Search PubMed⌕ Search

Biomedical subjects

E B Clark

Publications and source records attributed to E B Clark.

90 records · Page 5Linked to original sources
PubMed1983

Effect of environmental hypothermia on dorsal aortic blood flow in the chick embryo, stages 18 to 24.

Dorsal aortic blood flow was measured with a pulsed-Doppler meter in Hamburger-Hamilton stage 18, 21, and 24 chick embryos, and stroke volume index was calculated by dividing mean blood flow per minute by heart rate. These parameters were measured at baseline temperature 34.7 degrees C after cooling to 31.1 degrees C and subsequent rewarming to 34.2 degrees C. In stage 21 embryos, after environmental cooling, heart rate decreased from 170 bpm to 118 bpm (P less than 0.01), mean dorsal aortic blood flow decreased from 0.38 mm3/sec to 0.24 mm3/sec (P less than 0.01) but stroke volume index did not change [baseline, 0.13 mm3/beat; after cooling, 0.12 mm3/beat; after rewarming, 0.15 mm3/beat (P = N.S.)]. Similar results were observed in stage 18 and 24 embryos. The bradycardic response to environmental hypothermia was independent of functional autonomic innervation and probably mediated by a direct suppression of cell action potential dv/dt. Myocardial cell function was not adversely affected by an acute change in environmental temperature as the index of stroke volume was not altered, and all parameters returned rapidly to baseline with rewarming.

Action Potentials↗
PubMed1982

Preoperative secundum atrial septal defect with coexisting sinus node and atrioventricular node dysfunction.

Sinus node dysfunction in patients after repair of the secundum atrial septal defect has been ascribed to surgical damage. We studied 15 consecutive patients with secundum atrial septal defect before operative intervention. Noninvasive testing included 34-hour electrocardiographic monitoring and a standard 13-lead ECG. Intracardiac electrophysiologic techniques included corrected sinus node recovery time, sinoatrial conduction time, His bundle recording to measure AH and HV intervals, the atrial pacing rate at which atrioventricular node Wenckebach occurred, and atrioventricular nodal refractory period. The ECG revealed an ectopic atrial rhythm in two patients. Intracardiac electrophysiology showed an abnormal corrected sinus node recovery time (range -40 to 800 msec) in 10 patients. Five patients had evidence of atrioventricular nodal dysfunction with prolonged AH interval or abnormal atrial pacing rate at which atrioventricular Wenckebach occurred. These data indicate that sinus node dysfunction or atrioventricular node dysfunction were present before surgical intervention.

Adolescent↗
PubMed1982

Foramen ovale/atrial septum area ratio: a marker of transatrial blood flow.

We examined 51 cardiac specimens to test the hypothesis that the size of the foramen ovale is directly proportional to the relative volume of transatrial blood flow during cardiac morphogenesis. Included in the study were 18 normal specimens, five with tricuspid atresia, four with pulmonary atresia and intact ventricular septum, nine with secundum atrial septal defect, eight with simple coarctation of the aorta and seven with aortic stenosis. The areas of the foramen ovale and atrial septum were measured and the ratio of foramen ovale to atrial septum was calculated. The area of the atrial septum did not differ significantly among the six groups. Normal specimens had a ratio of 0.19 +/- 0.07. Specimens with tricuspid atresia and pulmonary atresia had ratios of 0.43 +/- 0.01 and 0.38 +/- 0.10, respectively (p less than 0.05). The ratio in specimens with coarctation of the aorta was 0.15 +/- 0.07 (NS). Specimens with aortic stenosis had a ratio of 0.11 +/- 0.06 (p less than 0.05). Specimens with secundum atrial septal defects had a ratio of 0.37 +/- 0.08 (p less than 0.05). These data indicate that the foramen ovale is a marker of transatrial blood flow in utero. Secundum atrial septal defects may be a consequence of increased transatrial blood flow.

Child↗
PubMed1982

Developmental hemodynamic changes in the chick embryo from stage 18 to 27.

