- Email: [email protected]
Hemodynamic evaluation of the Ionescu-Shiley pericardial xenograft in the mitral position
Experimental
and laboratory
reports
Hemodynamic evaluation of the lonescu-Shiley pericardial xenograft in the mitral position
Anand P. Tandon, M.D., M.R.C.P. Donald R. Smith, M.D., F.R.C.P. Marian I. Ionescu, M.D., F.A.C.S. Leeds,
England
Glutaraldehyde treated pericardial xenografts have been used for heart valve replacement during the past 6 years.’ Clinical results have been extremely gratifying. Very low thrombogenicity without anticoagulant therapy is one of the important benefits of this type of valve replacement. This report presents the results of a late hemodynamic evaluation of 27 patients and of sequential studies of six patients who had mitral valve replacement with the Ionescu-Shiley pericardial xenograft. * Patients
and methods
Since March, 1971, 106 patients had mitral valve replacement with pericardial xenografts. Actuarial survival and event free curves are shown in Fig. 1. Four embolic episodes were noted in the entire series. All were mild or trivial, occurred within the first 6 weeks following valve replacement and left no sequelae. Clinically 94 per cent of patients were in Grade I (NYHA) at the latest assessment. Twenty-seven patients underwent hemodynamic evaluation at a mean duration of 40.3 +- 2.8 (range 24 to 59) months following valve insertion. The criteria for selection were an interval of at least two years from valve replacement and the informed consent of the patient. From the Departments of Cardiology General Infirmary, Leeds, England. Received
for publication
Jan.
Accepted
for publication
Mar.
Reprint Surgery,
requests: M. I. Ionescu, The General Infirmary,
‘ShiIey
Laboratories,
Irvine,
0002~8703/78/0595-0595$00.70/O
and Cardiothoracic
Surgery,
The
19, 1977. 16, 1977. M.D., Department Leeds, LSl 3EX,
of Cardiothoracic England.
California.
The annulus diameter of the grafts used was 25 mm. in two patients, 27 mm. in 15 patients, and 29 mm. in 10 patients. The clinical details of these patients are shown in Table I. Six patients had, in addition to the preoperative investigation, two separate hemodynamic ‘studies performed at mean intervals of 11.2 (f 1.6) and 42.8 (+ 3.3) months following pericardial xenograft implantation. Of the 20 patients who had preoperative cardiac catheterization, 10 had resting pulmonary artery systolic pressure greater than 60 mm. Hg. All patients were hospitalized 24 hours prior to hemodynamic study. On admission, a detailed clinical history, estimation of functional capability, physical examination, hematological assessment, a chest radiograph, a 1Zlead electrocardiogram and a phonocardiogram were obtained in all patients. Electrocardiograms and chest radiographs were analyzed for rhythm, left ventricular voltage (using the sum of SV, and RV,), and cardiothoracic ratio. Right and left heart catheterization was performed in the postabsorptive state without any prior sedation. Pulmonary and systemic pressures were transduced by strain gauge manometers @EM* 486) with the zero level set 5 cm. below the sternal angle, integrated electronically and recorded on a multi-channel ultraviolet light recorder (SEM’ 3012). Cardiac output was measured by the direct Fick method using 2 minutes of gas collection. Hemodynamic data were obtained during a 4-minute period of rest and between the fourth and sixth minute of a 6-minute period of supine leg exercise on a bicycle *Sheilds
6 1978
The
C. V. Mosby
Co.
and
Epstein
Monitoring,
Middlesex,
U.K.
American Heart Journal
595
Tandon,
Smith,
and
Ionescu
I%
MTRAL
REPLACEMENT Q4.E2.6% Q4.7*2.6% 82.1 t4.9%
90
,--"..
66.6 * 7.0%
free 3 mths. 60
(SS)
cerebral hcwt
1
abscess b&m
(451
I581
0 0
S.B.E S.B.E.
2
3
S.&E. t.embdLiun
(IS1
(333
4
trm
--. ..-’
(81
5
Ib.cdpatima
(2)
6
7
YEhR6
Fig. 1. Actuarial analysis of results following mitral pericardial xenograft valve replacement. expressed as per cent expected survival rate and individual event free curves for complications.
Table
I. Preoperative clinical details Number of patients
Male Female Age Mean Range Clbiical lesion stenosiB
Incompetence Mixed Rhythm Atria1 fibrillation Sinus rhythm Functional status (NYHA) II III IV Previous closed mitral valvotomy
8 19 43.6 yrs (k1.8) 19-62 yrs 9 6 12 19 8 6 19 2 12
ergometer. Left ventricular angiograms were performed in all patients at the end of the study. Pulmonary vascular resistance was calculated using the standard formula. The mean diastolic gradient across the pericardial xenograft was measured by planimetric integration of at least five simultaneously recorded phasic left ventricular and pulmonary wedge tracings. The xeno-
5616
The data are
graft surface area was calculated according to the hydraulic formula of Gorlin and Gorlin.’ Results Electrocardiographic
and radibgical
changes.
