Geometric mismatch between homograft (allograft) and native aortic root:a 14-year clinical experienceq

A.C. Yankah*, H. Klose, M. Musci, H. Siniawski, R. Hetzer

Department of Cardiothoracic and Vascular Surgery, Deutsches Herzzentrum Berlin, Augustenburger Platz 1, D-13353 Berlin, Germany

Received 11 December 2000; received in revised form 22 June 2001; accepted 22 June 2001

Abstract

Objectives: We evaluated the effect of homograft/native aortic root geometric matching and mismatching on valve survival and myocar-

dial remodeling. Methods: Between January 1, 1987 and March 2000, a total of 292 patients, aged 1.5–78 years (mean, 46.2 years),

underwent freehand subcoronary aortic valve (AVR; n ¼ 207) and root (ARR; n ¼ 85) replacement with matched and mismatched cryo-

preserved homografts. All patients had pre- and postoperative two-dimensional Doppler echocardiographic studies. Two-hundred and forty-

three survivors, excluding children with complete data on sizing, were followed at a total follow-up time of 1269 patient-years. Seventy

percent received matched and 30% received mismatched aortic homografts. The homograft valve sizes ranged from 19 to 28 mm. Results:

Hospital death for elective first operation was 2.3%, and late death after a mean follow-up of 52 months was 7.9%. The patient survival at 14

years was 92 ^ 2%. By linear regression analysis, matched homografts were equal to or 1–2 mm less than the native aortic annulus

(r2 ¼ 0:73). The valve survival in patients with AVR and ARR was 72 ^ 4 and 80 ^ 8% at 14 years, respectively. The freedom from

reoperation was 92 ^ 5, 77 ^ 4 and 48 ^ 10% at 14 years for matched, oversized and undersized homografts, respectively (P ¼ 0:001). The

postoperative cardiac index of patients with 22 and 24 mm homografts was 3.8–4.1 l/m2, and there was a regression of the left ventricular

mass and end-diastolic diameter (P ¼ 0:001). Conclusions: The aortic homograft offers an excellent long-term clinical result. A mismatched

homograft is a risk factor for postoperative aortic incompetence, reinfection with pseudoaneurysmal formation and reoperation for the

freehand subcoronary implantation technique during the first 7 years of the postoperative period. It is prudent therefore to avoid mismatched

homografts and use rather a properly sized stentless xenograft if a root replacement is not indicated. q 2001 Elsevier Science B.V. All rights

reserved.

Keywords: Aortic allograft; Geometric mismatch; Ventricular remodeling

1. Introduction

It is over 38 years now since Ross and Barratt-Boyes

independently introduced the clinical use of the aortic

homograft [1,2]. Improved techniques of homograft valve

implantation, procurement, processing and cryopreservation

[3–8] mandate a renewed interest in improving the clinical

results by recognizing the importance of implanting a proper

aortic homograft size to match the geometry of the reci-

pient’s aortic root and of using a specific implantation tech-

nique.

The limited availability of aortic homografts might pose a

situation at an emergency operation to implant a

mismatched homograft valve. Early valve failure could

result, and subsequently, the enthusiasm for the excellent

clinical results of this relatively technical artistry achieved

by others [3–6,9–13] might fade away. Other factors related

to early homograft failure are immune response, especially

at a young age, and the learning phase of homograft implan-

tation [14,15].

The selection of a stentless aortic valve substitute and

accurate sizing will have an impact on early and long-

term valve performance and myocardial remodeling, as

well as bringing about an improvement in the patient’s clin-

ical and cardiac performance. The valve performance will

be disturbed by non-structural deterioration, such as cusp

rupture, leaflet prolapse or distortion, commissural displace-

ment, central and paravalvular leak (all by technical errors),

aortic root dilatation from progressive dilatation which is

not a technical error, and a progressive loss of leaflet exten-

sibility by structural deterioration [5,6,10,13].

The purpose of this report is to analyze our 14-year clin-

ical results of freehand subcoronary aortic valve replace-

ment (AVR) and aortic root replacement (ARR) with

European Journal of Cardio-thoracic Surgery 20 (2001) 835–841

1010-7940/01/$ - see front matter q 2001 Elsevier Science B.V. All rights reserved.

