An Overview of Arrhythmias in Pregnancy

Benign Arrhythmias

Pregnancy is a common (about 8%) inciting event for inappropriate sinus tachycardia with no impact on maternal or fetal outcomes.⁷ Premature atrial contractions (PACs) are common in pregnancy.⁸ Patients with intolerable symptoms from PACs are typically given beta-blockers, chiefly metoprolol, labetalol, and propranolol.^9,10

Atrial Tachycardia

Non-atrial fibrillation (AF) supraventricular tachycardias (SVT) are reported in 22 to 33 per 100,000 pregnancies.^11,12 Approximately 20% of patients with prior SVT have exacerbations during pregnancy.¹³ Although relatively rare in pregnancy, initiating and maintaining atrial tachycardias may be seen.¹⁴

Paroxysmal Supraventricular Tachycardia (PSVT)

The most common SVT in pregnancy is atrioventricular nodal re-entrant tachycardia.⁸ Arrhythmias are also more likely in patients with pre-excitation.¹⁵ Beta-blockers, mainly metoprolol, labetalol, propranolol, and/or digoxin, are the first line for chronic prophylaxis of symptomatic, stable SVT without pre-excitation; verapamil is the second line.^9,10 In patients with Wolff-Parkinson-White syndrome with symptomatic or frequent SVT, oral flecainide or propafenone is reasonable to prevent further SVT.¹⁰

In acute-onset SVT, vagal maneuvers are the first-line nonpharmacological treatment. Intravenous adenosine is the first-line pharmacological treatment but may be linked with pre-term labor in the third trimester.¹⁶ Intravenous beta-blockers (metoprolol, propranolol) are second-line and may be preferred during the third trimester. Atenolol should be avoided due to its association with fetal intrauterine growth restriction.¹⁷ In refractory cases, non-dihydropyridine calcium channel blockers can be used despite concerns for hypotension, fetal bradycardia, and heart block with verapamil.^18,19 In limited data, intravenous procainamide has been used safely in pregnancy.^9,20 In hemodynamically unstable patients, synchronized electric cardioversion with energy dosing similar to a nonpregnant patient is recommended and safe.¹⁰

Amiodarone is a class D medication with risks for thyroid disorders, bradycardia, and fetal growth restriction. It is reserved for life-threatening circumstances.^18,19

Atrial Fibrillation and Atrial Flutter in Pregnancy

Since 2001, atrial fibrillation (AF) has surpassed paroxysmal supraventricular tachycardia (PSVT) as the most frequent arrhythmia seen in pregnant women.¹² A Registry of Pregnancy and Cardiac Disease (ROPAC) from 2008 to 2011 of 1,321 pregnant women with congenital, ischemic, and valvular heart disease showed a 1.3% incidence of AF or atrial flutter (AFL), with AF occurring mainly in the second trimester. Women with mitral valve disease have a higher incidence. More importantly, compared to women without AF/AFL, maternal mortality was higher in women with AF/AFL (11.8% vs. 0.9%; P < .01) and low birth weight (< 2,500 g) (35% vs. 14%; P < .02).²¹

In a study of 301,638 pregnant women, the incidence of AF among women with versus without known heart disease was 2.2% versus 0.3%. The incidence of recurrent AF in pregnancy was 39.2% in women with preexisting AF. Among pregnant women with AF, pre-eclampsia and heart failure occurred at a rate of 4.1% and 9.6%, respectively. AF is associated with fetal complications, including premature birth, small for gestational age, intraventricular hemorrhage respiratory distress syndrome, and death.²²

Pregnant women with new-onset AF should undergo a transthoracic echocardiogram to assess for structural heart disease or new pathology such as pulmonary embolism. Other causes of AF, such as thyroid disease and electrolyte abnormalities, should be assessed and treated.²³

In patients with hemodynamic compromise with AF, there is a class I recommendation in the 2020 European AF guidelines for immediate direct-current cardioversion,²³ whereas rate control with beta-blockers and digoxin is recommended for hemodynamically stable patients.²⁴ For recurrent or refractory AF, flecainide or sotalol can be used. In general, rhythm control strategies are preferred over heart rate control during pregnancy.²⁵

Since pregnancy carries a nearly a 5-fold increased risk of thromboembolic disease, physicians must consider the risk of thromboembolism in pregnant patients with AF. If a pregnant patient experiences AF, electrical cardioversion should be performed within 48 hours to decrease the risk of stroke. Transesophageal echocardiography may be needed if the duration of AF is uncertain. Heparin is preferred, particularly low-weight-molecular heparin, since there is no data on direct oral anticoagulants in pregnant women.²⁵ During the first trimester, vitamin K antagonists such as warfarin can be used if the dose is ≤ 5 mg/g, or low molecular weight heparin or intravenous (IV) unfractionated heparin may be used.²⁶ Use of low molecular weight heparin should include a periodic evaluation of anti-Xa factor. In order to prevent life-threatening fetal bleeding, women should be converted to IV unfractionated heparin prior to planned delivery.

