Impact of Paroxysmal Supraventricular Tachycardia on Pregnancy Outcomes

Abstract

Background

Paroxysmal supraventricular tachycardia (PSVT) is one of the most common arrhythmias in pregnant women. However, studies investigating the risk of PSVT in pregnancy are lacking. In pregnancy, we aimed to determine the (1) proportion of women presenting with new-onset PSVT, (2) impact of prior PSVT history on episode severity and management, and (3) rate of adverse maternal and fetal or neonatal outcomes associated with PSVT.

Methods

Retrospective case-control study: 77 consecutive pregnancies in 75 women referred to the St Paul’s Hospital Cardiac Obstetrics Clinic (2010-2022) with a history or new presentation of PSVT. Maternal obstetric and fetal or neonatal adverse outcomes were compared to a healthy control group.

Results

Sixty-three pregnancies (82%) had a history of PSVT and 14 (18%) were new-onset in pregnancy. Sixty-eight percent of those with PSVT history had recurrence in pregnancy. Women with a recent history of PSVT within 5 years of pregnancy were more likely to experience recurrence than women with a remote history (81% vs 31%, P < 0.001). This group also experienced more frequent PSVT during pregnancy and increased rates of chemical cardioversion (38% vs 13%, P = 0.05). There were similar rates of adverse obstetric (8% vs 2%, P = 0.24) and fetal or neonatal outcomes (17% vs 19%, P = 0.72) between the PSVT group and controls.

Conclusions

PSVT events were safely managed in pregnancy with similar obstetric and fetal or neonatal outcomes as controls. However, recurrence of PSVT during pregnancy is frequent and leads to management complexities among those with a history, reinforcing the need for pre-pregnancy counselling and catheter ablation for definitive management.

Maternal arrhythmias are a common cardiac complication during pregnancy that can pose a threat to the health of the mother and fetus. One of the most common arrhythmias in pregnant women is paroxysmal supraventricular tachycardia (PSVT).^1,2 PSVT is defined as any tachyarrhythmia with a heart rate of 120 beats per minute or greater that requires atrial or atrioventricular junctional tissue for its initiation and maintenance.³ The prevalence of PSVT in pregnancy is reported in 22 to 33 cases per 100,000 pregnancies, with atrioventricular nodal re-entrant tachycardia and atrioventricular re-entrant tachycardia (Wolff-Parkinson-White syndrome) being the primary mechanisms for its development.3, 4, 5 Although PSVT is usually well-tolerated, it can lead to new onset or exacerbation of symptoms associated with pregnancy such as shortness of breath, palpitations, presyncope, and syncope.¹

The pathophysiology of PSVT in pregnancy is complex and multifactorial because of physiologic changes commencing in the first trimester.⁶ First, hemodynamic changes in the form of an expanded maternal circulating volume and a fall in systemic vascular resistance contribute to an increased cardiac output.⁴ This predisposes pregnant women to arrhythmias. Second, autonomic changes through increased levels of circulating catecholamines lead to additional adrenergic receptors, increasing cardiac excitability and risk for arrhythmias.⁶ Last, hormonal changes in the form of increased levels of estrogens act similarly by increasing cardiac excitability.⁶

Although maternal physiologic changes during pregnancy may predispose patients to PSVT, little is known on whether pregnancy increases the risk of new-onset PSVT.⁴ Although studies have shown that episodes of PSVT occur with increased frequency during pregnancy, cases of new-onset PSVT during pregnancy remain rare when compared to patients with established risk factors, such as pre-existing PSVT, structural heart disease, or congenital heart disease.^1,7 Furthermore, there are little data on whether outcomes differ among patients with new-onset PSVT vs pre-existing PSVT. The objectives of this study were to determine (1) the proportion of women presenting with new-onset PSVT in pregnancy; (2) the impact of prior PSVT history on episode severity and management during pregnancy; and (3) the rate of adverse maternal and fetal or neonatal outcomes among women with PSVT.

