Modified Blalock-Taussig shunt in newborn infants

J

THoRAc CARDIOYASC SURG

88:770-775, 1984

Modified Blalock-Taussig shunt in newborn infants The modified Blalock-TalBSig shunt, interposing an expanded polytetrafluoroethylene graft betweenthe subclavianand puJmonary arteries, was performedin 30 neonates with a mean age of 8.8 days anda mean weight of 3.14 kg. Underlying lesiOiti included severe tetralogy of Fallot or its variant (N = 10), transposition complex (with pulmonary stenosis or atresia) (N = 6), single ventricle equivalents (with puImonary atresia or stenosis)(N = 9), and puJmonary atresia with intact ventricularseptum (N = 5). The mean preoperative arterial oxygen tension prior to prostaglandin E 1 therapy was 29.5 torr. The shunt was performed through a right thoracotomy in 18 patients, through a left thoracotomy in nine, and through a median sternotomy in three. A 5 mm graft was used in 21 patients anda 6 mm graft in nine patients. The mean postoperative arterial oxygen tension was 64.1 torr (p < 0.001). The incidence of early shunt occh6ion was 3.3 % and the hospital mortality was 3.3 %. Actuarial functional life of the shunt (110 death or reoperation related to shunt failure)was 91 % at 3 years' follow-up. Nine patients were recatheterized. There was 110 distortion of the pulmonary artery. The ratios of the diameter of the right puJmonary artery and puJmonary valve anulus to that of the descending aorta increased after the operation by 50 % (p < 0.001) and 52% (p < 0.05),respectively. Our experienceindicates that the modified Blalock-TalBSig shunt has an excellent function, offers several technical advantages, and lacks most of the drawbacks of other systemic-pulmonary artery shunts. It may be the shunt of choice in patients less than 1 month of age.

Michel N. Ilbawi, M.D., John Grieco, M.D., Serafm Y. DeLeon, M.D., Farouk S. Idriss, M.D., Alexander J. Muster, M.D., Teresa E. Berry, M.D., and Janice Klich, M.D., Chicago. Ill.

Each of the systemic-pulmonary artery shunt procedures previously proposed for the treatment of newborn infants with cyanotic heart disease has characteristic disadvantages. The Potts shunt has been abandoned in most centers, as it is usually associated with excessive flow and pulmonary hypertension 1,2 and is difficult to take down at corrective operation. The Waterston shunt has been advocated because of a high percentage of patency in the neonate,' but congestive heart failure (due to excessive pulmonary blood flow), marked preferential flow to the ipsilateral lung, and pulmonary artery branch distortion are its particular drawbacks.' Elevated pulmonary vascular resistance in the newborn From the Divisionsof Cardiovascular-Thoracic Surgery and Cardiology, Children's Memorial Hospital, and the Departments of Surgery and Pediatrics, Northwestern University Medical School, Chicago, Ill. Supported in part by the A. C. Buehler Foundation, Park Ridge, Ill. Received for publication Nov. 17, 1983. Accepted for publication Jan. 20, 1984. Address for reprints: Michel N. Ilbawi, M.D., Division of Cardiovascular-Thoracic Surgery, Children's Memorial Hospital, 2300 Children's Plaza, Chicago, Ill. 60614.

770

period and small vessel size contraindicate use of the Glenn anastomosis.' Limitations of the Blalock-Taussig shunt" in newborn infants include kinking of the subclavian artery at its origin, pulmonary artery tenting, ischemic sequelae to the ipsilateral upper Iimb.?-" and frequent early occlusion."10 Recently, the modified Blalock-Taussig shunt, interposing expanded polytetrafluoroethylene (PTFE) graft between the subclavian and pulmonary arteries, has evolved in an attempt to utilize the advantages and reduce the disadvantages associated with other systemic-pulmonary artery shunts. This report reviews our experience with the modified Blalock-Taussig shunt in neonates and illustrates its merits over other shunts in this age group.