Non-vitamin K antagonist oral anticoagulants should be avoided due to limited data and experience in pregnancy.²⁷

Although data on stroke risk and AF during pregnancy is limited, pregnant women with AF due to mitral stenosis should be on anticoagulants. The CHA₂DS₂-VASC score has not been validated during pregnancy, but the 2018 European Society of Cardiology guidelines recommend the same criteria for using anticoagulants as in nonpregnant patients.²⁵ The 2023 American AF guidelines recommend shared decision-making since anticoagulation during pregnancy has not been validated in pregnancy.²⁶

The increasing incidence of AF during pregnancy underscores the importance of knowing how to evaluate and manage the risk of heart failure and stroke from this arrhythmia. The 2023 American College of Cardiology/American Heart Association/American College of Clinical Pharmacy/Heart Rhythm Society Guideline for the Diagnosis and Management of Atrial Fibrillation is summarized in Table 1, ²⁶ and an overview of the management of paroxysmal supraventricular tachycardia and AF is shown in Figure 1.

Figure 1

Ventricular Arrhythmias

Ventricular tachycardia (VT) during pregnancy is rare, with a prevalence of 2 per 100,000 hospital admissions; the risk is significantly higher among pregnant women with congenital heart disease, with a prevalence of 4.5 to 15.9 per 1,000 pregnancies.^11,28 VT occurs at a higher rate in pregnant women with underlying nonischemic cardiomyopathy.²⁹ VT in the setting of spontaneous coronary artery dissection and spasm has been reported.³⁰ Just like in nonpregnant women, VT in a pregnant patient without structural heart disease is typically hemodynamically well-tolerated.³¹

In pregnant patients with structural heart disease, VT treatment is tailored to the underlying disease. Beta-blockers and lidocaine are safe for hemodynamically stable VT, and Class 1C agents are contraindicated in patients with structural heart disease and coronary artery disease.^32,33 Conversely, in the absence of structural heart disease, VT is treated with beta-blockers, including propranolol and metoprolol.³⁴ Sotalol or flecainide can be used for patients with recurrent and symptomatic VT who are already on beta-blockers. Verapamil is another alternative option for the treatment of fascicular VT.³⁵

VT associated with hemodynamic instability should be treated with emergent direct current cardioversion due to the high risk of fetal demise. Higher energies at 100 to 360J, if needed, can be used in life-threatening situations if all other treatments have been exhausted. Even though amiodarone is generally contraindicated, it can be used if all other treatments have failed.¹⁰ IV magnesium (1-2 mg) can be used for torsades de pointes.³³

Inherited Arrhythmia Syndromes

Patients with inherited arrhythmia syndromes (IAS) effectively tolerate pregnancy and lactation. Management includes prepregnancy counseling, disease-specific testing, and optimization of treatment, including medications and defibrillator management. Thorough planning of labor and delivery, review of drugs after delivery, and a newborn cardiology assessment should be part of a multidisciplinary approach.

1. Long QT syndrome is the most common IAS. Risk factors for ventricular arrhythmias include a previous history of VT, SCA, and QTc > 470 msec. The risk of ventricular arrhythmias increases significantly in the 9-month postpartum period, especially for long QT type 2.^40,41 Long QT syndrome type 1 poses an elevated risk at the time of delivery due to adrenergic stimulation.⁴² Nonselective beta-blockers such as propranolol are the preferred agent, but if the patient is stable on nadolol before pregnancy, it can be continued during the pregnancy.⁴² Mexiletine is the second line of treatment in cases of recurrent VT despite beta-blockers.⁴² Concomitant QTc prolonging therapy should be avoided, and if oxytocin is needed, close telemetry and electrocardiographic monitoring are vital in the multidisciplinary care of these patients.

2. In patients with catecholaminergic polymorphic VT, nonselective beta-blockers or flecainide can be used.⁴²

3. Brugada syndrome is much more common in men, and quinidine reduces VT during pregnancy.⁴³

4. Pregnancy with a preexisting diagnosis of arrhythmogenic right ventricular cardiomyopathy is well-tolerated, and beta-blockers should not be interrupted. However, pregnancy is contraindicated in patients with biventricular disease and left ventricular ejection fraction of less than 30%.⁴⁴

A summary of the pharmacological treatment options is listed in Table 2.

