Y HOC VIET NAM SO OAC BIET - THANG 11/2010
KFT QUA Bl/OfC DAU DAT STENT ONG DONG MACH TRONG BENH TIM BAM SINH CO TUAN HOAN PHOI PHU THUOC ONG DONG MACH
Nguyen Minh Trf Viet, Chiu Kin Hau, Phan Thanh Tho, Truong Ba Luu(*)
TOM TAT
Boi c ^ n h : Dat stent dng dgng mach ngay nay cd the xem nhu la mgt phuong phap dieu tri thay the cho phau thuat tao shunt chu phdi nham cai thien luu lUdng tuan hoan phdi.
Muc tieu: Bai bao cao nay dUa ra nhOng kinh nghiem budc dau ve dat stent dng dgng mach trong benh tim bam sinh cd tuan hoan phd'i phu thuoc dng tren 6 benh nhan.
PhUcfnq phap: TU thang 3/2010 den thang 9/2010, 6 benh nhi dUOc tien hanh dat stent dng dgng mach sau khi dugc khao sat dudi sieu am tim va chup mach mau. 5 benh nhan bi teo van dgng mach phd'i vdi thong lien that, 2 trong so nay cd 2 that, 3 trong sd con lai cd tuan hoan kieu 1 tam that. Guidewire 0.014 dugc sd dung de luon qua dng dgng mach. Stent dgng mach vanh dugc dung de dat vao ong dgng mach. Theo doi sau thu thuat dua vao lam sang, sieu am va CT Scanner hay chup mach mau.
Ket q u i : Tudi benh nhan tir 5 den 45 ngay. Can nang tU 2900g den 4000g. Viec dat stent thanh cdng trong 5 trudng hgp. Khdng CO tif vong lien quan den thu thuat. Bien chifng nhe xay ra tren 3 trudng hgp. Mgt benh nhi td vong sau 5 ngay do huyet khdi thuyen tat trong stent. 3 benh nhi cd dgng mach phdi phat trien tot va dang chd dUdc lam p h i u thuat triet de hay lam phau thuat Glenn. 1 benh nhan bi hep dgng mach phoi trai can phai lam them thong noi chu phdi.
Ket luan: Stent dng dpng mach la thu
thuat kha thi, an toan va hieu qua tren nhu nhi nhd va so sinh co tim bam sinh vdi tuan hoan phdi phu thuoc dng.
SUMMARY
INITIAL RESULTS OF STENTING THE DUCTUS ARTERIOSUS IN DUCT - DEPENDENT PULMONARY CIRCULATION
Backgrounds: Transcatheter patent ductus arteriosus stenting is considered now as a modality to improve the pulmonary blood flow, as an alternative to surgical aortopulmonary shunt.
Objectives: this report shows our initial experience with stent implantation of ductus arteriosus in duct - dependent pulmonary circulation in 6 patients.
Methods: Between March 2010 and September 2010, 6 patients underwent ductus arteriosus stenting after full assessment by echocardiogram and angiogram. 5 patients have pulmonary atresia and ventricular septal defect, 2 of them with 2 ventricules and the remaining 3 with single ventricular morphology. 1 patient has pulmomary atresia and intact ventricular septum.
The duct was accessed with a 0.014 - inch guidewire. A low-profile premounted coronary stent was implanted in the duct. Attempts were make to covered the entire length of the ductus arteriosus. The follow - up was by clinical examination, echocardiography, GT Scanner and repeat cardiac catheterization following the procedure.
' Don vi tim much nhi ky thudt cao, benh vien Nhi ddng 2, Tp. IHCM
CHUYEN OE: PHAU THUAT TIM MACH VA LONG NGUC VIET NAM
Results: .Age of the patients was from 5 days to 45 days. Weight of them was from 2600g to 4000g. Patent ductus arteriosus stenting was successful in 5 patients. There was no procedure-related mortality. Minor complications occurred in 3. One patient died 5 days after because of thrombosis in stent. 3 patients has good development of pulmonary arteries on GT Scanner and are waiting for complete surgical treatment or bidirectional Glenn's shunt. One has stenosis of left pulmonary artery that needs another aortopulmonary shunt.
Conclusion: Ductus arteriosus stent is feasible, safe and effective palliation in newborns and young infant with duct - dependent pulmonary circulation.
