Optimal Flow of Aorta-Pulmonary

Transcription

1 Optimal Flow of orta-pulmonary rtery Shunt in Patients with Cyanotic Heart Disease Kenji Kusuhara, M.D., Shigehito Miki, M.D., Yuuichi Ueda, M.D., Yutaka Ohkita, M.D., Takafumi Tahata, M.D., and Masashi Komeda, M.D. STRCT n aorta-pulmonary artery shunt with an expanded polytetrafluoroethylene (Gore-Tex) tube graft (3 to mm in diameter) was done in 33 cyanotic patients with complex congenital heart disease. The patients ranged from 1 days to 22 years old. n 28, the shunt flow (Q,) was measured, and the optimal Q, and graft size were determined. Nine patients had severe heart failure because of an excessively large shunt. Seven of these patients died, early and 2 late after operation. The Q,s in these 9 patients were extremely high; the Q, index and the ratio of shunt flow to systemic flow (Q/QJ were 3.8 f 0.91 L/min/m2 (mean f standard deviation) and 2. f 9.7, respectively. The Q, index and the QJQ, of patients without severe cardiac failure were 1.9 f 0.92 Llminlm and 27.2 f 11., respectively. n conclusion, the Q. index, the QJQ,, or both should be maintained in the range of 1. to 2. L/min/m2 and 30 to 0, respectively. n infants, however, it is advisable to control the flow at less than the range just given. nalysis of graft size in relation to body weight (W, in kilograms) and body surface area (S, in square meters) showed that the optimal diameter (D, in millimeters) could be calculated by the following formulas: D = 1.88 ln(w) (r =.8) D = 0.87 ln(s) +.3 ( =.73) n aorta-pulmonary artery shunt as a palliative operation for cyanotic patients with diminished pulmonary blood flow has the advantages of providing sufficient bilateral blood flow allowing selection of a suitable graft size, and yielding even growth of both pulmonary arteries [l]. However, the procedure may be associated with a relatively high mortality because of a large shunt. We measured shunt flow (Q,) in the operating room with an electromagnetic flowmeter to investigate the optimal value of Q, the determinant factors of flow, and the appropriate graft size of the shunt. From the Division of Cardiovascular Surgery, Tenri Hospital, Tenri City, Nara, Japan. ccepted for publication Dec 12, 198. ddress reprint requests to Dr. Kusuhara, Division of Cardiovascular Surgery, Tenri Hospital, 200 Mishimacho, Tenri City, Nara, Japan 32. Material and Methods From January, 1979, to December, 198, 33 cyanotic patients with congenital heart disease underwent an aortapulmonary artery shunt with an expanded polytetrafluoroethylene (PE) (Gore-Tex) tube graft. There were 20 male and 13 female patients ranging in age from 1 days to 22 years (mean,.82 years) and in weight from 3.3 to 8 kg (mean, 17.3 kg). rterial oxygen saturation (SaOz) ranged from 37. to 8 (mean, 8.). Eight of the patients had undergone previous shunt operation. The patients were divided by postoperative course into those without congestive heart failure (Group ) and those with congestive heart failure (Group ) (Table). The operative procedure was a central shunt from the aorta to the main pulmonary artery in 30 patients (Fig 1-C) and to the right pulmonary artery in 3 (Fig 1D). graft 3 mm in diameter was used in 3 patients, mm in 7, mm in 1, and mm in 9. Cardiopulmonary bypass was used in 17 patients who could not tolerate clamping of the pulmonary artery during the anastomosis. Continuous suture of -0 polypropylene for the distal anastomosis of the graft and -0 or -0 polypropylene for the proximal anastomosis was used. n 28 patients, the Q, was obtained either by measuring with an electromagnetic flowmeter or by subtracting the flow of the aorta distal to the graft (Q,,) from the flow of the aorta proximal to the graft (Q,) (Fig 2). efore the flow study, the air in the microporous structure of the graft wall was flushed out with saline solution to obtain electric conductivity immediately after anastomosis. This procedure is essential for measuring flow in an expanded PE graft with an electromagnetic flowmeter. Results The 2 patients in Group (without severe congestive heart failure) had a smooth postoperative course except for 2, 1 of whom died accidentally of airway obstruction (Patient 9) and 1 who died of hypoxia because of underdevelopment of the pulmonary artery (Patient 11) (see Table). Conversely, the 9 patients in Group sustained severe congestive heart failure. Two of them (Patients 28 and 32) had a severe low cardiac output state caused by an excessively large shunt. There were early deaths, and 2 late deaths in this group including 1 due to infection (Patient 27). Overall early mortality was 21, and of the early deaths occurred in patients less than 1 year of age. Graft banding was added in 3 patients. One (Patient 21 in Group ) who underwent a central shunt with a nn Thorac Surg :128-13, ug 1987

