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Eur J Cardiothorac Surg 2003;23:728-734
© 2003 Elsevier Science NL
Department of Paediatric Cardiac Surgery, Collegium Medicum, Jagiellonian University, 265 Wielicka St., 30-663 Cracow, Poland
Received 1 October 2002; received in revised form 20 January 2003; accepted 23 January 2003.
* Corresponding author. Tel.: +48-12-568-1023; fax: +48-12-657-3947
e-mail: mimalec{at}cyf-kr.edu.pl
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Abstract |
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 Top Abstract 1. Introduction2. Materials and methods3. Results4. DiscussionAppendix A. DiscussionReferences |
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2 test, Mann–Whitney's and Student's t-tests) and multiple regression analysis were carried out. Results: In Group 1, circulatory collapse requiring resuscitation occurred in 15 (48.4%) children, within 72 h after the procedure. The resuscitation was unsuccessful in nine (29%) cases. The operative mortality (30 days) was 35%. In Group 2, two (5%) children died within the early and two (5%) within the late postoperative period. The postoperative course in the remaining children from Group 2 was uneventful. In Group 2 there was a significantly higher mean diastolic pressure after NP (P<0.05). The arterial pulse pressure after NP was significantly lower in Group 2 (P<0.05). Before HF, the application of RV-PA was associated with a lower Qp:Qs ratio (P=0.020), lower aortic pulse pressure (P=0.004) and lower aortic oxygen saturation (P=0.039). Conclusions: A stable haemodynamic status due to independent coronary perfusion, higher diastolic and lower pulse pressure is the most advantageous effect of RV-PA, resulting in a lower mortality and morbidity after NP. A lower Qp:Qs ratio eliminates the danger of the ventricular volume overload and ensures good conditions for the development of the pulmonary circulation before HF.
Key Words: Hypoplastic left heart syndrome • Norwood procedure • Haemodynamic status
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1. Introduction |
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TopAbstract1. Introduction2. Materials and methods3. Results4. DiscussionAppendix A. DiscussionReferences |
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2. Materials and methods |
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TopAbstract1. Introduction2. Materials and methods3. Results4. DiscussionAppendix A. DiscussionReferences |
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The diagnosis of hypoplastic left heart syndrome was based on two-dimensional and colour flow Doppler transthoracal echocardiography and was limited to patients with mitral stenosis or atresia, aortic stenosis or atresia with diminutive left ventricle and systemic right ventricular circulation. Children with coexisting cardiac anomalies were excluded from the study.
All the children in Group 1 underwent the classic Norwood procedure and the surgical technique remained constant. Following the standard midline sternotomy incision, the cardiopulmonary bypass was established by cannulation of the proximal main pulmonary artery and right atrium. The right and left branch pulmonary arteries were occluded and systemic cooling was begun. The circulation was arrested at a rectal temperature of 20°C and the branch vessels of the aortic arch were occluded. The cardioplegia solution (potassium cardioplegia: 0.9% NaCl with 16 mmol/l KCl, 4°C, 15 ml/kg) was administered through the pulmonary artery cannulation site after clamping the descending thoracic aorta. Through the atrial appendage purse string the septum primum was excised, creating a large interatrial communication. The standard procedure involved transecting the pulmonary artery proximal to the bifurcation and closing the distal pulmonary artery using a small patch of homograft. The ductus arteriosus was ligated, transected and then the ductal tissue was excised. The ascending, transverse and descending aorta were reconstructed with pulmonary artery homograft. The proximal pulmonary artery was then anastomosed to the ascending aorta. During the rewarming, a modified right BT shunt from the brachiocephalic artery to the right pulmonary artery using a polytetrafluoroethylene tube (IMPRA® ePTFE Vascular Graft, BARD, Tempe, USA) (3.5 mm in six children weighing less than 3 kg and 4 mm in 25 patients) was created to supply the pulmonary blood flow.
In Group 2, during the midline sternotomy, another surgeon performed the anastomosis between a circular homograft patch and a polytetrafluoroethylene (PTFE) tube (5 mm). The surgical technique varied with the ascending aorta size (Figs. 1a,b)
. In the case of a very small (
2.5 mm) diameter of the ascending aorta (in 14 (38%) children), the arterial infusion was ensured by cannulation of the proximal main pulmonary artery. When the circulation was arrested in the deep hypothermia, the potassium cardioplegia was administered through a small puncture in the brachiocephalic artery after clamping the aortic arch. The main pulmonary artery was divided at the level of the branch pulmonary arteries and the distal end was closed using the previously performed anastomosis. The septum primum was excised and the aorta was reconstructed as in the classic Norwood procedure. The cardiopulmonary bypass was reinstituted and during the rewarming a small right ventriculotomy was made about one cm beneath the pulmonary annulus and after then connected to the second end of the PTFE tube (Fig. 1a).
