VSDs and ASDs UCSF Congenital Cardiac Anesthesia Tutorials William Ng 2017

VSD nomenclature Sub-pulmonary Membranous or peri- membranous Cono-ventricular Inlet or Canal Muscular (RV perspective)

Subpulmonary VSD Also known as supracristal (crista supraventricularis) or conal VSD Infundibular septum just below the aortic valve Associated with aortic insufficiency due to lack of support for the right coronary cusp of the aortic valve and prolapse of the leaflet

Pulmonary and Aortic Valves relation

Membranous or peri-membranous VSD 80% of all VSDs Membranous defects are located subaortic region of the membranous septum They are located near or under the septal leaflet of the tricuspid valve and communicate with the LV just below the aortic valve Maybe partially closed by a collection of tricuspid valve and membranous septal tissue giving an aneurysmal appearance to the septum

Conoventricular Involve the same area as the peri-membranous but have extension anterior and superior in the septum

VSD with TOF Anterior malalignment of the conal septum causes subpulmonary obstruction and is associated with Tetralogy of Fallot

VSD with IAA or Coarctation Posterior malalignment of the conal septum causes subaortic obstruction and can be associated with coarctation or interrupted aortic arch.

AV canal or Inlet Involve the posterior septum near the AV valves Caused by deficiency of the endocardial cushion component of the interventricular septum

Muscular VSDs Muscular defects can occur in any portion of the muscular septum-apical, mid-muscular, anterior, or posterior They are located in the trabecular septum and may appear small from the RV

Lab Findings with VSDs What changes in the are seen in the atrium and ventricles with a large VSD? What EKG findings are seen? What Chest X-Ray findings are seen?

Initial findings with large VSD LV enlargement - blood shunts left to right during systole (RVSP 30 LVSP 120) more than diastole (RVEDP 5 LVEDP5). During systole - blood from LV flows across the VSD and directly through an open pulmonary valve to the lungs and back to the LA leading to LV enlargement. Progressive LV and then RV enlargement.

ECG findings with VSD Right atrial enlargement (peaked P waves in II) Left atrial enlargement (biphasic P waves in lead V3R) Biventricular hypertrophy

CXR findings with VSD moderate cardiomegaly symmetrically increased pulmonary blood flow hyperinflation left tracheal indentation by the aortic arch

Qp:Qs Qp:Qs = (SaO2 sat - MvO2 sat)/(PvO2 sat - PaO2 sat) Qp:Qs > 2.0 “large” shunt Qp:Qs < 1.25-1.5 “small” shunt Qp:Qs < 1.0 means a net right to left shunt

VSD physiology (1) Size of the defect determines the magnitude of the shunt Small defect results in restrictive shunt and large pressure gradient. Large defect (size of the aortic valve) results in small pressure gradient and the magnitude and direction of the shunt are dependent on the SVR to PVR (akin to SV physiology)

VSD physiology (2) PVR to SVR is normally 1:10-1:20, so usually -> large L to R shunt Can have near normal pulmonary blood flow (newborn to 2 weeks old or longer with high LAP) Large uncorrected VSDs lead to pulmonary volume overload, increased PVR causing R to L shunt (Eisenmenger’s) and VSD can not be closed due to increased RV afterload. Large VSDs (Qp:Qs > 2) are corrected early

Symptoms with large VSD Increased PBF causes LA dilation and venous congestion - increased WoB, FTT, and chest infections Systemic BF is maintained by large volume load on the RV and LV. This limits increases in cardiac output and exercise.

VSD surgical therapy Ventriculotomy is usually avoided: approach can be through the RA and tricuspid valve or aorta a PA Right ventriculotomy or left ventriculotomy (for muscular VSD) maybe necessary Infants may have PA band to avoid left ventriculotomy Muscular VSDs away from the valves may be closed in cath lab

VSD anesthetic considerations Pre CPB Maintain HR, contractility and preload - decreased CO will decrease systemic perfusion despite high PBF Avoid decreases in the PVR:SVR which will require increased cardiac output to maintain systemic perfusion Avoid large increase in PVR:SVR which may result in R to L shunt If R to L shunt exists ventilatory measures to decrease PVR along with maintaining or increasing SVR are important

