Effect of volume unloading surgery on coronary flow dynamics in patients with aortic atresia

Impact of Antegrade Pulmonary Blood Flow as Patients Progress Through Single-Ventricle Palliations

BACKGROUND

The impact of antegrade pulmonary blood flow (APBF) during single-ventricle (SV) palliation continues to be debated. We sought to assess its impact on the hemodynamic profile and the short- and long-term outcomes of patients progressing through stages of SV palliation.

METHODS

A retrospective single-center study was conducted of SV patients who underwent surgery between January 2010 and December 2020. Patients with APBF were matched to those with no APBF by a propensity score based on body surface area, sex, and type of systemic ventricle. Analysis was performed using appropriate statistics with a significance level of P = .05.

RESULTS

Sixty-three patients with APBF were matched with 95 patients with no APBF. At the pre-stage 2 catheterization, APBF patients had a larger left pulmonary artery diameter (z score, 0.1 vs -0.8; P < .042). Patients with APBF had shorter cardiopulmonary bypass time (57.0 vs 79.0 minutes), shorter duration of mechanical ventilation (14.1 vs 17.4 hours), and shorter hospital length of stay (5.0 vs 7.0 days) at stage 2 palliation (P < .05). In the multivariable Cox regression analysis, patients with hypoplastic pulmonary arteries (z scores < -2; adjusted hazard ratio, 9.17) and patients with chromosomal abnormalities/genetic syndrome (adjusted hazard ratio, 4.03) were at increased risk for poor outcomes (P < .05). During the follow-up period, there was no significant difference in risk of the composite poor outcome and long-term survival between groups.

CONCLUSIONS

SV patients with APBF had shorter cardiopulmonary bypass time, duration of mechanical ventilation, and hospital length of stay after stage 2 palliation. Patients with hypoplastic pulmonary arteries or chromosomal abnormalities/genetic syndromes had increased risk for poor outcomes. Maintaining APBF has better short-term outcomes, but there are no long-term hemodynamic or survival benefits.

Systemic Ventricular Dysfunction Between Stage One and Stage Two Palliation

Infants with a single ventricle can develop systemic ventricular dysfunction (SVD) after stage 1 operation, but available information is sparse. We reviewed our patients having Norwood, Sano, or hybrid procedures to better understand this problem. We conducted a retrospective, case-controlled cohort study of 267 patients having stage1 operation, examining outcomes between stages 1 and 2 (survival and subsequent cardiac surgeries), predictor variables, and histology of hearts explanted at transplantation. SVD developed in 32 (12%) patients and resolved in 13 (41%); mean age of onset was 3.0 ± 1.63 months; median = 2.79. SVD was not associated with cardiac anatomy, type of stage 1 procedure, weight, coronary abnormality, or atrioventricular valve regurgitation. The mean age of resolution = 12.1 ± 9.6 months; median = 6.3, and resolution may have been more likely with a systemic LV than RV (p = 0.067). Outcomes for the entire SVD group were less favorable than for those without, but patients with resolution of SVD had outcomes at least as good those without SVD. Myocardial histology (n = 4) suggested chronic ischemia. The risk of SVD after stage 1, while low, may be a fundamental feature of this patient population. SVD occurs with either a systemic RV or LV, although patients with a systemic LV may be more likely to have resolution than those with an RV. We identified no predictor variables, but histologic findings suggest chronic ischemia may be involved. Given the low incidence of SVD, multi-center studies will be required to better define predictors of onset and resolution.

Heart failure after the Norwood procedure: An analysis of the Single Ventricle Reconstruction Trial

BACKGROUND

Heart failure results in significant morbidity and mortality in young children with hypoplastic left heart syndrome (HLHS) after the Norwood procedure.

METHODS

We studied subjects enrolled in the prospective Single Ventricle Reconstruction (SVR) Trial who survived to hospital discharge after a Norwood operation and were followed up to age 6 years. The primary outcome was heart failure, defined as heart transplant listing after Norwood hospitalization, death attributable to heart failure, or symptomatic heart failure (New York Heart Association [NYHA] Class IV). Multivariate modeling was undertaken using Cox regression methodology to determine variables associated with heart failure.

RESULTS

Of the 461 subjects discharged home following a Norwood procedure, 66 (14.3%) met the criteria for heart failure. Among these, 15 died from heart failure, 39 were listed for transplant (22 had a transplant, 12 died after listing, and 5 were alive and not yet transplanted), and 12 had NYHA Class IV heart failure but were never listed. The median age at heart failure identification was 1.28 (interquartile range 0.30 to 4.69) years. Factors associated with early heart failure included post-Norwood lower fractional area change, need for extracorporeal membrane oxygenation, non-Hispanic ethnicity, Norwood perfusion type, and total support time (p < 0.05).

CONCLUSIONS

By 6 years of age, heart failure developed in nearly 15% of children after the Norwood procedure. Although transplant listing was common, many patients died from heart failure before receiving a transplant or without being listed. Shunt type did not impact the risk of developing heart failure.

Long term survival of hypoplastic left heart syndrome infants: Meta-analysis comparing outcomes from the modified Blalock-Taussig shunt and the right ventricle to pulmonary artery shunt

BACKGROUND

Stage 1 palliation of hypoplastic left heart syndrome (HLHS) involves the Norwood procedure combined with a modified Blalock-Taussig shunt (mBTS) or right ventricle to pulmonary artery shunt (RVPAS). Short-term survival has been described previously, whereas longer-term outcomes remain a subject of debate. This meta-analysis aimed to describe the short and long-term survival outcomes of these two shunts, and explore factors that might influence survival.

