Surgical management of pulmonary stenosis in tetralogy of Fallot

Surgical management of pulmonary stenosis in tetralogy of Fallot Fifty-jive consecutive patients with the tetralogy of Fallot underwent intracardiac repair in a 12 month period. A standardized protocol for outflow tract enlargement was used. When the measured diameter of the pulmonary valve ring was at least the "minimum acceptable pulmonary valve ring diameter," primary patch-graft enlargement across the valve ring was not done (Group I, 34 patients); when it was less, primary patch-graft enlargement was done (Group II, 21 patients). The right ventricular-left ventricular systolic pressure ratio (PRV/LV) after repair without patch-graft enlargement across the ring was related to the size of the ring. Sixteen (94 percent) of 17 such patients with normal-sized or large pulmonary valve rings (according to the criteria of Rowlatt, Rimoldi, and Lev') had PRV/LV equal to or less than 0.65; four (80 percent) ofjive patients with smaller rings but within the 50 percent conjidence limits had PRV/LV equal to or less than 0.65; jive (56 percent) of nine with still smaller rings but within the 72.5 percent conjidence limits had PRv/Lv equal to or less than 0.65. In Group II, IS patients had abnormally small rings, but after patch-graft enlargement the mean PRV/LV was 0.44 ± 0./40. A surgical protocol based on these data has been developed.

Albert D. Pacifico, M.D., John W. Kirklin, M.D., and Eugene H. Blackstone, M.D. (by invitation), Birmingham, Ala.

Ideally, the surgical treatment of patients with the tetralogy of Fallot should result in normal right ventricular systolic pressure late postoperatively, absence of right ventricular-pulmonary artery gradient, and a competent pulmonary valve. Hypoplasia of varying degrees of the right ventricular infundibulum, pulmonary valve ring, and main pulmonary artery and the frequently bicuspid configuration of the pulmonary valve. rarely allow this ideal result; and sometimes do not allow an adequate result from a repair confined to pulmonary valvotomy, resection of the elements of the infundibulum, and mobilization of the free wall of right ventricle. The insertion of an enlarging patch-graft into a vertical incision across the infundibulum and pulmonary valve ring to the bifurcation of the pulmonary artery can provide good relief of the pulmonary stenosis in most patients. However, the graft also produces complete pulmonary valve incompetence. Precise indications for this enlarging patch-graft across the From the Department of Surgery, University of Alabama School of Medicine and Medical Center, Birmingham, Ala. Read at the Fifty-seventh Annual Meeting of The American Association for Thoracic Surgery, Toronto, Ontario, Canada, April 18, 19, and 20, 1977. Address for reprints: John W. Kirklin, M.D., Department of Surgery, University Station, Birmingham, Ala. 35294.

382

pulmonary valve ring are currently controversial, and practices vary from almost routine primary enlargement to nearly complete avoidance of primary enlargement and then immediate secondary enlargement if the ratio of right ventricular to left ventricular systolic pressure (PRv/LV), measured after the initial repair while temporarily discontinuing cardiopulmonary bypass, is unacceptably high. Some surgeons base their procedure upon the preoperative cineangiogram and others upon visual estimates and rules of thumb. We are reporting the results of a clinical trial, during a 12 month period, in which a set of rules was used relating the decision for primary enlargement of the pulmonary valve ring to a weight-related "minimum pulmonary valve ring diameter." We have added some experiences prior and subsequent to this period for supplemental analyses. The results of this trial and the knowledge of pulmonary valve ring diameter in normal subjects, developed by Rowlatt, Rimoldi, and Lev, I have led to a recommended protocol based on prediction of the probability of the postrepair PRV!Lv being acceptably low without patch-graft enlargement from measurement of the size of the pulmonary valve ring. Patients and methods All patients undergoing repair of tetralogy of Fallot at the University of Alabama Medical Center in the first

Volume 74 Number 3

Pulmonary stenosis in tetralogy of Failot

383

September, 1977

12 months of the use of a new protocol (May 1, 1975, to May 1, 1976) were analyzed for this study. The protocol used a table relating the "minimal acceptable pulmonary valve ring diameter" to body weight (Table I). Venugopal and Subramanian" had stated that a diameter of 12 mm. was the minimum acceptable for a group of infants and small children. Believing that this could not be true for all sizes of infants or small children, we related the minimum acceptable size of the ring to the size of the patient. Since the average weight of their patients was 12 kilograms, we assumed their recommendation was correct for patients weighing 12 kilograms. Assuming a perfect circle, valve area is 133 sq. mm. when diameter is 12 mm., and we calculated from this that an acceptable ratio of pulmonary valve area (square millimeters) to body weight (kilograms) is 9. We calculated the "minimum acceptable valve area" for various weights and from this calculated the "minimum acceptable pulmonary valve ring diameter" indicated in Table I. The essential parts of the new protocol were as follows: measurement of the diameter of the "pulmonary valve ring" after valvotomy with calibrated Hegar dilators, as suggested earlier by Dobell and colleagues"; use of the table (Table I); and in general a short vertical ventriculotomy in the right ventricular infundibulum closed with a woven Dacron patch. We use the phrase "pulmonary valve ring" knowing that the size of dilator that is accepted depends in part on the configuration of the pulmonary valve, the completeness of the valvotomy, and any supravalvular narrowing that may be present. As usual, we measured the systolic pressure in the right ventricle and left ventricle immediately after repair and again just before closing the chest. The patients fell into two groups. In one (Group I), patchgraft enlargement across the pulmonary valve ring was not done as part of the initial repair; the decision was based largely but not exclusively, upon relating the measured diameter of the pulmonary valve ring to the "minimal acceptable diameter" shown in Table I. In three of the 34 patients in Group I, pressure measurements immediately after repair showed such a high PRV!LV, with a low or normal pulmonary artery pressure, that cardiopulmonary bypass was promptly re-established and an enlarging patch-graft was inserted across the pulmonary valve ring. All three survived. The 21 remaining patients (Group II) had primary patch-graft enlargement across the pulmonary valve ring, usually because the measured pulmonary valve ring diameter was less than the' 'minimum acceptable diameter" shown in Table I. The operation was usually done through a short vertical incision in the outflow portion of the right ven-

Table I. Minimum acceptable pulmonary valve ring diameter employed in 1975 and 1976 Minimum ring size Weight (Kg.) 3 4 5 6 7 8 9 10 12 14 16 18 20 25 30 35 40

Diameter (mm.)

