Fetal Arrhythmia Flashcards
What is the normal fetal heart rhythm rate and variability?
HR : 110-160 bpm Variability: 5-15 bpm (can e decreased by magnesium and betamethasone)
What are the most common causes of fetal arrhythmia?
Premature atrial contractions Premature ventricular contractions Atrial bigeminy (blocked or conducted)
What is the normal process for conduction system in the heart?
SA node -> AV node -> Bundle of His -> Left and Right Bundle branches -> Perkinje Fibers
What percentage of fetal arrhythmia are benign?
90% are benign 10% are life threatening
Describe the steps you take to determine the fetal rhythm in the setting of fetal arrhythmia?
1) Regular or irregular rhythm 2) FHR fast or slow 3) Relationship between atrial and ventricle : 1:1, 2:1 -Measure the atrial rate -Measure the ventricular rate -Assess AV interval (normal - 100-140ms)
How do you assess the relationship between the atrium and ventricle on fetal Doppler?
-Measure the atrial rate -Measure the ventricular rate Do this using the M mode or color m mode doppler or anatomic M mode in the 4CH view, insonation captures the atrial and ventricle- -Assess AV interval (normal - 100-140ms) Do this using pulse wave doppler in the LVOT view, SVC/Ascending Aorta Sagittal view and Left innominate (brachiocephalic vein)/aorta view:
What are examples of irregular fetal rhythm?
-Premature atrial contractions (most common) -Premature ventricular contractions (rare)
What are examples of tachyarrhythmia in a fetus?
-Sinus tachycardia -Supraventricular tachycardia (ectopic atrial tachycardia, permanent junction reciprocating tachycardia) -Ventricular tachycardia -Atrial flutter
What are examples of bradyarrhythmis in a fetus?
-AV block -Sinus Bradycardia -Blocked PACs
What are causes for PAC in a fetus?
Maternal stimulant: cough medications, caffeine, chocolate, cocoa butter Redundant foramen ovale flap (aneurysm of atrial septum) 1% is associated with Ebstein’s anomaly and Cardiac tumors 1% can develop SVT
What are causes for PVC in a fetus?
Very rare (less than 5% of arrhythmia) -Fetal myocarditis -Cardiomyopathy -Long QT syndrome -Cardiac tumors (Rhabdomyomas) Postnatal echocardiogram needed
How do you tell the difference between PAC and PVC?
In PAC, both the atrial and ventricular rhythm are abnormal In PVC on the ventricular beat is abnormal, atrial beat is normal
What causes fetal sinus tachycardia?
-Maternal fever -Infection -Maternal drug ingestion - betamimetics -Fetal distress
How do you define fetal sinus tachycardia?
HR - 180-200 bpm AV conduction - 1:1 Usually detected in the 2nd and third trimesters
How do you define fetal SVT?
HR: 180-280 bpm AV conduction - 1:1 Sustained leads to hydrops
What causes short ventricular atrial conduction in the setting of fetal SVT?
HR: 230-280 bpm -10% WPW -Atrioventricular reentrant tachycardia
What causes long ventricular atrial conduction in the setting of fetal SVT?
HR: 180-220 bpm -sinus tachycardia, permanent junctional reciprocating tachycardia, ectopic atrial tachycardia
Describe fetal atrial flutter?
30% of tachyarrhythmia 300-500bpm 2:1 or 3:1 conduction can lead to nonimmune hydrops
What’s the most common cause of sinus bradycardia?
Sinus bradycardia most commonly caused by vagal stimulation from transducer
What are the causes of bradyarrhythmia?
-Sinus bradycardia -Blocked PAC (bigeminy) (short and long pattern on umbilical artery doppler) -2nd and 3rd degree heart block -Familial idiopathic atrial fibrillation with slow ventricular response
Causes for complete heart block:
Lack of AV synchrony:
- Connective tissue disease with positive SSA/SSB (60% of cases)
- Idiopathic
- Congenital heart disease (left atrial isomerism)
What percentage of fetuses and neonates with heart block have a structural heart disease?
60% - fetus 30 % - neonate
What is the prognosis for complete heart block with structural heart disease?
Only 15% will survive to delivery
When does the myocardium begin to contract?
at 3 weeks post conception
When does the sinus node develop?
at 5 weeks
When does the conduction system develop?
at 16 weeks
What causes a decrease in baseline heart rate with increasing gestational age?
Decrease in fetal heart rate is secondary to increase in parasympathetic nervous system maturation and variability becomes more pronounced as well. 10 weeks - 170 bpm 14 weeks - 150 bpm 20 weeks - 140 bpm Full term - 130 bpm
How often does hydrops develop in fetus with sustained tachyarrhythmia?
50-75%
How often is WPW seen in fetus with tachyarrhythmia (SVT)?
8-10%
What are the modes of treatment for fetal arrhythmia?
-Observation -Transplacental therapy -Direct fetal treatment -Delivery
What are postnatal options for management of fetal arrhythmia?
-Transesophageal pacing -Medications -Cardioversion
How do you prepare for treatment for fetal arrhythmia?
-Consultation with pediatric cardiology and adult cardiology -Maternal 12 lead EKG to assess QT interval -Evaluation of maternal electrolyte - Ca+, K+, Mg+ -Evaluation of maternal renal/hepatic function -Evaluate TSH
List the following regarding digoxin: Dose: Side effect: Therapeutic level: Contraindications:
Dose - Loading dose over 24 hours - 0.5mg every 4-8h IV maintenance dose 0.25mg per day Mechanism of action: increase intracellular calcium and parasympathetic tone Side effect: fatigue, visual changes, GI distress, cardiac arrhythmia Therapeutic level: 0.8-2.0ng/m: Contraindication: maternal WPW, AV block, V fib
List the following regarding flecainide: Dose: Side effect: Therapeutic level: Contraindications:
Dose - 50-100mg q12h, max of 300mg/d Side effect: Dizziness, headache. visual disturbance, paresthesia, flushing Therapeutic level: 0.2-1.0microgram/mL Contraindication: Sick sinus syndrome and a flutter Better for hydrops
List the following regarding Sotalol: Dose: Side effect: Therapeutic level: Contraindications:
Dose - 80mg q12h, max 320mg/d Side effect: fatigue, dizziness, dyspnea, chest pain , prolonged QT Therapeutic level - none Contraindications - AV block or sinus node dysfunction Better for hydrops
What is the goal for K+ and Mag+ when treating a patient with digoxin?
Keep potassium >4 Keep magnesium >2
Describe your follow up after rate control.
-Daily fetal kick counts -Prenatal visits twice times weekly -Follow up with peds cardio every 2 weeks -Maternal EKG, serum K, Mg and drug levels every week
Presence of these features increases the risk for autoimmune congenital heart block?
- FHR less than 55 - Decreased cardiac function - Endocardial fibroelastosis
What is fetal endocardial fibroelastosis?
-Form of restrictive cardiomyopathy -Hyperechoic rim, results from blood stagnating in the heart due to outflow obstruction
Criteria and findings for PAC
PAC on M mode
This is a conducted PAC - note the irregular rhythm and the prolonged duration before the next atrial contraction after the ectopic beat
PAC bigeminy
premature contraction after every normal atrial contraction
PAC trigeminy
Premature contractions after every 2 normal atrial contractions
SVT on M mode
1:1 AV conduction
How often does complete heart block occur in a SSA positive pregnant patient?
1-2%
What is the recurrence rate of complete heart block if there is a prior affected sibling?
14-17%
Complete heart block on M mode:
