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Biomedical subjects

B H Brundage

Publications and source records attributed to B H Brundage.

At least 19 recordsLinked to original sources
PubMed1995

Pressure and volume loading of the right ventricle have opposite effects on left ventricular ejection fraction.

BACKGROUND: Left ventricular ejection fraction has been reported to be depressed in patients with right ventricular volume overload (RVVO) due to Ebstein's anomaly and uncomplicated atrial septal defect, whereas it is usually preserved in right ventricular pressure overload (RVPO) due to congenital pulmonic stenosis. In the present study, we examined the hypothesis that the differential timing of active displacement of the ventricular septum into the left ventricle in RVPO (end systole) and RVVO (end diastole) results in opposite effects of RVPO and RVVO on left ventricular ejection fraction. METHODS AND RESULTS: Ten patients with severe tricuspid regurgitation after tricuspid valve resection for endocarditis and 10 patients with primary pulmonary hypertension were studied as models of isolated RVVO and RVPO, respectively. Left ventricular ejection fraction, end-diastolic volume, and regional systolic shortening were measured with the use of echocardiographic techniques in these 20 patients and 10 healthy control subjects. In RVPO, despite marked underfilling of the left ventricle relative to the healthy control subjects (end-diastolic volume, 48 +/- 26 versus 77 +/- 20 mL; P < .02), left ventricular ejection fraction was similar to that of the control subjects (56 +/- 5% versus 60 +/- 4%; P = .07) and only 1 of 10 RVPO patients had an ejection fraction of less than 50%. In contrast, in RVVO the left ventricle was volume replete (end-diastolic volume, 84 +/- 26 versus 77 +/- 20 mL; P = NS), but left ventricular ejection fraction was significantly depressed (51 +/- 4% versus 60 +/- 4%, P < .001) compared with the control subjects, and 4 of 10 RVVO patients had an ejection fraction of less than 50%. Analysis of systolic fractional shortening along two perpendicular short-axis diameters and the mutually orthogonal long axis demonstrated isolated augmentation of fractional shortening in the ventricular septal-to-posterolateral free wall dimension in RVPO (47.4 +/- 13.7% versus 34.2 +/- 13.1%, P < .05) and isolated depression of fractional shortening along that same dimension in RVVO (13.7 +/- 11.8% versus 34.2 +/- 13.1%, P < .001) compared with the control subjects. CONCLUSIONS: End-systolic leftward ventricular septal shift in RVPO results in isolated augmentation of systolic shortening in the septal-to-free wall dimension, whereas end-diastolic leftward ventricular septal shift in RVVO results in isolated reduction in systolic shortening in the septal-to-free wall dimension. As a result, despite relative underfilling of the left ventricle in RVPO, resting left ventricular ejection fraction is preserved, whereas ejection fraction is depressed for the volume-replete left ventricle of patients with RVVO.

Adolescent↗
PubMed1995

Racial differences in coronary calcium prevalence among high-risk adults.

A total of 1,461 asymptomatic high-risk adult subjects were studied with digital subtraction fluoroscopy and conventional cinefluoroscopy to detect coronary calcium. Ethnicity and risk factor data were recorded. No subject had a history or electrocardiographic evidence of prior myocardial infarction. The prevalence of coronary calcium by digital subtraction fluoroscopy was high (58%). Substantial ethnic differences in prevalence were noted: 36% of African American subjects, 60% of Caucasian subjects, and 60% of Asian American subjects had definite radiographic evidence of coronary calcium. The difference in prevalence between African American and other subjects was significant (p < 0.0001) by chi-square test for all 3 races. These differences persisted in the unsubtracted cinefluoroscopic images (p < 0.0001) and after controlling for age, gender, and other risk factors (p = 0.003). After 20 +/- 11 months of follow-up, African Americans had more coronary artery disease events (13%) than Caucasians (6%) or Asian Americans (5%) (p = 0.04). Thus, African Americans have a significantly lower prevalence of coronary calcium than do Caucasians or Asian Americans. Based on the follow-up results, these differences in prevalence are not explained by differences in coronary artery disease risk.

Aged↗
PubMed1995

Beyond perfusion with ultrafast computed tomography.