Methods

Study design and population

This is a retrospective case-control study of pregnancies referred to the St Paul’s Hospital Cardiac Obstetrics Clinic. The cases were consecutive patients referred for findings of or symptoms secondary to atrioventricular nodal re-entrant tachycardia (AVNRT) or atrioventricular re-entrant tachycardia (AVRT) PSVT between January 2010 and January 2022. Exclusion criteria were (1) pregnancy that resulted in spontaneous abortion <20 weeks and/or (2) documented structural cardiac disease on echocardiographic study. The catchment area for the St Paul’s Hospital Cardiac Obstetrics Clinic encompasses the entire population of British Columbia, which is more than 5.6 million people. Clinic referral criteria includes any pregnant woman with a known cardiac diagnosis or symptoms necessitating further workup for potential underlying cardiac disease. A total of 2388 patients were referred to the clinic during the study period. The PSVT cohort consisted of 77 pregnancies in 75 women who fulfilled the study criteria.

To evaluate the risk of adverse maternal and fetal or neonatal outcomes in the PSVT cohort, a healthy control group was needed. The control group consisted of age-matched women referred and seen in the Cardiac Obstetrics Clinic who were found to have no underlying cardiac disease. Common reasons for referral among the control group included heart murmur and shortness of breath of unclear etiology, none of which were deemed to be of significance. Women with a known cardiac diagnosis were excluded. The control group consisted of 57 women meeting these criteria during the study period. This study was approved by the Research Ethics Board at our institution.

Baseline data

Clinical and electrocardiographic data were collected at the time of the initial clinic visit for the PSVT group. History was reviewed to determine if PSVT was new-onset in pregnancy or pre-existing. All patients were triaged by a multidisciplinary team and evaluated for structural heart disease. When available, prior echocardiograms were consulted to confirm the absence of structural heart disease. For patients without prior echocardiographic study or those presenting with new-onset PSVT in pregnancy, echocardiograms were conducted during the pregnancy. Clinic visits and investigations were dictated by clinical status. Patients were systematically seen within 4 weeks of referral, and plans for re-evaluation were dependent on symptom status. Furthermore, all patients were seen at 28-32 weeks’ gestation at the latest to finalize a delivery care plan. Electrocardiographic data were collected at each visit and Holter studies were conducted for patients who were unaware of PSVT symptoms during the pregnancy. The normal control group was followed as per routine obstetric and maternal care.

The following data were recorded for both PSVT and control groups: age, comorbid medical conditions, smoking history, New York Heat Association (NYHA) functional class, gestational age, parity status, symptoms of presyncope, syncope, palpitations, and cardiac medications during pregnancy such as β-blockers for underlying PSVT management and aspirin for preeclampsia prophylaxis. Obstetric and maternal risk factors for adverse fetal and neonatal outcomes were also recorded, including (1) smoking, anticoagulation use, multiple gestation, or maternal age <20 and >35 years; (2) prior pregnancy history of premature rupture of membranes, incompetent cervix, or caesarean section; and (3) during the current pregnancy, intrauterine growth restriction, antepartum bleeding >12 weeks’ gestation, febrile illness, or uterine/placental abnormalities.

PSVT data

Among women with pre-existing PSVT, standard 12-lead electrocardiograms (ECGs) and/or ambulatory ECGs documenting PSVT were examined to determine origin. The number of known PSVT episodes, requirement for preventative pharmacologic therapy, emergency department visit and management details, and need for PSVT ablation prior to pregnancy were documented. PSVT episodes were documented according to a previously used frequency scoring system out of 3, where 0/3 = no PSVT episodes, 1/3 = fewer than 1 PSVT episode every 3 months, 2/3 = fewer than 1 PSVT episode per month but at least 1 episode every 3 months, and 3/3 = at least 1 PSVT episode per month.⁸ Furthermore, PSVT episode frequency was reported using a 5-year cut-off before the documented pregnancy. As such, episode frequency was reported separately for the 5-year period prior to the documented pregnancy, and for the years preceding the 5-year cut-off. This was done as the implications of having more remote episodes of PSVT were thought to be different than more recent episodes.

Among all women with PSVT, the following clinical characteristics during pregnancy were documented: the number of PSVT episodes, trimester timing of episodes, need for preventative pharmacologic therapy and escalation of therapy over pregnancy, emergency department visit and management details, and PSVT in labour and delivery. The same frequency scoring system was used to report episodes during pregnancy. PSVT episodes in pregnancy were either patient reported or documented on ECG if occurring during an outpatient clinic visit, captured on outpatient Holter studies, or on presentation to the emergency department. For patient-reported cases, episodes were confirmed by a physician during scheduled appointments at the Cardiac Obstetrics Clinic based on the presence of definitive symptoms consistent with an episode of PSVT.

Maternal and fetal outcomes

All pregnant women with PSVT and the control group were followed from the time of referral until 6 months postpartum. Adverse outcomes during the ante-, peri-, and postpartum periods were classified as maternal cardiac, obstetric, and fetal or neonatal. Two physicians blinded to the women’s baseline characteristics independently verified adverse outcomes. Adverse cardiac outcomes were defined as pulmonary edema (documented by chest radiograph, or by crackles heard over at least one third of posterior lung fields and jugular venous distension), requirement for PSVT ablation, hospitalization for PSVT management, chemical and/or electrical cardioversion for PSVT, stroke, cardiac arrest, or cardiac death. Obstetric complications were defined as: maternal death from noncardiac causes, pregnancy-induced hypertension (systolic blood pressure ≥140 mm Hg and/or diastolic blood pressure ≥90 mm Hg measured on 2 separate occasions), preeclampsia (characterized by hypertension and proteinuria or end-organ dysfunction after 20 weeks’ gestation), or postpartum hemorrhage (blood loss >500 mL after vaginal delivery or >1000 mL after caesarean section, requiring transfusion or accompanied by a drop in hemoglobin level ≥20 g/L). Fetal and neonatal complications were defined as premature birth (<37 weeks’ gestation), small-for-gestational-age birth weight (<10th percentile for gestational age or <2500 g), respiratory distress syndrome, intraventricular hemorrhage, fetal death (after 20 weeks’ gestation and before birth), or neonatal death (from birth to age 28 days). Although many of the stated obstetric and fetal or neonatal outcomes would be unlikely to result from PSVT, these are commonly accepted outcomes used in the literature.

Statistical analyses

All data was analyzed using SPSS version 29.0 (SPSS, Inc, Chicago, IL). Data are presented as mean ± standard deviation. The 2-sided unpaired Student t test or Wilcoxon rank-sum test, as appropriate for distribution, was used to compare continuous variables between groups. The χ² test or Fisher exact test was used to analyze categorical variables between groups. P value of ≤0.05 was considered statistically significant.

Results

Baseline characteristics

Seventy-seven pregnancies in 75 women were seen in the Cardiac Obstetrics Clinic for PSVT assessment over the study period and fulfilled the study criteria. The mean gestational age at first evaluation in pregnancy was 25 ± 8 weeks (range 6-39 weeks). The age at delivery ranged from 23 to 44 years (Table 1). Other than an increased known diagnosis of Wolf-Parkinson-White (WPW), use of β-blockers, and the presence of obstetric and maternal risk factors in the PSVT group, the PSVT and control groups were similar with respect to age and comorbidities (Table 1). The specific obstetric and maternal risk factors in the PSVT group included maternal age >35 years (n = 27), prior history of caesarean delivery (n = 11), multiple gestation in the current pregnancy (n = 3), intrauterine growth restriction (n = 3), uterine or placental abnormalities (n = 3), smoking (n = 2), prior history of premature delivery or rupture of membranes (n = 1), and febrile illness (n = 1). The noted difference between the new-onset PSVT group vs controls was the increased obstetric and maternal risk factors in the former.

Table 1.

Baseline characteristics

Characteristic	New-onset PSVT cases (n = 14)	All PSVT cases (n = 77)	Normal controls (n = 57)	P value∗
Nulliparity	4 (29%)	29 (38%)	24 (42%)	0.60
Age, y	33.7±5.0	33.6±5.0	32.9±4.4	0.23
Known cardiac diagnoses
WPW	0 (0%)	16 (21%)	0 (0%)	<0.001
Other medical conditions
Hypertension	0 (0%)	0 (0%)	0 (0%)
Smoking history	0 (0%)	3 (4%)	0 (0%)	0.26
Hypothyroidism	2 (14%)	8 (10%)	3 (5%)	0.35
Diabetes	0 (0%)	0 (0%)	0 (0%)
NYHA class
Class I	13 (93%)	74 (96%)	53 (93%)	0.46
Class II	1 (0%)	3 (4%)	0 (0%)	0.26
Cardiac medications
Aspirin	1 (7%)	4 (5%)	0 (0%)	0.14
β-Blocker	1 (7%)	15 (20%)	0 (0%)	<0.001
LVEF, %	N/A	59.7±3.9	N/A
Obstetric risk factors†	8 (57%)	44 (57%)	20 (35%)	0.01

Data are REPORTED as mean ± SD or n (%).