METHODS

Medline, Cochrane Libraries and EMBASE were systematically searched, and 32 studies were included for statistical synthesis, comprising 1348 mBTS and 1258 RVPAS patients.

RESULTS

While early in-hospital survival was superior in the RVPAS group (RR=1.5, p<0.05, 95% CI: 1.21-1.85), this difference was lost from 2years post-stage 1 palliation (RR=0.91, p>0.05, 95% CI: 0.79-1.04), and maintained unchanged up to 6years. This shift in survival was also reflected in inter-stage survival, with superior RVPAS outcomes between stage 1 and 2 (RR=1.62, p<0.05, 95% CI: 1.39-1.88), and equivalent outcomes between stage 2 and 3. Potential contributors to this included a significantly higher rate of pulmonary artery stenosis in the RVPAS group and an increased requirement for shunt re-intervention in this group prior to stage 2.

CONCLUSIONS

Despite early advantages, RVPAS and mBTS for palliation of hypoplastic left heart syndrome produced comparable long-term survival. The RVPAS patients experienced more pulmonary artery stenosis and requirement for shunt re-intervention. The impact of shunt type on quality and survival with a Fontan is yet to be assessed.

Hypoplastic left heart syndrome: from comfort care to long-term survival

The management of hypoplastic left heart syndrome (HLHS) has changed substantially over the past four decades. In the 1970s, children with HLHS could only be provided with supportive care. As a result, most of these unfortunate children died within the neonatal period. The advent of the Norwood procedure in the early 1980s has changed the prognosis for these children, and the majority now undergoing a series of three surgical stages that can support survival beyond the neonatal period and into early adulthood. This review will focus on the Norwood procedure and the other important innovations of the last half century that have improved our outlook toward children born with HLHS.

Impact of initial Norwood shunt type on young hypoplastic left heart syndrome patients listed for heart transplant: A multi-institutional study

BACKGROUND

Pulmonary blood flow during Stage 1 (Norwood) palliation for hypoplastic left heart syndrome (HLHS) is achieved via modified Blalock-Taussig shunt (MBT) or right ventricle to pulmonary artery conduit (RVPA). Controversy exists regarding the differential impact of shunt type on outcome among those who require transplantation early in life. In this study we explored waitlist and post-transplant outcomes within this sub-population stratified by shunt type.

METHODS

Eligible patients were enrolled through the Pediatric Heart Transplant Study (PHTS) database. Patients included those listed for heart transplantation at 1 of 35 participating centers, all of whom were <6 years of age and with a diagnosis of HLHS (and variants) status post Stage 1 palliation with MBT or RVPA. Standard risk factors for death were analyzed using multivariable hazards modeling.

RESULTS

Between 2010 and 2013, 190 patients were identified. Compared with the RVPA group (n = 111), the MBT group (n = 79) was less likely to have undergone a Glenn palliation (41% vs 73%, p < 0.001), were younger at listing (median age 1.3 vs 1.8 years, p = 0.05), had lower median weight (7.9 vs 9.4 kg, p = 0.02), and were more likely to be mechanically ventilated at listing (35% vs 22%, p = 0.04). There were no significant differences in median waitlist time (1.7 vs 2.6 months, p = 0.2) or rate of transplantation (61% vs 60%, p = 1.0). Among waitlisted patients, 3-month survival was less for MBT compared with RVPA patients (74% vs 91%, p = 0.02). Patients who had not yet achieved Glenn palliation before listing had lower waitlist 3-month survival (76% vs 90%, p = 0.02). In MBT infants <1 year old, there was a trend toward improved survival in those with Glenn palliation compared to those without (100% vs 68%, p = 0.08). Early post-transplant mortality rates were similar between the RVPA and MBT groups (p = 0.4) with overall survival 84% at 1 year.

CONCLUSIONS

Among HLHS patients, the need for transplant before Glenn palliation is associated with poorer waitlist survival. Waitlist survival is poorer in the MBT group, with this difference driven by pre-Glenn MBT infants. Post-transplant outcomes were unaffected by shunt type.

External counterpulsation of a systemic-to-pulmonary artery shunt increases coronary blood flow in neonatal piglets

BACKGROUND

Systemic-to-pulmonary artery shunt (SPS) palliation reduces coronary blood flow (CBF), which may precipitate myocardial ischemia postoperatively.

HYPOTHESIS

Counterpulsation (CP) of SPS augments CBF.

METHODS

Seven neonatal piglets (4.3 ± 0.23 kg) underwent sternotomy and ductus ligation. With a 5-mm polytetrafluoroethylene graft, SPS was created from innominate to pulmonary artery. A rigid shell holding a 9.5-mm diameter balloon was placed around the graft for CP. Using electrocardiographic signal, CP was initiated to trigger balloon inflation/deflation during the diastolic/systolic intervals, respectively. Instantaneous proximal and distal pulmonary artery and mid-anterior descending coronary artery flow rates were measured using transit time flow probes. Blood pressure and flow rates were recorded during three states: shunt closed, shunt open, and shunt open with CP.

STATISTICAL COMPARISON

Friedman's test and repeated measures analysis of variance.

