Supraventricular Tachycardia in Pregnancy: Pharmacologic and Interventional Strategies

Pregnancy can expose a previously silent arrhythmia or increase the frequency of established supraventricular tachycardia (SVT). Changes in blood volume, autonomic tone, resting heart rate and cardiac chamber size may lower the threshold for re-entry circuits, while anaemia, infection, thyroid disease, electrolyte disturbance and dehydration can intensify palpitations. The clinical task is to relieve maternal symptoms and protect haemodynamic stability while limiting fetal drug exposure and unnecessary procedural risk.

Most episodes are caused by atrioventricular nodal re-entrant tachycardia (AVNRT) or atrioventricular re-entrant tachycardia (AVRT), although focal atrial tachycardia and atrial flutter may present in a similar way. A careful electrocardiogram during the episode is valuable because treatment depends on the mechanism. Australian clinicians must also account for access to electrophysiology services, medication availability through the Therapeutic Goods Administration (TGA) and Pharmaceutical Benefits Scheme (PBS), and the practical realities of pregnancy care across metropolitan and regional settings.

Recognising risk and confirming the rhythm

A regular narrow-complex tachycardia with sudden onset and termination strongly suggests AVNRT or orthodromic AVRT. Symptoms can include rapid palpitations, breathlessness, chest discomfort, dizziness and presyncope. Some patients remain well perfused, while others develop hypotension, pulmonary oedema or myocardial ischaemia. A 12-lead ECG during the event should be obtained whenever possible, followed by a baseline ECG between episodes.

Assessment should include a medication and stimulant history, volume status, full blood count, electrolytes, renal function and thyroid testing when clinically indicated. Vomiting, diarrhoea, fever and poor fluid intake can be important triggers, particularly during the first trimester or in hot Australian weather. Caffeine and over-the-counter decongestants may also aggravate symptoms. The clinician should distinguish SVT from sinus tachycardia caused by pulmonary embolism, sepsis, haemorrhage, severe anaemia or thyroid disease.

The Journal of Arrhythmia provides access to peer-reviewed work on electrophysiology, ablation and device therapy that can support specialist decision-making. In practice, a pregnant patient with recurrent symptomatic episodes may need coordinated review by obstetrics, cardiology, anaesthesia and, where available, an electrophysiologist. This coordination is easier in Sydney, Melbourne, Brisbane, Perth and Adelaide than in remote areas, where retrieval pathways and telehealth consultation may be essential.

Acute treatment with maternal and fetal safety in mind

Initial management begins with positioning, reassurance, cardiac monitoring, intravenous access and correction of reversible triggers. Vagal manoeuvres are appropriate for a stable regular SVT. A modified Valsalva manoeuvre is generally preferred; carotid sinus massage should be avoided in patients with carotid disease or a relevant bruit. These measures may terminate AVNRT or AVRT without drug exposure.

When vagal manoeuvres fail, intravenous adenosine is usually the preferred acute medicine for a stable regular narrow-complex tachycardia. Its very short half-life limits sustained maternal and fetal exposure, and available clinical experience supports use when clinically indicated. It should be administered with continuous ECG monitoring and resuscitation capability because transient flushing, chest tightness or unpleasant awareness may occur. Adenosine is less useful for atrial tachycardia and will not reliably terminate atrial flutter, although it can reveal atrial activity.

If adenosine is ineffective or contraindicated, an intravenous beta blocker such as metoprolol may be considered, or verapamil may be used in selected patients after excluding pre-excitation and ventricular dysfunction. Verapamil should not be combined casually with beta blockade because of bradycardia and hypotension risk. Intravenous drugs require careful dose selection and observation of maternal blood pressure, uteroplacental perfusion and fetal heart rate. Treatment should be individualised rather than based solely on gestational age.

Ongoing medicines for recurrent episodes

For frequent or disabling SVT, oral metoprolol or another suitable beta blocker is often considered, with the lowest effective dose and regular review. Propranolol may be appropriate in selected cases. Atenolol is generally avoided where alternatives exist because of concern about fetal growth restriction, particularly with early or prolonged exposure. Maternal heart rate, blood pressure, symptoms and fetal growth should be monitored during ongoing therapy.

Digoxin can have a role in selected patients, especially when ventricular function is preserved and beta blockers are unsuitable or insufficient. Flecainide may be considered for refractory SVT or specific accessory-pathway-related arrhythmias under specialist supervision. Sotalol requires caution because of QT prolongation and proarrhythmic potential. Amiodarone is generally reserved for life-threatening arrhythmia when safer options are ineffective, because fetal thyroid, growth and neurodevelopmental effects are concerns.