Patients and methods Thirty neonates underwent modified Blalock-Taussig shunts at the Children's Memorial Hospital from September, 1980, to October, 1983. Mean age was 8.8 days (range 1 to 30 days); mean weight, 3.14 kg (range 1.9 to 4.6 kg). Twenty boys and 10 girls constituted this group. Underlying congenital cardiac lesions included severe tetralogy of Fallot or its variants (N = 10),

Volume 88 Number 5 , Part 1

Modified Blalock-Taussig shunt 771

November. 1984

PT: [, pros hem Subclavtan a I

:

I

I I

I

I

I

I

,1nnommal£a

I"

A

D B

c

Fig. 1. The technique of performing the modified BlalockTaussig shunt through a lateral thoracotomy (A). The vessels were isolated (8). The subclavian artery is clamped and an arteriotomy is made (C).

transposition complexes (with pulmonary atresia or stenosis) (N = 6), single ventricle equivalents (with pulmonary atresia or stenosis) (N = 9), and pulmonary atresia with intact ventricular septum (N = 5). Initial arterial oxygen tension (with variable inspired oxygenconcentrations) ranged from 16 to 59 torr (mean 32.1 torr). Preoperatively, the patients were started on prostaglandin E. (0.05 to 0.1 ~g/kg/min) infusion to assure ductal patency and improve pulmonary blood flow. All patients were operated upon on an urgent basis. The shunt was performed through a right thoracotomy ip 18 patients, a left thoracotomy in nine, and through a median sternotomy in three. At operation, estimates of pulmonary artery and sulx:lavian artery sizes at the site of the anastomosis averaged 4.1 mm and 2.9 mm, respectively. PTFE grafts" were interposed between the sulx:lavianand pulmonary arteries in all patients; 6 mm *w. L. Gore Ariz.

& Associates, Inc., Elkton, Md ., or Impra, Inc., Tempe ,

E.

Fig. 1. Cont'd. Multiple stitches are placed in the artery and the graft before the latter is lowered into the chest (D). The graft-pulmonary artery anastomosis is then completed (E). PTFE. Polytetrafluoroethylene.

grafts were used in nine patients and 5 mm grafts in 21 patients. Early in our experience, the 6 mm graft was preferred. However, more recently, after a preliminary evaluation of our initial results, we have used the 5 mm graft in most newborn patients. Nine patients underwent cardiac catheterization from 12 to 19 months (mean 14.7 months) postoperatively. Biplane cineangiocardiograms were reviewed for shunt patency, graft kinking, pulmonary artery distortion, and anastomotic narrowing. The relative sizes of the pulmonary arteries and pulmonary valve anulus were estimated by the ratio of the diameter of the right pulmonary artery (immediately prior to its lobar branching) or the pulmonary anulus to the diameter of the descending aorta (above the diaphragm) on the same frame of the cineangiogram. These ratios were then compared to similar measurements made at the patient's preoperative catheterization to determine the contribution of the shunt to the growth of the pulmonary vascular tree.

The Journal of Thorac ic and Cardiovascular Surgery

7 7 2 Ilbawi et al.

lnoormnetc v

;

p
64

~j " 4.

0

a...

.-=0

.l!! ~

32

I

tic 1:1 r

I

I

,

"

i111:' nJIYa

,

Before Shunt

I

After Shunt

I

Pl IT pr

sth sis I

Fig. 2. The technique of performing the modified shunt through a median sternotomy. Superior traction on the innominate vein and caudad and leftward traction on the innominate artery facilitate exposure of the subclavian artery.

Operative technique. The pulmonary and subclavian arteries are dissected as for a classical Blalock-Taussig shunt (Fig. 1). A vessel loop is passed around the subclavian artery and pulled inferiorly to isolate a segment of the vessel with a side-biting clamp. Care is taken to avoid injury to the recurrent and vagus nerves. A longitudinal arteriotomy is made as proximally as possible to ensure utilization of the subclavian artery at its widest diameter. An obliquely trimmed PTFE tube graft is anastomosed to the subclavian artery end to side with continuous polypropylene suture. Multiple stitches are placed in the trimmed end of the graft and in the subclavian artery before the graft is lowered into the chest and the suture tightened (Fig. 1). This technique improves exposure and prevents any distortion of these small vessels. The other end of the graft is anastomosed to the proximal portion of the pulmonary artery by the same suturing technique. The vascular clamp is left on the subclavian artery until the pulmonary artery anastomosis is completed, to avoid trauma to the graft by the clamp, or blood stasis within it and subsequent clotting. No intravenous heparin is given. The azygos vein is

Fig. 3. Improvement in arterial oxygen tension (Po}) following construction of the modified shunt.