RESULTS

Diastolic pressure decreased significantly with the shunt open (39 ± 8.4 to 28 ± 4.5 mm Hg, P = .05), then increased with CP (33 ± 2.3 mm Hg, P = .03). Median ratio of pulmonary to systemic flow (Qp/Qs) was 1.19, 1.9, and 1.53 with shunt closed, open, and open with CP, respectively. With CP, both diastolic coronary flow per minute (P = .018) and average diastolic flow rate per diastolic interval (P = .03) increased as well as total coronary flow per minute (P = .066; 19.6% ± 11.7%, 25.2% ± 17.0%, and 15.4% ± 13.9% change from shunt open, respectively). The percentage increase in average diastolic flow rate per diastolic interval correlated strongly with Qp/Qs (R (2) = .838).

CONCLUSIONS

In this model of SPS, CP increased diastolic blood pressure and CBF while maintaining significant augmentation of pulmonary blood flow (Qp/Qs). Shunt CP may aid in early postoperative management of palliative congenital heart disease.

The Effect of Epinephrine on Coronary Flow in the Setting of a Systemic-to-Pulmonary Artery Shunt

Background:

Indirect clinical evidence suggests that coronary blood flow (CBF) is altered in patients palliated with systemic-to-pulmonary artery shunts (SPSs). The addition of epinephrine may exert additional effects.

Methods:

A total of 11 newborn piglets underwent placement of a 3.5- to 4-mm graft between the innominate artery and the pulmonary artery. Doppler probes measured flow continuously in the aorta (aortic flow [AoF]), pulmonary artery and left coronary artery at baseline (SPS closed), SPS open, and during epinephrine administration (SPS closed and open). Each animal served as its own control. Systolic and diastolic CBF, resistance (coronary vascular resistance index [CVRI]), and myocardial oxygen supply demand ratio were calculated.

Results:

Opening the SPS increased AoF and decreased systolic and diastolic pressure from baseline, with and without the presence of epinephrine. The CBF and CVRI decreased on opening the SPS in the presence of epinephrine. The decrease occurred only in diastole and was proportional to pulmonary-to-systemic flow ratio (Qp/Qs). Epinephrine infusion itself reduced CVRI with SPS closed, but there was little further decrease on opening SPS. Myocardial oxygen supply–demand ratio decreased on opening SPS at baseline and with epinephrine.

Conclusions:

This study suggests that SPS decreases CBF, especially in the presence of a higher Qp/Qs and epinephrine. The mechanism is largely due to the decrease in diastolic pressure and the inability of the coronary arteries to compensate with vasodilation.

Pathophysiology of coronary blood flow in congenital heart disease

OBJECTIVES

The aim was to investigate the effects of volume and pressure overload and increased coronary perfusion pressure on coronary flow (CF) in congenital heart disease (CHD) patients.

BACKGROUND

The effects of CHD on CF are poorly mapped.

METHODS

A total of 65 patients with acyanotic CHD and 49 age-matched healthy controls were examined by transthoracic Doppler echocardiography. Posterior descending artery flow was measured in patients with pulmonary valve stenosis (PS) and atrial septal defects (ASDs) i.e. in lesions with right ventricular pressure or volume overload, and left anterior descending artery flow in patients with coarctation of the aorta (CoA) and ventricular septal defect (VSD), in lesions with left ventricular pressure or volume overload. The CF data in each patient group were expressed as the percent of the median for healthy controls from the same age group.

RESULTS

The CF values were in VSD 172%, ASD 185%, PS 233%, and CoA 773% patients. In CoA patients body surface area (r=0.90, p<0.0001), systolic blood pressure (r=0.72, p<0.0001), diastolic blood pressure (r=0.77, p<0.0001), systolic wall tension (r=-0.77, p=0.004), and signs of inflammation (log CRP, r=-0.75, p=0.007) correlated with CF.

CONCLUSIONS

The increase in CF and velocity was most significant in patients with CoA. In newborns, increased coronary perfusion pressure seems to be the most important factor for increased CF, even if the pressure is not assumed to cause a significant increase in flow over the auto-regulatory range of 70-130mmHg. We also showed that inflammation decreases CF.

Effects of cardiopulmonary bypass surgery on coronary flow in children assessed with transthoracic Doppler echocardiography

Perturbation of coronary blood flow (CF) is an important contributor to myocardium-related complications. The study was primarily designed to assess the impact of cardiopulmonary bypass (CPB) surgery on CF by aid of transthoracic Doppler echocardiography. Changes in CF after off-pump coarctation surgery were also studied. All ultrasounds were performed before and 5 ± 1 days after surgery. Eighteen children underwent CPB surgery of ventricular left-to-right shunts at the mean age of 6 mo, while off-pump surgery (aortic coarctectomy) was undertaken at the mean age of 10 days in 12 children. After CPB surgery, both left anterior descending coronary artery mean diameter and basal CF increased from 1.7 ± 0.3 to 2.1 ± 0.4 mm ( P = 0.001) and 27 ± 10 to 47 ± 15 ml/min ( P = 0.0001), respectively. These two coronary variables decreased after off-pump coarctectomy: left anterior descending coronary artery mean diameter from 1.8 ± 0.1 to 1.7 ± 0.1 mm ( P = 0.06), and CF from 44 ± 12 to 25 ± 8 ml/min ( P = 0.001). The findings are in keeping with the hypothesis that the previously reported impairment of coronary flow reserve after CPB surgery could be due to increase in basal coronary flow after CPB. Off-pump coarctectomy seems to have little impact on CF, as the postsurgical decline in flow in these patients seems to relate to the reduction in cardiac pressure afterload.

