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Fortunately, indications for DC cardioversion in pregnancy is rare. A literature search suggests only about 50 cases are reported. I haven’t shocked electively in pregnancy but occasionally have come closer to it. In this current corona lockdown period, we had a call for a potential shock in pregnant mother with fast AF, which was again avoided by the optional  rate control measures.

Let us see, how often DC cardioversion might be necessary during pregnancy and few tips for its safety.

General principles

We know pregnancy can be pro arrhythmogenic. Most arrhythmias are non-sustained VPDs and APDs.They can be ignored if there is no structural heart disease, or at least postponed till delivery.

Drugs remain the mainstay.

The most common sustained arrhythmia in the young reproductive age group is SVT (AVNRT/AVRT) that can be managed with drugs like  Adenosine and beta-blockers. (Flecainide/Sotalol are found to be safe in pregnancy) . Though IV Verapamil is very effective, it has with some concern for fetus, so better avoided. Please, note many of the SVTs can be reverted with simple vagal maneuvres and oral beta-blocker /Verapamil. IV Digoxin has been widely used in RHD population for AF during pregnancy.

Mind you, even Injections Adenosine, Esmolol do have bradycardic potential and need to be given in monitored setting (No surprise, they are called medical cardioversion with the attendant risk) 

The universal antiarrhythmic drug Amiodarone still might come in handy in any refractory arrhythmia (Including AF) though it comes under the list of contraindication.(Safety of amiodarone in pregnancy) 

One important suggestion to make. Magnesium is a wonder antiarrhythmic drug, a membrane stabilizing agent through its indirect Ca + and K + blocking properties can be a powerful antiarrhythmic agent, especially in VT. This has a unique safety profile in pregnancy.We use it in eclampsia liberally  with the same action to suppress brain convulsions. (Cerebral tachycardia). Please consider IV magnesium  prior to considering  shock in VTs with dysfunctional ventricles as in peripartum cardiomyopathies et(Dose  to 2 g in 10mL of D5W over 1 to 2 minutes)

Consider DC shock only if there is hemodynamic instability.

Hemodynamic instability demands DC version. One practical issue is , what defines hemodynamic instability? In pregnancy, the systolic BP is already in lower normal due to systemic vasodilatory state. An HR>150 makes it further fall to around 90mmhg. This tempts us to label it as unstable. In this situation, we have to rely on patients’ symptoms to define hemodynamic instability. Never try to shock a comfortable pregnant women in whatever tachycardia she is in . (Including some VTs especially from outflow, fascicular, etc  ) Try to use drugs and get an expert opinion. to rule out subsets like cardiomyopathy, documented CAD, LV dysfunction.

When to shift to a cardiac facility?

This question crop up often. It is mainly logistic. May be in peripartum cardiomyopathy /Suspected ACS  with VT require special care.

 DC Shock checklist  & Precautions 

  • Biphasic shocks with energy levels 100 joules ( up to 200). Ideal to give single shock, ok to err on high energy  
  • Pads should be well away from the abdomen. 
  • Synchronized with QRS complex (Machine does this) 
  • In an unusual event of VF and cardiac arrest Defibrillation with 300/320 J (Here unsynchronised) 
  • Check the crash cart ready with essential drugs.
  • Keep cardiologist either on-call (Even a junior resident in labor room give immense confidence) 
  • Rule out  LV dysfunction or significant valve disease by echo (CAD can’t be ruled out though) If echo machine is not available ask the radiology or cardiology fellow to use the abdominal USG probe to document good LV contractility and gross EF% estimate.
  • If intramural thrombus is not convincingly excluded and there is AF and valvular heart disease, better to heparinse  and shock to avoid embolic events.
  • Temporary pacemaker support (Some of the cardioverters has transcutaneous pacing to tide over transient bradycardia that might occur post-shock) 
  • CPR readiness ( Extreme precaution !)
  • Fetal heart monitoring and Emergency cesarian readiness. 
  • Finally, most important consent with patient and family.

Is electrical Insulation of baby necessary or is it possible? 

 It’s not required. Fetus inherently tolerates stress better. Even if,  few joules reach the fetal heart inadvertently it may not mean much. What is, to be worried is maternal hypotension or bradycardia post-DC shock.

Impact on the fetus: Evidence?

The impact on fetal blood flow is not significant. This report from Taiwan  reassures there is no adverse effect by measuring umbilical artery flow (Yu-Chi Wang European Journal of Obstetrics & Gynecology and Reproductive Biology 126 (2006) 268–274)

While we consider DC shock during pregnancy is safe for the fetus, still, shock pads close to the abdomen, amniotic fluid being a good conductor of electricity at least one mother showed a sustained contraction of the uterus and fetal distress. This was possibly attributable to DC shock  Eleanor J. Barnes BJOG 2003 https://doi.org/10.1046/j.1471-0528.2002.02113.

Final message 

Most cardiac arrhythmias in pregnancy are carefully managed by non-electrical means. Of course, emergencies can’t afford to wait. Though two lives are at stake, it’s the mother’s heart that prevails over in drug selection and risk estimation. After all, it is her loving heart, that keeps the fetus alive.

