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Biomedical subjects

T D Ivey

Publications and source records attributed to T D Ivey.

At least 55 records · Page 3Linked to original sources
PubMed1986

Reperfusion of ischemic dog lung results in fever, leukopenia, and lung edema.

Pulmonary artery obstruction results in minimal parenchymal abnormalities in normal lung and diminishes edema formation in dog lungs injured by oleic acid. We tested the hypothesis that reperfusion of ischemic regions would result in significant injury in normal lung and would ablate the protective effect of ischemia in oleic acid injury. The pulmonary artery of the left diaphragmatic lobe was occluded for 48 h in 12 oleic-acid-injured and 10 normal animals. Observations made immediately before reperfusion and for 4 h after reperfusion in the awake dogs indicated that reperfusion resulted in systemic abnormalities in both groups of animals, including a rise in temperature, a fall in cardiac output, and a marked drop in circulating leukocytes. In uninjured animals, the reperfused lobe demonstrated an elevated wet-to-dry weight ratio of 5.70 +/- 0.13 compared with 4.42 +/- 0.06 for the right diaphragmatic lobe (p less than 0.05). Histologic examination revealed edema and white cell infiltrates in the alveoli of the reperfused lobe in uninjured animals. In injured animals, there was no difference in either wet-to-dry ratios or morphologic aspects between the lobes. The results demonstrate both a local and systemic toxic effect of reperfusion in normal animals and ablation of the partial protective effect of pulmonary artery occlusion in oleic-acid-injured animals.

Animals↗
PubMed1986

Double tachycardia following surgery for recurrent ventricular arrhythmias.

Simultaneous accelerated "junctional" rhythm and atrial flutter were observed postoperatively in a patient who had undergone electrophysiologic surgery for recurrent ventricular fibrillation. Digitalis toxicity was excluded, based on the low serum level of the drug and on the recurrence of the tachycardia after withdrawal of digitalis. While atrial flutter probably represented a postoperative recurrence of a clinically occurring arrhythmia, the accelerated "junctional" rhythm at unusually fast rates most likely developed as a consequence of a cryolesion applied to the ventricular septum as part of the surgical treatment. Phenytoin proved effective in suppressing this "junctional" tachycardia.

Aged↗
PubMed1986

Regional myocardial protection by retrograde coronary sinus infusion of cardioplegic solution.

Antegrade administration of a cardioplegic solution in the presence of a coronary artery stenosis may lead to the heterogeneous distribution of the agent and poor myocardial cooling distal to a vessel stenosis. To determine the effects of retrograde coronary sinus infusion of cardioplegic solution, coronary stenosis was created in the canine preparation by occluding the left circumflex artery (LCx) during cardioplegic arrest. Left ventricular global and regional function (assessed by sonomicrometry and solid-state micrometers) were studied after 60 min of ischemic arrest. Three groups (all n = 7) were studied: group I (control), cardioplegic solution infused via the aortic root without LCx occlusion; group II, same as group I except with LCx occlusion; group III, retrograde coronary sinus infusion of cardioplegic solution with LCx occlusion. Heart rate was controlled by atrial pacing. Statistically significant differences in global function between the three groups were seen at low filling pressures but were not seen during volume challenge. However, the recovery ratio of regional function in the LCx area at a left atrial pressure of 5 mm Hg in group II was 77.2% (% shortening) and 48.5% (segment work), which was significantly less (p less than .01) than recovery in group I (111.7% and 75.9%) and group III (108.3% and 81.5%). These differences persisted during volume loading, to a mean left atrial pressure of 15 mm Hg. Regional compliance in group II was also significantly (p less than .01) depressed after cardioplegic arrest but was well preserved in groups I and III.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Effect of damped sine-wave shocks on catheter dielectric strength.

