Congenital Heart Defects Flashcards
Congenital
Existing at birth
Fetal Circulation
Placenta → umbilical vein → liver → IVC → R atrium → R ventricle → lungs → L atrium → L ventricle → aorta → body (systemic circulation) → umbilical artery OR Placenta → IVC via ductus venosus R atrium → L atrium via PFO Pulmonary artery → aorta via PDA
Fetal Circulation Characteristics
↑PVR 2° fluid filled lungs & hypoxic environment
↓SVR 2° large surface area & low resistance utero-placental bed
Hgb F P50 = 19mmHg ↑oxygen affinity
Most oxygenated blood from the umbilical vein perfuses the brain & heart by shunting across the liver via the ductus venosus & across the heart via PFO
Fetal pH 7.25-7.35
Circulation Transition AFTER Birth
Umbilical cord clamped ↑SVR
Lungs inflate w/ air ↑PaO2 ↓PVR ↑pulmonary blood flow & return to L atrium
↑L atrium pressure > R atrium → PFO functional closure
What factors contribute to the ductus arteriosus remaining patent in utero?
Hypoxia
Mild acidosis
Placental PGEs
Functional PDA close at birth when these factors are removed
What can cause the newborn to revert back to fetal circulation?
Physiologic stresses
Example: CDH
Obstructive Lesions
Prevent ventricular flow either R or L
↓CO
Coarctation or aortic stenosis
Mixing Lesions
Mixing venous & arterial blood
Single ventricle i.e. hypoplastic L heart syndrome
Cyanotic & dependent on PDA at birth
L → R shunts result in _____
Pulmonary over-circulation
↑R ventricle preload
L ventricle output bypasses the systemic circulation
R → L shunts result in _____
Blood bypasses the pulmonary system
Deoxygenated blood pumped out systemically
↓PaO2 ↓SpO2
Eisenmenger’s Syndrome
Uncorrected VSD L → R shunt
→ pulmonary HTN
Shunt reverse direction across the defect when ↑PVR
R → L shunt
Shunt Calculations
Qp = pulmonary blood flow
Qs = systemic blood flow
Normal 1:1 RV = LV output
Qp/Qs
(SaO2 - SvO2) / (SpvO2 - SpaO2)
Arterial (aorta) O2 saturation - venous (SVC) O2 saturation
Pulmonary vein O2 saturation - pulmonary artery O2 saturation
Qp/Qs Assumptions
- Patient breathing RA & pulmonary venous blood fully saturated
- O2 consumption normal resulting in SvO2 25-30% lower than SaO2
- Patient not severely anemia (normal SVC O2 saturation)
- Complete mixing results in aorta & pulmonary artery O2 saturations being equal
*Most cases the assumptions are valid & allow rapid determination Qp/Qs based on SpO2 alone
Qp/Qs = < 1
R → L shunt
Cyanosis
Qp/Qs = 1-2
Minimal L → R shunt
Asymptomatic
Qp/Qs = 2-3
Moderate L → R shunt
Mild CHF symptoms
Qp/Qs = > 3
Large L → R shunt
Severe CHF symptoms
What is the most common congenital defect in children?
Ventricular septal defect
20%
Pulmonary over-circulation L → R shunt
Restrictive VSD
Small size
Limited pulmonary over-circulation
Unrestrictive VSD
LARGE flow across the septum w/ balance b/w SVR & PVR
Regular serial echocardiograms to monitor
Indications to surgically repair VSD:
Poor feeding
Reduced weight gain
↑incidence respiratory infection
PDA
Patent ductus arteriosus connection b/w aorta & pulmonary artery
Significant diastolic run-off into the pulmonary circulation ↓systemic diastolic BP → compromising distal perfusion (mesenteric, renal, & coronary)
Complete AV Canal
Free communication b/w all four heart chamber
Located where the atrial septum joins the ventricular septum
Involves atria, ventricles, tricuspid, & mitral valves → single large valve
When should the AV canal surgical repair be performed?
