FRCA Notes

Arrhythmias in Obstetrics

This page should be viewed alongside the overview page on cardiac disease in pregnancy.

Resources

  • Pregnancy is a well-recognised risk factor for arrhythmia, and arrhythmia may be the first presentation of undiagnosed structural heart disease
  • AF and SVT are the most common arrhythmias in pregnancy
  • Sudden arrhythmic death with a morphologically normal heart contributed to 18% of cardiac maternal deaths in MBRRACE-UK (2022)
  • Delayed cardioversion and inappropriately withheld antiarrhythmics were cited as contributing factors; management should follow the same principles as in the non-pregnant patient

  • Arrhythmias arise from disturbances of impulse generation, conduction, or both

Structurally normal heart

  • Haemodynamic: ↑ blood volume, HR and stroke volume, with physiological LVH, stretch the myocytes
    • Causes early afterdepolarisations, a shortened refractory period and slowed conduction
  • Hormonal: oestrogen and progesterone are proarrhythmic
    • Oestrogen ↑ L-type calcium channel expression in the SA node, accelerating pacemaker depolarisation and HR
    • ↑ automaticity and adrenergic responsiveness
  • Autonomic: ↑ sympathetic activity, particularly during labour and delivery
  • Pharmacokinetic: ↑ volume of distribution, altered protein binding and ↑ renal clearance may cause subtherapeutic antiarrhythmic levels

Other causes

  • Structural heart disease: congenital (particularly scar-related after Fontan, Mustard/Senning or ToF repair), valvular, ischaemic, cardiomyopathy including PPCM
  • Inherited channelopathies: long QT, Brugada, CPVT
  • Accessory pathways e.g. WPW
  • Triggers: electrolyte disturbance (K+, Mg2+), sepsis, thromboembolism, thyroid disease, OSA, obesity, drugs (alcohol, cocaine, amphetamines)

ECG changes in normal pregnancy

  • Sinus tachycardia
  • Shortened PR, QRS and QT intervals
  • Left axis deviation (15-20°) from diaphragmatic elevation
  • Small Q waves and T wave inversion in the inferior leads and V1-3
  • Atrial and ventricular ectopics
  • There is no upper limit of normal HR in pregnancy, but a resting HR of 100-115/min or more may warrant investigation

  • Pregnancy-related admissions with arrhythmia are rising, partly due to older maternal age, comorbidity, assisted reproduction and more women surviving congenital heart disease
  • Risk factors: age >40, BMI >30, low income
  • Recurrence in pregnancy with a prior history: AF 50%, SVT 52%, VT 27%
  • Most arrhythmias occur by the end of the second or start of the third trimester

Maternal risks Foetal/neonatal risks
↑ mortality (particularly VT) Preterm birth
Heart failure Low birth weight
Pre-eclampsia, abruption Foetal distress, NICU admission
PPH, preterm labour Stillbirth (8x in LQTS)
↑ caesarean delivery rate Neonatal death

Risk classification (mWHO 2.0, ESC 2025)


mWHO 2.0 class Arrhythmia
I Isolated atrial or ventricular ectopics
II Most supraventricular arrhythmias
Bradycardia requiring a pacemaker
II - III Low-risk LQTS (no events, on full-dose beta-blocker)
Low-risk CPVT (well controlled)
Brugada without previous events
III Sustained VT of any aetiology
LQT2 (post-partum)
Symptomatic or poorly controlled LQTS/CPVT
Brugada with previous events

  • Women in mWHO 2.0 class II-III and above should be managed by a Pregnancy Heart Team from pre-conception onwards
  • Ideally, symptomatic arrhythmias are treated (e.g. ablation, device insertion) before pregnancy

  • Detailed history of symptoms: timing, duration, severity, precipitating and relieving factors
  • Exclude structural heart disease and medical comorbidity
  • Consider PE, ischaemic heart disease and aortic dissection, particularly with chest pain or syncope

Red flags

  • Palpitations with syncope or presyncope, chest pain, dyspnoea or PND
  • Palpitations precipitated by exercise
  • Known structural or congenital heart disease, particularly with previous surgery
  • Family history of sudden death or inherited arrhythmia

Investigations

  • 12-lead ECG at baseline and during the arrhythmia
  • Bloods: FBC, U&E, K+ and Mg2+, glucose, LFTs, TFTs, VBG, troponin, NT-proBNP, sepsis markers
  • Urinalysis: protein:creatinine ratio, catecholamines
  • Echocardiogram: recommended for all new-onset cardiac symptoms
  • Holter monitoring (24 hours to 14 days) or implantable loop recorder, with a low threshold for prolonged monitoring
  • CXR, V/Q or CTPA if indicated
  • Non-contrast MRI if echo is inconclusive
  • Device interrogation if a pacemaker or ICD is present
  • Adenosine may be diagnostic in narrow complex tachycardia