This study evaluated the ability of 24 new standard tripolar and quadripolar U.S. Catheter Instruments catheters to withstand a single damped sinusoidal shock delivered by a standard defibrillator. The schema for energy delivery was meant to simulate possible clinical practices. Delivered peak voltage and current were measured during each shock. Each electrode was examined for pitting and changes in line resistance as a consequence of the shock. Electrode pitting occurred on all selected anodal poles. However, it also was found on "unsolicited" electrodes from 7 catheters, indicating that current had followed unanticipated routes. Electrode line resistance was unmeasurable in 6 of these 7 inappropriately pitted electrodes. Delivered peak voltage and postshock catheter dielectric strength depended on the manner of energy delivery. To simulate a posterior septal accessory pathway ablation procedure, a shock was delivered to 2 proximal (anodal) poles in 16 quadripolar catheters (8 received 200 J and 8 received 360 J). Delivered peak voltage was 3,125 +/- 362 V for the 200-J shock and 4,100 +/- 160 V for the 360-J shock. Postshock catheter dielectric strength for the 200- and 360-J shock was 1,425 +/- 826 V and 601 +/- 707 V, respectively. This was significantly lower than peak delivered voltage (p less than 0.001 for either energy). To simulate His bundle or ventricular tachycardia focus ablation, 8 tripolar catheters each received a single 200-J shock to the tip electrode. This resulted in a delivered peak voltage of 2,900 +/- 351 V, compared with a postshock dielectric strength of 1,325 +/- 1,320 V (p less than 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Catheterization↗
PubMed1985

Hypoperfusion as a possible factor in the development of gastrointestinal complications after cardiac surgery.

This study has presented the spectrum of postoperative gastrointestinal system complications after open heart surgery at the University of Washington from 1980 through 1983. The frequent necessity for operative intervention and a mortality rate of 17 percent in our study of gastrointestinal complications in patients who have undergone open heart surgery indicates the need for early diagnosis and treatment. The data suggest that bypass times approaching 100 minutes and the presence of postoperative cardiogenic shock are important risk factors in the development of such complications in elective cardiac surgery patients. An incidence of gastrointestinal complications of 8.6 percent in those undergoing repair of acute aortic dissections makes gastrointestinal complaints particularly suspicious in this subgroup.

Adult↗
PubMed1985

Autotransplantation of skeletal muscle into myocardium.

In a series of 15 studies in dogs, sternocleidomastoid muscle was used to replace deficits created in left ventricular myocardium and sternohyoid muscle was used to replace portions of right myocardial wall. The five right ventricular autotransplants resulted in a 100% surgical success rate, with animals electively killed between 3 and 55 weeks after surgery. In 10 left ventricular studies excision of areas varying from 12 X 46 mm to 30 X 60 mm and incisions of from 40 mm to 70 mm in length were performed. Left ventricular studies resulted in a 60% surgical success rate, with clinically healthy animals being killed for study between 2 weeks and 50 weeks after surgery. Animals surviving the critical surgical recovery period showed no loss of weight or changes in activity. Gross findings at autopsy confirmed the viability of the skeletal muscle transplants. Borders were well healed and the grafted tissue was pliable. Histologic studies suggest that revascularization of skeletal muscle occurred from the myocardial side, and that there were healthy myocardial and skeletal muscle fibers at the junction, with evidence of regeneration.

Animals↗
PubMed1985

Catheter-mediated electrical ablation of the posterior septum via the coronary sinus: electrophysiologic and histologic observations in dogs.

In a series of 12 dogs, the electrophysiologic and histologic effects of a single damped sine-wave shock delivered via standard electrocatheters to the region of the coronary sinus orifice were investigated. Six dogs received 200 J and six received 360 J of stored energy. The shock was delivered to two consecutive proximal poles of a standard quadripolar catheter positioned at the coronary sinus orifice and connected to the positive output (anode) of a defibrillator. A disc electrode positioned on the anterior chest wall served as the cathode (negative pole). During the shock, voltage and current were recorded. Electrophysiologic testing was done before and 4 weeks after the shock. At 4 weeks, animals were killed and serial sections of the atrioventricular groove and conduction system were performed. No significant long-term change in atrioventricular conduction, spontaneous or induced atrial or ventricular arrhythmias was observed. However, transient atrioventricular block was seen in five and idioventricular rhythms in six animals in the short term. No persistent electrocardiographic changes were observed, and no sudden deaths occurred. Microscopically, transmural injury at the anulus proper or basilar ventricular epicardium was inconstant and infrequent. However, transmural atrial injury at the level of the coronary sinus was produced over a 10 +/- 5 mm length with the 200 J shock and a 21 +/- 6 mm length with the 360 J shock. Neither coronary artery injury nor damage to the conduction system was seen and cardiac tamponade did not occur. However, localized intramural atrial rupture of the coronary sinus wall (on the endocardial aspect only) was observed in each dog, consistent with barotrauma. With the present technique, atrial injury potentially capable of blocking the effects of accessory pathway conduction could be produced without other electrophysiologic alterations or complications. Injury to the anulus proper (and therefore to any accessory pathway per se) is probably unlikely. Barotrauma may play a significant role in the type of injury observed in this study.

