Current Status of Pacemaker Power Sources

After years during which pacers of very similar design and capabilities were provided by a small number of manufacturers, many different lithium, halogen, rechargeable, and nuclear power sources are now available. The variety of chemistries, methods of construction, and sealing techniques used in the batteries of the different manufacturers is almost unlimited. This has made it necessary for physicians who implant and follow pacers to acquire a general knowledge of the field if they are to make an informed choice of pacemaker power source for implantation and if they are to manage recalls with a minimum of patient and physician trauma. More experience is required before it can be definitely determined which of the new pacer power sources will prove superior, but when coupled with well-designed, hermetically sealed pulse generators, all are capable of providing continuous pacing for at least 5 years and the 10-year pacemaker is now a probability.     

Myocardial stimulation impedance: the effects of electrode, physiological, and stimulus variables.

With exposed metal at the electrode tissue interface (8 mm2, 28 mm2, 57 mm2), myocardial threshold stimulation impedance increased as pulse duration was lengthened, with left ventricular intramyocardial stimulation, and with the smaller surface area electrode. An 0.5 mm2 differential-current-density electrode, which eliminated direct metal-to-tissue contact at the electrode-myocardial interface, was associated with notably higher impedances than each of the three metal tip electrodes and did not show increasing impedance levels with changes in pulse duration, confirming the minimization of polarization energy losses with this device. The majority of electrode, electrode tissue interface, and myocardial variables that are characterized by high threshold stimulation impedance are associated with low threshold energy requirements for pacing and reduced pacemaker power source drain. No accurate information about sensing impedances can be derived from current knowledge of pacing impedance.     

Management of Nontraumatic Chylothorax

Twenty-two patients with chylothorax have been treated at the National Institutes of Health since 1955. In 9 of these patients, the condition resulted from an antecedent operation and in 13, it occurred without a history of prior operation (nontraumatic). All 6 of the patients with tumors in whom nontraumatic chylothorax developed had a lymphoma. Four of these 6 also had a chylous ascites, while 6 of the 7 patients without tumors had an associated chylous ascites.Only 3 of the 13 patients with nontraumatic chylothorax responded to nonoperative therapy alone with stabilization of the pleural effusions. A single patient with systemic lupus erythematosus responded to steroid therapy. In contrast, 3 of 4 patients who underwent thoracotomy for nontraumatic chylothorax had permanent relief of their chylous pleural effusions.In the absence of medically treatable disease, thoracotomy with ligation of the thoracic duct and/or pleurectomy or pleurodesis can provide substantial palliation for patients with nontraumatic chylothorax, even when a discrete source of lymph leakage cannot be localized or ascites is present. Early surgical therapy of nontraumatic chylothorax is advocated in such circumstances.     

Intrapleural instillation of quinacrine for treatment of recurrent spontaneous pneumothorax.

We used intrapleural instillation of quinacrine hydrochloride in 20 patients (Group A) with recurrent spontaneous pneumothorax (one bilateral) and compared their clinical course with 19 patients who underwent thoracotomy and scarification or pleurectomy (Group B) and 63 patients treated by tube thoracostomy alone (Group C). In Group A, there was one complication of treatment, a pneumothorax immediately following tube removal, which necessitated repeat tube thoracostomy, and there was one late ipsilateral recurrence 2 years after treatment. These 20 patients with 21 recurrent spontaneous pneumothoraces treated with intrapleurally administered quinacrine have been followed for from 6 months to more than 4 years with only one late recurrence on the treated side. Eight patients in Group B had postoperative complications: 2 patients who had had pleurectomy required reoperation for postoperative bleeding; lobar pneumonia developed in 3; 1 had lack of total expansion of the lung; an intrathoracic hematoma developed in 1; and an ipsilateral pneumothorax necessitating tube thoracostomy developed in 1. In Group C, the rate of recurrence of pneumothorax was 23% during the first year following treatment. Intrapleural instillation of quinacrine is a simple, low-risk, reliable, and effective treatment for recurrent spontaneous pneumothorax, and is equally as effective as thoracotomy and scarification.     

Use of Cold Cardioplegic Solution for Vein Graft Distention and Preservation: A Light and Scanning Electron Microscopic Study

To evaluate the effect of a cardioplegic solution on the endothelium of the saphenous vein, portions of this vein were harvested from each of 5 patients undergoing coronary artery bypass operation. Each sample was divided into five segments. One segment was distended with heparinized saline solution, one with heparinized blood, and one with heparinized cardioplegic solution (25 mEq of potassium per liter). All of the distending solutions were kept at 10°C, and pressure was carefully limited to 200 mm Hg. The fourth segment of vein was distended with heparinized saline solution but no effort was made to limit distending pressure, and the fifth segment was not distended. All samples were then examined with light and scanning electron microscopy.There were no great morphological differences in the endothelium of veins distended to 200 mm Hg with saline solution, blood, or cardioplegic solution. The morphology of these samples compared favorably with the control vein endothelium although scattered areas of endothelial disruption were present in every sample. Veins distended without pressure control showed massive endothelial disruption. The particular solution used to distend the saphenous veins is not as important as limiting the distending pressure.     

