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Biomedical subjects

V O Björk

Publications and source records attributed to V O Björk.

At least 19 recordsLinked to original sources
PubMed1995

Work capacity and central hemodynamics thirteen to twenty-six years after repair of tetralogy of Fallot.

Exercise tests and cardiac catheterization were performed in 53 patients, 13 to 26 years after intracardiac repair of tetralogy of Fallot. At the time of repair, the median age was 7 years, and 60% of patients with cyanosis had had a previous palliative procedure. The right ventriculotomy was closed without a patch in 21 patients (40%), a patch restricted to the right ventricle was inserted in 18 patients (34%), and in 14 (26%) the patch extended across the pulmonary anulus. At follow-up, 94% of the patients were free of symptoms. Symptom-limited work capacity was 87% of the predicted value (95% confidence limits, 82% to 94%). Work capacity was inversely related to age at follow-up, to right ventricular systolic pressure at rest, and to presence of moderate or severe pulmonary valve regurgitation. Cardiac output in relation to oxygen uptake was reduced in 74% of patients during exercise. In 12 patients (23%), systolic pressure at rest in the right ventricle was 50 mm Hg or higher. Systolic pressure during exercise in the right ventricle was lower in patients without a patch than in those with a patch and was abnormally high in all groups compared with healthy subjects. The ratio of right to left ventricular pressure was significantly lower than measurements taken immediately after repair. An intracardiac left-to-right shunt was present in 6 patients (11%). Three patients required invasive treatment as a result of our follow-up. We conclude that work capacity was moderately reduced 13 to 26 years after repair of tetralogy of Fallot and was adversely influenced by right ventricular hypertension and pulmonary valve regurgitation. Intermittent lifelong surveillance is advocated, because patients without symptoms may have hemodynamic abnormalities that necessitate intervention.

Adolescent↗
PubMed1994

Mitral mechanical valve without long-term anticoagulation. Eight-year follow-up.

In 12 patients with sinus rhythm (including 5 children and 6 young women), mitral valve replacement was performed with a microporous-surfaced valve similar to the Björk-Shiley Monostrut. After the first 3 months, permitting endothelialization of the suture ring to continue over the groove and adjacent metal valve ring, no long-term anticoagulant treatment was given. There was no thromboembolic complication in this group during follow-up for 6-8 years, during which four women gave birth to a total of seven children. In eight other cases, one mitral case with atrial fibrillation, anti-coagulant was not discontinued, and in the remaining aortic cases it was reinstituted. One of them (with atrial fibrillation) had hematuria during inadequate anticoagulant medication, but no thromboembolism. Of five patients with only aortic valve replacement, two had thromboembolic complications, one without residual symptoms and one with slight hand weakness. Another had a transient ischemic attack while on anticoagulant and acetylsalicylic acid was added. Two patients with aortic and mitral valve replacement died, one from heart tamponade and the other from venous thrombosis with pulmonary embolism.

Adolescent↗
PubMed1994

Pulmonary function thirteen to twenty-six years after repair of tetralogy of Fallot.

Lung function was evaluated in 68 patients 13 to 26 (median 19) years after repair of tetralogy of Fallot. Age at repair was 7 years (9 months to 42 years) and 51% had a palliative shunt. An outflow patch was inserted in 56%. Median vital capacity was 84% of predicted, forced expiratory volume in 1 second 83%, maximal voluntary ventilation at 40 breaths/min 70%, and diffusing capacity for carbon monoxide 77% of predicted. Scintigraphy demonstrated abnormal pulmonary perfusion in 86%. Average right lung perfusion was 57% (predicted 52%). Regional hypoperfusion could in some patients be explained by previous palliative shunt, pulmonary artery obstruction, or presence of aortopulmonary collaterals. Median symptom-limited work capacity was 82% (95% confidence limits 78% to 90%) of predicted. Twenty-eight physically active patients had high values for symptom-limited work capacity, vital capacity, forced expiratory volume in 1 second, and maximal voluntary ventilation at 40 breaths/min compared with those of inactive patients. Lung function variables were related to physical exercise and previous palliative shunt. Moderate or severe pulmonary valve incompetence had negative but not significant influence on lung function. There was no significant influence of acyanosis before repair, use of transannular patch, duration of follow-up, or smoking. We found moderately reduced work capacity and lung function late after repair of tetralogy of Fallot that did not cause symptoms. Lung function variables were high in young active male patients and low in patients with previous palliative shunt. A better lung function in active patients indicates that physical activity should be encouraged after repair of tetralogy of Fallot.

Adolescent↗
PubMed1992

The five-year evaluation of a mechanical heart valve without anticoagulation in goats.

