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Biomedical subjects

J L Weiss

Publications and source records attributed to J L Weiss.

At least 127 records · Page 7Linked to original sources
PubMed1979

Accurate volume determination in the isolated ejecting canine left ventricle by two-dimensional echocardiography.

Two-dimensional echocardiography can provide serial cross-sectional images of the left ventricular cavity. We examined whether such serial images from steady-state ejecting hearts would allow three-dimensional reconstruction and accurate volume estimation without major geometric assumptions. Cross-circulated, paced dog hearts were suspended in a blood-filled tank. Serial cross-sectional images were taken at 3-mm intervals along the vertical axis. Left ventricular cavity and muscle areas of each image were planimetered with a light-pen system and summated for volume: total volume = sigma (areas x 3 mm). Direct left ventricular volume was measured through the cardiac cycle with a volumetric chamber connected to a balloon in the ejecting left ventricle. In six hearts, 67 separate direct volume measurements (range 9.5--54.7 ml) from various points in the cardiac cycle were compared with the simultaneous echo volume measurements. By least squares linear regression, echo volume = 1.01 (direct volume) - 0.44 ml; r = 0.972, SEE = 2.93 ml. Provided accurate cross-sectional localization is available, these studies suggest that extremely accurate steady-state left ventricular volume can be determined noninvasively in the ejecting heart from multiple cross-sectional images.

Animals↗
PubMed1978

Evidence of incomplete left ventricular relaxation in the dog: prediction from the time constant for isovolumic pressure fall.

Although it has been proposed that incomplete relaxation explains certain increases in left ventricular end diastolic pressure relative to volume, there has been no clear demonstration that incomplete relaxation occurs in the intact working ventricle. To identify incomplete relaxation, left ventricular pressure-dimension relationships were studied in 10 canine right heart bypass preparations during ventricular pacing. The fully relaxed, exponential diastolic pressure-dimension line for each ventricle was first determined from pressure and dimension values at the end of prolonged diastoles after interruption of pacing. For 167 beats during pacing under widely varying hemodynamic conditions, diastolic pressure-dimension values encountered this line defining the fully relaxed state during the filling period indicating that relaxation was complete before end diastole. The time constant for isovolumic exponential pressure fall (T) was determined for all beats. For this exponential function, if no diastolic filling occurred, 97% of pressure fall would be complete by 3.5 T after maximal negative dP/dt. For the 167 beats the fully relaxed pressure-dimension line was always encountered before 3.5 T. With very rapid pacing rates (170-200 beats/min) and(or) with pharmacologic prolongation of relaxation, incomplete relaxation occurred as evidenced by the fact that the line defining the fully relaxed state was never reached during diastole (n = 15). This evidence of incomplete relaxation occurred only when the subsequent beat began before 3.5 T but did not always occur under these conditions. Thus, an increase in end diastolic pressure relative to diastolic volume may result from incomplete relaxation under conditions of sufficiently rapid heart rate or sufficiently prolonged ventricular relaxation. Incomplete relaxation does not occur when the next beat begins more than 3.5 T after maximum negative dP/dt.

Animals↗
PubMed1978

Two-dimensional echocardiographic diagnosis of left atrial myxoma.

Two patients with left atrial myxomas detected with one-dimensional echocardiographic studies were evaluated before and after surgery with real-time phased-array two-dimensional echocardiographic studies. This latter technique provided relatively quantitative information regarding the size, shape, and mobility of the tumor and its effect on cardiac function. In case 1, the two-dimensional echocardiogram showed a relatively immobile tumor measuring 3 x 4.5 cm in diameter in the left atrium only. At surgery a 2 x 4.5-cm myxoma that was attached to the left atrium by a broad-based short stalk was removed. In case 2, the left atrial mass appeared to be 3 x 4 cm in diameter, with much movement during the cardiac cycle. At surgery a 3 x 4-cm left atrial myxoma that was attached to the interatrial septum by a long stalk was removed. In both cases, masses in other cardiac chambers were excluded, the mitral valves were normal, and left ventricular function was normal, all of which were confirmed at surgery and by postoperative echocardiograms. In one patient the information obtained by two-dimensional echocardiographic studies was believed to be sufficient to preempt the need for cardiac catheterization. These cases illutstrate that this new noninvasive technique may provide sufficient quantitative preoperative detail in patients with left atrial tumors to obivate the risk and expense of caridac catheterization.

Echocardiography↗
PubMed1976

Child care attitudes and adaptation to the maternal role among mentally ill and well mothers.

Discharged psychiatric hospital patients who were mothers of young children were compared with a group of well mothers on child rearing attitudes and adaptation to adult social roles. Mentally ill mothers were found to believe less in the importance of developing a reciprocal mother-child relationship or in differentiating between own needs and those of child, and were more likely to deny ambivalent feelings regarding child care. In each group, less adaptive child-care attitudes were related to greater impairment in adapting to other adult roles.

Adaptation, Psychological↗
PubMed1976

Hemodynamic determinants of the time-course of fall in canine left ventricular pressure.

The hemodynamic determinants of the time-course of fall in isovolumic left ventricular pressure were assessed in isolated canine left ventricular preparations. Pressure fall was studied in isovolumic beats or during prolonged isovolumic diastole after ejection. Pressure fall was studied in isovolumic relaxation for isovolumic and ejecting beats (r less than or equal to 0.98) and was therefore characterized by a time constant, T. Higher heart rates shortened T slightly from 52.6 +/- 4.5 ms at 110/min to 48.2 +/- 6.0 ms at 160/min (P less than 0.01, n = 8). Higher ventricular volumes under isovolumic conditions resulted in higher peak left ventricular pressure but no significant change in T. T did shorten from 67.1 +/- 5.0 ms in isovolumic beats to 45.8 +/- 2.9 ms in the ejecting beats (P less than 0.001, n = 14). In the ejecting beats, peak systolic pressure was lower, and end-systolic volume smaller. To differentiate the effects of systolic shortening during ejection from those of lower systolic pressure and smaller end-systolic volume, beats with large end-diastolic volumes were compared to beats with smaller end-diastolic volumes. The beats with smaller end-diastolic volumes exhibited less shortening but similar end-systolic volumes and peak systolic pressure. T again shortened to a greater extent in the beats with greater systolic shortening. Calcium chloride and acetylstrophanthidin resulted in no significant change in T, but norepinephrine, which accelerates active relaxation, resulted in a significant shortening of T (65.6 +/- 13.4 vs. 46.3 +/- 7.0 ms, P less than 0.02). During recovery from ischemia, T increased significantly from 59.3 +/- 9.6 to 76.8 +/- 13.1 ms when compared with the preischemic control beat (P less than 0.05). Thus, the present studies show that the time-course of isovolumic pressure fall subsequent to maximum negative dP/dt is exponential, independent of systolic stress and end-systolic fiber length, and minimally dependent on heart rate. T may be an index of the activity of the active cardiac relaxing system and appears dependent on systolic fiber shortening.

Animals↗
PubMed1975

Identification of women at risk for unwanted pregnancy.

Concern about increasing rates of unwanted pregnancy, particularly among adolescents, has led to consideration of steps necessary to develop effective intervention programs. In order to reach a young woman for counseling and contraceptive assistance before she places herself at risk for unintended pregnancy, it seems necessary to develop the capability for identifying high-risk individuals without reference to sexual history. The authors describe a preliminary attempt to predict contraceptively unprotected coitus from responses to projective test stimuli, noting that the problem is so urgent that even early and necessarily incomplete work in this area may have merit in stimulating further research in identification of women at risk for unwanted pregnancy.

Adolescent↗