Catheter Ablation

Early electrophysiology consultation for pharmacologic therapy or catheter ablation is recommended in recurrent drug-refractory SVT or tachycardia-induced cardiomyopathy.^44,45 The radiation dose for common electrophysiology interventions in a fetus is unlikely to exceed the 50 mGy negligible risk threshold for excess malignancy. Abdominal lead shielding leads to a 3% lower radiation dose.⁴⁶ With technological advances, these ablations can be safely performed using nonfluoroscopic electroanatomic mapping, catheter navigation systems, and intracardiac echocardiograms. Catheter ablation should be delayed until the second trimester, if possible.^25,44 If fluoroscopy is necessary, lead abdominal shielding must be performed.⁴⁷

Catheter ablation may be an alternative option in refractory, symptomatic cases of AF but may need to be deferred after delivery.²⁵ Case reports of VT ablation in incessant and recurrent VT have been reported, but ablation is a last-resort option.⁴⁸

Cardiac Implantable Electronic Devices

High-risk Patients

The pillars of cardiac risk assessment in pregnant patients are a comprehensive history and physical examination, 12-lead echocardiogram, and transthoracic echocardiogram.¹⁰ A personal history of cardiac disease (ie, syncope, congenital heart disease, structural heart disease, channelopathy, acquired heart disease, and isolated cardiac arrhythmias) and family history of sudden death or arrhythmias are as important as the obstetric history. From an arrhythmia perspective, patients with the highest risk are those with the potential for sudden cardiac death or arrhythmias leading to hemodynamic instability affecting maternal-fetal placental circulation. We rely on three models to assess cardiac risk in pregnancy: CARPREG-risk score (CARdiac disease in PREGnancy),^61,62 ZAHARA-risk score (Zwangerschap bij Aangeboren HARtAfwijkingen I),^63,64 and the modified World Health Organization (mWHO) classification based on expert consensus.⁶⁵ In the multicenter CARPREG II risk score,⁶⁶ patients with prior cardiac events or arrhythmias have a 15% risk of maternal cardiac complications during pregnancy (ie, cardiac death, cardiac arrest, pulmonary edema, sustained arrhythmia requiring treatment, thromboembolism, stroke, myocardial infarction, and vascular dissection). Most arrhythmias occur in the antenatal period,⁶⁶ which creates a unique opportunity for prepregnancy counseling. In cases of heart failure, the arrhythmias take place in the third trimester or early postpartum.⁶⁶ The ZAHARA risk score relates to congenital heart disease, where a history of prior arrhythmias confers a 7.5% risk of future cardiac complications. If the patient is additionally on cardiac medications, the risk can increase up to 41.5%. In 2011, the European Society of Cardiology guidelines⁶⁷ on managing diseases during pregnancy recommended estimating maternal risk according to the mWHO. From an arrhythmia perspective,²⁵ mWHO Class I (very low risk) includes isolated atrial or ventricular ectopic beats; mWHO Class II (low to moderate risk) includes most arrhythmias, mWHO Class II-III is hypertrophic cardiomyopathy and congenital heart disease, and mWHO IV is severe ventricular dysfunction, which puts patients at a high risk for material mortality (and therefore pregnancy is contraindicated). Maternal cardiovascular events occur in 24.2% of cases with higher mWHO classes.⁶⁷ High-risk arrhythmias include both ventricular and atrial arrhythmias. Depending upon the clinical circumstances, both nonsustained and sustained VT can suggest structural heart disease, cardiomyopathies, or cardiac ischemia. In adults with congenital heart disease, atrial arrhythmias are associated with increased risk of mortality.⁶³ Pre-pregnancy counseling in patients with Wolff-Parkinson-White syndrome⁶⁸ and congenital long-QT syndrome is warranted.⁶⁹

Multidisciplinary Cardio-obstetric Team

Cardio-obstetrics is a new emerging subspecialty that aims to improve maternal and fetal outcomes.^70,71 The multidisciplinary group has specialists in cardiology, maternal and fetal medicine, obstetrics, anesthesiology, neonatologists, genetics, imaging, labor and delivery nurses, and pharmacy.⁷² The goals of care and management are usually divided into stages: pre-conception, pregnancy, delivery, and postpartum. A multidisciplinary approach including cardiology, electrophysiology, heart failure, obstetrics, maternal-fetal medicine, anesthesiology, and nursing with precise planning and communication of plans for labor and delivery is paramount to ensure the safest possible outcomes for this high-risk medical condition (Figure 3).

Figure 3

Future Directions

Incorporating machine learning and artificial intelligence into our diagnostic algorithms will continue to evolve and help us identify individuals in the antenatal period who are considered high risk and require additional monitoring. Little data exists on managing arrhythmias during pregnancy and the effect on the pregnant person and the fetus. There is no comparison of effective antiarrhythmic interventions in this patient population. Hopefully, the Registry Of Pregnancy And Cardiac disease (ROPAC) study⁷³ and the Randomized Evaluation of Bromocriptine In Myocardial Recovery Therapy (REBIRTH) trial⁷⁴ will continue to provide some insights into pregnant people with cardiovascular disease.