Congenital Heart Defects:

Devon M. Fagel, JD

Pediatrics Clerkship, YSM III

Respiratory, Oncology & Research

November 30, 2010

Management of Single Ventricle Physiology

Overview

• Background: Embryology review of heart development

• Definitions: Anatomy of single-ventricle heart anomalies

• Procedures: Interventions to palliate/correct

pathophysiology

• Presentation: Cardiopulmonary management of patient

DN

• Conclusion: The Blalock-Taussig-Thomas collaboration

Embryology:

Everett & Lim, Congenital Heart Disease and Repair. Charlottesville, 2005

• Cardiac Tube: Single tube

twists rightward onto self

and begins pumping by 4w.

Truncus forms aorta & PA,

conus forms atria, bulbus

forms ventricle.

• Septum: A/V septate, form

respective valves. 22q11.2

deletion results in various

types of congenital defects.

• Right to Left Shunts: Fetal

lungs non-functional thus

cavae flow returns to RA

and diverted to LA by PFO.

Flow from PA diverted to

aorta via PDA.

Anatomy:

• Double Outlet Right Ventricle: Normally, PA which carries deoxygenated blood (blue) to lungs arises

from RV and aorta which carries oxygenated blood (red) to body arises from LV. In DORV, PA and

aorta arise from RV carrying mixed blood (purple) to both.

• Ventral Septal Defect: DORV always coincides with VSD which allows blood to pass between RV and

LV. Without VSD, oxygenated (though suboptimal) blood would not reach the aorta. Blood shunted

from left to right heart causing increase flow to lungs, leading to CHF.

• Interrupted Aortic Arch: Type B, interruption between left carotid and left subclavian occurs in 53% of

cases. Must rely on alternate path (PDA) for blood to reach lower body.

• Subaortic Stenosis: Narrowing of area below AV requiring LV to work harder to pump blood.

• Hypoplastic Left Heart Syndrome - Right heart is dominant providing most of systemic circulation.

Everett & Lim, Congenital Heart Disease and Repair. Charlottesville, 2005

Prenatal/Neonatal Interventions:• Echocardiography: HLHS (right heart

dominant providing most of systemic

circulation) detected at 24w leading

to termination.

• Prostaglandin Therapy: Used at birth to

keep shunts patent, systemic circulation

remains viable.

• Presurgical Intervention: Given RV

overload and PHTN, goal to balance

pulmonary and systemic flow so that

pulmonary overcirculation will not

damage the lungs.

• ECMO: Cannulae placed in large vessels,

heparin added and pumped through

membrane oxygenator, removing CO2

and adding O2.

Everett & Lim, Congenital Heart Disease and Repair. Charlottesville, 2005

Palliation/Correction:

• Damus Kaye Stansel Procedure: Norwood procedure, initial palliation attempts to maximize systemic outflow while

balancing pulmonary outflow so as not to damage lungs. Begins with B-T shunt to establish systemic to pulmonary

connection between right brachiocephalic and RPA. Aorta reconstructed by excising distal PA and using homograph to

attach pulmonary trunk to aortic trunk thus isolating pulmonary artery branches from systemic flow.

• Glenn / Hemi-Fontan Procedure: Second procedure to separate right and left heart function to allow pressures and

oxygen levels to normalize. Normally right heart (low pressure) pumps blood to lungs and left heart (high pressure) to

body. Veins carry deoxygenated blood (SaO2 70%) while arteries carry fully oxygenated blood (SaO2 99%). In

congenital heart typical SaO2 levels around 85%. In 1st stage of Fontan, B-T shunt disconnected and PA is excised so

that all blood flow to body provided by dominant ventricle. SVC attached to RPA providing venous flow to lungs. In

second stage IVC is attached to RPA by tunneling through right atrium.

