Excessive Pulmonary Flow Research Articles

The Role of Shunt Occlusion During Extracorporeal Life Support.

The current recommendation for systemic to pulmonary artery shunt (SPS) patients requiring extracorporeal life support (ECLS) is to keep the shunt open, maintaining a higher pump flow. The practice in our center is to totally occlude the shunt while on ECLS, and we are presenting the outcome of this strategy. This is a retrospective analysis of patients who underwent SPS for cyanotic congenital heart disease with decreased pulmonary blood flow and required postoperative ECLS between January 2016 and December 2020. ECLS indication was excessive pulmonary blood flow, leading to either refractory low cardiac output syndrome (LCOS) or cardiac arrest. All patients had their shunts totally occluded soon after ECLS establishment. Of the 27 SPS patients who needed postoperative ECLS (13 refractory LCOS, 14 extracorporeal cardiopulmonary resuscitation), wherein the strategy of occluding the shunt on ECLS initiation was followed, 16 (59.3 %) survived ECLS weaning and eight (29.6%) survived to discharge. Increased flow to maintain systemic circulation for a SPS patient while on ECLS is an accepted strategy, but it should not be applied universally. A large subset of SPS patients, who require ECLS either due to cardiac arrest or refractory LCOS due to excessive pulmonary flow, might benefit from complete occlusion of the shunt soon after commencement of ECLS, especially in cases with frank pulmonary edema or haemorrhage in the pre-ECLS period. A prospective randomized trial could be ethically justified for the subset of patients receiving ECLS for the indication of excessive pulmonary blood flow.

Early outcome and risk factors analysis of Blalock-Taussig shunt

Objective To investigate the early curative effect of Blalock-Taussig(B-T) shunt and summarize the key point in its post-operative intensive care, analyze the related risk factor of its mortality. Methods We collected 71 patients who received B-T shunt in Shanghai Children′s Medical Center from June 2015 to June 2017.All of 71 cases were divided into neonates group (25 cases) and non-neonate group(46 cases). All patients were operated through median sternotomy, 19 were emergency cases, in which 15 cases were neonates.Eight cases used cardio-pulmonary bypass in our study, in which 4 cases were neonates.Twenty-nine cases received ductus ligation in total 34 patients with patent ductus arterious.Percutaneous heparin was immediately administered after operation as an anticoagulation therapy.Relative large dosage inotropic agents was used after sufficient volume infusion in order to guarantee diastolic pressure higher than 35 mmHg(in neonates >30 mmHg, 1 mmHg=0.133 kPa). Ventilator parameter was adjusted to obtain appropriate flow distribution between pulmonary and systemic circulation.In order to avoid excessive pulmonary flow, the target PO2 was set between 40~45 mmHg. Results Oxygen saturation elevated by 15% after operation in all 71 cases.Average mechanical ventilation time was 92 hours, mean inotropic agents score was 17.There were 6 dead cases, mortality was 8.5%.In neonates, 4 cases dead, mortality was 16.0%.There was no significant difference in ventilation time, ICU retention day and mortality between neonates group and non-neonates group.The logistic regression analysis showed that the body weight and ratio between the shunt conduit diameter and body weight (mm/kg) were the risk factors for early post-operative mortality[body weight: 2 500~3 500 g: OR=6.729, 95%CI=1.373~17.131; ≤2 500 g: OR=7.832, 95%CI=2.563~28.325.the ratio between the shunt conduit diameter and body weight (mm/kg): 1.10~1.15: OR=4.204, 95%CI=1.195~23.926; ≥1.15: OR=3.981, 95%CI=1.195~12.926]. Conclusion B-T shunt is still a high risk operation although it is a palliative method.Low body weight and bigger diameter conduit are the significant factors related to its mortality.Strict control of the systemic and pulmonary flow ratio is the key point in the post-operation intensive care. Key words: Blaclock-Taussig shunts; Neonates; Palliative operation; Congenial heart disease

Functional Improvement and Regression of Medial Hypertrophy in the Remodeled Pulmonary Artery after Correction of Systemic Left-to-Right Shunt.