LVEF, left ventricular ejection fraction; NYHA, New York Heart Association; PSVT, paroxysmal supraventricular tachycardia; WPW, Wolf-Parkinson-White.

^∗P value is for all PSVT cases vs controls. Boldface indicates significance (P ≤ .05).

^†Obstetric and maternal risk factors include smoking, anticoagulation use, multiple gestation and maternal age <20 and >35 years; a history of premature delivery or rupture of membranes, incompetent cervix, caesarean delivery; and during the current pregnancy, intrauterine growth restriction, antepartum bleeding >12 weeks’ gestation, febrile illness, and uterine or placental abnormalities.

PSVT prior to pregnancy characteristics

Sixty-three cases (82%) had a known diagnosis of PSVT prior to pregnancy and 14 (18%) had a new diagnosis of PSVT made in the current pregnancy (Figure 1). Among those with a known diagnosis of PSVT, 47 of 63 (75%) had at least 1 episode of PSVT within 5 years prior to pregnancy, with the majority having fewer than 1 episode every 3 months (Table 2). The mean number of emergency department visits for PSVT prior to pregnancy was 2.6, with 34 cases (54%) presenting to the emergency department at least once (Table 2). Chemical cardioversion was common at 41%, and the single woman requiring electrical cardioversion had presented with hemodynamic instability. Of the 20 women (32%) who underwent catheter ablation before pregnancy, 6 had multiple ablations. Only 3 of 20 of these women (15%) had recurrence of episodes during pregnancy. Conversely, of the 43 women who did not have an ablation, 40 (93%) experienced recurrence of PSVT during pregnancy. Women who did not have an episode within the 5 years before pregnancy had higher rates of ablation completion vs those who did (11 of 16 [69%] vs 9 of 47 [19%], P < 0.001).

Figure 1.

Flowchart depicting the distribution of PSVT cases in pregnancy, differentiating between women with new-onset cases and women with a prior diagnosis. PSVT, paroxysmal supraventricular tachycardia.

Table 2.

Pre-pregnancy PSVT Characteristics

Characteristic	Pre-pregnancy PSVT cases (n = 63)
Pre-pregnancy PSVT frequency
PSVT frequency ≤5 y prior to pregnancy	47 (75%)
Episode <1x in 3 mo	31 (66%)
Episode >1x in 1-3 mo	6 (13%)
Episode ≥1x in 1 mo	10 (21%)
PSVT frequency >5 y prior to pregnancy	16 (25%)
Episode <1x in 3 mo	11 (69%)
Episode >1x in 1-3 mo	2 (12%)
Episode ≥1x in 1 mo	3 (19%)
Pre-pregnancy PSVT management
PSVT termination
Always on own	12 (19%)
Always with Valsalva maneuver	5 (8%)
Emergency department visit	34 (54%)
1 emergency department visit	19 (30%)
>1 emergency department visit	15 (24%)
PSVT cardioversion
Chemical cardioversion	26 (41%)
IV adenosine	16 (25%)
β-blocker	5 (8%)
Adenosine and β-blocker	1 (2%)
Calcium channel blocker	3 (5%)
Magnesium	1 (2%)
Electrical cardioversion	1 (2%)
Ablation	20 (32%)

Data are presented as n (%).

IV, intravenous; PSVT, paroxysmal supraventricular tachycardia.

