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Biomedical subjects

B F Vandenberg

Publications and source records attributed to B F Vandenberg.

At least 37 records · Page 2Linked to original sources
PubMed1991

Electrocardiographic diagnosis of left ventricular hypertrophy in the presence of bundle branch block.

Autopsy and echocardiographic studies indicate that ECG criteria for LVH tend to maintain their sensitivity in the presence of LBBB, with the exception of left precordial lead criteria alone. With RBBB, ECG criteria for LVH using right precordial S waves and combination criteria of right precordial S waves and left precordial R waves have a marked reduction in sensitivity, whereas left precordial R wave criteria have modestly reduced sensitivity. Limb lead criteria for LVH have increased sensitivity in the presence of RBBB and, to a lesser extent, in the presence of LBBB. Acceptable sensitivity for the diagnosis of LVH in patients with bundle branch block requires a combination of limb and precordial lead voltage criteria and/or other nonvoltage ECG criteria, since the prevalence of LVH in the presence of RBBB or LBBB appears higher than the sensitivity of individual criteria.

Bundle-Branch Block↗
PubMed1991

Myocardial perfusion and contrast echocardiography: review and new perspectives.

Myocardial perfusion can be assessed qualitatively and quantitatively with new ultrasound contrast techniques. This article reviews progress and problems in this area, discussing intracoronary and aortic root injections in animals and humans. The technique has great potential clinical application for the identification of coronary flow reserve, and the assessment of the need for and outcome of coronary revascularization procedures. It may allow direct measurements of regional myocardial perfusion.

Angioplasty, Balloon, Coronary↗
PubMed1990

Effect of age on diastolic left ventricular filling at rest and during inotropic stimulation and acute systemic hypertension: experimental studies in conscious beagles.

"Pharmacologic" stress testing with inotropic stimulation is useful in the detection of coronary artery disease when ventricular dysfunction is provoked. However, abnormal diastolic filling may be masked or mimicked because of the influence of aging, heart rate, and loading conditions. We evaluated age effects on left ventricular filling at rest in young (n = 5) and old (n = 6) purebred beagles that were free of occlusive coronary disease and left ventricular hypertrophy, and we also evaluated age-related differences in left ventricular filling velocities in response to dobutamine and phenylephrine. Pulsed Doppler echocardiography of left ventricular filling velocities was performed at baseline and then after the administration of dobutamine (10 to 20 micrograms/kg/min) infusion. Repeat baseline recordings were obtained and then phenylephrine was administered intravenously in doses of 5 to 25 micrograms/kg/min until systolic arterial pressure increased by at least 30 mm Hg above baseline. At baseline, Doppler echocardiography revealed that there were no significant differences in the early (E) velocity or velocity time interval (VTI), and atrial (A) velocity or the A/E velocity ratio between the young and old groups. However, the A VTI and the A/(A + E) VTI ratio were significantly increased in the old group. With dobutamine administration, the E velocity did not significantly increase from baseline in either group. The E VTI, A velocity and A VTI increased significantly in both groups, but the increases were not different between groups. With phenylephrine infusion there was a significant decrease in the E VTI in the old group but neither the A/E velocity or the A/(A + E) VTI ratio significantly changed from baseline.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1990

Surgical treatment of cardiac myxomas: long-term results.

Between 1965 and 1988, 22 patients underwent 24 operations for cardiac myxomas. Two patients had the complex myxoma syndrome. Mitral valve replacement was required at initial operation in 2 patients. One patient died perioperatively, and 5 others died subsequently. The 16 surviving patients recently underwent evaluation at a mean duration of 9 years after operation. Ten are asymptomatic and 6 have New York Heart Association class II symptoms. Nine patients continue to be employed. Eleven are in sinus rhythm, 3 have permanent pacemakers, and 2 have chronic atrial arrhythmias. Echocardiography showed atrioventricular valve insufficiency in 3 patients and reduced contractility in 4, but no new tumor recurrences. The long-term prognosis of this relatively large group of patients with cardiac myxomas has been good. Patients without the complex myxoma syndrome had no recurrence, whereas 2 patients did require reoperation for mitral valve replacement. Long-term disability and chronic arrhythmias have been infrequent, and functional status and employability of these patients have been very good.

