Fenestration Improves Clinical Outcome of the Fontan Procedure
A Prospective, Randomized Study
Background— The Fontan procedure is the definitive operation for palliation of complex congenital heart disease with single-ventricle physiology. Fenestration of the Fontan circuit allows for shunting of deoxygenated blood to the systemic circulation. This procedure improved the clinical outcomes of patients who are at high risk for poor Fontan results. However, it is controversial whether fenestration is beneficial for standard-risk patients.
Methods and Results— This prospective, randomized trial evaluated the clinical utility of fenestration in patients with standard preoperative risk profiles for Fontan surgery. Forty-nine consecutive patients were assigned to undergo either a fenestrated (25 patients) or nonfenestrated (24 patients) Fontan procedure. The fenestrated and nonfenestrated groups were comparable with respect to age (P=0.944), body surface area (P=0.250), number of preoperative risk factors for poor outcome (P=0.681), cardiopulmonary bypass time (P=0.302), number of patients who required aortic cross-clamping (P=0.240), preoperative oxygen saturation (P=0.101), and number of patients with dominant left ventricular morphology (P=0.534). Patients in the fenestrated group had 55% less total chest tube drainage (P=0.036), 41% shorter total hospitalization (P=0.018), and 67% fewer additional procedures in the postoperative period (P=0.006) than those in the nonfenestrated group.
Conclusions— Baffle fenestration performed at the time of Fontan surgery improves short-term outcome in standard-risk patients by decreasing pleural drainage, hospital length of stay, and need for additional postoperative procedures.
Received August 24, 2001; revision received October 31, 2001; accepted November 5, 2001.
Fenestration of the Fontan circuit, first described in 1990, decreases postoperative morbidity and mortality rates in high-risk patients.1 The benefit of fenestration is attributable to the improved cardiac output resulting from right-to-left shunting at the atrial level. Preload to the systemic ventricle is increased when conditions that limit pulmonary blood flow are present. In addition, baffle fenestration limits the postoperative increase in systemic venous pressure that commonly develops. However, these benefits come at the expense of lower systemic oxygenation, the theoretical risk of paradoxical embolism, and the potential need for intervention to close the fenestration.
Retrospective studies have claimed that Fontan fenestration causes low morbidity, decreased pleural drainage, and shorter hospitalization among high-risk patients.1,2 Consequently, the fenestrated Fontan procedure has become the preferred procedure for the high-risk population. However, baffle fenestration is controversial in standard-risk patients. Although some retrospective studies of standard-risk patients have reported no benefit from fenestration,3,4 another retrospective study showed decreased Fontan failure rate and decreased occurrence of significant pleural effusions with fenestration of the Fontan baffle.5 The purpose of our study was to evaluate the utility of the fenestrated Fontan procedure in a single-institution, prospective, randomized investigation comparing clinical outcomes of patients with similarly low preoperative risk profiles.
The study population consisted of all 54 patients referred to Children’s Medical Center of Dallas, for an elective Fontan procedure from May 1997 through September 2000 who demonstrated ≤2 risk factors. Consent could not be obtained in 5 patients. Therefore, 49 patients were enrolled in the investigation. The institutional review board of The University of Texas Southwestern Medical School approved the study. Informed consent was obtained from the parents of all patients except for one patient who was legal age. All procedures followed were in accordance with institutional guidelines.
Patients were assigned to undergo either a fenestrated or nonfenestrated Fontan procedure, based on a table of randomly generated numbers. Preoperative clinical data were collected and compared to ensure appropriate randomization. Intention to treat determined group assignment for primary analysis. However, 2 patients who were randomized to receive a fenestration were found after surgery to have no communication between the Fontan baffle and the atrium because of technical problems. This was suspected when oxygen saturation was >94% in the early postoperative period. Echocardiography and cardiac catheterization confirmed the absence of a fenestration in both patients. Therefore, a secondary analysis was performed in which these patients were included in the nonfenestrated group and compared with the effectively fenestrated cohort.