2 129 Kusuhara, Miki, Ueda, et al: Optimal Flow of orta-pulmonary rtery Shunt Summary of Patient Data ody ody Surface Plo Graft Patient No., Weight rea Diameter Diameter Q,/ Method of ge, Sex" Disease (kg) (mz) (mm) (mm) L/min/m2 QJQ, ECC Operationb Remarks PTENTS WTHOUT CONGESTVE HERT FLURE 1. 3, M 2. 1, F 3. m, M. 3, M. 2, M., F 7. 12, M 8. 12, M 9. 1 d, M 10., M , F 12. 3, M 13. 3, F 1. 22, M 1. 1, F 1. 1, F , M , M , M 20., F 21., F 22., F 23. 3, F 2. 1, M 1 T, P, small 10 PD T, PS, VSD, 8 SD, small PD 12 CVO, PS 10 after T 11 SV (), PS after 37 Glenn SV (), P after 22 T TG, P 3.3 CTG, VSD after T SV (), P, SD, R Hypoplastic RV, SD CVO, DORV, PS, asplenia SV (), P, SD after T CTG, P, VSD after T after T absence L pulmonary artery after T T, PS /2 8/18 9/1 3/2 8/18 / /21 /13 9/32 9/21 9/21 3/2 7/3 12/31 13/2 1/27 3/2 /30 8/3 9/2 8/27 7/23 /17 3 ' D C D C C t. Death (airway obstruction) Death (hypoxia) PTENTS WTH CONGESTVE HERT FLURE 2., M DORV, PS, / HF M, S 2., M / Late death (HF) 27. 2, F DORV,CVO /21 ' Death (infection) after T, asplenia 28. 1, M, hypoplastic / LOS L pulmonary artery (continued on page 130)

3 ~~ ~ ~~ 130 The nnals of Thoracic Surgery Vol No 2 ugust 1987 Summary of Patient Data (continued) ody ody Surface P/o Graft Patient h-o., Weight rea Diameter Diameter Q,/ Method of ge, Sex Disease (kg) (m ) (mm) (mm) Llrninim Q,/Q, ECC Operationb Remarks PTENTS WTH CONGESTVE HERT FLURE 29. 3, M SV (), PS /1 + Death (HF) 30. 7m, M / Death (HF) 31. 1, M / Late death (HF) m, F SV (), P, D Death (LOS) PD m, F P, SD, PD / Death (LOS) ll ages are recorded in years unless otherwise indicated.?he operative methods were as follows: = shunt from aorta to main pulmonary artery on left side of aorta; = shunt to bifurcation of hypoplastic main pulmonary artery on left side; C = shunt on right side; D = shunt at confluent pulmonary artery on right side of aorta. Data obtained after graft bonding. PNo diameter = ratio of diameter of pulmonary artery to diameter of aorta measured during operation; Q.1 = index of shunt flow; Q./Q, = ratio of shunt flow to systemic flow; ECC = extracorporeal circulation; = tetralogy of Fallot; T = tricuspid atresia; P = pulmonary atresia; FD = patent ductus arteriosus; = pulmonary stenosis; VSD = ventricular septal defect; SD = atrial septal defect; CVO = common atrioventricular orifice; T = lalock-taussig shunt; SV = single ventricle; CTG = corrected transposition of great arteries; Glenn = Glenn shunt; TG = transposition of great arteries; R = right aortic arch; RV = right ventricle; DORV = double-outlet right ventricle; DLV = double-inlet left ventricle, M = mitral atresia; S = single atrium; HF = heart failure; LOS = low output state. mm graft because of an excessively high Q, during operation had a Q, index of.9 L/min/m2 and a ratio of shunt flow to systemic flow (Q,/Qs) of 72. Therefore, the graft was banded to about mm in diameter, and its flow was decreased to a Q, index of 2.77 L/min/m2 and a Q/QS of 1. The other 2 patients (Patients 27 and 30 in Group ) had -mm grafts. oth patients experienced severe congestion postoperatively; the Q, index had been 3. L/min/m2 and.80 L/min/m2 and the Q/Q,, 3 and 8, respectively. The grafts were plicated to obtain a Q, index of 3.11 L/min/m2 and 3.0 L/min/m2 and a Q,/Q, of 7 and 3, respectively. One of the patients died of congestive heart failure two days after the reoperation. n all surviving patients, graft patency was confirmed by the presence of a shunt murmur at the time of discharge about a month postoperatively. n both groups, the SaO2 improved postoperatively from 70.9 to 79.8 in Group and from 2. to 7.7 in Group, but the partial pressure of arterial oxygen did not change significantly (Fig 3). Hematocrit did not decrease significantly within two to six months after operation in either group. On the other hand, the cardiothoracic ratio in Group showed a minimal increase from. to 8.0, while in Group, it increased remarkably from. to 70.9 (Fig ). n the flow studies, the Qs in Group patients were much higher than those in Group patients. The