reduce size of infarction in anesthetized, open-chest dogs subjected to coronary occlusion followed by reperfusion. To evaluate potential protective effects of these enzymes in conscious animals, three groups of dogs were instrumented at sterile surgery with a hydraulic occluder on the left circumflex (LCX) coronary artery, sonomicrometers to measure regional wall thickness, and catheters to monitor arterial and left ventricular pressures. Ten to 14 days after surgery, the animals were sedated with morphine sulfate (0.5 mg/kg). The LCX artery was occluded for 3 hr by inflation of the hydraulic cuff. Infusions of SOD (n = 7), CAT (n = 6), or saline (control group, n = 7) were begun 15 min before reperfusion and lasted for 45 min of reperfusion. The doses of SOD and CAT were 5 mg/kg, dissolved in 60 ml of saline, and infused at a rate of 1 ml/min. Myocardial blood flow was measured with tracer-labeled microspheres (15 micron diameter) before occlusion, after 5 to 10 min of occlusion, after 150 min of occlusion, and 5 to 10 min after reperfusion. Size of infarction was measured 24 hr later by dual-perfusion staining with Evans blue and triphenyl tetrazolium. Size of infarction (expressed as a percentage of area at risk) did not differ significantly among the three groups: control, 32 +/- 17% (mean +/- SD); SOD, 38 +/- 17%; CAT, 27 +/- 17%. Hemodynamic parameters and myocardial blood flows (measured before infusion of any agents) were not significantly different among the three groups. Serum SOD levels in SOD-treated dogs were 19 +/- 2 micrograms/ml at the onset of reperfusion and 29 +/- 3 micrograms/ml at the end of the infusion. Blood assays collected after infusion showed a monoexponential decay of SOD levels with a half-life of 22 +/- 6 min. We conclude that myocardial protection by SOD or CAT is model dependent. In conscious dogs subjected to 3 hr of coronary occlusion followed by reperfusion, SOD and CAT failed to alter size of infarction.

Animals↗
PubMed1986

Direct measurement of inner and outer wall thickening dynamics with epicardial echocardiography.

Simple geometric models of the left ventricle and indirect experimental measurements suggest that the inner myocardial wall contributes the largest fraction to total wall thickening. We measured transmural differences in regional wall thickening directly, using an epicardial M mode echocardiographic transducer (6 mm diameter, 5 MHz) placed on the anterior free wall of the left ventricle. Wall thickness was partitioned into inner and outer regions by inserting a waxed, 3-0 suture at different depths within the wall. The suture was used as an intramural echo target that was imaged simultaneously with the endocardium to determine inner and outer fractional contribution to total wall thickness. Data were collected in open-chest dogs at rest, during inotropic stimulation with isoproterenol, and during right heart bypass, which was used to vary cardiac output and preload. Results obtained with this method demonstrated that systolic wall thickness was nonuniform at rest and during each intervention. The fractional contributions to total wall thickening of the inner, middle, and outer thirds of the myocardial wall were estimated from the data to be 58%, 25%, and 17%, respectively. The experimental findings corresponded closely to theoretical predictions, supporting the conclusion that a gradient of thickening exists across the myocardial wall, with the inner portion of the wall contributing the largest fraction to total systolic thickening.

Animals↗
PubMed1986

Gated cardiac MRI: ejection-fraction determination using the right anterior oblique view.

Fifteen adults underwent gated cardiac MR scans in the right anterior oblique position. End-diastolic and end-systolic images were acquired in an imaging plane parallel to the ventricular septum using spin-echo image acquisition on a 0.35-T system. Analysis of ventricular volumes and ejection fractions was performed using the area-length method. These results were correlated with ejection fractions obtained from angiocardiography. The linear regression line obtained for ejection fraction was y = 0.74x + 16 and the r value was 0.789, indicating a reasonable correlation between the two methods.

Adult↗
PubMed1985

Prognostic significance of exercise-induced left ventricular dysfunction in chronic aortic regurgitation.

Twenty-three patients with hemodynamically significant aortic regurgitation (AR) underwent gated equilibrium radionuclide angiography to assess rest and exercise left ventricular ejection fraction (LVEF) before and after aortic valve replacement. Preoperatively, LVEF decreased from 54 +/- 3% at rest to 45 +/- 3% during exercise (p less than 0.001). Two patients died at operation. Postoperatively, after 5.7 +/- 1.6 months, LVEF was 62 +/- 5% at rest and 60 +/- 4% during exercise (difference not significant). Exercise LVEF improved significantly postoperatively (p less than 0.01). The patients were followed for a mean of 30 months (range 1 to 56), after valve replacement and during this period, 13 patients were in functional class I, 5 patients were in class II and 2 patients were in class III. One late death occurred and was unrelated to myocardial failure. Thus, in most patients with AR, exercise LVEF improves after aortic valve replacement. A preoperative decrease in LVEF during exercise in patients with significant AR does not predict a poor postoperative outcome.