Morphologic study of the ascending aorta and aortic arch in hypoplastic left hearts: Surgical implications

OBJECTIVES

The ascending aorta and aortic arch in patients with hypoplasia of the left heart are hypoplastic as a result of diminished blood flow. In this study, the presence and degree of obstruction owing to areas of narrowing or infolding within the diminutive aorta are quantified, and their surgical significance is discussed.

METHODS

Ninety-six specimens with hypoplasia of the left heart were studied and measurements were taken at specified sites to evaluate areas of narrowing. Quantitative assessments of infoldings and their contribution to obstruction of flow are made.

RESULTS

Narrowing of the distal ascending aorta was found in 60 (62.5%) specimens, with a decrease in circumference of the distal ascending aorta (0.72 +/- 1.06 mm) present when compared with its midpoint (P < .05). Tissue infolding at the orifice of the brachiocephalic artery and its junction with the distal ascending aorta was observed in 56 (58.3%) hearts, with major infolding in 29 (30.2%) and minor infolding in 27 (28.5%). Tissue infolding at this site correlated with a smaller ascending aorta (P < .001) but not with narrowing in the distal ascending aorta (P = .53). Ductal coarctations were detected in 77 (81.1%) specimens. Their presence correlated with a smaller diameter of the ascending aorta (P < .05), and their severity correlated with the presence of aortic and mitral valvular atresia (P < .05).

CONCLUSIONS

Important areas of obstruction in the ascending aorta in patients with hypoplasia of the left heart were found, and their pathogenesis is discussed. The findings highlight the importance of incorporating the ascending aorta into the aortic reconstruction at the time of initial palliation for patients with hypoplasia of the left heart.

Effects of single-ventricle physiology with aortopulmonary shunt on regional myocardial blood flow in a piglet model

OBJECTIVES

In single-ventricle physiology with aortopulmonary connection, diastolic hypotension could alter regional myocardial blood flow. Also, afterload increases could impair myocardial blood flow by increased wall tension and relative subendocardial malperfusion. This study explores the effects of acute single-ventricle physiology on regional myocardial blood flow distribution and investigates the consequences of moderate afterload augmentation on myocardial blood flow.

METHODS

Single-ventricle physiology was created in 8 piglets without using bypass, and 8 animals served as a sham control group. Aortopulmonary shunt, echo-guided atrial septostomy, tricuspid valve avulsion, and pulmonary artery occlusion allowed the left ventricle to support systemic and pulmonary circulations. Afterload augmentation was produced by aortic balloon inflation. Physiologic recordings and stable-isotope microsphere determination of myocardial blood flow to the subepicardium and subendocardium were obtained at baseline and during single-ventricle physiology (at 30 minutes, 120 minutes, and afterload increase).

RESULTS

Arterial oxygen content, diastolic pressure, and coronary perfusion pressure declined after creation of single-ventricle physiology (P < .05). Acute single-ventricle physiology resulted in higher myocardial blood flow (P < .05), unchanged subendocardial/subepicardial flow ratio and oxygen delivery, and lower coronary resistance (P < .01) as compared with biventricular physiology. Afterload augmentation increased coronary perfusion pressure, causing a trend for higher myocardial blood flow and oxygen delivery (P = NS), without affecting subendocardial/subepicardial flow distribution. Myocardial oxygen supply/demand balance fell in single-ventricle physiology, remaining unchanged during afterload augmentation.

CONCLUSIONS

Our study demonstrates that, in acute single-ventricle physiology with aortopulmonary shunt, myocardial blood flow is maintained by lower coronary perfusion pressure. Further, single-ventricle physiology results in less favorable myocardial oxygen supply/demand balance, although normal transmural myocardial blood flow distribution is maintained. Avoidance of diastolic runoff (ventricle-pulmonary conduit) could improve coronary reserve. In our study, moderate afterload augmentation did not induce relative subendocardial malperfusion, nor did it worsen oxygen supply/demand balance.

Optimal timing of the second stage of palliation for hypoplastic left heart syndrome facilitated through home monitoring, and the results of early cavopulmonary anastomosis

For children with hypoplastic left heart syndrome, contemporary management over three stages includes a window of high risk for sudden death between the initial stage of palliation, the Norwood operation itself, and the second stage, creation of the bidirectional superior cavopulmonary connection. The risk is highest at a time when patients have been discharged from the hospital to grow and prepare for the second stage,1–4and has persisted despite the remarkable improvements in immediate postoperative and hospital survival after the initial surgery.5,6Potential contributing factors to the increased vulnerability to sudden death between the stages include the limited circulatory reserve inherent in the parallel circulations supported by a functionally univentricular heart, the reliance on a prosthetic shunt which is susceptible to thrombosis, and congenital or acquired anatomical cardiovascular abnormalities such as aortic atresia, residual obstruction in the aortic arch, tricuspid valvar insufficiency, or right ventricular dysfunction.7–12

Right ventricle to pulmonary artery conduit reduces interim mortality after stage 1 Norwood for hypoplastic left heart syndrome

BACKGROUND

Despite significant improvement in survival after stage 1 Norwood, interim mortality before the second-stage operation remains significant. On the basis of reports of improved circulatory stability associated with the use of a right ventricle to pulmonary artery conduit, the difference between two physiologically different sources of pulmonary blood flow on interim mortality was investigated.