Area (sq. mm.)

6 7 7.5 8 9 9.5 10 11 12 13 13.5 14 15

28 38 45 50 63 72 81 90 113 126 144 162 177 225 270 314 314

17

18.5 20 20

Table II. Repair of tetralogy of Failot (May, 1975, to May, 1976) Group lIt

Group It

Age* 3 to 6 to 12 to 24 to 48 to 6 to 12 to 18 to 30 to Totals

<3 <6 <12 <24 <48 <72 <12 <18 <30 <45 :2:45

No. mo. mo. mo. mo. mo. mo. yr. yr. yr. yr. yr.

2 5 5 3 6 5 2 2 3 1 34

Hospital deaths No. 0 2 0 0 0 0 0 0 0 2(6%)

No.

Hospital deaths No.

2

0

2 6

0 0

5

1

4

0

2

0

21

1(5%)

·Calculated according to the Julian calendar. tGroup I includes patients without primary patch graft enlargement across the pulmonary valve ring; Group II includes those with primary ring enlargement.

tricle. The major portion of the hypertrophied parietal bands and, where indicated, the septal and moderator bands were excised, and the free wall of the right ventricle was mobilized. Wide pulmonary valvotomy was done when the pulmonary valve was stenotic, and the cusps were dissected away from the pulmonary artery when supravalvular narrowing was present. The diameter of the pulmonary valve ring was then sized by passing successively larger calibrated Hegar

The Journal of Thoracic and Cardiovascular Surgery

3 84 Pacifico, Kirklin, Blackstone

Table III. Repair of tetralogy of Fallot (May, 1975, to May, 1976) Patch-graft enlargement of pulmonary valve ring None Status of patient

No,

Primary repair Previous Blalock-Taussig anastomosis Previous Waterston anastomosis Previous Potts, then Blalock-Taussig Previous end-to-end right subclavianto-right upper lobe artery anastomosis

23 5 2 I

Totals

31

I

Initial %of total (62%) (56%) (29%)

No. 14 3

3

I

-c

Of) total

_ _

(38%) (44%)

_

(71%)

Secondary

_ _

No.

1

2

Total

37 9 7 I 1

(56%)

21

(44%)

3*

55

*All patients survived.

dilators until the one that fit snugly but not tightly was identified. The ventricular septal defect was repaired by sewing in place with a continuous polypropylene suture a patch of knitted Dacron velour. In patients in Group I, a measured woven Dacron patch was sutured into the ventriculotomy to prevent narrowing of the infundibulum with the closure. In patients in Group II, the incision was carried primarily across the pulmonary valve ring to the bifurcation of the pulmonary artery and, at times, onto the first part of the left pulmonary artery, and a measured patch was sewn into the entire incision. The patch was made from a preclotted woven Dacron tube whose diameter was approximately that of the ascending aorta; it was cut in half longitudinally and, without being stretched, was cut to the length of the incision and the ends rounded. The operations were done with cardiopulmonary bypass and profound total body and cardiac hypothermia. Two venous cannulas and a left atrial vent were used except in the smallest children, in whom only a single venous cannula was used. When two venous cannulas were used, the right atrium was opened during cooling, the foramen ovale was inspected and closed if patent, and the right atrium was closed. When one venous cannula was used, these procedures were done during total circulatory arrest. During most of the intraventricular repair the aorta was cross-clamped (for up to 45 minutes); the patient's body temperature was 20° C. to 24° C, and the perfusion flow rate was reduced to 0.5 to 1.6 L. . min. -1 . M. -2. When required for exposure, total circulatory arrest (for up to 45 minutes) was used with the body temperature at 20° C. Previously established Blalock-Taussig anastomoses were ligated. Waterston anastomoses were closed by disconnecting the anatomosis and closing the pulmonary and aortic openings separately. The last

PRV/LV measurement made before closing the chest was used in data analysis, except that the one taken after first temporarily discontinuing bypass was used for the three patients in Group I in whom secondary patch-graft enlargement of the ring was done. Pulmonary artery pressure was not measured routinely, but by palpation it was determined to be about normal in all patients except the patient in Group II with stenosis at the pulmonary artery bifurcation. During this 12 month period, 58 patients underwent intracardiac repair of classical tetralogy of Fallot, exclusive of those with congenital pulmonary atresia. In three patients, all of whom were hospital survivors, no measurements were available upon retrospective study of the operative notes, and they are not included in the study. The ages and categories of the 55 patients included in the study are shown in Tables II and III. During this time period no palliative operations were done for tetralogy of Fallot, no patients were denied operation because of the severity of their lesion or for other reasons, and no patients died without operation. For certain analyses, we have increased the number of Group I patients by including the two patients who had the necessary measurements and who w.ere operated upon prior to May, 1975, as well as the 13 operated upon between May I and Dec. 31, 1976. Rowlatt, Rimoldi, and Levi have presented regression equations based upon measurements made of fixed autopsy hearts from 75 children of various ages, from which the average normal annulus circumference can be calculated, given an independent variable such as body weight or body surface area. They also presented the standard deviation of the regression equation, which approximates the standard deviation for this calculated normal annulus circumference. Since we assume these variables are normally distributed, a simple

Volume 74

Pulmonary stenosis in tetralogy of Fallot

Number 3

385

September, 1977

Table IV. Estimated probability of requiring patch-graft enlargement across pulmonary valve ring Probability *

(sq. M.)