Adult↗
PubMed1985

Detection and sizing of myocardial ischemia and infarction by nuclear magnetic resonance imaging in the canine heart.

The usefulness of NMR imaging to size infarcted and hypoperfused, ischemic myocardium was assessed in 16 dogs which underwent coronary artery occlusion and reperfusion. During occlusion, technetium-99 microspheres were injected into the left atrium. Following death, the hearts were excised and underwent NMR imaging with a 0.35 tesla magnet, using multiple spin-echo pulse sequences. The epicardium of the heart was marked to indicate the level of the NMR cross-sectional tomographic image. The heart was subsequently breadloafed into 5 mm sections and the corresponding NMR cross-section was flagged for analysis. Autoradiography was performed to measure the hypoperfused, at-risk zone, and triphenyltetrazolium chloride staining was used to measure infarct size. For the flagged tomographic slice, the size of the NMR abnormality correlated well (r = 0.95), and was comparable to the actual hypoperfused, at-risk zone of the left ventricle. However, NMR estimates of infarct size correlated less well (r = 0.75) with the pathologic measure, and significantly overestimated actual infarct size (p less than 0.005). The T1 and T2 values were consistently increased (p less than 0.0005) in both the hypoperfused and infarct zones, compared to normal myocardium. We conclude that NMR imaging can detect acute myocardial ischemia and infarction, but overestimates infarct size and corresponds better to the area of hypoperfused, ischemic myocardium. In this excised canine heart occlusion-reperfusion model, the NMR abnormality corresponded best to the area including both infarction and the surrounding ischemic region.

Animals↗
PubMed1985

Urinary catecholamines and mitral valve prolapse in panic-anxiety patients.

Free norepinephrine and epinephrine were measured in two consecutive 12-hour urine collections gathered during normal activity and sleep from 23 panic-anxiety patients and 9 normal subjects. Mitral value prolapse (MVP) was found in 7 of 20 patients who had echocardiograms. Mean nighttime norepinephrine and epinephrine excretion in panic-anxiety patients without MVP was significantly higher than that of control subjects, and was significantly higher than that of anxiety patients with MVP. In the daytime, all groups had higher catecholamine (CA) levels, but the differences between the groups were less pronounced. Medication significantly relieved symptoms and was associated with decreased CA levels. Elevated basal CA levels may characterize the subgroup of panic-anxiety patients who do not have MVP.

Adult↗
PubMed1985

Assessment of dysfunction in aortic regurgitation by stress-shortening relationship.

Some patients with aortic regurgitation develop irreversible left ventricular dysfunction. The purpose of this study was to noninvasively examine left ventricular function in patients with aortic regurgitation by determining the end-systolic stress-shortening relationship using M-mode echocardiography. Ten normal volunteers and 10 patients with chronic, isolated aortic regurgitation were studied at rest and following load and inotropic alteration by cold pressor testing. The baseline ejection phase indices of ejection fraction and percent fractional shortening did not distinguish between normals and patients with aortic regurgitation (74.6% +/- 2.8% versus 67.0% +/- 4.2%, P = NS and 37.6% +/- 2.4% versus 31.6% +/- 2.7%, P = NS, respectively.) End-systolic stress was significantly greater in patients with aortic regurgitation both at rest (107.8 +/- 11.6 dynes/cm2 X 10(-3) versus 68.4 +/- 4.8 dynes/cm2 X 10(-3), P less than 0.005) and after cold pressor intervention (122.8 +/- 13.0 dynes/cm2 X 10(-3) versus 80.1 +/- 4.0 dynes/cm2 X 10(-3), P less than 0.005). Normals showed increased fractional shortening in the presence of increasing end-systolic stress. Patients with aortic regurgitation showed decreased fractional shortening during increased stress. This response suggests either left ventricular dysfunction with increasing stress or decreased myocardial contractile reserve after cold pressor inotropic stimulation. End-systolic stress-percent fractional shortening relationship may be a sensitive indicator of early left ventricular dysfunction in patients with aortic regurgitation.