Inhibition of gastrin release and gastric secretion by calcitonin in patients with peptic ulcer

We studied the effect of an intravenous infusion of calcitonin (2 MRCU/kg) on gastric secretion and serum gastrin and serum calcium levels in eight normal subjects, six patients with duodenal ulcer disease, three patients with primary hyperparathyroidism, six patients with histologically proved Zollinger-Ellison syndrome, and three patients with the Zollinger-Ellison syndrome and hyperparathyroidism. Gastric secretion was greatly inhibited in all groups of patients. Serum calcium was significantly diminished only in patients with hypercalcemia. Serum gastrin levels were depressed in all patients with elevated basal gastrin levels (DU, HPT, Z-E, and ZE + HPT). In normal subjects calcitonin inhibited strongly the serum gastrin response to food. These findings suggest that calcitonin may have a regulatory function in the release or catabolism of the hormone gastrin.     

Depletion of antral gastrin after food in rats.

The results of these studies indicate that in fasting rats, there is an abrupt and prolonged rise in circulating gastrin after feeding. This increase in serum gastrin is accompanied by an early (five minutes) diminution in antral gastrin which is followed by slightly higher and more variable antral gastrin values. These findings suggest that feeding triggers the release of gastrin with early depletion of antral gastrin and that, subsequently, gastrin syhthesis and release interact cyclically to maintain antral and serum concentrations of gastrin. Antral, fundic, and duodenal gastrin values in rats are similar to those reported in dogs and cats. The jejunum of the rat contains little, if any, gastrin.     

Surgery of left paraduodenal hernia

The clinical presentation, embryologic and etiologic factors, and repair of left paraduodenal hernia are presented. A new operative procedure for cure of left paraduodenal hernia is presented that deals effectively with the sac and predisposing arch containing the inferior mesenteric vein without section of the vein. Repair is based upon the embryologically normal anatomy with restoration of the inferior mesenteric vein to its normal retroperitoneal position. This procedure has been successfully utilized in a case in which the paraduodenal hernia of small bowel was encountered concomitantly with a perforated duodenal ulcer.     

The Blalock-Taussig Shunt in the First Two Years of Life: A Safe and Effective Procedure

Many surgeons have been reluctant to perform Blalock shunts in patients who are in infancy or early childhood (< 24 months old) and have done instead direct aortopulmonary anastomoses. Recently, others have advocated complete repair of tetralogy of Fallot in early infancy because of the high mortality of direct aortopulmonary shunts. We believe the Blalock-Taussig anastomosis is a safe and effective palliative procedure for all infants with inadequate pulmonary blood flow regardless of size.During the past nine years, 24 babies less than 2 years old who were followed had construction of Blalock-Taussig anastomosis for inadequate pulmonary blood flow. There were no operative deaths and no shunt-related late deaths. Of the 24 babies, 12 were less than 12 months old. Eighteen of the 24 had tetralogy of Fallot. The remaining 6 had a variety of lesions with inadequate pulmonary blood flow. The mean weight of the entire group was 7.3 ± 1.6 kg. Of those infants less than 12 months old, the mean weight was 6.8 ± 2.0 kg. More than 6 months following construction of the shunt, 2 babies died from sepsis unrelated to cardiovascular status. All infants had adequate but not excessive pulmonary blood flow after shunting. There were no late shunt failures.     

Prevention of upper gastrointestinal hemorrhage in 582 burned children.

In 582 burned children, neutralization of gastric acid and reduction of psychic stress were utilized to reduce upper gastrointestinal ulceration and hemorrhage. While receiving milk, diazepam, and psychologic support, two children required operation. Two of the children who died without clinically apparent gastrointestinal disease had ulcers discovered at autopsy. We conclude that a prophylactic regimen that reduced the amount of acid bathing the gastroduodenal mucosa, provides adequate calories, and minimizes psychic stress is useful in preventing gastrointestinal hemorrhage after burns.     

Suppression of gastric secretion and serum gastrin by gastrin antibody.

Fourteen dogs received varying doses of antigastrin antibody; after a single dose of 0.07 ml/kg, circulating gastrin levels could not be measured for as long as forty-seven days. Gastric secretion in response to food was not diminished by antigastrin antibody doses as high as 0.07 ml/kg daily for ten days. Larger doses, 0.2 and 0.4 ml/kg, were required to produce a temporary reduction in gastric-stimulated gastric acid secretion. Mucosal levels of gastrin in the antrum, fundus, and duodenum were greatly increased ten days after injection of antigastrin antibody. The therapeutic use of antigastrin antibody to control gastric secretion seems at the present time not feasible because of the scarcity of the antigastrin antibody and because large doses aare required to obtain only a temporary effect.     