METHODS

Data collection of 96 consecutive hospital survivors after stage 1 Norwood surgery was undertaken. The source of pulmonary blood flow was a modified right Blalock-Taussig shunt in 46 (BTS) and a right ventricle to pulmonary artery conduit in 50 patients. The same follow-up protocol was used in both groups. Data analysis was performed to identify variables associated with interim mortality.

RESULTS

Analysis of patient-related and procedure-related variables revealed no differences in age, weight, diagnosis, presence of aortic atresia, lowest perioperative pH, duration of cardiopulmonary bypass, circulatory arrest, length of mechanical ventilation, or hospital stay at the time of stage 1 Norwood between groups. Respiratory rate and systolic blood pressure were the only differences detected between groups at the time of discharge. Interim mortality was higher in the Blalock-Taussig shunt group. Statistical analysis identified aortic atresia, a modified Blalock-Taussig shunt, and the presence of perioperative dysrhythmias to be associated with interim mortality.

CONCLUSIONS

The use of a right ventricle to pulmonary artery shunt decreases the incidence of interim mortality among hospital survivors after stage 1 Norwood for hypoplastic left heart syndrome. Aortic atresia, the use of a modified Blalock-Taussig shunt, and perioperative dysrhythmias are independently associated with a higher mortality before superior cavopulmonary connection.

Multiscale modeling of the cardiovascular system: application to the study of pulmonary and coronary perfusions in the univentricular circulation

The objective of this study is to compare the coronary and pulmonary blood flow dynamics resulting from two configurations of systemic-to-pulmonary artery shunts currently utilized during the Norwood procedure: the central (CS) and modified Blalock Taussig (MBTS) shunts. A lumped parameter model of the neonatal cardiovascular circulation and detailed 3-D models of the shunt based on the finite volume method were constructed. Shunt sizes of 3, 3.5 and 4 mm were considered. A multiscale approach was adopted to prescribe appropriate and realistic boundary conditions for the 3-D models of the Norwood circulation. Results showed that the average shunt flow rate is higher for the CS option than for the MBTS and that pulmonary flow increases with shunt size for both options. Cardiac output is higher for the CS option for all shunt sizes. Flow distribution between the left and the right pulmonary arteries is not completely balanced, although for the CS option the discrepancy is low (50-51% of the pulmonary flow to the right lung) while for the MBTS it is more pronounced with larger shunt sizes (51-54% to the left lung). The CS option favors perfusion to the right lung while the MBTS favors the left. In the CS option, a smaller percentage of aortic flow is distributed to the coronary circulation, while that percentage rises for the MBTS. These findings may have important implications for coronary blood flow and ventricular function.

Early cavopulmonary anastomosis in very young infants after the Norwood procedure: impact on oxygenation, resource utilization, and mortality

BACKGROUND

The optimal timing of second-stage palliation after Norwood operations remains undefined. Advantages of early cavopulmonary anastomosis are early elimination of volume load and shortening the high-risk interstage period. Potential disadvantages include severe cyanosis, prolonged pleural drainage and hospitalization, and excess mortality. We reviewed our recent experience to evaluate the safety of early cavopulmonary anastomosis.

METHODS

Eighty-five consecutive patients undergoing post-Norwood operation cavopulmonary anastomosis were divided into group I (cavopulmonary anastomosis at <4 months; n = 33) and group II (cavopulmonary anastomosis at >4 months; n = 52). Groups were compared for age; size; early and late mortality; preoperative, initial postoperative, and discharge oxygen saturation; and duration of mechanical ventilation, intensive care unit stay, pleural drainage, and hospitalization.

RESULTS

Group I patients were younger than group II patients (94 +/- 21 days vs 165 +/- 44 days, respectively; P <.001) and smaller (4.8 +/- 0.8 kg vs 5.8 +/- 0.9 kg; P <.001). The preoperative oxygen saturation was not different (group I, 75% +/- 10%; group II, 78% +/- 8%; P =.142). The oxygen saturation was lower immediately after surgery in group I compared with group II (75% +/- 7% vs 81% +/- 7%, respectively; P <.001) but not by discharge (group I, 79% +/- 4%; group II, 80% +/- 4%). Younger patients were ventilated longer (62 +/- 86 hours vs 19 +/- 42 hours; P =.001), in the intensive care unit longer (130 +/- 111 hours vs 104 +/- 94 hours; P =.049), hospitalized longer (12.5 +/- 11.5 days vs 10.3 +/- 14.8 days; P =.012), and required longer pleural drainage (106 +/- 45 hours vs 104 +/- 93 hours; P =.046). Hospital survival was 100% in both groups. Actuarial survival to 12 months was 96% +/- 4% for group I and 96% +/- 3% for group II.

CONCLUSIONS

Early cavopulmonary anastomosis after the Norwood operation is safe. Younger patients are more cyanotic initially after surgery and have a longer duration of mechanical ventilation, pleural drainage, intensive care unit stay, and hospitalization.