  • Management depends on arrhythmia type, presence of structural heart disease and haemodynamic stability
  • Management essentially follows the Resus Council UK guidance for management of tachy- and brady-arrhythmias
  • Subtle differences include:
    • Avoiding DOACs for anticoagulation in AF/AFlutter
    • Lower threshold for immediate DCCV of sustained, pulsed VT
    • Amiodarone is a last resort but should not be withheld if other drugs fail; discuss neonatal hypothyroidism and neurodevelopmental risks

Anti-arrhythmic drugs in pregnancy and lactation


Drug Pregnancy considerations Breastfeeding
Beta-blockers IUGR and neonatal hypoglycaemia (mainly atenolol); sotalol prolongs QTc Compatible
Verapamil, diltiazem Compatible Compatible
Digoxin Compatible Compatible
Adenosine Limited data suggest no foetal harm Considered compatible
Flecainide, propafenone Limited data; no adverse foetal effects reported Considered compatible
Magnesium, lidocaine Compatible Compatible
Amiodarone Foetal thyroid dysfunction and goitre; prolongs QTc Contraindicated (iodine in milk)
Warfarin Embryopathy, foetal loss and foetal anticoagulation Compatible


  • Synchronised cardioversion is safe in all trimesters
  • Restoring sinus rhythm improves maternal haemodynamics and therefore placental perfusion
  • Small risk of foetal bradycardia requiring emergency caesarean delivery, but this should never delay cardioversion

Anaesthetic considerations

  • Notify cardiology, anaesthetic and obstetric teams
  • Monitored environment with difficult airway equipment and the facility to perform caesarean delivery
  • Aspiration risk from the gravid uterus and relaxed lower oesophageal sphincter rises with gestation
    • Sedation may be considered <20 weeks
    • Beyond 20 weeks, RSI and tracheal intubation are often appropriate
  • Antacid prophylaxis
  • Left lateral tilt if >20 weeks
  • Vasopressors (phenylephrine, metaraminol) to support BP
  • Choice of agents (propofol, opioids, benzodiazepines) is individualised to fasting status, gestation, haemodynamics and whether TOE is planned

Conduct

  • Standard or antero-posterior pad position
  • Biphasic energy as for non-pregnant patients (70-150J)
  • Up to 3 escalating shocks, then IV amiodarone and repeat
  • Gestation-appropriate FHR monitoring before (if feasible) and after
  • 12-lead ECG and monitoring for 12-24 hours afterwards; continue antiarrhythmics and thromboprophylaxis

Catheter ablation

  • For tachyarrhythmias refractory to drugs, in experienced tertiary centres
  • Zero-fluoroscopy techniques with 3D electroanatomical mapping are recommended, allowing ablation in all trimesters

Implantable devices

  • ICDs: survivors of VT/VF arrest, sustained VT, channelopathies, HCM
  • Pacing: symptomatic bradyarrhythmia (rarely needed as a new device in pregnancy); overdrive pacing for torsades
  • CRT for severe heart failure with LBBB
  • Devices should be checked during pregnancy: settings, battery and lead integrity

Peripartum device management

  • Pacemakers and ICDs can remain on for labour and procedures below the umbilicus (British Heart Rhythm Society)
  • Bipolar diathermy, or short bursts of monopolar, to minimise electromagnetic interference
  • Defibrillation pads applied and a magnet available
    • Magnet on a pacemaker: asynchronous (fixed rate) mode
    • Magnet on an ICD: disables anti-tachycardia therapy; pacing usually unaffected
  • Suxamethonium fasciculations may cause oversensing in older unipolar systems, but it is safe with modern devices
  • Reactivate and reprogramme to pre-delivery settings afterwards

  • Risk of polymorphic VT, VF and sudden death
  • Genetic testing and family screening are recommended; ICDs are common

Long QT syndrome

  • The most common channelopathy
  • Beta-blockers at pre-pregnancy dose throughout pregnancy and lactation; nadolol and propranolol are the drugs of choice

  • The post-partum period is particularly high risk in LQT2
  • Triggers: sympathetic stimulation, Valsalva, electrolyte disturbance, hypothermia

  • Neuraxial techniques are safe; avoid adrenaline-containing local anaesthetic
  • Vasopressors: phenylephrine or metaraminol; avoid ephedrine
  • GA: TIVA is attractive as propofol may shorten QTc; isoflurane is the safest volatile
  • Most opioids are safe, except pethidine and methadone
  • Prophylactic magnesium infusion may reduce torsades risk

  • Drugs to avoid:
    • Suxamethonium
    • Ondansetron
    • Ergometrine
    • Ephedrine
    • Pethidine, methadone

Brugada syndrome

  • Coved ST elevation and T wave inversion in V1-2
  • Triggers: fever, electrolyte disturbance, ↑ vagal tone