The presence of systemic left-to-right shunt and increased pulmonary blood flow can result in right heart failure and pulmonary arteriopathy. Correction of left-to-right shunt has been shown to improve cardiac function and physical performance. However, the cardiopulmonary remodeling processes following cessation of left-to-right shunt have yet to be reported. In this experimental study, excessive pulmonary flow was restored through ligation of the aortocaval fistula in rats with flow-induced pulmonary hypertension. The cardiopulmonary morphometric functions were assessed, and phenotypic switching of pulmonary vascular smooth muscle cells (VSMC) was determined. Ligation of aortocaval fistula significantly attenuated pulmonary blood flow and right ventricular mass, and potentiated the isometric contraction of pulmonary artery. Inflammatory cytokines IL-1β and IL-6 were reduced in the lung after ligation. Reduction of pulmonary blood flow restored the expressions of smooth muscle myosin heavy chain and α-smooth muscle actin in pulmonary artery, indicating the switching of VSMCs to the contractile phenotype. Our study demonstrated that normalization of pulmonary blood flow in flow-induced pulmonary hypertension reverses the remodeling in the right ventricle and pulmonary artery. The remodeling process of flow-induced pulmonary hypertension is functionally and morphometrically reversible by inducing transdifferentiation of pulmonary VSMC to contractile phenotypes and modulation of tissue inflammatory cytokines.

Pulmonary Arterial Reconstruction for Pulmonary Coarctation in Early Infancy

Pulmonary atresia with pulmonary coarctation may complicate diminished and unbalanced pulmonary development. The aim of this study is to assess the outcome of pulmonary arterial reconstruction with cardiopulmonary bypass in early infancy for sufficient and balanced pulmonary development. We performed a retrospective review of 15 patients with pulmonary coarctation younger than 4 months of age who underwent pulmonary arterial reconstruction between 2001 and 2005. The mean age and weight were 42.2 days and 3.62 kg, respectively. The patient population included 5 biventricular repair candidates and 10 Fontan candidates. To evaluate the pulmonary arterial development, the preoperative and postoperative pulmonary arterial index and minimum diameter of the pulmonary artery were compared. No early or in-hospital deaths occurred, and there was no nonconfluent pulmonary artery development or segmental mal-development after a mean follow-up period of 14.9 months. Immediate pulmonary flow regulation was required in 2 patients because of excessive pulmonary flow. The mean pulmonary arterial index increased significantly from 103 mm2/m2 to 343 mm2/m2, and the mean minimum diameter of the pulmonary artery increased significantly from 2.02 mm to 4.45 mm. Four biventricular repair candidates completed definitive repair, and 2 required surgical reintervention in the pulmonary artery. Six Fontan candidates completed the Glenn procedure, and 1 completed the Fontan procedure. Three required surgical reintervention in the pulmonary artery. Two late deaths occurred after the Glenn procedure because of ventricular dysfunction and respiratory infection. Pulmonary arterial reconstruction in early infancy provides sufficient and balanced pulmonary arterial development for pulmonary atresia with pulmonary coarctation.

Cardiopulmonary bypass for adults with congenital heart disease: pitfalls for perfusionists

The fixed incidence of congenital heart defects and improved survival have resulted in increasing numbers of adults with congenital heart disease (CHD) who have undergone complex repairs and/or palliations. Eventually, there will be more adults with CHD than children. They will require cardiac surgical interventions associated with progression of their CHD or for age-related disease, such as coronary revascularization. During bypass, anatomical shunts may exist within or without the heart. Left-to-right shunts can result in dramatically lower systemic blood flow than pump flow due to 'steal', while pulmonary edema ensues due to excessive pulmonary flow. Right-to-left shunts carry risks of massive air embolism and double or triple venous cannulation may be necessary. Cannulation of composite reconstructed aortas may be difficult, risking dissection or aortic obstruction, and double arterial cannulation may be indicated. Aberrant coronary arterial and venous anatomy may .preclude adequate myocardial preservation with common techniques and can be complicated by aortic insufficiency. Valves and conduits may exhibit failure. Conventional monitoring, such as central venous oximetry, may be misleading. Monitoring, such as serial lactate measurement, near-infrared spectroscopy and transcranial Doppler blood velocity, offer advantages for such patients. The perfusionist needs to be aware of such conditions as much congenital aberrancy may present unexpectedly during cardiac surgery.

Persistent pulmonary hypertension in a neonate with vein of Galen arteriovenous malformation.