I. OAT VAN OE
Vdi nhung tien bd vugt bat ve ky thuat md va cham sde hdi su'c sau md, ngay nay cang nhieu benh tim bam sinh phirc tap dugc dieu tri hieu qua. Tai nhung trung tam tien tien, ngay cang nhieu benh nhi so sinh cd tim bam sinh dugc dieu tri triet de. Tuy nhien, ddi vdi da sd benh tim phuc tap cd tuan hoan phdi phu thudc dng ddng mach, d giai doan so sinh. viec giir dng ddng mach luu thdng dugc xem nhu dieu tri bao tdn sinh mang, giup cho nhimg phau thuat triet dk hon sau nay (tim bam sinh vdi tuan hoan mdt thit vd mat sinh ly benh va tir chimg fallot vdi teo van ddng mach phdi la nhung vi du trong hoan canh na>).
Dieu tri thdng thudng va dugc nhi8u trung tam chap nhan hien nay ddi vdi benh tim bam sinh cd tuan hoim phdi phu thudc dng ddng mach (TBS-THPPT) la duy tri ong dong mach bang thudc prostaglandine El
(PGEl) sau dd la phau thuat tao shunt chii phdi (mgt dng nhan tao, khdng bi tu dong lai). Rd rang la viec giU dng ddng mach t6n tai mdt cac tir nliien xem ra cd ve hgp ly hon la gan cho tuan hoan phdi mdt dng nhan tao... PGEl la mdt loai thudc cd the duy tri hieu qua dng ddng mach. Tuy nhien, thu6c rat dac tien. khd sir dung, hieu qua trong thdi gian ngan. neu sir dung lau dai se giam hieu qua va rat nhieu tac dung phu. Vao nhimg nam dau 1990, xuat hien mdt vai nghien ciru budc dau tren ngudi va siic vat de khao sat viec duy tri dng ddng mach bang each dat stent (3-8). Ket qua dat dugc gay ra nhi^u tranh cai vi tinh kha thi ciia thii thuat, bi^n chimg nghiem trgng (tir vong do co that 6ng ddng mach, tang sinh ndi mach gay tit stent...) cung nhu hieu qua len su phat triln ciia tuan hoan phdi. Tuy nhien, vao cuoi nhirng nam ciia thien nien ky va nhUng nam gan day, vdi sir phat trien khdng ngimg ciia catheter, guidewire, stent ddng maeh vanh, ngay cang cd nhieu nghien cim cho ket qua kha khich le ve mat ky thuat thuc hien, hieu qua va kha thi ciia phuang phap dat stent de duy tri dng ddng mach (9). Va gan day nhat la nghien cim ciia Santoro G va cdng su cho thay phuang phap dieu tri nay cd the dugc xem nhu bien phap thay thd cho phau thuat.
II. PHUONG PHAP
Tir thang 3 nam 2010 ddn thang 9 nam 2010, 06 benh nhi vdi benh tim bam sinh phu thudc dng ddng mach hay thidu nang nang tuan hoan phdi dugc tien hanh dat stent dng ddng mach vdi sir ddng y ciia gia dinh sau khi hg da dugc tham van ve nguy ca ciia thii thuat. Dac diem lam sang ciing vdi chan doan ciia benh nhan dugc tdm tat d bang I. •,;,
Y HOC VIET NAM SO OAC BIET - T H A N G 11/2010
Bang I. M d TrUdng hdp
1 2 3
4 5
6
sd dac diem lam sang \ a chan doan ciia cac benh nhan dugc dat stent Tuoi
7 ngay 20 ngay
5 ngay
10 ngay 16 ngay
45 ngay
Can nang 3,2 kg 2,9 kg 3 kg
3,3 kg 3,5 kg
4,0 kg
Chan doan chinh
Teo van ddng mach phd'i - thdng lien that - hdi chiTng DiGeorge
Tim mdt that - that phai 2 dUdng ra - teo van dm phoi Teo van ddng mach phdi-thieu san that phai-tuan hoan vanh phu thudc that phai-tbdng lien nhT
Teo van ddng mach phdi - thdng lien that
Khdng Id van 3 la - thdng lien nhT - thdng lien that - hep nang dUdi van ddng mach phd'i
Chuyen vi dai ddng mach - thdng lien that - straddling van 2 la - hep nang dUdi van ddng mach phdi
Sieu am tim dugc thuc hien ky ludng tmdc thii thuat de xac dinh chan doan benh ly tim bam sinh ddng thdi sa bd danh gia hinh the cung nhu sir thdng thuong cua dng dpng mach. Cac benh nhan dugc tien hanh lam thdng tim vdi gay me toan than va ndi khi quan giiip thd. Bdc Id ddng mach va tinh mach diii ddi ben, sau do ludn sheath 4F - 5F cho ddng va tmh mach. Cac benh nhan dugc sir dung chdng ddng mau tmh mach vdi Heparin lOOUI/kg, va Cefazoline 30mg/kg phdng ngira viem ndi tam mac nhiem triing.