Acute myocardial infarction as a cause of death in palliated hypoplastic left heart syndrome

A 20 month old child with hypoplastic left heart syndrome died suddenly from a massive myocardial infarction 15 months after a hemi-Fontan operation. This was confirmed at postmortem examination and histological examinations. The sites of surgical reconstruction were all in good condition, there were no gross anatomical coronary abnormalities, and the coronary ostia were unobstructed. On microscopy the internal coronary arteries had notable intimal and medial thickening with narrowing of the lumen, although no thrombotic occlusion was seen. To the authors' knowledge, this is the first published report of arteriosclerosis of the coronary arteries in hypoplastic left heart syndrome. It raises the question as to whether there may be a primary histological abnormality in some children with this condition or whether some mechanism of accelerated arteriosclerosis is at work.

Cavopulmonary assist in the neonate: an alternative strategy for single-ventricle palliation

BACKGROUND

Cavopulmonary blood flow, rather than a systemic arterial source of pulmonary blood flow, stabilizes Norwood physiology. We hypothesized that pump-assisted cavopulmonary diversion would yield stable pulmonary and systemic hemodynamics in the neonate. This was tested in a newborn animal model of total cavopulmonary diversion and univentricular Fontan circulation.

METHODS

Lambs (n = 13; mean weight, 5.6 +/- 1.5 kg; mean age, 6.8 +/- 4.0 days) were anesthetized and mechanically ventilated. Baseline hemodynamic parameters were measured. Total cavopulmonary diversion was performed with bicaval venous-to-main pulmonary artery cannulation. A miniature centrifugal pump was used to assist cavopulmonary flow. Support was titrated to normal physiologic parameters. Hemodynamic data, arterial blood gases, and lactate values were measured for 8 hours. Baseline, 1-hour, and 8-hour time points were compared by using analysis of variance.

RESULTS

All animals remained stable without the use of volume loading, inotropic support, or pulmonary vasodilator therapy. Cardiac index, systemic arterial pressure, left atrial pressure, and lactate values were similar to baseline values 8 hours after surgery. Mean pulmonary arterial pressure and pulmonary vascular resistance were modestly increased 8 hours after surgery. Mean arterial pH, Po(2), and Pco(2) values remained stable throughout the study.

CONCLUSIONS

Cavopulmonary assist is feasible in a neonatal animal model of total cavopulmonary diversion and univentricular Fontan circulation with acceptable pulmonary arterial pressures and without altering regional volume distribution or cardiac output. Pump-assisted cavopulmonary diversion, in combination with Norwood aortic arch reconstruction, could solve several major problems associated with a systemic shunt-dependent univentricular circulation, including hypoxemia, impaired diastolic coronary perfusion, and ventricular volume overload.

Early experience with a modified Norwood procedure using right ventricle to pulmonary artery conduit

BACKGROUND

A recent modification to the Norwood procedure involves the use of a right-ventricle (RV) to pulmonary artery (PA) conduit to provide pulmonary blood flow for patients with hypoplastic left heart syndrome (HLHS). This modification is thought to provide more stable hemodynamics by avoiding the diastolic "run-off" that occurs with a Blalock-Taussig shunt.

METHODS

We reviewed our experience with the first 11 patients undergoing the RV-PA conduit modification of the Norwood operation and compared their outcomes with those of the preceding 22 patients who underwent a conventional Norwood procedure.

RESULTS

Between July 1999 and March 2002, 33 patients with HLHS underwent the Norwood procedure at a median age of 5 days (range 1 to 31 days). Aortic atresia was present in 28 (85%). No significant difference was noted between the RV-PA (n = 11) and conventional Norwood (n = 22) groups with respect to measures of morbidity such as duration of mechanical ventilation or hospital stay. Patients who underwent the conventional Norwood procedure did have significantly lower diastolic blood pressure in the early postoperative period (38.4 +/- 4.4 mm Hg versus 49.5 +/- 4.3 mm Hg, p = 0.001). The operative and 1-year survival rates were 81% and 81%, respectively, for patients with the RV-PA modification, which was not significantly different from those of patients who underwent the conventional procedure, 81% and 73% (p = 1.00 and p = 0.36). Two patients developed a pseudoaneurysm of the RV infundibulum after placement of RV-PA conduit. Four sudden deaths occurred after hospital discharge, all occurring in the conventional Norwood group.

CONCLUSIONS

The RV-PA conduit modification of the Norwood procedure results in excellent early survival. By avoiding low diastolic blood pressure this modification may provide superior perfusion to the coronary vascular bed and potentially reduce the risk of sudden unexpected death.

Right ventricle to pulmonary artery conduit improves outcome after stage I Norwood for hypoplastic left heart syndrome

BACKGROUND

Diastolic run off into the pulmonary circulation and labile coronary perfusion are thought to contribute to morbidity and mortality after the Norwood procedure (NP). We compared outcomes from the use of a RV to PA conduit (RV/PA) or a modified Blalock-Taussig shunt (BTS), physiologically distinct sources of pulmonary blood flow.