< 6mos before pulmonary vascular changes develop
Residual septal defects including AV valve regurgitation, postop pulmonary reactivity, & conduction system damage
How do critical coarctations present?
Circulatory collapse, shock, & acidosis d/t poor distal perfusion
PGEs to reopen the ductus
DUCTAL DEPENDENT
Coarctation S/S
Upper extremity HTN
↓LE pulses
L ventricular hypertrophy
Pulmonary Valve Stenosis
Narrowing ↑R ventricle workload
Symptoms dependent on obstruction severity
Often treated w/ balloon dilation
Aortic Valve Stenosis
Narrowing ↑L ventricle workload
Severe aortic stenosis potential to impair LV development in utero
Balloon dilation
Valve replacements at young ages require multiple revisions over time
Ross Procedure
Diseased aortic root resected & patient pulmonary valve root excised & implanted into the aortic position
Coronary arteries are then re-implanted into the “neo-aortic” root
R ventricle to pulmonary artery connection & valve obtained from cadaveric tissue or conduit (synthetic material)
Valve grows as patient grows
RV → PA connection potentially will require revisions over time, but better long-term solution to the aortic valve
Blalock-Taussig-Thomas Shunt
Diverts systemic blood flow to pulmonary artery
Classic BT Shunt
Subclavian artery divided & directly anastomosed to the ipsilateral pulmonary artery
Allows patient own subclavian artery to grow
↓pulses in ipsilateral arm or non-palpable
Modified BT Shunt
SYNTHETIC shunt b/w subclavian artery & pulmonary artery
Ipsilateral arm reflects true pressures & available as A-line location
Artificial material does not grow w/ the patient
Hypotension → sluggish flow & possible thrombosis CRITICAL
Tetralogy of Fallot
Ventricular septal defect
R ventricular outflow tract obstruction
Overriding aorta
R ventricular hypertrophy 2° pressure overload
Repair usually w/in 6mos
BT shunt palliation - neonates w/ hypercyanotic spells & too small for definitive repair (<5kg)
What is the most common cyanotic cardiac lesion?
TOF 6-11% CHD
Impaired pulmonary blood flow R → L shunt
CXR boot-shaped heart d/t R ventricle hypertrophy
Tet Spell Causes
Acute dynamic ↑pulmonary outflow tract obstruction (spasm) → cyanotic episode d/t R → L shunting
RVOTO + VSD
Crying, feeding, acidosis ↑PVR d/t HPV, catecholamines, surgical stimulation
Tet Spell Treatment
↑SVR ↑afterload
Relax the spasm ↓PVR
Tet Spell
Anesthetic Managment
100% FiO2 Sedation Fluid Hyperventilation β blocker ↓HR Esmolol 0.5mgkg or Propranolol 0.1-0.3mg/kg α agonist ↑afterload/SVR ↓HR Phenylephrine 1-10mcg/kg Knees to chest or squat ↑SVR
Truncus Arteriosus*
Failure truncus arteriosus to divide into the aorta & pulmonary artery VSD present R & L ventricle output into the truncus Complete mixing at ventricle level SpO2 75-80%
Transposition of the Great Arteries*
Aorta & pulmonary are reverse
Aorta arises from R ventricle & pumps de-oxygenated blood to the body
Pulmonary artery arises from L ventricle & pumps oxygenated blood back to the lungs
PATIENT NEEDS MIXING TO SUSTAIN LIFE
ASD, VSD, or PDA
Emergency balloon atrial septostomy under echocardiogram at bedside or fluoroscopy in the cardiac cath lab
Infective (Bacterial) Endocarditis
IE or subacute bacterial endocarditis (SBE)
Infection caused by bacteria that enter the bloodstream & settle in the heart lining, valve, or blood vessel
What patient are at increased risk to develop SBE?
Uncorrected congenital heart defects
How to prevent SBE?
Antibiotic prophylaxis especially in at risk patients (CHD)
Acute bacterial endocarditis is most commonly caused by _____ _____
Staphylococcus aureus
What patients require SBE prophylaxis?