PII: S1010-7940(01)00885-5

www.elsevier.com/locate/ejcts

q Presented at the 14th Annual Meeting of the European Association for

Cardio-thoracic Surgery, Frankfurt, Germany, October 7–11, 2000.

* Corresponding author. Tel.: 149-30-4593-2021; fax: 149-30-4593-

2021.

E-mail address: yankah@dhzb.de (A.C. Yankah).

cryopreserved homovital homografts with particular refer-

ence to sizing and homograft/native aortic root geometrical

mismatch.

2. Materials and methods

Between 1 January 1987 and March 2000, a total of 292

patients, aged 1.5–78 years (mean, 46.2 years), underwent

subcoronary AVR (n ¼ 207) and ARR (n ¼ 85, including

25 mini-roots) with cryopreserved homovital homografts.

Twelve patients who had an intraoperative conversion to

prosthetic valve implantation were not included in this

study. Complete data on homograft sizing were available

in 243 patients. Children were excluded in the study because

of the potential risk for immune response related early tissue

deterioration.

There were 216 males and 76 females. Two-hundred and

eighteen patients had aortic incompetence, 22 had aortic

stenosis and 52 had combined lesions. One-hundred and

seventy-seven patients had active infective aortic roots

(104 native and 73 prosthetic endocarditis). Of these, 119

had ring abscesses. Of the 115 sterile roots, 15 had a history

of a previous healed endocarditis, four had homograft degen-

eration, 12 had prosthetic valve dysfunction due to valve

thrombosis and recurrent paravalvular leaks, 29 had conge-

nital bicuspid valves and one quadricuspid valve, and there

were 59 patients with rheumatic/degenerative valves. The

preoperative mean left ventricular end-diastolic diameter

(LVEDD) was between 60.0 ^ 9.9 and 63.7 ^ 12.5 mm in

patients with aortic valve incompetence and the left ventri-

cular (LV) mass was between 229.3 ^ 16.1 and 269.2 ^ 25 g

in patients with aortic stenosis, respectively.

Matched homografts were implanted in 169 (70%)

patients and were defined as an internally sized aortic homo-

graft annulus of 2 mm less than or equal to the recipient

aortic root annulus. Mismatched homografts were

implanted in 74 (30%) patients and defined as internally

sized aortic homografts 3 mm less (undersize, n ¼ 46) and

3 mm larger (oversized, n ¼ 28) than the recipient aortic

root annulus. Among the 184 survivals, 125 matched and 59

mismatched (37 undersize, 22 oversize) homografts were

selected for AVR, and 44 matched and 15 mismatched

(nine undersize, six oversize) homografts for ARR.

All of the homografts were harvested from hearts of

cardiac transplant recipients, or from hearts of multi-organ

donors if they were deemed unsuitable for heart transplanta-

tion, under sterile conditions. The donor age ranged from 12

to 56 years, with a mean age of 40.8 years.

The implanted homograft valves were obtained from our

institution-based bank in Berlin, Bio-Implant Service of

Eurotransplant in Rotterdam, the European Homograft

Bank in Brussels and the Homograft Bank in Barcelona.

The size of homografts implanted varied between 19 and

29 mm (mean, 22.5 ^ 3 mm). Hegar dilators were used to

measure the internal diameter of the homografts within 2

mm. For the selection of proper homograft size, the host

annulus size was measured preoperatively by a two-dimen-

sional echocardiographic measurement.

The intraoperative measured native annulus sizes were

compared and correlated with the preoperative measured

host annulus sizes and the selected homograft sizes.

2.1. Preoperative echocardiographic prediction of annulus

size of the homograft recipient for homograft selection

The homograft sizes selected on the basis of preoperative

echocardiographic prediction were plotted against the

intraoperative measured annulus diameter. By linear regres-

sion analysis, the matched homograft sizes were equal to or

2 mm less than the native annulus (r2 ¼ 0:73; P , 0:001).

