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Biomedical subjects

T J Gardner

Publications and source records attributed to T J Gardner.

At least 145 records · Page 8Linked to original sources
PubMed1981

Clinical and hemodynamic evaluation of the 19 mm Björk-Shiley aortic valve prosthesis.

Between November, 1973, and March, 1980, 43 patients underwent isolated aortic valve replacement with 19 mm Björk-Shiley prostheses at the Johns Hopkins Hospital. There were 4 male and 39 female patients ranging from 12 to 75 years old (mean, 54.5 years). Average weight was 62 +/- 2 kg and average body surface area, 1.64 +/- 0.3 m2. Five patients died within thirty days of operation; however, since 1975, hospital mortality has been 5.9%. The 38 survivors have been followed up for as long as 85 months (mean, 40 months). There were 4 late deaths, and actuarial survival in patients discharged from the hospital was 81% at five years. All long-term survivors were in New York Heart Association Functional Class I (29 patients) or Class II (5 patients). Preoperative and postoperative echocardiograms in 17 patients demonstrated significant decreases in mean left ventricular wall thickness (12.9 +/- 1.8 mm vs 10.3 +/- 1.4 mm; p less than 0.001) and in left ventricular mass (262 +/- 95 gm vs 188 +/- 50 gm; p less than 0.02). Postoperative cardiac catheterization data were obtained from an additional 24 patients undergoing aortic valve replacement with the 19 mm Björk-Shiley prosthesis at the National Heart Institute. Average peak systolic gradient at rest was 16 mm Hg (range, 0 to 45 mm Hg) and was found to be directly related to body surface area (r = 0.60, p less than 0.002). Average effective valve orifice area was 1.06 cm2 (range, 0.63 to 2.02 cm2). For patients with small aortic roots, aortic valve replacement with the 19 mm Björk-Shiley valve is a satisfactory and, perhaps, preferable alternative to aortic annuloplasty to accommodate larger sized prostheses.

Actuarial Analysis↗
PubMed1981

The harmful effects of ventricular distention during postischemic reperfusion.

To assess the effects of left ventricular distention during the early reperfusion period following ischemic arrest, 16 canine heart preparations were subjected to 45 minutes of hypothermic (27 degree C) cardioplegic arrest and normothermic reperfusion. Isovolumic left ventricular developed pressure and rate of rise of left ventricular pressure (dp/dt) were measured with an intraventricular balloon; endocardial/epicardial flow ratios were determined with microspheres; and myocardial gas tensions were monitored with mass spectrometry. During early reperfusion, Group 1 hearts (n = 8) were not distended (end-diastolic pressure = 0). Group 2 hearts (n = 8) were subjected to an enddiastolic pressure of 20 mm Hg for the initial 15 minutes of reperfusion. Group 2 hearts demonstrated impaired subendocardial blood flow after 5 minutes of reflow (0.75 +/- 0.06 vs 0.96 +/- 0.04, endocardial/epicardial flow rates, Group 2 vs Group 1) and persistent elevation of intramyocardial carbon dioxide (CO2) tension (68 +/- 4 vs 51 +/- 4 mm Hg, Group 2 vs Group 1). In addition, postischemic ventricular function was significantly worse in Group 2 hearts (60 +/- 7 vs 79 +/- 3% of control dP/dt, Group 2 vs Group 1, and 53 +/- 6 vs 81 +/- 5% of control left ventricular developed pressure, Group 2 vs Group 1). These data demonstrate that even mild distention during early reperfusion can result in reduced subendocardial perfusion and delayed washout of tissue CO2. Although myocardial blood flow and CO2 tension subsequently returned to normal in the distended hearts, left ventricular performance remained significantly depressed. This injury can occur clinically in nonvented hearts prior to the resumption of effective ventricular contraction.

Animals↗
PubMed1981

Reversal of experimental pulmonary hypertension with sodium nitroprusside.