The mean cardiothoracic ratio showed a significant decrease from a preoperative level of 0.59 to 0.54 at the postoperative study (p < 0.001). The mean left ventricular voltage was 34.8 mm. preoperatively and 33.8 mm. at the postoperative study. This difference was not statistically significant. Hemodynamic findings at rsst. The results are given in Tables II and III. The mean cardiac index showed a significant increase from a preoperative level of 1.9 L./min./ M.* to 2.6 L./min./M.2 at the postoperative study (p < 0.001). The oxygen uptake also showed a smaller, but still significant rise (p < 0.05). The mean pulmonary artery and wedge pressures were significantly reduced at the postoperative study (p < 0.091), with a corresponding reduction in mean pulmonary vascular resistance (p < 0.01). Postoperatively, the mean diastolic gradient across the xenograft was 6.4 ( t 0.5) mm. Hg and the calculated xenograft surface area was 2.0 (& 0.1) cm.2 The results obtained in 10 patients with severe preoperative pulmonary hypertension are presented in Table III. This group of patients showed reductions in mean pulmonary artery and wedge pressures and in pulmonary
May, 1978, Vol. 95, No. 5
Hemodynamics
of mitral
pericardial
xenografts
II. Pre- and postoperative hemodynamic data (Mean values & SEM) of 27 patients with pericardial xenografts in the mitral position
Table
0, uptake (ml./min./M2) R Preop postop p value
123.7 f 6.0 136.3 zk4.0 to.05
E 314.6 + 40.4 406.5 t 14.4 to.05
Cardiac index (L.lmin.1M.Z)
PWP (mm. f&9
R
E
1.9 kO.1 2.6 kO.1 to.001
3.0 f 0.3 4.1 kO.2 to.01
PAP (mm. W E
R 23.3 f 1.9 13.8 k 0.8 <0.001
40.4 f 2.7 29.4 k1.5
Abbreviations: SEM = standard error of the mean; PWP = mean PVR = pulmonary vascular resistance; R = rest; E = exercise.
R
Mean diastolic gradient (mm. f-k)
PVR (dynes sec. cm:” M.?) E
38.7 k4.1 22.8 -+ 1.0 to.001
57.1 f 4.9 42.0 f 1.9 to.01
pulmonary
wedge
R
E
535.6 f 113.3 285.0 k 20.7 to.01 pressure;
656.8 k241.1 260.3 k 26.3 to.05 PAP = mean
Calculated xenograft surface area (cm?)
R
E
R
E
6.4 co.5
15.3 r0.9
2.0 kO.1
2.3 kO.1
pulmonary
artery
pressure;
Ill. Hemodynamic data in 10 patients with preoperative resting pulmonary systolic pressure > 60 mm. Hg (Mean values k SEM) Table
0, uptake (ml./min./M.2) R FhOp*
112.6 f 5.9 137.7 k7.7 -CO.05
Postop
p value
Cardiac index (L./min./M.2) E
308.5 f 50.1 392.6 + 19.3 -co.05
R
E
1.9 -+ 0.2 2.7 k 0.2 (0.01
2.8 *0.5 4.3 f 0.3 to.01
*Preoperative exercise studies available in six patients only.Abbreviations: SEM = standard error of the mean; PWP = mean PVR = pulmonary vascular resistance; R = rest; E = exercise
vascular resistance comparable to those found in patients with a lesser degree of pulmonary hypertension. Thus, in this series, the severity of preexisting pulmonary hypertension did not seem to influence the postoperative hemodynamic improvement. Hemddynamic findings on exercise. The cardiac index increased significantly from a preoperative level of 3.0 L./min./M.’ to 4.1 L./min./M.Z postoperatively (p < 0.01). For each milliliter increase in oxygen uptake, the cardiac index rose 5.6 ml. The mean pulmonary artery and wedge pressures showed significant reduction (p c 0.01) from the preoperative values but were still abnormally elevated. The pulmonary vascular resistance also showed significant reduction from the preoperative level (p < 0.05). Those patients with severe pulmonary hypertension preoperatively showed a similar improvement in
American
Heart
Journal
PWP (mm. f&J
PAP (mm. Hgl
R
E
27.7 2 2.9 15.6 + 1.2
44.5 + 2.2 29.8 f 2.7 to.01
pulmonary
wedge
R 50.4 k6.2 25.2 k1.8 to.001
pressure;
PVR (dynes sec. cm:’ M.?) E
66.3 * 5.9 44 2 3.9 to.01
PAP = mean
R
E
599.8 + 163.7 294.5 k30.7 to.01
pulmonary
834 f 239.8 288.9 k 55.2
pressure;
cardiac output, pulmonary pressures, and vascular resistance. Mean diastolic gradient increased from a resting value of 6.4 mm. Hg to 15.3 mm. Hg on exercise. The calculated surface area showed an increase with exercise to 2.3 cm.? Sequential studies. One preoperative and two separate postoperative studies were performed in six patients. These hemodynamic investigations were carried out under identical physiological conditions and the results are presented graphically in Figs. 2 and 3. At the first postoperative study the cardiac index, mean pulmonary artery and wedge pressures, and pulmonary vascular resistance showed a significant improvement, both at rest and on exercise, when compared with the preoperative data. The improvement was similar to that obtained in the entire group of patients as described in the previous paragraphs.
597
Tandon,
Smith,
__
and
Ionescu
I- S MITRAL
PERICARDIAL
XENOGRAFT
SEQMNTIAL
HAEMODYNAMIC
DATA AT REST L./min./sq.m.
ml./minhq.m.
,/*
i
P>O.l
P>O.5
1
II co.os
0i
P>O.7
dm
mm. Hg.
sac cri?iq.m.
40
l PRE-OP n Fig.
2. Sequential
‘1st. POST-OP
= 6 (valve size hemodynamic
27:
(llmtha)
‘2nd. POST-OP
(43mths.)
