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