15% (mean normalrt

«normal but within 50% CL)

50% «normal but within 72.5% CL)

«normal but within 95% CL)

90% (small,
Highest value within 95% CL:j:

0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.90 1.0 1.2 1.4 1.6 1.8 2.0

5.9 7.3 8.4 9.3 10.1 10.7 11.3 11.9 12.3 12.8 13.2 13.5 13.9 14.2 14.8 15.3 16.2 17.0 17.6 18.2 18.7

5.1 6.5 7.6 8.5 9.3 10.0 10.6 11.1 11.6 12.0 12.4 12.7 13.1 13.4 14.0 14.5 15.4 16.2 16.8 17.4 18.0

4.6 6.1 7.2 8.1 8.8 9.5 10.1 10.6 11.1 11.5 11.9 12.3 12.6 12.9 13.5 14.0 14.9 15.7 16.4 16.9 17.5

3.6 5.1 6.2 7.1 7.8 8.5 9.1 9.6 10.1 10.5 10.9 11.3 11.6 11.9 12.5 13.0 13.9 14.7 15.4 15.9 16.5

< 3.6 < 5.1 < 6.2 < 7.1 < 7.8 < 8.5 < 9.1 < 9.6 <10.1 <10.5 <19. 9 <11.3 <11.6 <11.9 <12.5 <13.0 <13.9 <14.7 <15.4 <15.9 <16.5

8.1 9.6 10.7 11.6 12.3 13.0 13.6 14.1 14.6 15.0 15.4 15.8 16.1 16.4 17.0 17.6 18.5 19.2 19.9 20.5 21.0

35%

BSA

75%

Legend: Based on data of Rowlatt, Rimoldi and Lev, 1 described by the equation:

Diameter(mm.) = 1017T[3.5869 . 10glO (BSA) - 9.5431] CL, Confidence limits. 'That is, probability of PRV/LV > 0.65 without patch across valve ring. tPhrases in parentheses describe size of pulmonary valve ring relative to patient's body surface area (BSA); the numbers are the measured internal diameter of the pulmonary valve ring (mm.) after valvotomy. :j:The woven Dacron tube from which the outflow patch is made can be this size.

relationship exists between this standard deviation and confidence limit (CL): CLa

=

Y ± a . S.D.

where y is the normal annulus circumference calculated from the regression equations, S.D. is the standard deviation of the regression estimate, and a is a number which varies according to the confidence limits desired (a = 0.67449 for 50 percent limits, a = 1.09162 for 72.5 percent limits, and a: = 1.95996 for 95 percent limits). To construct the table using only the lower confidence limits (that is, the "small" side of normal), we employed the equation: Lower CLa

=

Y- a . S.D.

These values for circumference in centimeters were transformed to diameter in millimeters by the equation: Diameter (mm.) = circumference (em) 1O/7T

From all of this, we have constructed tables giving the mean normal value for pulmonary valve ring diameter and the confidence limits according to body surface area and to weight. This information was used in the construction of Tables IV and V. For analyses, the size of the pulmonary valve ring in each individual patient was calculated as its degree of normality (Z), the number of standard deviations by which actual ring circumference deviates from the mean normal circumference. This was calculated by the formula: actual ring circumference - mean normal circumference

Z = ------------------

standard deviation of normal circumference

where the ring circumference in centimeters was determined from the measured ring diameter in millimeters as: Actual ring circumference

= 7T( diameter) /10

The Journal of

386

Pacifico, Kirklin, Blackstone

Thoracic and Cardiovascular Surgery

Table V. Estimated probability of requiring patch-graft enlargement across pulmonary valve ring Probability' 35% 15% (Kg.)

(mean normal)t

«normal but within 50% CL)

3 4 5 6 7 8 9 10 12 14 16 18 20 25 30 35

5.8 7.2 8.3 9.2 10.0 10.7 11.3 11.8 12.7 13.5 14.1 14.7 15.2 16.4 17.3 18.0

4.9 6.3 7.4 8.4 9.1 9.8 10.4 10.9 11.8 12.6 13.2 13.8 14.4 15.5 16.4 17.2

Weight

75%

90% (small.

Highest value

50% «normal but within 72.5% CL)

«normal but within 95% CL)


within

95% CL)

95% CL:j:

4.3 5.8 6.9 7.8 8.6 9.2 9.8 10.4 11.3 12.0 12.7 13.3 13.8 14.9 15.8 16.6

3.2 4.6 5.8 6.7 7.4 8.1 8.7 9.2 10.1 10.9 11.6 12.7 13.1 13.8 14.7 15.5

< 3.2 < 4.6 < 5.8 < 6.7 < 7.4 < 8.1 < 8.7 < 9.2 <10.1 <10.9 <11.6 <12.7 <13.1 <13.8 <14.7 <15.5

8.4 9.8 10.9 11.8 12.6 13.3 13.8 14.4 15.3 16.0 16.7 17.3 17.8 18.9 19.9 20.6

Legend: Based on data of Rowlatt, Rimoldi, and Lev.' described by the equation:

Diameter (mm.) = IOI1T[3.6108 . log,. (Wgtkg ,)

+ 0.0933]

CL. confidence limits. 'That is. probability of PRv!LV > 0.65 without patch across valve ring. tPhrases in parenthesesdescribe size of pulmonaryvalve ring relative to patient's weight; the numbersare the measuredinternal diameter of the pulmonary valve ring (mm.) after valvotomy. :j:The woven Dacron tube from which the outflow patch is made can be this size.

The mean normal circumference based upon body surface area or weight and its standard deviation were determined from the regression equations developed by Rowlatt, Rimoldi, and Lev. t This Z is actually a standardized score expressing the degree of normality of the pulmonary valve ring, with the statistical property that its mean is always zero and its standard deviation is always 1. Thus the value of Z is a statistic which can be looked up in a normal distribution table to ascertain its p value and confidence limits directly. For example, when Z is -0.674, the size of the pulmonary valve ring is exactly on the lower 50 percent confidence limit; when Z is -1.09, it is exactly on the lower 72.5 percent confidence limit; and when Z is -1.96, it is exactly on the lower 95 percent confidence limit. This information was used to construct Tables VI to VIII. Use of Z was chosen as superior to taking the ratio between actual ring circumference and the mean normal circumference, which generates a skewed distribution and causes statistical difficulties in the analysis. The probability that PRv/Lv is greater than 0.65 was estimated as a function of Z using probability of event techniques as described by us earlier. 4. 5 Confidence limits for proportions were also calculated by methods described earlier by us. 4. 5