Q, index and the Q,/Q, in Group were 3.8 * 0.91 L/min/ m2 (mean & standard deviation) (N = calculated with exclusion of 2 patients with severe low output syndrome and 1 patient for whom data were not available) and (N = 7), respectively, and those in Group were 1.9 * 0.92 L/min/m2 (N = 20) and 27.2 * 11. (N = 17), respectively (Fig ). Finally, we studied the relationship between graft size and body size. The graft diameter was plotted against body weight and body surface area. The linear regression lines were calculated and are shown in Figure. There were no significant differences in distribution between the two groups. Comment Satisfactory results are not always obtained with a shunt operation. The lalock-taussig shunt is most frequently used as palliation for cyanotic heart disease with decreased pulmonary blood flow. However, in many patients, a sufficient pulmonary blood flow is not obtained because of the small size of the subclavian artery, and a second palliative operation is required a few years after the lalock-taussig shunt because of recurrent severe cyanosis. The Waterston operation, which is preferable in infants, can cause pulmonary edema postoperatively because of an excessive Q, and can have high risks [2-1. modified lalock-taussig shunt is widely used because of the advantages of providing sufficient pulmonary blood flow by use of a - to -mm tubular graft even in infants [, 71 and avoiding sacrifice of the subclavian artery, which causes ischemia of the upper extremity. These palliative measures, especially the second one, make a future radical operation difficult because of distortion of the right or left pulmonary artery. lthough any other palliative shunt operation has some disadvantages, we chose an aorta-pulmonary artery shunt as the method of choice in this series. We used cardiopulmonary bypass in 17 patients and were able to perform the operation safely even in ill infants. The aorta-pulmonary artery shunt operation is excellent for several reasons. t is easier to perform than the other shunt procedures and has a comparatively long-term pa-

4 131 Kusuhara, Miki, Ueda, et al: Optimal Flow of orta-pulmonary rtery Shunt Goretex / \ t Q s L ' Fig 2. Methods of measuring shunt floui (Q,). t can be done directly using an electromagnetic flowmeter or by subtracting the floui of the aorta distal to the graft (Q,) from the flow of the aorta proximal to the graft (Q,). The ratio of shunt flow to systemic flow is Q./Q-. (o = aorta; P = pulmonay artery.) C \ P Goretex P RV \ mm in diameter tency; sufficient Q can be obtained with the selection of the proper graft diameter; and growth of the right and left pulmonary arteries can be expected [l,, 8, 91. However, the selection of the graft diameter that will ensure necessary and sufficient Q, is extremely difficult. The greater the Q,, the better the pulmonary artery growth that can be expected. However, the Q, should be restricted when the complications of heart failure and pulmonary edema are taken into account. Many authors [l, 8-10] have discussed the graft diameter used in an aorta-pulmonary artery shunt (central shunt) and in a modified lalock-taussig shunt. We chose the graft for each individual by this standard; use a graft mm in diameter and 3 or cm in length in a patient weighing 10 kg. The two following formulas show the relationship between graft diameter (D, measured in millimeters) and body weight (W, measured in kilograms), and between graft diameter and body surface area (S, measured in square meters). D = 1.88 n(w) (r =.8) D = 0.87 ln(s) +.3 (r =.73) Fig 1. Operative procedures. () Placement of shunt from aorta (o) to main pulmonary artery (P) on left side of aorta; () placement to bifurcption of hypoplastic main pulmonary artery (mp) on left side; (C) placement on right side; and (D) placement at confluent pulmonary artery on right side of aorta. (R = right atrium; 1P = left pulmonary artery; RV = right ventricle; rp = right pulmonary artery; SVC = superior vena cava.) t was very difficult to predict the Q, in each size of graft. This may be due largely to the influence of the pulmonary vascular resistance, which depends on the extent of pulmonary vessel growth. Some authors [8,10] stated that Q, is limited mainly by the diameter and length of the graft and that a short graft might cause pulmonary edema or pulmonary vascular obstructive disease. There were 9 patients with severe congestive heart failure (Group ) (see Table). Graft banding was necessary in 2 of these patients (Patients 27 and 30) because of an excessive shunt. We believe that the pulmonary vascular resistance was very low in Patient 27. Patient 30 died of congestive heart failure caused by an excessive shunt despite banding. n this patient, there was a prob-