MEAN? S.E.M.
four patients. 29:two patients.) data
at rest
from
six patients
with
mitral
pericardial
xenograft.
PWP = mean pulmonary wedge pressure; 0, Uptake = oxygen uptake; Mean PAP = mean pulmonary pressure; Pulm. Vast. Resistance = pulmonary vascular resistance; SEM = standard error of the mean.
There were no significant changes in cardiac index, pulmonary artery and wedge pressures, and pulmonary vascular resistance between the first and the second postoperative study. The mean diastolic gradient across the xenografts. were 7.1 mm. Hg at rest and 20.1 mm. Hg on exercise at the first, and 6.6 mm. Hg and 19.1 mm. Hg at the second postoperative study. This difference was not significant. The calculated xenograft areas were 2.2 cm.2 at rest and 2.6 cm.2 on exercise at the first postoperative study. A marginal increase to 2.3 and 2.7 cm.2, respectively, was noted at the second postoperative study, but again the difference was not significant. Left ventricular angiography. Left ventricular angiograms demonstrated competent pericardial xenografts in all patients. Discussion
The pericardial xenograft was primarily created to minimize the rate of thromboembolism
598
Mean artery
traditionally associated with prosthetic replacement of the mitral valve. The experience during the past 6 years has demonstrated that, even without the use of anticoagulants, this aim has been attained.l The structural integrity of the xenograft has been maintained, as shown by six years of clinical follow-up and by over seven years of fatigue testing in vitro. The results of this study demonstrated that mitral valve replacement with pericardial xenografts produced significant hemodynamic improvement, and that this improvement was maintained for periods of up to 59 months following valve insertion. The study also confirmed the previously reported reversibility of pulmonary hypertension following mitral valve replacement.“-” The results showed that, although a postoperative increase in cardiac output and in oxygen uptake was demonstrated both at rest and during exercise, the hemodynamic response to exercise
May, 1978, Vol. 95, No. 5
Hemodynamics
r
-
I-S
MITRAL
PERKMDIAL
of mitral
pericardial
nenografts
XENOGRAFT
SEQUENTIAL HAEMOOYNAMC
DATA ON EXERCISE
PW.7
*WE-OP n=6(Vak
Fig. 3. Sequential hemodynamic tions as in Fig. 2.
l lst. POST-OP(llmthd Site
27:fWr
patientS.29:
data
on exercise
l 2nd two
from
was still impaired. Postoperatively, the mean pulmonary artery and wedge pressures approached normal figures at rest but rose to abnormal levels with exercise. This seems to be a universal finding with all types of mitral valve replacement,3. ‘-16 and it may be related to the fact that all valve substitutes inserted in the mitral position produce some degree of obstruction to forward flow, especially during exercise. The mean diastolic gradient across the mitral pericardial xenograft of 6.4 mm. Hg compares favorably with gradients obtained with other mitral valve substitutesJ. 8.II-l4 Published results of postoperative hemodynamic evaluations of other currently used mitral valve replacements are given in Table IV. These data provide only a perspective against which the results of the present study can be considered. Direct comparison between results obtained with various valve substitutes is difficult due to the differences in the methods of study and the diversity of patient population. Furthermore, only scanty reports of “late” hemodynamic eval-
American
Heart
Journal
POST-OP
(43mths.I
MEAN? S.E.M.
Pat&MS.)
six patients
with
mitral
pericardial
xenograft.
Abbrevia-
uations are available, the majority of these having been performed at less than 18 months postoperatively as compared with 40 months in the present study. Nevertheless, the data presented in Table IV show that hemodynamitally the pericardial xenograft compares favorably with other types of valve substitute used in the mitral position. Although the number of patients with sequential hemodynamic investigations was small, the results are of considerable importance. They established that maximum circulatory improvement was obtained by the end of the first year following valve insertion and that the functional integrity of the xenograft was maintained intact with the passage of time. Similar results were obtained from investigations performed on patients with pericardial xenografts in the aortic position.” In conclusion, this study has demonstrated significant hemodynamic improvement following mitral valve replacement with the Ionescu-Shiley pericardial xenograft and maintenance of valve
599
Tandon,
Smith,
end
Ionescu
IV. Hemodynamic results following mitral valve replacement with different types of valve substitutes
Table
Authors Pietras
et al3 (1974)
Haerten Bjork
et al* (1976) et al”
Haerten Sigwart Johnson Lurie et Present
(1974)
et aI8 (1976) et alI2 (1976) et alI3 (1975) al” (1976) study
Mitral
valve substitute
Time of study (months POStoP)
Starr-Edwards valve, Model 6309 Starr-Edwards valve, Model 6300 Bjork-Shiley valve50’ angle 69” angle Lillehei-Kaster valve Lillehei-Kaster valve Hancock porcine xenograft Hancock porcine xenograft I-S pericardial xenograft
*Mean period not available. tCardiac output. Abbreviations: PWP = pulmonary
wedge pressure;
Mean PWP (mm. Hgl
R
E
R
16.3
3.2
4.8
13.2
12
2.0
3.4
5-13* 5-13*
4.6.f 4.4t 2.0 3.0 2.6 2.5 2.6
7.4t 7.9t 3.4
l-6* 5.5 1-15 40.3
*
4.1
E
Mean diastolic gradient (mm. f&d R
E
30
11.6
24.5
14
26
7.2
16.7 16.9 14 16 17 15 13.8
30.4 25.8 29
4.3 4.7 6.2 9 6.5 8 6.4
29.4
11.7 8.4
15.3
R = rest; E = exert
function up to 59 months postoperatively. Repeat circulatory investigations will be performed at longer intervals in order to continually appraise the function of this valve. Summary
Hemodynamic studies were performed in 27 patients at a mean interval of 40.3 (range 24 to 59) months following mitral valve replacement with pericardial xenografts. Six patients had sequential studies, one before operation and two separate investigations at mean intervals of 11.2 and 42.8 months following valve replacement. The results showed significant increase in cardiac index, reduction in mean pulmonary artery and wedge pressures, and decrease in pulmonary vascular resistance both at rest and during exercise, when compared with the preoperative values. The mean diastolic gradient across the pericardial xenografts was 6.4 mm. Hg at rest and 15.3 mm. Hg during exercise. The calculated xenograft surface area was 2.0 and 2.3 cm.2, respectively. The sequential studies established that the maximum hemodynamic improvement was achieved within the first year following valve replacement and that the functional performance of the xenografts was maintained, unaltered, with the passage of time.