Pulmonary vascular resistance may be elevated by the use of vasoconstrictive agents or by alveolar hypoxia. The present study was designed to determine the precise vasoconstrictive effects of the two inotropic agents, dopamine and epinephrine, as well as the effects of alveolar hypoxia on the pulmonary vascular system. In addition, the vasoactive effects of a known vasodilator, nitroprusside, were studied. A canine pulmonary lobar preparation was isolated in situ with its pulmonary artery and bronchus selectively cannulated in order to maintain a constant lobar pulmonary blood flow and in order to vary the inspired oxygen concentration from 95% to 0%. Pulmonary vascular pressures were determined by direct measurements and pulmonary vascular resistance units (PVRU) were calculated. Dopamine, epinephrine, and nitroprusside were infused into the isolated pulmonary artery singly and in combination, and the inspired oxygen concentration was varied during each drug infusion. The results of the study demonstrate that dopamine, epinephrine, and alveolar hypoxia all significantly elevate pulmonary vascular resistance. When these two drugs are used together in the presence of hypoxia, the effect on pulmonary resistance is additive. Furthermore, nitroprusside prevents the elevation of pulmonary vascular resistance caused by alveolar hypoxia, and when used with dopamine or epinephrine in the presence of hypoxia, nitroprusside reduces pulmonary vascular resistance toward normal.

Animals↗
PubMed1981

Superiority of perfluorocarbon cardioplegia over blood or crystalloid cardioplegia.

Oxygenated Fluosol-43 cardioplegia (CP), a perfluorocarbon with high oxygen solubility, was compared with crystalloid and oxygenated blood cardioplegia. Potassium in each CP was 25 mEq/l. Thirty perfused rabbit hearts in three groups of 10 hearts each underwent 100 minutes of global ischemia at 20 degrees C, followed by 45 minutes of reperfusion at 37 degrees C. During ischemia, CP was given every 20 minutes. With each CP injection, increases in myocardial oxygen tension were recorded using mass spectrometry and oxygen consumption (MVO2) was calculated. Left ventricular function was assessed before and after ischemia by measuring isovolumic developed pressure and dP/dt with an intraventricular balloon. Intramyocardial PO2 increased by 19.6 +/- 1.8 mm Hg in the Fluosol CP group, 0.4 +/- 0.1 mm Hg in the crystalloid CP group and 1.5 +/- 0.3 mm Hg in the blood CP group (p less than 0.001, Fluosol CP vs crystalloid CP and blood CP). MVO2 with each CP injection, expressed as ml O2/100 g dry weight, was 203.8 +/- 7.0 for Fluosol CP, 20.4 +/- 1.2 for crystalloid CP and 39.2 +/- 4.3 for blood CP (p less than 0.001 Fluosol CP vs crystalloid CP and blood CP). Recovery of maximal dP/dt after 45 minutes of reperfusion, expressed as a percentage of preischemic control, was 75.6 +/- 4.0% for Fluosol CP, 60.9 +/- 5.5% for crystalloid CP and 53.4 +/- 3.7% for blood CP (p less than 0.02 Fluosol CP vs blood CP and crystalloid CP). These data clearly show that the use of Fluosol cardioplegic solution enhanced oxygen delivery and use compared with blood and crystalloid cardioplegic solutions. The marked increase in intramyocardial oxygen and MVO2 with each injection of Fluosol CP shows that there is effective aerobic metabolic activity during ischemia, which may explain the improved functional recovery. The failure of blood CP to afford similar protection can be explained by a decreased oxygen release from hemoglobin due to the leftward shift of the oxygen-hemoglobin dissociation curve with hypothermia.

Animals↗
PubMed1981

Beneficial effects of adding propranolol to multidose potassium cardioplegia.

