Glen shunt (BDG)

hemi fontan and bidirectional glen (BDG)

1. GLENN SHUNT-A REVIEW

2. GENERAL PRINCIPLES OF SUPERIOR AND TOTAL CAVOPULMONARY CONNECTIONS Goal =separate the systemic and pulmonary circuits, resulting in normal or near normal oxygen saturation . Cavopulmonary connections -divert systemic venous return directly into the pulmonary vascular bed, providing more “effective” pulmonary blood flow and reducing the volume load on the single ventricle . GLENN SHUNT-A REVIEW

3. After these procedures, the single ventricle ejects blood only to the systemic circuit, with pulmonary blood flow derived by “passive flow” into the pulmonary vascular bed at the expense of higher central venous pressure . improve cyanosis and minimize ventricular work elevated PVR in the neonate precludes their use until approximately 3 months of age GLENN SHUNT-A REVIEW

4. The cavopulmonary connections -stage to the modified Fontan 1)BDG 2)Hemi- Fontan . Staging - high incidence of pleural effusions and low-output myocardial failure when taken directly for fontan procedure .. GLENN SHUNT-A REVIEW

5. Single left ventricle physiologies T ricuspid atresia with normally related great arteries Double-inlet left ventricle with normally related great arteries T ransposition of the great arteries with PS Malaligned atrioventricular canal with hypoplastic right ventricle P ulmonary atresia with intact ventricular septum GLENN SHUNT-A REVIEW

6. TRICUSPID ATRESIA GLENN SHUNT-A REVIEW

7. Single right ventricle physiologies HLHS DORVwith mitral atresia Malaligned atrioventricular canal with hypoplastic left ventricle Heterotaxy syndromes GLENN SHUNT-A REVIEW

8. HYPOPLASTIC LEFT HEART SYNDROME GLENN SHUNT-A REVIEW

9. GOALS OF STAGE 1 PALLIATION Unobstructed systemic blood flow Limited PBF Undistorted PA Unobstructed PVreturn Minimal AV valve regurgitation GLENN SHUNT-A REVIEW

10. allows the neonate to survive into infancy not a stable anatomic or physiologic long-term solution . ultimately undergo some variation of the Fontan operation as their final surgical palliation GLENN SHUNT-A REVIEW

11. Selecting Patients with Tricuspid Atresia for the Fontan Procedure: The “Ten Commandments”   1.     Minimum age, 4 years 2.     Sinus rhythm 3.     Normal caval drainage 4.     Right atrium of normal volume   5.     Mean pulmonary artery pressure ≤ 15 mm Hg    6.     Pulmonary arterial resistance < 4 U/m 2    7.     Pulmonary-artery-to-aorta-diameter ratio ≥ 0.75    8.     Normal ventricular functions (ejection fraction > 0.6)   9.     Competent left atrioventricular valve    10.   No impairing effects of previous shunts GLENN SHUNT-A REVIEW

12. Glenn. unidirectional (classic) and bidirectional superior cavopulmonary anastomoses and inferior cavopulmonary anastomosis (inferior vena cava [IVC]-to-PA connection ). Interim palliation with a BDG shunt - standard of care in infancy (4 to 9 months of age). GLENN SHUNT-A REVIEW

13. Timing of shunt decrease in PVR= superior cavopulmonary anastomoses by 3 to 6 months of age . Mahle - early ventricular unloading after neonatal single-ventricle palliation improved aerobic exercise performance in preadolescents with the Fontan palliation. early -opportunity to address distorted pulmonary arteries from previous bands or shunts and to create a better distribution of PA blood flow and growth of the pulmonary vascular bed . GLENN SHUNT-A REVIEW

14. Indications for early shunt procedure C yanosis secondary to inadequate pulmonary blood flow after neonatal palliation CHF from an excessive volume load caused by severe atrioventricular valve regurgitation or by an elevated Q p :Q s . GLENN SHUNT-A REVIEW

15. early - weighed against the risks of elevated SVC pressure and cyanosis . Bradley - younger than 3 months was associated with lower oxygen saturation in the early postoperative period and a risk of PA thrombosis . Some infants with severe ventricular dysfunction or atrioventricular valve regurgitation - not be suitable for further staged palliation and may require heart transplantation GLENN SHUNT-A REVIEW

16. Prerequisites before the procedure Echo cath For anatomic and hemodynamic assessment of the PA Aortic arch Ventricular and AV valve function Caval anatomy-Presence of decompressing veins that may result in cyanosis after superior cavopulmonary anastomosis . GLENN SHUNT-A REVIEW

17. CLASSIC GLENN SHUNT Dr. Glenn anastomosis between the transected distal end of the right pulmonary artery and the side of the SVC, which is ligated distal to the anastomosis. azygous vein is ligated to prevent its decompressing flow from the SVC. GLENN SHUNT-A REVIEW

18. BIDIRECTIONAL GLENN SHUNT GLENN SHUNT-A REVIEW median sternotomy CPB shunt is ligated with a vascular clip or ligature. Preservation of the proper spatial orientation of the SVC relative to the PA is essential azygos vein is ligated but not divided SVC is then divided, and the cardiac end is oversewn . cephalic end is anastomosed end to side to the ipsilateral PA .