Animals↗
PubMed1985

Oral verapamil for prophylaxis of supraventricular tachycardia after myocardial revascularization. A randomized trial.

To determine if the prophylactic administration of oral verapamil is effective in reducing the incidence of supraventricular tachycardia after myocardial revascularization, 141 patients were entered into a double-blind randomized trial. Seventy patients received verapamil 80 mg every 8 hours beginning immediately after operation and continuing for 5 days, and 71 patients received placebo. Patients were monitored during the study period and observed for the occurrence of supraventricular tachycardia. The verapamil and placebo groups were similar with regard to sex, age, preoperative antianginal drugs, number of bypass grafts, average bypass time, and average occlusion time. A total of 39 patients had supraventricular tachycardia, 20 were receiving verapamil, and 19 were receiving placebo. The average ventricular rate was 127 +/- 13 beats/min for the verapamil group with supraventricular tachycardia compared with 140 +/- 12 beats/min for the placebo group with the mean differences not significant (p = 0.10). On the basis of these data, it is concluded that verapamil 80 mg every 8 hours beginning early after myocardial revascularization is not effective in reducing the incidence of supraventricular tachycardia.

Administration, Oral↗
PubMed1985

Surgical management of refractory ventricular arrhythmias in patients with prior inferior myocardial infarction. A preliminary report.

Most reports of operations for ventricular arrhythmia have dealt with patients with anterior myocardial infarction. Patients with previous remote inferior myocardial infarction and recurrent ventricular tachycardia or fibrillation are a difficult subset of patients to treat with surgical ablative procedures. Over a 2 year period, 11 patients with prior inferior myocardial infarction and drug-refractory ventricular tachycardia or fibrillation underwent elective operation to control the arrhythmia. Five patients had monomorphic ventricular tachycardia. Three of these five patients had localized endocardial resection and/or cryoablative procedures when the ventricular tachycardia was well localized intraoperatively. In the remaining two patients, ventricular tachycardia was noninducible intraoperatively, and the patients underwent extensive endocardial resection and mitral valve replacement because of sites suspected near the posterior papillary muscle from preoperative catheter mapping. None of these five patients had inducible ventricular tachycardia postoperatively, and all are clinically free of the arrhythmia over a 24 month follow-up period. One patient with two morphologies of ventricular tachycardia previously had an unsuccessful blind endocardial resection. She underwent map-directed cryoablation of both sites of ventricular tachycardia. Postoperatively, the patient was free of inducible arrhythmia and has been asymptomatic over 8 months. Five patients had pleomorphic ventricular tachycardia or fibrillation that could not be electrically localized. One patient with ventricular fibrillation underwent extensive endocardial resection, but the posterior papillary muscle was spared. Postoperative electrophysiological study was positive. The patient has had no clinical ventricular arrhythmias on a regimen of amiodarone, however. Two patients had extensive endocardial resection and mitral valve replacement. One died early in the postoperative course and the other is clinically well. The remaining two patients had an encircling endocardial ventriculotomy. Both are clinically stable although one had inducible ventricular fibrillation postoperatively. We conclude that well-defined monomorphic ventricular tachycardia in patients with a previous inferior myocardial infarction can be successfully treated with localized endocardial resection and/or cryoablation. However, patients with poorly localized monomorphic ventricular tachycardia or pleomorphic ventricular tachycardia or fibrillation may require more extensive procedures. The role of posterior papillary muscle sacrifice with mitral valve replacement remains undefined.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1984

Changes in cardiac functional capacity after coronary bypass surgery in relation to adequacy of revascularization.

Seventy patients having aortocoronary vein bypass grafting surgery for angina pectoris underwent preoperative invasive exercise testing to symptom limits and again 6 to 14 months postoperatively. Cardiac output was measured using the direct Fick principle. Postoperatively at maximal exercise, there was a 3.11 liters/min (p less than 0.0001) increase in cardiac output in men (n = 61) and a 2.04 liters/min (p less than 0.01) increase in women (n = 9). Patients with complete revascularization showed a significantly greater improvement in cardiac output postoperatively than did those with incomplete revascularization (26 versus 6%, p less than 0.0001). The major reason for the increased maximal cardiac output was a marked increase in heart rate while stroke volume was maintained at the same preoperative level. These findings were true irrespective of preoperative use of beta-adrenergic blocking drugs.

