Ten-Year Institutional Experience With Palliative Surgery for Hypoplastic Left Heart Syndrome
Risk Factors Related to Stage I Mortality
Background We reviewed 212 consecutive patients who underwent stage I palliative surgery for hypoplastic left heart syndrome (HLHS) at our institution between January 1983 and June 1993.
Methods and Results Six surgeons participated in the care of these patients. Follow-up is 97% complete. Preoperative anatomic and physiological factors and procedural features of the stage I operation were analyzed for impact on stage I mortality, survival to stage II palliation, and actuarial survival. Hospital mortality was not significantly lower during the second half of the study period (P=.242). Operative mortality was 46.2%. Multivariate analysis revealed improved stage I operative survival in patients with mitral stenosis (MS) and aortic stenosis (AS; P=.006). Additional risk factors for stage I mortality were a lower immediately pre–stage I pH (P=.034) and weight <3 kg (P=.015). Overall first-year actuarial survival for MS/AS was 59%, and it was 33% for all others (P=.001). Among stage I survivors, patients with MS/AS were more likely to survive to stage II palliation (P=.031). Analysis of actuarial survival of stage I survivors showed that a smaller ascending aorta (P<.001), aortic atresia (P<.001), and mitral atresia (P=.002) were all risk factors for intermediate death.
Conclusions Preoperative anatomic and physiological state are predictors of stage I mortality. HLHS anatomic subtype also influences intermediate outcome, most notably pre–stage II attrition. These data may be useful in choosing initial management for patients with HLHS.
Hypoplastic left heart syndrome is one of the more common congenital heart defects and is the most common anomaly resulting in death from congenital heart disease during the first year of life in the United States.1 The 1980s witnessed the simultaneous development and implementation of two surgical approaches to the neonate with HLHS. Norwood et al2 3 4 reported the first successful application of staged reconstructive surgery and have subsequently reported sizable series of patients undergoing such a sequence of surgical therapy. Bailey et al,5 6 7 in contrast, have introduced and espoused transplantation in the neonatal period for HLHS. Both of these treatment options have their particular difficulties and limitations. Neonatal cardiac allotransplantation is acutely limited by the supply of suitable donor hearts.8 The reconstructive approach requires a sequence of technically demanding procedures that may be fraught with high operative mortality and significant interstage attrition.9 10 A previous analysis of one surgeon’s experience with staged reconstruction at this institution suggested that some HLHS subgroups are at higher risk for mortality and attrition.11 Norwood and others have been unable to identify high-risk subgroups.3 12 To address this apparent discrepancy and to identify any additional patient- or procedure-specific risk factors related to first-stage palliation of HLHS, we reviewed all patients who underwent stage I palliation for HLHS at Boston Children’s Hospital between January 1983 and June 1993. Specifically, we examined stage I mortality, survival to second-stage palliation, and actuarial survival among patients who survived stage I palliation.
A total of 212 patients underwent stage I palliation for HLHS at Children’s Hospital, Boston, between January 1983 and June 1993. Patient data were compiled by review of clinical records, including operative reports, and preoperative imaging studies. The diagnosis of HLHS was based on angiographic or two-dimensional echocardiographic evidence of a diminutive ascending aorta, aortic atresia or stenosis, and a hypoplastic left ventricle. It is not our current practice to perform angiography if preoperative transcatheter interventions are not necessary. Of the 212 patients, 153 (72%) were boys and 59 (28%) were girls. Age at operation ranged from 1 to 38 days, with a median of 4 days. Weight at operation ranged from 1.9 to 5.0 kg, with a median of 3.4 kg.
Operative survival was defined as survival of >30 days and the ability to leave the hospital. Follow-up information was obtained from 111 (97%) of the 114 survivors. Follow-up was obtained directly from the patient’s family or primary cardiologist during a 1-month period ending April 1, 1994. Time to follow-up (or late death) ranged from 0.1 to 9.7 years, with a median of 1.7 years. This constituted a total of 267 patient-years. Intermediate results were evaluated by the incidence of death, survival to second-stage palliation, and actuarial survival estimates. Potential risk factors for early mortality were analyzed in contingency tables with χ2 or Fisher’s exact tests. Multivariate analyses of operative mortality, mortality before stage II palliation, and overall intermediate mortality among stage I survivors were performed using stepwise logistic regression and Cox regression models. The relation of discrete variables to survival among stage I survivors was examined with the log-rank test. Survivorship estimates were made by the Kaplan-Meier method. All analyses used a standard, commercially available software package (SAS Institute, Inc).
