16

Arrhythmias in Pregnancy

Dana Senderoff Berger and Lee Brian Padove

Introduction

Palpitations account for 16% of the outpatient medical visits [1] and cardiac arrhythmias seen in 60% of otherwise healthy young adults [2]. Arrhythmias are relatively uncommon in pregnancy as evidenced by the prevalence rate of 166 per 100,000 hospital admissions [5]. Interestingly, palpitations in pregnancy often do not correspond to arrhythmias [4], with only 10% of symptomatic episodes of palpitations due to an arrhythmia [3]. Arrhythmias and palpitations occur more frequently during pregnancy probably due to the hemodynamic, hormonal, and autonomic changes [6]. Pregnancy may precipitate new-onset arrhythmia or can exacerbate preexisting stable arrhythmia. The vast majority of arrhythmias are benign in a structurally normal heart [5]; however, they may be related to an underlying structural cardiac defect, which if diagnosed in a timely manner may decrease the associated mortality and/or morbidity.

Common Causes of Palpitations in Pregnancy

Tachycardia is common in pregnancy given the physiologic changes that occur during a normal pregnancy (see Chapter 3). Bradycardia, on the other hand, is uncommon, occurring only in 1% of pregnant patients presenting with cardiac complaints. Benign ectopic beats are seen in 59% of symptomatic and 50% of asymptomatic pregnant women [3,4], and the most common sustained arrhythmia in pregnancy is supraventricular tachycardia. Arrhythmias may range from more benign ectopic beats to more serious ones such ventricular tachycardia (Table 16.1) [3].

Specific diagnosis can be achieved in one-third of patients with palpitations based solely on a combination of history and physical examination, limited laboratory testing, and an EKG [17]. Should the patient have a concerning history, physical exam, laboratory, or EKG finding, the obstetrician must refer the patient to cardiology for further evaluation (Box 16.1 and Figure 16.1).

Most palpitations in pregnancy are self-limiting and benign; however, there is a higher likelihood of an underlying structural cardiac defect if palpitations are accompanied by dizziness, chest pain, shortness of breath or syncope, history of structural/congenital heart disease, or prior cardiac surgery [3,12,13]. If the patient has a prior history of arrhythmia, there is an increased likelihood of recurrent arrhythmias [14] and therefore the patient should be referred to a cardiologist. A family history of sudden death may also identify a patient at risk for a potentially lethal arrhythmia. Physical exam can also help identify palpitations favoring cardiac referral as listed in Box 16.2. However, it is important to be aware of the limitations of physical exam in pregnancy (Chapter 6). In general, high-risk patients include sustained arrhythmias and those with structural heart disease [15]. Those with very frequent premature ventricular contractions (PVCs) may also be at risk for developing a reversible cardiomyopathy [16].

PVCs and premature atrial contractions (PACs) are common in pregnancy [3,4] and typically run a benign course. The exception may be very frequent PVCs. Rhythm monitoring is indicated to establish the burden of arrhythmia to help guide therapy. PACs are quite common in both symptomatic (59%) and asymptomatic pregnant patients (50%) [3]. However, treatment is only recommended if symptoms are intolerable. Symptoms typically improve or resolve in the postpartum period.

High-burden PVCs (>5%) have an association with maternal cardiac events (but no death) and low birth weight babies [19], while even higher burden (certainly identified in patients with as low as 10% but felt to be more likely >20% [20]) may be associated with PVC mediated cardiomyopathy which is felt to be a reversible.

Atrial Fibrillation

There is an increasing incidence of atrial fibrillation in pregnancy, with recent literature citing it as being the leading cause of hospital admissions among sustained arrhythmias in pregnancy [21]. Risk factors include older age, obstructive sleep apnea, underlying congenital heart disease, and hypertension [21]. Pregnancy-associated atrial fibrillation is also known as lone atrial fibrillation, that is, without a prior history of atrial fibrillation outside of pregnancy and no structural heart disease. These episodes of atrial fibrillation are usually self-limited with low risk of embolic events. There appears to be a high variability in the interventions and care in this group [22]. The general basis of treatment of atrial fibrillation is heart rate/rhythm control, and prevention of stroke.