The following preoperative risk factors for poor outcome after the Fontan procedure were assessed: elevated mean pulmonary artery pressure (>15 mm Hg), elevated pulmonary vascular resistance (>2 mm Hg/L per min/m2), pulmonary artery distortion, elevated ventricular filling pressure (≥12 mm Hg), atrioventricular valve regurgitation, and non–sinus rhythm.6–15
Preoperative evaluation consisted of ECG, transthoracic echocardiogram, and complete cardiac catheterization. Mean pulmonary arterial pressures were measured with fluid-filled catheters either directly or indirectly as pulmonary venous wedge pressures. If a patient had different pressures in the right and left pulmonary arteries, the higher of the two values was used. If there were 2 separate sources of pulmonary blood flow or if measured pressures were different in each lung, the pulmonary vascular resistance was not calculated. Patients whose pulmonary vascular resistance could not be measured were assigned as a risk factor only if the patient had elevated pulmonary artery pressure. Pulmonary artery distortion was defined as angiographic demonstration of peripheral pulmonary artery stenosis or hypoplasia, or discontinuity of the pulmonary arteries.2 This was a subjective assessment. Ventricular filling pressure was directly measured as the mean pressure in the atrium that filled the systemic ventricle. The degree of systemic atrioventricular valve regurgitation was assessed semiquantitatively by angiography and echocardiographic color Doppler, primarily based on width of jet origin. The regurgitation jet was graded as none, mild, moderate, or severe. Rhythm was assessed with preoperative ECG and Holter monitor if required. Coil occlusion of large aortopulmonary collaterals was performed before surgery. A prior bidirectional Glenn or a hemi-Fontan procedure was performed in 84% of the fenestrated and 88% of the nonfenestrated patients (P=0.726).
Intraoperative and Postoperative Treatment
Patients underwent either a lateral tunnel Fontan procedure (6 patients) or an extracardiac Fontan procedure (43 patients), based on the surgeon’s preference. The extracardiac Fontan channel was constructed in one of two ways: a tube graft from the inferior vena cava to the pulmonary artery (19 patients) or an extracardiac tunnel constructed along the lateral aspect of the right atrium (24 patients). The different surgical techniques were evenly distributed among the two study populations (P=0.866). The fenestration consisted of a single 3- to 6-mm communication between the Fontan channel and the pulmonary venous atrium.
Postoperative treatment typically included administration of digoxin, captopril, and aggressive use of diuretics. All patients were treated with aspirin (81 mg per day) beginning on the second postoperative day. To maximize caloric intake, patients were not fluid restricted after the initial postoperative period. Chest tubes were left in place until drainage was <3 mL/kg in a 24-hour period. A chest tube was reinserted only if a symptomatic pleural effusion was diagnosed. Chemical pleurodesis was performed after 2 to 3 weeks of persistent drainage. The attending cardiologist and surgeon determined the need for and timing of postoperative cardiac catheterization. There were no differences in postoperative intensive care unit practices and discharge criteria between fenestrated and nonfenestrated patients. Hemodynamic and respiratory stability and a stable heart rhythm generally determined discharge from the intensive care unit. Oxygen saturation and oxygen requirement were not discharge criteria.
Assessment of Outcomes
The primary end point was length of hospital stay. Other outcome variables included length of stay in the intensive care unit, total days of chest tube drainage, total quantity of chest tube drainage, number of additional procedures required in the postoperative period, occurrence of stroke, and number of readmissions to the hospital within 30 days of discharge. All end points were defined a priori. Survival was not defined as an outcome variable. The day of surgery counted as day 1 for all variables. All extra procedures in the postoperative period were counted. These included returning to the operating room for bleeding or poor hemodynamics, replacement of chest tubes, pleurodesis, pericardiocentesis, cardiac catheterization, and late fenestration.
Sample size estimates were based on a previous retrospective investigation of the Fontan procedure,2 with 80% power to avoid a type II statistical error. Descriptive statistics were calculated for all variables. Medians and ranges described continuous variables. Categorical variables were summarized as frequencies. The Mann-Whitney U test was used for all continuous variables; χ2 analysis and Fisher’s exact test were applied for all dichotomous variables. Survival data for hospital length of stay, intensive care unit length of stay, and length of chest tube drainage were compared by means of a Cox proportional hazards test to account for a patient who was censored because of death (pulmonary embolus) within the study period. A probability value of <0.05 indicated statistical significance. All calculations were performed with Statview Statistical Software.