600
Cardiac index (L./min./M.z)
We wish to thank Miss Anne preparation of thii manuscript.
E. Tunnicliffe
for help in the
REFERENCES 1.
2.
3.
4.
5.
6.
7.
8.
Ionescu, M. I., Tandon, A. P., Mary, D. A. S., and Abid, A.: Heart valve replacement with the Ionescu-Shiley pericardial xenograft, J. Thorac. Cardiovasc. Surg. 73:31, 1977. Gorlin, R., and Gorlin, S. G.: Hydraulic formula for calculation of the area of the stenotic mitral valve, other cardiac valves and central circulatory shunts, AM. HEART J. 41 :l, 1951. Pietras, R. J., Long, D. M., and Rosen, K. M.: Late postoperative clinical and hemodynamic assessment of the earIy cloth-covered Starr-Edwards mitral valve prosthesis, J. Thorac. Cardiovasc. Surg. 67:456, 1974. Dalen, J. E., Matloff, J. M., Evans, G. L., Hoppin, F. G., Jr., Bhardwaj, P., Harken, D. E., and Dexter, L.: Early reduction of pulmonary vascular resistance after mitral valve replacement, N. Engl. J. Med. 277387, 1972. Zener, J. C., Hancock, E. W., Shumway, N. E., and Harrison, D. C.: Regression of extreme pulmonary hypertension after mitral valve surgery, Am. J. Cardiol. 30:820, 1972. Kaul, T. K., Bain, W. H., Jones, J. V., Lorimer, A. R., Thomson, R. M., Turner, M. A., and Escarous, A.: Mitral valve replacement in the presence of severe pulmonary hypertension, Thorax 3 1:332, 1976. Russell, T., II, Kremkau, E. L., Kloster, F., and Starr, A.: Late hemodynamic function of cloth-covered StarrEdwards valve prostheses, Circulation 45: and 46 (Suppl. 1):8, 1972. Haerten, K., Both, A., Loogen, F., and Bricks, W.: Hemodynamics after mitral valve replacement with Starr-Edwards, Bjork-Shiley and Lillehei-Kaster prostheses (Abstr.), Circulation 53 and 54 (Suppl. II):lSl, 1976.
May, 1978, Vol. 95, No. 5
Hemodynamics
9.
10.
11.
12.
13.
Reid, J. R., Stevens, T. W., Segwast, W., Fulweber, R. C., and Alexander, J. L.: Hemodynamic evaluation of the Beall mitral valve prosthesis, Circulation 45(Suppl. I):l, 1972. Fernandez, J., Morse, D., Spagna, P., Lemole, G., Gooch, A., Yang, S. S., and Maranhao, B.: Results of mitral valve replacement with the Beall prosthesis in 209 patients, J. Thorac. Cardiovasc. Surg. 71:218, 1976. Bjork, V. O., Book K., and Holmgren, A.: The BjorkShiley mitral valve prosthesis, Ann. Thorac. Surg. l&379, 1974. S&wart, U., Schmidt, H., Gleichmann, U., and Borst, H. G.: In vivo evaluation of the Lillehei-Kaster heart valve prosthesis, Ann. Thorac. Surg. 22:213, 1976. Johnson, A. D., Daily, P. O., Peterson, K. L., LeWinter, M., DiDonna, G. J., Blair, G., and Niwayama, G.: Functional evaluation of the porcine heterograft in the mitral position, Circulation 52(Suppl. 1):40, 1975.
American
Heart
Journal
14.
15.
16.
17.