Results Annulus size and postrepair pressure relations. The PRV/LV ratios in the operating room after repair without patch-graft enlargement of the pulmonary valve ring are related to the size of the pulmonary valve ring, expressed in relation to the normal values of Rowlatt, Rimoldi, and Lev.! Among the 17 patients whose pulmonary valve ring diameter, normalized by body surface area, was normal or larger than normal, 16 had a postrepair PRV/LV equal to or less than 0.65; the mean value of PRV/LV for the group was 0.43 ± 0.150 (Table VI). Among patients with smaller valve rings, the mean of the PRV/LV ratios for the group tended to be larger, and the proportion of individuals with PRV/LV equal to or less than 0.65 was usually smaller. The same general relations pertain when the normalization is made according to body weight (Table VII). Analysis of the enlarged Group I, including patients operated upon before and after the study period (see Methods), gives results which are similar to those from the study period alone (Table VIII). In this enlarged group, PRV/LV after repair without patch-graft enlargement of the ring has a highly significant correlation with the size of the pulmonary valve ring (Fig. 1).

Volume 74

Pulmonary stenosis in tetralogy of Fallot

Number 3

387

September, 1977

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Fig. 1. Relationship of Pav/r.v and size of the pulmonary valve ring expressed for each patient as Z (see Methods). A, The mean normal value of the valve ring was calculated from each patient's body surface area (BSA). The solid line represents the regression equation: In PRV/LV = -0.68 ± 0.052 - 0.21 ± 0.038 [size Z], where In is natural logarithm. The P for the relations between PRV/ LV and Z is <0.000 I, and the standard error of the regression equation is 0.357. B, The mean normal value was calculated from each patient's weight. The regression equation is: In PRV/LV = -0.83 ± 0.054 - 0.20 ± 0.036[size Z]. The P for the relations between PRV/LV and Z is <0.0001, and the standard error of the regression equation is 0.359. In both A and B, the dashed lines enclose the 95 percent confidence limits (Cl.).

Table VI. Repair of tetralogy of Fallot (May, 1975, to May, 1976) Size of pulmonary valve ring (relative to BSA)


Small (outside 95% CL)

17

5

0.43 ± 0.150 16(94%)

0.46 ± 0.138 4(80%)

9 0.65 ± 0.227 5(56%)

2 0.50 ± 0.65t 2(100%)

I 0.81

I

I

0.67

0.52

3 0.49 ± 0.085

15:1: 0.44 ± 0.140

2dVormal mean value Group 1* n PRV/LV

(mean ± S.D.)

PRV/LV $

0.65

o

Group 1I* n

after RV ring enlargement

PRV/LV

Legend: BSA, Body surface area. CL, Confidence limits. PRv!Lv, Ratio of right ventricular systolic pressure to left ventricular systolic pressure. S.D., Standard deviation.

*Group I includes patients without primary patch graft enlargement across the pulmonary valve ring; Group II includes those with primary ring enlargement. tlndividual ratios for the two patients. :j:Excluding one surviving patient with unrelieved stenosis at bifurcation of pulmonary artery whose ratio was 1.

Probability of event analysis of this group gives a statistically nonsignificant relation between the size of the pulmonary valve ring and probability that PRv/Lv after repair without patch-graft enlargement will be greater than 0.65 (Fig. 2). Sixteen of the 21 patients undergoing primary patch-graft enlargement across the pulmonary valve

ring (Group II) had an abnormally small pulmonary valve ring (that is, one whose diameter normalized according to body surface area was less than the 95 percent lower confidence limit of normal according to Rowlatt, Rimoldi, and Levi). One surviving patient had unrelieved stenosis at the origins of the right and left pulmonary arteries and a PRV/LV after repair of

388

The Journal of Thoracic and Cardiovascular

Pacifico, Kirklin, Blackstone

Surgery

Table VII. Repair of tetralogy of Fallot (May, 1975, to May, 1976) Size of pulmonary valve ring (relative to body weight, Kg.) '2Normal mean value




10 0.40 ± 0.156 9(90%)

14 0.48 ± 0.147 13(93%)

5 0.53 ± 0.110 4(80%)

1.0

Small (outside 95% CL)

Group 1* n PRV!LV PRY/LV

(mean ± S.D.) :5 0.65

Group 1/* 3 0.54 ± 0.123

n

after ring enlargement

PRY/LV

I

o I

0.59

4 0.74 ± 0.200 1(25%) 16t 0.44 ± 0.136

Legend: CL, Confidence limits. PRv!Lv, Ratio of right ventricular systolic pressure to left ventricular systolic pressure. S.D., Standard deviation. *Group I includes patients without primary patch graft enlargement across the pulmonary valve ring; Group II includes those with primary ring enlargement. ~Excluding one surviving patient with unrelieved stenosis at bifurcation of pulmonary artery whose ratio was I.

Table VIII. Repair of tetralogy of Fallot without primary patch-graft enlargement across pulmonary valve ring* Size of pulmonary valve ring (relative to BSA, sq. M.)

n (mean ± S.D.) PRY/LV :5 0.65

PRV/LV

"?Normal mean value




25 0.40 ± 0.139 24(96%)

8 0.51 ± 0.179 6(75%)

9 0.65 ± 0.227 5(56%)

5 0.96 ± 0.409 2(40%)

Small (outside 95% CL) 2 0.81,0.69

o

Legend: BSA, Body surface area. CL, Confidence limits. PRV/LV, Ratio of right ventricular systolic pressure to left ventricular systolic pressure. S.D., Standard deviation. *Includes 34 patients in Group I plus 15 additional patients (see text).

1.0. Among the other 15 patients with these small pulmonary valve rings, the mean value of the PRV/LV after repair with primary patch-graft enlargement across the pulmonary valve ring was 0.44 ± 0.140 (Table VIII). Among the 55 patients, the younger the patient was at the time of repair, the smaller the pulmonary valve ring (Z) tended to be (Fig. 3, A). The same relations pertained among the 38 patients undergoing primary repair, including the patient with an end-to-end anastomosis of the right subclavian-to--right upper lobe pulmonary artery which had never functioned (Fig. 3, B). Patients having had a previous systemic-pulmonary artery shunt (excluding the above-mentioned patient) had normalized pulmonary valve ring sizes (Z) not statistically significantly different from those undergoing primary repair. According to the set of rules and judgments described, during this time period 24 (44 percent) of the 55 patients in the group studied had an outflow patch placed across the pulmonary valve ring (Table III).