The estimations of the preoperative echocardiographic non-

calcified annular measurements for emergency operations

correlated weakly with the intraoperative direct measure-

ments (r2 ¼ 0:45; P , 0:001). The distensibility (percen-

tage systolic/diastolic diameter change) of the annulus of

non-calcified aortic lesions was 2.5–5.8% (mean, 3.8%) as

compared with 4.5–12% (mean, 7.5%) of a normal aortic

root. Patients beyond the age of 50 years demonstrated a

distensibility of 2.5–4.5%.

ABO blood group and Human Leucocyte Antigen (HLA)

matching between homograft donors and recipients was not

practiced in all patients because of logistic reasons. Homo-

graft recipients did not receive immunosuppressive therapy.

The performance of the homografts was analyzed in 243

patients using the homograft/native aortic root geometric

annulus mismatch as a risk factor for reoperation.

2.2. Surgical technique

All of the homograft valve implantations were performed

through a median sternotomy with the aid of conventional

cardiopulmonary bypass with moderate hypothermic perfu-

sion at 30–328C, and myocardial protection with cold crys-

talloid cardioplegic arrest was achieved by maintaining the

myocardial temperature at 10–128C.

A preselected and thawed aortic homograft valved

conduit was prepared by trimming the proximal muscle to

5 mm below the valve and removing the attached anterior of

the mitral valve if it was not needed for annulus enlarge-

ment.

2.2.1. The freehand subcoronary implantation (n ¼ 207)

The homograft/native aortic root sizing was 2 mm less

than or equal to the recipient annulus internal diameter. The

implantation was carried out by two suture lines: the prox-

imal line with continuous interrupted or mattress 4-0

Prolene while the homograft conduit was held outside the

aortic root. The upper line was accomplished with each

sinus of Valsalva scalloped or leaving the non-coronary

sinus in place. The depth of the sinus scallop was deter-

mined by the distance between the coronary ostia and the

proximal line. The commissural posts of a properly sized

A.C. Yankah et al. / European Journal of Cardio-thoracic Surgery 20 (2001) 835–841836

homograft valve were fixed 1 cm above the recipient’s

commissures at the sino-tubular junction to facilitate 40–

50% leaflet coaptation. The homograft was inserted in the

natural position to restore the anatomic units of the aortic

root. In seven patients, a homograft with its anterior mitral

leaflet was used to enlarge the aortic annulus by extending

the incision into the native anterior mitral leaflet as

described by Manouguian [16] (Fig. 1).

2.2.2. ARR (n ¼ 85 including 25 mini-roots)

Homograft/native aortic root sizing was equal to or 2 mm

larger than the recipient aortic annulus internal diameter.

Total ARR was performed when there was a gross deformity

caused by endocarditis with annular abscess or aortic–

ventricular discontinuity or a congenital anomaly. All

necrotic tissues were excised and the homograft was

inserted as a free-standing cylinder or mini-root between

the LV outflow tract and the ascending aorta of the host.

The proximal suture line was performed with 4-0 Prolene by

continuous interrupted sutures at the segment of the annulus

facing each sinus. The reimplantation of the coronaries was

performed by the continuous interrupted suturing technique

described by Ross and others [3,5–7,14]. The distal homo-

graft conduit was tailored to match the geometry of the host

ascending aorta using continuous interrupted sutures. In the

mini-root technique, the homograft root was then loosely

wrapped with the host ascending to avoid crimping of the

aortic root and subsequent valve incompetence.

Additional cardiovascular surgical procedures were:

replacement of the ascending aorta (n ¼ 12), coronary

artery bypass surgery (n ¼ 13), mitral valve replacement

(n ¼ 8) or reconstruction (29), and tricuspid valve recon-

struction (n ¼ 4).

2.3. Follow-up patients and protocol

Follow-up patients were reviewed periodically either by

DHZB cardiologists or by the patient’s own cardiologist,

initially at 1, 3 and 6 months after homograft valve replace-

ment and at yearly intervals thereafter. At each visit, in

addition to the clinical assessment, chest X-rays, electrocar-

diograms and echocardiograms were obtained and analyzed.