PGEl dugc sii' dung tren trudng hgp 3 va 4 de giu' dng ddng mach va ngimg 6h trude thii thuat. Hinh anh hgc cua cung ddng mach chu dugc khao sat vdi cac mat phang trude - sau, ben, 4 - budng. Hinh anh hgc ciia dng ddng mach dugc xem xet ky ludng tit nai xuat phat tir ddng mach chii xudng den diem ndi vdi than ddng mach phdi. Dudng kinh nhd nhat ciing nhu chieu dai cua dng ddng mach dugc do dac. Hinh anh hgc ciia tuan hoan phdi (than va 2 nhanh dgng mach phdi) cung dugc xem xet ky ludng. Cac thdng sd huyet ddng hoc Cling dugc ghi nhan tnrdc, trong va sau thii thuat (huyet ap va do bao hda oxy mau ddng mach).
Phan ldn cac trudng hgp, viec dat stent dng ddng mach cd the thuc hien qua dudng ddng mach (retrograde). Guidewire 0.014 (Hi-Torque BMW Abbott, Cruiser Biotronik) dau mem, than cung dugc ludn tir ddng mach chii qua dng ddng mach vao sau trong nhanh ciia ddng mach phdi vdi sir trg giiip ciia cathether JR 4F. Trudng hgp 2 va 5, do hinh dang dng ddng mach vdi xuat phat sdm mat dudi cung ddng mach chii, chung tdi phai diing catheter JR 5F ludn theo dudng tmh mach di qua Id thdng lien that va ludn qua ddng mach chii len de cho dugc guidewire vao dng ddng mach (antegrade).
Sau dd stent ddng mach vanh dugc dat vao dng ddng mach (OrbusNeich's R Stent). Vi tri dat stent dugc chgn sao cho stent ldi mdt it vao than ddng mach phdi, phii het chieu dai dng ddng mach va khdng ldi vao ddng mach chu. Chieu dai ciia stent dugc chgn lira ky ludng vdi du trii kha nang co ngan 15-20%
sau khi dugc bung hoan toan (H.l). Dudng kinh stent dugc chgn tiiy vao can nang benh nhan, benh nhan nhd hon 3 kg > stent dudng kinh 3 mm dugc chgn, benh nhan tir 3 - 4 kg
> stent 3 . 5 - 4 mm dugc chgn, benh nhan tir 4 - 5 kg > stent 4.5 mm dugc chgn. Sau khi
CHUYEN OE: PHAU THUAT TIM MACH VA LONG NGL/C VIET NAM
tha stent. \iec thuc hien viec kiem tra bang xet kha nang phai dat them mdt stent khac chup mach mau de xem xet vi tri ciia stent va (H.2).
H.T Hinh dang hgc cua dng ddng mach va ddng mach phdi dugc khao sat bing chup mach mau. Wire dugc ludn qua dng ddng mach theo dudng retrograde (trai)
1
H.2. Kiem tra vi tri ciia stent Sau thii thuat. benh nhan dugc thd may it
nhat 12h, rut ndi khi quan cang sdm khi cd the, heparin truj'^n tmh mach 20 - 25 Ul/kg/h trong^ 48-72h, sau dd duy tri vdi aspirin lieu chdng kit tap tilu ciu.
Benh nhan dugc theo ddi sat sao dau hieu lam sang, huyit ddng, do bao hda oxy mau ddng mach. Sau dd, viec theo ddi vg sau dua vao lam sang, sieu am tim (1- 3 - 6 thang). CT Sanner. chup mach mau dd danh gia tuan hoan phdi gidng nhu mdt trudng hgp
lam BT shunts dd xem xet kha nang phai lam lai thii thuat tam thdi hoac cd thi tiln hanh cac phau thuat d giai doan tilp theo.
