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Biomedical subjects

V L Gott

Publications and source records attributed to V L Gott.

At least 127 records · Page 7Linked to original sources
PubMed1977

Myocardial ischemia during cardiopulmonary bypass. The hazards of ventricular fibrillation in the presence of a critical coronary stenosis.

The effect of a critical coronary artery stenosis on myocardial blood flow and metabolism in the fibrillating heart was assessed by placing 10 dogs on cardiopulmonary bypass, venting the ventricle, inducing ventricular fibrillation, and applying critical stenosis to the left anterior descending coronary artery (LAD). Endocardial and epicardial blood flows were measured by the radioactive microsphere technique prior to the application of the stenosis and after one hour and 2 hours of fibrillation. Intramyocardial oxygen tension (PO2) and carbon dioxide tension (PCO2) were continuously monitored in the LAD-supplied myocardium by a mass spectrometer probe inserted at midmyocardial depth. Selective arterial-coronary venous lactate differences were determined at control, one hour, and 2 hours. At the end of the 2 hour period, vital dye injection defined the distribution of the LAD. Endocardial flow to the myocardium of the stenosed LAD was reduced by 50 per cent after one hour and by 70 per cent after 2 hours (p less than 0.05). Epicardial flow fell 40 per cent after one hour and 50 per cent after 2 hours (p less than 0.05). Endocardial and epicardial flow in the distribution of the unstenosed circumflex coronary artery remained unchanged. Changes in myocardial PO2 and PCO2 in the LAD-supplied myocardium indicated the development of severe ischemia in all 10 dogs and suggested myocardial infarction in 5. There was a conversion from lactate extraction to lactate production during the 2 hour period of ventricular fibrillation. From this study, it is concluded that the myocardium distal to a critical stenosis suffers a progressive reduction in flow during ventricular fibrillation which does not occur in regions supplied by unstenosed coronary arteries. Thus prolonged fibrillation in the presence of a flow-limiting coronary stenosis may play a role in the pathogenesis of myocardial infarction during coronary bypass surgery.

Animals↗
PubMed1977

Regional ischemia distal to a critical coronary stenosis during prolonged fibrillation--improvement with pulsatile perfusion.

In a previous study from this laboratory, regional myocardial ischemia developed distal to a critical coronary stenosis in the fibrillating heart on cardiopulmonary bypass when myocardial perfusion was non-pulsatile. To assess the effect of pulsatile perfusion on the development of the fibrillation-induced ischemia, 10 dogs were placed on total cardiopulmonary bypass with the heart in the vented fibrillating state. A critical stenosis was applied to the left anterior descending artery (LAD). Pulsatile perfusion with a pulse pressure of 35 mm Hg and a pulse rate of 100/min was produced by a new method developed in this laboratory. During the 2 hours of bypass, ischemia in the LAD-supplied myocardium was assessed by changes in intramyocardial oxygen (PmO2) and carbon dioxide (PmCO2) tensions and by regional arterial-coronary venous lactate difference. With linear perfusion, regional ischemia in the LAD myocardium had been evidenced by a low PmO2 (8 +/- 3 mm Hg), a high PmCO2 (170 +/- 25 mm Hg) and regional lactate production (9.2 +/- 4.2 mg/100 ml). In contrast with pulsatile perfusion intramyocardial gas tensions remained stable during the 2 hours on bypass (PmO2 = 21 +/- 3 mm Hg, PmCO2 = 65 +/- 5 mm Hg, P less than 0.05 vs linear flow study) and lactate consumption was demonstrated (+17.7 +/- 2.9 mg/100 ml, P less than 0.001 vs linear flow group). With linear perfusion, myocardial blood flow to the LAD area had decreased 56 +/- 8% in the subendocardial layer and 46 +/- 7% in the subepicardial layer. In the dogs receiving pulsatile flow during bypass, regional LAD blood flow remained unchanged over the 2-hour bypass period and was significantly higher than the flow with linear flow (P less than 0.05). These data indicate that fibrillation-induced regional myocardial ischemia distal to a critical stenosis can be prevented by maintaining pulsatile perfusion during cardiopulmonary bypass.

Animals↗
PubMed1976

Permanent cardiac pacemakers in children: technical considerations.

