Management of a Recurrent Pregnancy-Related Incessant Adenosine-Sensitive Atrial Tachycardia

Abstract

A 27-year-old pregnant woman (29th week) reported palpitations, dizziness and exertional dyspnoea. The heart rate was 130 bpm at rest, up to 180 bpm during mild exertion, without haemodynamic compromise. The electrocardiogram (ECG) showed atrial tachycardia. An adenosine intermittent interruption of the atrial tachycardia was observed. Metoprolol combined with flecainide controlled the ventricular rate to 80–85 bpm followed by conversion to sinus rhythm. The patient stayed asymptomatic until a second pregnancy, when the same atrial tachycardia recurred. Symptoms were controlled by combining metoprolol and flecainide at an earlier stage.

Introduction

Cardiac arrhythmias are relatively rare during pregnancy. Atrio-ventricular re-entry supraventricular tachycardia (AVNRT) is most frequently encountered in this setting [1]. Atrial tachycardia during pregnancy is however rare. Managing such arrhythmias remains a challenge. The case of a recurring pregnancyrelated incessant atrial tachycardia is presented.

Case presentation

A 27-year-old female, 29 weeks into her first pregnancy, presented herself with complaints of palpitations, dizziness and exertional dyspnoea. The patient denied any previous history or symptoms of cardiac, pulmonary or other medical conditions before the pregnancy. At admission, the heart rate was 130 bpm at rest and peaked to 180 bpm during exertion, without signs of haemodynamic instability. The electrocardiogram (ECG) showed a narrow QRS complex supraventricular tachycardia (Figure 1A). A 24-hour Holter ECG showed persistence of the arrhythmia with a median heart rate of 120 bpm, minimum 90 bpm, maximum 187 bpm. With adenosine 6 mg intravenously, reversion to sinus rhythm was achieved, followed by immediate recurrence of the atrial tachycardia (Figure 1B). Anaemia and hyperthyroidism were excluded. Echocardiography revealed no structural heart abnormalities.

During the tachycardia, atrial wave polarity, RP>PR intervals, and tachycardia response during autonomous nervous system modulation ruled out AVRT or AVNRT, and indicated adenosine-sensitive atrial tachycardia (Figure 1B).

Progressively increasing dosages of metoprolol to 100 mg controlled the ventricular rate (Figure 2A). Subsequently, the addition of flecainide resulted in effective slowing of the ventricular rate to 80–85 bpm followed by conversion to sinus rhythm (Figure 2B). The therapy was increased gradually and in consultation with the obstetrics/gynaecology team of our institution for the regular monitoring of the vital parameters of the foetus.

After 37 weeks of gestation, a healthy infant was delivered through a Caesarean section. After delivery, the palpitations had ceased and stable sinus rhythm was documented at the out-patient clinic three weeks after delivery. Metoprolol and flecainide were stopped.

Until the patient’s second pregnancy at 12 weeks, there were no recurrences. At 15 weeks in the second pregnancy, the same therapy was prescribed (

Table 1. Metoprolol and flecainide dosages during the two pregnancies.

). Compared with the first pregnancy lower dosages of metoprolol (75 mg) and flecainide (50 mg twice daily) were required to achieve clinically effective rhythm control. As before, after the delivery of a second healthy infant, the episodes ceased.

Discussion

We describe the case of a pregnancy-related adenosine-sensitive recurrent persistent atrial tachycardia. During both pregnancies, combination of metoprolol and flecainide effectively controlled symptoms, without adverse effects on the foetus. In the second pregnancy, initiating therapy earlier allowed more effective control of the symptoms with lower dosages of both anti-arrhythmic drugs.

During pregnancy, the cardiovascular system undergoes physiological adaptations. Haemodynamic, hormonal and autonomic changes can be arrhythmogenic [1, 2]. Cardiac output increases 30–50%, especially in the first weeks of pregnancy, resulting in a 35% increase in stroke volume and a 15% increase in heart rate. Plasma volume increase causes stretching of atrial and ventricular cardiomyocytes, resulting in potential cellular electrophysiological alterations, such as early after depolarisations, shortened refractoriness, slowed conduction and increased electrical spatial dispersion (3). A higher heart rate at rest is a known arrhythmogenic factor [4]. Furthermore, oestradiol and progesterone have proarrhythmic properties [5]. Although the presence of underlying structural heart disease is a risk factor for supraventricular tachycardia, in most cases there is no history or evidence of cardiac illness.

Cardiac arrhythmias represent one of the most common cardiovascular disorders that may complicate a pregnancy (prevalence 0.1– 2%), AVNRT being by far the most frequent supraventricular tachycardia [1]. Conversely, atrial tachycardias are rare. In one reported case, successful management of persistent atrial tachycardia with high ventricular rate was obtained by introducing amiodarone 400 mg daily, after a loading dose of 800 mg for 1 week [6]. Another case report described recurring paroxysmal atrial tachycardia in three pregnancies effectively and safely treated with multiple cardioversions [7].

In the present case, an intravenous adenosine bolus was utilised, resulting only in a transient effect. Progressively increasing doses of metoprolol were needed to effect the ventricular rate. Full-dose flecainide was subsequently combined with metoprolol yielding a lasting clinical effect until the end of the pregnancy. Current evidence supports the prophylactic use of metoprolol with a high level of evidence as well as the use of flecainide [2].

The case presented here provides further evidence that the combination of metoprolol and flecainide, may be effective to treat pregnancy-related persistent atrial tachycardia. In the case of drug-refractory, symptomatic atrial tachycardia, radiofrequency ablation should be considered [5].

Take home messages

Incessant pregnancy-related atrial tachycardia rarely occurs during pregnancy. Therefore, the description of such cases is important for patient management.

In the present case, the atrial tachycardia responded to intravenous adenosine but recurred immediately.

A stepwise pharmacological approach was adopted, starting with progressively increasing dosages of metoprolol (up to 100 mg/ day), which resulted in effective control of the ventricular rate, followed by the addition of flecainide (50 mg twice daily), which achieved rhythm control.

During the second pregnancy earlier initiation of the same therapy was effective, utilising lower dosages of metoprolol and flecainide.