ligated and divided whenever the procedure is performed on the right side to facilitate the takedown of the shunt at the time of the corrective operation. In patients in whom the median sternotomy approach is used, the subclavian artery is exposed by cutting the ·pericardial reflection at the base of the innominate artery and passing a vessel loop around it. Delicate caudad and leftward traction on the loop facilitates exposure of the subclavian artery, which can then be readily isolated and clamped (Fig. 2). Results The mean postoperative arterial oxygen tension in room air was 64.1 torr (range 50 to 92 torr) (p < 0.(01) (Fig. 3). Early graft thrombosis occurred in one patient (3.3%) 12 hours after operation and necessitated replacement of a 5 mm PTFE graft with a 6 mm graft. There were no intraoperative deaths. One patient died 5 days postoperatively of Escherichia coli sepsis, for a hospital mortality of 3.3%. All patients were followed up for 2 to 37 months postoperatively. There were no instances of late occlusion of the shunt. Twenty-three patients are doing well, with no recurrence of cyanosis or increase in hematocrit value. Two patients with severe tetralogy of Fallot and hypoplastic pulmonary arteries, in whom the initial shunts (both patent) were performed with 6 mm grafts,

Volume 88 Number 5, Part 1 November, 1984

100 c

.Q

U c

tt 75 o'" ::>

Modified Blalock-Taussig shunt

---T-- ......--...... ---+---1---~--~--

~;·2i·T "'_.._..__._.._

..... --~--

1.20 0

_.._ _ .

_.._ _ _

78%32

c: u '"

s

L10

~0

100

«

50

0>

c

090

'0

c Ql u

..---- 5mm Groft ......_.._.... 6mm Groft

~

!l!

C

0::

CT

'"
."

773

25

If)

~ E

::>

080

»,

E

a 4

8

12

16

20

24

28

32

36

40

Months After Surgery

Fig. 4. Actuarial functional life curve of the modified shunt in this series (no death or second operation related to inadequate shunt function). Note that the functional life of the 5 mm graft was better than that of the 6 mm graft. The difference is not statistically significant. The numbers with small arrows indicate the percent value ± 95% confidence limits.

required a subsequent shunt on the opposite side 7 months and 9 months postoperatively because of increasingcyanosis.Two patients had moderately severe congestive heart failure after the shunt procedure; one (with 5 mm graft) responded to medical treatment, but the other (with 6 mm graft) needed banding of the subclavian artery proximal to the shunt to control the failure. The cumulative percent of adequate shunt function (no death or second operation related to shunt failure) in this series was 91% at 3 years' follow-up. The 5 mm graft had a better actuarial functional life than the 6 mm graft, but the difference was not statistically significant (Fig. 4). There were three late deaths unrelated to the shunt. Two of the three patients had asplenia syndrome and pulmonary atresia, with cyanosis recurring 3 to 4 months after the shunt operation despite adequately functioning shunts. Repeat catheterization revealed obstructed total anomalous pulmonary venous drainage, which was not appreciated preoperatively because of inadequate pulmonary blood flow. Both patients died after attempts at repair of the anomalous venous drainage. The third patient had tetralogy of Fallot and absent pulmonary valve syndrome. Ligation of the main pulmonary artery and a left modified Blalock-Taussig shunt were performed as described by Byrne and associates. 11 The patient died 3 months later of unrelieved severe bilateral pulmonary emphysema. Graft patency was demonstrated in all nine patients who were recatheterized. Graft kinking or pulmonary

2!

070

6c

060

.a>0

E

"3

050

n,

1:

.2' 0::

040

l'

i

I

Before Shunt

After Shunt

Fig. 5. Changes in pulmonary artery size produced by the shunt in nine patients. Large circles, Patients with 6 mm graft. Small circles, Patients with 5 mm graft.

190 1.80 170 .2 C a:: 1.60 .E 1.50 ~ 140 0> c; 1.30 'C c 120 u '" gj 1.10 0 2 100 090 2 ::> c 080 c « 070 » 6c 060 0 E 050 'S 0.. 040 lJ)

p
I

l' Before Shunt

i

After Shunt

Fig. 6. Changes in pulmonary valve anulus size produced by the modified shunt. Large circles, Patients with 6 mm graft. Small circles, Patients with 5 mm graft.

artery distortion were not present, and the blood flow through the shunt, as judged by cineangiographic examination, was equally distributed to both lungs. The ratio of the right pulmonary artery to descending aorta diameter increased from 0.65 ± 0.12 to 0.98 ± 0.14

774

The Journal of Thoracic and Cardiovascular Surgery

Ilbawi et al.

