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Biomedical subjects

S Iversen

Publications and source records attributed to S Iversen.

At least 55 records · Page 3Linked to original sources
PubMed1991

Evaluation of the healing of precoated vascular dacron prostheses.

Knitted and woven Dacron grafts commercially coated with bovine collagen, gelatin and human albumin were implanted end-to-side between the infrarenal aorta and the bifurcation in 35 growing pigs. Grafts were explanted after 4, 8 and 12 weeks and compared to 6 uncoated knitted prostheses preclotted with blood that served as a control. Uncoated grafts rapidly developed a firmly attached neointima lined with endothelium. Compared with coated grafts the thrombus-free area of uncoated grafts was significantly larger (P less than 0.05). The slow resorption of albumin resulted in a delayed and incomplete neointimal healing and failing graft incorporation. Although the bovine collagen was only minimally cross-linked by formaldehyde, healing of the neointima was compromised in a thin woven graft that demonstrated peeling of the inner capsule even after 12 weeks. The identical collagen as well as bovine gelatin were quickly degraded in knitted grafts and both types showed transprosthetic infiltration at 4 weeks. All knitted grafts coated with either collagen or gelatin, however, were occluded after 8 and 12 weeks. Light microscopy revealed hyperplasia of smooth-muscle cells within the thickened distal anastomotic region. These results demonstrate that a timely return of porosity is mandatory for the development and maintenance of an intact neointima. Both the structure of the fabric as well as the method of preparing the coating are crucial variables to determine the rate of biodegradation.

Animals↗
PubMed1991

PTCA of the left main stem following protective coronary artery bypass grafting.

Percutaneous transluminal coronary angioplasty (PTCA) was performed in 14 patients with significant left main stem stenosis following protective coronary artery bypass grafting (CABG). The procedure was successful in 13/14 patients (93%), achieving a decrease in mean diameter stenosis from 74% +/- 7% to 31% +/- 12% (P less than 0.01). Accordingly, the absolute stenosis diameter increased from 0.9 mm +/- 0.3 mm to 2.4 mm +/- 0.5 mm (P less than 0.01). Dissection of the left main stem artery and a transient significant fall of blood pressure each occurred in one patient. No other serious complications were noted. Eight of 13 patients (62%) with successful PTCA underwent control angiography. Restenosis had occurred in 3 of 8 patients (38%) with total occlusion of the left main stem in 1 patient. All bypass grafts were found to be patent at follow-up. Clinical evaluation in all 14 patients revealed no serious events (death, myocardial infarction, repeat revascularization procedure) during a mean follow-up period of 27 months (range 6-39 months). PTCA of the left main stem following CABG can be considered a relatively safe and effective procedure with a marked restenosis-rate but beyond that, an uncomplicated long-term follow-up.

Adult↗
PubMed1991

Resection of central primary pulmonary artery sarcoma.

Primary sarcomas of the pulmonary arteries are rare, and the diagnosis is in the majority of the reported cases established postmortem. Surgical resection of these centrally located tumors has been performed either by pneumonectomy and/or local tumor resection. We report on two patients with sarcomas of the central pulmonary arteries who underwent successful resection of the tumor and prosthetic replacement of the arteries under cardiopulmonary bypass. One patient required additional thromboendarterectomy of the right pulmonary artery branches because of secondary thrombus formation. As primary pulmonary artery sarcomas are refractory to both chemotherapy and radiation, surgical resection remains the only means of treatment. The prognosis depends entirely upon resectability, which, if necessary, should be performed with the aid of cardiopulmonary bypass. In this way, lung resection may be avoided.

Adult↗
PubMed1991

Healing parameters of a new albumin-coated knitted Dacron graft.

Knitted dacron grafts commercially coated with human albumin were implanted end-to-side between the infrarenal aorta and the bifurcation in 9 growing pigs. Uncoated knitted dacron grafts implanted in 6 pigs served as a control. Grafts were explanted after 4, 8, and 12 weeks and evaluated for neointimal healing, peeling of the inner and outer capsule, extent of neoendothelialization, absorption of the sealant, interstitial infiltration, and perigraft inflammation. Toxicological in-vitro analysis included the evaluation of residual aldehydes and plasticizers. In contrast to the uncoated knitted prosthesis, which rapidly developed a layered neointima with complete neoendothelialization, only islands of neointima were found in albumin-coated grafts after 4 weeks. The neointima remained incomplete at 8 and 12 weeks with scanning electron microscopic evidence of sharply demarcated endothelial areas. No transprosthetic bridging was detectable even after 12 weeks and peeling of the inner and outer capsule was easily provocable. These results outline that the cellular and connective infiltration of the prosthetic wall is compromised unless degradation of the sealant is completed within four weeks: the neointimal development is delayed and graft incorporation fails, leaving the outer capsule unattached.

