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Biomedical subjects

L I Bonchek

Publications and source records attributed to L I Bonchek.

At least 37 records · Page 2Linked to original sources
PubMed1990

Coronary bypass with substrate-enhanced cardioplegia versus non-cardioplegic technique for early revascularization in acute infarction.

Nine patients chosen at random received substrate enhanced cardioplegia (SECP) for early (less than 4 h) revascularization in acute infarction. A control group of 9 patients with similar clinical characteristics was chosen from the larger group revascularized concurrently with a noncardioplegic technique (NCP). There were no significant differences between the NCP and SECP groups respectively in preoperative clinical parameters such as age (62.8 vs. 62.3 years), sex (7 men, 2 women in both groups), ejection fraction (50% vs. 56%) or number of diseased vessels (2.1 vs 2.3). Intraoperative aortic clamp times were significantly shorter in NCP patients (11 vs. 38 min), and 4 NCP patients had no clamping. The internal mammary artery (IMA) was used in 6 NCP patients and 1 SECP patient (to a nonoccluded branch vessel). Postoperatively, NCP patients had higher peak CPK-MB (284 vs. 190 IU/l), longer use of inotropes (10 vs. 2.7 h) and intraaortic balloon pump (15 vs. 8 h), and a higher ejection fraction before discharge from hospital, but none of these differences were significant. SECP appears to provide better myocardial performance early postoperatively, but lasting benefits were not apparent in this subset of patients with early revascularization. Because the IMA has a powerful effect on long term survival but is very difficult to use with antegrade SECP, we continue to favor the IMA without SECP in hemodynamically stable, young patients (less than 65 years) who are revascularized early after infarction.

Aged↗
PubMed1989

Operative factors, not hemodynamics, modify hormones in repair of coarctation.

This study was designed to evaluate separately the influence of restoration of distal pulse pressure and the influence of factors related to operation upon hemodynamic and hormonal alterations accompanying repair of canine aortic coarctation. Eight normal adult dogs underwent a sham operation and served as controls. In 10 dogs the thoracic aorta was transfected and reanastomosed. In 10 dogs aortic coarctation was created within 1 week of birth by banding the aorta just proximal to the ductus ligament, thereby fixing lumenal diameter at 1 to 2 mm. Studies were performed in the latter animals 18 months after operation. These dogs were subdivided into two groups: one (n = 6) underwent surgical repair of the coarctation; in the other (n = 4), the coarctation was repaired and an occluder was placed on the aorta to maintain distal aortic pulse pressure at its diminished preoperative level. Normal distal pulse pressure was restored in these animals by releasing the occluder 1 week after recovery from the repair of coarctation. Each dog was studied in the conscious state before the definitive procedure and again 24 hr later. Plasma renin activity increased significantly after operation in the sham and in the transection groups. Renin activity and proximal blood pressure were significantly elevated and distal pulse pressure was diminished preoperatively in both the repair and the occluder groups. After their respective definitive procedures, the elevation in renin activity and in proximal pressure persisted in the repair group but decreased in the occluder group.(ABSTRACT TRUNCATED AT 250 WORDS)

Anastomosis, Surgical↗
PubMed1988

Postoperative fibrous cardiac constriction.

Two patients with postoperative fibrous cardiac constriction are described. Unlike postoperative pericardial or epicardial constriction, the fibrous constricting layer in these patients envelopes the vein bypass grafts and is separate from the pericardium, which is not involved. Surgical management of these patients is difficult and hazardous; a strategy is outlined.

Cardiomyopathies↗
PubMed1988

Left thoracotomy for reoperative coronary bypass.

The left thoracotomy approach for reoperative circumflex coronary revascularization is described in three cases. This approach is an excellent alternative to repeat sternotomy in select patients.

Aged↗
PubMed1987

Hemodynamic and hormonal abnormalities in canine aortic coarctation at rest and during exercise.

This study was designed to determine the hemodynamic and hormonal consequences of aortic coarctation at rest and during treadmill exercise. Twelve normal adult dogs served as controls. In eight dogs coarctation was created within 1 week of birth by banding the aorta just proximal to the ductus ligament, thereby fixing luminal diameter at 1 to 2 mm. Studies were performed 18 months after operation. Vascular pressures were monitored proximal and distal to the coarctation, cardiac output and regional blood flow were evaluated with radioactive microspheres and blood samples were collected for determination of hormone levels and blood gases. At rest, systolic pressure in the proximal aorta was 130 +/- 12 mm Hg (mean +/- SD) in the control group and 167 +/- 16 mm Hg in dogs with coarctation (p less than 0.01). During exercise at a level that doubled heart rate and cardiac index, mean aortic pressure increased by 11 and 31% (p less than 0.01) in the control and the coarctation group, respectively. Mean distal aortic pressure increased by 8% during exercise in control dogs but decreased by 29% in dogs with coarctation. Exercise decreased flow to the kidneys and the large intestine in the coarctation group. Plasma norepinephrine concentrations were greater in the coarctation group than in control dogs at rest; during exercise, plasma norepinephrine, epinephrine and renin activity increased in both groups, but to a greater degree in the group with coarctation. These results confirm an abnormality in renal and gut perfusion in experimental coarctation and suggest that this may be related to a decline in perfusion pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Coronary artery bypass without cardioplegia.

Cardioplegic myocardial protection has become the standard for coronary artery bypass. In contrast, we report 500 consecutive coronary artery bypass operations with intermittent aortic clamping for distal anastomoses, left ventricular venting, and 30 degrees C hypothermia. Average patient age was 62 years (range of 30 to 89 years). The number of patients who had urgent or emergency operations was 194 (39%); 251 patients had unstable angina, and 123 others had preinfarction angina (pain at rest in the hospital); 27 had evolving myocardial infarction. The average number of grafts was 3.3 per patient, and the average ischemic time was 7.65 minutes per graft. There were five hospital deaths (1%); none resulted from poor myocardial protection that caused low cardiac output. Only three survivors (0.6%) required a balloon pump to be weaned from cardiopulmonary bypass: two had acute infarctions preoperatively, and the other had an ejection fraction of 0.30 and intractable atrial arrhythmias. Only two other patients (0.4%) received any inotropic infusions postoperatively. Eighteen patients (3.6%) had a perioperative infarction. These results, particularly the virtual absence of postoperative inotropic support, in unselected patients of whom 80% had acute coronary syndromes, indicate that intermittent ischemia can provide excellent myocardial protection for coronary bypass. Brief periods of intermittent ischemia alleviate concern about cardioplegic protection via occluded coronaries or internal mammary grafts and provide a simple and safe option for myocardial protection during coronary artery bypass.

Adult↗
PubMed1987

Accuracy of sizers for aortic valve prostheses.

Accurate sizing of the aortic anulus is a prerequisite of prosthetic valve implantation, because it is usually desirable to insert the largest possible prosthesis. Although it is generally assumed that commercial valve sizers are accurately labeled, our measurements reveal that the sizers for the St. Jude Medical, Björk-Shiley, and Ionescu-Shiley prostheses are larger than their nominal sizes. These findings are relevant to the selection of prosthetic valves.

Aortic Valve↗