Aortic valve replacement withthe Bjork-Shiley tilting valve prosthesis · Aorticvalve...

British Heart Journal, 1971, 33, Supplement, 42-46.

Aortic valve replacement with the Bjork-Shileytilting disc valve prosthesisViking Olov Bj6rkFrom the Thoracic Surgical Clinic, Karolinska Sjukhuset, Stockholm, Sweden

The Bj6rk-Shiley tilting disc valve (Bjork,1969) has now been used in more than I20cases, 9I in the aorta and 3I in the mitral area(Bjork, I970a). The 9I aortic valve replace-ments had a primary mortality of 8 8 per cent.There were 2 severe complications necessitat-ing reoperation, one paravalvular leakage, andone aortic incisional aneurysm. The first 47cases, followed up from 6 to I7 months, havebeen carefully investigated with aortographyand left-heart catheterization at restand duringexercise (Bj6rk, I97ob). The systolic peakpressure gradient, especially during exercise,was significantly lower over the Bjork-Shileyvalve (i6 mm. Hg) than over the Starr-Edwards valve (4I mm. Hg) and the Kay-Shiley valve (38 mm. Hg). As the resultingblood trauma was decreased the remaininghaptoglobin in plasma was twice as high in thepatients with Bjork-Shiley valves as in thosewith Starr-Edwards and Kay-Shiley valves.

After more than I0 years' clinical experi-ence with artificial heart valves, two factorshave been found most important for the result:the durability of the valve, and the pressuregradient over the prosthesis.

After 8 years' excellent function with theStarr-Edwards ball valve prosthesis I wasat first hesitant about trying other artificialvalves. It was, however, the unacceptable highpressure gradient over the smaller ball valvesthat necessitated the introduction of a newtilting disc valve prosthesis for aortic valvereplacement. Seven out of 9 cases with aorticvalve replacement with the No. 8 Starr-Edwards ball valve prosthesis died, and restinggradients up to 70 mm. Hg were encountered.The results with the Smeloff-Cutter ballvalves and Kay-Shiley disc valves were alsounsatisfactory in narrow aortic roots, wherea Dacron outflow prosthesis often had to beutilized to enlarge the clearance between thedisc and the aortic wall.

Complications with calcification andshrinkage of cusps fashioned from the pa-tient's own pericardium or fascia for aorticvalve replacement in my own experience

(Bj6rk and Hultquist, I964), and the report ofonly I in 3 good long-term results of homo-graft replacement (Barratt-Boyes et al., I969),have convinced me that the best durabilitymay be achieved with artificial valves.

Apart from durability, the lowest pos-sible gradient is the only other most importantfeature of an artificial valve. To decrease thegradient a valve without a central occludermust be used. The first such valve I used wasthat constructed by Wada-Cutter. After 8months, in cases with concomitant sinus ofValsalva or ascending aortic aneurysm, themetal shoulder, hitting the same area at eachheart beat, caused a groove in the Teflon discand resulted in valvular insufficiency with theWada-Gutter valves in 2 of ii patients withinone year.

The aortic tilting disc valveTo eliminate the drawback in construction ofthe Wada valve, a new central flow tilting discdesign with a free floating and rotating Delrindisc has been introduced (Fig. i). The freefloating disc is uniquely suspended in aStellite cage with a vertical sewing ring of thinTeflon. The Delrin disc tilts open to 600 andprovides central flow. (The mitral versionopens only to 500, as the velocity of bloodflow is much less through the mitral valve.)The pivot point of the disc shifts towards thecentre as the disc closes, thereby reducingclosure impact velocity. The disc has an ex-tremely low mass inertia: its weight in a 23mm. valve is only 034 g. The disc does notoverlap the ring, but fits within the orificearea. It can usually rotate one turn in Ioo-2ooheart cycles.

