Biomedical subjects
Publications and source records attributed to A B Taylor.
Patients with supraventricular tachycardia should be able to lead a perfectly normal life without significant treatment related side effects. Many of these patients have normal hearts and no other significant medical problems. Using the techniques described above, no patient should have significant symptoms from SVT.
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Thirty (10.8%) of 279 patients undergoing correction of a ventricular septal defect (VSD) from January, 1972, to September, 1986, also had a double-chambered right ventricle (DCRV). Age at operation ranged from 1.3 to 18.8 years (mean, 6.7 +/- 4.5 years [+/- standard deviation]). Seventeen patients were male, and 13 were female. Two-dimensional echocardiography was used after 1978 in the initial evaluation of 20 patients; however, the diagnosis of DCRV was made with the use of subcostal views only since 1984 in 4 of 5 patients. Surgical correction consisted of closure of the VSD and resection of anomalous muscle bundles through a right ventriculotomy (28 patients), and right atriotomy (2 patients). All patients survived and are asymptomatic 4.2 +/- 3.4 years following operation. Six patients have undergone catheterization postoperatively and 8 patients had intraoperative pressure recordings. The mean preoperative ratio of right ventricular to left ventricular pressures was 0.67 +/- 0.22 compared with 0.34 +/- 0.15 postoperatively (p less than .001). In 2 patients, DCRV was not recognized preoperatively or at VSD closure through a right atriotomy, and reoperation was necessary after DCRV was demonstrated at postoperative catheterization. DCRV may occur in approximately 10% of patients undergoing correction of VSD. Careful evaluation of echocardiographic and catheterization data preoperatively and careful evaluation of the anatomy intraoperatively are necessary so that DCRV not be overlooked, especially because most VSDs are now closed through the right atrium. Successful correction of VSD and DCRV is associated with excellent long-term results.
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From 1971-1981, 18 patients with discrete subaortic stenosis were treated surgically at the Medical University of South Carolina. Echocardiography was diagnostic in 10 of 11 patients in whom it was used. Preoperative cardiac catheterization was performed in all patients. The preoperative left ventricular outflow systolic pressure gradient was 82.0 +/- 27.2 mmHg (mean +/- SD) (range 30-145). In 16 (88.8%) patients excision of the subaortic membrane was complete, and relief of left ventricular outflow obstruction was good. The excision was incomplete in 2 patients; one required reoperation for residual gradient and developed complete heart block, and the other had a residual gradient of 60 mmHg and was in New York Heart Association functional class II when lost to follow-up. These data suggest that complete excision of the discrete subaortic stenosis is important to achieve good relief of left ventricular outflow obstruction.
We have shown that patch aortoplasty relieves the aortic pressure gradient substantially better than resection with end-to-end anastomosis in infants with coarctation of the aorta. Growth of the intact posterior wall of the unresected coarctation after aortoplasty, however, has not yet been demonstrated to occur. We studied 21 infants less than 2 years of age who underwent prosthetic patch repair of coarctation after 1975. Associated lesions were present in 16 patients, and 12 had a concomitant procedure. Two patients died in the hospital, and 4 died later, all of causes unrelated to the coarctation repair. Systolic blood pressure in the right arm declined from 140 +/- 41 mm Hg (mean +/- standard deviation) preoperatively to 101 +/- 19 mm Hg postoperatively in the whole group and to 95 +/- 12 in 10 patients followed for more than 3 years. The right arm-left leg systolic pressure gradient declined from 66 +/- 22 mm Hg to 5 +/- 14 in all patients and to 4 +/- 13 in the group followed more than 3 years. Hypoplastic transverse arch was seen in all but 2 patients. Its relative diameter increased in 6 of 9 patients who underwent catheterization postoperatively and increased more than 50% in 3 patients. Two patients have evidence of narrowing of the aorta at the patch, but both have normal blood pressure in the right arm. In the patient with longest follow-up, an 8-month-old infant seen 8 years after operation, angiograms show the diameter of the aorta at the coarctation to be greater than that at the transverse arch and at the descending aorta.(ABSTRACT TRUNCATED AT 250 WORDS)
Excellent clinical results have been achieved by both resection with end to end anastomosis and synthetic patch aortoplasty for the repair of coarctation of the aorta in older children. Increasing experience with exercise stress testing in the postoperative evaluation of patients with coarctation has allowed the discovery of less obvious differences between the two procedures. To evaluate these differences further, the stress tests of 50 postoperative patients who underwent coarctation repair were reviewed: 26 patients with end to end anastomosis and 24 with synthetic patch aortoplasty. Twenty normal control subjects were similarly exercised. Systolic blood pressure in the arm and leg was evaluated before and after the test. Heart rate, electrocardiogram and arm blood pressure were monitored during the test. The mean arm systolic blood pressure was higher at all points of measurement in the patients who underwent repair by end to end anastomosis than in the group who underwent patch aortoplasty. These systolic pressure differences reached statistical significance only for standing arm blood pressure before exercise (p less than 0.05) and for supine arm systolic blood pressure immediately after exercise (p less than 0.01). There was no difference in arm-leg pressure gradient between the two study groups before exercise; however, after exercise the group with end to end anastomosis had significantly higher arm-leg pressure gradients (p less than 0.001). Significant differences between the two types of repair not apparent at rest were found immediately after exercise. The long-term prognostic importance of an exercise-induced arm-leg blood pressure gradient remains to be determined. However, exercise stress testing is sensitive in demonstrating these differences.
