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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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