Preoperative and perioperative characteristics of each group are summarized in Table 1. There were no statistically significant differences in age, body surface area, number of risk factors, morphology of the systemic ventricle, preoperative oxygen saturation, cardiopulmonary bypass time, or number of patients who required intraoperative cross-clamping of the aorta. Table 2 (fenestrated patients) and Table 3 (nonfenestrated patients) list the primary diagnosis, previous procedures, age, relevant risk factors, and length of hospitalization for each patient.
Table 4 lists the results of the intention-to-treat analysis. The number of hospital days, duration of chest tube drainage, total amount of pleural drainage, number of additional procedures, and number of patients who required additional procedures and postoperative oxygen saturation were significantly decreased in the fenestrated group. Patients in the nonfenestrated group were hospitalized for 8 additional days and required 3 times the number of additional procedures as the nonfenestrated patients. Comparison of effectively fenestrated patients with nonfenestrated patients (Table 5) underscores these findings. For example, the patients with an effective fenestration had a much shorter duration of chest tube drainage (Figure 1). Furthermore, the difference in the median number of hospital days between the effectively fenestrated and nonfenestrated patients was considerable (12 days versus 23 days). However, there was significant overlap between the 2 groups (Figure 2) with regard to this outcome measure.
Although there was no significant difference in the number of readmissions between the study groups in either analysis, readmissions accounted for additional morbidity in the nonfenestrated group. Five patients accounted for 7 readmissions in the nonfenestrated group compared with 1 readmission in the fenestrated group. In the nonfenestrated group, readmissions accounted for 113 additional hospital days and 12 additional procedures compared with 9 additional hospital days and 2 additional procedures in the fenestrated group. The incidence of stroke was not statistically different in either comparison.
Non-sinus rhythm occurred in 6 patients (12%) in the postoperative period. The rhythm disturbances included 4 patients with junctional rhythm (1 patient with preoperative junctional rhythm), 1 patient with junctional ectopic tachycardia, and 1 patient with intermittent heart block. Four patients with rhythm disturbances were fenestrated, whereas 2 were in the nonfenestrated group (P=0.67).
Late fenestration was performed on 3 patients who did not initially receive an effective fenestration. One patient returned to the operating room on postoperative day 2 because of poor hemodynamics defined as significant hypotension, metabolic acidosis, and kidney failure despite inotropic support and volume resuscitation. Two patients underwent late creation of a fenestration because of prolonged pleural drainage. One fenestration was performed after 55 days of persistent drainage and the other was completed after the third readmission for pleural drainage. All 3 patients had significant clinical improvement after late fenestration. No patients required takedown of the Fontan baffle.
Though Fontan fenestration has been used commonly in high-risk candidates, its use in standard-risk patients remains controversial, primarily because of a lack of prospective investigation in this population. This study represents the first prospective, randomized trial to assess the clinical outcome of fenestrating standard-risk Fontan patients. The presence of a fenestration was associated with significant clinical benefits, including shorter hospital stays, decreased pleural drainage, and fewer additional procedures performed during the hospitalization. When the analysis was extended to compare effectively fenestrated patients with nonfenestrated patients, the outcome differences were confirmed at an even higher level of statistical significance. It is particularly noteworthy that the median length of stay for the effectively fenestrated patients was 11 days shorter than the median length of stay for the nonfenestrated patients. Additionally, 52 fewer postoperative procedures were required in the effectively fenestrated cohort.