Prosthetic cardiac valves
History infective endocarditis
Unrepaired or incomplete repair cyanotic heart disease (including shunts)
Complete repairs w/ prosthetic during 1st 6mos (d/t prosthetic material re-epithelization)
Cardiac transplant recipients w/ valve disease
SBE Prophylaxis Antibiotics
Intraop:
- Cefazolin 50mg/kg IV
- Ampicillin 50mg/kg IV
(PCN allergy Clindamycin 20mg/kg IV)
Preop Amoxicillin 50mg/kg PO
What dental procedures require SBE prophylaxis?
Gingival tissue manipulation
Periapical teeth region involvement
Oral mucosa perforation
*Patients w/ valvular heart disease, repair w/ prosthetic material, previous infective endocarditis, unrepaired cyanotic CHD, cardiac transplant, valve regurgitation
What is considered more important to prevent VGS infective endocarditis for dental procedures?
VGS = viridins group streptococci
Good oral health maintenance & regular access to dental care»_space;> antibiotic prophylaxis
HLHS
Hypoplastic L heart syndrome
Single ventricle w/ complete mixing pulmonary & systemic circulation
SpO2 75-80%
Ductal dependent
Stage I
Norwood
Connection from systemic → pulmonary circulation
1. Atrial septectomy & common atrium created
2. Reconstruct pulmonary artery to aortic arch
3. PDA ligation
4. Establish pathway for blood flow to lungs w/ shunt
SaO2 75-80%
R ventricle ejects blood into systemic circulation
Blalock-Taussig Shunt
Connection from R subclavian to Pulmonary artery
Sano Shunt
Gore-tex graft from R ventricle → pulmonary artery
Improves coronary perfusion
Stage II
Bi-directional Glenn
Direct anastomosis b/w SVC & pulmonary artery branch
Blood flow to both R & L pulmonary arteries
Requires low PVR
Blood flow = passive
Maintain adequate volume/preload
PaO2 75-85%
IVC venous blood continues to flow into the heart → systemic circulation
Stage III
Fontan Procedure
IVC connected to pulmonary vasculature
- Extra-cardiac
- Lateral tunnel
- Fenestrated
Allows passive blood flow from IVC directly to lungs (bypasses the heart)
Completes pulmonary & systemic circulation separation
PaO2 88-93%
Anesthetic Considerations
BEFORE Stage I
Maintain patent PDA w/ PGEs to allow systemic perfusion Restrict excessive pulmonary blood flow - Allow mild hypercarbia CO2 45-55mmHg - Low oxygen concentrations - PEEP Inotropic support - Dopamine or Epi Minimize myocardial depression Prevent & treat pulmonary HTN crisis
Chronic Fontan Complications
Dysrhythmias ↑atrial pressures on suture lines
Protein losing enteropathy - poorly understood hypoalbuminemia development despite normal renal & hepatic function
Thrombosis - dysrhythmias cause venous stasis or sluggish flow
Pulmonary HTN
Result from high blood flow & ↑PVR/pressure PPHN common in un-repaired CHD Acute ↑pulmonary artery pressure → shunt - Desaturation - Bradycardia - Systemic hypotension
Factors known to ↑PVR
Hypoxemia FiO2 <30% Hypercarbia Acidosis Hypothermia Atelectasis \+pressure PEEP Stress or stimulation Light anesthesia
Factors known to ↓PVR
↑FiO2 100%
Hyperventilation
Inhalational agents ↓SVR
Nitric oxide iNO
Nitric Oxide
Potent smooth muscle vasodilator
Short half-life
Stimulates guanylate cyclase → cyclic-GMP → activates protein kinase G → Ca2+ reuptake ↓calcium impairs MLCK cross-bridge formation → smooth muscle relaxation
Promotes capillary & pulmonary dilation
100ppm & 800ppm
Overdose → methemoglobin & pulmonary toxicity