III. KET QUA
Ket qua cua thii thuat dat stent dugc tdm tat trong bang 2. Trudng hgp 4, benh nhi bi teo van ddng mach phdi - thdng lien that, chung tdi khdng the ludn guidewire qua dng dgng mach do hinh dang dng ddng mach
Y HOC VIET NAM SO DAC BIET - THANG 11/2010
thang dimg, ngoan ngoeo nhieu chd gap gdc khdng the vao bang dudng ddng mach. Hon nira, khi chiing tdi theo dudng tinh mach, ludn catheter qua thdng lien that de den ddng mach chii len, catheter lai de vao nut nhT that gay bloc nhT that do 3 vdi rdi loan nang huyet ddng hgc. Do dd chiing thdi phai ngimg thu thuat. Benh nhan sau dd dugc duy tri md dng dgng mach bang PGEl de chd phau thuat thdng ndi chii phdi, nhung bi nhiem triing sa
sinh nang do nhiem triing benh \'ien va tir vong 2 ngay sau dd. Trudng hgp 3. benli nhan cd ket qua sau dat stent rat kha quan, nhung dot tir 5 ngay sau thu thuat do huyet khdi trong stent. Trudng hgp 1, benh nhan phat trien the chat rat tdt, can nang 7,3kg hien tai benh nhan cd do bao hda oxy 70%, chung tdi tinh ti le McGoon ciia ddng mach phdi la 1,5, chi sd Nikata la 152/m2. Benh nhan dang dugc chd lam phau thuat kieu Sano.
Bang TrUdng
hdp
1 2 3 4 5 6
2. Mdt sd c Du'dng
vao
retrograde antegrade retrograde That bai antegrade retrograde
ac diem ciia thii thuat dat Stent Chieu
dai ong dong mach 13
8 10 10 9
DUdng kinh Stent (mm) 3.5
3 3.5 3.5 4
Chieu dai Stent (mm) 15 10 12 12 12
va ket qua Do bao
hoa oxy (1)
(O/o)
45 50 70 55 45
Do bao hoa oxy (2)
(O/o)
90 88 90 95 90
Thdi gian theo ddi (thang)
7 7
*
* 3 1
Do bao hoa oxy (3)
(O/o)
70 65
80 78 (l)trudc Stent, (2) sau Stent, (3) lan theo ddi cudi, * tir vong
Trudng hgp 2, tre cd phuang an dieu tri kieu tuan hoan mdt that. Hien tai tre phat the chat, tam than van ddng kha tdt, can nang 7 kg (7 thang), tre hai tim vdi do bao hda oxy mau ddng mach 65%). Chiing tdi thuc hien lam MSCT va chup mach mau cho thay ddng mach phdi trai bi hep chd phan nhanh tir than ddng mach phdi, kich thudc khoang 3 mm.
Shunt chii phdi ben trai dang dugc du kien thuc hien. Trudng hgp 5 va 6, benh nhi phat trien thi chit tam than binh thudng, vdi do bao hda oxy mau ddng mach trong gidi ban cho phep (80 va 78%o), sieu am tim cho thay ddng chay qua stent boat ddng tdt vdi kich thircVc ddng mach phdi nam trong gidi ban binh thudng theo z-scores. Trong thdi gian
tdi. khi benh nhi dugc 6 - 1 2 thang chung tdi se khao sat ky tuan hdan phdi bang chup mach mau va MSCT de xet chi dinh thuc hien phau thuat Glenn's shunt cho cac benh nhan nay.
Thdi gian thuc hien thii thuat trung bmh tir 60 den 120 phut. Neu dat stent thanh cdng benh nhi deu dugc xuat vien khdi hdi sire sau 24h.
Bien chiing va t u vong. Khdng cd tir vong gay ra do Iam thii thuat. Mdt benh nhan tir \'ong do tac stent do huyet khdi 5 ngay sau do. Benh nhan khac, sau thii thuat that bai, tir vong do nhiem trimg benh vien. Mdt benh nhan bi bloc nhT that do 3 trong khi lam thii thuat, hdi phuc hoan toan sau khi ngung thii thuat. 3 benh nhi khac bi bien chimg nhe:
CHUYEN OE: PHAU THUAT TIM MACH VA LONG NGUC VIET NAM
cha\- mau va hu}'lt khdi tai vet chich ddng mach diii. hdi phuc hoan toan sau dd.