PSVT in pregnancy and maternal cardiac outcomes

During pregnancy, 57 of 77 cases (74%) experienced at least 1 episode of PSVT. The recurrence rate of PSVT during pregnancy among women with a history of the condition was 68% (Figure 1). Those with an episode within the preceding 5 years were more likely to experience recurrence in pregnancy (Table 3). Similarly, there was an increased frequency of PSVT episodes in pregnancy among women who had an episode within the preceding 5 years. With respect to PSVT presentation, slightly more than 60% of cases had episodes in multiple trimesters and 25% of cases were isolated to the third trimester. In 28% of cases, the PSVT would always self-terminate and, to a lesser degree, would always terminate with the use of Valsalva. Thirty-five women (61%) presented to the emergency department for symptoms related to PSVT, of whom 11 had a new PSVT presentation in pregnancy and 20 had PSVT within the 5 years prior to pregnancy.

Table 3.

PSVT in pregnancy characteristics and cardiac outcomes based on episode history

Characteristic	PSVT in pregnancy (n = 57)	PSVT in prior 5 y (n = 47)	No PSVT in prior 5 y (n = 16)	P value∗
PSVT in pregnancy details
PSVT in pregnancy		38 (81%)	5 (31%)	<0.001
PSVT frequency in pregnancy
Episode <1x in 3 mo	18 (32%)	10 (21%)	3 (19%)
Episode >1x in 1-3 mo	12 (21%)	11 (23%)	0 (0%)
Episode ≥1x in 1 mo	27 (47%)	17 (36%)	2 (13%)
At least 1 episode in 3 mo	39 (68%)	28 (60%)	2 (13%)	0.003
PSVT presentation
First trimester	2 (3%)
Second trimester	6 (11%)
Third trimester	14 (25%)
Multiple trimesters	35 (61%)
Labour and delivery	2 (3%)
PSVT termination
Always on own	16 (28%)	11 (23%)	1 (6%)	0.27
Always with Valsalva maneuver	6 (11%)	5 (11%)	1 (6%)	ns
Emergency department visit	35 (61%)	20 (42%)	4 (25%)	0.21
1 emergency department visit	19 (33%)	11 (23%)	3 (19%)
>1 emergency department visit	16 (28%)	9 (19%)	1 (6%)
Adverse cardiac outcomes
Pregnancies complicated by a cardiac event	31 (54%)	18 (38%)	3 (18%)	0.15
Hospital admission for PSVT management	4 (7%)	2 (4%)	0 (0%)	ns
Chemical cardioversion	30 (53%)	18 (38%)	2 (13%)	0.05
IV adenosine	21 (37%)	12 (26%)	2 (13%)
β-Blocker	6 (11%)	4 (9%)	0 (0%)
Adenosine and β-blocker	3 (5%)	2 (4%)	0 (0%)
Electrical cardioversion	2 (3%)	0 (0%)	1 (6%)	0.25
Ablation	2 (3%)	1 (2%)	0 (0%)	ns

IV, intravenous; PSVT, paroxysmal supraventricular tachycardia.

^∗P value is for comparison between those who experienced PSVT within the 5 years prior to pregnancy and those who did not. Boldface indicates significance (P ≤ .05).

Fifteen women in the PSVT cohort (20%) were on a β-blocker at baseline evaluation, and 6 of them had poorly controlled PSVT prior to the documented pregnancy. Fifteen women (20%) were started on a β-blocker because of increasing episodes of PSVT during pregnancy, 5 in the second trimester, and 10 in the third trimester. Two women had escalating doses of β-blockers in the third trimester.

Among all women who had a PSVT episode in pregnancy, the rate of adverse maternal cardiac outcomes was 54% (Table 3). There were no adverse cardiac outcomes in women who had a history of PSVT but did not have recurrence of episodes in pregnancy. Four women (7%) required admission to hospital for PSVT management with hospital stays of 1, 4, 5, and 8 days, respectively. Little more than 50% required chemical cardioversion in pregnancy, with 10 of these women presenting with new-onset PSVT. There was a higher rate of chemical cardioversion among women who experienced PSVT within the 5 years prior to pregnancy vs those with a remote history. Two women required electrical cardioversion for management of treatment-refractory PSVT, 1 presenting with hemodynamic instability due to new atrial fibrillation in the context of concurrent PSVT episodes. PSVT presentation was uncommon in labour and delivery, and the 2 cases were successfully terminated with adenosine and intravenous metoprolol, respectively, with no hemodynamic instability. Lastly, 2 women underwent ablation post-partum (2 days and 6 months post-partum), one presenting with new-onset PSVT in pregnancy and the other with PSVT within the 5 years prior to pregnancy. There were no other adverse cardiac outcomes in this cohort.

