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J Am Coll Cardiol, 2000; 35:468-476 © 2000 by the American College of Cardiology Foundation |

* Department of Cardiology, Institut Jantung Negara (National Heart Institute), Kuala Lumpur, Malaysia
Department of Cardiothoracic Surgery, Institut Jantung Negara (National Heart Institute), Kuala Lumpur, Malaysia
Manuscript received October 19, 1998; revised manuscript received September 27, 1999, accepted October 18, 1999.
Reprint requests and correspondence: Dr. Mazeni Alwi, Department of Cardiology, Institut Jantung Negara, 145, Jalan Tun Razak, 50400 Kuala Lumpur, Malaysia
mazeni{at}ijn.com.my
| Abstract |
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We compared the result of radiofrequency (RF)-assisted valvotomy and balloon dilation with closed surgical valvotomy and Blalock Taussig (BT) shunt as primary treatment in selected patients with pulmonary atresia and intact ventricular septum (PA-IVS).
BACKGROUND
Patients with PA-IVS who have mild to moderate hypoplasia of the right ventricle (RV) and patent infundiblum have the greatest potential for complete biventricular circulation. The use of RF or laser wires to perforate the atretic valve followed by balloon dilation provides an alternative to surgery.
METHODS
Between May 1990 and March 1998, 33 selected patients underwent either percutaneous RF valvotomy and balloon dilation (group 1, n = 21; two crossed over to group 2) or surgical valvotomy with concomitant BT shunt (group 2, n = 14). Second RV decompression by balloon dilation or right ventricular outflow tract (RVOT) reconstruction were performed if necessary. Patients who remained cyanosed were subjected to transcatheter trial closure of the interatrial communication. Partial biventricular repair was offered to those with inadequate growth of the RV.
RESULTS
The primary procedure was successful in 19 patients in group 1. There was one in-hospital death and two late deaths. Of the remaining 16 survivors, 12 achieved complete biventricular circulation, 7 of whom required no further interventions. Two patients required repeat balloon dilation, 1 RVOT reconstruction and 2 transcatheter closure of interatrial communication. Two patients underwent partial biventricular repair. In group 2, there were 3 in-hospital deaths after the primary procedure and 1 patient died four months later. All survivors (n = 10) required a second RV decompression, 8 by balloon dilation and 2 by RVOT reconstruction, after which, two patients died. Of the final 8 survivors, 7 achieved complete biventricular circulation, 5 after coil occlusion of the BT shunt and 2 after closure of interatrial communication.
CONCLUSIONS
Radiofrequency valvotomy and balloon dilation is more efficacious and safe compared with closed pulmonary valvotomy and BT shunt in selected patients with PA-IVS.
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It has increasingly been recognized that there are two principal forms of this disease, those with mild to moderate hypoplasia of the RV who generally have a patent infundibulum, and those with severe hypoplasia of the RV who positively correlate with major RV-coronary connections (4). For patients in the first group, who incidentally form a majority in most of the reported series, many authors believe that the treatment goal is to eventually establish a complete biventricular circulation with RV decompression as the initial palliative procedure (5). On the other hand, patients with severely hypoplastic, diminutive RV are generally assigned towards a univentricular repair, and in the difficult subset of patients with RV-dependent coronary circulation, cardiac transplantation may be an option. Right ventricle decompression may be achieved by simple pulmonary valvotomy without cardiopulmonary bypass, or by a more radical transannular patch of the right ventricular outflow tract (RVOT) in the neonatal period with or without a concomitant systemic-pulmonary shunt. More recently, the use of laser wire and radiofrequency (RF)-assisted valvotomy and balloon dilation has made possible primary treatment of this group of patients to be undertaken in the catheterization laboratory (6,7).