METHODS AND RESULTS

Review of 56 consecutive patients who underwent a Norwood procedure with a RV/PA (n=36) or a BTS (n=20) between 2000 and 2002. Median age was 4.5 days (range 1 to 40) and median weight was 3.1 kg (range 1.8 to 4.1). The RV/PA was constructed with a 5-mm conduit. Patients in the BTS group received a 4-mm shunt. Comparisons between RV/PA and BTS groups showed no difference for weight, gestational age, prenatal diagnosis, HLHS variant, associated diagnoses, ascending aortic size, ventricular function, AV valve function, and pulmonary venous obstruction. Operative survival was higher with RV/PA [33/36 (92%) versus 14/20 (70%); P=0.05]. Patients with RV/PA had less need for ventilatory manipulations to balance the Qp/Qs (1/36 v/s 8/20; P=0.001), delayed sternal closure (6/36 v/s 7/20; P=0.001), and extracorporeal support (5/36 v/s 7/20; P=0.036). RV/PA patients had more favorable postoperative hemodynamics: higher diastolic blood pressure without changes in systolic blood pressure at 1, 8, 24, 48 hours after the NP (46.3 v/s 39.5; 47.2 v/s 42.1; 46.1 v/s 37.1; and 47.1 v/s 40.2; all P=0.001).

CONCLUSIONS

RV/PA simplifies postoperative management and improves hospital survival after NP for HLHS.

Single-ventricle physiology

The patient with single-ventricle physiology presents a significant challenge to the intensive care team at all stages of management. An integrated approach that applies a working knowledge of cardiac anatomy, cardiopulmonary physiology, and the basic principles of intensive care is essential to guide management for each individual patient. This management requires cooperative and constructive involvement of surgeons, cardiologists, and intensivists, as well as a nursing and respiratory care team experienced in the management of single-ventricle patients. The outcome of each stage of palliation for single-ventricle lesions should continue to improve as new ideas are developed and as older ideas are subjected to rigorous scientific analyses.

Outcomes after the Norwood operation in neonates with critical aortic stenosis or aortic valve atresia

OBJECTIVE

This study was undertaken to determine the demographic, anatomic, institutional, and surgical risk factors associated with outcomes after the Norwood operation.

METHODS

A total of 710 of 985 neonates with critical aortic stenosis or atresia enrolled in a prospective 29-institution study between 1994 and 2000 underwent the Norwood operation. Admission echocardiograms were independently reviewed for 64% of neonates. Competing risks analyses were constructed for outcomes after Norwood operation and after cavopulmonary shunt. Incremental risk factors for outcome events were sought.

RESULTS

Overall survivals after the Norwood operation were 72%, 60%, and 54% at 1 month, 1 year, and 5 years, respectively. According to competing risks analysis, 97% of neonates reached a subsequent transition state by 18 months after Norwood operation, consisting of death (37%), cavopulmonary shunt (58%), or other state (2%, cardiac transplantation, biventricular repair, or Fontan operation). Risk factors for death occurring before subsequent transition included patient-specific variables (lower birth weight, smaller ascending aorta, older age at Norwood operation), institutional variables (institutions enrolling < or =10 neonates, two institutions enrolling >/=40 neonates), and procedural variables (shunt originating from aorta, longer circulatory arrest time, and management of the ascending aorta). Of neonates undergoing cavopulmonary shunt, 91% had reached a subsequent transition state by 6 years after cavopulmonary shunt, consisting of Fontan operation (79%), death (9%), or cardiac transplantation (3%). Risk factors for death occurring before subsequent transition included younger age at cavopulmonary shunt and need for right atrioventricular valve repair.

CONCLUSIONS

Competing risks analysis defines the prevalence of the various outcomes after Norwood operation and predicts improved outcomes with successful modification of controllable risk factors.

Improved Survival of Patients Undergoing Palliation of Hypoplastic Left Heart Syndrome: Lessons Learned From 115 Consecutive Patients

Background Outcome of stage 1 palliation (S1P) for hypoplastic left heart syndrome (HLHS) has improved coincident with application of treatment strategies including continuous superior vena cava oximetry (SvO 2 ), phenoxybenzamine (POB), strategies to minimize the duration of deep hypothermic circulatory arrest (DHCA) and efforts to ameliorate the inflammatory response to cardiopulmonary bypass (CPB) using aprotinin and modified ultrafiltration.

Methods and Results Analysis of a consecutive series of 115 patients undergoing S1P was done to identify the risk factors for mortality and the impact of new treatment strategies. For the current era, July 1996 to October 2001, hospital survival was 93% (75/81) compared with 53% (18/34) for the time period, January 1992 to June 1996, P <0.001. Survival to stage 2 palliation (S2P) was also significantly improved in the current era, 81% (66/81) versus 44% (15/34), P <0.01. Anti-inflammatory treatment strategies demonstrated improved survival by univariate analysis ( P <0.001). Multivariate analysis identified continuous SvO 2 monitoring as a factor favoring S1P survival ( P =0.02) and use of POB as a factor favoring survival to S2P ( P =0.003). In the current era shorter duration of DHCA was associated with improved survival to S2P ( P =0.02).

Conclusions–Improved survival following S1P can be achieved with strategies that allow for early identification of decreased systemic output and the use of afterload reduction to stabilize systemic vascular resistance and therefore the pulmonary to systemic flow ratio. Strategies to ameliorate the inflammatory response to CPB may decrease the degree and duration of postoperative support. Strategies to minimize duration of DHCA may improve intermediate survival and merit additional studies.