Homograft valve regurgitation was described by color

Doppler echocardiography and categorized as follows:

grade 0 as no aortic insufficiency, grade I as mild, grade II

as moderate and grade III as severe [17].

Follow-up was complete at reoperation and removal of

the homograft valve, death with the homograft valve in

place or at the last follow-up in survivors with their homo-

graft valves in place.

Follow-up information was available for evaluation in

94% of patients. The maximum follow-up was 14 years

and 2 months, and the mean was 52 months. At the latest

postoperative evaluation, 81% of the patients were in New

York Heart Association (NYHA) class I and 19% in class II

clinically.

2.4. Data analysis

Patient survival and valve failure were analyzed with

Kaplan–Meier curves, and the probability and standard

A.C. Yankah et al. / European Journal of Cardio-thoracic Surgery 20 (2001) 835–841 837

Fig. 1. Aortic annulus enlargement with extended incision into the native anterior mitral valve leaflet using a valved homograft with anterior mitral valve

leaflet.

error were calculated. Continuous data were presented as

means ^ standard deviation (SD). Variables relating to the

recipient, including age, sex, underlying aortic root pathol-

ogy, homograft/patient aortic root annulus size and implan-

tation technique, were analyzed using the Cox proportional

hazards model. Linear regression techniques were applied to

establish the relationship between host and homograft annu-

lar size.

The log-rank test was used to identify statistical signifi-

cance as an endpoint analysis. Implantation of mismatched

homografts and reoperation for homograft explantation, and

patient survival in relation to a variable period of homograft

operation (1987–1993, and 1994–2000) were included in

the analysis.

At the echocardiographic studies, both M-mode record-

ings and off-line measurements were guided by the two-

dimensional image. The ejection fraction was calculated

according to Teichholz et al. [18] and the LV mass by

means of the cube formula. Blood flow velocity in the LV

outflow tract was estimated by pulsed wave Doppler from an

apical four-chamber view (sample size of 5 mm). Pressure

gradients were calculated according to the simplified

Bernoulli equation (Doppler pressure gradient ¼ 4 £ (peak

velocity)2). The mean gradients were calculated from off-

line planimetry of the continuous wave Doppler recordings

[17–19].

Analysis of variance (ANOVA) was used to compare the

differences between the three different valve sizes (match,

undersize and oversize) and the pre- and postoperative

values of LV mass and LVEDD. The results are presented

with 95% confidence intervals (CI).

Homograft valve failure was diagnosed when there was an

onset of postoperative evidence of clinically mild, moderate

or severe valve stenosis or incompetence with or without

conduit calcification. The time of censoring for significant

valve stenosis or incompetence, or dysfunction due to struc-

tural or non-structural deterioration was the date of reopera-

tion and homograft explantation, late death from the causes

above, or the last follow-up for the remaining survivors.

3. Results

3.1. Patient survival

The hospital mortality for an elective first operation was

2.3%. Late death was 7.9% after a mean follow-up of 52

months.

On survival analysis, 92% of the hospital survivors are

alive at 10 and 14 years after homograft valve replacement,

respectively (Fig. 2). Mismatched homograft was not a risk

factor for death in both periods of operation (risk ratio, 0.35;

95% CI, 0.10–1.23; P ¼ 0:17).

3.2. Reoperation and valve survival

Homografts were explanted in 48 patients during the 14-

year follow-up at a mean time interval of 2.5 years after

implantation (Table 1). Forty-one (85.5%) patients received

the freehand subcoronary implantation technique and seven

(14.5%) had the root replacement technique. The age of

these patients at the first homograft operation was 40.1

years (SD, ^19.7 years). Of the 48 (20%) reoperations,

eight (seven AVR, one ARR) were due to persistent infec-

tion (3% of endocarditis patients) with pseudoaneurysmal

formation or reinfection (1% of endocarditis patients).

The freedom from explantation of the homografts in

patients with ARR at 13 years is 80%, and 72% in the free-

hand AVR patients at 14 years, respectively (Fig. 3). The

freedom from homograft explantation at 7years was 88%.