These findings are consistent with previous retrospective reports, which demonstrated that high-risk and standard-risk patients who underwent a fenestrated Fontan procedure had less pleural drainage, shorter hospitalizations, and a decreased Fontan failure rate compared with nonfenestrated patients.2,5 In contrast, other retrospective studies have suggested that standard-risk patients undergoing the Fontan procedure do not require routine fenestration.3,4 These studies found that preoperative risk factors do not identify a priori those patients who had significant pleural effusions. We agree that not every patient undergoing Fontan palliation requires fenestration to achieve a good outcome. In fact, we observed that a number of nonfenestrated patients had hospital courses similar to those of fenestrated patients. From this we infer that baffle fenestration is able to improve outcome in those who are predisposed to persistent pleural drainage and poor postoperative hemodynamics. Unfortunately, it is currently impossible to identify this subgroup of the standard-risk population before surgery. Once nonfenestrated patients with a propensity to prolonged pleural drainage were identified after surgery, we were able to demonstrate substantial clinical improvement after late fenestration. This is consistent with a previous report that showed significant improvement after late transcatheter fenestration dilation or creation.16
It has been suggested that fenestration increases the risk of stroke by providing a pathway for systemic venous emboli to enter into the systemic circulation. However, a previous retrospective study showed no statistical difference in the number of strokes between fenestrated and nonfenestrated patients despite selection of higher-risk children for the fenestrated group.17 The two patients who had a stroke in the current study were in the nonfenestrated cohort. Although our study did not have adequate power to exclude differences between groups relative to rare occurrences such as stroke, our experience is consistent with a previous study that demonstrated that fenestration did not contribute to the occurrence of systemic thromboembolism in 126 patients with a Fontan procedure.5
This report did not address the long-term fate of fenestrated Fontan patients. Clearly, there are some patients who will require fenestration closure because of low systemic oxygen saturation. However, the proper timing and clinical benefit of fenestration closure in normally saturated and mildly desaturated patients remain unknown. It has been reported that 29% of fenestrations will close spontaneously within 3 months.18 Furthermore, multiple centers have shown that a fenestration can be safely closed with a device in the cardiac catheterization laboratory18–20 and that such closures are well-tolerated.21 At our institution, we have not routinely occluded fenestrations unless there is significant cyanosis without an alternative cause. Follow-up of this randomized cohort may provide additional insights into effective long-term treatment.
Although this is a large, single-institution, prospective, randomized experience in a narrowly defined time period for the Fontan procedure in a standard-risk population, its relatively small numbers and short follow-up period limit our statistical analysis of infrequently occurring outcomes including stroke, death, and hospital readmission. As with most pediatric thoracic surgical series, we were limited by the heterogeneity in the preoperative diagnosis and the techniques used.
In conclusion, this prospective, randomized study demonstrates that fenestration at the time of the Fontan procedure significantly improves short-term clinical outcome in the standard-risk population. Therefore, we suggest that all patients undergo Fontan fenestration until the subgroup of children at negligible risk for persistent pleural drainage or poor postoperative hemodynamics can be accurately identified in the preoperative period.
Bridges ND, Lock JE, Castaneda AR. Baffle fenestration with subsequent transcatheter closure: modification of the Fontan operation for patients at increased risk. Circulation. 1990; 82: 1681–1689.
Bridges ND, Mayer JE, Lock JE, et al. Effect of baffle fenestration on outcome of the modified Fontan operation. Circulation. 1992; 86: 1762–1769.
Hsu DT, Quaegebeur JM, Ing FF, et al. Outcome after the single-stage, nonfenestrated Fontan procedure. Circulation. 1997; 96 (suppl II): II-335–II-340.
Castaneda A. From Glenn to Fontan: a continuing evolution. Circulation. 1992; 86 (suppl II): II-80–II-84.
Driscoll DJ, Offord KP, Feldt RH, et al. Five- to fifteen-year follow-up after Fontan operation. Circulation. 1992; 85: 469–496.
Mair DD. The Fontan procedure: what have we learned and accomplished? ACC Curr J Rev. 1998; May/June: 52–55.
Cohen MI, Wernovsky G, Vetter VL. Sinus node function after a systematically staged Fontan procedure. Circulation. 1998; 98: (suppl II): II-352–II-359.
Sommer RJ, Recto M, Golinko RJ, et al. Transcatheter coil occlusion of surgical fenestration after Fontan operation. Circulation. 1996; 94: 249–252.
Goff DA, Blume ED, Gauveau K, et al. Clinical outcome of fenestrated Fontan patients after closure: the first 10 years. Circulation. 2000; 102: 2094–2099.