Echocardiography↗
PubMed1990

Tissue characterization of chronic myocardial infarction.

Determination of magnetic resonance (MR) relaxation times (T1 and T2) and ultrasound backscatter are potential methods of noninvasive myocardial tissue characterization. The authors postulated that infarct-related collagen deposition in a canine chronic myocardial infarction model would alter T1 and T2 relaxation times. Further, we sought to compare the changes in T1 and T2 with backscatter measurements. Eight animals were studied 4 to 6 weeks after occlusion of the left anterior descending coronary artery; standard echocardiography showed each to have left ventricular wall motion abnormalities. Time-averaged backscatter and cyclic backscatter variation (at 5 MHz) were measured in the open-chest animal with corresponding normal and infarcted areas undergoing in vitro T1 and T2 measurements (at 20 MHz) and water and hydroxyproline concentration analysis. Significant increases in T2, time-averaged ultrasound backscatter, and hydroxyproline concentration were found in the infarcted myocardium compared with normal muscle. Cyclic variation in backscatter and water content were not significantly different between the two groups. Although backscatter, T2, and tissue collagen content increased in the infarcted myocardium, a significant relationship was not found among these variables.

Animals↗
PubMed1990

Characterization of acute experimental left ventricular thrombi with quantitative backscatter imaging.

Two-dimensional echocardiography is an excellent technique for detecting left ventricular thrombi, however, acute clot is sometimes difficult to differentiate from adjacent myocardium and intracavitary signals. We hypothesized that quantitative assessment of the acoustic properties of acute left ventricular thrombi using a quantitative backscatter imaging system would permit the differentiation of thrombus from adjacent myocardium and intracavitary echoes. Acute, experimental left ventricular thrombi in seven dogs were evaluated with a quantitative backscatter imaging system that allowed the measurement of relative integrated backscatter and cyclic (i.e., diastolic minus systolic) variation in integrated backscatter. Coronary ligation abolished the cyclic variation in relative backscatter that occurred in normal myocardium. The end-diastolic relative backscatter in the thrombus (16.9 +/- 1.3 dB) was significantly higher than in apical myocardium (13.2 +/- 0.6 dB, p less than 0.05). There was no significant difference in the cyclic variation in relative backscatter among thrombus, ischemic myocardium, or intracavitary blood. Thus, the quantitative assessment of the acoustic properties of left ventricular thrombi can be useful in their detection and in the differentiation from myocardium and intracavitary signals.

Animals↗
PubMed1989

Quantitation of myocardial perfusion by contrast echocardiography: analysis of contrast gray level appearance variables and intracyclic variability.

Hand-agitated diatrizoate meglumine/diatrizoate sodium (MD-76) was injected above the aortic valve in seven dogs during two-dimensional echocardiographic imaging to determine the ability of contrast appearance variables (i.e., peak background-subtracted gray level intensity, time to peak contrast appearance and maximal slope of the contrast appearance curve) to predict myocardial blood flow. Regional perfusion was altered by a critical coronary stenosis (around the left anterior descending coronary artery) or by administering intracoronary adenosine (into the left circumflex coronary artery), or both. Changes in regional blood flow between control and interventions were compared with the changes in the contrast appearance variables. In addition, the ability of intracyclic variability of gray level intensity to predict myocardial perfusion was assessed. In the determination of absolute myocardial perfusion, background-subtracted peak gray level intensity and the maximal slope of the appearance curve demonstrated a fair correlation (r = 0.67 and 0.51, respectively, p less than 0.0001). However, time to peak contrast appearance did not correlate (r = 0.14, p = 0.31). Intracyclic variability of gray level intensity at control (before contrast injection) and after contrast injection also did not correlate with perfusion (r = 0.18 and 0.06, respectively). In the evaluation of relative changes in myocardial blood flow, the percent change in the maximal slope of the appearance curve correlated with the percent change in blood flow (r = 0.77, p less than 0.0001). Seven of the eight regions with greater than 3.5-fold increase in blood flow were identified by an increase in maximal slope of greater than 50%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Myocardial risk area and peak gray level measurement by contrast echocardiography: effect of microbubble size and concentration, injection rate, and coronary vasodilation.

