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Biomedical subjects

R S Litwak

Publications and source records attributed to R S Litwak.

At least 37 records · Page 2Linked to original sources
PubMed1980

Coronary artery spasm and perioperative cardiac arrest.

There has been increasing interest in coronary artery spasm as etiopathogenic mechanism for various syndromes associated with myocardial ischemia. A case with documented organic coronary artery disease is presented, in which coronary artery spasm was the probable cause of intraoperative and early postoperative cardiac arrest. We recommend that coronary spasm be considered in the differential diagnosis of perioperative cardiac arrest.

Angina Pectoris, Variant↗
PubMed1978

A simple left heart assist device for use after intracardiac surgery: development, deployment and clinical experience.

A simple left heart assist device (LHAD) has been developed and employed in nineteen patients with severe left ventricular dysfunction who could not be weaned from cardiopulmonary bypass following intracardiac surgery. It has been used when all other means of weaning, including maximum pharmacologic therapy and intra-aortic balloon counterpulsation (IABC), had failed. The device utilizes specially designed and constructed obturated cannulae in the left atrium and the ascending aorta, and an extracorporeal roller pump to partially bypass the left ventricle. With improved cardiac performance, the patient may be separated from the device without need for thoracic reentry. Of the nineteen patients having LHAD support (2-500 hours), thirteen were eventually weaned from the device and seven were discharged from the hospital. Five patients remain alive and well (18 to 50 months postoperatively).

Assisted Circulation↗
PubMed1978

The cerebral function monitor during open-heart surgery.

Open-heart surgery has entered the third decade of its existence. The period has demonstrated increased patient safety during and after open-heart surgery due to the employment of simple and reliable monitoring techniques. The monitoring of the function of the brain has not kept pace with these advances. Electroencephalographic (EEG) method is impractical for routine use in the operating room and in the intensive care unit. The cerebral function monitor (CFM) offers simplified continuous monitoring and interpretation of cerebral electrical activity (integrated EEG) in the clinical situation. The unit displays a two channel tracing, one representing cerebral activity and a second indicating electrode impedance artefacts. The early changes seen in addition to other conventional monitoring of the electrocardiogram, blood pressures, pulse rate, etc. offers information especially pertinent to open-heart surgery. It would appear that there is a place in anesthetic practice during and after cardiopulmonary bypass for the routine use of the CFM to supplement existing monitoring for the safer conduct of open-heart surgery. This study analyzes the value of a cerebral function monitor in 112 patients undergoing open-heart surgery.

Brain↗
PubMed1977

Left ventricle to aorta valved conduit for relief of diffuse left ventricular outflow tract obstruction.

Operative relief of congenital tunnel subaortic stenosis by means of local incision or excision, or both, has generally been unsatisfactory. The use of a valve-bearing conduit between the left ventricular apex and thoracic aorta offers a predictable means of bypassing the left ventricular outflow obstruction. The procedure was used in a 17 year old girl with an excellent hemodynamic result. The history of operative management with diverting plantation of valved conduits in this position have not been defined, but use of these prostheses appears advisable in severe subvalvular, valvular and supravalvular obstructions that are not readily amenable to predictable and safe surgical palliation. The operation may prove useful in selected cases of idiopathic hypertrophic obstructive cardiomyopathy.

Adolescent↗
PubMed1977

Creating permanent complete heart block by indirect cauterization without atriotomy.

We created permanent complete heart block (CHB) in 11 dogs without atriotomy by means of indirect cauterization of the atrioventricular (A-V) bundle with a partially insulated wire placed through a small puncture in the atrial wall and guided by palpation. In six acute studies and five chronic studies, all dogs exhibited permanent CHB. To test the block, isoproterenol increased both atrial and ventricular rates 200%-400% without affecting the block. Atropine had no effect on ventricular rate or block.

Animals↗
PubMed1977

Role of the Hancock "stabilized glutaraldehyde process" bioprosthesis in the management of mitral valve disease.

The low mortality of isolated mitral valve (MV) replacement permits attention to be focused on those valve-related factors which affect the quality of life after operation. Comparison of a number of MV prostheses indicates that all perform satisfactorily from the hemodynamic standpoint. An asset of the "stabilized glutaraldehyde process" (SGP) Hancock bioprosthesis (H-B) is the significantly lower incidence of thromboembolism encountered in patients who have not been permanently anticoagulated. While additional time is required before meaningful durability comparisons can be made, the absence of valve failure and the low incidence of tissue dysfunction in H-B over 6 1/2 years is encouraging. Although the ideal device for replacing the MV is not yet available, the Hancock SGP bioprostheses represent the best compromise of available choices.

