Search PubMed⌕ Search

Biomedical subjects

A Henze

Publications and source records attributed to A Henze.

At least 73 records · Page 4Linked to original sources
PubMed1980

Late thrombotic malfunction of the Björk-Shiley tilting disc valve in the tricuspid position. Principles for recognition and management.

Among 52 consecutive patients surviving tricuspid valve replacement with the Björk-Shiley tilting disc valve, follow-up extends between 1/2-9 years, mean 4.9 years. Four patients suffered thrombotic obstruction of their tricuspid prosthesis on 8 occasions, an incidence of 3.2%/year. Ebstein's anomaly and deficient anticoagulation were identified as likely contributory factors, but the complication remained unexplained in 2/8 instances. Thrombotic malfunction of the tricuspid prosthesis seems to constitute a relatively benign clinical entity with mild manifestations and diagnostic possibilities by non-invasive methods. Relief by means of thrombolytic treatment in the form of streptokinase (Kabikinase) (4) or replacement of the clotted prosthesis (4) involved neither disabling complications nor mortality. Our clinical observations and experimental studies suggest that thrombolytic therapy is effective, provided that prosthetic malfunction is due to a recent red clot, whereas encapsulation of the prosthetic disc by organized white-grey pannus necessitates re-operation. Streptokinase treatment should be attempted before surgery, but it is hardly meaningful to proceed for more than 24 hours. Restored prosthetic function within this time limit indicates the likely resolution of a red clot.

Angiocardiography↗
PubMed1979

Surgical treatment of aneurysms of the ascending aorta: early experience with the sinus-shaped composite dacron graft.

This paper reviews the early and late results of 36 operations for aneurysms of the ascending aorta. Cystic medial necrosis was the predominant cause of aneurysm formation (56%), followed by arteriosclerosis (25%), previous aortotomy (11%) and syphilitic aortitis (8%). Dissection was encountered in 42%. The ascending aorta was replaced by a tubular Darcron graft in 26 patients, whereas 10 underwent aneurysmorrhaphy. Additional procedures were aortic valve replacement (27), resuspension of the aortic commissures (4) and coronary ostial implantation into sinus-shaped composite Dacron graft (4). Hospital mortality (0--18 days) was 8/36 patients (22%), but higher with cystic medial necrosis (30%), dissection (33%), duration of ECC greater than 180 minutes (38%), graft replacement (44%), emergency operation (45%) and heart volume greater than 900 ml/m2 BSA (50%). Late mortality (average 3 years) was 29%, but higher with cystic medial necrosis (33%), following aortic valve replacement (36%) and during anticoagulation (47%). Late cumulative survival (average 3 years) was 47% for the entire series, but only 33% in the presence of cystic medial necrosis. The poor overall prognosis for patients with cystic medial degeneration was closely related to a high incidence of fatal anastomotic complications and late deaths from cerebral haemorrhage during anticoagulation. Radical exclusion of the diseased aortic wall and omission of long-term anticoagulation are therefore desirable in order to lower the mortality rate. Surgery concerns the aneurysm per se, the aortic incompetence and the coronary ostia. The sinus-shaped composite graft with a Björk-Shiley prosthesis at its base appears to be a promising device for such a procedure, which should be performed electively, following early diagnosis in order to prevent dissection and emergency operations.

Adolescent↗
PubMed1979

Comparison between the in vitro flow dynamics of the standard and the convexo-concave Björk-Shiley tilting disc valve prostheses.

In the new convexo-concave model of the Björk-Shiley prosthesis the disc pivots 2.5 mm downstream, creating a space between the disc and the ring when the disc tilts open. Its flow dynamics were compared with those of the standard model under steady flow rates 0--32 1/min of a water-glycerin mixture employed as blood-analogous test fluid. The following results are valid for corresponding sizes of the conventionally used 21, 23, 25, 27, 29 and 31 mm prosthetic valves of the two models. The transprosthetic pressure fall varied directly, but in a parabolic fashion with the steady flow rate for all the partial and full flow orifices. The resistance to flow 0--32 1/min for the full flow orifice of the convexo-concave prosthesis was in average 16% lower than that of the standard model, with highly significant differences for the 21 and 23 mm prostheses (p less than 0.001). There was a redistribution of flow towards the smaller prosthetic opening from 23% (S.D. +/- 1.4) for the standard model to 30% (S.D. +/- 2.4) for the convexo-concave model (p less than 0.001). The minimum steady flow rate required to maintain the convexo-concave disc in completely open position (60 ml/sec) was only half that (37--50%) required for the standard disc (125 ml/sec) (p less than 0.001). Regurgitation through the closed prosthesis varied directly and linearly with the driving pressure and was slightly but definitely lower with the convexo-concave model than with standard model. The main features of the new design are decreased resistance to flow, redistribution of the flow within the prosthesis in order to prevent stasis along its smaller orifice, diminished opening resistance and reduced regurgitation. It is concluded that the flow dynamics of the convexo-concave model Björk-Shiley prosthesis constitute a significant improvement over those of the standard model.