This study reviews the outcome of percutaneous RF valvotomy and balloon dilation versus closed surgical valvotomy and Blalock Taussig (BT) shunt in a selected group of PA-IVS patients with mild to moderate RV hypoplasia and patent infundibulum.
| Methods |
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Transcatheter primary procedure. Twenty-one patients were subjected to RF valvotomy and balloon dilation, of whom, two patients were later included in the surgical group after unsuccessful procedure (group 1). All patients in group 1 underwent cardiac catheterization under general anesthesia. The femoral artery and vein were cannulated percutaneously using 4F and 5F sheaths, respectively. Right ventricle-dependent coronary circulation was first excluded in all patients. Radiofrequency valvotomy was performed using the HAT 300 generator and 0.018-in. cereblate wire (Sulzer Osypka GmBH, Grenzach-Wyhlen, Germany) via a 5F Judkins right catheter. After successful valvotomy, a 0.014-in. Flex coronary guidewire (ACS Hi-Torque; Floppy II, Temeluca, California), and in the later cases Crosswire (Terumo Corp., Tokyo, Japan), was passed antegradely into the pulmonary artery. Procedural failure is defined as inability to perforate the atretic valve with the RF wire, and subsequent balloon dilation thus could not be performed.
Earlier in the series, the flex coronary wire was routinely snared in the main pulmonary artery and brought down into the descending aorta for better support during balloon dilation. Balloon dilation was performed sequentially using 2-mm and 4-mm coronary balloons (Schneider [Europe] GmBH, Bulach, Switzerland) and finally 8- to 10-mm Tyshak (NuMED; Cornwall, Ontario, Canada) valvuloplasty balloon. The right ventricular-to-aortic pressure ratio was used as a hemodynamic index of the severity of RV hypertension. Prostoglandin infusion was then gradually weaned off after 48 h, and if the patient remained duct dependent two weeks after the procedure or showed evidence of ductal closure despite PGE1 infusion, a modified BT shunt or stenting of the patent ductus arteriosus (PDA) was put forward (adjunct procedure).
Surgical valvotomy. Fourteen patients, including the two who had unsuccessful RF valvotomy, underwent closed pulmonary valvotomy with a concomitant BT shunt via left thoracotomy (group 2). Prostoglandin infusion was discontinued 24 h after the surgery. None of these patients underwent preliminary cardiac catheterization studies, except the two patients who crossed over.
Echocardiographic examination chiefly looking at the degree of residual RVOT obstruction was performed at 24 h after the primary procedure and repeated as necessary during the initial hospitalization.
Morbidity and mortality. The duration of hospital stay, requirement for ventilatory and inotropic support, complications and mortality related to the primary procedure between two groups were compared. Mortality within the initial hospital stay was considered as in-hospital death, and late death were patients who died during subsequent admissions.
Follow-up. On follow-up, the degree of cyanosis, presence of RV failure and echocardiographic observations on RV growth, residual pulmonary stenosis and tricuspid regurgitation were noted. Complete biventricular circulation was considered to have been achieved if there was no clinical cyanosis (SaO2 > 96%) and echocardiograhic features of at most mild RV hypoplasia and absence of predominantly right to left shunt across the interatrial communication on color Doppler if it has not been closed surgically or by a device.
Subsequent procedures. All survivors from both groups were subjected to cardiac catheterization four to six months after the primary procedure if significant RV outflow obstruction remained on Doppler echo (peak systolic gradient > 25 mm Hg). Balloon dilation was performed if the stenosis was at valvar level, and likewise for RVOT reconstruction for subvalvar obstruction. All survivors in group 2 who were deemed to have achieved complete biventricular circulation underwent further cardiac catheterization at 18 to 24 months (mean 21 months) of age for coil occlusion of the BT shunt. In both groups, for patients who remained cyanosed after the primary procedure despite having no significant RVOT obstruction (peak systolic gradient < 25 mm Hg) but continued to have mild to moderate RV hypoplasia, a trial closure of the interatrial communication/patent foramen ovale (PFO) using a balloon catheter and followed by Amplatzer Septal Occluder (ASO) device (AGA Medical Corporation, Golden Valley, Minnesota) was performed. If the systemic pressure dropped by more than 20% of the baseline and/or central venous pressure (CVP) increased to >15 mm Hg, the RV was considered inadequate for complete biventricular circulation. The ASO device was then removed and the patient was subjected to partial biventricular repair, i.e., creation of bidirectional Glenns shunt and closure of PFO. In patients who could tolerate closure of the PFO using the ASO device, a dobutamine challenge was then performed at incremental doses of 5 and 10 µg/kg/min for 10 min each. If the hemodynamics remained stable, the device was then released permanently and the patient was considered to have achieved complete biventricular circulation.
