Biomedical subjects

T A Risser

Publications and source records attributed to T A Risser.

4 recordsLinked to original sources

PubMed1986

Mechanisms of pulsus paradoxus during resistive respiratory loading and asthma.

To determine the mechanisms of pulsus paradoxus during asthma, six subjects known to have cold air bronchial hyperreactivity were studied while in a quiescent phase of their disease. All were free of significant airway obstruction at the time of study. After placement of an esophageal balloon to estimate intrathoracic pressure, the subjects were assessed during quiet breathing, resistive airway loading and then during a stable period of airway obstruction induced by cold air. Steady state left ventricular volume and performance were measured using radionuclide ventriculography; right ventricular volume was calculated from the stroke volume ratio and right ventricular ejection fraction. Cardiac cycles were segregated according to their occurrence in inspiration or expiration using a flow signal from a pneumotachograph. Combined inspiratory and expiratory resistance produced pulsus paradoxus and changes in esophageal pressure that were similar to those during asthma and significantly greater than those during quiet breathing. These changes were accompanied by decreases in left ventricular diastolic volume and stroke volume during inspiration, and increases in these variables during expiration; right ventricular volume and stroke volume demonstrated changes reciprocal to those seen in the left ventricle. These data indicate that during periods of increase in airway resistance, abnormal pulsus paradoxus results from an exaggeration in the normal inspiratory-expiratory difference in stroke volume mediated primarily by the effects of intrathoracic pressure on ventricular preload.

Adult↗

PubMed1984

Quantitative analysis of left ventricular function: pre- and postischemic two-dimensional echocardiography in dogs.

A quantitative technique that aligns the diastolic and systolic silhouettes was used to assess left ventricular function (wall thickening and endocardial wall motion) from two-dimensional echocardiographic studies for every 2 degrees of arc of the left ventricular circumference in canines. Thirty-two dogs were studied before and at specific intervals up to 14 days after either temporary or permanent occlusion of the left anterior descending coronary artery. Decreased systolic wall thickening and frank systolic thinning were observed in the ischemic/infarcted region 90 min and 6 hr after occlusion; endocardial motion showed the abnormally contracting segment less clearly. Partial recovery was seen in both groups of animals but to a greater degree in those with temporary occlusion. The technique was useful for assessing sequential changes in wall motion.

Animals↗

PubMed1983

Quantitative computer-assisted analysis of left ventricular wall thickening and motion by 2-dimensional echocardiography in acute myocardial infarction.

Quantitative regional wall motion analyses of 2-dimensional echocardiograms (2-D echo) have usually focused on large arcs (greater than 45 degrees) of the left ventricular (LV) perimeter rather than on small LV zones. Few studies have assessed changes in wall thickness. To determine normal ranges of regional LV function, the endocardial and epicardial contours of short-axis 2-D echoes obtained at the papillary muscle level of 10 normal subjects were manually traced. Then, 15 patients with acute myocardial infarction (MI) were studied, comparing their contours at admission with ranges determined from the normal subjects. In all patients with MI, 2-D echoes located abnormal wall motion involving at least the region identified as abnormal by the electrocardiogram and often extending into adjacent regions. All 9 patients with transmural MI had either decreased wall thickening or abnormal endocardial wall motion; all except 1 had focal thinning in the region of the MI. Of the 6 patients with nontransmural MI, 2 had abnormal endocardial wall motion, and all had decreased wall thickening. Evaluating regional wall motion at multiple points around the LV circumference should permit more precise delineation of LV function in health and disease than has been heretofore possible.

Adult↗

PubMed1983

Quantitative analysis of left ventricular wall motion and thickness using two-dimensional echocardiography.

The real time two-dimensional ultrasonic imaging of the left ventricle made possible segmental echocardiographic measurements of wall motion and thickening and thinning. The underlying hypothesis is that measurements of regional wall motion could quantify the extent of myocardial ischemia and infarction; the method could be used as a truly non-invasive tool to assess the severity of damage from infarction and the effects of interventions designed to limit infarcts. The method is operator interactive. Each patient's data could be compared with data for a normal group. The selection criteria for the normal patients have been described. The confidence region of the normal group and the effect of averaging over three tracings for three heartbeats have been computed. Technical difficulties inherent in the method and possible improvements are discussed.

Computers↗