19. bi-directional - far less likely to engender Pulmonary vascular obstructive disease compared with systemic-pulmonary shunts minimal Distortion of the pulmonary artery architecture. GLENN SHUNT-A REVIEW

20. Shunt between the Superior Vena Cava and Right Pulmonary Artery — Technic of Anastomosis . Glenn WW. N Engl J Med 1958;259:117-120.

21. Angiogram Taken Two Months after Operation. Glenn WW. N Engl J Med 1958;259:117-120.

22. Arterial Oxygen Studies before and after the Shunt.* Glenn WW. N Engl J Med 1958;259:117-120.

23. Technique Without Cardiopulmonary Bypass BDG Patients with sources of pulmonary blood flow that do not need interruption as part of the cavopulmonary anastomosis ( antegrade flow through a stenotic pulmonary valve or banded PA ) and have no specific intracardiac pathology requiring revision are candidates for cavopulmonary anastomosis without CPB . HLHS -not candidates -pulmonary blood flow is shunt dependent/ may require PA reconstruction and other intracardiac procedures at the time of their superior cavopulmonary anastomosis GLENN SHUNT-A REVIEW

24. HEMI FONTAN PROCEDURE GLENN SHUNT-A REVIEW

25. FONTAN PROCEDURE d’Udekem Y et al. Circulation 2007;116:I-157-I-164 Copyright © American Heart Association, Inc. All rights reserved.

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28. Postoperative Physiology circulation to the lungs is from the upper body systemic venous return . pulmonary blood flow results from upper body blood flow, all SVC return must pass through the lungs to reach the heart in the absence of decompressing venous collaterals. GLENN SHUNT-A REVIEW

29. early age - reduction of the volume work of the single ventricle and a predictable Q p :Q s of a 0.6 to 0.7 . This ratio is higher in young infants because of the relative size of the head and the upper extremities in young infants as opposed to those in older children , but in general, systemic arterial oxygen saturations (SaO 2 ) are 75% to 85%. GLENN SHUNT-A REVIEW

30. immediate reduction in the volume load of the single ventricle by removing the aortopulmonary shunt decreases the work of the single ventricle and may improve long-term AV valve and myocardial function . AV valve regurgitation resulting from physiologic rather than structural abnormalities may decrease as the ventricular geometry normalizes GLENN SHUNT-A REVIEW

31. oxygen is delivered more efficiently to the body because only deoxygenated blood from the SVC rather than admixed blood from the ventricle is presented to the lungs for oxygen uptake . reduction in cardiac output needed to achieve a given tissue O 2 delivery GLENN SHUNT-A REVIEW

32. DIASTOLIC DYSFUNCTION GLENN SHUNT-A REVIEW

33. ventricular filling is not absolutely dependent on pulmonary venous return, because IVC flow is still diverted directly to the single ventricle and maintains preload . acute volume reduction noted after superior cavopulmonary anastomosis is better tolerated than in the case of transitioning a child from a neonatal palliation directly to the Fontan completion without an intervening superior cavopulmonary anastomosis GLENN SHUNT-A REVIEW

34. SaO 2 - lower in very young younger than 3 months patients . as young as 4 weeks have had satisfactory BDG shunt creation patients younger than 3 months -early cyanosis, PA thrombosis, and vascular congestion. delay of the procedure until the child is older than 3 months By age 6 months-mortality risk approaches 0 GLENN SHUNT-A REVIEW

35. Postoperative Issues GLENN SHUNT-A REVIEW

36. Mechanical Ventilation Positive pressure ventilation with increased mean airway pressures adversely affects PVR and ventricular filling Early institution of spontaneous ventilation improves hemodynamics Spontaneous breathing also increases pco 2 , which will promote increased cerebral blood flow and, thereby, increase pulmonary blood flow. GLENN SHUNT-A REVIEW

37. “Physiologic” (3 to 5 cm H 2 O) PEEP-well tolerated, does not significantly affect PVR or CO, and may improve oxygenation by reducing areas of microatelectasis , reestablishing functional residual capacity, and improving ventilation/–perfusion matching. GLENN SHUNT-A REVIEW