The use of propranolol with multidose potassium cardioplegia was studied in 32 in situ canine hearts subjected to 90 minutes of global ischemia at 15 degrees C and 60 minutes of reperfusion at 37 degrees C. All hearts received potassium (37 mEq/l) every 30 minutes during ischemia. There were four groups of equal size: group 1 received no propranolol, group 2 received low-dose propranolol and group 3 received high-dose propranolol. Group 4 received high-dose propranolol only with the initial potassium infusion. Myocardial CO2 (PmCO2) was monitored by mass spectrometry as an indicator of metabolic activity. An intraventricular balloon was used to measure isovolumic developed pressure, maximal dP/dt and end-diastolic pressure (EDP) before and after ischemia. During ischemia, peak PmCO2 was significantly higher in group 1 (45.6 +/- 2.8 mm Hg) than in groups 2, 3 and 4 (35.2 +/- 2.8 mm Hg, 33.4 +/- 2.8 mm Hg and 30.4 +/0 2.8 mm Hg, respectively) (p less than 0.05). There were no differences between the four groups in systolic ventricular function assessed by developed pressure and dP/dt. Hearts that received high-dose propranolol had significantly lower EDP after 60 minutes of reperfusion (group 3 13.3 +/- 1.5 mm Hg, group 4 10.4 +/0 1.5 mm Hg) compared with group 1 hearts (25.3 +/- 3.8 mm Hg, p less than 0.05). Hearts in groups 3 and 4 exhibited less ischemic injury as assessed by electron microscopy than hearts in groups 1 and 2. These data show that propranolol added to multidose potassium cardioplegia reduced metabolic activity during ischemia and improved ventricular compliance during reperfusion without depressing systolic function. Because left ventricular compliance and morphologic preservation were similar in groups 3 and 4, it appears that a single high dose of propranolol is sufficient and that subsequent doses do not further enhance the beneficial effects.

Animals↗
PubMed1981

Prostaglandin E1 as an adjunct to emergency cardiac operation in neonates.

Prostaglandin E1 (PGE1) has been used prior to operation in 28 neonates (0 to 30 days) with congenital heart disease (CHD). The patients were divided into two groups. Group I consisted of 19 neonates with CHD resulting in marked cyanosis. Thirteen patients had pulmonary atresia, three had tetralogy of Fallot, and three had complex defects with pulmonary stenosis. All patients were markedly hypoxemic. The average oxygen saturation was 41%. PGE1 infusion, 0.1 mcg/kg/min, was successful in 17 of 19 patients, as it resulted in an increase in oxygen saturation from 41% to 79%, average increase 38%. Two patients did not respond to PGE1 infusion. One was 30 days of age and the other had no patient ductus arteriosus. All of the patients underwent a palliative shunt procedure. There were three hospital deaths in this group. No patient died of hypoxemia. Group II consisted of nine patients whose CHD was predominantly that of aortic obstructive disease with clinical manifestations of cardiac failure, hypoperfusion, and acidemia. Six of these patients had complicated coarctation of the aorta. Three patients had interruption of the aortic arch. The pH of these patients averaged 7.19. PGE1 infusion resulted in improvement of the pH to average of 7.37, improvement of congestive heart failure, and reappearance of femoral pulses. One patient failed to respond. All patients in Group II underwent operation. There were three hospital deaths in this group. No patient died intraoperatively. PGE1 infusion is a valuable aid to surgical treatment of desperately ill neonates with both cyanotic and acyanotic forms of CHD.

Heart Defects, Congenital↗
PubMed1980

Management of aortic arch interruption with prostaglandin E1 infusion and microporous expanded polytetrafluoroethylene grafts.

Prostaglandin E1 infusion and a microporous expanded polytetrafluoroethylene graft were used in the management of eight infants, all less than 4 days old, with interruption of the aortic arch. Five of the six infants receiving prostaglandin E1 responded dramatically to this therapy, with return of lower limb pulses and lessening of metabolic acidosis. There were no adverse effects attributable to the prostaglandin E1 infusion. Seven infants subsequently underwent aortic reconstruction with a polytetrafluoroethylene graft. There were no operative deaths, and in up to 3 years of follow-up of these patients, graft obstruction occurred in only one patient and this graft was successfully revised. The long-term mortality rate was high (62 percent); all deaths but one were attributable either to the palliation or to the total correction of the associated cardiac malformations.

Aorta, Thoracic↗
PubMed1980

Systemic-Pulmonary shunts inneonates and infants using microporous expanded polytetrafluoroethylene: immediate and late results.