Albumins↗
PubMed1991

[Angiographic and histologic findings in high frequency rotational ablation in coronary arteries in vitro].

High-frequency rotational angioplasty is a recently developed method for coronary angioplasty in the catheter laboratory. An elliptical burr tip (phi 1.25-2.0 mm) with embedded diamant chips (phi 40-50 microns) is rotated by a helical drive shaft at 150,000-180,000 rpm. The burr is advanced over a 0.009-inch coaxial guide wire. To show the effects of this approach in diseased and healthy vessels, which may be present before and behind a stenosis, 17 atherosclerotic coronary arteries of nine human hearts, and 18 normal coronary arteries of nine pig hearts were treated by this method in vitro. Standardized coronary angiography was performed before and after Rotablator treatment, followed by histological examination. From these data the burr-to-vessel-diameter ratio was calculated for each vessel segment and compared with the angiographical and histological outcome. Partial or complete removal of the circumference of the innermost vessel wall layers was observed regularly. The average removal of tissue in human coronary arteries was limited to the intimal layer and in the pig coronary arteries to the internal elastic membrane. In the pig coronary arteries no intimal tears or dissections occurred, in human coronary arteries tears could be seen frequently (13 of 17 vessels (76%)). Media tears were observed in 3 of 17 vessels; one (2%) media dissection could be demonstrated; no perforation occurred. Thus, the in vitro studies suggest that coronary rotational angioplasty has only a slight effect on the vessel segment next to a stenosis, regardless of the burr-to-vessel-diameter ratio.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1990

Current early results of pulmonary thromboendarterectomy for chronic pulmonary embolism.

Some patients with chronic pulmonary embolism causing severely symptomatic pulmonary hypertension have been managed by heart-lung transplantation with an associated hospital mortality of 24%. To allow comparison with pulmonary thromboendarterectomy (PTE), we have reviewed the hospital morbidity and mortality in 149 consecutive patients. From 1 October 1984 to 18 September 1989, these patients underwent PTE utilizing a standardized procedure consisting of median sternotomy, cardiopulmonary bypass, deep hypothermia and circulatory arrest for bilateral PTE in 91% (136/149) of the procedures with 7.4% (11/149) and 1.3% (2/149) undergoing right or left PTE, respectively. Ventilator dependency (greater than or equal to 5 days on respirator) occurred in 28.3% (41/146). Hospital mortality (death within 30 days or in hospital) was 11.4% (17/149). The most common causes of death were respiratory and multiorgan failure, 10 (59% of deaths) and acute pulmonary hemorrhage, 3 (17% of deaths). We conclude that PTE with an operative mortality of half that of heart-lung transplantation (11.4% vs. 24%) should be the procedure of choice for significantly symptomatic chronic pulmonary embolism. Furthermore, the hazards of immunosuppression and chronic graft rejection are avoided.

Adult↗
PubMed1990

Diagnosis of perioperative myocardial necrosis following coronary artery surgery--a reappraisal of isoenzyme analysis.

Although the routine determination of CK-MB activity is widely used after coronary artery bypass grafting (CABG), the diagnosis of a perioperative myocardial necrosis remains arbitrary. The intention of the present study was to develop discriminative enzymatic parameters of CK-MB activity in a collective of 710 patients following CABG. Patients were grouped according to their postoperative electrocardiogram (ECG). For each patient, the time activity curve of CK-MB was determined. The total amount of CK-MB was calculated by integrating the area beneath the CK-MB activity curve. Patients presenting with an unchanged postoperative ECG (group I) or a new bundle branch block with uncompromised haemodynamics (group IIa) had an uniform and low profile of CK-MB activity. Serial CK-MB activities as well as the integrated CK-MB area of these two collectives were significantly different (P less than 0.001) from values determined for patients with bundle branch block and low cardiac output (group II b) or patients with new Q waves (group III). After 24h, the 90th percentile of serial CK-MB activities of group I had declined to 18 U/l and was clearly exceeded by 90% of all patients that belonged to either group IIb or III. The 90th percentile of CK-MB areas for group I showed a value of 801 U/l x h. CK-MB areas above 801 U/l x h were seen in about 50% of all patients of group IIa.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Artery Bypass↗
PubMed1990

Thoracic research scholarship 1988: pulmonary thromboendarterectomy for chronic thromboembolic pulmonary hypertension at the University of California, San Diego.