Ultrafast computed tomography (CT) has been available for the clinician for nearly 10 years. Although cost, as well as availability of competing technologies, have limited its application, several investigative groups have demonstrated the feasibility of measuring regional myocardial blood flow by this method. Ultrafast CT provides accurate measurements when myocardial blood flow is normal or reduced. However, when flow is increased (e.g., by pharmacologic vasodilation), the technique underestimates flow. (This can apparently be corrected by using a complex curve-fitting technique.) Direct injection of contrast medium into the aorta distinguishes differences in endocardial and epicardial blood flow. Although imaging of myocardial perfusion has proven clinical value, there is a need for new noninvasive approaches for detecting silent coronary atherosclerosis before coronary events occur. Here it is possible to make use of the close association between coronary atherosclerosis and coronary intimal calcium, recognized over 35 years ago. Even though the amount of coronary calcium is a function of age, individuals with coronary artery disease usually have greater amounts, and the greater the number of coronary vessels with calcium, the greater the likelihood of obstructive coronary disease. Ultrafast CT has proven value for visualizing coronary calcium. No contrast medium is required and radiation exposure is approximately 425 mrads.

Coronary Circulation↗
PubMed1995

Right ventricular mass measurement by electron beam computed tomography. Validation with autopsy data.

RATIONALE AND OBJECTIVES: Validation of right ventricular mass quantitation by electron beam computed tomography in humans has not been performed. The ability of electron beam computed tomography to accurately determine the septal component of the right ventricle also has not been determined. This article addresses both issues. METHODS: Twenty human adult hearts obtained at autopsy were scanned by electron beam computed tomography in a short-axis projection. Planimetry of the right ventricular free wall and septal components of each slice was performed and summed to determine right ventricular mass. These measurements were compared against comparable measurements obtained by autopsy weights of the hearts. RESULTS: Right ventricular free wall weights by electron beam computed tomography (53.9 +/- 18.4 g) correlated well (slope = .92, r = .92, standard error of the estimate = 7.4 g, P < .001) with autopsy weights (55.8 +/- 18.4 g). Right ventricular septal weights by electron beam computed tomography (6.1 +/- 2.3 g) correlated poorly (slope = .04, r = .11, standard error of the estimate = 2.4 g, P = .65) with autopsy weights (13.9 +/- 6.3 g). CONCLUSIONS: Electron beam computed tomography quantitation of right ventricular mass is accurate in humans if only the free wall and not the septal component is utilized.

Aged↗
PubMed1995

Myocardial cysticercosis detected by ultrafast CT.

Cysticercosis can affect any organ of the body although central nervous system manifestations are the most common. Cysticercosis involving the myocardium is extremely rare and is usually diagnosed postmortem. We report a case of cysticercosis involving the myocardium diagnosed antemortem using ultrafast CT.

Cardiomyopathies↗
PubMed1994

Application of ultrafast computed tomography for diagnosis of perivalvular abscesses. Surgical implications.

The presence of a perivalvular abscess is associated with an increased risk of morbidity and mortality with valve replacement and can require extensive debridement and reconstructive procedures. An accurate noninvasive method for preoperative diagnosis may hasten operation and aid in preoperative and surgical management. Two cases are presented in which ultrafast computed tomography accurately identified perivalvular abscesses not detected on two-dimensional transthoracic echocardiography and guided operative intervention.

Abscess↗
PubMed1992

Effects of exercise test results on physician perceptions of coronary artery disease probability using a threshold analysis.

The incremental diagnostic value of exercise electrocardiographic testing compared with clinical data alone in the diagnosis of coronary artery disease (CAD) was found to be of limited value in a previous study. That study used a computer algorithm for diagnosing disease. Thus, the strict use of the results apply only to computerized disease diagnosis rather than physicians' diagnoses. The aim of the present study was to determine whether exercise test data improve a physician's ability to detect the presence or absence of CAD and 3-vessel or left main CAD, and whether the data effect the decision to perform angiography. The study sample comprised a data base of 312 patients whose clinical data, exercise test results and coronary anatomy were known. Individual cases were presented to 8 cardiologists with and without exercise data. The cardiologists provided estimates of disease probability and were asked whether they would request coronary angiography. Receiver-operating characteristic curves and goodness-of-fit analysis showed better discrimination and calibration of the estimates for the presence of CAD and 3-vessel/left main CAD after exercise test results were known. Individualized probability thresholds for deciding whether to request angiography were determined for each physician. Forty-three percent of patients crossed greater than or equal to 1 threshold, with 64% of the crossings in the correct direction. For estimating the presence of any CAD, 84% of crossings from below to above a threshold were correct, whereas only 36% from above to below were correct. For 3-vessel/left main CAD, 36% of crossings from below to above a threshold were correct, whereas 88% from above to below were correct.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Angiography↗
PubMed1992

Regression of left ventricular mass in systemic hypertension.