Vein of Galen aneurysmal malformation (VGAM) often leads to death in the neonatal period, mainly due to congestive heart failure. Chronic and excessive pulmonary flow in utero and postnatally is attributed to large VGAM and right ventricular overload. We report a male neonate with VGAM complicated by severe heart failure and persistent pulmonary hypertension. Endovascular coil embolization of VGAM was performed, resulting in improvement of congestive heart failure; however, severe persistent pulmonary hypertension led to death 2 days after the embolization. Postmortem examination showed marked right and left ventricular hypertrophy and impressive muscular thickening of intra-alveolar arterioles. Neonatal embolization seems to be beneficial only in babies without suprasystemic pulmonary hypertension. Therefore, early delivery and repair of VGAM should be considered before the onset of persistent pulmonary hypertension.

The infant with single ventricle and excessive pulmonary blood flow: results of a strategy of pulmonary artery division and shunt

Background. The infant with a single ventricle and excessive pulmonary blood flow requires early protection of the pulmonary vascular bed to insure suitability for a subsequent Fontan procedure. The traditional approach, pulmonary artery banding, has had disappointing results. We have pursued an alternate strategy: division of the pulmonary artery, and placement of a systemic-to-pulmonary artery shunt. Potential sites of systemic outflow tract obstruction are simultaneously bypassed, by either a Damus-Kaye-Stansel, or modified Norwood procedure. Methods. From January 1996 to June 2001, 22 infants were treated by this strategy. Patients with hypoplastic left heart syndrome were excluded. Median age was 18 days (range 2 days to 6 months). In addition to pulmonary artery division and shunt, 3 of 22 patients underwent a Damus-Kaye-Stansel procedure, and 13 of 22 patients underwent a modified Norwood procedure. Results. There were no operative deaths, and one late death. Actuarial survival beyond 30 months was 90%. At follow-up catheterization in 22 patients, median transpulmonary gradient was 7 mmHg (range 4 to 18), and median pulmonary vascular resistance 1.9 Wood units (range 0.9 to 3.3). Twenty-one patients have undergone a subsequent bidirectional superior cavopulmonary connection, and 6 a Fontan procedure, with no deaths. No patient developed subaortic stenosis, or aortic arch obstruction. Neoaortic insufficiency was none or trivial in 12 patients, mild in 3, and moderate in 1. Conclusions. In patients with a functional single ventricle and excessive pulmonary flow, a strategy of pulmonary artery division and shunt, along with prophylactic bypass of systemic outflow obstruction, carries low operative and midterm mortality. It provides consistent protection of the pulmonary vascular bed, avoids subaortic stenosis and aortic arch obstruction, minimizes neoaortic insufficiency, and ensures suitability for progression along a Fontan pathway. These results provide a comparison for alternate strategies, including pulmonary artery banding.

Optimal degree of pulmonary artery banding—Adequate circumference ratio to calculated size from normal pulmonary valve dimensions

These findings suggest that PA banding may be suitable in children with congenital heart disease and excessive pulmonary flow, and that best results are obtained when the band circumference is <90% of the standard pulmonary valve-ring circumference, as calculated from an equation derived from normal pulmonary valve dimensions. This guideline applies equally well to small infants weighing <3 kg and to larger patients.

Left ventricular size and function in double inlet left ventricle

Using quantitative cineangiography we studied left ventricular size and function in 15 patients (aged 1 day to 15 years) with double inlet left ventricle. Our purpose was to assess how ventricular volume and performance change with age and palliative surgery in patients with and without restriction to pulmonary flow. Ventricular volumes were calculated using Simpson's rule method; end-diastolic volume was also stated as a percentage of predicted total (combined right and left) ventricular volume. Ejection fraction and systolic pressure to end-systolic volume ratio were calculated as indexes of ventricular function. Our results suggest that ventricular size is inadequate for a septation procedure in patients with restriction to pulmonary flow but increases after shunting operation. In patients without restriction to pulmonary flow, ventricular volume is adequate for a septation procedure during the first months of life, but it tends towards reduction, along with obstruction of the interventricular communication, after pulmonary artery banding. Ejection fraction is slightly lower than in left ventricle of heart with biventricular atrioventricular connexion, but it does not decrease with age, at least during the first 15 years of life. Systolic pressure to end-systolic volume ratio also does not decrease with age, but it is lower in patients with excessive pulmonary flow or atrioventricular valvar regurgitation.