Aortic Valve Insufficiency↗
PubMed1984

Streptokinase thrombolysis in experimental coronary artery thrombosis: pattern of reflow and effect of a stenosis.

We studied recanalization of an obstructed left circumflex coronary artery by streptokinase in open-chest anesthetized dogs. Thrombotic occlusion was induced by a 100 microA anodal current selectively delivered to the intimal surface of the vessel. Intracoronary streptokinase (50,000 U) or saline was infused over a 50-min period beginning at either 30 min or 90 min after occlusion. Continuous recordings were made of antegrade circumflex flow and regional myocardial function, which was quantitated using sonomicrometer crystals in the regions of the left anterior descending and circumflex coronary arteries. In some experiments a fixed stenosis, having no effect on mean circumflex coronary artery blood flow, was placed at the site of subsequent thrombus formation. The presence of a stenosis decreased the weight of occlusive thrombi obtained from nonreperfused saline controls by 40% and increased the proportion of animals successfully reperfused by streptokinase from 13 to 76%. Streptokinase reduced thrombus mass by 44% in animals recanalized in the presence of the stenosis. On the average, reflow was established after 26 min of streptokinase infusion, was less in magnitude than pre-occlusion flow, and was unstable and intermittent, being marked by frequent reocclusions. Initiating treatment at 30 min or 90 min post-occlusion did not influence characteristics of the reflow. Return of myocardial contractility in the ischemic bed was not detected during the immediate reperfusion period in the majority of these experiments.

Animals↗
PubMed1984

Computed tomography of pericardial masses: further observations and comparison with echocardiography.

Eight patients with surgically proven primary intrapericardial masses were evaluated over the past 3 years using a variety of radiologic tests. Dynamic CT prospectively identified the masses in all eight patients, esophagography was positive in four of five patients, chest radiography was prospectively positive in one of eight patients, and echocardiography identified a mass in only one of seven patients. Furthermore, precise CT localization of the masses proved important in surgical management of these patients, suggesting in several instances the need for cardiopulmonary bypass. Although echocardiography is the modality of choice in evaluating potential pericardial effusion, CT should be the preferred diagnostic test for suspected intrapericardial mass lesions.

Contrast Media↗
PubMed1984

Hemodynamic changes during acetate and bicarbonate hemodialysis.

In a crossover, double-blind comparison, circulatory changes induced by hemodialysis with bicarbonate versus acetate dialysate were evaluated at the first exposure as well as after 2 weeks of acclimatization to each dialysate. Hemodialysis with bicarbonate dialysate resulted in only minor changes in blood pressure and left ventricular (LV) function as assessed by M-mode echocardiography. In contrast, the first exposure to acetate resulted in significant decreases in systolic (30 mm Hg) and diastolic (17 mm Hg) blood pressure as well as in LV end-diastolic and end-systolic dimensions (5-6 mm) and a rise in ejection fraction. After acclimatization, tolerance developed for the arterial vasodilatory effects of acetate, but not for the venous vasodilatory effect (persistent decrease in LV end-diastolic dimension). These results indicate that some of the circulatory changes induced by hemodialysis may be related more to the acetate infused than to fluid losses or relative autonomic insufficiency.

Acetates↗
PubMed1983

Noninvasive quantification of jeopardized myocardial mass in dogs using 2-dimensional echocardiography and thallium-201 tomography.

The evaluation of jeopardized myocardial mass is important in defining the effect of interventions during myocardial infarction. To quantitate the in vivo mass at risk, 2-dimensional echocardiography (2-D echo) and thallium-201 single-photon emission computed tomography (SPECT) was performed in 10 closed-chest dogs after circumflex coronary artery occlusion. The 2-D images were manually digitized to compute left ventricular (LV) mass using a modified Simpson's rule algorithm. This measure of LV mass correlated well with the actual LV mass (r = 0.97). Perfused myocardial mass was estimated from thallium SPECT images 4 hours after occlusion using a region-growing algorithm. After the dogs were killed, the jeopardized mass was outlined using a dual perfusion staining technique using triphenyltetrazolium chloride and Evans blue dye. The actual perfused mass was well estimated by the thallium images (r = 0.96). The noninvasively determined mass at risk was calculated as: 2-D mass--thallium SPECT mass, and correlated well with the pathologically determined mass at risk (r = 0.91). Thus, the jeopardized mass may be determined noninvasively by using 2-D echo and thallium-201 tomography. This approach may provide further information regarding the effect of intervention therapy on jeopardized myocardium.

Animals↗