5 132 The nnals of Thoracic Surgery Vol No 2 ugust 1987 SaOz (room air) P < 0.0 lp<ool 1 Ht n- ni 0 U ns 0 group CHF - W 70 9k 9 2 ( k 9 ( 18) group CHF + )----m 2k 12019) 7710() preop postop PO2 (room air) rnrnhg ns ns ns ns n n 0 1 group CHF (2) 92(20) group CHF + ) (9) 82 l(7) CTR preop postop P<OOl P< ns 'P<OO n n T 0 group CHF - 31' 2 O? 7 () 2 2k 7 ( 19) group CHF + *--- 22k 3 9 (2) (1 preop postop Fig 3. Changes in atmospheric arterial oxygen saturation (SaO,) and partial pressure of arterial oxygen (PO,) before and after operation. The mean SaOz increased postoperatively (p <.Ol), but the partial pressure of arterial oxygen showed no significant changes (ns) in either group. Data are shown as the mean 2 the standard deviation with the number of patients in parentheses. (CHF = congestive heart failure.) lem with the graft diameter. We had a good result in Patient 21 (Group ) who did not have a left pulmonary artery and whose Q,/Qs was 70 or higher before banding. Chopra and co-workers [ll] suggested that the optimal Q, is one-half to one-quarter of normal cardiac output. Our calculation of the Q,/Q, for cardiac output indicates that the risk of heart failure is high when the ratio is 0 or more and that the optimal rate may be 30 (mean in Group ) to 0 (mean + standard deviation in Group ). Q, index (Q, per body surface area) of 3 L/min/m2 or more portends a poor prognosis; the desirable Q, index gioup CHF -; ~-) 3 8f 7 (23) (20) group CHF,+) *--- f 3 (9) 70 9? 9 (7) preop postop Fig. Changes in hematocrit (Ht) and cardiothoracic ratio (CTR) before and after operation. Hematocrit decreased in both groups. The cardiothoracic ratio in Group increased significantly about a month after operation. However, in Group there was no significant (ns) increase postoperatively. Data are shown as the mean 2 the standard deviation with the number of patients in parentheses. (CHF = congestive heart failure.) may range from about 1. L/min/m2 (mean in Group ) to 2. L/min/m2 (mean + standard deviation in Group ). We thought that a flow of less than 1. L/min/m2 was safer but insufficient. Cardiac reserve is scarce in infants, and the optimal Q, for them may be in far lower ranges. Further studies involving a greater number of infants are indicated. n some patients with an excessive shunt, particularly those with a Q,/Q, of more than 0 or a Q, index of

6 133 Kusuhara, Miki, Ueda, et al: Optimal Flow of orta-pulmonary rtery Shunt lrninlrn" QE ndex [+092: f group group "1 ' T 0. D(rnm)=l 88PnW(kg)+ 8 r=o 8,.,., $0 30 ' 0 kg body weight (W), Q/Qs D(rnrn)=O87 lns(rn2)+3 r=o f11 f group group Fig. Comparison of shunt flow index (Q, index) and shunt flow ratio (Q,/Q,) between Groups and. The two groups are well separated by the broken lines. The patient whose Q,, is more than 0 of the Q./QS or more than 3 Llminlm2 of the Q index (mean - standard deviation of Group ) tends to have a poor prognosis. to = alive; 0 = operative death caused by heart failure; rn = late death caused by heart failure; = operative death caused by infection, hypoxia, or airway obstruction; parentheses = severe low cardiac output syndrome after operation.) more than 3 L/min/m2, atmospheric partial pressure of arterial oxygen does not exceed 0 mm Hg despite such a high Q. Heart failure and ventilation insufficiency would develop. respiratory disturbance similar to asthma is apt to occur immediately after operation, and long-term postoperative therapy for heart failure and respiratory insufficiency is often required. To cope with an uncontrollable excessive shunt, we narrow the graft by suturing or by cutting out its central portion and replacing it with a narrower graft as though we were doing a banding operation O 2.0 m2 body surface area (S) Fig. Correlations between graft diameter (D) and body weight and between graft diameter and body surface area. to = Group [no congestive heart failure]; = Group [congestive heart failure].) s for the long-term patency of expanded PE grafts in our patients, patency was confirmed by stethoscope in. Graft flow murmurs disappeared and repeated anoxic spells occurred about one year nine months after