The risk for reoperation was twice as high in the second

operation period (risk ratio, 2.05; 95% CI, 1.07–3.90;

P ¼ 0:028), while in the two operation periods, the use of

matched and mismatched homograft valves was signifi-

cantly different (P ¼ 0:003).

3.3. Homograft/native aortic root mismatch

The probability of homograft valve survival for

geometric oversized homografts was 92 ^ 6%, 77 ^ 4%

for matched homografts and 48 ^ 10% for undersized

homografts at 13 years (P ¼ 0:001; Fig. 4; Table 1). The

P value for the log-rank test adjusted for the two periods of

A.C. Yankah et al. / European Journal of Cardio-thoracic Surgery 20 (2001) 835–841838

Fig. 2. Actuarial (Kaplan–Meier) patient survival excluding hospital death

for both implantation techniques during the 14-year follow-up.

Table 1

Determinants of homograft reoperation

Covariates Risk ratio 95% CI P value

Sex 1.922 0.803–4.601 0.14

Age .30 years 0.9907 0.9575–1.025 0.59

Undersize 2.975 1.432–6.184 0.001

Oversize 0.361 0.081–1.599 0.16

Match 0.587 0.297–1.161 0.12

Freehand AVR 2.033 0.85–4.858 0.11

ARR 0.492 0.206–1.176 0.11

Aortic ring abscess 1.318 0.671–2.588 0.42

homograft operation (1987–1993 and 1994–2000) was

0.003.

Twenty-four patients with the freehand subcoronary

implant were reoperated on due to mismatched (22 under-

sized, two oversized) homografts. Thirteen developed aortic

incompetence grade III (three leaflet prolapses, ten central

leaks), and there were 11 patients with incompetence grade

II and a mean gradient of more than 5 mmHg (three cusp

ruptures, three paravalvular and seven central leaks).

Dysfunctions of matched homografts encountered in the

freehand technique group were due to valves inserted in a

native root with a geometric disparity between the annulus,

sinus of Valsalva and the sino-tubular junction and distorted

infected native annulus. Among the ten patients who

received mismatched homografts (eight undersized, two

oversized) for root replacement with the mini-root techni-

que, two developed a mean transvalvular gradient of over 5

mmHg and eight others below 5 mmHg. One patient devel-

oped recurrent endocarditis. The geometric disparity

between the homograft and the native root was at subannu-

lar, annular and sino-tubular levels.

3.4. Matched homografts

The valve performance was excellent in 155 (91.7%)

patients. Fourteen (8.3%) patients, including patients with

acute aortic root endocarditis and abscesses and a Marfan

patient, developed valve dysfunction due to paravalvular

(n ¼ 2) and central leaks (n ¼ 12, including five with the

mini-root technique) because of technical reasons. One

patient developed homograft endocarditis with valve incom-

petence. The freedom from valve explantation for all causes

was 77 ^ 4% at 10 and 14 years (Fig. 4).

3.5. Correlation between homograft size and patient body

surface area

Hemodynamically, there was no disparity between the

patient’s body surface area and the cardiac output for the

selected homograft size. For the 22 mm homograft valves,

the mean cardiac index measured postoperatively was

4.09 ^ 0.5 (95% CI of 3.62 and 4.55 l/m2), and for a 24

mm valve, the mean cardiac index was 3.8 ^ 0.4 (95% CI of

3.40 and 4.2 l/m2). Two patients with a mini-root technique

and an undersized homograft demonstrated cardiac indices

of 2.7 l/m2.

3.6. Left ventricular remodeling

The postoperative LV remodeling was achieved by

reduction of the LV mass (g) for aortic stenosis and the

LVEDD (mm) for aortic incompetence. Over a period of

6–60 months, the LV mass reduced by 12–15% and the

LVEDD by 10–12%. The aortic annulus diameter of

patients, particularly with annuli greater than 27 mm,

remained stable without calcification and progressive dila-

tation.