38. Elevated Cavopulmonary Pressures minimize the transpulmonary gradient (PA mean pressure – common atrium mean pressure) to allow passive PBFthrough the lungs and back to the single ventricle. elevated transpulmonary gradient - pulmonary venous obstruction, elevated PVR, or pleural effusion, hemothorax , or pneumothorax . Extubating - reduce the common atrial pressure and promote flow through the lungs by creating a greater transthoracic gradient from the extrathoracic space to the intrathoracic space . Diminished cavopulmonary blood flow will reduce systemic SaO 2 GLENN SHUNT-A REVIEW

39. Elevation of PVR from the inflammatory effects of CPB may be minimized with pulmonary vasodilators -nitric oxide at 5 to 20 parts per million in inspired gas . Mild facial edema after superior cavopulmonary anastomosis may persist for up to 72 hours . Majority of pleural effusions - diminish over time with judicious diuretic use and fluid restriction . GLENN SHUNT-A REVIEW

40. aspirin (5 mg/kg/day) - reduce the risk of thrombosis of the superior cavopulmonary circuit GLENN SHUNT-A REVIEW

41. significantly elevated SVC pressure ,upper extremity plethora and edema - obstruction at the cavopulmonary anastomosis, distal PA distortion, or marked elevations in PVR . Significant elevations of pressure in the SVC may limit cerebral blood flow. If the SVC pressure is more than 18 mm Hg- early catheterization GLENN SHUNT-A REVIEW

42. Hypertension and Bradycardia Transient postoperative hypertension and bradycardia -first 24 to 72 hours Hypertension - pain, catecholamine secretion, intracranial hypertension acute elevation of the central venous pressure -reflex similar to that seen in head trauma, such that systemic hypertension is necessary to preserve adequate cerebral perfusion . aggressive lowering of the blood pressure may adversely affect the cerebral perfusion pressure vasodilators =cautiously. GLENN SHUNT-A REVIEW

43. Transient bradycardia =acute reduction of the volume load of the single ventricle, or may be due to injury to the sinus node or its arterial supply. GLENN SHUNT-A REVIEW

44. Low Cardiac Output preexisting ventricular dysfunction or severe atrio -ventricular valve regurgitation - volume-loaded ventricles, which need high filling pressures to generate adequate output, volume reduction and the effects from CPB may significantly reduce cardiac output and oxygen delivery to the tissues. GLENN SHUNT-A REVIEW

45. Cyanosis Excessive hypoxemia (SpO 2 <75%) should be investigated promptly. pulmonary venous desaturation systemic venous desaturation decreased pulmonary blood flow . GLENN SHUNT-A REVIEW

46. Pulmonary venous desaturation Pleural effusion Pneumothorax Hemothorax Chylothorax Pulmonary edema Atelectasis Bacterial pneumonia/viral pneumonitis Arteriovenous malformation GLENN SHUNT-A REVIEW

47. Systemic venous desaturation /Decreased oxygen delivery Anemia Low cardiac output Decreased ventricular function Severe AV valve regurgitation Pericardial tamponade GLENN SHUNT-A REVIEW

48. Increased oxygen consumption Sepsis Venovenous collateral from superior cavopulmonary circuit via the systemic venous circuit to the systemic ventricle Baffle leak GLENN SHUNT-A REVIEW

49. Decreased pulmonary blood flow Pulmonary venous hypertension Restrictive atrial communication Decompressing vein GLENN SHUNT-A REVIEW

50. Decreased pulmonary blood flow - decompressing venovenous collaterals, an undiagnosed contralateral LSVC decompressing venous collaterals – MC IN bilateral superior vena cava , a higher early postoperative transpulmonary gradient, and elevated pressure in the SVC. GLENN SHUNT-A REVIEW

51. A left SVC to coronary sinus- may re-canalize, resulting in significant desaturation after superior cavopulmonary anastomosis. Successful transcatheter coil embolization GLENN SHUNT-A REVIEW

52. PULMONARY AV MALFORMATIONS particularly in patients with heterotaxy syndrome. Diversion of normal hepatic venous flow from the pulmonary circulation regress after incorporation of hepatic venous flow into the lungs . young age polysplenia (interrupted IVC with azygos continuation to the SVC ). GLENN SHUNT-A REVIEW

53. gradual hypoxemia months to years pulsatile second source of pulmonary blood flow may minimize the development malformations diminish or disappear completely after fontan completion theoretic advantages exist to an ivc -pa cavopulmonary anastomosis relative to the formation of pulmonary arteriovenous malformations, the elevation in hepatic venous pressure and the detrimental effects on liver function may be prohibitive GLENN SHUNT-A REVIEW

54. long-term aspirin (a cyclooxygenase inhibitor) = prevented the development of cyanosis by preventing pulmonary AV fistula formation. Transcatheter embolisation when feeding artery greater than 3mm. Surgery- Fistulectomy / Lobectomy GLENN SHUNT-A REVIEW