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MFM Written/Oral Boards > Fetal Arrhythmia > Flashcards

Fetal Arrhythmia Flashcards

1
Q

What is the normal fetal heart rhythm rate and variability?

A

HR : 110-160 bpm Variability: 5-15 bpm (can e decreased by magnesium and betamethasone)

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2
Q

What are the most common causes of fetal arrhythmia?

A

Premature atrial contractions Premature ventricular contractions Atrial bigeminy (blocked or conducted)

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3
Q

What is the normal process for conduction system in the heart?

A

SA node -> AV node -> Bundle of His -> Left and Right Bundle branches -> Perkinje Fibers

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4
Q

What percentage of fetal arrhythmia are benign?

A

90% are benign 10% are life threatening

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5
Q

Describe the steps you take to determine the fetal rhythm in the setting of fetal arrhythmia?

A

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)

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6
Q

How do you assess the relationship between the atrium and ventricle on fetal Doppler?

A

-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:

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7
Q

What are examples of irregular fetal rhythm?

A

-Premature atrial contractions (most common) -Premature ventricular contractions (rare)

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8
Q

What are examples of tachyarrhythmia in a fetus?

A

-Sinus tachycardia -Supraventricular tachycardia (ectopic atrial tachycardia, permanent junction reciprocating tachycardia) -Ventricular tachycardia -Atrial flutter

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9
Q

What are examples of bradyarrhythmis in a fetus?

A

-AV block -Sinus Bradycardia -Blocked PACs

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10
Q

What are causes for PAC in a fetus?

A

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

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11
Q

What are causes for PVC in a fetus?

A

Very rare (less than 5% of arrhythmia) -Fetal myocarditis -Cardiomyopathy -Long QT syndrome -Cardiac tumors (Rhabdomyomas) Postnatal echocardiogram needed

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12
Q

How do you tell the difference between PAC and PVC?

A

In PAC, both the atrial and ventricular rhythm are abnormal In PVC on the ventricular beat is abnormal, atrial beat is normal

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13
Q

What causes fetal sinus tachycardia?

A

-Maternal fever -Infection -Maternal drug ingestion - betamimetics -Fetal distress

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14
Q

How do you define fetal sinus tachycardia?

A

HR - 180-200 bpm AV conduction - 1:1 Usually detected in the 2nd and third trimesters

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15
Q

How do you define fetal SVT?

A

HR: 180-280 bpm AV conduction - 1:1 Sustained leads to hydrops

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16
Q

What causes short ventricular atrial conduction in the setting of fetal SVT?

A

HR: 230-280 bpm -10% WPW -Atrioventricular reentrant tachycardia

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17
Q

What causes long ventricular atrial conduction in the setting of fetal SVT?

A

HR: 180-220 bpm -sinus tachycardia, permanent junctional reciprocating tachycardia, ectopic atrial tachycardia

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18
Q

Describe fetal atrial flutter?

A

30% of tachyarrhythmia 300-500bpm 2:1 or 3:1 conduction can lead to nonimmune hydrops

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19
Q

What’s the most common cause of sinus bradycardia?

A

Sinus bradycardia most commonly caused by vagal stimulation from transducer

20
Q

What are the causes of bradyarrhythmia?

A

-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

21
Q

Causes for complete heart block:

A

Lack of AV synchrony:

  • Connective tissue disease with positive SSA/SSB (60% of cases)
  • Idiopathic
  • Congenital heart disease (left atrial isomerism)
22
Q

What percentage of fetuses and neonates with heart block have a structural heart disease?

A

60% - fetus 30 % - neonate

23
Q

What is the prognosis for complete heart block with structural heart disease?

A

Only 15% will survive to delivery

24
Q

When does the myocardium begin to contract?

A

at 3 weeks post conception

25
Q

When does the sinus node develop?

A

at 5 weeks

26
Q

When does the conduction system develop?

A

at 16 weeks

27
Q

What causes a decrease in baseline heart rate with increasing gestational age?

A

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

28
Q

How often does hydrops develop in fetus with sustained tachyarrhythmia?

A

50-75%

29
Q

How often is WPW seen in fetus with tachyarrhythmia (SVT)?

A

8-10%

30
Q

What are the modes of treatment for fetal arrhythmia?

A

-Observation -Transplacental therapy -Direct fetal treatment -Delivery

31
Q

What are postnatal options for management of fetal arrhythmia?

A

-Transesophageal pacing -Medications -Cardioversion

32
Q

How do you prepare for treatment for fetal arrhythmia?

A

-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

33
Q

List the following regarding digoxin: Dose: Side effect: Therapeutic level: Contraindications:

A

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

34
Q

List the following regarding flecainide: Dose: Side effect: Therapeutic level: Contraindications:

A

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

35
Q

List the following regarding Sotalol: Dose: Side effect: Therapeutic level: Contraindications:

A

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

36
Q

What is the goal for K+ and Mag+ when treating a patient with digoxin?

A

Keep potassium >4 Keep magnesium >2

37
Q

Describe your follow up after rate control.

A

-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

38
Q

Presence of these features increases the risk for autoimmune congenital heart block?

A
  • FHR less than 55 - Decreased cardiac function - Endocardial fibroelastosis
39
Q

What is fetal endocardial fibroelastosis?

A

-Form of restrictive cardiomyopathy -Hyperechoic rim, results from blood stagnating in the heart due to outflow obstruction

40
Q

Criteria and findings for PAC

A
41
Q

PAC on M mode

A

This is a conducted PAC - note the irregular rhythm and the prolonged duration before the next atrial contraction after the ectopic beat

42
Q

PAC bigeminy

A

premature contraction after every normal atrial contraction

43
Q

PAC trigeminy

A

Premature contractions after every 2 normal atrial contractions

44
Q

SVT on M mode

A

1:1 AV conduction

45
Q

How often does complete heart block occur in a SSA positive pregnant patient?

A

1-2%

46
Q

What is the recurrence rate of complete heart block if there is a prior affected sibling?

A

14-17%

47
Q

Complete heart block on M mode:

A

MFM Written/Oral Boards (127 decks)

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