Flow testsIn a tilting disc valve prosthesis the ratio oftotal orifice area to tissue diameter is signifi-cantly increased to permit laminated flow.The low gradient of the disc prosthesisand the fact that the disc does not hit the ringduring diastole have reduced blood trauma toa minimum. When small particles of gold leaf

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Aortic valve replacement with Bjork-Shiley tilting disc valve 43

FIG. I (a) The Bjork-Shiley aortic valve prosthesis with a free floating disc tilted open to600 in a Stellite cage. The outflow cage leg in the central excavation of the disc will keep therotating Delrin disc in place. (b) The valve viewedfrom the aortic side in a closed position.(c) The valve viewedfrom the left ventricular side in a closed position. (d) The valve viewedfrom the left ventricular side in an open position.

are suspended in the fluid in the pulse dupli-cator a laminated flow will be demonstratedthat has never been observed with other valvestested (Fig. 2). Around a ball valve prosthesisa turbulent flow is demonstrated. In pulseduplicator studies with an aortic flow of i5o-300 ml./sec. the gradient of the tilting discvalve is significantly lower than that over othercommonly used and tested valves such asStarr-Edwards, Kay-Shiley, Wada-Cutter,and Smeloff-Cutter models. The comparisonwas made with prostheses of the same externaldiameter of 23 mm., a stroke volume of 70ml., and a pulse frequency of 70 at an aorticpressure of I25/75 mm. Hg, and resulted in agradient of only 2-5 mm. Hg with the Bjork-Shiley tilting disc valve prosthesis (Bjork andOlin, I970) (Fig. 3).Durability testsThe durability of the tilting disc valve pros-thesis was tested by accelerated cycling at1200/min. of non-rotating Delrin discs,utilizing a test fluid of glycerin and waterwith a specific gravity of II00. In these teststhe discs were tethered to prevent rotationand to magnify the wear effect in localizedareas. In pulse duplicator studies at a pulserate of 5o-I5o cycles/min. the disc rotatedabout one revolution every 200 pulses. Inaccelerated cycling no rotation of the disc wasencountered and a wear depth of O'I5 mm.was found after 5 years. From this study thein vivo durability is estimated to be approxim-ately 30 years for a non-rotating 23 mm. tiltingdisc valve prosthesis in the aortic area, and 20years for the large 29 mm. valve without rota-tion of the disc.

Two patients have been reoperated after 9and 7 months and no visible wear has beendetected on the discs. However, a microphoto-graph ofthe Delrin disc, implanted in a patientfor 7 months and removed for inspection atreoperation, showed an indentation of o ooo5inch, which should correspond to a finctionallife of more than IOO years. The Delrin wasfound to be 7 times more resistant to wear than

FIG. 2 Photographic visualization of thelaminated flow in the Bjdrk-Shiley aorticvalve, using a shutter speed of 1/20 sec., duringinjection of an illuninated suspension of smallparticles ofgold leaf (Bjork and Olin, 1970).



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PULSATILE FLOW ( H20 )

mm Hg

S-E 9* /

K-S 3 W-C23-S-C 4

B-S 2-AVF ml/ sec.

..~~~~~~~~~o

150 200 250

FIG. 3 Mean pressure difference in mm. Hg in relation to aortic valve flow (A VF) in ml./sec.obtained in the pulse duplicator studies of valves with identical tissue diameter, Starr-Edwards(S-E 9), Kay-Shiley (K-S 3), Wada-Cutter (W-C 23), Smeloff-Cutter (S-C 4), and Bjork-Shiley (B-S 23). The gradient was significantly lower in the Bjork-Shiley valve compared withthe other valves tested (Bjork and Olin, 1970).

Teflon and twice as resistant as Halon duringthese wear tests.

Operative procedureAll patients have been operated upon withthe AGA heart-lung machine with the Bjorkdisc oxygenator and automatic blood levelcontrol, using both left and right coronaryartery perfusion at 30°C. The coronary arteryperfusion is not started until the valves havebeen removed. The sizer should pass easilyinto the left ventricle, as it is important not toselect an unnecessarily large valve. Approxim-ately 30 isolated Tycron sutures are placedthrough the lower portion of the sewing ring,but in the conmnissures they are placed in theupper portion to avoid extra tension and cut-ting through (Fig. 4). When all sutures aretied the inner ring and disc can be rotated andoriented so that the movement of the disc isfree. Usually the downward going portion ofthe disc is oriented toward the non-coronarysinus or the commissure between the rightand non-coronary cusp. At the end of opera-tion a negligible gradient is found over thevalve.

Anticoagulant treatment is started on thethird postoperative day.