We report the hemodynamic parameters of stage 18, 21, 24, and 27 chick embryos (from 3 to 5 days of incubation). Dorsal aortic blood velocity and mean vitelline artery blood pressure are measured with a 20 MHz pulsed-Doppler meter and servo-null pressure system respectively. We also measure heart rate, dorsal aortic diameter and embryo weight of each developmental stage. From these data, we calculate mean dorsal aortic blood flow, mean dorsal aortic blood flow per cardiac cycle, mean dorsal aortic blood flow per milligram embryo weight, vascular resistance and cardiac work. Blood flow increases geometrically with each embryo stage but remains constant when normalized for embryo weight. Mean arterial pressure increases linearly and vascular resistance decreases geometrically. Cardiac work increases in proportion to embryo weight. These results define the parameters of normal hemodynamic function during early embryonic development.

Animals↗
PubMed1981

Changing indications for pacemakers in children.

Permanent pacemakers were implanted in 50 children. Indications were symptomatic sinus node dysfunction in 34 (68%), surgical block in 9 (18%), and congenital block in 7 (14%). Twenty-three (68%) of the 34 children with sinus node dysfunction had undergone prior cardiac operations. Only 4 of the 50 patients (8%) had electrode problems after a mean pacing time of 29.5 months (range, 1 to 96 months). All 35 of the mercury-cell pulse generators used in 28 patients ceased to function after an average useful life of 20.8 months (range, 1 to 51 months). The lithium-powered units in the 45 survivors all show satisfactory pacing after 5 to 44 months (mean, 28.1 months). With improved pacemaker technology, longer survival after complex repairs, and better monitoring techniques, the indications for cardiac pacing in children have broadened. Surgical block now is an indication in only a small fraction of the pediatric pacemaker population. Sinus node dysfunction accounts for an ever-increasing majority of the pacemakers we currently implant in children.

Adolescent↗
PubMed1979

Plastic casts of embryonic respiratory and cardiovascular system: a technique.

This report describes a technique for producing plastic casts of the cardiovascular and respiratory systems of the chick embryo at Stage 36 or older. For casts of the cardiovascular system, polymerization compound is injected in the right ventricle filling the heart, venous, and arterial system. A two stage injection produced more detailed casts of the pulmonary vasculature. For respiratory system casts, the compound is injected in the trachea filling the bronchi and air sacs. Casts are prepared by tissue corrosion in 10% potassium hydroxide. This technique is an alternative to serial section reconstruction in the study of developing cardiovascular and respiratory system.

Animals↗
PubMed1979

Critical aortic coarctation: patch aortoplasty in infants less than age 3 months.

Twenty-three infants less than age 3 months (mean age 31 days) underwent patch aortoplasty for relief of coarctation of the aorta. All had intractable congestive heart failure, despite aggressive medical therapy. Each infant had other cardiac anomalies, including patent ductus arteriosus (83 percent) and ventricular septal defect (74 percent). All patients underwent closure of the ductus arteriosus and patch angioplasty of the aorta to produce a luminal diameter of at least 16 mm. In addition, 9 of the 17 patients (53 percent) with a large shunt ventricular septal defect underwent pulmonary arterial banding. There was one hospital death 42 days after operation secondary to bowel perforation and sepsis. Hospitalization beyond 21 days postoperatively was always due to other unrepaired cardiac lesions. The three late deaths at 3, 9 and 18 months after operation were associated with additional major anomalies. Fourteen patients have had postoperative catheterization. No gradient was found across the site of coarctation repair, but one patient had a gradient between the left carotid and left subclavian arteries. Surgical repair of critical coarctation of the aorta in infants can safely be offered despite the presence of other cardiac anomalies.

Aging↗
PubMed1979

Late complications following surgical repair of total anomalous pulmonary venous return below the diaphragm.

Between May, 1975, and June, 1977, we surgically repaired an infracardiac total anomalous pulmonary venous return in 4 infants under deep hypothermic cardiac arrest. All patients had pulmonary hypertension and a patent ductus arteriosus. All survived operation and required positive end-expiratory pressure with mechanical ventilation. Late complications included patent ductus arteriosus not visualized at initial catheterization, breakdown of an oversewn atrial septal defect repair, and pulmonary venous obstruction despite an anastomosis diamter of 1.5 to 2.5 cm. At reoperation, there was scarring and contraction at the junction of the pulmonary veins and left atrium. One infant with these complications died post-operatively. In another patient, there was kinking of the left lower pulmonary vein at its juncture with the left atrium. In view of these complications we currently recommend the following: ligation of the ductus arteriosus regardless of catheterization findings; a right-sided approach to avoid pulmonary vein kinking; prosthetic patch closure of the atrial septal defect to avoid excessive tension on suture lines and to maintain maximum left atrial size; stellate anastomosis to provide the largest possible drainage channel; awareness that an unusually high positive end-expiratory pressure may be required postoperatively; and early recatheterization.