There was no difference in episode frequency among women who had a prior PSVT diagnosis and those who experienced new-onset PSVT in pregnancy (Table 4). Furthermore, the number of hospital admissions and success of nonpharmacologic methods of PSVT termination were similar between both groups. There was a trend to increased frequency of emergency department visits and need for chemical cardioversion among patients with new-onset PSVT in pregnancy.

Table 4.

Cardiac outcomes: new-onset vs pre-existing PSVT

Characteristic	New pregnancy onset PSVT (n = 14)	Prior PSVT∗ (n = 43)	P value
PSVT in pregnancy details
PSVT frequency in pregnancy
Episode <1x in 3 mo	5 (36%)	13 (30%)
Episode >1x in 1-3 mo	1 (7%)	11 (26%)
Episode ≥1x in 1 mo	8 (57%)	19 (44%)
At least 1 episode in 3 mo	9 (64%)	30 (70%)	0.75
PSVT termination
Always on own	4 (29%)	12 (28%)	ns
Always with Valsalva maneuver	0 (0%)	6 (14%)	0.32
Emergency department visit	11 (79%)	24 (56%)	0.13
1 emergency department visit	5 (36%)	14 (33%)
>1 emergency department visit	6 (43%)	10 (23%)
Adverse cardiac outcomes
Pregnancies complicated by a cardiac event	10 (71%)	21 (49%)	0.14
Hospital admission for PSVT management	2 (14%)	2 (5%)	0.25
Chemical cardioversion	10 (71%)	20 (47%)	0.11
IV adenosine	7 (50%)	14 (33%)
β-Blocker	2 (14%)	4 (9%)
Adenosine and β-blocker	1 (7%)	2 (5%)
Electrical cardioversion	1 (7%)	1 (2%)	0.43
Ablation	1 (7%)	1 (2%)	0.43

IV, intravenous; PSVT, paroxysmal supraventricular tachycardia.

^∗Patients with a previous diagnosis of PSVT who had at least 1 episode during pregnancy.

Obstetric and fetal outcomes

The rate of adverse obstetric outcomes was similar in the PSVT group vs controls (6 [8%] vs 1 [2%], P = 0.24). Among the PSVT group, preeclampsia occurred in 1 pregnancy (1%), gestational hypertension in 2 pregnancies (3%), and postpartum hemorrhage in 3 pregnancies (4%). There were no cases of noncardiac death in either group. The overall rate of adverse fetal outcomes in the PSVT group vs controls was similar (13 [17%] vs 11 [19%], P = 0.72). Rates of preterm delivery (<37 weeks) were similar between PSVT and control groups (8 [10%] vs 5 [9%], P = 0.75) as was small for gestational age (5 [6%] vs 7 [12%], P = 0.25). There were 2 neonatal deaths in the PSVT group; one was a stillbirth and the other neonate had neurologic issues and refractory seizures.

Sixty percent of the deliveries in the PSVT cohort (46 of 77 cases) were vaginal deliveries and induction was used in 33% of these cases. Caesarean deliveries occurred in the remaining 31 pregnancies for the following indications: previous caesarean delivery or planned (n = 16), breech or transverse position (n = 4), failure to progress (n = 3), fetal distress (n = 3), placenta previa (n = 2), presence of an ovarian cyst (n = 1), and large fibroids (n = 1). Caesarean delivery was not performed for cardiac indications in any of the women in the PSVT cohort.

Discussion

This is a retrospective case-control study of consecutive women receiving care for PSVT during pregnancy that explores the granular details around PSVT history, presentation and management in pregnancy, and outcomes. The rate of adverse maternal cardiac outcomes was 54% among women who had PSVT in pregnancy, driven by the need for chemical cardioversion. There was a similar rate of adverse obstetric and fetal or neonatal outcomes among the PSVT cohort as compared to controls. We found that 18% of all PSVT presentations in pregnancy were new-onset in our cohort. Among those with a history of PSVT, those with a more recent history within 5 years of pregnancy were more likely to have a recurrence of PSVT, higher burden of episodes, and trend to increased rates of adverse maternal cardiac outcomes in pregnancy than those with a more remote history.

