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Biomedical subjects

J T Bricker

Publications and source records attributed to J T Bricker.

At least 73 records · Page 4Linked to original sources
PubMed1989

The effects of hypoxemia on myocardial blood flow during exercise.

We evaluated the adequacy of regional and transmural blood flow during exercise and rapid pacing after 1 wk of hypoxemia. Seven mature mongrel dogs were made hypoxemic (mean O2 saturation = 72.4%) by anastomosis of left pulmonary artery to left atrial appendage. Catheters were placed in the left atrium, right atrium, pulmonary artery, and aorta. Atrial and ventricular pacing wires were placed. An aortic flow probe was placed to measure cardiac output. Ten nonshunted dogs, similarly instrumented, served as controls. Recovery time was approximately 1 wk. Cardiac output, mean aortic pressure, and oxygen saturation were measured at rest, with ventricular pacing, atrial pacing, and with treadmill exercise. Ventricular and atrial pace and exercise were at a heart rate of 200. Right ventricular free wall, left ventricular free wall, and septal blood flow were measured with radionuclide-labeled microspheres. Cardiac output, left atrial blood pressure, and aortic blood pressure were similar between the two groups of dogs in all testing states. Myocardial blood flow was significantly higher in the right and left ventricular free wall in the hypoxemic animals during resting and exercise testing states. Myocardial oxygen delivery was similar between the two groups of animals. Pacing resulted in an increase in myocardial blood flow in the control animals but not the hypoxemic animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Use of a left ventricular assist device as a bridge to transplantation in a pediatric patient.

Despite many advances in heart transplantation and in mechanical circulatory support, the benefits of staged cardiac transplantation have not been extended to the pediatric transplant recipient, chiefly because implantable circulatory assist devices are still too large. Extracorporeal devices, however, can overcome this impediment. Here we report the 1st case, to our knowledge, in which an extracorporeal left ventricular assist device has been used in a child to support circulation prior to cardiac transplantation. The patient was a 9-year-old boy in New York Heart Association functional class IV, with congestive heart failure as a result of idiopathic biventricular cardiomegaly. In mid-May of 1987, while awaiting a suitable donor, he suffered severe oliguria after an episode of circulatory arrest. Therefore we decided to maintain his circulation-and consequently his peripheral organ function-with an extracorporeal left ventricular assist device. After establishing cardiopulmonary bypass under normothermia and without cardiac arrest, we established flow from the left ventricle through a 36-Fr wire-reinforced straight cannula to a Biomedicus BP-80 centrifugal force pump, with return to the proximal ascending aorta through a 28-Fr wire-reinforced straight cannula. The patient's hemodynamic course under subsequent mechanical circulatory support was remarkably stable, with controllable systemic hypertension and no evidence of hemolysis. Although cardiac activity was minimal and systemic blood flow nonpulsatile, the patient's renal, pulmonary, and hepatic functions improved, and his peripheral circulation was well preserved. After 12 hours of support, a donor heart became available, and a routine orthotopic cardiac transplant was performed. Upon removal, the left ventricular assist device showed a small amount of thrombus formation. The patient's postoperative recovery has been easily manageable, and 20 months after transplant he enjoys unrestricted physical activity. We conclude that an extracorporeal left ventricular assist device can be used as a bridge to cardiac transplantation in children. Moreover, this application of a continuous force centrifugal pump without adverse effect encourages the conclusion that long-term maintenance of terminal heart disease patients might be possible through development of small, implantable pumps with the potential of lower power requirements and reduced thrombogenesis.

Journal Article↗
PubMed1988

Decrease in canine endocardial and epicardial electrogram voltages with exercise: implications for pacemaker sensing.