Placement of permanent cardiac pacemakers in children presents technical problems that are not encountered in the adult. Problems unique to pacemaker implantation in children are related to the patient's size, the relative bulkiness of pulse generators, the lack of subcutaneous tissue, and the child's growth and long life expectancy. Based on our experience with implantation of 27 permanent cardiac pacemakers in 13 children, we have found that the use of small pulse generators, placement of epicardial leads, insertion of properitoneal pulse generators, and use of recharabeable pacemakers are satisfactory methods in children.

Adolescent↗
PubMed1976

Kartagener's syndrome with corrected transposition. Conducting system studies and coronary arterial occlusion complicating valvular replacement.

An 18-year-old man whose sister has classic Kartagener's syndrome was found to have sinusitis, bronchiectasis, and corrected transposition with normal visceral situs. Congenital complete heart block was secondary to absence of conducting-system pathways between a small posterior atrioventricular node and the transposed His bundle and bundle branches. No anterior atrioventricular node was present. Prosthetic valvular replacement of the left-sided (morphologic right) atrioventricular valve was complicated by coronary arterial occlusion by suture, with subsequent myocardial infarction. The case appears to represent an unusual variant of Kartagener's syndrome with the abnormality of laterality being expressed as corrected transposition.

Adolescent↗
PubMed1976

Fatal cerebral atheromatous embolization after cardiopulmonary bypass.

Cholesterol embolization to the abdominal viscera is common. Fatal cholesterol embolization to the central nervous system is rare. This report describes a 55-year-old woman with severe atherosclerotic disease who underwent cardiac surgery during which she suffered a fatal cerebrovascular accident. Postmortem examination revealed multiple infarcts in the brain, eye, and spleen due to emboli of cholesterol crystals and other atheromatous debris from a ruptured atherosclerotic plaque in the ascending aorta at the site of an aortotomy for cardiopulmonary bypass. In patients known to have severe atherosclerotic disease, atheromatous embolization to the central nervous system should be regarded as a potential complication of surgical manipulation and incision of the aorta for cardiopulmonary bypass. Ophthalmoscopic examination may be of diagnostic value in such cases.

Arteriosclerosis↗
PubMed1976

A new method of producing pulsatile flow during cardiopulmonary bypass using a standard roller pump.

A new method for producing pulsatile flow during cardiopulmonary bypass is described. The method requires only the addition of a dilated segment in the tubing which passes beneath the arc of a standard roller pump. Preliminary studies demonstrate that pulsatile flow and pressure with physiologic contours can be produced by this "bubble tube" system. Furthermore, the new tubing causes less hemolysis than standard pump tubing.

Animals↗
PubMed1975

Thromboresistance of glass after glow discharge treatment in argon.

Glow discharge treated (GDT) inorganic materials are sterile and free of all organic contaminants. Such materials implanted in the canine inferior vena cava often demonstrate significant thromboresistance. Standard Pyrex glass tubing was GDT in argon to provide a surface free energy above 70 dynes/cm, slight surface negativity, and other surface-physical modifications of its interface. Chromic acid cleaned lengths of the same tubing, and short segments whose edges were not fire-polished were used as controls. Upon canine implantation, the in vivo results were similar in independent surgical laboratories. The glass was implanted as 1.4 cm long rings or as 5 cm long tubes in separate medical centers according to different protocols. GDT specimens remained patent; all controls accumulated thrombi. A remarkably pure, low critical surface tension, labile protein coating covered all cylindrical lumens after 2 hr in vivo. This coating diminished within 2 weeks and was essentially absent after 480 days, eeven though scanning EM showed evidence of a micron thick luminal film, probably eroding glass. No emboli were found in the implant animal's kidney or lungs at any stage.

Animals↗
PubMed1975

Current status of the Beall, Bjork-Shiley, Braunwald-Cutter, Lillehei-Kaster and Smeloff-Cutter cardiac valve prostheses.