The importance of treatment in systemic hypertension and cardiovascular morbidity and mortality has been established. Although systemic hypertension is the most important factor in the pathogenesis of left ventricular hypertrophy, other factors such as catecholamines and renin-angiotensin system may be involved. Increased left ventricular mass causes reduction in coronary reserve and may lead to acute ischemic events. Equally efficacious antihypertensive agents may have diverse effects on left ventricular hypertrophy and left ventricular function. New tomographic techniques with improved spatial resolution are emerging in the evaluation of left ventricular mass and may therefore provide better assessment of changes in left ventricular mass. With improved measures of left ventricular mass the question as to whether regression of left ventricular mass provides an additional benefit beyond control of blood pressure in hypertensive individuals may be finally answered.

Antihypertensive Agents↗
PubMed1992

Ultrafast CT and the cardiovascular system.

Ultrafast computed tomography (CT) is a new imaging technique that relies on electron beam technology. Its rapid image acquisition speeds make it ideal for evaluating the cardiovascular system. The high-resolution, flow, and cine-modes are unique and provide complimentary information about cardiovascular anatomy, function, and flow dynamics. Ultrafast CT can provide quantitative measurements of cardiac output, ejection fraction, ventricular volumes, and ventricular mass as well as evaluation of segmental cardiac function. This technique can be used to assess coronary artery bypass graft patency as well as to screen for coronary artery calcium. Intracardiac thrombus or tumor, valvular disease, and disorders of the pericardium can be evaluated and characterized using ultrafast CT. The diagnosis of congenital lesions of the heart and great vessels is facilitated by this imaging modality, which can help determine complex anatomic abnormalities and quantitate shunt lesions. Acquired lesions of the great vessels, such as aortic dissection and aneurysm, can be diagnosed by ultrafast CT, which can also be used for serial examination and conservative management.

Heart↗
PubMed1992

Doppler echocardiographic demonstration of the differential effects of right ventricular pressure and volume overload on left ventricular geometry and filling.

To compare the effects of isolated right ventricular pressure and volume overload on left ventricular diastolic geometry and filling, 11 patients with primary pulmonary hypertension, 11 patients with severe tricuspid regurgitation due to tricuspid valve resection and 11 normal subjects were studied with use of Doppler echocardiographic techniques. Right ventricular systolic overload in primary pulmonary hypertension resulted in substantial leftward ventricular septal shift that was most marked at end-systole and early diastole and decreased substantially by end-diastole. Right ventricular diastolic overload after tricuspid valve resection resulted in maximal leftward ventricular septal shift at end-diastole sparing end-systole and early diastole. The early diastolic distortion of left ventricular geometry associated with right ventricular pressure overload resulted in prolongation of isovolumetric relaxation of the left ventricle (129 +/- 39 ms) and a reduction in early diastolic filling compared with values in normal subjects. Late diastolic distortion of left ventricular geometry associated with right ventricular volume overload had no influence on the duration of left ventricular isovolumetric relaxation (52 +/- 32 ms) but caused a reduction in the atrial systolic contribution to late diastolic filling of the left ventricle compared with values in normal subjects. In patients with right ventricular pressure overload, 52 +/- 16% of left ventricular filling occurred in early diastole compared with 78 +/- 11% in patients with right ventricular volume overload (p less than 0.001). The differential effects of systolic and diastolic right ventricular overload on the pattern of left ventricular filling appear to be related to the timing of leftward ventricular septal displacement.

Adult↗
PubMed1991

Survival in patients with primary pulmonary hypertension. Results from a national prospective registry.