I have seen Obstetrician anxiety (which spills over to attending cardiologist too!) can be extreme in such situations. I must admit, Obstetricians, are truly sincere warriors fighting at odd hours to protect the two delicate lives. After all, taking  responsibility brings the anxiety. Cardiologists must understand this and help them out in their difficult times.(without any super specialty ego !)

Reference

  1. Crijns HJ. Electrical cardioversion in healthy pregnant women: safe yes, but needed?. Neth Heart J. 2011;19(3):105‐106. doi:10.1007/s12471-011-0079-3

 

2.Finlay AY, Edmunds V. D.C. cardioversion in pregnancy. Br J Clin Pract. 1979;3:88–94

3.Oktay C, Kesapli M, Altekin E Wide-QRS complex tachycardia during pregnancy: treatment with cardioversion and review. Am J Emerg Med. 2002 Sep;20(5):492-3.

Which drugs are safe?

From BMJ 

Click to access pregnancy_heart_disease_v28_web.pdf

 

Further frontiers 

The DC shock from ICD experience

There have been a good number of women who got ICD for various indications (Commonly HOCM, long QT, ) who subsequently became pregnant, successfully managed during pregnancy.

(One rare study Andrea Natale et ll Circulation. 1997;96:2808–2812 documents at least 10 shock episodes documented in large series of 44 patients without any consequences)

 

 

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Why should mitral  annulus gets calcified ? .  Degenerative  calcification can be benign in  elderly .  If it occurs prematurely (say < 55 years )   there is enough reasons to worry .  This may represent a systemic vascular inflammation and  is considered a surrogate marker for athero- vascular -sclerosis .  A study from Cidar Sinai  , Los angels  has well documented the link way back in 2003  !

mitral annular calcification mac cad link

This is a  large study involving  17 735 patients (who were investigated for symptoms of CAD )   were screened.

The incidence  of MAC was high (As expected !)

  • 35% > 65 years
  • 5 %  < 65 years
Angiography  revealed more surprises .
  • The incidence of angiographic  CAD among those who had MAC and no MAC   was  88% v68% respectively ,( p = 0.0004),
  • Left main coronary artery disease  was (14% 4%, p = 0.009)
  • Triple vessel disease  was (54% v33%, p = 0.002).

mitral annular calcification  www_drsvenkatesan_co_in

Image source  S.Atar ,  Heart 2003 : 89, 161-164

Conclusion
This study concluded ,  CAD is more aggressive in patients with MAC. It can  also be  an independent  predictor of  high risk CAD .
Further Implications  of MAC
  1. MAC is more common in women, especially diabetics .
  2. Degenerative Mitral regurgitation  is common ,rarely  mitral stenosis
  3. Recurrent VPDs and even  trouble some mitral annular VT is possible
  4. Extensive calcific lesions in coronary  artery is also reported with MAC.
Link between Stroke and MAC .
This was well proven by this paper  published in  NEJM in 1992.
MITRAL ANNULAR CALCIFICATION AND STROKE NEJM  EMELIA BENJAMIN 1992

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Acute coronary syndrome is the number one cardiac emergency .In any coronary care unit there are vital differences  between men and women in terms of ACS presentation and outcome . Though there can be variation in ethnic , geographical   factors .The following is   an observation  from one of the Asia’s oldest  and  largest coronary care unit over a period of 40 years . (Madras medical college Chenna ,India )

There is  very significant gender advantage in the incidence of ACS. The male female ratio is consistently around  4: 1 .This Indicates for every day , men suffer from ACS  by four  fold more .This is a very hard data can not be ignored . Women present to the hospital much later than men .This may be due to increased tolerance of pain, social issues  waiting for their spouse to arrive etc

  • There is a  significant  difference in the pattern of ACS in men and women . Men present with STEMI  and women present with more of NSTEMI . In  NSTEMI  the gender ratio is dramatically equal 1 :1 .
  • Explosive chest pains are less common in women .
  • For some unknown reason  diabetes  afflicts  women with a  greater ferocity  !
  • Similarly  it appears  obesity and dyslipidemia has more significance in women
  • Sudden cardiac death and primary VF is many fold less common in women.
  • Mechanical complications like mitral regurgitation and ventricular septal rupture are several fold higher in women (Weak muscle low muscle mass ?)
  • Thrombolytic success is slightly lower in women than men .
  • The overall outcome in ACS is same as men .Some say women fare  worse  .This is important because while they are protected heavily against development of CAD once they develop it  the outcome seems  exempted  from the gender advantage .The reason for this is not clear

Final message

Women show their  unique way   in ACS  too ! Some   of them are  true  advantages  while  few are disadvantages .The mechanism for these differences  can not be entirely attributable to presence or absence of  estrogen . The hard fact is ,  women always score over men in the tolerance levels and  deal effectively stress situations .  It would appear Women’s body   easily nullify adrenergic triggers .

Reference

Reference less cardiology .

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