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A delayed sternal closure was performed in five (16%) children in Groups 1 and 7 (19%) neonates in Group 2. The patients were initially managed with dopamine (Dopaminum hydrochloricum, Polfa, Warsaw, PL) and sodium nitroprusside (Naniprus, Pharmachim, Sophia, BG) as required. Sodium nitroprusside (1–3 µg/kg per min) was used when vascular resistance needed to be decreased and dopamine (2–5 µg/kg per min) to improve ventricular function. Between Norwood and hemi-Fontan procedure all the children were treated with acetylsalicylic acid (Acidum acetylsalicylicum, Polpharma, PL) (2–3 mg/kg per h). Some of patients in the early postoperative period received heparin (Heparin Biochemie, Biochemie, A) (5 U/kg per day).
Data were collected on the basis of medical records, operative reports and perfusion reports. The early postoperative period was defined as the first 72 h after the operation. To evaluate the early haemodynamic status the following data were recorded at hourly intervals: heart rate, arterial systolic pressure, arterial diastolic pressure and central venous pressure. The pulse pressure was defined as an amplitude of the arterial pressure. The arterial pressure was measured though a 22G cannula placed into the radial or femoral artery. The following blood gases data from the early postoperative period were also collected: partial arterial oxygen tension (pO2), pH, base excess, bicarbonate concentration (HCO3-) and arterial oxygen saturation (SatO2).
To obtain information about the late haemodynamic status, cardiac catheterisation data were reviewed. Before the hemi-Fontan procedure, cardiac catheterisation was performed in 19 (61%) children in Group 1 aged from 4 to 7.3 months (mean 6.04±1.0 months), weighing from 4.7 to 8 kg (mean 6.10±0.8 kg) and in 12 (32%) infants in Group 2 aged from 4.6 to 7.2 months (mean 5.98±1.0 months) and weighing from 4.5 to 7.6 kg (mean 6.06±0.9 kg). The Qp:Qs ratio was calculated using standard formulas. Data from routine blood tests performed before catheterisation (haematocrit value, haemoglobin concentration) were also collected.
The data are represented as mean±standard deviation and range. The statistical analysis was carried out by means of descriptive statistics, 2 test (Yates correction), Mann–Whitney's test and Student's t-test. The multivariate analysis of variables found to be significant by the univariate analysis, was performed using the multiple regression. Differences were considered statistically significant at a P value of <0.05.
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3. Results |
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TopAbstract1. Introduction2. Materials and methods3. Results4. DiscussionAppendix A. DiscussionReferences |
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The circulatory arrest time in deep hypothermia was significantly (P<0.001) shorter in Group 2 (mean 41.7±10.8 min, 25–61 min) than in Group 1 (mean 54.1±6.6 min, 41–67 min), without significant prolongation of the cardiopulmonary bypass time (Group 1: mean 70.5±24.4 min, 48–167 min; Group 2: mean 67.0±18.1 min, 39–121 min; P=0.983).
In the early postoperative period, the heart rate, arterial systolic pressure and central venous pressure were not significantly different between the two groups. Significant differences were apparent with respect to the arterial diastolic pressure at 4, 8, 12, 24, 36 and 42 h after the operation (P<0.001, P<0.001, P<0.001, P<0.001, P=0.004, P=0.029, respectively) (Fig. 2) , as well as in the case of the arterial pulse pressure at 8, 12, 24, 36, 48 and 72 h after the operation (P=0.006, P=0.004, P=0.013, P=0.029, P<0.001, P=0.004, respectively) (Fig. 3) . The blood gases values: partial arterial oxygen tension, pH, base excess, bicarbonate concentration and arterial oxygen saturation did not significantly differ between these two groups.
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4. Discussion |
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TopAbstract1. Introduction2. Materials and methods3. Results4. DiscussionAppendix A. DiscussionReferences |
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The most common method of the limitation of the excessive pulmonary flow used to be hypoventilation (to maximise pulmonary vascular resistance by the reduction of the inspired oxygen fraction and minute ventilation) [7,8]. To reduce pulmonary overcirculation children were successfully treated with inspired carbon dioxide [9,10]. The addition of carbon dioxide to the inspired gas mixture was thought to help avoid the adverse effects of the hypoventilation [9]. Another major method of regulating the systemic and pulmonary resistance was pharmacotherapy. There was a general tendency not to use high doses of inotropic agents, which can increase systemic resistance and increase shunt perfusion pressure. To reduce the systemic resistance, sodium nitroprusside and phenoxybenzamine were recommended [9,11]. To decrease the high reactivity of the neonatal pulmonary circulation, the use of high-dose fentanyl (>50 µg/kg) was proposed, both intra- and postoperatively [8].
