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Biomedical subjects

W Zwehl

Publications and source records attributed to W Zwehl.

24 records · Page 2Linked to original sources
PubMed1981

Real time computerization of two-dimensional echocardiography.

A computerized system was developed for real time acquisition, enhanced processing, analysis, and display of cross-sectional images of the left ventricle derived by two-dimensional echocardiography (2DE). The new methodology couples a standard medical imaging computer system to the video output of any current 2DE unit, uses a 128 x 128 or 64 x 64 matrix window and stores the real time 30 frames/sec digitized images on a magnetic disk. Computerized beat-to-beat and frame-by-frame processing employs space-time smoothing the automatic detection of endocardial interfaces by standard threshold and second derivative techniques. Multiple views are displayed in real time with 256 levels of gray and color. The methodology was used to analyze and graphically display frame-by-frame changes throughout the cardiac cycle. In addition, regional wall motion and thickness were analyzed in 12 sectors of individual cross-sections using a standardized angular subdivision originating at the center of area and indexed by an external reference point. An algorithm was developed to correct cross-sectional interference definition from the commonly used trailing-to-leading edge to the more valid leading-to-leading outline technique. Computerized analysis of spatial and temporal variations of cardiac contraction were demonstrated in several clinical and experimental applications, including bicycle exercise testing, investigation of acute myocardial infarction, and assessment of interventions. Initial evaluation indicates that the new real time computerized digital acquisition and data analysis represents a major advances toward quantitation of left ventricular function using 2DE.

Animals↗
PubMed1981

Quantitative two dimensional echocardiography during bicycle exercise in normal subjects.

A quantitative two dimensional echocardiographic study was conducted in 10 normal subjects performing bicycle exercise in a supine position. Standardized two dimensional echocardiographic short axis and apical views of the left ventricle were analyzed to derive left ventricular sectional areas and length. Over a range of exercise heart rates from 108 to 152 beats/min, satisfactory two dimensional echocardiographic views and measurements were obtained for quantitative assessment of sectional and global left ventricular function. Variability of left ventricular short axis area measurements ranged from 2.9 to 8.3 percent. Left ventricular volume reconstruction employed a simplified formula (volume = 5/6 area X length) with a single papillary muscle level short axis area and left ventricular length. Changes in left ventricular function from rest to exercise quantitated by two dimensional echocardiography indicated a significant reduction in end-systolic volume (from 28.1 +/- 5.6 to 20.8 +/- 4.3 cc/m2, p less than 0.001) and increased left ventricular ejection fraction (from 63.4 +/- 6.3 to 72.1 +/- 5.7 percent, p less than 0.001). The change in end-diastolic volume was not significant. It is concluded that standardized two dimensional echocardiographic study during supine bicycle exercise in normal subjects provides good reproducibility of measurement of sectional and global left ventricular function. Quantitative two dimensional echocardiographic exercise study of global as well as segmental left ventricular performance in patients may be feasible using standardized procedure and analysis.

Adolescent↗
PubMed1981

[Left ventricular volumes by cross-sectional echocardiography in the dog: a comparison with biplane angiocardiography (author's transl)].

Using apical long axis and precordial short axis views, left ventricular end-diastolic and end-systolic volumes and ejection fraction were determined by cross-sectional echocardiography and compared with biplane angiocardiography. 10 anesthetized, closed chest dogs were first studied in the control state. Inferior vena cava was occluded by a balloon-inflated catheter, measurements were repeated. Descending aorta was blocked, with measurements retaken. Finally 8 dogs were studied after left coronary artery occlusion. For enddiastolic volumes correlation coefficients were 0.89, 0.93, 0.89, and 0.90 respectively (n = 10, 10, 10, 8; p less than 0.01). End-systolic volumes correlated with r 0.94, 0.92, 0.83, 0.92 (p less than 0.01). Left ventricular volumes were systematically underestimated by echocardiography (p less than 0.05). Ejection fraction corresponded less favourably, overall r was 0.85 (n = 38; p less than 0.01). Thus, cross-sectional echocardiography appears suitable for quantifying left ventricular volumes, less ejection fraction in the dog, during acute interventions as well as in the presence of regional dysfunction.

Angiocardiography↗
PubMed1980

[Reno-cardiac interactions in kidney failure (author's transl)].

The high incidence of cardiac complications in endstage renal failure is not only related to the chronic pressure load of the left ventricle, although the proportion of patients with elevated blood pressure increases from 53 to 81% as reno-parenchymal disease progresses. Other factors as anemia, hyperparathyroidism, autonomic neuropathy and retention of electrolytes, metabolic products of toxins may cause damage to the heart. It is a matter of discussion whether uremia itself causes cardiomyopathy. Findings of a reduced Ca++-uptake during beta-adrenergic stimulation and a reduced reaction of (Na+, K+)-ATPase to digitalis suggest a basic change of myocardial membrane metabolism. Retention of an "endogenous digitalis" could help to explain some contradictory results.

Adolescent↗
PubMed1979

[Echocardiographic dimensions of the left ventricle during ergometric exercise: results in normal subjects (author's transl)].

10 healthy men aged 18 to 32 years underwent M-mode-echocardiographic studies at rest, during exercise and recovery. Semisupine bicycle exercise was performed using work loads of 25, 50, 75, and 100 W with measurements taken every minute. With increasing exercise, heart rate rose significantly (p less than 0.01) from 68/min to a maximum of 132/min, blood pressure as obtained by sphygmomanometry rose from a mean of 83 torr to 102 torr. Left ventricular enddiastolic dimension (EDD) did not change significantly with exercise, left ventricular endsystolic dimension (ESD) decreased from a group mean of 34.8 mm to 30.5 mm. This paralleled an increase in stroke dimension from 18.3 to 22.6 mm and of fractional shortening (FS) from 0.34 to 0.43. Mean velocity of circumferential fiber shortening (MVCF) rose from 1.01 circ/s to 2.06 circ/s. During recovery, heart rate and blood pressure returned faster to resting levels than did ESD, FS, and MVCF. Again EDD did not change. These data indicate that heart rate contributes more to the increases in cardiac output observed with ergometric exercise than does stroke volume; with moderate exercise levels this increase in stroke volume is produced by diminishing endsystolic volume whilst enddiastolic volume remains unchanged.

Adolescent↗