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A J Buda

Publications and source records attributed to A J Buda.

At least 55 records · Page 3Linked to original sources
PubMed1988

Modification of the centerline method for assessment of echocardiographic wall thickening and motion: a comparison with areas of risk.

The ability of the centerline method to discern regional myocardial risk area was evaluated using two-dimensional echocardiographic measurements and coronary artery occlusion in 16 open chest, anesthetized dogs. The centerline method was modified to allow determination of both wall thickening and wall motion at control and during coronary artery occlusion. End-systolic and end-diastolic echocardiographic images were analyzed at 100 equally spaced points around the centerline of the short-axis view of the left ventricle to determine shortening and thickening abnormalities. In vivo risk regions were assessed by microsphere injection during occlusion, and autoradiographic analysis revealed a mean (+/- SD) circumferential risk area of 37.5 +/- 7.7%. Abnormal function was established by three criteria on the basis of the control values for both fractional shortening and wall thickening: 1) less than 2 SD, 2) less than 95% tolerance limits, and 3) dyskinesia. The criterion of less than 2 SD estimated a risk area of 45.9 +/- 16.7% for fractional shortening and 37.2 +/- 16.8% for wall thickening. Although neither value was significantly different from the actual mean value for the risk region, the results for fractional shortening were greater than for wall thickening (p less than 0.01). The less than 95% tolerance limit method significantly underestimated risk area for both shortening (25.6 +/- 15.1%, p less than 0.05) and thickening (19.1 +/- 12.7%, p less than 0.001), as did analysis by dyskinesia (13.1 +/- 12.1% for shortening, p less than 0.001; 20.6 +/- 12.1% for thickening, p less than 0.01). Thus, modification of the centerline method allowed determination of both fractional shortening and wall thickening from echocardiographic images.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Feasibility of high-resolution, intravascular ultrasonic imaging catheters.

A small-aperture, prototype ultrasonic imaging system, typical of the size necessary to be embedded in a catheter, was developed to evaluate the feasibility of intravascular ultrasonic imaging catheters (UICs). The evaluation included in vitro imaging of postmortem samples of human femoral and iliac arteries with the UIC prototype and a high-resolution magnetic resonance (MR) proton imager. Excellent correlations between results from the UIC images, MR images, and tissue specimens were demonstrated. Although the current prototype is too large to be useful in examination of smaller vessels such as coronary arteries, the signal-to-noise ratio and resolution obtained indicate that imaging with intravascular UICs is feasible and may have significant diagnostic value.

Arteries↗
PubMed1988

The effects of a critical stenosis on myocardial blood flow, ventricular function, and infarct size after coronary reperfusion.

Immediate percutaneous transluminal coronary angioplasty has been advocated for patients with a residual stenosis after coronary thrombolysis because of the possibility that the residual stenosis may restrict reflow and thereby increase infarct size. Because there are few experimental data bearing on this issue, we measured left ventricular function, myocardial blood flow, and infarct size in 20 anesthetized open-chest dogs during 2 hr of left circumflex occlusion and 4 hr of reperfusion. Ten animals were reperfused through a critical stenosis of the left circumflex artery (critical stenosis group) and the remaining 10 animals underwent full reperfusion without stenosis (control group). In both groups, a comparable degree of echocardiographic systolic wall thinning was present during occlusion and partial recovery of global and regional left ventricular function in the two groups. Subendocardial blood flow was decreased in the critical stenosis group relative to the control group at 5 min after reperfusion (0.52 +/- 0.16 ml/min/g in the critical stenosis group vs 1.55 +/- 0.32 ml/min/g in the control group, p less than .05) but not at 4 hr after reperfusion, when a reduced reflow response was seen in both groups. No differences in subepicardial blood flow were seen in the two groups of animals. Infarct size was slightly greater in the critical stenosis group than the control group, but this difference was not statistically significant (infarct/risk area ratio: 55.5 +/- 7.8% in the critical stenosis group vs 39.4 +/- 9.7% in the control group, p = .21). A close inverse exponential relationship was seen between infarct size/risk area ratio and subendocardial blood flow during occlusion (r = .89, p = .001). Two control animals had high levels of subendocardial collateral flow (greater than 0.2 ml/min/g); when these animals were excluded from analysis, differences in the infarct size/risk area ratio in the control and critical stenosis groups were less striking: (55.5 +/- 7.8% in the critical stenosis group vs 48.4 +/- 9.6% in the control group). Thus, the presence of a critical stenosis results in restriction of hyperemic blood flow to the subendocardium after reperfusion but does not influence infarct size or early left ventricular functional recovery.