MaterialAltogether 9I patients have been operated onfor aortic valvular disease, using the tilting

disc valve prosthesis. All patients experiencedone or more of the three cardinal symptomsof anginal pain, syncopal attacks, and dys-pnoea. There were 64 cases with calcific aorticstenosis with a gradient of more than 50 mm.Hg, with or without some degree of insuffici-ency. There were 27 cases of aortic insuffici-

FIG. 4 Diagram demonstrating the locationof isolated Tycron sutures through the valvularrim and the lower portion of the suture ring.In the commissures the sutures are placed inthe upper portion of the ring.

44 Viking Olov Bjdrk

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Aortic valve replacement with Bj6rk-Shiley tilting disc valve 45

FIG. 5 X-ray of a 6i-year-old man with combined calcific aortic stenosis and insufficiencydemonstrating the decrease in total heart size from 2200 ml. to I300 ml. in 6 months after theinsertion of a 27 mm. Bjork-Shiley aortic tilting disc valve prosthesis. The peak systolicpressure difference was iI mm. Hg at rest (cardiac output 7-7 1./min.) and 20 mm. Hg duringexercise (cardiac output I51I 1./min.).

ency, and I9 patients had concomitant pro-cedures: one patient had an ascending aorticaneurysm (Marfan's syndrome) resected andgrafted, one had an obstructive cardiomyo-pathy resected, 9 patients also had mitralvalve replacement, 7 had mitral commissur-otomy, and one patient had a ventricular sep-tal defect closed with a patch.

Results of aortic valve replacementOperative mortality In the 9I cases ofaortic valve replacement there were 8 deaths(8 8%). The fatal outcome had no direct rela-tion to the performance of the valve prosthesisin any of these cases. Six deaths were due tomyocardial failure (o, I, I, 2, 5, and 5 monthspostoperatively), and 2 patients died from sep-sis (3 weeks and 2 months postoperatively).

Complications Two cases of embolism oc-curred in connexion with the operative pro-cedure of removal of calcific aortic valves,resulting in paraplegia. One is alive and con-fined to a wheelchair, the other died in myo-cardial failure after an unsatisfactory outcomeof a concomitant mitral commissurotomy. Inone case an incisional aneurysm was detectedby aortography at the follow-up investigation7 months after operation. One case had aparavalvular insufficiency, necessitating re-operation with closure 9 months after valveimplantation.

Follow-up The remaining 83 patients arealive and well I to I7 months after operation,except one with paraplegia, mostly sitting ina wheelchair but able to walk with the aid of

two sticks. Thirty-four patients were fol-lowed for more than one year. The first 47cases have been carefully investigated withaortography, transseptal catheterization, anddetermination of the pressure difference overthe aortic prosthesis at rest and duringexercise.

Subjective improvement Of the 47 pa-tients investigated, all but 2 considered them-selves in better condition. Thirty were free ofsymptoms and in excellent condition; I5 weremuch better, but 4 of them still had continuedangina pectoris, one complained of shortnessof breath, one had an attack of dizziness, andone had a total block. The two unimprovedpatients were reoperated, one for a paravalvu-lar leakage and the other for an aneurysm inthe ascending aortic incision.

Heart size The average total heart size be-fore surgery was 1140 ml., which diminishedin 6 months to 920 mL. The correspondingrelative heart size diminished from 630 ml./m.2tO 520 ml./m.2 during the 6 months followingoperation. The most pronounced decrease inheart size was found in a 6i-year-old manwith combined calcific aortic stenosis and in-sufficiency, where the total size diminishedfrom 2200 ml. to I300 ml. in 6 months (Fig. 5).Working capacity At the follow-up inves-tigation the working capacity was:

I200 kpm./min. in 3 patients800 ,, ,, 12 ,,600 ,, ,, 9 ,,400 ,, ,, 12 ,,

less than 400 kpm./min. ,, 5



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46 Viking Olov Bjork

Regurgitation Regurgitation at the follow-up aortography was classified:

24 cases: none or minimal12 ,, slighti case: moderateI ,, severe

In the cases with slight regurgitation onaortography i or 2 sutures had cut through,causing 2-3 mm. regurgitant jet, usually inone commissure. In the case with moderateinsufficiency on aortography, this was withouthaemodynamic significance and the heart haddecreased from I030 ml. to 670 ml. in totaland from 630 ml./m.2 to 390 ml./m2. in relativesize. The case with severe insufficiency had one3 mm. and one IO mm. suture insufficiency attwo conumissures and was reoperated. Ninecases did not undergo aortography. Eight ofthem had no diastolic murmur, while onehad a slight murmur.