Statistical analysis. The nonparametric Wilcoxon rank sum test and the Mann-Whitney U test were used to compare the continuous variables. Comparison of dichotomous variables was made using the Fisher exact test. Statistical significance was assumed at 5% level.
| Results |
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Two other patients attained reasonable RV growth (Z +0.6 and +0.1, respectively), albeit with mild cyanosis, but the parents are hesitant for transcatheter closure of the PFO.
Two of the 16 patients (12.5%) in group 1 failed to achieve complete biventricular circulation. The Z values of the tricuspid valve were -3.5 and -4.0 at initial presentation. They both received bidirectional Glenns shunt and closure of the PFO at six and eight months after the primary procedure.
In one patient, who was severely cyanosed at eight months post-RF valvotomy due to poor RV growth (Z = 3.4), trial closure of PFO eliminated the cyanosis but resulted in hypotension and elevated CVP after 10 min, and the device was then removed. However, at 18 months, despite surgical closure of the PFO at the time of the Glenns shunt construction, he still had bidirectional shunting through a residual interatrial communication. It was successfully occluded with an ASO device (Fig. 3). In the other patient, trial closure was not undertaken, as the RV was deemed too small (Z = 6) to support the pulmonary circulation (Fig. 4).
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Follow-up and late outcome
The survivors (n = 8) in this group had been followed up for a mean of 51 ± 20.3 months (33 to 96 months). Seven patients who were deemed to have complete biventricular circulation had their BT shunt occluded with Gianturco coils. Five patients did not require any further intervention. Two patients underwent transcatheter closure of the PFO at three and eight years of follow-up. The remaining patient is awaiting BT shunt occlusion and trial closure of PFO (Fig. 6 )
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| Discussion |
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While transannular patching provides the greatest possibility of unobstructed forward flow from the RV, the proponents for pulmonary valvotomy have argued that it produces less ventricular damage and pulmonary regurgitation (14). It can also be performed safely without cardiopulmonary bypass. Although it may not completely relieve pulmonary outflow obstruction, a more radical RV outflow reconstruction can be deferred to late infancy when the morbidity and mortality risks can be expected to be lower. Furthermore, in those patients whose residual obstruction is chiefly at valvular level, nonsurgical reintervention by balloon dilation offers a safe and effective alternative (21). This has been our approach in eight patients in group 2.
Transcatheter primary procedure. Transcatheter valvotomy and balloon dilation offer a promising alternative as the primary therapy in selected patients with PA-IVS. Perforation of the atretic pulmonary valve can be achieved using laser guidewire or RF wire, and balloon dilation can then be performed in the conventional way (6,7,22). The sharp, stiff end of a coronary guidewire has been successfully used to perforate the atretic pulmonary valve (23), but this technique has been rendered largely obsolete with the availability of laser and RF wires. The use of laser-based methods has the advantage of using the same guidewire to track the balloon over once the valve has been perforated. In our experience, however, once valvotomy has been achieved with RF wire, the tiny perforation could be recrossed with another guidewire for subsequent balloon dilation in all cases. Furthermore, the risk to staff, limited portability and considerable capital expense favor the use of the RF method (7). Since its introduction, the technical skills for this demanding procedure have improved, the indications have become more precise and more centers have begun to use this approach (2426). Although this technique has been used in patients with infundibular atresia and even those with ventricular septal defect (27,28), it is clear that only patients with membranous valvular atresia and a patent infundibulum, in the setting of a non-RV-dependent coronary circulation, should be considered for this procedure to achieve the best results and avoid serious complications (26). This subgroup of patients generally has a reasonably well-developed RV and therefore the greatest potential for biventricular circulation (4). The one early death in our series was a result of a rare but nevertheless known complication of vessel cannulation in a newborn rather than directly related to the procedure itself.