The Starr-Edwards ball valve prosthesis is generally the standard by which other cardiac valve substitutes are compared. This report reviews information pertaining to several prostheses--the Beall mitral valve and the Bjork-Shiley, Braunwald-Cutter, Lillehei-Kaster and Smeloff-Cutter aortic and mitral valves--considered by some to have specific advantages over the Starr-Edwards valves. Hospital and late mortality rates after valve replacement are comparable for the four aortic valve prostheses reviewed and depend more on patient selection than on the specific prosthesis utilized. Extensive clinical experience with the Bjork-Shiley aortic valve indicates that this prosthesis offers hemodynamic advantages over ball valve prostheses, especially in patients with a small aortic root. Clinical experience with the Lillehei-Kaster pivoting disc prosthesis has been less extensive, but this model provides theoretical hemodynamic advantages similar to those of the Bjork-Shiley aortic valve prosthesis. Problems associated with cloth wear and the unexpectedly slow rate, in man, of tissue ingrowth into the fabric of the Braunwald-Cutter aortic valve prosthesis have been discouraging, although this prosthesis has been associated with a very low thromboembolic rate in patients receiving anticoagulant therapy. The Smeloff-Cutter aortic prosthesis is hemodynamically similar to the Starr-Edwards prosthesis and has been proved to be a reliable and durable aortic valve substitute over the past several years. Mortality after mitral valve replacement is also largely influenced by factors other than prosthetic valve design. On the basis of postoperative data, the five mitral valve prostheses reviewed do not appear to have substantial hemodynamic differences. For patients with a small left ventricular cavity the low profile prostheses, such as the Beall, Bjork-Shiley and Lillehei-Kaster, may be advantageous. Most available evidence indicates that patients receiving aortic or mitral valve prostheses should be given anticoagulant therapy postoperatively.

Anticoagulants↗
PubMed1975

The "angina-producing" myocardial segment: An approach to the interpretation of results of coronary bypass surgery.

The first 153 cases of saphenous vein aortocoronary bypass surgery performed at The Johns Hopkins Hospital were reviewed. Eighty-eight percent of the 140 late survivors reported significant symptomatic improvement. Seventy-one unselected patients consented to complete reevaluation at a mean interval of 6.1 months postoperatively. Vein bypass patency in this group was 66 percent. Eighty-two percent of these 71 patients had improved performance on electrocardiographic stress testing. There were no significant differences between hemodynamic status on pre- and postoperative studies regardless of the status of vein bypass patency. Repeat coronary angiography revealed a 30 percent incidence of new total occlusions of the intrinsic coronary circulation. Segmental wall motion on ventriculography was improved in 12 percent, unchanged in 50 percent and decreased in 38 percent of the segments analyzed. Localized electrocardiographic changes compatible with myocardial damage developed in the immediate postoperative period in 45 of these patients (63 percent); in 38 of the 45, these changes corresponded to new angiographic abnormalities. Physiologic mechanisms underlying symptomatic improvement were sought by identification of an "angina-producing" myocardial segment. In most instances, alleviation of angina could be related to either: (1) a patent bypass graft into an unchanged intrinsic coronary artery with presumed increased blood flow to the distal coronary segment, or (2) occlusion of the bypass graft and the corresponding coronary artery with probable infarction of previously ischemic myocardium. Current criteria for the selection of patients undergoing coronary bypass surgery are reviewed in the light of these findings. It is concluded that relief of disabling angina is the major indication for surgery. Prevention of myocardial infarction and improvement in left ventricular function are at present less reliable objectives.

Angina Pectoris↗
PubMed1975

Factors influencing survival following postinfarction ventricular septal defects.

Postinfarction ventricular septal defect (VSD) carries a grave prognosis. Surgical closure appears to improve survival. Eighteen patients with postinfarction VSD are reviewed. Nine died before operation could be performed and 9 underwent closure of the VSD; 4 patients are late survivors. Factors which appear to influence survival are: (1) time of surgical intervention after appearance of VSD, (2) presence or absence of cardiogenic shock, (3) location of the infarct, and (4) operative approach to the VSD. Based on these factors, a method of management for postinfarction VSD is outlined.

Aged↗
PubMed1975

A simple model of the hemodynamic effects of a proximal coronary artery narrowing.

A simple mathematical model of the hemodynamic effects of a discrete proximal coronary artery obstruction is presented. The model demonstrates that resting myocardial flow demands fail to be met when the vessel diameter is decreased by 75% or greater. More strikingly, it shows that the maximum flow obtainable for increased myocardial oxygen demand begins to fall significantly with a lesion causing a 40 to 50% obstruction. The implications of these findings in relation to stress-induced angina are discussed.