Animals↗
PubMed1987

Pulsed Doppler assessment of left ventricular diastolic filling in coronary artery disease before and immediately after coronary angioplasty.

To determine if left ventricular (LV) diastolic filling abnormalities are detectable by Doppler echocardiography in patients with coronary artery disease (CAD), 34 patients with CAD and 24 normal, age-matched control subjects underwent mitral valve pulsed Doppler examination. At catheterization, all CAD patients had typical angina, at least 70% diameter narrowing of 1 major coronary artery, ejection fraction of 50% or more and no valvular heart disease. Seventeen CAD patients underwent coronary angioplasty and had a Doppler examination 1 day before and 1 day after the procedure. Doppler diastolic time intervals, peak velocities at rapid filling (E velocity), atrial contraction (A velocity) and the ratio peak E/peak A velocities were measured. The following areas under the Doppler velocity envelope and their percentage of the total area were calculated: first third of diastole (0.33 area), triangular area under the peak E velocity (E area), and triangular area under the peak A velocity (A area). Patients with CAD and normal subjects were significantly different (p less than 0.01) in peak E velocity (CAD 0.60 +/- 0.12 m/s, normal 0.68 +/- 0.12 m/s), peak A velocity (CAD 0.59 +/- 0.12 m/s, normal 0.48 +/- 0.11 m/s), ratio peak E/peak A velocities (CAD 1.0 +/- 0.27, normal 1.5 +/- 0.32), A area (CAD 0.052 +/- 0.015 m, normal 0.036 +/- 0.010 m), ratio E area/A area (CAD 1.7 +/- 0.53, normal 2.5 +/- 0.69), and all area fractions. In the CAD patients who had undergone coronary angioplasty, no differences were found in any Doppler index before and immediately after the procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Determination of left ventricular volumes and ejection fraction by nuclear magnetic resonance imaging.

To determine the ability of nuclear magnetic resonance (NMR) imaging to assess left ventricular (LV) volumes and ejection fraction (EF), we studied 24 patients within 48 hours of single-plane LV angiography. In all patients, a transverse, single-plane NMR acquisition technique was employed with LV end-diastolic (ED) and end-systolic (ES) volumes (V) calculated by a modified area-length algorithm. In nine patients, a multislice acquisition technique was employed with LVEDV and LVESV calculated by a Simpson's rule algorithm. NMR-determined LVV and EF correlated reasonably well with angiographic values (LVEDV: r = 0.75; LVESV: r = 0.90; and LVEF: r = 0.76). The single-plane NMR technique significantly underestimated LVEDV (p less than 0.01), whereas no significant difference was demonstrated for LVESV. As a result, angiographic LVEF was significantly underestimated (p less than 0.05). This underestimation is likely related to off-axis imaging and to the geometric constraints of a single-plane algorithm. In comparing multislice NMR to angiographic data, no significant difference was demonstrated for LVEDV, LVESV, or LVEF. Thus, quantitation of LVV and EF with NMR is feasible, and comparison to angiographic volumes is similar to results reported from other noninvasive imaging modalities. Improvement in current acquisition techniques and software should result in further quantitative potential.

Adult↗
PubMed1987

Visualization of myocardial infarction and subsequent coronary reperfusion with MRI using a dog model.

Twelve anesthetized mongrel dogs underwent left thoracotomy with placement of a removable ligature around the left circumflex coronary artery. Following a 3 to 6 hour delay, ECG-gated spin-echo MRI was performed. The ligature was then removed reperfusing the heart, and after a 10-15 min period, MRI repeated. Finally, post-sacrifice images were obtained, and the hearts chemically stained for infarct evaluation. The MR images were subjectively and quantitatively evaluated for visibility of the endocardial border and of the injured myocardium, and for changes after reperfusion. The injured tissue was variably visible in vivo, the major limitation a result of motion blurring and artifact. The abnormal tissue was easily visible on MRI in 11 animals, and not clearly visible in one. The endocardial border was easily seen in 10 animals. The variation of calculated relaxation times was high for both normal and ischemic/infarcted myocardium in the beating hearts (normal: T1 = 566 +/- 288, T2 = 38 +/- 6; injured myocardium: T1 = 637 +/- 250, T2 = 41 +/- 12) in contrast, relatively stationary skeletal muscle measured in the same images had narrower ranges (T1 = 532 +/- 199, T2 = 28 +/- 2). Changes with reperfusion were seen, but not reliably. The infarcted or ischemic zones were easily visible on post-sacrifice images in all animals imaged. Post-sacrifice relaxation times were T1 = 564 +/- 69 msec, T2 = 39 +/- 3 msec for normal heart muscle, and 725 +/- 114, T2 = 47 +/- 5 for ischemic/infarcted tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Superoxide dismutase does not cause scar thinning after myocardial infarction.