Medication decisions should include a discussion of evidence quality. Much pregnancy pharmacology relies on observational data, registries and accumulated clinical experience rather than randomised trials. Australian prescribers should check current TGA product information, local hospital protocols and specialist advice rather than assume that a medicine’s non-pregnancy indication defines its pregnancy safety. PBS listing may influence affordability, but a listed medicine is not automatically the best choice for an individual pregnancy.

When electrical cardioversion or ablation is needed

Haemodynamic instability requires urgent synchronised direct-current cardioversion. Hypotension, shock, ongoing chest pain, pulmonary oedema or severe altered mental status should not be managed with prolonged attempts at drug therapy. Electrical cardioversion is considered acceptable during pregnancy when clinically necessary. Maternal oxygenation and circulation take priority, with fetal assessment before and after the procedure when circumstances permit. Anaesthetic planning should involve obstetric and cardiac teams.

Elective cardioversion may be considered for persistent symptomatic tachyarrhythmia that cannot be controlled pharmacologically. The possibility of thromboembolism must be assessed if the rhythm is atrial flutter, atrial fibrillation or another sustained atrial arrhythmia; this issue is different from typical short episodes of AVNRT or AVRT. Anticoagulation decisions should reflect rhythm duration, structural heart disease and validated risk assessment, not the presence of palpitations alone.

Catheter ablation is usually planned before conception for patients with recurrent, poorly tolerated or drug-refractory SVT. Radiofrequency or cryoablation can provide a definitive treatment and may avoid medication during pregnancy. Pre-pregnancy counselling should review the mechanism, procedural success, recurrence risk and contraception or fertility plans. Ablation is also an opportunity to document the arrhythmia clearly when an ECG has not been captured during symptoms.

If SVT becomes severe and refractory during pregnancy, ablation can be performed in carefully selected cases at an experienced centre. Techniques that minimise or eliminate fluoroscopy, including three-dimensional electroanatomical mapping and intracardiac imaging, are preferred. When timing is flexible, the second trimester is often considered the most practical period, but maternal instability may require intervention at any stage. Radiation exposure must be justified, optimised and documented in line with Australian radiation safety requirements and relevant ARPANSA principles.

Planning care across Australian services

A written plan helps patients know when to seek urgent care and helps emergency teams act quickly. It should include the suspected rhythm, previous ECG findings, effective vagal manoeuvres, medicines that have worked or failed, relevant allergies and the treating cardiology contact. The plan should also state that fainting, persistent chest pain, severe breathlessness or sustained rapid heart rate warrants emergency assessment through Triple Zero (000).

Women living outside major centres may face long travel distances, limited overnight cardiology cover and delayed access to electrophysiology. Early referral from a regional hospital to a tertiary maternity-cardiology service can prevent fragmented care. A patient from regional New South Wales, Queensland or Western Australia may require coordination between local emergency staff, retrieval services and a metropolitan electrophysiologist. Telehealth can support planning, but it does not replace immediate stabilisation during an unstable episode.

Antenatal care should include fetal growth surveillance when prolonged beta-blocker treatment is used, alongside routine obstetric monitoring. Birth planning is usually vaginal unless there is an obstetric indication or significant cardiac disease. The delivery team should know the rhythm history, medication schedule and cardioversion plan. Postpartum haemodynamic shifts can precipitate recurrence, so observation after birth and review of breastfeeding-compatible medicines are important.

Clinicians and trainees can explore themed collections for focused material on arrhythmia management, ablation and electrophysiology. Reviewing current evidence is particularly relevant where local practice involves TGA restrictions, hospital formulary differences, PBS affordability and referral requirements. Shared decisions should balance symptom burden, episode frequency, gestational age, structural heart disease and the patient’s preferences.

Safe management of SVT in pregnancy depends on rapid rhythm recognition, correction of reversible triggers and a graded approach to treatment. Vagal manoeuvres and adenosine are central for stable regular episodes; beta blockers and selected antiarrhythmics may support longer-term control; cardioversion and low-fluoroscopy ablation remain important options when medication fails or maternal risk rises. Australian care is strongest when emergency, obstetric and electrophysiology teams share a documented plan. Explore the Journal of Arrhythmia’s clinical resources and apply current specialist guidance to each patient’s circumstances.