| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Ann Thorac Surg 1998;66:668-672
© 1998 The Society of Thoracic Surgeons
a Division of Cardiothoracic Surgery, University of California, San Francisco, California, USA
Address reprint requests to Dr Reddy, Division of Cardiothoracic Surgery, 505 Parnassus Ave, M593, San Francisco, CA 94143-0118
Presented at the Workshop on "One and One-Half Ventricle Repairs," Gubbio, Italy, Dec 6–7, 1996.
Abstract
Background. The bidirectional cavopulmonary shunt has become a mainstay in the palliation of patients with a functional single-ventricle heart. However, there remain a number of unresolved issues regarding this procedure, many of which concern the response of the pulmonary vasculature to this unique circulatory physiology. Among the issues of debate are the role and effects of an additional source of pulmonary blood flow.
Methods. Between January 1990 and April 1997, 160 patients underwent bidirectional cavopulmonary anastomosis. Median age at operation was 7.8 months, and age ranged from 24 days to 43 years. An additional source of pulmonary blood flow was included in 93 patients (58%). A retrospective review of our experience with this cohort was performed with a focus on the role of additional pulmonary blood flow.
Results. Eight patients (5%) died in the early postoperative period, and the overall early failure rate (death or take-down) was 7.5% (n = 12). Eleven other patients underwent early reoperation to decrease (n = 8) or increase (n = 3) the amount of pulmonary blood flow. Early survivors were followed up for a median of 23 months, during which time 5 patients died and 30 patients underwent Fontan completion. Including early and late mortality, actuarial survival rates at 1 and 2 years were 91% and 88%, respectively.
Conclusions. The bidirectional cavopulmonary shunt is a useful procedure in the early or intermediate-term management of patients with a functional univentricular heart. However, there is much still to be learned about this unique physiologic system. The role of accessory pulmonary blood flow remains unclear, as does the use of the bidirectional cavopulmonary shunt as long-term palliation. Pulmonary arteriovenous fistulas are a serious concern, especially in young patients with heterotaxy syndrome.
The bidirectional Glenn anastomosis has become a standard component in the management of single-ventricle patients [1–6]. The advantages of this procedure include relief of the volume load on a single functional ventricle, avoidance of pulmonary artery distortion after pulmonary artery banding or shunts, simplification of the eventual Fontan operation, and possibly prevention of the pulmonary vascular disease that can result from prolonged left to right shunting. Despite these advantages, a number of concerns remain, many having to do with the pulmonary vasculature. For example, pulmonary arteriovenous fistulas [7, 8] and systemic to pulmonary arterial collaterals [9] tend to develop in patients with a bidirectional Glenn circulation, and there is concern that a bidirectional Glenn operation may lead to decreased pulmonary artery growth [10, 11] and uneven distribution of pulmonary blood flow [1, 9, 12]. Several recent reports have specifically addressed the effect on outcomes of adding or maintaining a source of pulmonary blood flow in additional to the cavopulmonary connection [13–17]. Among other things, an additional source of pulmonary blood flow—either antegrade through a patent pulmonary valve or via a systemic to pulmonary arterial shunt—has been advocated as a means of preventing arteriovenous fistulas and stimulating the promotion of pulmonary artery growth [16, 17]. However, there are few published data to substantiate or discredit these assumptions, and the influence of additional pulmonary blood flow on postoperative outcomes has not been well characterized. Since 1990, 58% of 160 patients undergoing the bidirectional Glenn procedure have had additional pulmonary blood flow either antegrade or through a shunt, which provides an excellent opportunity to evaluate the effect of this variation on outcomes after the bidirectional Glenn procedure.
Patients and methods
Patients
Between March 1990 and April 1997, 160 patients underwent a bidirectional Glenn procedure. Median age at operation was 7.8 months, and age ranged from 24 days to 43 years. Thirty-one patients had undergone no prior palliation, whereas the remaining 129 patients had undergone a total of 160 previous palliative operations. Patient diagnoses are summarized in Table 1, and sources of pulmonary blood flow before the bidirectional Glenn procedure are summarized in Table 2.
|
|
Data collection and statistical analysis
Patient records were reviewed retrospectively and cross-sectional follow-up was carried out by means of physician contact or direct review of patient records. Patients were followed up until their most recent physician contact before the time follow-up was conducted or until the date of Fontan completion. Paired t test, independent samples t test, and 
2 analysis were used to compare within-group means, between-group means, and dichotomous variables, respectively. Cox proportional hazards and Kaplan-Meier product limit methods were used for actuarial survival analysis. The focus of the analysis was comparison of preoperative and outcome variables between patients with and without an additional source of pulmonary blood flow. Statistical calculations were performed using SPSS for Windows v.6.01 (SPSS Inc, Chicago, IL).