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The effects of vitamin D, 2.5 mg (100,000 U)/d for 4 d, on serum calcium, serum 25-hydroxyvitamin D (25-OHD) and serum 1 alpha, 25-dihydroxyvitamin D (1 alpha, 25(OH)2D) were compared in 24 normal adults and 12 normal children. The daily dose of vitamin D was 1,500 U/kg body wt in children weighing less than 45 kg. Vitamin D increased mean serum calcium from 9.5 +/- 0.1 to 9.8 +/- 0.1 mg/dl (P less than 0.05), increased mean serum phosphorus from 4.6 +/- 0.1 to 5.0 +/- 0.1 mg/dl (P less than 0.01), increased mean serum 25-OHD from 25 +/- 3 to 34 +/- 4 ng/ml (P less than 0.001), and increased mean serum 1 alpha, 25(OH)2D from 34 +/- 3 to 42 +/- 4 pg/ml (P less than 0.02) in children. In contrast, vitamin D increased mean serum 25-OHD from 18 +/- 2 to 39 +/- 6 ng/ml (P less than 0.001) and did not change mean serum calcium (9.4 +/- 0.1 vs. 9.5 +/- 0.1 mg/dl), mean serum phosphorus (4.0 +/- 0.1 vs. 4.1 +/- 0.1 mg/dl), or mean serum 1 alpha, 25(OH)2D (31 +/- 2 vs. 29 +/- 3 pg/ml) in adults. Mean serum 1 alpha, 25(OH)2D was significantly higher after vitamin D in children than in adults (P less than 0.02). These results provide evidence that circulating 1 alpha, 25(OH)2D is not as tightly regulated in children as it is in adults. This difference in regulation could account in part for the higher values for serum 1 alpha, 25(OH)2D observed in children.
Epidural injections were performed by obstetricians on 1012 patients in a pain relief service in which there was clinical co-operation between anaesthetists and obstetricians. A consultant anaesthetist collaborated in the training of staff providing the service. Midwives maintained the epidural analgesia with top-up doses as part of their traditional role in providing pain relief in labour. Eight-eight per cent of patients were fully satisfied, 10% were helped and 2% had failed epidurals. The forceps rate was 30% and the dural tap rate 1.4%. Junior obstetric staff in training grades can with adequate safeguards make a significant contribution to running an obstetric epidural service.
Hypoplasia of the pulmonary arteries has been cited as a contraindication to right vertricular bypass operations. We have successfully corrected a lesion in which the left pulmonary artery was severely hypoplastic and have documented a good hemodynamic result postoperatively. Size of pulmonary arteries is less important than pulmonary vascular resistance as a criterion for orthoterminal correction.
The nucleoli of rat liver cells duplicate in great detail the life-long series of reorganizational changes encountered in kidney and intestinal epithelial cells. The ultrastructural components of the large, loosely organized polymorphous nucleoli, which are dominant in the rapidly multiplying stem cells of embryos, are readily accessible for chemical activities. Smaller, more compact amphinucleoli are dominant in more mature cells, which were characterized by Smetana ('70) as "idling" cells, showing slowly continuing ribosome formation and RNP synthesis. In older cells bipartite nucleoli become dominant and are reorganized in increasing numbers from the younger amphinucleoli. These, however, are not replaced in equal numbers from the shrinking pool of polymorphs of young cells which have greatly reduced mitotic potential. Paralleling the shifts in dominant nucleolar types, the high level of protein synthesis declines in older cells not only in the quantity of proteins synthesized but also in kinds of enzymes produced. These fail to meet the structural and functional requirements of aging cells leading ultimately to the onset of age-related degenerative changes. Again it is noted that separation of the karyosomal DNA from the plasmosomal RNA-protein complex of the nucleolus may lead to possible breakdown of the DNA-dependent RNA-protein transcription system ultimately bringing protein synthesis to a very low level in the senescent animal.
Heart rate, systolic and diastolic blood pressure, rate-pressure product and electrocardiographic changes were measured in 288 healthy children during treadmill exercise. A constant speed (3.5 miles/hour) protocol was used to facilitate the measurements of physiologic data during exercise. Because responses to exercise vary with size, the children were separated into four groups according to body surface area. Comparisons were also made between male and female and between black and white children. The values for heart rate and systolic pressure showed excellent reproducibility in repeated tests. These data establish for clinical use reference values for children during treadmill exercise.