Fifteen (50 percent) of 30 patients less than 4 years of age underwent patch-graft enlargement across the pulmonary valve ring, compared with nine (36 percent) of 25 patients 4 years of age or older at the time of repair (p value = 0.3). Three (6 percent) of the 55 patients in the group studied died in the hospital (Table II). One patient, who had been on long-term propranolol treatment preoperatively, who did not have patch-graft enlargement across the valve ring, and whose PRv/Lv after repair was equal to or less than 0.65, died of low cardiac output on the second postoperative day; bilateral hemothoraces were present at autopsy. One patient who had patch-graft enlargement across the valve ring and whose postrepair PRV/LV was 0.65 died on the twelfth postoperative day from the effects of pulmonary edema without left atrial hypertension; autopsy showed massive hyaline membrane formation in the lungs with essentially absent air spaces. One patient with a normalsized pulmonary valve ring and a PRV/LV less than 0.65 after repair without patch-graft enlargement had a

Volume 74 Number 3

389

Pulmonary stenosis in tetralogy of Fallot

September, 1977

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Fig. 2. Probability that PRV/Lv is greater than 0.65 as a function of size of the pulmonary valve ring expressed as Z. The solid line is the probability and the dashed lines the 70 percent confidence limits. A. The mean normal value was calculated from each patient's body surface area, and: Pr = 1/(1 + exp( 1.48 + 1.36[Z], where Pr is probability and exp is e, the base of the natural logarithms. a. The mean normal value was calculated from each patient's weight, and: Pr = 1/(1 + exp( 1.86 + 1.09[Z]). The relations in both A and a are statistically not significant. CL. Confidence limits.

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\.l-_-l.._L..-J_...1....-'--~~--'_-'---'_~_.l-

9

12

18 24

36 48

72

120

180

300

AGE (MONTHS)

Fig. 3. A. The relation between age at the time of repair and the size of the pulmonary valve ring relative to body surface area (aSA) expressed as (Z) in the 55 patients in the study group. Z(BSA) = -3.7 ± 0.94 + 0.69 ± 0.243 . In (age). The transformation to logarithm of age (In) was chosen because of the skewed age distribution. The relation is not a strong one (r = 0.36), but is statistically significant (p for intercept = 0.0002, P for slope = 0.006). Standard error of regression = 2.24. B, The same for the 38 patients undergoing primary repair, including the patient with the end-to-end anastomosis of right subclavian to right upper lobe pulmonary artery, which had never functioned. Z(BSA) = -3.5 ± 1.07 + 0.70 ± 0.311 . In (age). The relation is not a strong one (r = 0.35), but is a statistically significant one (p for intercept = 0.002; p for slope = 0.03). Standard error of regression = 2.12.

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The Journal of Thoracic and Cardiovascular Surgery

small tricuspid valve and hepatomegaly preoperatively. She died on the second postoperative day of low cardiac output. Discussion One limitation of this study is the fact that what is termed diameter of the pulmonary valve ring is determined by the size of the Hegar dilator that passes smoothly into the pulmonary artery after valvotomy and attempted release of the supravalvular narrowing. This is the result not only of the diameter of the true pulmonary valve ring or annulus, but also of residual valvular and supravalvular narrowing and of the configuration (bicuspid or tricuspid nature) of the pulmonary valve. The diameter measured in this way may be quite different from that measured by cineangiography with the circulation intact. The measurements of Rowlatt, Rimoldi, and Lev' were made at autopsy of normal hearts and possibly are still different. We presume, however, that the autopsy measurements are comparable to the measurements made at operation. Measurements have also been made in patients with tetralogy of Fallot by Lev, Rimoldi, and Rowlatt" at autopsy and by Zerbini? at operation. The results of our study are applicable only when the short vertical incision in the outflow tract of the right ventricle is closed with a patch. Otherwise, the slight narrowing resulting from the direct suturing of the incision plus the variable degree of hypoplasia of the infundibulum would probably produce higher PRV/LV than observed in this study. In fact, our present opinion is that use of a transverse incision would in some patients leave a higher PRv/ LV than would use of a vertical incision and infundibular enlargement with a patch'. Using the PRY/LV as the end point of repair is valid only when the surgeon knows by palpation or measurement that the distal pulmonary artery pressure is low. The systolic pressure gradient between the right ventricle and pulmonary artery is used by some, but this gradient is probably more dependent upon cardiac output (not known in this series in the operating room immediately after repair) than is PRY/LV. The insistence upon a PRv/Lv equal to or less than 0.65 as acceptable immediately after repair is controversial. Muraoka and colleagues" reported the result of operation in a group of 20 infants less than 2 years of age, in which noneunderwent patch-graft enlargement across the pulmonary valve ring, and the average PRY/LV at the end of operation was 0.69; 6 months to 5 years later no patient had a PRv/Lv greater than 0.6, and the average was 0.42. Their data suggest that the