Aldehydes↗
PubMed1977

Temporary mechanical support of left ventricular failure following open heart surgery.

Patients coming to open heart surgery with advanced cardiac dysfunction may require mechanical cardiac support to avoid life-threatening low cardiac output in the postoperative period. 15 patients who could not be withdrawn from cardiopulmonary bypass because of low cardiac output were supported with a left heart bypass system (left atrium to ascending aorta). Ten were ultimately separated from the device, 6 were dismissed from the hospital and 4 remain well (the longest 2.6 years postoperative). A major asset of the device is that thoracic reentry is not required when support is discontinued.

Assisted Circulation↗
PubMed1977

Estrogen suppression of surgically induced vascular intimal hyperplasia in rabbits.

Since estrogen has been shown to reduce aortic medial hypertrophy in hypertensive rats, a naturally occurring estrogen compound, estradiol, was studied for its ability to suppress the intimal hyperplasia which follows vessel transection and anastomosis. Suture lines and adjacent abdominal aortas were examined by light and electron microscopy 1 month after surgery, in 23 rabbits. Test animals were given 200 microgram of Depoestradiol I.M. weekly, starting 3 days preoperatively. Control animals were similarly manipulated but received no estrogen. Control animals showed striking intimal thickening over the sutures, in contrast to the estrogen-treated group in which there was significantly less growth of corresponding tissue (p less than 0.01).

Animals↗
PubMed1977

Reduction of unexpected, life-threatening events in postoperative cardiac surgical patients; the role of computerized surveillance.

With increasing use of computerized surveillance (CS) in critical care, a key question is whether it favorably influences clinical outcome. Knowing that two intensive care unit beds would soon have CS capability, we embarked on an uninterrupted prospective study in which the incidence of sudden, unexpected life-threatening events (SULTE) was compared in post-open heart surgery patients whose subsystem performances were evaluated by conventional methods (CM) as opposed to those who would be followed by CS involving automatic acquisition and generation of 30 cardio-respiratory variables. We evaluated 211 patients, 91 with CM and 120 by CS. Since CS availability was limited, sicker patients were given priority for the two CS beds. Despite the obvious bias in favor of CM, there was a statistically significant reduction (P less than 0.001) in the incidence of SULTE in those patients followed by CS (1 of 120 patients: 0.8%; no SULTE-related deaths) in comparison to the CM patients (11 of 91 patients: 12%; two SULTE-related deaths.) The data suggest that computerized surveillance can play a role in reducing morbidity and possibly mortality in postoperative cardiac surgical patients.

Adult↗
PubMed1976

Use of a left heart assist device after intracardiac surgery: technique and clinical experience.

A left heart assist device (LHAD) has been employed in 14 patients. All had advanced heart disease and were in low cardiac output after repair, such that they could not be separated from cardiopulmonary bypass despite prolonged support and adjuvant therapy, including drugs, pacing, and use of intraaortic balloon counterpulsation whenever possible. Apart from special cannulas, the equipment necessary for the LHAD is widely available. An asset of the system (left atrial-ascending aorta bypass of the left ventricle) is that it may be terminated without reentering the thorax to remove the cannulas. This is accomplished with precisely fitting obturators that obliterate the cannula lumens and allow the tubes to be permanently implanted. This concept is believed important since critically ill patients requiring support are precisely those in whom added risk would be imposed by a second operation. Of the 14 patients who have had intraoperative and postoperative support (up to 6.8 days), 9 were weaned from the device and 6 were dismissed from the hospital. Four patients remain alive and are improved, the longest at 22 months since operation. The favorable performance of the LHAD suggests that it may prove useful either when intraaortic balloon counterpulsation cannot be successfully deployed or when it has failed to achieve hemodynamic stability.

Assisted Circulation↗
PubMed1976

Electrophysiological and antiarrhythmic effects of propranolol in canine acute myocardial ischemia.

