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Biomedical subjects

J A Rumberger

Publications and source records attributed to J A Rumberger.

At least 73 records · Page 4Linked to original sources
PubMed1992

Quantitative dynamics of left ventricular emptying and filling as a function of heart size and stroke volume in pure aortic regurgitation and in normal subjects.

Quantitative understanding of the dynamics of left ventricular (LV) emptying and filling as the left ventricle dilates but maintains ejection fraction is limited. Cine computed tomography was used to quantify peak LV emptying and filling characteristics in 30 patients with normal ejection fraction but variable end-diastolic and stroke volumes. Group I consisted of 15 normal male patients and group II of 15 male patients with chronic, well-compensated, isolated aortic regurgitation. For each patient global LV volumes, absolute peak emptying and peak early diastolic filling rates and the timing of these maximal slopes were quantified. Mean arterial pressure and heart rate were within the normal range and ejection fraction and ages similar between groups I and II. Between-group analyses showed significantly increased end-diastolic and stroke volumes in group II compared with group I but nearly identical end-systolic volumes. Likewise, absolute peak emptying and filling rates were significantly greater in group II than in group I patients. The ratio of peak emptying rate to peak filling rate remained constant between groups. Timing of peak emptying and filling were similar in both groups. Absolute LV peak emptying and filling rates were found to vary linearly with end-diastolic and stroke volumes in all subjects examined. However, referencing peak emptying or peak filling rates to end-diastolic or total stroke volumes eliminated intergroup differences. Thus, in the presence of preserved ejection fraction and normal arterial pressure, the dynamic rates of LV emptying and early diastolic filling increase in direct proportion to absolute end-diastolic and stroke volumes, but the ratio of peak emptying to peak filling rate remains constant.

Adult↗
PubMed1992

Semiquantitation of aortic regurgitation by different Doppler echocardiographic techniques and comparison with ultrafast computed tomography.

Fourteen patients with chronic aortic regurgitation were studied by several two-dimensional and Doppler echocardiographic methods to determine the severity of aortic regurgitation. Semiquantitation of aortic regurgitation was performed by various color-flow imaging measurements, diastolic half-time of the continuous-wave regurgitation jet, and pulsed-wave velocity curve in the descending aorta. These measurements were compared with regurgitant volume and fraction by ultrafast computed tomography. All Doppler methods demonstrated a significant correlation for severity of aortic regurgitation with regurgitant fraction by ultrafast computed tomographic scanning, but scatter was present with each method. The methods with the closest correlation were at the lowest level of obtainable results. In clinical practice, all Doppler methods must be used to determine the severity of aortic regurgitation.

Adult↗
PubMed1992

Measurement of myocardial perfusion and cardiac output using intravenous injection methods by ultrafast (cine) computed tomography.

Ultrafast (or cine) computed tomography (CT) uses a novel scanning electron beam technology to obtain multi-level images of the beating heart in rapid succession. Recent investigations have demonstrated that it can be used to define the transit of iodinated contrast media through the cardiac chambers and myocardium. Using classical indicator dilution principles and rapid intravenous injection of iodinated contrast media, ultrafast CT can quantify cardiac output and, to a limited extent, myocardial perfusion. A caveat to the application requires that careful calibration be made on a subject-by-subject basis prior to quantification of cardiac output. Although global myocardial perfusion and flow reserve can be evaluated by ultrafast CT, spatially variable imaging artifacts may limit the application in all regions of the left ventricular myocardium. Advances in study design, image reconstruction and post-image processing continue. Ultrafast CT technology offers a means to define cardiac anatomy, function and flow in man rapidly, conveniently and accurately in a noninvasive fashion employing intravenous contrast media injection.

Cardiac Output↗
PubMed1992

Coronary artery calcification detected with ultrafast CT as an indication of coronary artery disease.