Adrenergic beta-Antagonists↗
PubMed1984

Improvement in aerobic and hemodynamic responses to exercise following aorta-coronary bypass grafting.

Preoperative and postoperative hemodynamic studies were performed during exercise in 70 patients having aorta-coronary bypass grafting for the treatment of angina. There was significant symptomatic improvement with 88% of patients free of angina postoperatively. In patients with complete revascularization there was a marked improvement during exercise in maximal oxygen consumption, cardiac index, and maximal pressure-rate product. In addition, there was a fall in pulmonary arterial pressure postoperatively. In contrast, patients with incomplete revascularization showed a small but insignificant rise in maximal oxygen consumption and cardiac index. The major reason for the increase in cardiac index was a marked increase in heart rate rather than a change in stroke index. In patients with complete revascularization there was a significant increase in stroke work index at maximal exercise.

Adrenergic beta-Antagonists↗
PubMed1984

The effect of prostacyclin infusion on platelet hemostatic function in patients undergoing cardiopulmonary bypass.

Prostacyclin (PGI2) infusion was studied in patients during cardiopulmonary bypass for coronary artery bypass grafting to assess its capacity to protect platelet hemostatic function. Twelve patients received PGI2 at doses ranging from 20 to 70 ng/kg/min by continuous infusion directly into the bubble oxygenator. Nine control patients were also studied. Platelet counts were not different in the two groups; the platelet count at the completion of the operation was decreased by a mean of 29% in treated patients and 40% in control patients (p greater than 0.15). Bleeding times were uniformly greater than 30 minutes following 30 minutes on bypass in both groups (p greater than 0.5). Also there was no difference in the bleeding times between the treated and untreated groups in the immediate postbypass period (p greater than 0.05). In addition, no difference in transfusion requirements was observed between the treated and control groups. However, plasma levels of platelet factor 4 were lower in the treated patients (p less than 0.05), and, more significantly, blood pressure was lower at all time points in the treated patients (p less than 0.001) despite the greater use of vasopressors. We conclude that PGI2 infusion in this study was of no hemostatic benefit but produced significant hypotension, a potential source of morbidity.

Adult↗
PubMed1984

Management of patients with carotid bruit undergoing cardiopulmonary bypass.

During a 31 month period, 1,433 consecutive patients undergoing cardiac procedures were screened for carotid bruit. A total of 94 patients with carotid bruit were identified who had ultrasonic carotid duplex scans. Nine patients had a history of transient ischemic attack, carotid bruit, and reduction in internal carotid artery diameter by greater than or equal to 50% according to ultrasonic carotid duplex scanning. All nine patients underwent carotid angiography followed by thromboendarterectomy prior to or simultaneous with cardiopulmonary bypass. There was one neurological complication leading to death in this subset. Sixteen patients with asymptomatic carotid bruit had ultrasonic carotid duplex scanning revealing an internal carotid artery lesion of greater than or equal to 50% but did not undergo arteriography or thromboendarterectomy prior to the cardiac procedure. Perfusion pressure was maintained at greater than or equal to 70 mm Hg during bypass. There were no focal neurological events in this subset. Sixty-six patients with internal carotid artery stenosis of less than 50% diameter reduction and asymptomatic bruits had no further work-up or modification in perfusion technique, and there were no focal neurological events in this group. Thus there were no focal neurological events in any of the 82 patients with asymptomatic carotid bruit. An additional group of three patients with a previous stroke and internal carotid artery occlusion by ultrasonic carotid duplex scanning had transient exacerbation of neurological symptoms after cardiopulmonary bypass. The remaining 1,339 patients without carotid bruit had nine (0.7%) focal neurological events postoperatively. We believe that asymptomatic patients with or without hemodynamically significant stenosis can safely undergo cardiopulmonary bypass procedures without carotid thromboendarterectomy. Patients with asymptomatic bruits can be safely screened with ultrasonic carotid duplex scanning and do not require arteriography prior to cardiopulmonary bypass.

Auscultation↗
PubMed1984

The early course of pulmonary artery hypertension in patients undergoing mitral valve replacement with cardioplegic arrest.