At the University of California, San Diego pulmonary thromboendarterectomy (PTE) has emerged as an effective measure in the treatment of chronic thromboembolic pulmonary hypertension. Unresolved emboli become organized by incorporation into the vascular wall and may form strictures, webs, bands and/or membranous occlusions and cause pulmonary hypertension refractory to medical treatment. When pulmonary vascular resistance exceeds 300 dyn.sec.cm-5 and the vascular wall changes are located to begin at or proximal to the lobar artery level, surgery is indicated. The operation is performed using cardiopulmonary bypass, deep hypothermia and periods of circulatory arrest. The dissection of each segmental artery is carried out in the media layer from separate incisions in the right and left pulmonary artery at the level of the pericardial flexion. Pulmonary reperfusion edema may complicates the postoperative course, and pulmonary hemorrhage, respiratory insufficiency necessitating prolonged ventilatory support and secondary multi organ failure are main causes of hospital mortality. Between October 1984 and September 1988 103 patients with a mean age of 50 +/- 16 years underwent PTE. Consequently, pulmonary vascular resistance could be reduced from 788 +/- 370 to 299 +/- 150 dyn.sec.cm-5 and cardiac index increased from 2.0 +/- 0.6 to 3.2 +/- 0.8 l/min-m2. Hospital mortality was 11.7% (12/103 patients). Thus, pulmonary thromboendarterectomy effectively reduces pulmonary hypertension at an acceptable low risk. The results indicate that patients should be diagnose and referred for surgery as early as possible.

Adult↗
PubMed1990

New bundle branch block after coronary artery bypass grafting--evaluation by CK-MB isoenzyme analysis and transoesophageal echocardiography.

Twelve patients with a new complete bundle branch block after coronary artery bypass grafting underwent transoesophageal echocardiography (TEE). The results of TEE were compared with the pre-operative ventriculography, CK-MB isoenzyme time-release curves and clinical course. In eight patients with transient right bundle branch block or bifascicular block, low CK-MB activities and an uncomplicated postoperative course, transoesophageal echocardiography showed no new segmental wall motion abnormalities apart from a paradoxical septal movement in five. A persistent right or left bundle branch block was associated with either elevated isoenzyme activities, transoesophageal echocardiographic evidence of new segmental wall motion disturbance or both in four patients. One patient died because of fatal arrhythmia and one suffered from a prolonged low cardiac output syndrome. A transient bundle branch block is usually a benign electrocardiographic finding. In case of a persistent bundle branch block associated with elevated CK MB isoenzymes, new left ventricular wall motion disturbances indicating a peri-operative myocardial injury are easily detected by transoesophageal echocardiography.

Aged↗
PubMed1990

[Extracorporeal circulatory assistance with centrifugal pumps in postcardiotomy low-output syndrome].

From 6/86 to 5/89 seven out of 1700 (0.4%) open heart patients had to be assisted with centrifugal pumps for postcardiotomy low cardiac output syndrome. In 4 cases a left ventricular assist device (LVAD) was used, one case each had a right ventricular assist device (RVAD), an extracorporeal membrane oxygenation (ECMO) and a biventricular assist device (BVAD) with ECMO and ultrafiltration. The last 3 patients were assisted non-pulsatile without intraaortic balloon counterpulsation (IABP) and no impairment of vital organ function was observed. Four out of 7 patients could be weaned from the assist device after a mean of 30 hours (0.5-48). Three patients became long-term survivors with 2 assisted non-pulsatile. Transesophageal echocardiography (TEE) was used to determine the timing for wean off and was found to be an important adjunct to the monitoring of filling--and systemic pressure.

Adult↗
PubMed1990

[Intraoperative diagnosis of the heart and great vessels--echocardiography].

Two-dimensional echocardiography including color Doppler techniques can be used for analysis of the morphology and function and of the blood flow of the heart and the great vessels. Epicardial echocardiography has the advantage of high resolution and multiple scan planes. The restriction to the intraoperative period is a clear disadvantage. In addition, the scan planes are difficult to standardize. Transesophageal echocardiography can be used for monitoring during the whole operative period but is restricted to horizontal and/or longitudinal scan planes. It is a non-contact procedure and thus, sterile conditions are not affected. For evaluation of surgical success, intraoperative echocardiography can be used for analysis in patients with congenital heart disease, mitral valve regurgitation, hypertrophic obstructive cardiomyopathy, and aortic dissection. Acute intraoperative revisions with a second extracorporal circulation period will avoid reoperation. In patients with coronary artery disease the flow within the bypass and also the status of the anastomosis can be scanned and may contribute to reduce the perioperative infarct rate. Intraoperative echocardiography needs additional costs and man power. Only after randomized comparative prospective studies have demonstrated that patients controlled by intraoperative echocardiography have a better outcome and prognosis than patients without intraoperative control this method will become routine in open-heart surgery.