To assess the relationship of coronary artery calcification to angiographically detectable disease, the authors evaluated 100 patients less than 60 years of age who underwent clinically indicated coronary angiography and ultrafast computed tomography (CT). The ultrafast CT technique consisted of 3-mm-thick contiguous sections and a 100-msec acquisition time. All patients with clinically significant disease at angiography (defined as at least one stenosis with a diameter narrowing of at least 50%) had some coronary artery calcification present at ultrafast CT (100% sensitivity in this population). The absence of calcification at ultrafast CT had a 100% negative predictive value for clinically significant coronary artery disease. Specificity and positive predictive value were 47% and 62%, respectively. Sensitivity and specificity of ultrafast CT in the detection of patients with angiographically detectable disease were 94% and 72%, respectively. Ultrafast CT of the heart is an anatomically based, noninvasive test with high sensitivity for the detection of coronary artery calcification. Ultrafast CT may be beneficial in the screening of selected populations for the presence of atherosclerotic coronary disease.

Adult↗
PubMed1992

Ultrafast computed tomography analysis of regional radius-to-wall thickness ratios in normal and volume-overloaded human left ventricle.

BACKGROUND: This study tested two hypotheses: 1) regional left ventricular radius-to-wall thickness ratios (R/T) are uniform in normal subjects, and 2) patients with left ventricular hypertrophy secondary to compensated volume overload normalize global and regional R/T. METHODS AND RESULTS: Ultrafast computed tomography was used to measure regional short-axis ventricular R/T in 11 normal subjects and 13 patients with compensated aortic insufficiency (AI) of moderate severity (regurgitant fraction, greater than or equal to 25%). Radius and wall thickness dimensions were calculated by two different methods. In method 1, the average radius and wall thickness were determined for each planimetric transaxial tomographic image. In method 2, the left ventricle was three-dimensionally reconstructed; then, new radii and wall thickness were recalculated as if all the images were acquired orthogonal to the endocardial surface at each tomographic level. In normals, the mean R/T ratio was 1.75 +/- 0.11 (SEM) with method 1 and 1.80 +/- 0.07 with method 2. The R/T ratios varied as a function of the relative apex-to-base position. R/T ratios at the basal four levels were relatively uniform, whereas R/T at the lower three tomographic levels were significantly less than those at the base (p less than 0.01). Patients with AI had a mean regurgitant fraction of 44 +/- 3.8% (range, 25-63%). The mean R/T ratio was 2.18 +/- 0.16 with method 1 and 2.55 +/- 0.18 with method 2. Similar to the pattern observed in normals, the regional R/T ratios at the lower three or four levels were significantly less than the basal R/T ratios (p less than 0.01). Regional comparison of the normal to the volume-overloaded ventricles demonstrated that R/T ratios in the AI patients were significantly greater at the upper five levels with method 1 and at all eight levels with method 2 (p less than 0.01-0.001, AI versus normal). CONCLUSIONS: These findings demonstrate that regional R/T ratios are heterogeneous in both normals and patients with left ventricular hypertrophy secondary to compensated aortic insufficiency. Furthermore, these findings challenge the accepted hypothesis that global and regional R/T ratios normalize in patients with compensated volume-overload hypertrophy.

Adult↗
PubMed1991

Ultrafast computed tomography.

Ultrafast computed tomography is a developing cardiac imaging modality that can provide high temporal and spatial resolution images of the beating heart in the outpatient setting. The three-dimensional registration of these images has facilitated numerous studies showing this device to be capable of quantitating cardiac anatomy, cardiac function, and cardiac blood flow. During the past 1 to 2 years, these applications have extended into definition of right ventricular muscle mass, cardiac sources for embolization, and the possibility of diagnosing asymptomatic coronary artery disease through visualization of discrete coronary artery calcification. With respect to cardiac functional analysis, studies now suggest the application of exercise ergometry and ultrafast computed tomography imaging to define the physiologic significance of coronary stenoses. Studies involving the adaptation of indicator dilution methods to ultrafast computed tomography to quantitate regional myocardial perfusion continue to suggest this as a potential tool in the noninvasive quantitation of regional myocardial perfusion. The major limitation of this method is its availability, at present, in only a select number of major medical centers throughout the world.