IV. BAN LUAN
Phau thuat lam shunt chii phdi tren benli nhan so sinh cd benh ly tim bam sinh tuan hoan phdi phu thudc dng ddng mach tir lau da dugc chap nhan rdng rai nhu dieu tri ca ban tam thdi budc dau. Tuy nhien, ti le tir vong kha cao (10 - 30%), ti le bien chirng nghiem trgng kha nhieu (liet co hoanh. tran dich mang phdi, nhiem triing phdi, tang luu lugng tuan hoan phdi qua m i r c . ) dan den thdi gian nam hdi sire lau (1-2). Dac biet d nhimg trung tam mdi chua cd nhieu kinh nghiem hdi sire so sinh, phau thuat shunt chii phdi cd the xem nhu la khd kha thi do ti le tir vong cao va ganh nang ve van de hdi sue. Do dd, dat stent dng ddng mach cd the la each dieu tri dang dugc quan tam va nen dugc xem nhu phuong phap dieu tri thay the ddi vdi mdt sd cac benh nhan thich hgp. Kit qua ciia mdt sd nghien ciru ban dau (3-8) cho mdt sd ket qua gay nhieu tranh cai do ban che ve mat ky thuat dua den tinh kha thi va hieu qua han che. Tu}- nhien, vdi ket qua ciia mdt sd nghien cim gan day (9), vdi sir phat trien ciia stent va guidewire ddng mach vanh, tinh kha thi cua phuong phap nay rit cao (>75%) vdi ti le tir \'ong do thii thuat gin bing 0%, va ti le bien chimg khdng nhieu (trdi stent, huyit khdi trong stent, co that dng ddng mach...) va cd the khac phuc dugc. Kdt qua dilu tri kha kha quan khi benh nhan cd the dat din phau thuat tiep theo. Mdt nghien cim gin day ciia Santoro G. \'a cdng su so sanh viec dat stent dng ddng mach va phau thuat lam shunt chii phdi len sir phat triln ciia tuin hoan phdi, Nghien cim nay bao gdm 27 benh nhan bi tim bam sinh cd tuan hoan phdi phu thudc dng ddng mach. trong dd 13 benh nhan duac
dat stent (nhdm 1) va 14 benh nhan dugc phau thuat (nhdm 2). Su phat trien cua tu5n hoan phdi dugc so sanh dua vao ti le McGoon \'a chi sd Nakata dua tren kit qua chup mach mau. Nghien ciai cho thiy sir phat trien ddng mach phdi cai thien ro ret trong 2 phuong phap: Nakata index tang tir 136 ± 72 mm/m2 len 294 ± 99mm/m2, p<0.0001 cho nlidm 1, va 151 ± 74 mm/m2 len 295 ± 177 innVin2, p < 0,01 cho nhdm 2), va tu'ong tu nliu ddi vdi ti le McGoon.
Diem can nhan manh la thdi gian hii phuc tai hdi sue cua benh nhan dugc dat stent dng ddng mach rat ngoan muc so vdi phuong phap phau thuat. Day la mdt uu diem rit dang quan tam ddi vdi nhiJng trung tam mdi phat trien chua cd nhieu kinh nghiem ve hoi sire cho nhung benh nhan sa sinh nhd ky nhu tinh hinh nudc ta hien nay. Hon nua, viec sir dung PGEl cdn rat ban che do dieu kien kinh te va tinh san cd tai nudc ta, chirng tdi thiet nghT phuang phap dat Stent it nhieu la cuu canh cho sinh mang benh nhan.
Ve each chgn lua benh nhan, ddi vdi trudng hgp teo van ddng mach phdi - thdng lien that, dng ddng mach thudng xuat phat thang dimg va rat ngoan ngoeo, viec dat stent se rat khd khan do khdng thi ludn dugc guidewire vao dng ddng mach (8). That bai trong trudng hgp 4 ciia chiing tdi la mdt vi du. Chimg tdi cho rang cin nen than trong trong viec dat stent ong ddng mach tren nhiing benh nhan nay. N I U kit qua sieu am cd the tien lugng dugc hinh dang cua dng ddng mach khdng thuan lgi, benh nhan se dugc dieu tri phau thuat.