Contrast agents were injected via the intracoronary route in eight dogs during two-dimensional echocardiographic imaging to determine the influence of microbubble size and concentration, injection rate, and coronary vasodilation on risk area and peak gray level measurement. At an injection rate at 13 cc/sec, the average background-subtracted peak gray level intensity of hand-agitated diatrizoate meglumine/diatrizoate sodium was significantly (p less than 0.01) higher than that of hand-agitated diatrizoate meglumine/diatrizoate sodium + 0.9% saline, sonicated diatrizoate meglumine/diatrizoate sodium, and sonicated 70% sorbitol. These differences were abolished by the use of 38 cc/sec injection rates and intracoronary injection of adenosine. Perfusion area determinations as assessed by planimetry were unaffected by the contrast agent used, the injection rate, or by intracoronary administration of adenosine. We conclude that risk area measurement by the ultrasound contrast technique is not affected by varying contrast agents, injection rates, or vasodilation. However, peak gray level intensity is variable among contrast agents and may result in variability of time-activity curve analysis.

Animals↗
PubMed1988

Detection, localization, and quantitation of bioprosthetic mitral valve regurgitation. An in vitro two-dimensional color-Doppler flow-mapping study.

The usefulness of two-dimensional color-Doppler flow-imaging (2D Doppler) in the detection, localization, and quantitation of bioprosthetic mitral valve regurgitation is uncertain. Mitral bioprostheses, before and after the creation of transvalvular (n = 33), paravalvular (n = 17), or combined (n = 23) defects, were mounted in a pulsed duplication system (flow rates, 2.5-6.5 l/min; pulse rate, 70 beats/min). An Aloka 880 2D Doppler system (Japan) was used to image the regurgitant jets in the simulated left atrial chamber, analogous to images obtained with transesophageal echocardiography. Jet area was corrected to an estimate of stroke volume: 2D Doppler measurements were divided by [(valve effective orifice area) X (continuous-wave Doppler-determined mean diastolic filling velocity)]/pulse rate. Regurgitant fraction and regurgitant volume were measured by an electromagnetic flow probe. 2D Doppler correctly identified the presence and location of paravalvular regurgitation. In transvalvular and combined transvalvular-paravalvular defects, there were six incorrect interpretations, all having transvalvular regurgitant volumes less than 4 ml/beat. In the presence of transvalvular regurgitation, jet area, length, and width correlated linearly with regurgitant volume (r = 0.82, 0.80, and 0.68, respectively; p less than 0.0001) and regurgitant fraction (r = 0.62, 0.61, and 0.45, respectively; p less than 0.001). Correlations with regurgitant fraction were improved when 2D Doppler measurements were corrected for stroke volume (r = 0.78, 0.79, and 0.67, respectively; p less than 0.0001). Mitral bioprostheses with transvalvular defects were also studied at varying flow rates (3.2-7.5 l/min) and pulse rates (70, 90, and 110 beats/min). The correlation between jet area and regurgitant volume was improved with a second-order polynomial regression (r = 0.93, p less than 0.0001). Our conclusions are that 1) in this in vitro model analogous to transesophageal imaging, 2D Doppler accurately detects and localizes bioprosthetic mitral valve regurgitation; 2) in transvalvular bioprosthetic mitral valve regurgitation, 2D Doppler measurement of jet area has a curvilinear relation with regurgitant volume, and correlation with regurgitant fraction is improved with correction for stroke volume; and 3) in paravalvular bioprosthetic mitral valve regurgitation, correlations between 2D Doppler measurements and regurgitant volumes are weaker, possibly because of jet eccentricity.

Animals↗
PubMed1988

111In-labeled platelet scintigraphy and two-dimensional echocardiography for detection of left atrial appendage thrombi. Studies in a new canine model.