Many authors emphasised the importance of the shunt diameter size in the control of the pulmonary blood flow and suggested that postoperative conditions were considerably more stable after the application of smaller shunts [12–14].
The idea of the application of a right ventricle-to-pulmonary artery shunt in the first stage palliation for HLHS comes from the pioneering work of William Norwood (1981; valved Hancock and non-valved PTFE conduits) [1,15]. The application of conduits with a too large diameter (8 and 12 mm) was probably the cause of the first negative experience and this technique was abandoned for years. Recently, a few reports have appeared, mostly from Japanese cardiac surgery centres, describing the application of right ventricle-to-pulmonary artery shunts (xenopericardial conduit with a bicuspid valve 6 mm in diameter [16] and PTFE graft 4, 5 or 6 mm in diameter [17,18]).
The fundamental advantage of RV-PA is that coronary perfusion is independent of the pulmonary-to-systemic flow ratio. Independent coronary perfusion results in a very stable postoperative course. The location of the proximal shunt end beneath the valve of the systemic circulation significantly increases the systemic diastolic pressure, which was observed in our patients and noted by other authors [17,18]. As a consequence, the systemic pulse pressure decreases and this haemodynamic change was occurred both in the early and late postoperative period.
The crucial role of the coronary perfusion affecting the results after the Norwood procedure was proved by previous reports. In the large pathologic study of 122 post-mortem cases the most important cause of death after stage I palliation for HLHS was found to be impairment of coronary perfusion [15]. Some studies have also shown that the administration of high-dose fentanyl reduces the incidence of ventricular fibrillation in neonates with HLHS, probably due to stabilisation of the pulmonary resistance, and in this way it also stabilises coronary perfusion [19]. The abnormal pattern of coronary blood flow (the lack of coronary perfusion during diastole) in children with BT was considered the main reason for unexpected late deaths. Some authors have suggested that a significantly decreased risk of death after the hemi-Fontan procedure, is associated with the occlusion of BT [20].
The traumatisation of the only ventricle by a ventriculotomy did not significantly influence the heart rate or the systolic pressure. According to the early analysis [21] a small ventriculotomy did not have an adverse effect on the right ventricle function. In our opinion it is too early to evaluate late complications of the RV-PA and this problem will need further investigations.
The main haemodynamic consequence of the RV-PA is the significant decrease of the Qp:Qs ratio. This benefit eliminates the need to use hypoventilation or increased concentrations of carbon dioxide in the inspired gas mixture. It also allows for safer administration of higher concentration of oxygen. On the other hand, lower pulmonary blood flow does not change the main blood gases values in the early postoperative period. Our study has shown that in the late postoperative period RV-PA may result in more severe hypoxaemia and in an increase of the haematocrit value and haemoglobin concentration. We did not observe a failure to thrive or embolic complications in our patients. There was also no need to carry out the hemi-Fontan procedure earlier than scheduled. The lower Qp:Qs ratio allows for avoiding a large ventricular volume overload and ensures good conditions for the development of the pulmonary vasculature (the pulmonary vein mean pressure was lower in patients with RV-PA than in infants with BT). We believe that the good development of the pulmonary arteries is related to the increased pulsatility of forward pulmonary flow from a pumping ventricle. The patients with RV-PA are thus good candidates for the hemi-Fontan procedure.
The opportunity of the ascending aorta or brachiocephalic artery cannulation in children with larger aortic diameter is a fact of a great importance. It significantly decreases the time of cardiac arrest in deep hypothermia and may improve ventricular function in early postoperative period. The completion of the anastomosis between homograft patch and a PTFE tube (distal end of the RV-PA) before median sternotomy can additionally reduce the cardiopulmonary bypass time.
The stable haemodynamic status due to independent coronary perfusion, higher diastolic and lower pulse pressure is the most advantageous effect of the application of the right ventricular-to-pulmonary artery shunt. It results in lower morbidity and mortality after the Norwood procedure. The lower Qp:Qs ratio obviates the possibility of the ventricular volume overload and ensures good conditions for the development of the pulmonary circulation before the hemi-Fontan procedure. More severe hypoxaemia before the hemi-Fontan procedure in our material does not have significant adverse implications.
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Acknowledgments |
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Footnotes |
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Appendix A. Discussion |
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TopAbstract1. Introduction2. Materials and methods3. Results4. DiscussionAppendix A. DiscussionReferences |
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Dr Januszewska: Right ventriculotomy was made about 1 cm beneath the pulmonary annulus and the diameter of the ventriculotomy was about 5 mm. With respect to the late results of this ventriculotomy, 3 weeks ago during the Congress of the European Society of Cardiology in Berlin our cardiologists presented a study which compares the pre and postoperative echocardiographic data and they revealed that the ejection fraction and right ventricle anterior wall shortening fraction did not significantly differ between these two groups preoperatively and postoperatively.