Results
Early results
Eight patients (5%) died in the early postoperative period and 4 additional patients had the bidirectional Glenn anastomosis taken down, for an overall failure rate of 7.5%. Nine patients (8 with additional pulmonary blood flow) underwent early reoperations to increase (n = 2) or decrease (n = 7) the amount of pulmonary blood flow. All of these were before March 1993. Early outcomes among patients with and without extrapulmonary blood flow are compared in Table 3. Seven of eight early deaths were in patients with additional pulmonary blood flow, which approached statistical significance (p = 0.08). Patients with an additional source of pulmonary blood flow were significantly more likely to have prolonged effusions (p = 0.048), defined as chest tube drainage for greater than 7 days, and had significantly higher pulmonary artery pressure and arterial oxygen saturation.
|
During the follow-up period, there were five late deaths, ranging from 3 to 21 months after the Glenn operation. Actuarial survival did not differ between patients with and without additional pulmonary blood flow.
Follow-up data among patients with and without additional pulmonary blood flow are compared in Table 3. Patients with additional pulmonary blood flow had significantly higher indexed pulmonary blood flow and significantly greater indexed lower lobe pulmonary artery area. Saturations and Glenn pressures did not differ between the groups, and there was no significant difference in pulmonary artery index changes from catheterization before the Glenn procedure to catheterization after the Glenn procedure.
Comment
The fundamental principle of the bidirectional cavopulmonary anastomosis is to relieve the volume load on the single ventricle while providing a controlled source of low-pressure pulmonary blood flow. When the superior caval vein is the sole source of blood flow to the lungs, the physiology is that of a modified in-series circulation, with the ventricle pumping a single cardiac output to the systemic vascular bed. An additional source of pulmonary blood flow may mitigate some of the benefits of a bidirectional Glenn physiology by offsetting the reduction in volume load and increasing the likelihood of pulmonary vascular complications. On the other hand, an additional source of pulmonary blood flow may offer some benefits over a pure cavopulmonary shunt physiology. Increased arterial oxygen saturations may be sufficient to reduce baseline cyanosis, and the additional source of pulmonary flow may allow for modestly improved exercise tolerance. In addition, by providing hepatic blood directly to the lungs, introducing an element of pulsatility to pulmonary flow, and increasing flow rates, an additional source of pulmonary blood flow may reduce the likelihood of pulmonary vascular complications (such as arteriovenous fistulas and aortopulmonary collaterals) and improve pulmonary arterial growth. However, there are no strong data to support these potential benefits, and the relative advantages of additional pulmonary blood flow remain in question.
In previously reported series, patients with additional pulmonary blood flow have had significantly higher arterial oxygen saturations in the early postoperative period, although not necessarily at follow-up [13, 14, 16, 17]. This is the pattern we observed in our patients as well, and may be due in part to the development of aortopulmonary collateral arteries over time in patients without an additional source of flow, which serves to increase the ratio of pulmonary to systemic blood flow. Similarly, we and others have found that Glenn pressures are higher among patients with additional pulmonary blood flow [14]. Although pressures were higher in the early postoperative period in our series, they did not differ significantly at follow-up. Recruitment of aortopulmonary collaterals may also contribute to the trend toward more similar pressures over time. Although we found no difference in the percentage of patients with and without additional pulmonary flow in whom aortopulmonary collaterals developed, no reasonable estimation of the contribution of flow was made, except in the select group of patients who underwent coil embolization.
High morbidity in the early postoperative period has been noted among patients with additional pulmonary blood flow, in the form of both a higher incidence of prolonged effusions [13, 15] and longer hospital stay [15], and this has been the case in our series as well. The most striking finding of our analysis is that seven of eight early deaths occurred in patients with additional pulmonary blood flow. Although this preponderance was not statistically significant, it is very concerning. Another group has found a significantly higher late mortality among patients with additional pulmonary flow [15]. Patients with additional pulmonary blood flow also had a much higher incidence of early reoperation for adjustment of pulmonary blood flow, although no patient has undergone early reoperation for this reason since March 1993. The higher mortality and reoperation rate may reflect the more complicated nature of many of the patients who required additional pulmonary flow.
Our results leave some question about the effect of additional pulmonary blood flow on pulmonary vascular complications. Interestingly, both of the patients in the present study who had clinically significant pulmonary arteriovenous fistulas were 2 months of age or less at the time of the Glenn procedure, had heterotaxy syndrome, and did not have an additional source of pulmonary blood flow. Although a recent study using contrast echocardiography to assess for the presence of pulmonary arteriovenous fistulas found a similar prevalence of fistulas in patients with and without an additional source of pulmonary blood flow [7], it is still not known what effects pulsatile pulmonary blood flow carrying hepatic venous blood may have on the development of pulmonary arteriovenous fistulas. Thus, despite our preference to perform the bidirectional Glenn procedure when the patient is young [6], our clinical experience with these 2 patients, as well as evidence that patients with polysplenia may be especially prone to the development of pulmonary arteriovenous fistulas [18, 19], suggests that the risks of performing a bidirectional Glenn operation in very young infants with heterotaxy may be prohibitive. In such patients we now leave an additional source of pulmonary blood flow, even if it provides only a small amount of flow.