Pressure The systolic peak pressure differ-ence over the aortic tilting disc valves wassignificantly lower than with Starr-Edwardsand Kay-Shiley prostheses. The increase ofpressure difference during exercise is veryslight over the Bjork-Shiley tilting discvalves, especially when compared with othervalves with central occluders (see Table).

Plasma haptoglobin The average plasmahaptoglobin value was 44 mg. per cent at thefollow-up. The values of haematocrit andhaemoglobin were within normal range in allpatients except the one with a significantparavalvular leakage necessitating reopera-tion.

DiscussionThe relief of symptoms following replace-ment with the Bjork-Shiley aortic valve hasbeen very satisfactory. Most patients are ableto live normally and resume their work. Allpatients are anticoagulated.At the follow-up investigation the tilting

disc valve has been found to have a greathaemodynamic advantage over valves with acentral occluder. The peak pressure differenceat rest and during exercise is significantly lessover the Bjork-Shiley valves as compared withthe Starr-Edwards and Kay-Shiley valveprostheses (Bjork, Olin, and Astrom, I969)(Table). The advantage is most obviousin cases with a narrow aortic root, and duringexercise. Thus the average pressure increaseduring exercise over the Bjork-Shiley aorticvalve was i6 mm. Hg compared with 4I mm.Hg over the Starr-Edwards and 38 mm. Hgover the Kay-Shiley valve. The ability to with-

TABLE The average peak systolic pressuredifference over the Bjork-Shiley aortic valvecompared with values found in cases operatedupon with the Starr-Edwards and Kay-Shileyvalves in the aortic area

Valve No. of Rest Range Exercise Rangecases gradient gradient

(mm. Hg) (mm. Hg)

Bjork-Shiley 41 iI-8 0-37 i6 0-59Starr-Edwards 46 I75 0-47 4I o-85Kay-Shiley 34 27 9-6I 38 IO-Ico

stand attacks of tachycardia without fall ofblood pressure in the immediate postoperativeperiod has been observed in several patientswith the Bjork-Shiley valve.As the central laminated flow gives a smaller

systolic peak pressure gradient, the bloodtrauma is decreased compared with caseshaving prostheses ofthe central occluding type.This decreased blood trauma has resulted inan average plasma haptoglobin value of 44mg. per cent with the Bjork-Shiley valves, ap-proximately twice that found after operationwith the Starr-Edwards (i9 mg.%) and theKay-Shiley) 20 mg.%) prostheses.

ReferencesBarratt-Boyes, B. G., Roche, A. H. G., Brandt, P. W.

T., Smith, J. C., and Lowe, J. B. (I969). Aortichomograft valve replacement. A long-term follow-up of an initial series of IOI patients. Circulation,40, 763.

Bjork, V. 0. (I969). A new tilting disc valve prosthesis.Scandinavian,Journal of Thoracic and CardiovascularSurgery, 3, I.

- (I97oa). The central flow tilting disc valve pros-thesis (Bjork-Shiley) for mitral valve replacement.Scandinavian_Journal of Thoracic and CardiovascularSurgery, 4, I5.

- (197ob). A new central flow tilting disc valveprosthesis: One year's clinical experience with 103patients. Journal of Thoracic and CardiovascularSurgery, 6o, 355.

-, and Hultquist, G. (I964). Teflon and pericardialaortic valve prostheses. Journal of Thoracic andCardiovascular Surgery, 47, 693.

-, and Olin, C. (I970). A hydrodynamic com-parison between the new tilting disc aortic valveprosthesis (Bjork-Shiley) and the correspondingprostheses of Starr-Edwards, Kay-Shiley, Smeloff-Cutter and Wada-Cutter in the pulse duplicator.ScandinavianJournal of Thoracic and CardiovascularSurgery, 4, 3I.

-, -, and Astrom, H. (I969). Results of aorticvalve replacement with the Kay-Shiley disc valve.ScandinavianJournal of Thoracic and CardiovascularSurgery, 3, 93.



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