Previous studies demonstrated that treatment with superoxide dismutase, a scavenger of superoxide anions, limits the extent of myocardial injury in a canine preparation of regional myocardial ischemia and reperfusion. Little is known, however, about the effects of superoxide dismutase on the healing of a myocardial infarct. Therefore, this study was performed to determine whether treatment with superoxide dismutase during myocardial ischemia impairs formation of scar tissue after infarction. Dogs received 2 hour infusions of superoxide dismutase or albumin (controls) by way of the left atrium beginning 15 minutes before and ending 15 minutes after a 90 minute occlusion of the left circumflex coronary artery. Six weeks later the animals were killed. Two-dimensional echocardiography was performed before surgery and before induced death. Wall thickening in the central ischemic zone was decreased at 6 weeks compared with baseline studies (p less than 0.05), but the decrease was similar for both groups. The hydroxyproline concentrations (microgram/mg dry weight) of the scar tissue in the superoxide dismutase and control groups, respectively, were 35.3 +/- 3.8 and 28.7 +/- 5.0 (p less than 0.05). The ratios of the scar thickness to normal wall thickness were superoxide dismutase 0.91 +/- 0.03 and control 0.89 +/- 0.03 (p greater than 0.05). Thus, superoxide dismutase had no adverse effect on wall thickening or scar formation assessed 6 weeks after myocardial infarction, and may be useful to limit oxygen radical-mediated damage during reperfusion of the ischemic myocardium.

Animals↗
PubMed1987

The effect of inotropic stimulation on normal and ischemic myocardium after coronary occlusion.

During acute myocardial ischemia, there exists a zone of myocardial dysfunction that surrounds the central ischemic area that has been termed the functional border zone. We hypothesized that this nonischemic but dysfunctional myocardium may respond to an inotropic challenge. To address this issue, we studied 11 open-chest dogs during acute left circumflex (LCx) occlusion. Simultaneous two-dimensional echocardiograms and radioactive microsphere injections were used to create circumferential left ventricular flow-function maps at the papillary muscle level. Serial studies were performed at baseline, 15 min after LCx occlusion, and after the infusion of dobutamine during LCx occlusion. After occlusion, wall thickening decreased from 52 +/- 8% (mean +/- SEM) to -5 +/- 5% (p less than .01) in the central ischemic zone. The extent of left ventricular dysfunction measured 170 +/- 11 degrees while the subendocardial hypoperfusion zone was 130 +/- 9 degrees (p less than .05), resulting in a functional border zone of 40 +/- 11 degrees. During the infusion of dobutamine, wall thickening did not change in the central ischemic zone but increased adjacent to the functional border zone (p less than .01) and in the normal zone (p less than .05), reducing the extent of the functional border zone to 19 +/- 16 degrees (p less than .05). After dobutamine, the slope of transition of wall thickening from nonischemic to ischemic zones, measured directly from the left ventricular function map, increased on the free wall border (0.71 +/- 0.11 to 0.95 +/- 0.10, p less than .02) to a greater extent than on the septal border (0.60 +/- 0.08 to 0.73 +/- 0.06, p = .07). We conclude that nonischemic myocardium adjacent to ischemic tissue responds to inotropic challenge, dobutamine produces a significant decrease in the size of the functional border zone, and dynamic changes in wall thickening after inotropic intervention are greater in the functional border zone of the lateral free wall than at the septal border of the ischemic area.

Animals↗
PubMed1987

The functional border zone in conscious dogs.