Coronary Circulation↗
PubMed1991

The effect of a low-osmolar radiographic contrast medium on in vivo and postmortem renal size.

High osmolar radiographic contrast media (CM) are known to cause an increase in renal size. To examine the effect of low-osmolar CM on renal size, 14 anesthetized dogs received 12 intravenous bolus injections of 0.5 mL/kg iohexol (541 mOsm/L). The postmortem renal, cortical, and medullary volumes were determined by fluid displacement. Renal volumes of 18 control dogs were determined similarly. The mean (+/- SEM) postmortem renal volumes were 66.1 +/- 2.2 mL for the CM group and 52.3 +/- 3.3 mL for the control group (P = 0.003), whereas the cortical and medullary volumes were similar. Six dogs were also scanned by fast computerized tomography before and after iohexol administration. The in vivo whole renal and medullary volumes enlarged from 67.4 +/- 3.0 to 77.1 +/- 2.8 mL (P = 0.006), and from 28.5 +/- 2.0 to 35.1 +/- 1.1 mL (P = 0.026), respectively, while the cortical volume remained unaltered. These results suggest that even low osmolar CM may significantly increase renal volume, probably by causing tubular expansion.

Animals↗
PubMed1990

Quantitation of the in vivo kidney volume with cine computed tomography.

The authors examined the utility of cine computerized tomography (CT) for noninvasive determination of whole kidney, cortical, and medullary volumes. The right kidneys of 14 anesthetized dogs were scanned after an intravenous bolus injection of iohexol, and their volumes determined after boundary identification. After the scans, the kidneys were excised at postmortem examination and their volumes determined by fluid displacement. The mean (+/- standard error of the mean [SEM]) postmortem and in vivo renal volumes were 66.1 +/- 2.2 cc and 78.2 +/- 2.4 cc, respectively (r = 0.86; P less than 0.001). The difference was consistent with the blood, filtrate, and urine contents of the in vivo kidney. The in vivo cortical and medullary volumes correlated poorly with their postmortem volumes because of difficulties in boundary definition. These results demonstrate the feasibility for fast and reliable in vivo whole kidney volume quantitation by cine CT.

Animals↗
PubMed1989

Patterns of regional diastolic function in the normal human left ventricle: an ultrafast computed tomographic study.

The detailed evaluation of regional diastolic filling at multiple ventricular levels in the normal human left ventricle has not previously been reported. Ultrafast computed tomography was used to characterize global and regional early diastolic filling in the left ventricle of 11 normal male volunteers. Regional early diastolic filling data from six distinct ventricular levels (apex to base) were fit to a third-order polynomial curve, and the peak rate of diastolic filling and time of peak filling were determined. Peak filling rate was 259 +/- 17 ml/s (+/- SEM) as a global average, where peak filling rate referenced to end-diastolic volume and stroke volume across the levels examined was 3.78 +/- 0.17 s-1 and 4.83 +/- 0.20 s-1, respectively. Average filling fraction was 39 +/- 1%, and time to peak filling from end-systole was 145 +/- 5 ms. Regional (tomographic) peak filling rates, except for the most apical level examined, were not statistically different across the ventricle. Filling fraction and time to peak filling were remarkably constant from one level to another. However, reference of regional peak filling rate to regional end-diastolic volume demonstrated significant nonuniformity from apex (120% of average for all levels) to base (87% of average for all levels). Peak filling rate referenced to tomographic stroke volume was less variable and not statistically different across the ventricle as a whole.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Ultrafast cardiac CT scanning.

Computerized tomography (CT) represents the optimal theoretic approach to x-ray imaging. Ultrafast CT is an emerging imaging modality that has been shown to be highly applicable to quantitative determinations of ventricular mass, right and left ventricular volumes, and global and regional left ventricular function in a variety of cardiac pathologic states. This article examines the clinical capability of ultrafast CT and attempts to answer some concerning questions that may be raised.

Animals↗