of mitral
pericardial
xenografts
Lurie, A. J., Miller, R. R., Maxwell, K., Vismara, L. A., Hurley, E. J., and Mason, D. T.: Postoperative hemodynamic assessment of the glutaraldehyde-preserved porcine heterograft in the aortic and mitral positions (Abstr.), Cir&lation 53 and 54 (Suppl. II):148, 1976. Book, K.: Mitral valve renlacement with Biork-Shilev tilting disc valve-A clinical and hemodynam”ic study in patients with isolated mitral valve lesions, Stand. J. Thorac. Cardiovasc. Surg. Suppl. 12:2, 1974. Hultgren, H., Hubis, H., and Shumway, N. E.: Cardiac functions following mitral valve replacement, AM. HEART J. 75:302, 1968. Tandon, A. P., Smith, D. R., Whitaker, W., and Ionescu, M. I.: Long term haemodynamic evaluation of the aortic pericardial xenograft, Br. Heart J. (In press)
601
and laboratory
reports
Hemodynamic evaluation of the lonescu-Shiley pericardial xenograft in the mitral position
Anand P. Tandon, M.D., M.R.C.P. Donald R. Smith, M.D., F.R.C.P. Marian I. Ionescu, M.D., F.A.C.S. Leeds,
England
Glutaraldehyde treated pericardial xenografts have been used for heart valve replacement during the past 6 years.’ Clinical results have been extremely gratifying. Very low thrombogenicity without anticoagulant therapy is one of the important benefits of this type of valve replacement. This report presents the results of a late hemodynamic evaluation of 27 patients and of sequential studies of six patients who had mitral valve replacement with the Ionescu-Shiley pericardial xenograft. * Patients
and methods
Since March, 1971, 106 patients had mitral valve replacement with pericardial xenografts. Actuarial survival and event free curves are shown in Fig. 1. Four embolic episodes were noted in the entire series. All were mild or trivial, occurred within the first 6 weeks following valve replacement and left no sequelae. Clinically 94 per cent of patients were in Grade I (NYHA) at the latest assessment. Twenty-seven patients underwent hemodynamic evaluation at a mean duration of 40.3 +- 2.8 (range 24 to 59) months following valve insertion. The criteria for selection were an interval of at least two years from valve replacement and the informed consent of the patient. From the Departments of Cardiology General Infirmary, Leeds, England. Received
for publication
Jan.
Accepted
for publication
Mar.
Reprint Surgery,
requests: M. I. Ionescu, The General Infirmary,
‘ShiIey
Laboratories,
Irvine,
0002~8703/78/0595-0595$00.70/O
and Cardiothoracic
Surgery,
The
19, 1977. 16, 1977. M.D., Department Leeds, LSl 3EX,
of Cardiothoracic England.
California.
The annulus diameter of the grafts used was 25 mm. in two patients, 27 mm. in 15 patients, and 29 mm. in 10 patients. The clinical details of these patients are shown in Table I. Six patients had, in addition to the preoperative investigation, two separate hemodynamic ‘studies performed at mean intervals of 11.2 (f 1.6) and 42.8 (+ 3.3) months following pericardial xenograft implantation. Of the 20 patients who had preoperative cardiac catheterization, 10 had resting pulmonary artery systolic pressure greater than 60 mm. Hg. All patients were hospitalized 24 hours prior to hemodynamic study. On admission, a detailed clinical history, estimation of functional capability, physical examination, hematological assessment, a chest radiograph, a 1Zlead electrocardiogram and a phonocardiogram were obtained in all patients. Electrocardiograms and chest radiographs were analyzed for rhythm, left ventricular voltage (using the sum of SV, and RV,), and cardiothoracic ratio. Right and left heart catheterization was performed in the postabsorptive state without any prior sedation. Pulmonary and systemic pressures were transduced by strain gauge manometers @EM* 486) with the zero level set 5 cm. below the sternal angle, integrated electronically and recorded on a multi-channel ultraviolet light recorder (SEM’ 3012). Cardiac output was measured by the direct Fick method using 2 minutes of gas collection. Hemodynamic data were obtained during a 4-minute period of rest and between the fourth and sixth minute of a 6-minute period of supine leg exercise on a bicycle *Sheilds
6 1978
The
C. V. Mosby
Co.
and
Epstein
Monitoring,
Middlesex,
U.K.
American Heart Journal
595
Tandon,
Smith,
and
Ionescu
I%
MTRAL
REPLACEMENT Q4.E2.6% Q4.7*2.6% 82.1 t4.9%
90
,--"..
66.6 * 7.0%
free 3 mths. 60
(SS)
cerebral hcwt
1
abscess b&m
(451
I581
0 0
S.B.E S.B.E.
2
3
S.&E. t.embdLiun
(IS1
(333
4
trm
--. ..-’
(81
5
Ib.cdpatima
(2)
6
7
YEhR6
Fig. 1. Actuarial analysis of results following mitral pericardial xenograft valve replacement. expressed as per cent expected survival rate and individual event free curves for complications.
Table
I. Preoperative clinical details Number of patients
Male Female Age Mean Range Clbiical lesion stenosiB
Incompetence Mixed Rhythm Atria1 fibrillation Sinus rhythm Functional status (NYHA) II III IV Previous closed mitral valvotomy
8 19 43.6 yrs (k1.8) 19-62 yrs 9 6 12 19 8 6 19 2 12
ergometer. Left ventricular angiograms were performed in all patients at the end of the study. Pulmonary vascular resistance was calculated using the standard formula. The mean diastolic gradient across the pericardial xenograft was measured by planimetric integration of at least five simultaneously recorded phasic left ventricular and pulmonary wedge tracings. The xeno-
5616
The data are
graft surface area was calculated according to the hydraulic formula of Gorlin and Gorlin.’ Results Electrocardiographic
and radibgical
changes.