Studies focusing on the functional border zone have been performed largely with anesthetized, open-chest preparations. Therefore, we instrumented 14 dogs at sterile surgery with sonomicrometers arrayed to measure systolic wall thickening across the perfusion boundary produced by circumflex coronary occlusion. We fitted sigmoid curves to the data to model the distribution of wall thickening impairment as a function of distance from the perfusion boundary, which was delineated with myocardial blood flow (15 micron diameter microspheres) maps. Using this approach, we defined the functional border zone as the distance from the perfusion boundary to 97.5% of the sigmoid curve's nonischemic asymptote. The lateral extent of the functional border zone, measured 10 min and 3 hr after occlusion, was 32 and 28 degrees of circumference, respectively. To evaluate the severity of nonischemic dysfunction, we measured average systolic wall thickening within the functional border zone. It was reduced from 3.69 +/- 1.10 (mean +/- SD) mm to 2.98 +/- 1.07 mm (p less than .01) and 2.74 +/- 1.12 mm (p less than .01) early and late after coronary occlusion. Thus, a narrow functional border zone was evident during circumflex coronary occlusion in conscious dogs. Its lateral extent was limited to approximately 30 degrees (similar to findings in open-chest, anesthetized dogs), severe dysfunction was restricted to the immediate vicinity of the perfusion boundary, and the average severity of nonischemic dysfunction within the functional border zone was mild.

Animals↗
PubMed1987

The physiologic basis of dobutamine as compared with dipyridamole stress interventions in the assessment of critical coronary stenosis.

Noninvasive cardiac imaging with echocardiography or thallium-201 scintigraphy utilizing pharmacologic agents as alternatives to exercise is gaining popularity. We investigated the physiologic rationale underlying the optimal choice of pharmacologic stress for functional versus perfusion imaging. With the use of an open-chest dog model, a critical stenosis of the left circumflex coronary artery was produced with total ablation of hyperemic response to a 15 sec period of complete occlusion. Regional left ventricular wall thickening was assessed by quantitative two-dimensional echocardiography. Regional myocardial blood flow was determined by microspheres in both the flow-restricted left circumflex area and the control area supplied by the left anterior descending artery. Eight dogs received 15 micrograms/kg/min dobutamine intravenously for 10 min, and nine dogs received 0.14 mg/kg/min dipyridamole intravenously for 4 min. Dobutamine induced wall thickening abnormalities in all dogs while dipyridamole induced dysfunction in only 55% of the animals studied (p less than .01). Subendocardial blood flow to the left circumflex area was unchanged after both dobutamine and dipyridamole when compared with baseline blood flow. However, subendocardial blood flow increased markedly after dipyridamole in the control area. Regional subendocardial blood flow ratio (left anterior descending/left circumflex) was 3.74 +/- 0.09 (mean +/- SEM) after dipyridamole versus 1.27 +/- 0.09 after dobutamine (p less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Mitral valve prolapse. Echocardiographic changes during pregnancy.

Mitral valve prolapse (MVP) has been reported to be the most common cardiac disorder in reproductive-age women. The purposes of this prospective investigation were to determine the effect of pregnancy on cardiac function in women thought to have MVP and to determine whether any such changes would adversely affect pregnancy outcome. During a recent three-year period, 43 (1.2%) of 3,582 pregnant women followed in our clinic had a prior diagnosis of MVP without any other cardiac disorder. On closer evaluation, only 21 women (0.6%) had a previous echocardiogram suggestive of MVP. Serial echocardiograms in these women revealed that pregnancy caused either no change or an improvement in the valve prolapse. No cardiac complications were present, and perinatal outcomes were favorable. MVP may be less pronounced during pregnancy, and an echocardiogram late in gestation seems worthwhile to confirm the diagnosis before delivery.

Adult↗
PubMed1986

Diagnosis of exercise-induced left bundle branch block at rest by scintigraphic phase analysis.

Accurate diagnosis of diseases of the ventricular conducting system is essential for their appropriate therapy. Some conduction abnormalities, such as exercise-induced left bundle branch block (EX-LBBB), are not apparent on resting electrocardiograms. Phase analysis of rest and exercise radionuclide ventriculograms (RVG's) was used to compare four EX-LBBB patients with six normal controls. All patients had normal resting electrocardiograms, ejection fractions, and visually normal wall motion. First harmonic phase images were generated reflecting the timing of ventricular contraction. Dynamic phase displays were reviewed and graded in a blinded fashion by three independent experienced observers. Phase angle histograms of the right and left ventricle were determined for both resting and exercise images. The mean phase angle and standard deviation were also calculated for each ventricle. Visual grading of the resting phase images failed to show a significant difference between normal patients and patients with EX-LBBB. Quantitative analysis, however, revealed a significant difference in mean phase angle differences (LV-RV) in resting studies: 0.8 degrees (+/- 1.9 degrees SEM) in normals versus 9.3 degrees (+/- 2.3 degrees SEM) in EX-LBBB patients (P less than 0.03). Exercise accentuated the phase angle differences: 1.8 degrees in normals vs. 31.2 degrees in EX-LBBB patients (P less than 0.001). Quantitative phase analysis of resting RVG's permits the diagnosis of cardiac conduction disease that is not apparent on the resting EKG and may result in better monitoring and treatment.