Thirty infants with various types of cyanotic congenitl heart disease underwent systemic-pulmonary artery shunts with a microporous polytetrafluoroethylene (PTFE) graft between May, 1976, and July, 1979. Sixteen of them were less than 1 month old, and the average age of the neonates was 5.3 days. There were no operative deaths and 5 hospital deaths, 2 related directly to the shunt. Five patients required early revision of the shunt. Relief from cyanosis was achieved in each patient. Twenty-five patients have been followed up to three and one-half years. There have been 2 late deaths and one late occlusion of the shunt. One patient outgrew the shunt and required secondary shunting procedures. Three of 30 patients have evidenced mild congestive heart failure, which has responded to digitalis. Because of the reliability and excellent late patency of the PTFE prosthesis, we consider it to be superior to a central or Potts shunt for relief from cyanosis in the neonate and infant, and as reliable as a Blalock-Taussig shunt.

Arteriovenous Shunt, Surgical↗
PubMed1980

Unstable angina pectoris. Factors influencing operative risk.

Experience was reviewed with 471 consecutive patients who had coronary artery bypass (CAB) operation alone. The hospital mortality rate was 2% in 341 patients operated on for treatment of stable angina pectoris. There were ten deaths (7.7%) in the 130 patients who underwent CAB for treatment of unstable angina. In this series, age greater than 70 years, poor left ventricular function, distal coronary arteries unfavorable for grafting and the presence of main left coronary artery disease were factors associated with increased operative mortality. In 78 patients with unstable angina who had none of these increased risk factors, the mortality rate was 1.3%. Hospital mortality was 33% in patients older than 70 years and 29% in patients with poor left ventricular function and/or distal vessels unfavorable for grafting. In 23 of the 130 patients, the only increased risk factor present was severe stenosis of the main left coronary artery and one of them (4.3%) died. Thus, when elderly patients and patients with poor left ventricular function or poor distal vessels were excluded, the hospital mortality rate associated with CAB in patients with unstable angina was low (2.0%, 2/101 patients) and equal to that for operation in patients with stable angina pectoris.

Adult↗
PubMed1980

Effect of multiple-dose potassium cardioplegia on myocardial ischemia, return of ventricular function, and ultrastructural preservation.

To evaluate the myocardial protection afforded by multiple-dose versus single-dose administration of potassium cardioplegic solution, we studied 24 isolated feline hearts before, during, and after 1 hour of ischemic arrest. Intramyocardial gas tensions, ventricular function, histologic preservation, and postischemic myocardial edema were compared in hearts maintained at 27 degrees C during the ischemic period. Equal groups of hearts received no infusion of cardioplegic solution, a single dose of potassium solution at the onset of ischemia, or multiple infusions of the cardioplegic solution throughout the arrest period. During ischemia, single-dose cardioplegic administration resulted in less accumulation of myocardial carbon dioxide (Pmco2) than did hypothermia alone, reflecting a reduction in metabolic activity during ischemia. The fact that multiple-dose cardioplegia further reduced Pmco2 accumulation suggests an intermittent washout of metabolic end products. During reperfusion, hearts protected by multidose cardioplegia demonstrated superior preservation of ventricular performance compared to hearts protected by single-dose cardioplegia or hypothermia alone. In addition, multiple infusions of the cardioplegic solution resulted in optimal structural preservation in both light and electron microscope studies.

Animals↗
PubMed1980

Comparison of the effects of left ventricular distention during cardioplegic-induced ischemic arrest and ventricular fibrillation.

To evaluate the role of left ventricular distention in the pathophysiology of myocardial injury during cardiac surgery, 40 isolated, perfused feline hearts were subjected to 1 hour of either hypothermic potassium arrest (groups 1, 2 and 3) or 1 hour of hypothermic ventricular fibrilation (groups 4 and 5). During this period, intracavitary left ventricular pressure was maintained at 0 mm Hg in groups 1 and 4, at 30 mm Hg in groups 2 and 5 and 45 mm Hg in group 3. After either reperfusion of defibrillation, myocardial gas tensions, left ventricular function, coronary blood flow, the ration of endocardial to epicardial blood flow, and myocardial water content were measured to evaluate the degree of myocardial injury incurred. In addition, structural changes in the myocardium were assessed using light and electron microscopy. No differences in these parameters were seen in hearts that underwent ischemic arrest, regardless of the presence or absence of significant left ventricular distention. In fibrillating hearts, however, dilatation decreased ventricular performance, impaired subendocaridal blood flow and elevated myocardial CO2 tensions. These results suggest that left ventricular distention per se is not harmful during periods of ischemia. During periods of ventricular fibrillation, howevr, distention produces impaired subendocardial blood flow, resulting increased ischemia and decreased recovery of ventricular performance.