(II)

(5)

c

(7)

(4) (4)

......................

2 u

c

t.i:., 75 "6 :::>

c.,

-c


C

50

s cf.,

•

•

Present Series Modified B- T shunt in neonates ..................... Edmunds et 01 Classical B-T shunt in neonates 0 - - - - - - 0 Guyton et 01 Classical B - T shunt in all age groups

> 25 .-§ -s

E :::> u

4

8

12

16

20

24

28

32

36

40

Months After Surgery

Fig. 7. Comparison of the actuarial functional life of the modified Blalock-Taussigshunt in this series with that of the classical shunt reported by Edmunds," Guyton," and their associates. The modified shunt has a better long-term result. The numbers in parentheses are the number of patients followed. The numbers with arrows indicate the percent value ± 95% confidence limits.

(p < 0.(01) or 50% (Fig. 5), and the ratio of the pulmonary valve anulus to descending aorta diameter increased from 0.75 ± 0.21 to 1.14 ± 0.41 (p < 0.05) or 52% (Fig. 6). The increase of these ratios in patients with 5 mm grafts was not statistically different from that increase noted in patients with 6 mm grafts. Discussion Klinner, Pasini, and Schaudig," prompted by the limitations of the original Blalock-Taussig shunt, interposed a graft between the subclavian and pulmonary arteries. Subsequently, several centers have used this technique with good results. BoIS Most of the reported experiences, however, have been in older infants and children, and little is mentioned concerning shunt performance in patients less than 1 month of age. Our experience clearly demonstrates the advantages of the modified shunt in neonates. Hemodynamically, the modified shunt uses the concept of inflow regulation by the subclavian artery; that is, the blood flow through the shunt is limited by the diameter of the artery, so that large diameter grafts (5 or 6 mm) can be used while at the same time the lungs are protected from overperfusion. The use of such relatively large grafts without the fear of resultant heart failure is particularly advantageous in newborn infants for two reasons: 1. The incidence of acute thrombosis is significantly decreased. In this series, the 3.3% incidence of early shunt occlusion compares favorably with the 19% to 22% incidence reported in neonates with classical Blalock-Taussig shunts.v"

2. It provides the potential for the shunt flow to increase with growth of the patient and enlargement of the vessel. This accounts for the excellent long-term results of the modified shunt. Its actuarial functional life, 91% in this series, is better than most of those reported for the classical shunt in this age group 10. 16 (Fig. 7). The modified shunt has several additional advantages. By preserving the integrity of the subclavian artery, it avoids acute and chronic ischemic sequelae to the upper extremity reported following the classical Blalock-Taussig shunt.?" It also allows for the use of the subclavian artery on the ipsilateral side of the aortic arch without fear of kinking the artery at its origin, as might occur if primary subclavian-pulmonary artery anastomosis were performed on that side. This may be especially important in patients in whom the preferential blood flow to one pulmonary artery or the anatomy of the ductus arterious precludes the use of the vessel on the contralateral side of the arch. However, if these or other limitations are not present, we prefer to use the right subclavian artery for construction of the modified shunt because of the ease of takedown at the time of definitive repair. Another advantage of the modified shunt is in neonates with a short subclavian artery. The classical Blalock-Taussig shunt, if performed in this group of patients, can result in distortion of the pulmonary artery branches and tension on the anastomotic site, leading to narrowing and inadequate pulmonary blood flow. Occasionally, the need may arise for performing a