Biomechanical Phenomena↗
PubMed1979

Ten years' experience with the Björk-Shiley tilting disc valve.

More than 10 years of clinical experience with 1,800 consecutive valve replacements with the Björk-Shiley tilting disc valve were focused on improving its durability, flow dynamics, thromboresistance, and in vivo functional control. Although the original Delrin disc functions excellently after 10 years in the human circulation, the durability of the prosthetic valve was further prolonged by the introduction of pyrolytic carbon as disc material. The opening mechanism was also reinforced by integrating the bearing struts with the valve ring. No other presently available heart valve prosthesis shows such a low resistance to flow for a given tissue diameter. The disc was equipped with a ring-shaped radiopaque marker that permitted noninvasive functional control. The 5 year survival rates were 82% after aortic, 66% after mitral, and 66% after mitral and aortic valve replacements, including the operative mortality rates. The incidence of systemic emboli was 0.7% per year after aortic, 4.2% per year after mitral, and 2.2% per year after mitral and aortic valve replacements with anticoagulation treatment. The incidence of obstruction by thrombosis was 0.3% per year for aortic, 1.3% per year for mitral, and 2.3% per year tricuspid prostheses. The new convex-concave model decreases the stagnation zone behind the disc, decreases emboli from 4.2% to 1.2% per year after mitral valve replacement, and has a lower gradient.

Aortic Valve Stenosis↗
PubMed1978

Clinical evaluation of the Björk-Shiley tilting disc valve in the tricuspid position. Early and late results in 10 isolated and 51 combined cases.

Tricuspid valve replacement with the Björk-Shiley tilting disc valve was performed in 61 consecutive patients with either organic disease causing valve malfunction or functional regurgitation of severe degree. The early mortality rate was 21% (13/61) for the entire series. It was 10% (1/10) for tricuspid valve replacement alone, 27% (9/33) for mitral and tricuspid valve replacement, and 18% (3/17) for triple valve replacement. Age over 60 years, functional capacity group IV (N.Y.H.A.) and heart volume over 900 ml/m2 BSA were factors associated with a high operative mortality. There were 3 late deaths, 42, 42 and 45 months, respectively, after surgery, due to arrhythmia (2) and anticoagulant complications (1). The Björk-Shiley prosthesis has functioned well and with satisfactory clinical improvement in the majority of the 48 long-term survivors, for an average period of 2.8 years. There were, however, 3 cases of prosthetic valve failure due to thrombotic obstruction following isolated tricuspid replacement because of Ebstein's anomaly (2) and traumatic tricuspid valvular incompetence (1). Reoperation with insertion of a new Björk-Shiley prosthesis involved no mortality. One patient, however, had a recurrent prosthetic thrombosis which was successfully treated with streptokinase. Only one patient in the series, who underwent triple valve replacement, suffered from systemic embolism, an incidence of 0.7 per 100 patient years. There were no episodes of pulmonary embolism or infective endocarditis.

Adolescent↗
PubMed1977

Combined aortic and mitral valve replacement with the Björk-Shiley tilting disc valve prosthesis. Early and late results in 75 consecutive patients.