Coronary Circulation↗
PubMed1975

The effect of cardiopulmonary bypass perfusion pressure on myocardial gas tensions in the presence of coronary stenosis.

Mass spectrometry was utilized to determine myocardial gas tensions in dogs subjected to cardiopulmonary bypass. Myocardial ischemia occurred in animals with normal coronary arteries when cardiopulmonary bypass perfusion pressure fell 40 to 60 mm Hg below the mean aortic pressure measured prior to bypass. Myocardial ischemia did not occur, or could be eliminated when present, if cardiopulmonary bypass perfusion pressure was maintained near prebypass mean aortic pressure. In animals with constricted circumflex coronary arteries, the adverse effect of low perfusion pressure on myocardial metabolism during cardiopulmonary bypass was found to be more severe in areas of myocardium supplied by the stenotic coronary artery. It is concluded that maintenance of cardiopulmonary bypass perfusion pressure near the level of preoperative mean aortic pressure will help prevent myocardial ischemia during operation; particularly in patients with coronary artery disease.

Animals↗
PubMed1975

Changes in intramyocardial ST segment voltage and gas tensions with regional myocardial ischemia in the dog.

This study was designed to evaluate the sensitivity of changes in myocardial carbon dioxide and oxygen tensions as indicators of regional myocardial ischemia and also to determine to what extent these changes can be related to changes in intramyocardial ST segment voltage. Changes in ST segment voltage recorded in unipolar epicardial electrodes proved to be a less-sensitive indicator of underlying myocardial ischemia than were changes in ST segment voltage recorded in unipolar intramyocardial electrodes. In 9 dogs, regional ischemia was produced by placing a variable constrictor on the left circumflex coronary artery; circumflex flow was monitored. Myocardial carbon dioxide and oxygen tensions were measured using a mass spectrometer. Unipolar electrograms were recorded using a multicontact plunge electrode. With progressive degrees of proximal stenosis, ranging from a critical stenosis, which is associated with a decrease in mean flow of less than 15%, to a severe stenosis associated with and 80% decrease, ST voltage increased 21 mv and carbon dioxide tension increased 84 mm Hg, but oxygen tension decreased only 7 mm Hg. The study suggests that increases in intramyocardial ST segment voltage, an index of myocardial ischemia, are associated with parallel increases in myocardial carbon dioxide tension, each providing a more sensitive quantitative correlate of regional myocardial ischemia than do decreases in oxygen tension. The local accumulation of carbon dioxide may be an important pathophysiological mechanism in myocardial ischemia.

Animals↗
PubMed1975

Mass spectrometry for the measurement of intramyocardial gas tensions: methodology and application to the study of myocardial ischemia.

The methodology for use of the mass spectrometer for the measurement of intramyocardial gas tensions in the canine preparation is described. Baseling studies were carried out initially in 36 animals, and control levels for myocardial oxygen tension and myocardial carbon dioxide tension were 19 mm Hg (S.D. 6 mm Hg) and 43 mm Hg (S.D. 10 mm Hg), respectively. Myocardial oxygen tension was not altered significantly by varying the arterial oxygen tension between 65 and 300 mm Hg. However, myocardial carbon dioxide tension increased linearly with increased arterial carbon dioxide tension. In 15 dogs placed on total cardiopulmonary bypass, a perfusion pressure 40-60 mm lower than the control mean arterial pressure resulted in myocardial ischemia with a decrease in myocardial oxygen tension and an increase in myocardial carbon dioxide tension. A subsequent increase in perfusion pressure to control levels resulted in resolution of ischemia and return of myocardial oxygen and carbon dioxide tensions to their control level. In another series of open-chest dogs on cardiopulmonary bypass, a proximal constriction applied to the left coronary circumflex artery resulted in a marked decrease in myocardial oxygen tensions and a marked increase in myocardial carbon dioxide tensions in the region supplied by the constricted vessel. In yet another series of open-chest dogs, it was found that incremental decreases in coronary flow established by constriction of the circumflex artery resulted in an exponential increase in both myocardial carbon dioxide tensions and ST-segment elevation as determined by a 25-gauge multi-contact plunge electrode placed in the posterior left ventricular wall. It appears that mass spectrometry techniques for evaluating myocardial ischemia have several advantages over myocardial biopsy techniques for assay of ATP and lactate, and also over the technique of coronary sinus lactate determination.

Animals↗