Dr C. Pizarro (Wilmington, Delaware): You clearly improved your results over a short period of time. I think it's a little difficult to ascertain, though, that this modification per se is responsible for all of it, because your circulatory arrest seems to be a little bit different, and the way you reconstructed the last group of patients, besides the RV-to-PA conduit, is also a little bit different. However, I share your enthusiasm for this particular modification. I think that you pointed out quite well that the coronary perfusion is not totally independent from QP/QS ratio and it seems to be improved.
I have two brief questions. When these patients went to have their cath or hemi-Fontan, did you notice any particular difference in terms of pulmonary artery growth? Secondly, did you have to do anything with respect to tricuspid valve regurgitation?
Dr Januszewska: We didn't analyse it statistically, we just made observations. During the hemi-Fontan procedure, we saw that the pulmonary arteries were very well developed. First of all, the right pulmonary arteries were always very good. And incompetent tricuspid valve is not a problem in our material. We did not observe any significant regurgitation of the tricuspid valve.
Dr A. Dodge-Khatami (Utrecht, Netherlands): I have one question. What size shunts do you use? Do you use different size shunts according to weight, and do you think if you had used a bigger size shunt, you would have maybe improved your saturations or QP/QS ratio?
Dr Januszewska: The shunt we use is 5 mm in diameter.
Dr Dodge-Khatami: In all?
Dr Januszewska: Yes, in all.
Dr H. Jalahi (Brisbane, Australia): One of the reasons people moved away from central shunts in the past was the difficulty to access when they used to go to do the hemi-Fontan, and the Blalock-Taussig shunt was conveniently situated next to the right pulmonary artery, leaving all of that left area alone. How difficult has it been for you coming back for a hemi-Fontan to access this side of the aorta, particularly when you do the classical arch augmentation?
Dr Januszewska: All procedures were done by Professor Edward Malec and he did not have such a problem.
Dr D. Quaegebeur (New York, NY): What do you think about the proximal anastomosis between the shunt and right ventricle? We have had patients who acutely obstructed in that area. And has it influenced the timing of restudying for the second stage?
Dr Januszewska: In our material we did not observe such an influence. All the children were treated with aspirin after the procedure. And these two groups, before the hemi-Fontan procedure, during the catheterisation, did not significantly differ with respect to age. So there was no need to perform a hemi-Fontan procedure earlier in our material.
Dr C. Pizarro (Wilmington, Delaware): If I could just make a quick comment in reference to the shunt size. I think shunt size still matters, and when you operate on a very small patient, you really have to downsize the conduit. Before I came here we just operated on a 1.3 kg baby and used a 4 mm RV-to-PA conduit, and that patient still had a significant amount of excessive pulmonary blood flow. We have used a smaller conduit in this patient and in a number of patients under 2.5 kg that we have done so far. So I think that you really have to reduce the shunt size depending on the weight of the patient.
Dr G. Stellin (Padova, Italy): Dr Sano has been reporting (verbally at least) one case who died suddenly before the second stage. Would you like to suggest us to anticipate the second stage repair in order to prevent conduit thrombosis? Did you have any problem with your patients in the postop period with conduit thrombosis?
Dr Januszewska: No, no. Two children died in the late postoperative course but because of sepsis.
Dr Stellin: Do you anticoagulate your patients?
Dr Januszewska: Yes, aspirin. All the children are treated with aspirin.
Dr J. Pajak (Krakow, Poland): Let me offer a few words of my comment on this occluded shunt. This observation was made by our cardiologists. They could see some flow disturbance in the beginning of the shunt, but this had no impact on the pulmonary flow and the pulmonary artery architecture.
Dr F. Lacour-Gayet (Denver, Colorado): I share this enthusiasm for this type of new shunting used by Bill Norwood and recently developed by Dr Sano and your group. You have a very large experience. My personal experience shows also improved results in the operating room and in the ICU. It is clear also that in the midterm, the left pulmonary artery seems a lot better developed than with the previous technique, and this is another advantage of this technique.
My question is on the risk of the ventriculotomy. I would like to outline that at the time of the Glenn, it is possible to totally remove the shunt and totally close the ventriculotomy. Therefore if there has been a ventriculotomy, it is closed. Whether this scar has an impact on the long-term function of the infundibulum, I don't know. I would like to ask you if you have a particular technique to recommend at the time of the Glenn to remove the shunt and also if you have seen aneurysm at the site of implantation of the Gore-Tex.
Dr Januszewska: In our institution, as the second stage we perform a hemi-Fontan procedure, and during this procedure the shunt is completely removed and the ventriculotomy site is occluded using pledget sutures.
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References |
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TopAbstract1. Introduction2. Materials and methods3. Results4. DiscussionAppendix A. DiscussionReferences |
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