In an effort to describe the immediate course of pulmonary hypertension following mitral valve replacement, we reviewed preoperative and postoperative data from 62 patients who underwent mitral valve replacement. Patients were divided based on the absence (Group I) or presence (Group II) of severe preoperative pulmonary hypertension, defined as a mean pulmonary artery pressure greater than or equal to 40 mm Hg. Group II patients were subdivided based on the absence (Group IIa) or presence ( Group IIb) of markedly elevated preoperative pulmonary vascular resistance indices, defined as a greater than or equal to 700 dynes . sec . cm-5 . m2. Pulmonary artery wedge pressures fell promptly following mitral valve replacement in all groups, but the course of other hemodynamic parameters varied among groups. Cardiac index increased significantly among Group I and IIb patients but not among Group IIa patients. Group I patients did not have significant changes in mean pulmonary artery pressure and pulmonary vascular resistance index. Group IIa patients had substantial reductions in mean pulmonary artery pressure while pulmonary vascular resistance index remained near 400 dynes . sec . cm-5 . m2. Group IIb patients had substantial reductions in mean pulmonary artery pressure while pulmonary vascular resistance index fell significantly to about 400 dynes . sec . cm-5 . m2. Primary valvular lesion and pharmacologic support were insignificant variables. Data from these hemodynamic groups suggest that at least three mechanisms contribute to the pulmonary hypertension seen in mitral valve disease: passive transmission of elevated left atrial pressures, reactive pulmonary arteriolar vasoconstriction, and morphologic changes in the pulmonary vasculature. The first two mechanisms appear to be rapidly reversed following mitral valve replacement. While others have described the regression of pulmonary hypertension several months following mitral valve operations, data presented here suggest that changes in pulmonary artery pressures and pulmonary vascular resistance index may occur much earlier.

Adult↗
PubMed1983

Postinfarction angina: results of early revascularization.

To assess the efficacy of surgical revascularization for postinfarction angina within 30 days of acute infarction, the clinical course of 103 patients treated surgically from January 1979 to July 1982 was reviewed. There were 84 men (82%) and 19 women (18%) with a mean age of 58 years (range 34 to 80). Group A (11 patients) underwent surgery within 24 hours of infarction, Group B (21 patients) within 7 days and Group C (71 patients) within 30 days. Eighty-four patients (82%) had subendocardial infarctions and 19 patients (18%) had transmural infarction. Transmural infarction was more common in patients in Group A (36%) than in those in either Group B (19%) or Group C (15%). There were two deaths, both in Group C (1.9%), within 30 days of surgery. The use of intraaortic balloon or inotropic support and the occurrence of major arrhythmias or perioperative infarction was noted in 30 patients (29%) (64% in Group A, 33% in Group B and 18% in Group C). The average time in the intensive care unit was 3.2 days, with an average total hospital stay after surgery of 8.3 days. Late follow-up (mean 15.4 months, range 1 to 39) is complete for 97 patients (97%). There were no late myocardial infarctions and 93 patients (96%) were essentially free of angina. The only late death (1.0%) was caused by septicemia from delayed sternal wound infection. This study suggests that myocardial revascularization within the first 30 days after myocardial infarction can be accomplished with an acceptable operative mortality in selected patients with postinfarction angina refractory to medical management.

Adult↗
PubMed1983

Influence of propranolol on supraventricular tachycardia early after coronary artery revascularization. A randomized trial.

A total of 116 patients undergoing coronary revascularization were randomized preoperatively in a double-blind manner to receive 80 mg daily of propranolol or placebo in the postoperative period. Preoperatively, all patients had been receiving at least 80 mg of propranolol a day to the time of the operation. In addition, all patients had a left ventricular ejection fraction of 0.4 or more, no history of supraventricular tachyarrhythmia (SVT), and no need of digitalis preparations or other antiarrhythmic drugs. All patients were monitored for 5 days and propranolol or placebo was started 24 hours postoperatively. SVT was documented with biatrial electrograms in all cases. Study groups were similar in postoperative creatine kinase MB levels and postoperative weight gain, but the placebo group tended to be older and have more grafts per patient. Seven patients randomized were dropped from the study, two with perioperative infarction, four with persistent ventricular arrhythmias necessitating quinidine or procainamide, and one with persistent postoperative hypotension (placebo). There were no significant differences in the incidence of postoperative SVT in these two groups: 13.2% in the propranolol group and 16.1% in the placebo group. We conclude that 80 mg daily of propranolol given postoperatively to patients undergoing coronary revascularization does not effectively reduce the incidence of SVT.

Clinical Trials as Topic↗