pulmonary valve ring grew more rapidly after operation than did the aortic ring, and that in infants one can accept a PRY/LV higher than 0.65 immediately after repair. Other studies (including that of F. Fontan, personal communication) suggest that PRV/Lv late postoperatively is generally a little less than immediately after repair but that exceptions occur. 9-11 Certainly our experience has been that patients with PRV/LV greater than 0.65 but less than 1.0 immediately after repair without patch-graft enlargement survive the early postoperative period. Right or wrong, our concern has been that, under these circumstances, late postoperatively the PRV/Lv will be unduly high (>0.60) and that this will result in diminished exercise tolerance and symptoms. This study does not address the infrequent but important problem of stenoses at the origin of the left and/or right pulmonary arteries. When significant, special procedures directed toward them are required. This study confirms the idea that a small pulmonary valve ring, usually associated with marked underdevelopment of the infundibulum of the right ventricle, does not prevent adequate relief of the pulmonary stenosis in tetralogy of Fallot. The use of patch-graft enlargement by a proper technique, as part of the complete repair, reduces the right ventricular systolic pressure to acceptable levels unless there is stenosis at the origin of the left and right pulmonary arteries or marked hypoplasia of these arteries (Table VI). Past experience indicates that patch-graft enlargement across the ring by an improper technique does not always give a good result. When the pulmonary valve ring in the tetralogy of Fallot is the same or larger than the normal mean diameter, as it was in 17 (31 percent) of the 55 patients in this study, good relief of the pulmonary stenosis can be obtained by resection of the parietal bands and, where indicated, the septal bands; mobilization of the free wall of the right ventricle and, where necessary, pulmonary valvotomy; and release of supravalvular narrowing (Table VI). When the measured diameter is smaller than this mean normal value, the completeness of relief of the pulmonary stenosis (as evidenced by the PRY/LV) after repair without a patch across the ring decreases, as does the proportion of patients in whom an adequate relief of pulmonary stenosis can be obtained without such a patch (Tables VI to VIII). Thus we disbelieve Mercer's advice that a decrease in crosssectional area of the pulmonary valve ring up to 50 percent of normal may be considered acceptable; 12 he seems to have assumed, falsely, that the pulmonary valve ring is the only point of narrowing in tetralogy of

Volume 74 Number 3 September, 1977

Pulmonary stenosis in tetralogy of Fallot

~

39 I

.

Fig. 4. A, Prior to cardiotomy, measurements are made of the length of the incision if it is to be limited to the ventricle and its length if it is to be carried to the end of the pulmonary artery. When angiocardiography has shown some narrowing at the origi n of the left pulmonary artery , the incision is carried across this. B , A short verticle incision is made in the infundibulum of the right ventricle .

Fallot. There is no given pulmonary valve ring diameter above which a patch across the valve ring is never needed and below which PRV!LV is always greater than 0.65 after repair. without enlargement of the ring, so that a patch across the valve ring is always needed . We presume the reason a sharp cutoff point does not exist is that the measurements are not sufficientl y precise and that there is a somewhat independent variability in the precise pathological anatom y of the infundibulum, pulmonary valve, and supravalvular area. The proportion of patients undergoing patch-graft enlargement across the pulmonary valve ring is larger than that which we"- 13 have reported previously (Table IX). In part this may be related to the fact that in the

Table IX. Repair of tetralogy of Fallot in children ~4 years old Patch-graft enlargement across pulm onary valve ring

Years

No. of patient s

No .

1963-1964 * 1967-1968t Present study

90 63 25

15 12 9

I

% 17% 19% 36%

I

70% CL 13%-22% 14%-26% 25%-48%

Legend : p value for differences between 1963-1964 and present, 0.035; between 1967-1968 and present, 0.09. CL, Confidence limits. *Kirklin, Wallace, McGoon and DuShane". tKirkiin and Karp".

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Thoracic and Cardiovascular Surgery

CLOSURE OF VENTRICULOTOMY

Fig. 4. C, After the infundibular elements have been excised, the free wall of the right ventricle mobilized, the pulmonary valve opened, and the ventricular septal defect repaired, the twice preclotted Dacron tube is trimmed and sutured into the ventriculotomy incision. D, When the ventriculotomy incision has been extended across the pulmonary valve ring to the bifurcation of the pulmonary artery, a longer patch-graft is sutured into the entire area. Note that in both C and D the patch-graft has a convex contour both longitudinally and transversely to provide the largest possible pathway.

earlier experiences intracardiac repair was infrequently performed in patients younger than 4 years of age. The younger age group had a higher (but statistically not sign ificantly so) proportion of outflow patches in the present experience than did older patients , and Castaneda':' and Barratt-Boyes" have reported that a high proportion of their small infants were subjected to patch-graft enlargement across the pulmonary valve ring . This would be expected, in view of the tendency we have noted for the pulmonary valve ring to be more abnormally small the younger the child is when operation is required. However, probably the mo st important factor in the higher proportion of patients having patch-graft enlargement across the pulmonary valve ring in the present series of patients is our insistence that the PRV/LV be equal to or less than 0 .65 after repair; in the two earlier series, PRv/Lv equal to or less than 0.80 was accepted.

Also in contrast to results of many previous studies, the hospital mortality rate was no higher in those having patch-graft enlargement across the pulmonary valve ring than in the others. This may be related to the change in surgical technique. For many years we had done the repair through a transverse right ventriculotomy without placing a patch primarily across the valve ring unless it was obviously very small ; we had measured pressures after discontinuing cardiopulmonary bypass but with the cannulas still in place; and we had re-established bypass and inserted the patches when the PRY/LV indicated the need for this . The resulting I-shaped incision and the prolongation of cardiopulmonary bypass were undesirable features of this technique. Furthermore, it was particularly unattractive in small infants in whom the repair was done with the use of profound hypothermia and total circulatory arrest. Castaneda and colleagues" also

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September, 1977

have reported no increased hospital mortality rate with patch-graft enlargement across the ring. The study indicates that the size of the. pulmonary valve ring is correlated with the PRV/LV after repair without patch-graft enlargement across the valve ring. This size therefore should serve as a useful guide in making the decision for or against patch-graft enlargement across the ring. We have constructed Tables (IV and V) on the basis of these data, which relate the probability that PRv/Lv after repair will be greater than 0.65 (and thus that patch-graft enlargement across the pulmonary valve ring is probably necessary) to the normalcy of the diameter of the ring after valvotomy. These must be considered tentative because of the statistical nonsignificance of the relations in Fig. 2, presumably because of the relatively small size of the sample. At present, we use Table IV, because the fit of all the data in the study seems a little better when normalized to body surface area rather than to weight. After making a small vertical incision in the infundibulum of the right ventricle and doing the resection, mobilization, valvotomy, and release of supravalvular narrowing that may be required, we measure the internal diameter of the "pulmonary valve ring" by calibrated Hegar dilators. When it is the same as or larger than the mean normal value relative to the patient's body surface area (Table IV), the incision is not carried across the pulmonary valve ring; the ventricular septal defect is repaired, and a measured preclotted woven Dacron patch is used to close the ventricular incision (Fig. 4). After bypass is discontinued and before the cannulas are removed, PRV/Lv is measured. Generally (see below for exceptions) if the ratio is greater than 0.65, bypass is re-established and patch-graft enlargement is carried across the pulmonary valve ring and at least to the bifurcation of the main pulmonary artery. When the pulmonary valve ring diameter is found to be smaller than the 95 percent lower confidence limit of normal (Table IV), the primary incision is promptly carried across the valve ring and to the bifurcation of the pulmonary artery or, if necessary, on to the first part of the left pulmonary artery; after the ventricular septal defect has been repaired, a measured preclotted woven Dacron patch is inserted to widen the entire area (Fig. 4). The patch is made from a woven Dacron tube whose diameter is about that of the high 95 percent confidence limit of normal for that patient. When the ring is smaller than the mean normal value but within its 50 percent confidence limits, the chance is about 35 percent that a patch across the pulmonary valve ring will be required for the PRV/LV to be equal to or less than 0.65 after repair. If the valvotomy has seriously compromised the competence of the pulmo-