To correlate the antiarrhythmic and electrophysiological effects of propranolol in acute myocardial ischemia, we examined the effects of temporary (15-minute) ligations of the left anterior descending coronary artery in studies on 15 dogs. We recorded bipolar electrograms and monophasic action potentials from the ischemic and normal zones and measured the intervals from the onset of QRS in a standard electrocardiogram lead to the major deflection of electrograms recorded from the ischemic and normal zones. We also determined monophasic action potential duration (APD) and effective refractory period (ERP). Data for control ligations were compared to those during which propranolol, 40 mug/kg, was administered intravenously immediately after ligation. Propranolol reduced the mean number of ventricular beats per minute (from 15 to 6) (P less than 0.01). Propranolol slowed conduction in the ischemic zone (by 10 msec at peak effect, P less than 0.01) and had no or only a very slight effect (by 1-msec at 15 minutes, P less than 0.05) on conduction in the normal zone. Propranolol also prolonged APD in the ischemic (32-msec) and normal (14-msec) zones (P less than 0.01), prolonged ERP in the ischemic (41-msec) and normal (20-msec) zones (P less than 0.01), and reduced the APD/ERP ratio in the ischemic (1.62 to 1.47) (P less than 0.01) and normal (1.62 to 1.55) (P less than 0.05) zones. During the control ligation, APD in the ischemic zone was 25 msec shorter than in the normal zone (P less than 0.01), but with propranolol the difference was not significant. The effects of propranolol in slowing conduction in the ischemic zone, in prolonging refractoriness, in reducing APD/ERP, and in reducing the disparity in APD between ischemic and normal zones may explain its demonstrated antiarrhythmic effects in acute myocardial ischemia.

Action Potentials↗
PubMed1976

Postcardiotomy low cardiac output clinical experience with a left heart assist device.

Fifteen patients with advanced heart disease who could not be withdrawn from cardiopulmonary bypass (CPBP) because of low cardiac output were supported with a left heart assist device (LHAD). The system (left atrium to ascending aorta bypass of left ventricle) was not employed until all other measures had failed to allow separation from CPBP, including intraaortic balloon counterpulsation whenever possible. In this experience no attempt was made to totally bypass the left ventricle (LV). Rather, LHAD flow rate was adjusted so that the combined output of the LHAD and depressed LV achieved satisfactory levels of systemic blood flow at acceptable LV filling pressures. With improved cardiac performance patients were separated from the LHAD without need for thoracic reentry. Of the 15 patients having LHAD support (longest 21 days), 10 could be separated from the device and six were dismissed from the hospital. Four remain well, the longest 1.6 years postoperatively. Patients requiring 3 days or less of circulatory assistance had a more favorable prognosis than those needing more extended periods of support.

Adult↗
PubMed1975

Extracorporeal model for study of factors affecting thrombus formation.

Factors determining thrombus formation on a foreign surface were studied with the use of plastic flow chambers introduced into extracorporeal shunts. Silicone rubber shunts, joining the carotid artery and jugular vein, were implanted in dogs and remained patent for several weeks. The flow chamber geometry consisted of a 4.8 mm diameter straight tube having a 3.2 X 3.2 mm circumferential cavity in the wall. Chambers were introduced sequentially into the shunts for exposure times of 10 to 30 minutes and regulated blood flow rates of 100 to 400 ml/min. The dry weight of thrombus accumulated in the chamber (5 to 50 mg) was found to increase with exposure time up to 20 minutes and to decrease with increasing flow rate. Various components of the process of thrombus formation were altered by the administration of acetylsalicylic acid, heparin and lysozyme, used alone and in pairs. Heparin was found to be the most effective antithrombotic agent, dry weights of accumulated thrombus being on the order of 50 percent lower when compared to control values. The efficacy of heparin was found to be unaffected by the presence of aspirin and lysozyme, which themselves were not effective antithrombotic agents under the conditions of these experiments. The technique described here may provide a useful animal model for studying the influence of blood flow and different biomaterials on thrombus formation.

Animals↗
PubMed1975

Early clinical experiences with a heart assist device.

A method of left heart (left atrium-aorta) support after open heart surgery is described. Thoracic reentry is not required when support is terminated. The system has been employed in 10 patients, 4 of whom are long-term survivors.

Adult↗
PubMed1975

The use of vein allografts as sidearms for intraaortic balloon insertion.

Femoral artery cannulation for intraaortic balloon counterpulsation may be attended by difficulties due to changes in the vessel wall and the inherent stiffness of Dacron grafts. A substitute technique utilizing venous allografts is described. The advantages are enumerated and are related to allograft pliability. Fifty-nine such procedures have been done without related complications.

Assisted Circulation↗