Bundle-Branch Block↗
PubMed1986

Comparison of two-dimensional echocardiographic wall motion and wall thickening abnormalities in relation to the myocardium at risk.

Previous 2DE studies have suggested that left ventricular wall thickening determinants of regional left ventricular function may be more precise than left ventricular wall motion parameters in the assessment of myocardial ischemia and infarction. To study the relationship between regional wall motion and regional wall thickening abnormalities relative to myocardial ischemia, we performed 2DE in 27 dogs at baseline and following 1 hour of circumflex coronary occlusion. A 2DE circumferential map of regional wall motion and regional wall thickening was generated at 22.5-degree intervals over 360 degrees using a fixed centroid. With the use of three consecutive beats, 95% normal tolerance levels were derived for each individual left ventricular function map. The circumferential extent of left ventricular dysfunction was measured at the curve intercepts of the occluded and normal maps. The left ventricular ischemic area at risk for the corresponding 2DE slice was determined by technetium-99 autoradiography. Following coronary occlusion, left ventricular end-diastolic area increased (p less than 0.0005), left ventricular end-systolic area increased (p less than 0.0005), and left ventricular area ejection fraction decreased (50 +/- 2% to 30 +/- 2%, p less than 0.0005). The circumferential extent of regional wall motion overestimated the area at risk by 77% (226 +/- 11 degrees vs 128 +/- 7 degrees, p less than 0.0005), whereas the circumferential extent of regional wall thickening corresponded to the area at risk (147 +/- 9 degrees vs 128 +/- 7 degrees, p = NS). In addition, the circumferential extent of regional wall motion overestimated regional wall thickening by 54% (p less than 0.0005).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1986

Prognostic significance of vegetations detected by two-dimensional echocardiography in infective endocarditis.

Although 2DE is considered the most sensitive method for detecting vegetations in infective endocarditis, the independent clinical significance of these vegetations continues to be debated. To further examine this, we identified 74 patients who were diagnosed as having infective endocarditis over a 54-month period. The 50 patients who underwent 2DE examination form the basis of this report. Definite vegetations were present in 21 (42%) patients and measured 1.2 +/- 0.2 cm2. The vegetation was localized to the aortic valve in 10 patients, the mitral valve in eight, and the tricuspid valve in three. A major complication, defined as death, new-onset congestive heart failure, major arterial embolus, or valve surgery occurred in 86% of the vegetative endocarditis patients compared to 62% of those without vegetations. Among those patients with vegetations, death occurred in 24%, heart failure in 38%, arterial embolus in 48%, and surgery in 43%. This compared to 7%, 21%, 21%, and 24%, respectively, in those patients without vegetations. These data support the concept that 2DE detection of a vegetation defines a high-risk subgroup of patients with infective endocarditis in whom careful monitoring and aggressive management are warranted.

Adult↗
PubMed1986

Serial assessment of circumferential regional left ventricular function following complete coronary occlusion.

The effect of abrupt coronary artery occlusion on regional left ventricular (LV) function is well known, but serial changes in circumferential regional function over the first few hours have not been extensively investigated. Circumflex coronary artery occlusion was produced in nine closed-chest, conscious dogs and changes in LV circumferential function were assessed using two-dimensional echocardiography (2DE) performed in the short-axis projection at the mid-papillary muscle level. End-diastolic and end-systolic frames were manually digitized and regional area ejection fractions at 22.5-degree intervals were calculated using a fixed diastolic center of mass. Endocardial motion abnormality was measured from a circumferential regional ejection fraction map. The extent of wall motion abnormality was measured as that exceeding 95% confidence limits of normal controls; the degree of dyssynergy was measured as the planimetered area of the extent of wall motion abnormality. Following circumflex coronary artery occlusion, a wall motion abnormality was well defined with a minute of occlusion and its circumferential extent measured 146 +/- 16 degrees with 11 +/- 2 cm2 absolute degree of dyssynergy. These parameters did not change over the course of the coronary artery occlusion. We conclude that circumferential regional abnormalities produced by coronary occlusions are well defined early and do not change over the first 3 hours of acute ischemia and infarction.

Animals↗