nary valve, there is little additional disadvantage to the patch-graft enlargement across the ring, and it may as well be done primarily. If the operation is in a small infant and is done with a single venous cannula, profound hypothermia, and total circulatory arrest, one may wish to insert a patch across the ring primarily even with these odds. In patients in whom the pulmonary valve appears to be well developed, pliable, and competent after valvotomy, one may wish not to carry the reconstruction across the ring primarily with only this 35 percent chance, but rather to wait and do so only after measuring pressures after having completed the repair and temporarily discontinued bypass. In infants with such a good pulmonary valve, one might accept a PRV/LV somewhat higher than 0.65 after repair in view of Muraoka's data. If the ring is still smaller than this but within the 72.5 percent confidence limits, the chances are about 50 percent that a patch across the ring will be required; if it is below this but within the 95 percent confidence limit, the chances are about 75 percent. In older patients or again in those whose pulmonary valve appears to be well developed and competent, one might not place the patch across the valve ring primarily even in these circumstances, doing so only if the PRV/LV immediately after discontinuing bypass is greater than 0.65; in others in these categories, primary patch-graft enlargement across the ring may be elected. We appreciate being able to include the patients whose operations were done by our colleagues, Dr. Nicholas T. Kouchoukos and Dr. RobertB. Karp. We are indebted to Ms. Sandy O'Brien for editorial and art work. We acknowledge the helpful criticisms of Sir Brian Barratt-Boyes. REFERENCES Rowlatt, U. F., Rimoldi, H. J. A., and Lev, M.: The Quantitative Anatomy of the Normal Child's Heart, Pediatr. Clin. North Am. 10: 499, 1963. 2 Venugopal, P., and Subramanian, S.: Intracardiac Repair of Tetralogy of Fallot in Patients Under 5 Years of Age, Ann. Thorac. Surg. 18: 228, 1974. 3 Dobell, A. R. C., Charrette, E. P., and Chughtai, M. S.: Correction of Tetralogy of Fallot in the Young Child, J. THORAc. CARDIOVASC. SURG.

55: 70, 1968.

4 Blackstone, E. H., Kirklin, J. W., Bradley, E. L., DuShane,1. W., and Appelbaum, A.: Optimal Age and Results in Repair of Large Ventricular Septal Defects, J. THORAc. CARDIOV ASC. SURG.

72: 661, 1976.

5 Blackstone, E. H., Kirklin, J. W., Pluth, J. R., Tumer, M. E., and Parr, G. V. S.: The Performance of the Braunwald-Cutter Aortic Prosthetic Valve, Ann. Thorac. Surg. 23: 302, 1977. 6 Lev, M., Rimoldi, H. J. A., and Rowlatt, U. F.: The Quantitative Anatomy of Cyanotic Tetralogy of Fallot, Circulation 30: 531, 1964.

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7 Zerbini, E. J.: The Surgical Treatment of the Complex of Fallot: Late Results, J. THoRAc. CARDIOV ASC. SURG. 58: 158, 1969. 8 Muraoka, R., Yokota, M., Matsuda, K., Tabota, R., and Hikasa, Y: Long-Term Hemodynamic Evaluation of Primary Total Correction of Tetralogy of Fallot During the First Two Years of Life. Arch. Jpn. Chir. 42: 315, 1973. 9 Kirklin, 1. W., and Karp, R. B.: The Tetralogy of Fallot From a Surgical Viewpoint, Philadelphia, 1970, W. B. Saunders Company. 10 Hawe, A., Rastelli, G. C., Ritter, D. G., DirShane, J. W., and McGoon, D. c.: Management of the Right Ventricular Outflow Tract in Severe Tetralogy of Fallot, J. THORAc. CARDIOVASC. SURG. 60: 131, 1970. II Hawe, A., McGoon, D. c., Kincaid, O. W., and Ritter, D. G.: Fate of Outflow Tract in Tetralogy of Fallot, Ann. Thorac. Surg. 13: 137, 1972. 12 Mercer, J. L.: Acceptable Size of the Pulmonary Valve Ring in Congenital Cardiac Defects, Ann. Thorac. Surg. 20: 567, 1975. 13 Kirklin, J. W., Wallace, R. B., McGoon, D. c., and DuShane, 1. W.: Early and Late Results After Intracardiac Repair of Tetralogy of Fallot: 5- Year Review of 337 Patients, Ann. Surg. 162: 578, 1965. 14 Castaneda, A. R., Williams, R. G., Rosenthal, A., and Sade, R. M.: Tetralogy of Fallot: Primary Repair in Infancy, in Kidd, B. S. L., and Rowe, R. D., editors: The Child With Congenital Heart Disease, Mount Kisco, N. Y., 1976, Futura Publishing Company, Inc., p. 63. 15 Barratt-Boyes, B. G.: Primary Definitive Intracardiac Operations in Infants: Tetralogy of Fallot, in Kirklin, J. W., editor: Advances in Cardiovascular Surgery, New York, 1973, Grune & Stratton, Inc., p. 155.

Discussion DR. DWIGHT C. McGOON Rochester. Minn.