The mean cardiothoracic ratio showed a significant decrease from a preoperative level of 0.59 to 0.54 at the postoperative study (p < 0.001). The mean left ventricular voltage was 34.8 mm. preoperatively and 33.8 mm. at the postoperative study. This difference was not statistically significant. Hemodynamic findings at rsst. The results are given in Tables II and III. The mean cardiac index showed a significant increase from a preoperative level of 1.9 L./min./ M.* to 2.6 L./min./M.2 at the postoperative study (p < 0.001). The oxygen uptake also showed a smaller, but still significant rise (p < 0.05). The mean pulmonary artery and wedge pressures were significantly reduced at the postoperative study (p < 0.091), with a corresponding reduction in mean pulmonary vascular resistance (p < 0.01). Postoperatively, the mean diastolic gradient across the xenograft was 6.4 ( t 0.5) mm. Hg and the calculated xenograft surface area was 2.0 (& 0.1) cm.2 The results obtained in 10 patients with severe preoperative pulmonary hypertension are presented in Table III. This group of patients showed reductions in mean pulmonary artery and wedge pressures and in pulmonary
May, 1978, Vol. 95, No. 5
Hemodynamics
of mitral
pericardial
xenografts
II. Pre- and postoperative hemodynamic data (Mean values & SEM) of 27 patients with pericardial xenografts in the mitral position
Table
0, uptake (ml./min./M2) R Preop postop p value
123.7 f 6.0 136.3 zk4.0 to.05
E 314.6 + 40.4 406.5 t 14.4 to.05
Cardiac index (L.lmin.1M.Z)
PWP (mm. f&9
R
E
1.9 kO.1 2.6 kO.1 to.001
3.0 f 0.3 4.1 kO.2 to.01
PAP (mm. W E
R 23.3 f 1.9 13.8 k 0.8 <0.001
40.4 f 2.7 29.4 k1.5
Abbreviations: SEM = standard error of the mean; PWP = mean PVR = pulmonary vascular resistance; R = rest; E = exercise.
R
Mean diastolic gradient (mm. f-k)
PVR (dynes sec. cm:” M.?) E
38.7 k4.1 22.8 -+ 1.0 to.001
57.1 f 4.9 42.0 f 1.9 to.01
pulmonary
wedge
R
E
535.6 f 113.3 285.0 k 20.7 to.01 pressure;
656.8 k241.1 260.3 k 26.3 to.05 PAP = mean
Calculated xenograft surface area (cm?)
R
E
R
E
6.4 co.5
15.3 r0.9
2.0 kO.1
2.3 kO.1
pulmonary
artery
pressure;
Ill. Hemodynamic data in 10 patients with preoperative resting pulmonary systolic pressure > 60 mm. Hg (Mean values k SEM) Table
0, uptake (ml./min./M.2) R FhOp*
112.6 f 5.9 137.7 k7.7 -CO.05
Postop
p value
Cardiac index (L./min./M.2) E
308.5 f 50.1 392.6 + 19.3 -co.05
R
E
1.9 -+ 0.2 2.7 k 0.2 (0.01
2.8 *0.5 4.3 f 0.3 to.01
*Preoperative exercise studies available in six patients only.Abbreviations: SEM = standard error of the mean; PWP = mean PVR = pulmonary vascular resistance; R = rest; E = exercise
vascular resistance comparable to those found in patients with a lesser degree of pulmonary hypertension. Thus, in this series, the severity of preexisting pulmonary hypertension did not seem to influence the postoperative hemodynamic improvement. Hemddynamic findings on exercise. The cardiac index increased significantly from a preoperative level of 3.0 L./min./M.’ to 4.1 L./min./M.Z postoperatively (p < 0.01). For each milliliter increase in oxygen uptake, the cardiac index rose 5.6 ml. The mean pulmonary artery and wedge pressures showed significant reduction (p c 0.01) from the preoperative values but were still abnormally elevated. The pulmonary vascular resistance also showed significant reduction from the preoperative level (p < 0.05). Those patients with severe pulmonary hypertension preoperatively showed a similar improvement in
American
Heart
Journal
PWP (mm. f&J
PAP (mm. Hgl
R
E
27.7 2 2.9 15.6 + 1.2
44.5 + 2.2 29.8 f 2.7 to.01
pulmonary
wedge
R 50.4 k6.2 25.2 k1.8 to.001
pressure;
PVR (dynes sec. cm:’ M.?) E
66.3 * 5.9 44 2 3.9 to.01
PAP = mean
R
E
599.8 + 163.7 294.5 k30.7 to.01
pulmonary
834 f 239.8 288.9 k 55.2
pressure;
cardiac output, pulmonary pressures, and vascular resistance. Mean diastolic gradient increased from a resting value of 6.4 mm. Hg to 15.3 mm. Hg on exercise. The calculated surface area showed an increase with exercise to 2.3 cm.? Sequential studies. One preoperative and two separate postoperative studies were performed in six patients. These hemodynamic investigations were carried out under identical physiological conditions and the results are presented graphically in Figs. 2 and 3. At the first postoperative study the cardiac index, mean pulmonary artery and wedge pressures, and pulmonary vascular resistance showed a significant improvement, both at rest and on exercise, when compared with the preoperative data. The improvement was similar to that obtained in the entire group of patients as described in the previous paragraphs.
597
Tandon,
Smith,
__
and
Ionescu
I- S MITRAL
PERICARDIAL
XENOGRAFT
SEQMNTIAL
HAEMODYNAMIC
DATA AT REST L./min./sq.m.
ml./minhq.m.
,/*
i
P>O.l
P>O.5
1
II co.os
0i
P>O.7
dm
mm. Hg.
sac cri?iq.m.
40
l PRE-OP n Fig.
2. Sequential
‘1st. POST-OP
= 6 (valve size hemodynamic
27:
(llmtha)
‘2nd. POST-OP
(43mths.)