This study evaluates the early and late results of combined aortic and mitral valve replacement with the Björk-Shiley tilting disc valve prosthesis in 75 consecutive patients operated upon during a 6-year-period commencing October 1969. The Delrin disc model Björk-Shiley prosthesis was inserted in the first 20 patients and the pyrolytic carbon disc model in the remainder. The opening angle was increased from 50 degrees to 60 degress and the Teflon sewing ring was designed with two flanges in the pyrolytic carbon disc mitral model. The patient material was characterized by marked cardiomegaly, impaired physical working capacity, hypokinetic central circulation, pulmonary hypertension and a 59% incidence of atrial arrhythmias before operation. Surgery was performed during generalized hypothermia to 30 degrees C and selective coronary perfusion, and the mitral valve was always replaced first. There were no intra-operative deaths, although 7/75 patients (9%) died while in hospital. Twelve patients (16%) died in average 19 (2-59) months postoperatively. Thrombo-embolic complications, which were frequently associated with poor anticoagulation, occurred in 9 patients and were fatal in 4 cases, corresponding to an incidence per patient month of 0.005 and 0.002, respecitvely. This risk was not affected by the type of prosthesis. One patient required operative repair of an aortic paraprosthetic leakage. Clinical improvement was found in 88% of the long-term survivors. The maximal working capacity increased in average 41% over the pre-operative value (p less than 0.001) and cardiac enlargement diminished in average by 22% (p less than 0.001). The incidence of atrial arrhythmias decreased slightly to 48%. Haemolysis was mild and without clinical significance. The actuarial curve indicated a 75% survival rate 3 years after operation.

Adolescent↗
PubMed1977

Results five to seven years after aortic valve replacement with the original Delrin disc model Björk-Shiley prosthesis.

Isolated aortic valve replacement with the original Delrin disc model Björk-Shiley prosthesis was performed in 128 patients at the Thoracic Surgical Clinic, Karolinska Sjukhuset, Stockholm, Sweden, during the period 1969--71. No patient was lost at follow-up 5--7 years after surgery. The early mortality rate was 5% (6/128) and the actuarial late death rate at 5 years was 13% (16/122). This late survival rate represents a significant improvement over the natural history of symptomatic aortic valvular disease. Age at operation and the particular size of prosthetic valve inserted had no bearing on late mortality, while large heart size and aortic incompetence were associated with a higher incidence of late deaths. There was only one death due to thromboembolism and no case of mechanical prosthetic valve dysfunction. The incidence of thrombo-embolism was 0.7 per 100 patient years with continuous anticoagulation therapy during sinus rhythm, but increased during atrial fibrillation and after discontinuation of anticoagulation. Survival without complications was 75% at 5 years among the 122 patients discharged from hospital.

Adult↗
PubMed1977

Isolated mitral valve replacement with the Björk-Shiley tilting disc valve prosthesis. A six-year review and a comparison between the Delrin and the pyrolytic carbon disc models.

Replacement of the mitral valve with the Björk-Shiley tilting disc valve prosthesis was performed in 203 consecutive patients with isolated mitral valvular disease at Karolinska Sjukhuset, Stockholm, Sweden, during the 6-year period ending December 1975. Results with the Delrin and pyrolytic carbon disc prostheses were analysed with actuarial techniques and compared in terms of mortality rate, incidence of thrombo-embolism and frequency of re-operation. Early (4%) and late mortality rates (7.5 deaths per 100 patient years) were similar with both types of prostheses. No case of primary mechanical prosthetic failure was encountered. The pyrolytic carbon disc prostheses have obviously decreased the incidence of systemic emboli from 9.6 to 5.3 per 100 patient years and so far eliminated mortality due to embolization. This benefit is probably related to the increased opening angle from 50 degrees to 60 degrees in the pyrolytic carbon disc model, which causes less resistance to blood flow. Thrombotic obstruction of the prosthetic valve, however, has been a persistent problem in the order of 3.3 incidences per 100 patient years. Only one patient in twelve involved was referred to our clinic and could be saved by an emergency re-operation. The development of the ring-shaped radiopaque marker in the tilting disc occluder provides a valuable tool for instant diagnosis of partly or completely obstructed disc motion caused by thrombosis. Disc motion can be easily visualized by cineradiography or fluoroscopy. Early diagnosis of and emergency operation for thrombotic obstruction of the prosthesis will reduce the mortality due to this dangerous complication.

Adolescent↗
PubMed1977

Left ventricular rupture as a complication of mitral valve replacement.