3.7. Thromboembolism

Our patients were treated with aspirin for 3 months after

surgery and have not been complaining of symptoms related

to thromboembolic complications, either in the early or late

postoperative follow-up periods.

4. Discussion

The anatomic units of the aortic homograft are distensible

by 8–12% and will result in the radial movement of the

commissures outward, even if the aortic annulus is fixed

and inexpansible. In a normal non-calcified aortic root, a

16% change in the aortic root radius would allow the leaflet

edges to straighten in the systole and form a triangular

orifice [15,20].

Accurate matching of a homograft to the host aortic root

either equal to or 2 mm less than the host annulus at subcor-

onary implantation will therefore provide over 50% leaflet

coaptation and excellent long-term clinical and hemody-

namic performance which is identical to that of ARR [4–

6,9,11,21].

The less distensible stentless xenografts, which appear to

be complimentary, rather than a competitive valve substi-

tute to the homograft, require oversizing by 2–3 mm to

A.C. Yankah et al. / European Journal of Cardio-thoracic Surgery 20 (2001) 835–841 839

Fig. 4. Actuarial (Kaplan–Meier) freedom from explantation of homograft/

native aortic root geometric matched, oversized and undersized valves.

Fig. 3. Actuarial (Kaplan–Meier) freedom from homograft valve explanta-

tion after freehand subcoronary and root replacement.

allow proper matching to a distensible native aortic root in

order to maintain over 50% leaflet coaptation.

Besides patients’ special wishes and a contraindication

for long-term anticoagulation, the principal indication for

ARR in our series was acute endocarditis with burrowing

ring abscess. Sepsis and NYHA functional classes III and IV

were major risk factors for early death in this group of

patients.

Twenty-seven (56.3%) homograft early and late failures

in our series were associated with geometric mismatching,

and of the matched homografts, 14 (29.2%) failures were

technical and seven (14.5%) were due to infection. In our

series, cryopreserved homovital homograft valve explanta-

tion occurred frequently in the first 7 postoperative years

due to structural deterioration in most patients with

mismatched homografts. However, the valve performance

of matched and oversized homografts remained stable after

2 and 5 years until 14 years postoperatively, respectively

(Fig. 4; P ¼ 0:001). Similar clinical results have been

reported by others [4,6,11].

In small aortic roots or in subvalvular obstructive lesions,

it seems prudent to enlarge the aortic root to accommodate a

larger aortic homograft. The aortotomy is made through the

commissure between the left and non-coronary sinus into the

posterior interleaflet triangle. The incision may end at the

edge of the anterior leaflet of the mitral valve. When there

is no adequate native annulus size or there is a subvalvular

obstructive lesion, the incision is extended into the anterior

mitral leaflet and onto the roof of the left atrium [16,21]. The

attached anterior mitral leaflet of the homograft is used to fill

the opening of the native anterior mitral leaflet, thereby enlar-

ging the LV outflow (Fig. 1). The homograft may be used in

certain cases of double valve replacement and repair (AVR

and anterior mitral valve repair) in order to avoid the need for

anticoagulation therapy.

Annulus enlargement for a root replacement using an

oversized homograft with the anterior mitral leaflet poses

no risk for postoperative valve incompetence, unless there is

homograft ring distortion or a geometric mismatch between

the native annulus and the homograft.

Although a root replacement technique offers 100% valve

competence, homograft ring distortion at implantation in a

necrotic region may cause valve incompetence as well

[5,14].

Tailoring or reduction annuloplasty for root replacement

might be beneficial, but not for the freehand subcoronary

implantation technique because of the limited technical

possibility to tailor all the three anatomic units of the aortic

root.

Homograft valve dysfunction is associated with multilevel

geometric disparity at the subannular, annular, sinus and

sino-tubular level. Subsequently, non-structural valve fail-

ure, such as cusp rupture, leaflet prolapse or distortion, para-

valvular leak pseudoaneurysmal formation and commissural

displacement, resulting in a central leak, occurred. An

ongoing loss of leaflet flexibility and expansibility, such as

structural deterioration, may be associated with an under-

sized valve, as could be demonstrated, particularly in adult

patients.