A number of investigators have also expressed concern regarding the effect of reduced, and sometimes unequally distributed, blood flow on the growth of the pulmonary vasculature [1, 13–17]. Our own data suggest that pulmonary arterial growth is not significantly reduced after a bidirectional Glenn operation [20]. Two groups, both of which reported small series of patients, have found that pulmonary arterial size increased more (or decreased less) among patients with additional pulmonary blood flow who underwent a bidirectional Glenn procedure relative to those in whom additional pulmonary flow was not used [16, 17]. Despite the fact that all of the studies on pulmonary arterial growth after the Glenn operation lack data on early postoperative pulmonary artery size, which is a substantial shortcoming, a prior bidirectional Glenn operation has not had adverse effects on outcomes after the Fontan procedure, suggesting that growth of the pulmonary arteries is not a significant concern with short-term Glenn palliation, regardless of whether additional pulmonary blood flow is present.
Although we have a large series of patients with substantial numbers of patients with and without additional pulmonary blood flow, there was undoubtedly a selection bias in determining patients in whom additional pulmonary flow was left or placed. Our current approach is to allow antegrade sources of pulmonary blood flow to remain patent by banding the pulmonary artery at the time of the Glenn procedure, or by tightening the band if the pulmonary artery has already been banded. If the pulmonary valvar orifice is sufficiently small, banding may not be necessary, and only a very small volume of flow may reach the pulmonary circulation via the antegrade route. In patients with a prior arterial shunt, the shunt is generally removed, because the cavopulmonary anastomosis is performed at the same site. When patients have a prior shunt that inserts on the pulmonary artery at a point removed from the location of cavopulmonary anastomosis, hemodynamics are generally evaluated with and without the shunt clamped and a decision is made on the basis of the pulmonary artery pressures and systemic saturations. A shunt is generally added only if the arterial partial pressure of oxygen is less than approximately 30 mm Hg. Additional pulmonary blood flow is added in all patients beyond toddler age.
Ultimately, the effects of an additional source of flow on the pulmonary vasculature can only be addressed adequately with properly randomized studies, although the anatomic and physiologic variability of single-ventricle patients and the exigencies of perioperative management will make such studies unlikely.
References
This article has been cited by other articles:
|
|
 |
|
  B. E. Kogon, C. Plattner, T. Leong, J. Simsic, P. M. Kirshbom, and K. R. Kanter The bidirectional Glenn operation: A risk factor analysis for morbidity and mortality. J. Thorac. Cardiovasc. Surg., November 1, 2008; 136(5): 1237 - 1242. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. F. Calvaruso, A. Rubino, S. Ocello, N. Salviato, D. Guardi, D. F. Petruccelli, A. Cipriani, K. Fattouch, S. Agati, C. Mignosa, et al. Bidirectional Glenn and Antegrade Pulmonary Blood Flow: Temporary or Definitive Palliation? Ann. Thorac. Surg., April 1, 2008; 85(4): 1389 - 1396. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. G. Gray, K. Altmann, R. S. Mosca, A. Prakash, I. A. Williams, J. M. Quaegebeur, and J. M. Chen Persistent Antegrade Pulmonary Blood Flow Post-Glenn Does Not Alter Early Post-Fontan Outcomes in Single-Ventricle Patients Ann. Thorac. Surg., September 1, 2007; 84(3): 888 - 893. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Baslaim Effect of patent ductus arteriosus stenting on subsequent bidirectional Glenn anastomosis: A word of caution J. Thorac. Cardiovasc. Surg., April 1, 2006; 131(4): e3 - e4. [Full Text] [PDF]
|
|
|
|
 |
|
 G H Tatum, G Sigfusson, J A Ettedgui, J L Myers, S E Cyran, H S Weber, and S A Webber Pulmonary artery growth fails to match the increase in body surface area after the Fontan operation Heart, April 1, 2006; 92(4): 511 - 514. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. A. Berdat, E. Belli, F. Lacour-Gayet, C. Planche, and A. Serraf Additional Pulmonary Blood Flow Has No Adverse Effect on Outcome After Bidirectional Cavopulmonary Anastomosis Ann. Thorac. Surg., January 1, 2005; 79(1): 29 - 36. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 X.-J. Luo, J. Yan, Q.-Y. Wu, K.-M. Yang, J.-P. Xu, and Y.-L. Liu Clinical Application of Bidirectional Glenn Shunt with Off-Pump Technique Asian Cardiovasc Thorac Ann, June 1, 2004; 12(2): 103 - 106. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Caspi, T. W. Pettitt, T. B. Ferguson Jr, A. R. Stopa, and S. K. Sandhu Effects of controlled antegrade pulmonary blood flow on cardiac function after bidirectional cavopulmonary anastomosis Ann. Thorac. Surg., December 1, 2003; 76(6): 1917 - 1921. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. M. Bradley, J. M. Simsic, and D. M. Mulvihill Hypoventilation improves oxygenation after bidirectional superior cavopulmonary connection J. Thorac. Cardiovasc. Surg., October 1, 2003; 126(4): 1033 - 1039. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