Yuan & Jing, Arch Cardiovasc Dis 102: 549-557, 2009

Norwood Procedure (Stage 1):

Yuan & Jing, Arch Cardiovasc Dis 102: 549-557, 2009

Presentation:• Birth Hx: ex-40wks born to 34 yo G5P3A1LC2 mother with prenatal dx

of CHD. Declined karyotype during pregnancy. APGARs 7/8, initially

required several CPAP breaths but no chest compressions. SpO2 remained

in 80’s pransferred to NBSCU and then NICU

• Hospital Course: 10 m/o f with hx of double outlet right ventricle,

interrupted aortic arch, subaortic stenosis s/p Damus-Kay-Stansel and Glen

procedures. Post-op course complicated by chronic lt pleural effusion, s/p

lt upper lobectomy and plication of lt hemidiaphragm, ECMO, persistent

respiratory failure s/p tracheostomy, urosepsis, mediastinitis, and seizure

d/o due to IJ thrombosis and bilateral subdural hemorrhages.

• Recent Events: Broncoscopy showed diffuse bronchomalacia but patent lt

lower mainstem bronchus, CPAP titrated down from 12 to 5. Developed

Pseudomonas+ tracheitis and decompensated. Due to increased

tachycardia, agitation and WOB, continued on 0.5mg morphine q6, Ativan

0.5mg q4. Also found to have elevated LFTs and GGT. Recent cx show

CMV+.

Cardio/Pulmonary Management:

Photiadis et al., Eur J Cardiothorac Surg 29: 551-556, 2006

• Oxygen Saturation: Mathematical models suggest maximal systemic oxygen delivery occurs with Qp/Qs < 1.

However, optimal hemodynamic status and end-organ function thus higher survival correlate with Qp/Qs

ratio of 1.5. Ventilatory settings should be set to achieve an O2 saturation of 80-85%. This can be achieved

through FiO2.

• Ventricular Function: Digoxin, Lasix and Aldactone to support ventricular function. Check HR, edema and

strictly monitor I/Os.

• Anticoagulation: Given hx of IJ thrombosis and femoral vein occlusion. Check distal pulses, capillary refill

and temperature of extremities.

• Antibiotics: Given subaortic stenosis, pt at risk of bacterial infection. Conduct complete heart exam for

increase in murmur at LUSB.

Mastropietro and Tourner, NeoReviews 10: 239-244, 2009

Bradley et al., J Thorac Cardiovasc Surg 127: 473-480, 2004

Cardio/Pulmonary Imaging:

• Lt Basal Opacities: Lt lower lobe consolidation, lt pleural effusion obscuring

hemidiaphragm, likely atelectasis/fibrosis.

• Cardio/Pulmonary Anatomy: Transverse diameter of heart enlarged, pulmonary

vasculature prominent centrally.

• Foreign Objects: Tracheostomy tube, median sternotomy wires, mediastinal clips

and stents.

ID/Neuro/Dev Management:

• Tracheitis: Cx showed Pseudomonas/MRSA+.

• Transaminitis: Alk Phos 533 (80-380). GGT 369, trending down from 450. Normal US. Hep

panel, EBV, CMV sent showed CMV+. PCR quantification >200.

• Seizure Disorder: Check phenobarbital levels monthly.

• NeuroDevelopment: Given genetic abnormalities, bypass surgery, prolonged hospital stay and

vent/trach dependent, significant delays.

Sarajuuri et. al, Journal of Pediatrics 157: 414-420, 2010

Conclusion:

Blalock & Taussig, JAMA 128: 189-202, 1945

“The operations here reported were undertaken with the conviction that

even though the structure of the heart was grossly abnormal, it might be

possible to alter the course of the circulation in such a manner as to

lessen the cyanosis and resultant disability.”

Murphy & Cameron, JAMA 300: 328-330, 2008

“The Blalock-Taussig article foreshadowed areas of progress in the

treatment of patients with congenital heart disease by providing a

model for cooperation across disciplines (cardiac surgery, pediatric

cardiology and animal research) to make striking medical progress.”

Murphy & Cameron, JAMA 300: 328-330, 2008