Post CPB considerations Patients with small VSDs and without PVOD usually do not require inotropic support and the reduced volume load on the RV can lead to hypertension requiring nitroprusside or milrinone Patients with PVOD will be hyper-responsive to pulmonary vasoconstriction. Treatment to reduce PVR and support the RV will be necessary Residual VSDs may prevent separation from CPB VSD patch can cause RVOTO or LVOTO Complete heart block can occur from injury to the AV node or bundle of His

ASD subtypes Primum Secundum Sinus venosus Coronary Sinus

Secundum ASDs Secundum atrial septal defects account for about 80% of ASDs. Produced either by fenestrations in septum primum or deficiency of septum primum so that this tissue does not reach septum secundum

Primum ASD Primum ASD represent deficiencies in the endocardial cushion contribution to the atrial septum Frequently associated with cleft anterior MV leaflet and MR AKA partial AV canal

Superior Sinus Venosus ASD (1) Both superior and inferior defects are posterior to the fossa ovalis Unroofed SVC/RA junction with RUPV/LA junction (anomalous communication)

Superior Sinus Venosus ASD (2) Posterior to the fossa ovalis Right upper pulmonary vein comes in normally and attaches to the LA The common wall that separates the SVC/RA junction from the RUPV/LA junction is unroofed Not a defect in the IAS Blood flow - LA to RUPV orifice across the ASD

Inferior Sinus Venosus ASD Inferior Sinus venosus ASD: Results from the deficiency in the common wall that normally separates the right lower pulmonary vein/LA junction from the RA/IVC junction

Inferior Sinus Venosus ASD May be associated with scimitar syndrome Right upper and lower pulmonary veins drain to the IVC/RA junction APCs to the right lower lobe Right lung hypoplasia

Single Patch technique using pericardium Repair of superior sinus census defects

Warden Procedure (1) Sinus venosus with PAPVR - Warden procedure. Transection of the SVC above the origin of the pulmonary veins. The SVC orifice is directed across the defect to the LA with a pericardial patch. The distal end is anastomosed to the RA appendage

Warden Procedure (2)

Coronary Sinus Defect Associated with persistent LSVC draining into a dilated coronary sinus Coronary sinus shares the back wall of the LA (common) wall Fenestrations (unroofing): connections between the coronary sinus and the LA

ASD L -> R shunt mechanisms LA pressure is higher than RA pressure-blood flows from the LA through the fenestrations into the coronary sinus and empties in the RA Unroofing of the coronary sinus at the entry to the RA allows the orifice of the coronary sinus to form a connection between the right atrium and left atrium

Coronary Sinus ASD

CXR findings with ASD Adolescent patient with large secundum atrial septal defect. AP view: the arrow points to the prominent main pulmonary artery segment. Pulmonary vascular markings are prominent. Lateral view: demonstrates a dilated anterior right ventricle.

ASD: Ventricular changes RV enlargement - unlike VSDs blood flow across an ASD is during diastole. LA pressure is greater than RA pressure so blood flows from LA to RA (since RA pressures are lower secondary to higher RV compliance) leading to volume overload of the RV

Pediatric ECG findings with ASD RAD Incomplete RBBB RV hypertrophy

Adult ECG findings with ASD AF RAD RV hypertrophy

ASD Physiology Small restrictive ASDs allow minimal shunting. Large ASDs result in a near common atrium and shunt is depended on PVR:SVR Increased PBF increases LAP and L to R shunt Unlike VSDs, ASDs may take 30-40 years to develop pulmonary volume overload Large ASDs result in volume overload of the LA, RA, and RV seen on Echocardiogram

Anesthetic considerations Pre-CPB Maintain HR, contractility and preload - decreased CO will decrease systemic perfusion despite high PBF Avoid decreases in the PVR:SVR ratio which will require increased cardiac output to maintain systemic perfusion Avoid large increases in PVR:SVR which may result in R to L shunt If R to L shunt exists, use ventilatory measures to decrease PVR, maintaining or increasing SVR are important

Anesthesia for ASD repair Mask induction Limit fentanyl to 10-15 mcg/kg Dexmedetomidine co-anaesthetic -> extubation in OR Caudal morphine 70 mcg/kg in 5-10 ml of preservative free saline

Post-CPB Usually weaned off CPB easily Primum defects can result in heart block from suture of the patch to crest of the IVS Primum defects may have residual MV regurgitation In patients with pulmonary volume overload the PVR may be reactive: use ventilation strategy to reduce this

References Dr. Mark Wesley’s notes Anesthesia for Cardiac Surgery by Dr. James DiNardo Boston Children’s Hospital Multimedia Library Google images