We repaired coarctation of the aorta in a group of 18 children less than 3 years old, using either resection with end-to-end anastomosis (8 patients, Group 1) or patch graft aortoplasty (10 patients, Group 2). The two groups were similar preoperatively in age, pressure difference between proximal and distal aorta (delta PA0), and severity of aortic arch hypoplasia. Three patients, all less than 2 months old, died early postoperatively. Among the survivors, the right brachial artery systolic pressure was significantly higher in Group 1 (133.1 +/- 7.0 mm Hg) (mean +/- standard error of the mean) than in Group 2 (102.5 +/- 7.2 mm Hg) (p less than 0.05). The delta PA0 was significantly higher in Group 1 (33.0 +/- 7.5 mm Hg) than in Group 2 (5.1 +/- 2.3 mm Hg) (p less than 0.01). Three patients in Group 1 required reoperation and were treated with patch graft aortoplasty; relief of delta PO0 was complete in 2. Patch graft aortoplasty is more effective than resection in reducing proximal aortic systolic pressure and in relieving delta PA0 in infants and small children with coarctation of the aorta.
Replacement of cardiac valves in children has been associated with high rates of mortality and morbidity in the past. We have compared 24 children from 2 to 18 years of age who have received mechanical valves with 24 children who have received porcine valves. The groups were similar except that (1) there were more mitral operations in the mechanical valve group and more aortic operations in the porcine valve group; (2) more porcine than mechanical valves were implanted in recent years; and (3) the porcine valve group comprised more young patients under 8 years and required more complex operations. Early and late mortality rates were higher in the mechanical than in the porcine valve group. Major late complications were seen in 50 percent of the mechanical valve group and 13 percent of the porcine group. Implantation of an adult-sized aortic valve was made possible in all patients by the use of aortic augmentation annuloplasty. Higher operative mortality rates in the mechanical valve group may have been related more to technique of myocardial preservation during operation than to type of valve. Although differing rates of late morbidity and mortality may also have been related to myocardial preservation and other technical factors, the type of valve used seemed to be an important determinant of the better results in the porcine group. Despite unknown durability of the porcine valve, our data suggest that the safest prosthetic valve to use in children at this time is the glutaraldehyde-fixed porcine prosthesis.
Of 309 consecutive cases of epidural analgesia provided by obstetricians, 250 set up by junior obstetric staff. Midwives managed the epidural analgesia and gave the top-up doses as part of their traditional role in providing pain relief in labour. This practice was thought to be influential in producing a high sponn epidural analgesic service can safely be provided by obstetricians in a small maternity hospital.
Electrotonic spread of applied potentials was observed between longitudinal and circular muscle layers of the small intestine with no rectification. Nexal junctions were demonstrated between muscle fibers of each layer. Connective tissue cells bridged between the two muscle layers. These showed structural characteristics of fibrocytes and of interstitial cells. Some nexuses were seen between connective tissue cells and between these cells and muscle fibers of each layer but in most junctions the membranes were 10-18 nm apart. Since connective tissue can serve for electrical conduction between cultured heart cells and since electrical properties of intestinal muscle permit transmission with low degrees of coupling, it is suggested that interstitial cells and fibrocytes may electrically couple longitudinal and circular muscle layers of cat intestine.
A process of nucleolar reorganization apparently identical to that encountered in intestinal epithelial cells (Adamstone and Taylor, '72) develops in kidney cells of aging rats. The polymorphic nucleoli of young tubule cells soon change to amphinucloeli and, while terminal nucleolar reorganization is delayed in cells of collecting tubules, in the nephrons nucleoli soon begin to undergo terminal reorganization becoming bipartite structures with separate plasmosomes and karyosomes. This suggests disruption of the DNA-dependent RNA protein transcription system and failure to maintain the flow of messenger RNA into the cytoplasm. Old cells are not discarded immediately from the kidney tubules and they retain much rough endoplasmic reticulum, numerous ribosomes and polysomes and large plasmosomes. Thus a high RNA concentration is known to develop in old kidney tissue while protein synthesis is also known to be low (Kanungo et al., '70; Buetow and Ghandi, '73). Nucleolar counts show gradual increase in bipartite nucleoli at the expense of amphinucleoli and in the senescent kidney bipartite nucleoli predominate. It is suggested that nucleolar reorganization, with final separation of plasmosomes and karyosomes, includes the process of nucleolar segregation and is triggered by some innate nucleolar mechanism in response to encoded genetic information stored in the nucleolus during nucleogenesis. At this time both DNA and RNA are incorporated into the developing nucleolus. It is also to be noted that two shifts in nucleolar dominance occur with advancing age. These may be fundamental to the process of aging and to the onset of senescence. Furthermore, the changes in dominant nucleolar types are the direct result of the process of nucleolar reorganization.