Two 5-year observations of goats with microporous surfaced Björk-Shiley Monostrut mitral heart valves without anticoagulation show the important point that one went through four the other two normal pregnancies with delivery of fourteen kids. Furthermore, the local findings on the valves suggest that the porous surface should be used only to invite a thin, endothelialized neointima over a preferably carbon-coated suture ring to continue over the groove and to the adjacent part of the valve flange. The vertical or central part of the ring and the struts, in the control material with a polished surface, have never been the origin of a thrombus and should therefore be polished.

Animals↗
PubMed1991

Repair of complete atrioventricular canal. 15 year's experience.

Corrective surgery for complete atrioventricular canal was performed over a 15-year period on 72 patients, 49 of whom had Down's syndrome: 46 were without major associated cardiac anomalies and 15 had previously undergone pulmonary artery banding. The pressures in the right and left ventricles equilibrated in 77% of the patients. The early mortality rate was 18% and the late mortality 7%. At follow-up 4% of the patients had severe mitral incompetence and 6% had severe tricuspid incompetence. The mean reduction of pulmonary artery pressure was 40 mmHg. The mean peak systolic pressure ratio between pulmonary artery and aorta was 0.73 before repair and had fallen to 0.38 at follow-up catheterization, when 88% of the patients were asymptomatic. Early repair in the first year of life is nowadays preferred in order to avoid progressive pulmonary vascular disease. Although the alternative of first-stage pulmonary artery banding gave lower (13%) mortality at the corrective operation, it cannot be recommended if atrioventricular valvular incompetence is significant.

Cardiac Catheterization↗
PubMed1990

Development of an artificial heart valve.

When I reviewed the 21-year results with the Björk-Shiley tilting disc valves, I found out that to date, we still have to use these disc valves and all mechanical heart valves with anticoagulation therapy. The highest incidence of valve-related postoperative deaths after aortic valve replacements in Stockholm was anticoagulation-related bleeding, which continued at a rate of about 1% year after year. There is a need to improve the quality of life for heart valve patients, especially for children, for young females who want to have children, for the older generation who are on medical treatment, and for all patients in whom long-term anticoagulation of a perfect quality is impossible to guarantee. A series of tests on goats has been performed, using the Björk-Shiley Monostrut valve used in 2,024 patients at the Karolinska Hospital in Stockholm and in 75,000 patients worldwide for up to 8 years with a modification of a microporous surface. In the mitral position, this modified partially microporous-surfaced Björk-Shiley Monostrut valve has permitted goats to live for 5 years with four normal pregnancies without anticoagulation therapy.

Animals↗
PubMed1990

Optimal microporous surface for endothelialization of metal heart valves in the blood stream.

Optimum surface porosity of a prosthetic heart valve was obtained with use of microspheres less than 40 microns in diameter. A thin and translucent neointima then forms on the valve surface, so thin that its nutrition is supplied by diffusion and thickening will not take place, thereby avoiding interference with the functioning disc. Larger microspheres tend to promote clotting and buildup of fibromyxoid soft tissue, which may cause such interference.

Animals↗
PubMed1990

Modified porous metal-surfaced Björk-Shiley monostrut heart valve. Long-term study in goats without anticoagulation.

To diminish the risk of thrombosis on a mechanical heart valve without anticoagulation, specific areas of the valve ring should be polished, as thrombosis has not been found to start there. By limiting the porous-surfaced area to the groove and the adjacent part of the flange, the thin endothelialized covering of the carbonized suture ring will continue over the groove and top of the flange to the high-flow area. As the high-flow areas that are not completely covered with the neointima, i.e. the struts and the vertical or central portion of the valve ring, are at increased risk of bacterial invasion if their surface is porous, they should be left uncoated and polished.

Animals↗
PubMed1989

Early mortality after 2,902 coronary artery bypass operations.

A review of 2,902 coronary artery bypass grafting operations is presented. During the 16-year study period the mean patient age rose from 51 to 59 years and the average number of grafts per patient from 1.5 to 3.0. There were 81 early deaths (2.8%, the most common cause being myocardial infarction (68%). Left main stem stenosis was present in 23 of these 81 patients and depressed left ventricular function in 30. Compared with the survivors, the deceased patients were characterized by higher age, proportionately large numbers of women, combined procedures and reoperations and less use of internal mammary artery grafts. Of the 94 patients aged greater than or equal to 70, 11 died (12%). The perioperative mortality was significantly greater (p less than 0.05) in women than in men (20/457 vs. 61/2445 viz. 4.4% vs. 2.5%). Combined operations were associated with 8.7% (27/311), reoperations with 6% (6/101) and coronary endarterectomy with 5% (4/75) early deaths. In the last year of the study there were three early deaths among 359 patients (0.8%) who underwent primary isolated coronary bypass grafting without endarterectomy. The perioperative risks fell steadily during 16 years, despite rising proportions of older patients, combined procedures, reoperation and coronary endarterectomy.