The rate of adverse maternal cardiac outcomes was 54% among women who had PSVT in pregnancy, with most occurring in women who had PSVT within 5 years of pregnancy. This was mostly driven by PSVT requiring chemical cardioversion with adenosine in the majority of cases, followed by intravenous β-blocker. Electrical cardioversion was uncommon in pregnancy, undertaken in 2 women who had refractory PSVT. Although both had no episodes within the 5 years prior to pregnancy, they had underlying factors that likely contributed to the treatment-refractory episodes. One woman had a complex dichorionic-diamniotic pregnancy requiring emergency caesarean section at 28 weeks’ gestation and the other developed concurrent atrial fibrillation and required electrical cardioversion due to hemodynamic instability. There were 2 ablations during the post-partum period. One was in a woman who had highly recurrent PSVT in pregnancy, and the other was experiencing repeat episodes in the second trimester and elected to have an ablation.

The rates of adverse obstetric and fetal or neonatal outcomes were similar between the PSVT cohort and controls. The trend to hypertensive disorders of pregnancy and post-partum hemorrhage is likely related to the higher prevalence of obstetric risk factors in the PSVT cohort rather than the underlying diagnosis of PSVT. Although there were 2 neonatal deaths in the PSVT cohort, neither was attributable to this underlying diagnosis. One was a stillbirth involving a mother who had a history of WPW, for which she had 2 successful ablations years prior to pregnancy and had no recurrent episodes during the documented pregnancy. The second was a neonate that was flaccid at birth with neurologic issues and refractory seizures secondary to a case of endometritis; the mother only had a single, short-lived episode of new-onset PSVT in the second trimester, which self-resolved.

We found no difference in adverse fetal or neonatal outcomes between the PSVT cohort and controls. Discordant results were found in a large population study conducted by Chang et al. including pregnancies in Taiwan from 2001 to 2012 (n = 2,350,328). This study found that PSVT events during pregnancy were associated with worse fetal or neonatal outcomes, such as low birth weight, preterm labour, fetal stress, and obvious fetal abnormalities.² This is likely due to the fact that Chang et al. did not exclude mothers with underlying structural heart disease, which is known to be associated with adverse fetal or neonatal outcomes. Although patients with congenital heart disease were excluded and the authors state that the confounding effects of structural heart disease were minimized, the effects of PSVT on pregnancy cannot be fully isolated in such a study. Furthermore, the study did not consider some cardiomyopathies, which may have been significant in the higher rate of adverse fetal or neonatal outcomes among the PSVT group.²

A cohort study by Bekiaridou et al.⁹ of pregnant women aged 18-50 years with confirmed PSVT found a higher incidence of preterm labour in women with PSVT compared with controls (30.3% vs 8.6%; P < 0.001). Although both of our studies excluded women with structural heart disease, the difference in our findings may stem from Bekiaridou et al. only comparing women with confirmed PSVT episodes during pregnancy to controls, whereas our analysis incorporated all women in the PSVT cohort, including those with a diagnosis of PSVT prior to pregnancy who may not have experienced episodes during pregnancy. Regardless, our overall rate of preterm delivery was 10%, much lower than the reported 30% by Bekiaridou et al. Moreover, among those with PSVT in pregnancy in our cohort, the rate of pre-term delivery remained low at 7%. It may be that pre-term delivery in the Bekiaridou cohort was driven by a perceived need to induce earlier for cardiac indications whereas that was not the case in our cohort. Nonetheless, Bekiaridou et al. found no significant differences in the incidence of other obstetric complications between the PSVT and control groups. The burden of data suggest that the rate of obstetric complications directly attributable to PSVT events are low, but may occur indirectly due to actions taken as a result of PSVT events, such as planning for earlier delivery.