It seems highly desirable that every effort be made to objectify some of these decisions now made on subjective bases, such as when to patch-graft across the pulmonary annulus. Certainly Dr. Pacifico, Dr. Kirklin, and Dr. Blackstone have made an important contribution in this regard. In fact, I am having a copy of their table prepared for ready reference in the operating room. However, I think we must realize that they are only attempting to make a start in this direction. Indeed, in the borderline cases in which objectivity would be most useful, we find some subjectivity remaining in the protocol presented: Whether or not the valve has been rendered incompetent by the valvotomy, whether or not it appears that the patient's annulus might grow as related to the age of the patient, and whether it would be a burden to return to bypass or not after measuring the R V/L V ratio, all influence the decision. I have two questions: I wonder how important it is to avoid an outflow tract patch across the annulus in these borderline

Thoracic and Cardiovascular

Surgery

cases when it has been necessary in most instances to virtually destroy the valve in order to obtain an adequate valvotomy. In a recent analysis of early patients at the Mayo Clinic with follow-up up to 13 years, use of an outflow patch was among those conditions that seemed to make no difference in the late postoperative clinical course. This has led us to be rather liberal in the eval uation of whether or not to patch in the borderline situation. The next question relates to the fact that about one third of our patients have had thin-walled, well-developed outflow tract chambers, with little or no valvular stenosis. This type of anatomy has been readily repaired by resection of the limbs of the crista without the use of a patch even up to the annulus. I noticed that the authors used patches in the ventriculotomy in all of their patients up to the annulus. I wonder if they have not encountered this type of anatomy in their patients or whether they are recommending an outflow tract patch up to the annulus in all patients regardless of this anatomy. DR. FRANK GERBODE San Francisco. Calif.

Throughout the years we have been impressed with the work of Dr. Kirklin's group in this and other fields and with their numerous efforts to make things more scientific and operated reliable. I would suggest that most of the patie~ts upon by that group and by Dr. Castaneda had pulmonary arteries large enough to accept an adequate and full cardiac output after repair. However, there is a group of patients with very narrow pulmonary arteries and, in some, a complete atresia of the main pulmonary artery in whom it would be foolish to try a complete repair. In such cases we have a decision of whether or not to do a shunt operation or some other operation. About 13 years ago we treated five such patients. We elected to try a two-stage operation-doing a patch procedure on the outflow tract first and waiting to see if the pulmonary vascular bed would eventually accept a complete cardiac output resulting in a left-to-right shunt instead of a right-to-left shunt. Within a year, three of these patients had enlargement of the main pulmonary arteries, and left-to-right shunts developed. We then closed the ventricular septal defects. Two other patients are still in a balanced shunt state. They are now grown adults and are doing pretty well. They have been greatly improved by the patch in the outflow tract, but the pulmonary vascular bed is still unable to accept full output. I wish to suggest that a two-stage operation might be used in some instances in which this anatomic configuration exists. DR. ROBERT L. REPLOGLE Chicago. l/l.

The results of Drs. Starr, McGoon, and Castaneda reveal that the operative risk in the management of the patient with tetralogy of Fallot has been reduced to a very low figure in competent hands. Dr. Pacifico has addressed himself to what we all perceive as a potential long-term problem: that is, whether or not the patient with residual right ventricular outflow obstruction is better off than the patient with pulmonary

Volume 74 Number 3 September,19n

insufficiency. I had always thought that the decision as to whether to accept stenosis or insufficiency could be made at the time of operation; one could either enlarge the annulus with a pericardial or Dacron patch or accept some residual obstruction and thereby avoid pulmonary insufficiency. Last fall at the meeting of the American Heart Association my colleagues and I presented our postoperative results in 50 patients with tetralogy of Fallot in whom we quantitated pulmonary insufficiency by measuring the right ventricular stroke volume and the left ventricular stroke volume. By subtracting the left ventricular from the right ventricular stroke volume, one can derive quantitative measurements of pulmonary insufficiency. Somewhat to my surprise, we found that there was no difference in the incidence of pulmonary insufficiency or the quantitation of pulmonary insufficiency in those patients who had received transannular patches and those that had not. This certainly destroyed the shibboleth that I had carried around for many years. Dr. Pacifico, in your study, do patients who are left with an intact annulus indeed have less pulmonary insufficiency than the patients who have had a transannular patch? I am concerned that one might leave a somewhat stenotic annulus intact, hoping to avoid pulmonary insufficiency, and wind up with both a residual gradient and pulmonary insufficiency. DR. PAC I Fie 0 (Closing) I would like to thank each of the discussers for their comments. Dr. McGoon asked whether or not it is important to avoid an outflow patch if the valve is destroyed. We believe that, if the valve will not remain competent after valvotomy, there is no significant difference if a patch is placed across the annulus. In this situation we would use the mean normal value of the measured valve annulus as the minimum accepted.

Pulmonary stenosis in tetralogy of Failot

395

Regarding the use of a patch in the infundibulotomy, we believe that it is preferable to make a verticle incision in the right ventricle. If a primary transverse incision is made and primary or secondary enlargement across the valve ring is then required, the result will be an inverted T-shaped incision. If the verticle incision is closed primarily without a patch, some further narrowing of the infundibular chamber probably will occur. These are the reasons that we use a verticle incision and a patch within it. We would not use this technique in a patient with a low-lying infundibular pulmonic stenosis. A higher proportion of patients with tetralogy of Fallot and subpulmonary ventricular septal defect require patching across the valve annulus, because during closure of the ventricular septal defect the valve annulus may become further narrowed. Therefore, directly measuring it after repairing the defect seems advisable. I appreciate Dr. Gerbode's comments. We agree that a two-stage management program is advisable for patients with distal pulmonary artery hypoplasia. One could also employ Dr. Castaneda's suggestion: that is, closing the ventricular septal defect with a perforated Dacron patch. Dr. Replogle mentioned that there is no difference in the degree of pulmonary incompetence in those patients having a patch across the valve annulus and in those who did not have a patch across the valve annulus. The pulmonary valve is stenotic in approximately 60 or 65 percent of patients with the tetralogy, and relieving the valvular stenosis directly may result in an incompetent valve in some patients. In those cases we would not believe it necessary to leave the valve annulus intact.