Atrial fibrillation among pregnant patients with structural heart disease may be a marker of increased risk for maternal mortality as well as intrauterine growth restriction [23], which may be predictable based upon the severity of preexisting disease.

Supraventricular Tachycardia

Supraventricular tachycardia (SVT) is reported as the most common sustained arrhythmia in pregnancy [21,22], i.e., 22/100,000 pregnancy related hospitalizations in the United States.

Wolff-Parkinson-White Syndrome

Wolff-Parkinson-White syndrome is characterized by the presence of an extra electrical pathway that provides a source for reentry (“short circuit”). The overall incidence of Wolff-Parkinson-White is not well delineated in the general population, or in pregnancy. In one study, it made up 2.5% of arrhythmias in pregnancy in patients with maternal cardiac disease [21]. The classic resting ECG has a delta wave.

Reentrant Arrhythmias

The reentrant arrhythmia is usually orthodromic, i.e., narrow QRS complex SVT. Impulse travels from atrium to ventricle and then retrograde through the accessory pathway. Usual agents used to treat SVT can safely be used in pregnancy [8].

On the other hand, if the electrical impulse travels antegrade down the accessory pathway it is called antidromic; this can be potentially life threatening with wide QRS complex and special care has to be taken in the selection of medications used [8].

Supraventricular tachycardia during pregnancy had higher adjusted odds for severe maternal morbidity, cesarean delivery, low birth weight, preterm delivery, and fetal abnormalities. This population-based cohort study found that prophylactic ablation pre-pregnancy, while decreasing incidence of SVT during pregnancy, did not seem to change this risk [24].

Ventricular Tachycardia

Ventricular tachycardia (VT) is rare in pregnancy (16 per 100,000 pregnancy-related admissions) [25] and is usually associated with structural heart disease with a reported 1.4% incidence in those with structural heart disease [26]. Patient history with emphasis on prior arrhythmias and syncope along with family history of arrhythmia and/or sudden death should be reviewed. EKG should be done at rest to assess QT interval and if possible, during arrhythmia to identify source/site of origin. The most common source of idiopathic ventricular tachycardia in this age group is right ventricular outflow tract, which is identified by ECG by left bundle branch block pattern and inferior axis deviation.

Ventricular tachycardia if associated with structural heart disease is associated with both increased maternal mortality and poor fetal outcomes [25]. That being said, new-onset ventricular tachycardia in pregnancy is likely of right ventricular outflow tract origin, possibly associated with borderline low magnesium or potassium levels and seems to improve postpartum [27].

Arrhythmias with Genetic Basis

Brugada Syndrome

Brugada syndrome is a rare autosomal dominant genetically transmitted disorder of sodium/calcium channels with varying phenotypic presentations and pathognomonic EKG findings (right bundle like with coved ST segment elevation) that may be intermittent. Its greatest risk is the risk of sudden death and current definitive treatment in the at-risk group is automatic implantable cardioverter defibrillator (AICD) placement [28]. Syncope during pregnancy does not identify a patient as higher risk [29].

In Brugada syndrome, many medications that an obstetrician, cardiologist, or anesthesiologist might normally use may have dire consequences and should be avoided, such as bupivicaine, procaine, flecainide, ergonovine, and procainamide. Drugs to preferably avoid include amiodarone, verapamil, ketamine, tramadol, and propranolol. A full list and discussion of these medications can be found on line at www.brugadadrug.com [28].