Fig 1⇓ shows the distribution of anatomic subtypes in the study population. Of the 212 patients, 88 (41.5%) had MA with AA, 59 (27.8%) had MS with AA, 51 (24.1%) had MS with AS, and 14 (6.6%) had other variants.
Fig 2⇓ displays the distribution of ascending aorta diameters in the study population. The ascending aorta diameters in 116 patients (57%) were between 2 and 4 mm; in 18 patients (8.8%), <2 mm; and in 71 (35%), >4 mm. Ascending aorta diameter tended to be greater in those patients with AS than in those with AA (Fig 3⇓).
The presence of a discrete coarctation of the aorta was noted preoperatively in 103 patients (49%). Pre–stage I right ventricular function was identified as normally preserved in 127 patients (60%), mildly depressed in 40 (19%), moderately depressed in 31 (15%), and severely depressed in 11 (5%). Tricuspid regurgitation was noted to be moderate in 14 patients (7%) and severe in 2 (1%). Forty-six (22%) were noted to have restrictive atrial septal defects.
Various techniques were used in the first-stage reconstructions performed during the study period. All but 2 stage I procedures were performed with cardiopulmonary bypass and hypothermic circulatory arrest. The mean duration of circulatory arrest was 62 minutes (SD, 9.9 minutes). Sixteen patients required a second period of circulatory arrest averaging 24 minutes (SD, 5.9 minutes). Pulmonary arterial to aortic continuity was established in several ways. To facilitate statistical analyses, these were classified as type 1: direct anastomosis of the divided proximal pulmonary artery to the side of the ascending aorta with augmentation of the neoaortic arch with homograft, autologous pericardium, or synthetic gusset (n=105); type 2: anastomosis of the proximal main pulmonary artery to the underside of the aortic arch in an end-to-side fashion directly or with a homograft, synthetic, or autologous pericardium interposition tube graft (n=92); and type 3: other forms of palliative reconstruction (n=15). The types of operation with materials used for neoaortic reconstruction are shown in Table 1⇓. A variety of systemic-to-pulmonary shunts were also used during the study period. One hundred eighteen patients (56%) received 4-mm RMBTSs, 74 (35%) had 3.5-mm RMBTSs, and 11 (5.2%) had central shunts placed. The current reconstruction of choice at our institution is a type 1 procedure with a 3.5-mm RMBTS. An additional technique applied to this population is that of delayed sternal closure. The chest was left open in 72 patients (34%), and 51 underwent delayed sternal closure at a mean of 3.8 days (SD, 2.4 days).
Table 2⇓ summarizes the duration of postoperative intensive care unit and hospital stay. The median intensive care unit stay for operative survivors was 11 days, with a range of 4 to 105 days. The median duration of postoperative mechanical ventilation was 6 days in operative survivors, with a range of 2 to 81 days. The median hospital stay among operative survivors was 33.1 days, with a range of 9 to 341 days. The median hospital stay among all patients was 23.5 days, with a range of 0 to 341 days.
There were 98 operative deaths (46.2%). Fig 4⇓ shows hospital mortality by anatomic subtype. The results of univariate analysis of possible risk factors for stage I hospital mortality are shown in Table 3⇓. Patients with ascending aorta diameter <2 mm were at increased risk for operative mortality (P=.002). These patients were more likely to receive a type 2 stage I procedure. Only 7 of the 19 patients (37%) with ascending aorta diameters <2 mm underwent type 1 operations, whereas 95 of the remaining 186 patients (51%) underwent a type 1 operation.
Patients weighing <3 kg were at higher risk for hospital death (P=.024), whereas patients with an immediately preoperative pH >7.5 were more likely to survive (P=.017). There was a trend toward improved survival in those patients with MS/AS by univariate analysis (P=.06). Preoperative right ventricular or tricuspid valve function, type of stage I procedure, type of systemic-to-pulmonary shunt, operative surgeon, or year of operation did not influence operative mortality (P>.05). Independent risk factors for stage I mortality identified in multivariate analysis were weight <3 kg (P=.015) and lower immediately preoperative pH (P=.0361). MS/AS patients were at dramatically lower risk for stage I death (P=.006).