Cardiac Catheterization↗
PubMed1979

Increased mitral-aortic separation in discrete subaortic stenosis.

We recently speculated that mitral-aortic separation (MAS) might be increased in discrete subaortic stenosis (DSS). We have examined this hypothesis in 22 heart specimens in which the subaortic obstruction originated on the muscular ventricular septum below the right aortic sinus, either as a discrete band, an accumulation of several bands or a diffuse ridge, and extended posteriorly into the MAS or anterior leaflet of the mitral valve or both, with a variable relationship to the aortic cusps and sinuses. No specimen had ventricular septal defect, supravalvular aortic stenosis or other features of Shone syndrome. The mean MAS was nearly twice that of 80 normal specimens (4.9 vs 2.5 mm), the range of MAS was increased from normal (0.11 vs 0.7 mm) and the mean diameter of the aortic annulus was decreased compared with the normal specimens, data that will be of interest to echo- and angiocardiographers in the clinical description of DSS, and to the surgeon who must resect these lesions.

Adult↗
PubMed1977

Assessing the blalock-hanlon atrioseptectomy at cardiac catheterization.

Blalock-Hanlon atrial septectomy (BH) is performed to increase systemic and pulmonary venous mixing at the atrial level. Failure of clinical improvement may be related to inadequate intraatrial communication. A simple catheterization technique employing a balloon catheter is used to assess the presence or absence of the limbus of the foramen ovale following BH, since persistence of the limbus of the fossa ovalis after BH is associated with significantly smaller percentage of communication (atrial communication area/total atrial area).

Cardiac Catheterization↗
PubMed1977

Atrial defect size after Blalock-Hanlon atrioseptectomy.

In transposition of the great arteries, a Blalock-Hanlon closed atrial septectomy is performed to improve intracardiac mixing at the atrial level. Although the Blalock-Hanlon septectomy is a common surgical procedure in cyanotic congenital heart disease, it has not been adequately assessed pathologically. In 14 heart specimens from patients (aged 3 days to 19 years) with transposition of the great arteries and Blalock-Hanlon septectomy, the margins of the septectomy, fossa ovalis and atrial septum were identified. The total area of the septum and its defects was calculated using planimetry. The ratio of defect size to atrial septal area was expressed as percent communication, which ranged from 5 to 39 (mean 18) percent in eight specimens with intact limbus of the foramen ovale and 26 to 57 (mean 42) percent in six specimens in which the limbus had been excised. The finding that specimens in which the Blalock-Hanlon defect extended into the fossa ovalis had the largest total communication emphasizes that to obtain optimal bidirectional atrial mixing the surgeon should extend the Blalock-Hanlon procedure across the limbus into the foramen ovale.

Child↗
PubMed1976

The normal spectrum of mitral and aortic valve discontinuity.

The relationship of the base of the left and noncoronary sinuses of the aortic valve and the adjacent aortic leaflet of the mitral valve was studied in 106 normal heart specimens and 184 specimens with isolated VSD. The results show a spectrum of persistence of the tissue along the inner curvature of the heart. This may help settle the recent controversy in the interpretation of echocardiograms of this area because the recorded mitral-aortic discontinuity may be due to this spectrum rather than to variations in technique.

Adult↗
PubMedDate not supplied

Repair of coarctation of the aorta in children with Turner syndrome.

Increased risk of perioperative hemorrhage has been described in patients with Turner syndrome and coarctation of the aorta. We have operated on 11 patients with Turner syndrome and coarctation of the aorta, two of whom developed bleeding. One patient died. End-to-end anastomosis was performed in all patients. Histologic studies of resected specimens did not reveal any abnormalities. The risk of bleeding was not related to age at the time of repair or postoperative hypertension. Although no specific abnormality has been identified in these patients, the risk of serious hemorrhage appears increased.

Aortic Coarctation↗