Postoperative hemodynamics after Norwood palliation for hypoplastic left heart syndrome

Hemodynamics after Norwood palliation for hypoplastic left heart syndrome (HLHS) have been incompletely characterized, although emphasis has been placed on the role that an excess pulmonary-to-systemic blood flow ratio (Qp/Qs) may play in causing hemodynamic instability. Studies suggest that maximal oxygen delivery occurs at a Qp/Qs < 1. However, it remains unclear to what extent cardiac output can increase with increasing pulmonary perfusion. One approach is to use the oxygen excess factor omega, an index of systemic oxygen delivery, and compare omega with measured Qp/Qs. We measured Qp/Qs and omega in neonates after Norwood palliation for HLHS, and determined how they were related. In addition, we determined the temporal course of surrogate indexes of systemic perfusion in the early postoperative period. Arteriovenous oxygen saturation difference, blood lactate, and omega were recorded on admission and every 3 to 12 hours for 2 days in 18 consecutive infants with HLHS or variant after Norwood palliation. Three infants required extracorporeal membrane oxygenation (ECMO) 6 to 9 hours after admission. These infants had higher Qp/Qs, blood lactate, arteriovenous oxygen saturation difference, and lower omega than non-ECMO patients. In non-ECMO patients between admission and 6 hours, omega decreased significantly despite no appreciable change in Qp/Qs. We conclude that: (1) Oxygen delivery is significantly decreased at 6 postoperative hours unrelated to Qp/Qs. This modest decline in oxygen delivery is insufficient to compromise tissue oxygenation. (2) Patients requiring ECMO have significant derangements in oxygen delivery.

Unexpected death after reconstructive surgery for hypoplastic left heart syndrome

BACKGROUND

Although operative mortality for reconstructive surgery for hypoplastic left heart syndrome continues to improve, nonoperative mortality, especially in the first year of life, remains relatively high. A number of patients who are thought to be clinically well at hospital discharge die unexpectedly. The goal of the present study was to determine the incidence of and risk factors for unexpected death in patients with hypoplastic left heart syndrome.

METHODS

Retrospectively, we determined the incidence of unexpected death among 536 patients with hypoplastic left heart syndrome who were discharged to home after stage I surgical procedure. To identify potential risk factors, a nested case-control analysis was undertaken.

RESULTS

Unexpected death occurred in 22 of 536 patients (4.1%) discharged to home after stage I surgical procedure. The median age at unexpected death was 79 days (range, 25 to 227 days). Seizures preceded cardiac arrest in 2 patients, and ventricular arrhythmias were documented in 3 additional patients during attempted resuscitation. Autopsy studies were performed in 12 patients and identified residual lesions that may have contributed to death in 2 patients. In multivariate analysis documented perioperative arrhythmia and earlier year of stage I surgical procedure were associated with an increased risk for unexpected death (p = 0.03 and p = 0.04, respectively). There were 4 additional patients who had unexpected death after subsequent cavopulmonary operation at a median age of 1.6 years (range, 0.9 to 3.8 years).

CONCLUSIONS

Unexpected death occurred in more than 4% of patients with hypoplastic left heart syndrome who were discharged to home after stage I surgical procedure and was most common in the first several months of life. Factors that may contribute to unexpected death include residual lesions, arrhythmias, and neurologic events, although in the majority of cases the cause remains largely unknown.

Precoronary stenosis after stage I palliation for hypoplastic left heart syndrome

We report a patient with stenosis of the native ascending aorta after palliation of hypoplastic left heart syndrome and aortic atresia. We describe the approach to diagnosis, temporary support with extracorporeal membrane oxygenation, and successful surgical reintervention. Stenosis of the native ascending aorta is an important, potentially reversible cause of acute, early postoperative ventricular dysfunction.

Survival After Reconstructive Surgery for Hypoplastic Left Heart Syndrome

Background —There are limited data regarding the long-term survival of patients who have undergone reconstructive surgery for hypoplastic left heart syndrome (HLHS). We reviewed the 15-year experience at our institution to examine survival in the context of continued improvements in early operative results.

Methods and Results —Between 1984 and 1999, 840 patients underwent stage I surgery for HLHS. From review of medical records and direct patient contact, survival status was determined. The 1-, 2-, 5-, 10-, and 15-year survival for the entire cohort was 51%, 43%, 40%, 39%, and 39%, respectively. Late death occurred in 14 of the 291 patients discharged to home after the Fontan procedure, although only 1 patient has died beyond 5 years of age. Heart transplantation after stage I reconstruction was performed in 5 patients. Later era of stage I surgery was associated with significantly improved survival ( P <0.001). Three-year survival for patients undergoing stage I reconstruction from 1995 to 1998 was 66% versus 28% for those patients undergoing surgery from 1984 to 1988. Age >14 days at stage I and weight <2.5 kg at stage I were also associated with higher mortality ( P =0.004 and P =0.01, respectively). Other variables, including anatomic subtype, heterotaxia, and age at subsequent staging procedures, were not associated with survival.

Conclusions —Over the 15-year course of this study, early- and intermediate-term survival for patients with HLHS undergoing staged palliation increased significantly. Late death and the need for cardiac transplantation were uncommon.

Right ventricular function in congenital heart disease: pressure and volume overload lesions

The right ventricle is often subject to both pressure and volume overload in congenital heart disease. Evaluating right ventricular function in both the native lesion and after surgery in light of these loading conditions, presents a unique challenge for investigators studying these misshapen hearts. The purpose of this article is to briefly delineate what is generally known about right ventricular function in congenital heart disease and to touch on some noninvasive imaging modalities which have helped shed some light on this matter.