MEAN? S.E.M.
four patients. 29:two patients.) data
at rest
from
six patients
with
mitral
pericardial
xenograft.
PWP = mean pulmonary wedge pressure; 0, Uptake = oxygen uptake; Mean PAP = mean pulmonary pressure; Pulm. Vast. Resistance = pulmonary vascular resistance; SEM = standard error of the mean.
There were no significant changes in cardiac index, pulmonary artery and wedge pressures, and pulmonary vascular resistance between the first and the second postoperative study. The mean diastolic gradient across the xenografts. were 7.1 mm. Hg at rest and 20.1 mm. Hg on exercise at the first, and 6.6 mm. Hg and 19.1 mm. Hg at the second postoperative study. This difference was not significant. The calculated xenograft areas were 2.2 cm.2 at rest and 2.6 cm.2 on exercise at the first postoperative study. A marginal increase to 2.3 and 2.7 cm.2, respectively, was noted at the second postoperative study, but again the difference was not significant. Left ventricular angiography. Left ventricular angiograms demonstrated competent pericardial xenografts in all patients. Discussion
The pericardial xenograft was primarily created to minimize the rate of thromboembolism
598
Mean artery
traditionally associated with prosthetic replacement of the mitral valve. The experience during the past 6 years has demonstrated that, even without the use of anticoagulants, this aim has been attained.l The structural integrity of the xenograft has been maintained, as shown by six years of clinical follow-up and by over seven years of fatigue testing in vitro. The results of this study demonstrated that mitral valve replacement with pericardial xenografts produced significant hemodynamic improvement, and that this improvement was maintained for periods of up to 59 months following valve insertion. The study also confirmed the previously reported reversibility of pulmonary hypertension following mitral valve replacement.“-” The results showed that, although a postoperative increase in cardiac output and in oxygen uptake was demonstrated both at rest and during exercise, the hemodynamic response to exercise
May, 1978, Vol. 95, No. 5
Hemodynamics
r
-
I-S
MITRAL
PERKMDIAL
of mitral
pericardial
nenografts
XENOGRAFT
SEQUENTIAL HAEMOOYNAMC
DATA ON EXERCISE
PW.7
*WE-OP n=6(Vak
Fig. 3. Sequential hemodynamic tions as in Fig. 2.
l lst. POST-OP(llmthd Site
27:fWr
patientS.29:
data
on exercise
l 2nd two
from
was still impaired. Postoperatively, the mean pulmonary artery and wedge pressures approached normal figures at rest but rose to abnormal levels with exercise. This seems to be a universal finding with all types of mitral valve replacement,3. ‘-16 and it may be related to the fact that all valve substitutes inserted in the mitral position produce some degree of obstruction to forward flow, especially during exercise. The mean diastolic gradient across the mitral pericardial xenograft of 6.4 mm. Hg compares favorably with gradients obtained with other mitral valve substitutesJ. 8.II-l4 Published results of postoperative hemodynamic evaluations of other currently used mitral valve replacements are given in Table IV. These data provide only a perspective against which the results of the present study can be considered. Direct comparison between results obtained with various valve substitutes is difficult due to the differences in the methods of study and the diversity of patient population. Furthermore, only scanty reports of “late” hemodynamic eval-
American
Heart
Journal
POST-OP
(43mths.I
MEAN? S.E.M.
Pat&MS.)
six patients
with
mitral
pericardial
xenograft.
Abbrevia-
uations are available, the majority of these having been performed at less than 18 months postoperatively as compared with 40 months in the present study. Nevertheless, the data presented in Table IV show that hemodynamitally the pericardial xenograft compares favorably with other types of valve substitute used in the mitral position. Although the number of patients with sequential hemodynamic investigations was small, the results are of considerable importance. They established that maximum circulatory improvement was obtained by the end of the first year following valve insertion and that the functional integrity of the xenograft was maintained intact with the passage of time. Similar results were obtained from investigations performed on patients with pericardial xenografts in the aortic position.” In conclusion, this study has demonstrated significant hemodynamic improvement following mitral valve replacement with the Ionescu-Shiley pericardial xenograft and maintenance of valve
599
Tandon,
Smith,
end
Ionescu
IV. Hemodynamic results following mitral valve replacement with different types of valve substitutes
Table
Authors Pietras
et al3 (1974)
Haerten Bjork
et al* (1976) et al”
Haerten Sigwart Johnson Lurie et Present
(1974)
et aI8 (1976) et alI2 (1976) et alI3 (1975) al” (1976) study
Mitral
valve substitute
Time of study (months POStoP)
Starr-Edwards valve, Model 6309 Starr-Edwards valve, Model 6300 Bjork-Shiley valve50’ angle 69” angle Lillehei-Kaster valve Lillehei-Kaster valve Hancock porcine xenograft Hancock porcine xenograft I-S pericardial xenograft
*Mean period not available. tCardiac output. Abbreviations: PWP = pulmonary
wedge pressure;
Mean PWP (mm. Hgl
R
E
R
16.3
3.2
4.8
13.2
12
2.0
3.4
5-13* 5-13*
4.6.f 4.4t 2.0 3.0 2.6 2.5 2.6
7.4t 7.9t 3.4
l-6* 5.5 1-15 40.3
*
4.1
E
Mean diastolic gradient (mm. f&d R
E
30
11.6
24.5
14
26
7.2
16.7 16.9 14 16 17 15 13.8
30.4 25.8 29
4.3 4.7 6.2 9 6.5 8 6.4
29.4
11.7 8.4
15.3
R = rest; E = exert
function up to 59 months postoperatively. Repeat circulatory investigations will be performed at longer intervals in order to continually appraise the function of this valve. Summary
Hemodynamic studies were performed in 27 patients at a mean interval of 40.3 (range 24 to 59) months following mitral valve replacement with pericardial xenografts. Six patients had sequential studies, one before operation and two separate investigations at mean intervals of 11.2 and 42.8 months following valve replacement. The results showed significant increase in cardiac index, reduction in mean pulmonary artery and wedge pressures, and decrease in pulmonary vascular resistance both at rest and during exercise, when compared with the preoperative values. The mean diastolic gradient across the pericardial xenografts was 6.4 mm. Hg at rest and 15.3 mm. Hg during exercise. The calculated xenograft surface area was 2.0 and 2.3 cm.2, respectively. The sequential studies established that the maximum hemodynamic improvement was achieved within the first year following valve replacement and that the functional performance of the xenografts was maintained, unaltered, with the passage of time.