Survival to stage II palliation was also analyzed as an end point. Table 4⇓ summarizes the findings of univariate analysis. Patients who underwent stage I later in the study period (P<.001) and those with MS/AS (P=.001) were much more likely to survive to stage II surgery. Those who had ascending aorta diameter <2.5 mm (P=.018) and those in whom synthetic tube grafts were used in neoaortic reconstruction (P=.03) were less likely to survive to a second-stage operation. Patients receiving a 3.5-mm RMBTS (P=.025) and those undergoing delayed sternal closure (P=.024) were more likely to survive to a stage II procedure. There was a trend toward increased survival to stage II in patients who underwent a type 1 reconstruction (direct side-to-side anastomosis of main pulmonary artery to ascending aorta with aortic arch augmentation, P=.059). Multivariate analysis also revealed that MS/AS patients were less likely to die (P=.031) and patients with synthetic tube graft neoaortic reconstruction were more likely to die (P=.033) before stage II.
Actuarial survival of all patients by anatomic subtype is shown in Fig 5⇓. Overall 1-year actuarial survival was 59% in MS/AS patients and 33% for all others (P=.001). Actuarial survival among stage I survivors, similarly classified according to anatomic subtype, is shown in Fig 6⇓. Again, MS/AS patients showed increased intermediate survival (P=.001), as did those with ascending aorta diameters >4.5 mm (P=.005). In contrast, patients with either mitral atresia (P=.002) or aortic atresia (P=.001) had lower survival. Patients who underwent a type 1 stage I reconstruction had improved actuarial survival (P=.004) compared with those who underwent other types of stage I reconstruction. Multivariate analysis with the proportional-hazards model showed that aortic atresia was the only independent risk factor for death among operative survivors (P<.001).
Although a number of institutions have dedicated considerable effort toward programs of staged reconstruction for HLHS for more than a decade, controversy over the influence of anatomic subtype on stage I survival persists. A smaller, single-surgeon series from this institution previously suggested the importance of anatomic subtype in outcome after stage I palliation.11 There was a trend for patients with MS/AA to be at higher risk for stage I mortality in that series.11 Norwood and Bove and their colleagues have not observed such an influence in several reports of their respective HLHS experiences.3 4 12 13 In the consecutive 10-year institutional experience of this report, pre–stage I anatomy strongly influenced both operative and intermediate mortality among stage I survivors. Patients with MS/AS, who tended to have larger ascending aorta diameter, had improved operative survival, survival to stage II palliation, and overall intermediate survival. During the early years of the study period, these patients were more likely to undergo a type 1 reconstruction. Patients with particularly diminutive ascending aortas were more likely to undergo a type 2 repair. We have speculated that the dependence of the coronary arteries on retrograde perfusion through an attenuated length of ascending aorta has contributed to the apparently inferior early and intermediate results in these patients. As a result, it is now our practice to perform a type 1 repair in virtually all patients. If a type 2 repair is nevertheless chosen, we commonly divide the ascending aorta and reimplant it end to side above the neoaortic annulus in an effort to improve coronary perfusion.
A lower immediately preoperative pH, perhaps reflecting the inadequacy of resuscitative efforts, was also a predictor of higher stage I mortality. This confirms the observation previously made at this institution11 and suggests a beneficial role for prenatal diagnosis, by which acidosis may be largely avoided.
The intermediate results of the MS/AS patients in this series are comparable to those obtained with transplantation when one takes into account the mortality associated with the pretransplant waiting period. The most prolific HLHS transplant center has reported an overall 5-year actuarial survival of 61%.7 However, the early mortality for the majority of the patients in the study population, with atresia of one or both of the left heart valves, did not decrease significantly during the study period. This finding contrasts sharply with the results of reparative neonatal cardiac surgery at our institution.14 There was, however, an encouraging increase in survival to stage II palliation among all patients later in the study period. Of all stage I survivors in the past 5 years, 85% have undergone a second-stage palliative procedure. The vast majority of these second-stage procedures are a bidirectional cavopulmonary connection. The second-stage bidirectional cavopulmonary connection has improved survival at completion of the Fontan procedure at this institution and is the subject of a subsequent report (unpublished data).
We conclude from these data that HLHS patients with MS/AS may undergo a course of reconstructive palliative surgery with overall results similar to those currently offered by cardiac transplantation.7 Patients with other anatomic subtypes face significant early mortality but are now more likely to survive to subsequent palliative procedures. Given the short supply of organ donors, the most appropriate HLHS patients for transplantation are those with either mitral or aortic valve atresia, particularly those who weigh <3 kg and/or have an ascending aorta diameter of <2 mm. Prospective trials are necessary to confirm such speculation.
Selected Abbreviations and Acronyms
|HLHS||=||hypoplastic left heart syndrome|
|RMBTS||=||right modified Blalock-Taussig shunt|
- Copyright © 1995 by American Heart Association
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