Congenital Long QT Syndrome

Congenital long QT syndrome is associated with a repolarization abnormality with a significant risk of sudden death. Diagnosis is made by a combination of patient history, family history, and EKG findings. Long QT syndrome can be associated with a significant risk of sudden death in the postpartum period [31]. Patients generally have successful pregnancy and delivery; however, there may be increased risk of sudden death reported up to 9 months postpartum which may be attenuated with use of beta-blockers from delivery through the postpartum period [16,30,31]. Serum potassium and magnesium should be checked and optimized to keep on the high end within the normal range. A calm environment is important. Avoidance of QT-prolonging drugs both during the pregnancy and during the peripartum and delivery is important. See below for anesthesia considerations. There have been some recommendations to consider assisted delivery to prevent prolonged second stage or Valsalva, which may potentially increase QTC. An up-to-date list of potentially harmful drugs is available at www.crediblemeds.org. Pharmacy consult should be obtained on admission.

Catecholaminergic Biventricular Tachycardia

Catecholaminergic biventricular tachycardia is a rare genetic disease that has limited data in pregnancy. Many of these patients have AICDs in place and are on beta blockade, the dose of which may need maximization during pregnancy. We have had an experience similar to a report in the literature with a pregnant patient developing worsening tachycardia with subsequent induced cardiomyopathy that improved with the addition of flecainide [32].

Arrhythmogenic Right Ventricular Cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy is another inherited disease with limited data, but with successful pregnancy outcomes and low incidence of maternal arrhythmias (3%–13% of pregnancies). Interventions reported in one series included adjustment of beta-blockers, short term use of diuretics, and flecainide [33,34].

Bradyarrhythmias

Atrioventricular Conduction Heart Block

Successful pregnancy outcomes have been reported in asymptomatic patients with heart block with or without pacemakers. Therefore, in asymptomatic women without structural heart disease, prophylactic temporary pacing is not necessary [35]. Thaman et al. noted heart block may worsen during pregnancy but also reported two patients in whom heart block resolved post-partum [36].

Transient Postpartum Bradycardia

Transient bradycardia has been reported in postpartum period that does not require intervention [37]. Anecdotally, our experience and case reports in the literature demonstrate that most of these patients had preeclampsia or relatively elevated blood pressures.

Management Options in Pregnancy

For the Cardiologist: Obstetrician’s Perspective

The majority of cardiologists are not used to discussions with pregnant patients. Not only is the physiology different [37], but usually the priorities, worries, and concerns of the individuals involved including the future mother, the spouse/loved one, and referring doctors vary considerably from what is generally encountered by a cardiologist. Their concerns include:

1.Fetal morbidity and mortality.

2.Maternal morbidity, days in the hospital, route of delivery, anesthesia, breast feeding, etc. The top priority in the mother’s mind is safety of her future baby and reassurance about various testing, even something as simple as EKGs or echocardiography.

3.There is a lack randomized trials or large studies in the pregnant population. Data are often limited to case series, retrospective studies, and some prospective descriptive research.

4.Counseling should be tailored to the specific needs of the pregnant woman.

In general, if symptom treatment is the goal, the first line of treatment is reassurance. If symptoms are disruptive enough to affect lifestyle and nonpharmacologic interventions fail, every effort should be made to use the lowest dose of medications for the shortest duration that will control symptoms. There is limited evidence of antiarrhythmic drugs in pregnancy, therefore providers must weight risks and benefits and take into consideration the stage of pregnancy, severity of the arrhythmia, and possible teratogenicity. Cardiac drugs in pregnancy are discussed in detail in Chapter 20.

Treatment of Specific Arrhythmias

Management of arrhythmias in pregnancy is based on the results extrapolated from observational studies, and generally similar to that in the nonpregnant state.

Frequent PVCs

High burden of PVCs, that is, 20% or greater, is considered an indication for therapy. Beta-blockers are first-line therapy after shared decision making with the patient [25]. If beta-blockade is not effective, flecainide or sotalol may be considered as the next line therapy. It should be noted that beta-blockers are associated with intrauterine growth restriction [39,40]. In addition, there is risk of neonatal hypoglycemia and bradycardia, i.e., 4.3% with beta-blocker exposure group versus 1.2% no exposure and 1.6% versus 0.5%, respectively. Beta-blocker properties are listed in Table 16.2.

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