OBJECTIVE: To characterize mortality in persons diagnosed with primary pulmonary hypertension and to investigate factors associated with survival. DESIGN: Registry with prospective follow-up. SETTING: Thirty-two clinical centers in the United States participating in the Patient Registry for the Characterization of Primary Pulmonary Hypertension supported by the National Heart, Lung, and Blood Institute. PATIENTS: Patients (194) diagnosed at clinical centers between 1 July 1981 and 31 December 1985 and followed through 8 August 1988. MEASUREMENTS: At diagnosis, measurements of hemodynamic variables, pulmonary function, and gas exchange variables were taken in addition to information on demographic variables, medical history, and life-style. Patients were followed for survival at 6-month intervals. MAIN RESULTS: The estimated median survival of these patients was 2.8 years (95% Cl, 1.9 to 3.7 years). Estimated single-year survival rates were as follows: at 1 year, 68% (Cl, 61% to 75%); at 3 years, 48% (Cl, 41% to 55%); and at 5 years, 34% (Cl, 24% to 44%). Variables associated with poor survival included a New York Heart Association (NYHA) functional class of III or IV, presence of Raynaud phenomenon, elevated mean right atrial pressure, elevated mean pulmonary artery pressure, decreased cardiac index, and decreased diffusing capacity for carbon monoxide (DLCO). Drug therapy at entry or discharge was not associated with survival duration. CONCLUSIONS: Mortality was most closely associated with right ventricular hemodynamic function and can be characterized by means of an equation using three variables: mean pulmonary artery pressure, mean right atrial pressure, and cardiac index. Such an equation, once validated prospectively, could be used as an adjunct in planning treatment strategies and allocating medical resources.

Adult↗
PubMed1991

Measurement of myocardial blood flow by UFCT: towards clinical applicability.

This review is designed to be a summary of the research conducted towards establishing ultrafast CT as a clinically appropriate tool for measuring myocardial blood flow. The methods and techniques used in the animal validation studies are presented. The results will be critically analyzed and the conclusions discussed. The proposed improvements to flow calculation algorithms will also be addressed. Technical improvements and experimental research needed will also be addressed.

Algorithms↗
PubMed1991

Reproducibility of left ventricular myocardial volume and mass measurements by ultrafast computed tomography.

Ultrafast computed tomography has been reported to be an accurate method of measuring left ventricular mass in dogs. To assess the interstudy, intraobserver and interobserver variability of left ventricular myocardial mass measurements in humans, left ventricular myocardial volume was measured three times within 24 h in 16 patients with ischemic heart disease. The mean percent difference of the mean of the three studies performed was -0.01 +/- 1.4% (range -2.9% to 3.6%). The regression analysis for the intraobserver variability at baseline was: Y = -4.33 + 1.03X; r = 0.99, SEE = 3.5 ml. The mean percent difference of the mean of the two sets of measurements performed by two independent observers was 0.28 +/- 2.1% (range -4.35% to 4.35%). The interobserver variability excluding papillary muscles at baseline study was: Y = -4.34 + 1.06X; r = 0.99, SEE = 1.5 ml. The regression analysis with versus without papillary muscles showed: Y = -8.72 + 0.97X; r = 0.96, SEE = 2.6 ml. Regression analysis to assess the variability of 24-h studies at end-systole versus end-diastole revealed: Y = 3.07 + 0.94X; r = 0.97, SEE = 1.8 ml. In conclusion, ultrafast computed tomography is a minimally invasive technique, with very low interstudy, intraobserver and interobserver variability for left ventricular myocardial volume and mass determinations in serial studies.

Cardiomegaly↗
PubMed1991

Validation of ultrafast computed tomographic left ventricular volume measurement.

Left ventricular volume has been measured with ultrafast computed tomography. However, the accuracy with which this can be done is unknown. We therefore imaged with ultrafast computed tomography 11 rectangular phantoms, 20 to 225 ml, and 17 left ventricular casts, 15 to 112 ml. Two observers planimetered serial tomographic images and computed volume from sequential tomograms. There was no significant inter- or intraobserver difference in measurement of phantoms. Deviation of ultrafast computed tomographic volume from true phantom volume was -0.1 +/- 3.5% SD, range 9.0 to -7.6%. Correlation of true phantom volume with ultrafast computed tomographic volume was 0.99, SEE = 1.9 ml. No significant difference was observed between merged and single ultrafast computed tomographic scanning sequences. Left ventricular cast volume determined by ultrafast computed tomography deviated from true volume by 6% +/- 20%, range 54% to -45%. Correlation of true volume with ultrafast computed tomographic volume was 0.99, SEE = 5.1 ml. There was no interobserver significant difference in measurement of left ventricular cast volume. Correlation between ultrafast computed tomographic volume and cineradiographic volume of the same left ventricular casts was 0.99, SEE = 4.4 ml. Thus, phantom volumes can be measured accurately without significant intra- or interobserver variation. Merged scanning sequences did not influence volume determination. Left ventricular cast volume determination was comparable to that obtained with cineradiography.

Cardiac Volume↗