600
Cardiac index (L./min./M.z)
We wish to thank Miss Anne preparation of thii manuscript.
E. Tunnicliffe
for help in the
REFERENCES 1.
2.
3.
4.
5.
6.
7.
8.
Ionescu, M. I., Tandon, A. P., Mary, D. A. S., and Abid, A.: Heart valve replacement with the Ionescu-Shiley pericardial xenograft, J. Thorac. Cardiovasc. Surg. 73:31, 1977. Gorlin, R., and Gorlin, S. G.: Hydraulic formula for calculation of the area of the stenotic mitral valve, other cardiac valves and central circulatory shunts, AM. HEART J. 41 :l, 1951. Pietras, R. J., Long, D. M., and Rosen, K. M.: Late postoperative clinical and hemodynamic assessment of the earIy cloth-covered Starr-Edwards mitral valve prosthesis, J. Thorac. Cardiovasc. Surg. 67:456, 1974. Dalen, J. E., Matloff, J. M., Evans, G. L., Hoppin, F. G., Jr., Bhardwaj, P., Harken, D. E., and Dexter, L.: Early reduction of pulmonary vascular resistance after mitral valve replacement, N. Engl. J. Med. 277387, 1972. Zener, J. C., Hancock, E. W., Shumway, N. E., and Harrison, D. C.: Regression of extreme pulmonary hypertension after mitral valve surgery, Am. J. Cardiol. 30:820, 1972. Kaul, T. K., Bain, W. H., Jones, J. V., Lorimer, A. R., Thomson, R. M., Turner, M. A., and Escarous, A.: Mitral valve replacement in the presence of severe pulmonary hypertension, Thorax 3 1:332, 1976. Russell, T., II, Kremkau, E. L., Kloster, F., and Starr, A.: Late hemodynamic function of cloth-covered StarrEdwards valve prostheses, Circulation 45: and 46 (Suppl. 1):8, 1972. Haerten, K., Both, A., Loogen, F., and Bricks, W.: Hemodynamics after mitral valve replacement with Starr-Edwards, Bjork-Shiley and Lillehei-Kaster prostheses (Abstr.), Circulation 53 and 54 (Suppl. II):lSl, 1976.
May, 1978, Vol. 95, No. 5
Hemodynamics
9.
10.
11.
12.
13.
Reid, J. R., Stevens, T. W., Segwast, W., Fulweber, R. C., and Alexander, J. L.: Hemodynamic evaluation of the Beall mitral valve prosthesis, Circulation 45(Suppl. I):l, 1972. Fernandez, J., Morse, D., Spagna, P., Lemole, G., Gooch, A., Yang, S. S., and Maranhao, B.: Results of mitral valve replacement with the Beall prosthesis in 209 patients, J. Thorac. Cardiovasc. Surg. 71:218, 1976. Bjork, V. O., Book K., and Holmgren, A.: The BjorkShiley mitral valve prosthesis, Ann. Thorac. Surg. l&379, 1974. S&wart, U., Schmidt, H., Gleichmann, U., and Borst, H. G.: In vivo evaluation of the Lillehei-Kaster heart valve prosthesis, Ann. Thorac. Surg. 22:213, 1976. Johnson, A. D., Daily, P. O., Peterson, K. L., LeWinter, M., DiDonna, G. J., Blair, G., and Niwayama, G.: Functional evaluation of the porcine heterograft in the mitral position, Circulation 52(Suppl. 1):40, 1975.
American
Heart
Journal
14.
15.
16.
17.
of mitral
pericardial
xenografts
Lurie, A. J., Miller, R. R., Maxwell, K., Vismara, L. A., Hurley, E. J., and Mason, D. T.: Postoperative hemodynamic assessment of the glutaraldehyde-preserved porcine heterograft in the aortic and mitral positions (Abstr.), Cir&lation 53 and 54 (Suppl. II):148, 1976. Book, K.: Mitral valve renlacement with Biork-Shilev tilting disc valve-A clinical and hemodynam”ic study in patients with isolated mitral valve lesions, Stand. J. Thorac. Cardiovasc. Surg. Suppl. 12:2, 1974. Hultgren, H., Hubis, H., and Shumway, N. E.: Cardiac functions following mitral valve replacement, AM. HEART J. 75:302, 1968. Tandon, A. P., Smith, D. R., Whitaker, W., and Ionescu, M. I.: Long term haemodynamic evaluation of the aortic pericardial xenograft, Br. Heart J. (In press)
601