Unchanged pulmonary capillary filtration coefficients after Escherichia coli endotoxin infusion

The pulmonary capillary filtration coefficient (K_f,c) was measured in intact, anesthetized dogs before and after the intravenous administration of alloxan and E. coli endotoxin. The method used to measure K_f,c was that of determining the capillary filtration rate by analyzing the weight transient following a change in capillary pressure (ΔP_c) and dividing the initial filtration rate by ΔP_c. In four dogs given 75 mg/kg of alloxan, the K_f,c increased 10-fold. This indicated that the capillary membranes were damaged by the alloxan and that, by using this method of measuring K_f,c, changes in K_f,c were easily detected. The K_f,c, measured after a 3-hr continuous infusion of a total of 4 mg/kg of E. coli endotoxin [0.35 ± 0.21 (SD) ml/min/mm Hg/100g], was not different from the value found in the same animals before the endotoxin (0.33 ± 0.29). Since the K_f,c is a sensitive indicator of capillary membrane pore size, these results strongly suggest that E. coli infusion did not damage the pulmonary capillary membrane.     

Pericardiodiaphragmatic hernia

Twenty-seven reported cases of pericardial diaphragmatic hernia are reviewed and another case is added. This entity may be congenital or traumatic in origin, the latter being more frequent at a ratio of 2:1. All patients except one were male and the mean age at diagnosis was 40 years. The patients were usually symptomatic, the most frequent complaints being of cardiac or respiratory origin. Pneumoperitoneum may be diagnostic although chest roentgenograms and contrast studies may suggest the diagnosis. Computed axial tomography and echocardiography may prove useful in the future. We believe the anterior abdominal approach is preferable to the transthoracic approach in reducing the hernia and repairing the defect because it affords better exposure and easier accessibility to other intraabdominal disease and can easily be converted into a median sternotomy if needed. The stomach and transverse colon became herniated most frequently and in only three cases was a sac found. The defect involves the central leaflet of the diaphragm and primary repair generally results in a good prognosis.     

Arterial injuries of the legs associated with fractures and dislocations

Twenty-nine patients with vascular injuries of the leg associated with fractures and dislocations were reviewed. The overall limb salvage rate was 69 percent and the amputation rate 31 percent. These rates are usually directly related to delay in diagnosis and treatment. Routine arteriography is recommended in all patients with the slightest signs of ischemia. Prompt diagnosis followed by prompt vascular repair and fracture fixation will result in greater limb salvage.     

Effect of alcohol on the release of cholecystokinin and pancreatic enzyme secretion

Ethanol is often implicated in the pathogenesis of acute pancreatitis, but the pathophysiologic processes of alcohol-induced acute pancreatitis remains poorly understood. We found that ingestion of alcohol by healthy volunteers did not stimulate release of cholecystokinin, which is the chief hormonal stimulant of pancreatic enzyme secretion, nor did it significantly alter fasting levels of pancreatic polypeptide, a hormonal inhibitor of pancreatic enzyme secretion. In conscious dogs prepared with chronic pancreatic fistulas, direct intraduodenal instillation of ethanol significantly reduced pancreatic protein output, and this reduction corresponded to a decline in plasma concentrations of cholecystokinin that was similar in the percentage of diminution and in duration. These data suggest that, in patients who do not have chronic pancreatitis, alcohol does not induce acute pancreatitis, either by stimulating cholecystokinin release or by stimulating enzyme secretion directly.     

Prevention and management of contractures in patients with burns of the neck

Two hundred patients with neck burns were analyzed to determine the incidence of contractures. It was found that only 8 per cent of patients with second degree burns had contractures, all of which were mild. Both the overall incidence of cervical contractures in patients with third degree neck burns and their severity can be decreased by the use of a custom-formed isoprene splint. Splinting should begin as soon as possible after the burn and continue until scar maturation is complete.     

Regulation of gastric acid secretion by secretin and serotonin

We have tested the interaction between serotonin and secretin in pentagastrin-induced gastric acid secretion in six dogs prepared with Thomas gastric and duodenal cannulas. We further examined the effect of methysergide, a serotonin antagonist, on gastric acid secretion. The intravenous administration of serotonin or secretin alone significantly inhibited pentagastrin-induced gastric acid secretion. The combined administration of serotonin and secretin inhibited gastric acid secretion to a greater magnitude than either secretagogue alone. The administration of methysergide diminished basal concentrations of secretin on gastric acid secretion. Methysergide also enhanced the stimulatory activity of pentagastrin-induced gastric acid secretion. The inhibitory action of intraduodenal acidification of pentagastrin-induced gastric acid secretion was reversed by methysergide.