operation in Patient 3 (Group ) whose graft was occluded. lalock-taussig operation was performed on this patient. possible cause was that the graft had been pulled and deformed as the patient grew. This trend is supported by similar findings obtained during the radical operation on Patient 1. Therefore, we have adopted a policy of using grafts of as large a diameter as possible and of sufficient length. The future distortion caused by growth is taken into account, although the relationship of the anastomotic sites between the aorta and the pulmonary artery is important. References 1. Gazzaniga, Lamberti JJ, Siewers RD, et al: rterial prosthesis of microporous expanded polytetrafluoroethylene for construction of aorta-pulmonary shunts. J Thorac Cardiovasc Surg 72:37, Waterston DJ, Stark J, shcraft KW: scending aorta-to-

7 13 The nnals of Thoracic Surgery Vol No 2 ugust 1987 right pulmonary artery shunts: experience with patients. Surgery 72:897, ernhard WF, Jones JE, Friedberg DZ, Litwin S: scending aorta-right pulmonary artery shunt in infants and older patients with certain types of cyanotic congenital heart disease. Circulation 3:80, Tay DJ, Engle M, Ehlers KH, Levin R Early results and late developments of the Waterston anastomosis. Circulation 0:220, 197. Truccone NJ, owman FO, Malm JR, Gersony WM: Systemic-pulmonary arterial shunts in the first year of life. Circulation 9:08, 197. McKay R, de Leva1 MR, Rees P, et al: Postoperative angiographic assessment of modified lalock-taussig shunts using expanded polytetrafluoroethylene (Gore-Tex). nn Thorac Surg 30:137, Donahoo JS, Gardner TJ, Zahka K, Kidd SL: Systemicpulmonary shunts in neonates and infants using micropo- rous expanded polytetrafluoroethylene: immediate and late results. nn Thorac Surg 30:1, Lamberti JJ, Campbell C, Replogle RL, et al: The prosthetic (Teflon) central aortopulmonary shunt for cyanotic infants less than three weeks old: results and long-term follow-up. nn Thorac Surg 28:8, Jennings R Jr, nnes J, rickman RD: Use of microporous expanded polytetrafluoroethylene graft for aorta-pulmonary shunts in infants with complex cyanotic heart disease. J Thorac Cardiovasc Surg 7:89, Miyamoto K, Zavanella C, Lewin N, Subramanian S: orta-pulmonary artery shunts with expanded polytetrafluoroethylene (PE) tube. nn Thorac Surg 27:13, Chopra PS, Levy JM, Dacumos GL, et al: The lalock- Taussig operation: the procedure of choice in the hypoxic infant with tetralogy of Fallot. nn Thorac Surg 22:23, 197 Circulatory Support 1988 dam s Mark Hotel, St. Louis, Missouri February -7, 1988 (weekend meeting) Circulatory Support 1988 will be a comprehensive meeting on the clinical application of circulatory support devices. Surgeons, perfusionists, engineers, and operating room and intensive care unit nurses are encouraged to attend either individually or as a team. The meeting is sponsored by The Society of Thoracic Surgeons under the direction of its Committee on Circulatory ssist Devices and rtificial Hearts. Committee members are: D. Glenn Pennington, M.D., Chairman; Jack G. Copeland, M.D.; Charles Hahn, M.D.; J. Donald Hill, M.D.; George J. Magovern, M.D.; Peer M. Portner, Ph.D.; and M. Glenn Rahmoeller. For this weekend meeting, the Saturday morning segment entitled Problem Cases will include panel discussions on such topics as Patient Selection, ntraoperative Management, and leeding and nti-coagulation. Saturday afternoon will be divided in two parts, the first being a unique series of video presentations on the working details of currently available support devices. The second Saturday afternoon session will offer attendees break-out meetings divided into concurrent sessions for surgeons, perfusionists/engineers, and OWCU nurses on the subjects of: (1) ECMO, Roller, and Centrifugal Pumps, (2) External Pulsatile Pumps, and (3) nternal Pulsatile Pumps. Sunday morning will be devoted to a state-of-the-art session with discussions focusing on such topics as Resuscitation for Cardiac Shock, Post Cardiotomy Support, ridging to Transplant, Permanent rtificial Hearts, and Devices of the Future. n addition, there will be commercial exhibits related directly to program topics (by invitation only), and scientific posters will be used to show how circulatory devices are being used throughout the U.S. and elsewhere. For registration and other meeting information contact: The Society of Thoracic Surgeons, 111 East Wacker Dr, Chicago, L 001; tel: (312) -10.