Cardiac Anomalies Flashcards
What are five adaptations in the fetal circulation that allow it to work?
Umbilical Vein
Ductus Venosus: shunt between umbilical vein and IVC so blood can bypass the liver
Foramen Ovale: shunt between RA and LA so blood can bypass the lungs
Ductus Arteriosus: shunt between pulmonary artery and aorta so blood can bypass the lungs
Umbilical Artery
Is the pulmonary vascular resistance high or low in the fetal circulation, and why?
High
Alveoli filled with fluid rather than air
Hypoxic pulmonary vasoconstriction
Leads to high pulmonary vascular resistance
Is the pulmonary vascular resistance high or low in the newborn’s circulation, and why?
Low
Breath of air
Pulmonary vessels vasodilate
Reducing pulmonary vascular resistance
What is the origin of the umbilical artery?
Anterior division of the internal iliac artery
Becomes obliterated
What are two mechanisms by which the ductus arteriosus closes?
Smooth muscle in the ductus arteriosus senses the increased oxygen levels in the blood and starts constricting
It also senses the placenta being removed, due to drop in prostaglandins, which is a trigger for closure
What four defects are seen in Tetralogy of Fallot
- Pulmonary stenosis
- Right ventricular hypertrophy
- Ventricular Septal Defect
- Overriding aorta
What is the issue with a patent ductus arteriosus?
Because of the systemic vascular resistance (left sided pressures) being higher than the pulmonary vascular resistance (right sided pressures)
There is a reversal of flow and blood flows from the aorta into the pulmonary artery
Which can cause right sided heart failure
What is the treatment of a Patent Ductus Arteriosus
NSAIDs: inhibit prostaglandins
PDA ligation
Coil occlusion
What is Transposition of the Great Arteries?
Switching
RV drains deoxygenated blood into the Aorta but is still fed by IVC / SVC via RA
LV drains into pulmonary artery but is still fed by pulmonary veins via LA
Two independent closed-off circulations
Survival helped by
- VSD: allows for communication between two circulations
- PDA
However, still mixed blood only rather than fully oxygenated blood going to the systemic organs
With TGA, what medication is recommended for the newborn at birth?
Prostaglandin infusion (continuous), to keep ductus arteriosus open Will allow some mixing of the oxygenated and deoxygenated blood
An irregular heart rate is noted at some point in ______% of all pregnancies.
____% of these are of no clinical significance
1-3%
90%
What are the complications of a sustained bradyarrhythrmia or tachyarrhythmia?
Congestive heart failure
Hydrops
Fetal demise
Neurological morbidity
Regarding irregular ectopic beats
- what % of arrhythmias do they comprise
- what are the secondary to
- more common in the ____ trimester
Regarding irregular ectopic beats
- what % of arrhythmias do they comprise = 85%
- what are the secondary to = atrial extrasystoles
- more common in the THIRD trimester
At what HR is the definition of a fetal tachyarrhythmia
> 180
Usually not clinically significant until > 200bpm
What % of all arrhythmias are tachyarrhythmias?
5-8%
What % of tachyarrhythmias are associated with congenital heart disease?
5%
Where the two most common types of tachyarrhythmias?
- SVT (60-90%)
- HR 220-300
- usually re-entrant tachycardia secondary to an accessory pathway - Atrial flutter (10-30%
- HR 250-500
- slower ventricular rate secondary to variable AV block (2:1 or 3:1 conduction)
What are the two types of Brady arrhythmias?
- Structural (50%)
- congenital heart disease
- atrial isomerism and congenitally corrected TGA - Anti Ro/La antibodies
What is the differential diagnosis of fetal arrhythmia?
Infection - maternal or fetal Hypoxia Fetal anaemia Maternal dugs Maternal thyrotoxicosis Maternal catecholamines
What is the neonatal survival of tachyarrhythmia?
> 90%
With the correct choice of medication with SVT and Flutter
In fetal tachyarrhythmias, what factors are associated with worse prognosis?
Hydrops
Associated abnormalities - CHD
Metabolic derangement
Inappropriate medication choice
Which fetal arrhythmia has the highest morbidity and mortality?
Brady arrhythmias
Particularly with hydrops, which is the most important prognostic factor - it is almost fatal and consideration to non-intervention should be given
Presence of CHD is next most important prognostic factor, with mortality > 80%
What is the management of fetal irregular / ectopic beats?
Confirm normal cardia anatomy
Weekly auscultation or Doppler to rule out conversion to tachyarrhythmia
What are the first and second line treatments for fetal tachyarrhythmia WITHOUT hydrops?
Transplacental therapy
SVT
- Flecainide
- Sotalol and Digoxin
Atrial Flutter
- Sotalol
- Digoxin and Flecainide
What are the first and second line treatments for fetal tachyarrhythmia WITH hydrops?
SVT
1. Flecainide
Atrial flutter
1. Sotalol
2. Amiodarone
Not Flecainide as it does not slow AV conduction time