111In-labeled platelet scintigraphy and two-dimensional echocardiography were performed in 40 dogs to determine the ability of the two techniques to detect left atrial appendage thrombi. Thrombi were induced in 33 dogs that were classified into two groups, "acute" or "chronic," according to the time of labeled-platelet injection after thrombus induction. In the acute group (17 dogs), platelets were injected 24 hours after thrombus induction. In the chronic group (16 dogs), platelets were injected 4-8 days after thrombus induction. "Sham" thoracotomies were performed on seven additional control dogs who did not receive thrombin injections. Analog and blood pool-corrected 111In-labeled platelet scintigraphy images were obtained 4-72 hours later. Closed-chest two-dimensional echocardiography was performed before thoracotomy and repeated at the time of scintigraphy. The location and size of each thrombus were verified at autopsy. Two-dimensional echocardiography detected three of 17 acute (mean volume, 1.2 +/- 1.0 cc) and three of 10 chronic (mean volume, 0.4 +/- 0.3 cc; p less than 0.025) left atrial appendage thrombi. 111In-labeled platelet scintigraphy detected all 17 acute thrombi but only two of 10 chronic thrombi. The measured radioactivity levels of the excised thrombi were 1,949 +/- 1,665 cpm/clot/dose in group 1 and 228 +/- 213 cpm/clot/dose in group 2 (p less than 0.005). In this model, 111In-labeled platelet scintigraphy was able to detect acute left atrial appendage thrombi that could not be identified by two-dimensional echocardiography. Both techniques showed poor sensitivity for detection of chronic thrombi. The decline in sensitivity of 111In-labeled platelet scintigraphy for detection of older thrombi is probably due to diminished labeled-platelet incorporation.

Animals↗
PubMedDate not supplied

Acoustic lability of albumin microspheres.

The sonication of human serum albumin produces air-filled microspheres that are used in echocardiographic studies of myocardial perfusion. Recent studies suggest that the microspheres disappear when high pressures are applied, altering the relationship between the administered microsphere dose and the echocardiographic response. Because an ultrasound pulse generates a pressure wave in insonified medium, we hypothesized that with increasing acoustic pulse pressure, the microsphere concentration decreases, hence ultrasonic backscatter decreases. We measured relative integrated backscatter from albumin microspheres diluted in normal saline solution (6152 microspheres/ml) and 5% human plasma protein fraction (24,608 microspheres/ml), with increasing acoustic pulse pressures at the transducer's focus. Backscatter was also measured in normal saline solution with increasing concentrations (up to 15,380 microspheres/ml) of albumin microspheres at an acoustic pulse pressure of 0.11 MPa (1.1 atm). Backscatter and microsphere concentration were related logarithmically: y = 3.38 x 0.32; r = 0.93. Backscatter was unchanged over time at acoustic pulse (peak compression) pressures less than 0.15 MPa (1.5 atm). However, backscatter decreased readily at acoustic pulse pressures greater than 0.33 MPa (3.3 atm), which included any mixing effects. Thus, albumin microspheres are acoustically labile.

Acoustics↗
PubMedDate not supplied

Diagnosis of recent myocardial infarction with quantitative backscatter imaging: preliminary studies.

Acute myocardial ischemia and chronic myocardial infarction may be recognized with ultrasound tissue characterization techniques because of myocardial acoustic changes caused by reduced perfusion and/or collagen deposition. Our purpose was to study the acoustic properties of recent myocardial infarction when the predominating pathologic finding was myocardial edema and leukocytic infiltration. We used a new quantitative backscatter imaging system to study 18 patients 9 +/- 5 days after myocardial infarction (eight patients with anteroseptal myocardial infarction and 10 with inferior myocardial infarction) and 20 normal subjects. The cyclic variation of relative integrated backscatter (end-diastolic minus end-systolic) was calculated from on-line measurements. Standard parasternal long- and short-axis and apical four- and two-chamber views were obtained. In the anteroseptal myocardial infarction group, the cyclic variation of relative integrated backscatter was lower in the septum (1.5 +/- 1.6 dB) than in the posteroinferior wall (3.2 +/- 1.2 dB); however, the sample size of only three patients (of eight patients imaged) in the latter group prevented statistical comparison. The cyclic variation of relative integrated backscatter in the infarcted septum was less than the measurement obtained in the septum of the control group (4.3 +/- 2.4 dB, p less than 0.05). In the inferior infarction group, the cyclic variation of integrated backscatter in the posteroinferior wall (1.8 +/- 1.7 dB) was not significantly different from the measurement obtained in the septum (3.7 +/- 3.6 dB); however, the cyclic variation in the posteroinferior wall was significantly less than that obtained in the control group posteroinferior wall (5.7 +/- 1.7 dB, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Angiography↗