Assessment of RV size. There continues to be much debate on the best method of assessing right ventricular size and morphology. There are proponents of using complex scoring of right ventricular size (16), a simple measurement of tricuspid annulus diameter (16) or merely visual assessment of how well formed the RV appears to be (17,26). Although we began measuring the Z value of the tricuspid valve in the later part of the study, we concur with Gibbs et al. (26) that the latter, simplest approach is probably sufficient for clinical decision making. Of all the survivors from both groups, the RV has not appeared to grow despite virtual elimination of outflow obstruction in two patients, both of whom underwent percutaneous RF valvotomy as the primary procedure. We speculate that this may have been in part attributable to their late presentation (three and seven months), and hence delayed decompression of the RV. Their tricuspid valve diameter z values were 3.5 and 4.0 at presentation, respectively. However, all is not lost, as the RV can still be incorporated into the circulation, albeit with a reduced volume load, by performing a bidirectional Glenns Shunt and closure of interatrial communication (partial biventricular repair) (18).
Closure of interatrial communication. We have found the ASO, which is retrievable, to be a useful device in determining the potential for complete biventricular circulation in patients who continue to remain cynosed due to inadequate growth of the RV. In patients destined for partial biventricular repair, closure of the PFO would lead to an increase in the CVP and concomitant lowering of the systemic arterial pressure. On the other hand, in those patients whose RV is capable of supporting the entire pulmonary circulation, cyanosis would be eliminated without increasing the CVP and compromising the cardiac output. The device can then be safely deployed permanently. However, we feel that it is important to stretch the capability of the RV by dobutamine stress before deployment.
Subgroup with concomitant subvalvar obstruction. Fixed, subvalvular stenosis is part of the anatomic spectrum of PA-IVS (19). In our experience, this was a cause of failure of perforation of the valve in two patients due to malpositioning of the guiding catheter and RF wire in the intertrabecular recesses. These two patients ( Z = 1.1 and +0.5), who were then subjected to the standard surgical procedure, subsequently died of RV failure at 13 and 36 postoperative days. In retrospect, a more radical RVOT reconstruction, albeit with a higher operative mortality risk, would have been more appropriate. No doubt, the prolonged requirement for inotropic and ventilatory support and eventual death due to inadequate RV decompression have negatively skewed the surgical results significantly. However, in another patient, the procedure was successful, and this has allowed the patient to grow to a reasonable size when a radical RVOT reconstruction could be performed at a lower risk.
Study limitations. As this study is partly retrospective, the Z value of the tricuspid valve as a measure of the RV size was not available in the historical, surgical control group. Nevertheless, the other preintervention echocardiography findings were similar in the two groups, and all patients underwent initial evaluation and selection into the study by the two principal investigators. Second, the majority of patients in the surgical group did not undergo prior cardiac catheterization to exclude RV-dependent coronary circulation. Nonetheless, the two patients in whom right ventriculo-coronary connections were noted on echocardiography were among the survivors. Finally, the patients in the surgical control group received their treatment in a slightly earlier era, and in two patients who died early of RV failure due to inadequate RV decompression, the choice of surgical treatment may not have been appropriate. Therefore, the morbidity and mortality rates and final outcome may not be representative of current surgical results in established institutions (16,18).
Conclusions. From our small series, we conclude that primary treatment with RF valvotomy and balloon dilation compared with surgical valvotomy in this selected group is more efficacious in decompressing the hypertensive RV in that only a small number required a second decompression procedure. It is also associated with lower morbidity, as indicated by lower requirement for ventilation and freedom from potential complications of surgery. Stenting of the PDA in patients requiring prolonged prostaglandin infusion despite absence of significant residual RVOT obstruction, coil occlusion of PDA and transcatheter closure of interatrial communication later in those patients who have attained adequate RV growth offers the exciting prospect that a small number of these patients may be treated entirely in the catheterization laboratory.
The infrequency with which this anomaly occurs makes it difficult to draw strong conclusions from a single institution, but our results argue for further investigation and application of this technique.
| Acknowledgments |
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