A prospective cohort study by Lee et al.⁷ found that among 207 pregnant women diagnosed with symptomatic PSVT, new-onset PSVT during pregnancy was rare, occurring in only 3.9% of cases. It was concluded that pregnancy was associated with a low risk of new-onset PSVT. Of the 77 total pregnancies in this PSVT cohort, 14 patients (18%) experienced new-onset PSVT in pregnancy. Although this is significantly less than the recurrence rate of 68% in those with previously diagnosed PSVT, our results show that PSVT can certainly occur de novo in pregnancy in the absence of structural heart disease. The hemodynamic and hormonal changes of pregnancy are likely responsible for the occurrence of new-onset PSVT and certainly for recurrence of underlying PSVT.4, 5, 6 However, in the setting of new-onset PSVT there are likely further predisposing factors in addition to the pregnancy-related changes given the overall low incidence of new-onset PSVT in the general pregnancy population. There may be asymptomatic PSVT present prior to pregnancy that is unmasked because of pregnancy-related changes. The new-onset PSVT group was similar to controls in terms of age and comorbidities; however, it did have increased obstetric risk factors that could be a precipitant. PSVT burden and response to nonpharmacologic interventions was similar regardless of whether women had a history of PSVT or presented with it for the first time in pregnancy. However, women with new-onset PSVT tended to go to the emergency department more often and hence underwent cardioversion, although this did not reach statistical significance. This increased medical seeking behaviour is to be expected given the patient concern and uncertainty around the new-onset presentation of PSVT in pregnancy. In contrast, women with a history of PSVT are provided education on how to recognize episodes and effectively manage them using nonpharmacologic and pharmacologic interventions, and as a result are unlikely to present to the emergency department as a first step.

Our data suggest that pre-pregnancy catheter ablation markedly reduces the risk of PSVT recurrence during pregnancy, with a recurrence rate of 15% among women who underwent the procedure compared with 93% in those who did not. These findings align with the cohort study by Bekiaridou et al.,⁹ which showed that women with a known history of PSVT who did not undergo ablation had a 10-fold higher risk of recurrence (odds ratio: 10.76, 95% confidence interval: 4.44-26.10, P < 0.0001). Although PSVT can generally be managed safely with medications during pregnancy, the Heart Rhythm Society (HRS) expert consensus recognizes catheter ablation prior to pregnancy as the preferred treatment for reducing recurrence in women with known PSVT.¹⁰ Our results emphasize the importance of pre-pregnancy counselling for women with PSVT, which should include an electrophysiology consultation for individualized management planning, particularly among those who have had episodes within 5 years of pregnancy.

Study limitations

This is a select population referred to a specialized Cardiac Obstetrics Clinic, so it may reflect a more symptomatic population requiring increased interventions. However, we were able to study those with a more recent vs remote history, making the results more generalizable to a “lower risk” population. Another limitation of our study is the potential for reporting bias, as PSVT episodes during pregnancy were either patient reported or confirmed by ECG during outpatient clinic visits, on outpatient Holter, or on presentation to the emergency department. Although there is a possibility of inaccuracies in self-reported symptoms that may have led to an overestimation of episode frequency in pregnancy, patient-reported episodes were reviewed and assessed by physicians during follow-up at the Cardiac Obstetrics Clinic to ensure complete documentation of PSVT burden during pregnancy.

Conclusion

This study in a Canadian Tertiary Cardiac Obstetrics Centre reveals important insights into PSVT presentation in pregnancy that informs pre-pregnancy counselling and expectant management in pregnancy. In particular, patients should be reassured that PSVT is generally well tolerated in pregnancy without major adverse cardiac, obstetric, and fetal or neonatal outcomes. However, a high rate of PSVT-related events, specifically emergency department visits and a requirement for chemical cardioversion and β-blocker use can be expected. As such, to minimize distress and disruptions in pregnancy, catheter ablation should be considered for definitive management prior to pregnancy, especially among women who have had pre-pregnancy PSVT close to an anticipated pregnancy. We emphasize the importance of regular antepartum follow-up, educating patients about signs and symptoms of PSVT, and timely management of PSVT episodes as integral components of care. Although the multidisciplinary care provided at our expert Cardiac Obstetrics Center may have contributed to the favourable outcomes observed, this study was not designed to establish causation. Nonetheless, in settings where such robust programmes may not exist, it is crucial to advocate for team-based approaches to ensure comprehensive peripartum care.