Individuals with permanently implanted pacemakers who have normal sensing and pacing at rest may demonstrate abnormalities, particularly of atrial sensing, with exercise. Exercise is known to cause changes in the surface electrocardiographic voltages. The purpose of this study was to evaluate changes in endocardial and epicardial voltages during exercise in canines with permanently implanted pacing leads similar to those permanently implanted in humans with pacemakers. Six adult mongrel dogs were equipped with transvenous atrial and ventricular endocardial bipolar screw-in leads from a jugular venosection, and with atrial and ventricular bipolar stab-on leads from a left thoracotomy. Exercise was performed at one week following implantation and at weekly intervals for a total of 4 weeks. The animals were studied at rest and at a single workload of 3 miles per hour at a 30% elevation. Unfiltered electrograms were recorded with a VR-12 Electronics-for-Medicine photographic recorder. The mean decreases of electrograms with exercise from resting voltage were: 15% for atrial endocardial unipolar leads; 11% for atrial endocardial bipolar leads; 4% for atrial epicardial unipolar leads; 15% for atrial epicardial bipolar leads; 8% for ventricular endocardial unipolar leads; 18% for ventricular endocardial bipolar leads; 0.1% for ventricular epicardial unipolar leads and 5% for ventricular epicardial bipolar leads.

Animals↗
PubMed1987

Emergency gastrotomy: treatment of choice for iron bezoar.

The authors believe that gastrotomy and surgical removal of tablets is the treatment of choice in massive iron ingestion with development of an "iron bezoar" unresponsive to gastric lavage. Prompt surgical treatment in such cases may be lifesaving.

Acute Disease↗
PubMed1987

Severe cardiopathy in branching enzyme deficiency.

A 7 1/2-year-old girl had exercise intolerance and exertional dyspnea. Four months later, congestive heart failure developed, with recurrent chylous pleural effusions, and she died at age 8 1/2 years. Endomyocardial biopsy tissue showed abundant PAS-positive, diastase-resistant cytoplasmic deposits. Similar inclusions were seen in muscle, skin, and liver specimens. Postmortem studies showed that the abnormal polysaccharide was especially abundant in heart and muscle, but was also present in all other tissues, including the central nervous system. Glycogen isolated from heart, muscle, and spinal cord showed a shift of the iodine spectrum toward higher than normal wavelengths. Branching enzyme activity was lacking in the muscle biopsy specimen and in all postmortem tissues; glycogenolytic enzymes had normal activities. These studies show that cardiomyopathy can be the first symptom of generalized branching enzyme deficiency and that the degree of accumulation of the abnormal polysaccharide may vary in different tissues.

Biopsy↗
PubMed1987

Double balloon technique for dilation of valvular or vessel stenosis in congenital and acquired heart disease.

Despite the generally excellent success with balloon dilation for the stenotic lesions of congenital and acquired heart disease, technical difficulties sometimes prevent satisfactory results. Such technical difficulties include: a large diameter of the anulus of the stenotic lesion relative to available balloon diameter, difficulty in the insertion or removal of the larger balloon catheters, and permanent damage to or obstruction of the femoral vessels by the redundant deflated balloon material of the large balloons. A double balloon technique was initiated to resolve these difficulties. With this method, percutaneous balloon angioplasty catheters were inserted in right and left femoral vessels, placed side by side across the stenotic lesion and inflated simultaneously. Dilation procedures using the two balloon technique were performed in 41 patients: 18 with pulmonary valve stenosis, 14 with aortic valve stenosis, 5 with mitral valve stenosis, 3 with vena caval obstruction following the Mustard or Senning procedure and 1 with tricuspid valve stenosis. Patient ages ranged from 1 to 75 years (mean 17.8) and patient weights ranged from 8.9 to 89 kg (mean 42.3). Balloon catheter sizes ranged from 10 to 20 mm in diameter. Average maximal pressure gradient in mm Hg before dilation was 61 in pulmonary stenosis, 68 in aortic stenosis, 21 in mitral stenosis, 12 in tricuspid stenosis and 25 in vena caval stenosis. Average maximal valvular pressure gradient after dilation was 13 in pulmonary stenosis, 24 in aortic stenosis, 4 in mitral stenosis, 0 in tricuspid stenosis, and 1 in vena caval stenosis. No major complications were encountered with the procedures.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Cardiac transplantation in an 8-month-old female infant with subendocardial fibroelastosis.