Adult↗
PubMed1989

Mechanical failure of the Björk-Shiley valve. Updated follow-up and considerations on prophylactic rereplacement.

The early production series of the 29 to 31 mm 70-degree convexo-concave (CC70) Björk-Shiley heart valves constitutes a subgroup of CC70 values with an extra high risk of outlet strut fracture. The hazard function for mechanical failure among these valves has remained almost constant over a 7-year follow-up period, and the 7-year actuarial incidence of mechanical failure among these valves is 12.5%. Selected patients with these valves will be considered for prophylactic rereplacement.

Aortic Valve↗
PubMed1988

Albumin prevents erythrocyte crenation in patients undergoing extracorporeal circulation.

Free fatty acid-induced massive erythrocyte crenation has been reported in patients undergoing extracorporeal circulation (EC), suggesting that the crenated cells impair microcirculatory flow and tissue oxygenation during and after the operation. Effect of albumin administration on erythrocyte crenation was examined in 18 patients undergoing coronary bypass operation: 9 patients were given 25 g and another 9 patients were given 50 g of human albumin as a part of the priming solution. Erythrocyte crenation was almost completely prevented in the patients given 50 g albumin. Crenated erythrocytes during EC were 3.6 +/- 2.3% (mean +/- SD) of all erythrocytes and 2.8 +/- 3.7% after EC. This was significantly lower than in patients without albumin administration (63.4 +/- 34.0% during EC and 28.6 +/- 33.3% after EC, n = 20). But the effect was less striking in the patients given 25 g albumin, 32.4 +/- 39.1% during and 28.3 +/- 40.8% after EC. Maintaining an adequate level of plasma albumin is important in preventing erythrocyte crenation during EC, improving microcirculatory flow in patients undergoing open heart surgery.

Aged↗
PubMed1988

Aortic origin of the right pulmonary artery: a cause of heart failure in infancy at high altitude.

The development of technique for surgical correction of aortic origin of the right pulmonary artery is described. In the first patient, aged 7 years, the operation was performed via bilateral thoracotomy, with standby for extracorporeal circulation, and the right pulmonary artery was anastomosed directly to the left, using side clamps on both aorta and left pulmonary artery. The currently preferred procedure is to operate as early as possible in infancy, using perfusion at 30 degrees C with ventricular fibrillation and without cross-clamping of the aorta. Wide mobilization of the pulmonary artery probably prevents stenosis at the end-to-side anastomosis.

Altitude↗
PubMed1988

Angiographic studies of internal mammary artery grafts 11 years after coronary artery bypass grafting.

Of 99 consecutive patients with 101 internal mammary artery grafts, 91 of 97 hospital survivors (94%) underwent angiography 2 weeks after operation, 84 of 96 survivors (88%) after 1 year, 66 of 88 survivors (75%) after 5 years, and 37 of 69 survivors (54%) after 11 years (range 10 to 13 years). Thirty-five of the 37 patients who consented to a fourth postoperative angiographic study (95%, confidence limits 86% to 100%) still reported relieved angina 11 years after the operation, and seven patients (19%, confidence limits 5% to 33%) were completely free of symptoms. Angiographic findings in 30 patients with symptoms of angina were progression of the coronary artery disease in 22, (73%, confidence limits 56% to 91%), occluded or stenosed grafts in nine (30%, confidence limits 12% to 48%), and nonbypassed obstructions in six patients (20%, confidence limits 4% to 36%). The cumulative 11-year patency rate was 88%, confidence limits 81% to 95%, for internal mammary artery grafts and 61%, confidence limits 45% to 76% for saphenous vein grafts. Six of 18 saphenous vein grafts (33%, confidence limits 19% to 58%) occluded in the interval between 5 and 11 years after operation, and gross wall irregularities were observed in six of the 12 patent saphenous vein grafts. Unligated side branches and stenosis of the internal mammary artery did not prevent long-term graft patency. Internal mammary artery graft failures were related to technical errors during the operation and occurred when the internal mammary artery was used to bypass a low-grade coronary artery stenosis. In one patient, regression of a coronary artery stenosis was associated with a marked decrease in luminal size of the internal mammary artery graft before the 5-year follow-up. This single internal mammary artery graft became occluded in the interval between 5 and 11 years after the operation. Eleven of 36 internal mammary artery grafts (31%, confidence limits 14% to 47%) increased 15% to 40% in luminal diameter as a result of increased myocardial blood demand before the 11-year follow-up.

Angiography↗