We are not the first to attempt repair of left ventricular rupture complicating mitral valve replacement, as 18 analogous cases have been reported earlier in the literature. Our series comprises 8 patients, 5 of who, survived. A review of these 26 cases provided several facts of interest to surgeons dealing with this complication. The rupture occurred either as a laceration in the posterior atrioventricular groove (type I, 16 of 26 patients) or as a perforation of the midportion of the left ventricle (type II, 10 of 26 patients). Intraoperative rupture (17 of 26 patients) was usually detected on termination of bypass, whereas delayed rupture (9 of 26 patients) occurred after chest closure or in the recovery room. The morality rate was about 50 per cent for the intraoperative type, and no patient survived a delayed rupture. The prognosis appeared to be most in intraoperative type II lesions. The main factors affecting the prognosis were (1) instant reinstitution of extracorporeal circulations and (2) avoidance of the circumflex coronary artery during repair of type I lesions located close to the anterolateral mitral commissure. Attempts to suture a ventricular rupture on the pressure-loaded, beating heart were always unsuccessful and frequently extended the laceration. Patients with the delayed type of rupture died of hemorrhage before they could again be placed on bypass. It may be preferable to reopen the lefr atrium in order to repair a type I laceration. In type II perforations, direct repair with buttressed sutures should be attempted from the exterior of the heart. The angulated metal cannula for drainage of the left ventricle was identified as a possible, but not previously reported, cause of myocardial perforation. It is hoped that the use of a soft cannula or a metal cannula with an angle of 60 degrees instead of 90 degrees will reduce the incidence of this complication.

Female↗
PubMed1977

Radiopaque marker in the tilting disc of the Björk-Shiley heart valve. Evaluation of in vivo prosthetic valve function by cineradiography.

This paper describes a new, noninvasive method for evaluating the in vivo function of the Björk-Shiley tilting disc valve in the aortic, mitral, and tricuspid positions. The tilting disc was equipped with a ring-shaped radiopaque marker, which permits visualization of the motion of the disc by both cineradiographic and fluoroscopic studies. A beam direction corresponding to the axis of motion of the disc should be sought for calculation of the prosthetic opening angle, whereas prostehtic valve closure is demonstrated by a beam direction deviating 20 to 30 degrees from the valve ring plane. Complete opening to 60 degrees and closure of the prosthetic valve, indicating free motility of the tilting disc, were confirmed by cineradiograms. The error of estimation of the in vivo opening angle is small with deviations of less than 15 degrees from the ideal beam direction and negligible for opening angles approaching 60 degrees. Deviations in two planes simultaneously cause less error than deviation in one plane. The radiopaque marker was designed to detect mechanical valve failure owing to thrombotic obstruction. The incidence of this particular complication was 8.1 per 100 patient-years after aortic valve replacement without anticoagulation treatment. With anticoagulation, this incidence was zero after aortic and 2.5 after mitral valve replacement. In our clinical experience to date, which comprises over 1,250 implants, we have not encountered a single case of primary mechanical valve dysfunction. Our current program includes a change-over to the radiopaque tilting-disc model of the Björk-Shiley prosthesis, which was introduced at this clinic in March, 1975.

Aortic Valve↗
PubMed1976

Coronary ostial stenosis: a complication of aortic valve replacement of coronary perfusion.

Coronary ostial stenosis developing after aortic valve replacement is a clinically well-recognized entity. This non-atheromatous intimal proliferation may be limited to the proximal part of the coronary artery, probably as a complication of intra-operative coronary perfusion. It may also occur in association with widespread intimal thickening in the aortic root, presumedly as a reaction to turbulence around aortic ball valve prostheses. We have encountered this process in 2/508 patients (0.4%), who underwent aortic valve replacement with the Björk-Shiley tilting disc valve prosthesis. The coronary perfusion technique was identical in all the operations.

Aortic Valve↗
PubMed1975

Management of thrombo-embolism after aortic valve replacement with the Björk-Shiley tilting disc valve. Medicamental prevention with dicumarol in comparison with dipyridamole - acetylsalicylic acid. Surgical treatment of prosthetic thrombosis.

Dicumarol anticoagulation poved very effective in the prevention of thromboembolic complications after aortic valve replacement with the Björk-Shiley tilting disc valve. We have, however, encountered six late deaths because of massive cerebral hemorrhage, which represent 3% of the patients who were maintained on dicumarol medication at that time. This unacceptable mortality prompted us to introduce two programmes, one without anticoagulation and another one with dipyridamole-acetylsalicylic acid. Furthermore, dicumarol was terminated in patients with haemorrhagic episodes, instable anticoagulation, pregnancy, and in those reguiring surgery. The results were disappointing, however, and the majority of the patients involved were therefore put on dicumarol medication. Eleven of the 64 consecutive patients taking dipyridamole - acetylsalicylic acid had thrombo-embolic episodes during a mean follow-up period of 9 months...

Adult↗