On Nov 1, 1984, an orthotopic cardiac transplantation was performed in an 8-month-old female infant with subendocardial fibroelastosis. Because of the advanced state of cardiac failure, the operation was done despite a positive tissue crossmatch for antitoxic donor-specific antibodies. Immunosuppression consisted of high doses of cyclosporine (up to 550 mg/m2 or 30 mg/kg) and steroids. Hypertension and tremor of the extremities, which were attributed to cyclosporine, occurred during the first week but resolved after seven days. No signs of nephrotoxic effects have been noted; however, a severe episode of allograft rejection was detected by endomyocardial biopsy on the seventh postoperative day, and a moderate rejection episode was noted on the 22nd postoperative day. Histologic improvement was seen after treatment with conventional steroid pulses. The patient was discharged on Nov 29, 1984. Complications consisted of four episodes of otitis media caused by Staphylococcus aureus and one rejection episode that was treated on an outpatient basis with an intravenous methylprednisolone sodium succinate pulse. Our experience emphasizes both the feasibility and importance of performing endomyocardial biopsies in infant recipients. Through biopsy, episodes of rejection can be discovered when clinical signs are not yet apparent. Eighteen months after transplantation, the child was developing and growing normally.

Cyclosporins↗
PubMed1986

Dysrhythmias after repair of atrial septal defect.

To determine the incidence of dysrhythmias following repair of isolated secundum atrial septal defect, postoperative electrocardiograms were reviewed in 292 patients. The PR interval was shortened by the 7th postoperative day (p <.05) as compared to the preoperative PR interval. Sinus rhythm only was observed in 228/292 (78%). Nine patients (3%) had a preoperative dysrhythmia. A postoperative dysrhythmia was observed in 64/292 (22%). Twenty-two (7.5%) had symptomatic postoperative dysrhythmias. A tachydysrhythmia was found in 16/64 (25%) of these. The latest occurrence of symptomatic dysrhythmia was 17 years after surgery. Currently, 7/292 (2.4%) of the patients reviewed have a pacemaker. Five of 292 (1.7%) had Holt-Oram syndrome. All five patients with Holt-Oram syndrome had postoperative dysrhythmias; two patients were symptomatic. Serious dysrhythmias may present years after repair of an atrial septal defect. Patients with Holt-Oram syndrome are at greater risk for development of postoperative dysrhythmias.

Journal Article↗
PubMed1985

Exercise testing in children with Wolff-Parkinson-White syndrome.

Exercise testing using a modified Bruce treadmill protocol was performed by 17 children with Wolff-Parkinson-White (WPW) syndrome. All had intracardiac electrophysiology studies as well. Endurance time, heart rate and blood pressure were normal during exercise. Ventricular premature complexes were seen with exercise in 2 patients and supraventricular tachycardia with exercise testing was seen in 2. Disappearance of the delta wave with exercise correlated with a long anterograde effective refractory period of the Kent bundle (360 to 390 ms). Children with partial normalization of the QRS during exercise had a longer anterograde effective refractory period of the Kent bundle than those in whom preexcitation persisted. In 1 patient, disappearance of the delta wave with exercise confirmed the diagnosis of WPW syndrome. Preexcitation was seen only after exercise in 1 patient. Exercise testing is of value in the evaluation of children with WPW syndrome; children with WPW syndrome who have total normalization of the QRS interval during exercise and few or no symptoms of tachycardia do not require electrophysiologic study.

Adolescent↗
PubMed1985

The use of exercise testing in children to evaluate abnormalities of pacemaker function not apparent at rest.

The purpose of this study was to evaluate the use of exercise testing in identifying abnormalities of pacemaker function and in confirming set parameters not apparent at rest in children with implanted atrial synchronous physiologic pacemakers. Maximal exercise tests were performed on 24 children (15 boys, 9 girls) from 4.5 to 18 years of age (median = 15) with physiologic pacemakers. The lower rate limit was observed before or following testing in 19 of 24 cases. In each case this correlated with the set lower rate limit. The upper rate limit was reached in 10 of 24 cases and was found to be lower than that programmed in one case in which a long atrial refractory period had limited the upper rate limit. Six children reached the maximum upper rate limit to which their pacemaker could be programmed. No abnormalities of atrial capture or ventricular capture occurred during exercise testing. Ventricular sensing was normal in each case. Atrial sensing was observed to be normal in 15 of the 24 cases. Two patients had decreased atrial sensing with exercise. Reversion to the "noise rate" due to myopotential inhibition was found in seven other cases. Subsequent tests on two of these children showed normal sensing.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