Animals↗
PubMed1979

Routine use of autotransfusion following cardiac surgery: experience in 700 patients.

An autotransfusion technique has been developed for collection and reinfusion of shed mediastinal blood. This system has been routinely applied in the postoperative management of 592 consecutive adult and 108 pediatric cardiac surgical patients. Two hundred seventy-one adult patients (46%) and thirty-six pediatric patients (33%) actually received autologous blood. Autotransfusion volume ranged from 50 to 21,350 ml per patient. In 1976 at our institution, homologous transfusion requirements averaged 8.4 +/- 0.7 units per adult patient. During 1978, with the routine use of postoperative autotransfusion, bank blood transfusions were lowered to 4.2 +/- 0.3 units per patient (p less than 0.001). In contrast to perioperative autotransfusion techniques, collection and reinfusion of shed mediastinal blood is particularly useful for intravascular volume replacement in patients with serious postoperative bleeding.

Adult↗
PubMed1979

Current management of atrial myxoma with emphasis on a new diagnostic technique.

Sixteen patients aged 22-64 years have undergone removal of atrial myxoma at the Johns Hopkins Hospital. The first two patients had myxomas removed by closed surgical approach, and both died. Fourteen consecutive patients have undergone operation with the aid of cardiopulmonary bypass, and all survived. There has been one late death unrelated to myxoma. Current surgical approach is excision of the tumor and its stalk or base and resection of the portion of intra-atrial septum to ensure complete removal. Recently a new diagnostic technique of two-dimensional phased array real time echocardiography has been used in four patients, including a pregnant woman, to confirm the clinical diagnosis of atrial myxoma. This technique provides a two-dimensional view of both atria and ventricles in cross section or sagittal view. This noninvasive method is painless, is independent of cardiac function and carries no risk or radiation hazard. The two-dimensional echocardiogram is superior to the standard one-dimensional or M-mode echocardiogram for diagnosis of myxoma in that it can evaluate simultaneously both right and left atria, can detect smaller space-occupying lesions because of better resolution and can more readily determine the size of the lesion and its stalk, can evaluate the mobility of the tumor and can determine more accurately the extent of tumor obstruction. Because of these qualities, we have relied on two-dimensional echocardiography as the definitive diagnostic procedure for detection of atrial myxoma. Currently operation for atrial myxoma is performed without cardiac catheterization or angiocardiography.

Adult↗
PubMed1979

Beneficial effects of pulsatile perfusion in the hypertrophied ventricle during ventricular fibrillation.

To assess the potential benefit of pulsatile perfusion inthe hypertrophied heart during fibrillation, 10 dogs with left ventricular hypertrophy, produced by previous supravalvular aortic banding, were used to compare linear and pulsatile perfusion in the fibrillating heart during total cardiopulmonary bypass. The mass spectrometer was used to measure subendocardial PCO2 and PO2 (PmCO2 and PmO2), and radioactive microspheres were utilized to measure myocardial blood flow in the same layers. Pulsatile perfusion was established using the recently develop "bubble tubing," which produces a pulse pressure of at least 20 mm Hg and can be used in a standard roller-pump apparatus. Both linear and pulsatile flows were compared at mean aortic root pressures of 80 and 50 mm Hg, and these four combinations of aortic root pressure and type of flow were employed for periods of 30 minutes each. Myocardial ischemia developed during linear coronary perfusion at 50 mm Hg, as evidenced by an elevation of PmCO2. Ischemia was not evident during pulsatile perfusion at the same mean pressure. Reversal ischemia was a result of increased myocardial blood flow and pulsatile perfusion, and this increase was shown to occur maximally in the deeper subendocardial layer. Ischemia was not eviden during linear or pulsatile perfusion at an mean perfusion pressure 80 mm Hg. Thus, if lower perfusion pressures are to be tolerated in patients with left ventricular hypertrophy, pulsatile perfusion with the bubble tubing technique may prevent the development of subendocardial ischemia or infarction.

Animals↗