Rat nhieu nghien ciru de cap den van de tang sinh ndi mach, huyit khoi dan den stent dng ddng mach boat ddng khdng hieu qua, tai hep (3-8). Mdt trudng hgp tir vong trong nghien cim nay la do chiing tdi chua manh
Y HOC VIET NAM SO OAC BIET - THANG 11/2010
dang tai nong stent da bi huyet khdi. Tuy nhien, vdi cac stent mach vanh ky thuat mdi.
da sd cac nghien cim sau nay vdi thdi gian theo ddi tir 5 - 12 thang cho thiy benh nhi phat trien the chat hoan hao vdi phat trien ddng mach phdi tdt (8). Them vao dd, vdi phat trien cua phau thuat tim mach nhi, cac phau thuat sira chUa triet de cho benh ly teo van ddng mach phdi - thdng lien that (kieu Rastelli) hay phau thuat Glenn's shunt cho tuan hoan mdt that cd the thuc hien an toan d benh nhi chi can tren 4 thang. Do dd, van de stent phii thudc la that su khdng can thiet.
Phuong phap dat stent dng ddng mach cdn kha mdi me ddi vdi chiing tdi. Sd lugng benh nhan va thdi gian theo ddi cdn han che.
Tuy nhien, vdi nhiing kinh nghiem rut ra tir nhiing benh nhi dau tien, chiing tdi cho rang day la phuang phap day trien vgng thich hgp vdi hoan canh kinh te xa hdi ciia nudc ta hien nay.
V. KET LUAN
Dat stent dng ddng mach cd the dugc xem la phuang phap dieu tri thay the cho phuang phap phau thuat Iam shunt chu phdi trong dieu trj benh tim bam sinh cd tuan hoan phdi phu thudc dng ddng mach. Vdi viec chgn lira benh nhan va ky thuat thich hgp, day la phuong phap kha thi va hieu qua trong dieu tri bao tdn budc dau d berth nhi nhd ky va sa sinh. Chung tdi cho rang, day la phuong phap day trien vgng thich hgp vdi hoan canh kinh te xa hdi cua nudc ta hien nay.
TAI UEU THAM KHAO
1. Tamisier D, Vou'he PR, Vermant F, Leca F, Massot C, Neveux J. Modified Blalock -Taussig shunts: results in infants less tlian 3 months of age.
Ann Thorac Surg 1990; 49: 797-801.
2. M Sanjeeva Rao, Anil Bhan, Sachin Talwar, Rajesh Sharma, Shiv Kumar Choudhary, Balram Airan, Anita Saxena, Shyam Sunder Kothari, Rajnish Juneja and Panangipalli Venugopal. Modified Bialock-Taussig Shunt in Neonates:
Determinants of Immediate Outcome. Asian Cardiovasc Thorac Ann 2000: 8:339-343.
3. Coe J, Olley P. A novel method to maintain ductus arteriosus patency. J Am Coll Cardiol
1991; 18:3: 837-41.
4. Rosenthal E, Qureshi S, Kakadekar A et al. Comparison of balloon dilatation and stent implantation to maintain patency of the neonatal duct in lambs. Am J Cardiol
1993;71:1373-6.
5. Gibbs J, Rothman M, Rees M, Parsons J, Blackburn M, Ruiz C. Stenting of tlie arterial duct: a new approach to palliation for pulmonary atresia. Br Heart J 1992; 67: 240-5.
6. Abrahms S, Walsh K. Arterial duct morphology with reference to angioplasty and stenting. Int J Card 1993; 40: 27-33.
7. Schatz RA, Bairn DS, Leon M et al.
Clinical experience with the Palmaz-Schatz coronary stents. Initial results of a multi- center study. Circulation 1991; 83: 148-61.
8. Gibbs JL, Uzun O, Blackburn ME, et al. Fate of the stented arterial duct.
Circulation 1999; 99: 2621-2625.
9. Schneider M, Zartner P, Sidiropoulos A, et al. Stent implantation of the arterial duct in newborns with duct-dependent circulation.
Eur Heart J 1998; 19: 1401-1409.
10. AIwi M, Choo KK, Latiff HA, et aL Initial results and medium-term follow-up of stent implantation of patent ductus arteriosus in duct-dependent pulmonary circulation. J Am Coll Cardiol 2004; 44:
438-445.