Echocardiography↗
PubMed1990

Risk factors for pulmonary thromboendarterectomy.

Pulmonary thromboendarterectomy is being performed with increasing frequency for incapacitating pulmonary hypertension caused by chronic large-vessel pulmonary embolism. However, patient-related risk factors and procedural complications associated with morbidity and mortality have not been fully defined. From Oct. 1, 1984, to April 10, 1989, we performed pulmonary thromboendarterectomy using deep hypothermia and circulatory arrest in 127 consecutive patients (62.2% male, mean age 50 +/- 16 [standard deviation], range 20 to 82 years) in whom the exposure and dissection of the pulmonary arteries and methods for myocardial protection have been standardized. End points for univariate and multivariate analyses of risk factors were reperfusion pulmonary edema leading to respiratory insufficiency as defined by ventilator dependency (greater than or equal to 5 days) (31.5%, 39/124) and hospital mortality (12.6%, 16/127). Multivariate analyses showed that ascites and need for 4 units of blood or more predicted ventilator dependency (p less than 0.03). Increased cardiopulmonary bypass times predicted both end points (p less than 0.03 to less than 0.0001), and failure to achieve at least a 50% reduction in pulmonary vascular resistance strongly predicted hospital death (p less than 0.0001). However, other factors that exhibited trends for association with one of the end points may prove important with a larger sample size. A hospital mortality rate of 12.6% for pulmonary thromboendarterectomy is acceptable when compared with approximately 25% for heart-lung transplantation, which is the only therapeutic alternative. Increased ventilator dependency and hospital mortality can be anticipated with longer cardiopulmonary bypass times and inadequate reduction of pulmonary vascular resistance.

Adult↗
PubMed1989

Influence of incremental preoperative risk factors on the perioperative outcome of patients undergoing emergency versus urgent coronary artery bypass grafting.

A retrospective analysis of 127 patients with impending myocardial infarction undergoing coronary artery bypass grafting was performed to evaluate incremental risk factors associated with perioperative mortality and morbidity. Fifty-four patients (group 1) were operated upon as emergencies within 24 h and 73 patients underwent urgent coronary revascularization within a mean of 3.4 days (group II) after admission. The incidence of non-transmural myocardial infarctions (NTMI), haemodynamic parameters, the number of diseased vessels and the incidence of a preceding percutaneous coronary dilatation (PTCA) were not statistically different between the groups. The overall perioperative mortality was 8.7% (16.7% group I, 2.7% group II). Major non-fatal complications were frequent in the surviving collective including low cardiac output in 14 patients (12.1%) and transmural or subendocardial perioperative infarction in 12 patients (10.3%). Perioperative mortality was associated with reduced left ventricular myocardial function (P less than 0.001), operation within 24 hr after onset of anginal symptoms (P less than 0.001) or subendocardial infarction (P less than 0.025) in the 4 weeks before operation. Perioperative mortality was independent of the degree of coronary stenosis, number of distal anastomoses or performance of a coronary endarterectomy. Of the patients, 90.5% (87.5% of group I and 92.3% of group II) included in a mean follow-up of 16.8 months (range 5-27 months) were graded into Canadian Heart Functional Class I. Successful coronary surgery for acute myocardial ischaemia results in excellent late functional recovery. The major risk factors for fatal perioperative outcome are reduced left ventricular function and the necessity of every early surgical intervention.

Angioplasty, Balloon, Coronary↗
PubMed1989

Emergency surgical revascularization following coronary angioplasty: evaluation of operative results by isoenzyme analysis and electrocardiography.

Seventeen patients underwent emergency coronary artery bypass grafting due to balloon catheter induced occlusion or dissection of a major coronary artery. Patients were revascularized within a maximum of 210 min from the onset of ischaemia and received an average of 1.6 distal anastomoses. A perioperative transmural or non-transmural myocardial infarction as diagnosed by CK-MB activity and electrocardiographic patterns occurred in 7 patients (41.2%). One early death resulted in an overall perioperative mortality of 5.9%. Successful preservation of myocardium was demonstrated in 10 patients by a rapid decline of CK-MB activity, no perioperative electrocardiographic changes and no requirement for inotropic support. The incidence of a perioperative myocardial infarction was independent of the anginal status before coronary angioplasty or the angiographic evidence of a complete occlusion versus a dissection. Major ischaemic myocardial complications associated with coronary angioplasty are rare but frequently catastrophic events. Fast surgical intervention is mandatory to prevent myocardial infarction or to limit the extent of injury. The operative outcome can be evaluated by careful analysis of time release curves and cumulative parameters of CK-MB activity.

Adult↗