Volume 88 Number 5, Part 1 November, 1984

systemic-pulmonary artery shunt simultaneously with an intracardiac procedure through a median sternotomy. In the past, the Waterston-Cooley shunt or a direct graft interposition between the ascending aorta and the pulmonary artery has been used in this situation. However, the Waterston-Cooley shunt may result in distortion of the pulmonary arteries, congestive heart failure, pulmonary vascular disease, or preferential blood flow to one lung. Similarly, a direct graft between the aorta and pulmonary artery may produce congestive heart failure and has a high incidence of thrombosis. The technique described in this report provides an alternative that combines the advantages of the modified Blalock-Taussig shunt with the feasibility of performing the procedure through a median sternotomy and the ease of taking the shunt down at the time of total repair. The contribution of the systemic-pulmonary artery shunt to the growth of the pulmonary arterial tree is an important parameter of its function and can be assessed by the ratio between the diameter of the branch pulmonary arteries and the descending aorta. In restudying six patients with PTFE graft shunts during the neonatal period, McKay and associates" reported a mean increase in this ratio of 28% for the right pulmonary artery and 32% for the left pulmonary artery. Our results in the nine patients who underwent postoperativecatheterization were similar. Enlargement of the pulmonary arterial tree and pulmonary valve anulus was present in all. In conclusion, the modified Blalock-Taussig shunt in the neonate offers low risk, excellent short- and longterm results, and has several technical advantages. It may be the shunt of choice in the newborn period. REFERENCES Neches WH, Naifeh J, Park SC, Lenox CC, Zuberbuhler JR, Siewers RD, Pontius RG, Bahnson HT: Systemicpulmonary artery anastomosis in infancy. J THORAC CARDIOVASC SURG 70:921-927, 1975 2 Truccone NJ, Bowman FO Jr, Maim JR, Gersony W: Systemic-pulmonary arterial shunts in the first year of life. Circulation 49:508-516, 1974 3 Stewart S, Mahoney EB, Manning J: The Waterston anastomosis with no deaths in the neonate. J THORAC CARDIOVASC SURG 72:588-592, 1976 4 Idriss FS, Cavallo CA, Nikaidoh H, Paul MH, Koopot R,

Modified Blalock-Taussig shunt

775

Muster AJ: Ascending aorta-right pulmonary artery shunt. J THORAC CARDIOVASC SURG 71:49-57, 1976 5 Willman VL, Barner HB, Mudd JG, Fagan LF, Kaiser GC: Superior vena cava-pulmonary artery anastomosis. J THORAC CARDIOVASC SURG 67:380-386, 1974 6 Blalock A, Taussig H: Surgical treatment of malformations of the heart in which there is pulmonary stenosis or pulmonary atresia. JAMA 128:189-202, 1945 7 Mearns AJ, Deverall DB, Kester RC: Revascularization of an arm for incipient gangrene after the Blalock-Taussig shunt. Br J Surg 65:467-468, 1978 8 Skovranek J, Goetzova A, Sahavek M: Changes in muscle blood flow and development of the arm following the Blalock-Taussig anastomosis. Cardiology 6:131-137, 1975 9 Laks H, Fagan L, Barner HB, Willman VL: The BlalockTaussig shunt in the neonate. Ann Thorac Surg 25:220224, 1978 10 Edmunds H, Stephenson LW, Gadzik JP: The BlalockTaussig anastomosis in infants younger than one week of age. Circulation 62:597-603, 1980 11 Byrne JP, Hawkins JA, Battiste CE, Khoury GH: Palliative procedures in tetralogy of Fallot with absent pulmonary valve. A new approach. Ann Thorac Surg 33:499502, 1982 12 Klinner W, Pasini M, Schaudig A: Anastomose zwichen System und Lungenarterie mit Hilfe von Kunststoffprothesen bei cyanotischen Herzirtien. Thoraxchirurgie 10:68-75,1962 13 de Leval MR, McKay R, Jones M, Stark J, Macartney FJ: Modified Blalock-Taussig shunt. J THORAC CARDIOVASC SURG 81:112-119, 1981 14 Lawless CE, Smith EEl, Hallidie-Smith K, Sapsford RN: The modified Blalock-Taussig shunt using microporous expanded polytetrafluoroethylene (PTFE). J Cardiovasc Surg 23:287-292, 1982 15 Donahoo JS, Gardner TJ, Zahka K, BSL: Systemicpulmonary shunts in neonates and infants using microporous expanded polytetrafluoroethylene. Immediate and late results. Ann Thorac Surg 30: 146-150, 1980 16 Guyton RA, Owens JE, Waumett JD, Dooley KJ, Hatcher CR, Williams WH: The Blalock-Taussig shunt. Low risk, effective palliation, and pulmonary artery growth. J THORAC CARDIOVASC SURG 85:917-922,1983 17 McKay R, de Leval MR, Rees P, Taylor JFN, Macartney FJ, Stark J: Postoperative angiographic assessment of modified Blalock-Taussig shunts using expanded polytetrafluoroethylene (Gore-Tex). Ann Thorac Surg 30:137145, 1980