In most patients, despite homograft/native root geometric

mismatch, there was no mismatch between the cardiac

output and the patient’s surface area as demonstrated in

the postoperative measurements of the cardiac indices.

Like other reports, a regression of LV hypertrophy and

LVEDD could be achieved over a period of 6–60 months

[12,13,22–24]. Reduction of LV hypertrophy, LVEDD and

improvement of the ventricular performance underscore the

hemodynamic superiority of a non-obstructive stentless

bioprostheses over a stented bioprostheses of the same

size [25]. It is possible therefore to have a relatively small

homograft valve (up to 3 mm smaller) without a demon-

strable gradient. The gradient to valve area was not studied

in this series. Rahimtoola, however, underlines that the rela-

tionship of the gradient to valve area is curvilinear, and once

the effective orifice size of the aortic valve is critically

reduced to less than 35% of normal, the gradient rises preci-

pitously [24,25]. We encountered this in two patients with

mini-root and 13 patients with subcoronary implantations.

The multivariate analysis identified undersized homografts

as a risk factor for developing aortic valve incompetence,

early and late recurrent endocarditis in the freehand subcor-

onary implantation technique. Due to standardization of the

homograft sizing technique at the beginning of homograft

implantation at our institution, the use of mismatched homo-

grafts was not specifically associated with surgical inexperi-

ence or a particular period of implantation, but rather with

availability. Mismatched homografts were rather frequently

used at emergency operations for complicated acute infec-

tive endocarditis, and the number of implanted matched and

mismatched homografts was evenly distributed in the two

operation periods (1987–1993 and 1994–2000). The P value

of reoperation for explantation of mismatched homografts

for the log-rank test adjusted for both implantation periods

was 0.003. The use of mismatched homografts, therefore,

was not associated with surgical inexperience, but rather,

with the availability of proper homograft sizes at the time of

emergency operations in both operation periods. Although

the risk for reoperation was twice as high in the second

operation period (risk ratio, 2.05; 95% CI, 1.07–3.90;

P ¼ 0:028), it was demonstrated that mismatched homo-

grafts did not have an adverse effect on patient survival,

and therefore were not a risk factor for death for both opera-

tion periods (risk ratio, 0.35; 95% CI, 0.10–1.23; P ¼ 0:17).

The durability of the homografts achieved with both

implantation techniques therefore was influenced by sizing

and the implantation technique as demonstrated in the valve

survival analysis in Fig. 3 and by others [6,9,11,12,14,21].

However, a mini-root technique should not be used as a stan-

dard root replacement technique because of its potential to

develop valve incompetence from crimping the homograft

following wrapping with the native aortic root. Furthermore,

it can complicate root fibrosis with subsequent late calcifica-

A.C. Yankah et al. / European Journal of Cardio-thoracic Surgery 20 (2001) 835–841840

tion as well as coronary ostial stenosis leading to reoperation.

The technique can, however, be beneficial for local root

hemostasis, and therefore can be used in selected groups of

patients and as a rescue procedure to save patients from cata-

strophic bleeding and prolonged operation times.

5. Conclusions

The identical excellent long-term hemodynamic perfor-

mance of cryopreserved homograft valves used for AVR

and ARR techniques is associated with proper sizing and

meticulous implantation techniques.

Geometric mismatch between the native and homograft

root was not a risk factor for postoperative death, but it was

a risk factor for postoperative aortic incompetence, reinfec-

tion with pseudoaneurysmal formation and reoperation in

patients with a freehand subcoronary implantation techni-

que and a common hazard for the mini-root implantation

technique in the first 7 years after operation. The use of

mismatched homografts was not associated with surgical

inexperience, but rather, was associated with the availability

of the proper homograft size at the time of emergency

operations. In a situation where there is only a mismatched

homograft available, it seems therefore prudent to choose a

stentless xenograft as an alternative biological valve substi-

tute, which is readily available in all sizes, to restore the

anatomic and functional units of the patient’s aortic root and

to achieve a competent valve.

Acknowledgements

The authors wish to thank Mrs Stein for her statistical

assistance.

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