  • Drugs to avoid are listed at brugadadrugs.org
  • Epidural bupivacaine infusion has been linked to VT; levobupivacaine or ropivacaine are recommended for labour epidurals
  • Single-shot spinal bupivacaine and lidocaine infiltration are safe; remifentanil PCA is a safe alternative
  • Phenylephrine is the vasopressor of choice
  • Propofol bolus and short infusions (e.g. for CS) are safe; avoid prolonged propofol infusions
  • Caution with misoprostol as it may cause fever
  • Isoprenaline should be available to treat an electrical storm

CPVT

  • Beta-blockers (nadolol or propranolol) throughout pregnancy and lactation
  • Flecainide is added if cardiac events occur in pregnancy

Peripartum management of the parturient with an arrhythmia


  • Review in the obstetric anaesthetic clinic: history, functional status, investigations and device function
  • Discuss analgesic and anaesthetic options for vaginal and caesarean delivery
  • An individualised delivery plan, agreed by the Pregnancy Heart Team, should cover:
    • Mode of delivery and intrapartum monitoring
    • Analgesic and anaesthetic options
    • Preferred uterotonics and drugs to avoid (e.g. QT-prolonging drugs in LQTS)
    • Equipment availability: defibrillator pads, magnet
    • Post-partum location and monitoring

Mode of delivery

  • Low-risk patients may labour spontaneously; vaginal delivery is preferred for most
  • Assisted second stage may be used in symptomatic patients, although the evidence is weak
  • Caesarean delivery for obstetric indications or cardiac contraindications to vaginal delivery e.g. intractable heart failure, coronary ischaemia, severe LVOTO, uncontrolled arrhythmias

Anticoagulants and antiplatelets

  • Haematology input to plan the timing of doses
  • Prophylactic LMWH: omit 12 hours before neuraxial blockade
  • Therapeutic LMWH: omit 24 hours before
  • UFH infusion: stop 4-6 hours before
  • Aspirin 75-150mg is not a contraindication; clopidogrel must be stopped 5-7 days before

  • Goals are to maintain sinus rhythm and haemodynamic stability and avoid triggers

Peripartum arrhythmia triggers

  • Anxiety, pain and sympathetic stimulation
  • Hyperventilation, Valsalva
  • Hypotension from neuraxial block or PPH
  • Hypoxia, hypercarbia, acidosis
  • Hypothermia, fever
  • Electrolyte disturbance
  • Uterotonics and other specific drugs

Monitoring

  • Low risk: SpO2, NIBP, temperature and fluid balance
  • Symptomatic or at risk of SVT/VT: continuous ECG ± arterial line
    • Arterial line allows beat-to-beat BP, electrolyte and gas sampling, titration of vasopressors and point-of-care testing in PPH
  • In theatre: Association of Anaesthetists standards ± TTE/TOE

Labour analgesia

  • Epidural analgesia is recommended in tachyarrhythmias, including those at risk of SVT or VT
    • Most effective analgesia; minimises tachycardia from pain, contractions and Valsalva
    • Can be extended for operative delivery
    • De novo epidural, CSE or DPE with low-dose bupivacaine and fentanyl
  • Entonox, IM diamorphine and fentanyl or remifentanil PCA can be used in most
  • Avoid pethidine in tachyarrhythmias owing to its anticholinergic effect

Anaesthesia for caesarean delivery

  • Neuraxial anaesthesia (spinal, epidural or CSE) is recommended for most
    • Sympatholytic, lower risk of tachyarrhythmia, better analgesia, less blood loss and VTE
  • GA if contraindicated, category 1 delivery or patient preference
    • Obtund the pressor response to laryngoscopy in tachyarrhythmias
    • Sugammadex may be preferable to neostigmine owing to a more stable haemodynamic profile

Vasopressors

  • Tachyarrhythmias: phenylephrine or noradrenaline (reflex bradycardia is beneficial)
  • Bradyarrhythmias: ephedrine (although associated with lower umbilical artery pH)
  • LQTS: metaraminol or phenylephrine

Uterotonics

  • Oxytocin is first line; slow infusion (2IU over 10 minutes then 12mU/min for 4 hours) reduces blood loss with minimal haemodynamic effect
  • Ergometrine: risk-benefit assessment in hypertension, symptomatic tachyarrhythmia, IHD and fixed output states; avoid in LQTS
  • Carboprost: avoid in severe asthma and significant pulmonary hypertension
  • Misoprostol: safe in most, caution in Brugada (fever)
  • Carbetocin has similar haemodynamic effects to oxytocin but is not studied in structural heart disease

  • High-risk patients: HDU with ECG monitoring for 12-24 hours
  • Continue antiarrhythmics; in LQT2 the post-partum period is the highest risk
  • Reactivate or reprogramme devices
  • Multimodal analgesia to limit sympathetic stimulation
  • VTE prophylaxis according to individual risk
  • Advice on breastfeeding compatibility of medications and contraception
  • Ongoing outpatient follow-up with the cardio-obstetric team