Pre-excitation syndrome is a collective term that refers to premature ventricular activation through accessory or anomalous conduction pathways. 1,7WPW, a classic subtype of pre-excitation, is characterized by the presence of a short PR interval and a broad QRS with a delta wave on ECG, whereas the LGL subtype only shows a short PR interval and a normal QRS complex on ECG.8,9 Ventricular pre-excitation can predispose pregnant women to re-entry arrhythmias, with clinical manifestations of pre-excitation, paroxysmal tachycardia, and related symptoms, including palpitations, dizziness, and/or syncope.3,8,9
In large-scale general population studies involving children and adults, the prevalence of WPW is estimated as 1–3 per 1000, and the incidence of WPW among first-degree relatives is 5.5 per 1000.9 Approximately 65% of adolescents and 40% of individuals > 30 years old with a WPW pattern on resting ECG have no symptoms.10 Consequently, it is difficult to identify asymptomatic patients with pre-excitation syndromes. In this study, 75.1% of patients were diagnosed with pre-excitation syndrome by ECG examination in the second or third trimester of pregnancy, and most of them had no symptoms.
However, the increase in blood volume and changes in hormone levels predispose pregnant women with pre-excitation syndrome to SVT, leading to an increased risk of adverse events.3,6 The treatment of serious arrhythmia caused by pre-excitation syndrome during pregnancy is more difficult compared to that in nonpregnancy, and there is currently no clear treatment specification. At present, vagal maneuvers and intravenous injection of adenosine are recommended as Class I therapies for managing SVT.10 If the patient with pre-excitation is unwilling to undergo ablation, medications such as flecainide and propafenone can be used as Class IIA recommendations (in the absence of structural heart disease). If the patient is hemodynamically unstable, synchronous cardioversion is recommended. Nevertheless, none of these effective treatments can be used in pregnancy owing to the risk of fetal exposure to ionizing radiation and fetal arrhythmia.11,12 Due to limited treatment options, the management of SVT during pregnancy remains a thorny clinical challenge.11 In this study, none of the recruited cases with SVT received RFCA during pregnancy. Cardiologists suggest that these patients should undergo RFCA after delivery, especially those who wish to have another child. Accordingly, we focused on 29 patients who experienced two pregnancies during our study period. Among them, five patients received RFCA after the first delivery and obtained better outcomes in the second pregnancy. However, RFCA was performed in only five patients, which is insufficient to draw conclusions. Future research with a larger sample size is required to further explore these hypotheses.
We found that a history of SVT before pregnancy, cardiac function, and heart organic abnormalities was related to the occurrence of SVT during pregnancy. Although only 24.9% of all patients were diagnosed with pre-excitation syndrome before pregnancy or in the previous pregnancy, 51.6% of them experienced SVT during pregnancy. We speculate that this may be related to imprecise or no treatment in these cases (11 of them received RFCA before pregnancy) even if some had previously experienced recurrent SVT. Additionally, RFCA as an effective treatment for pre-excitation syndrome has a certain failure rate. Indeed, it has been reported that the success rate of the first RFCA is 91.2%, while that of the second ablation is 80%.13 In this study, one patient underwent two RFCA procedures, but SVT occurred again during pregnancy. Overall, 95.5% of patients had a cardiac function grade of I–II, and few patients developed serious cardiac complications. All patients with left ventricular systolic dysfunction and most patients with a cardiac function grade of III–IV during pregnancy were from the SVT group.
A recent study reported that a young patient with WPW syndrome and postpartum cardiomyopathy (PPCM) developed symptomatic arrhythmias (tachycardia), suggesting that WPW syndrome is a pre-excitation/accessory pathway-induced arrhythmia related to pregnancy and can occur along with PPCM.14 Among all patients included in this study, one patient with hypertrophic cardiomyopathy developed SVT in the third trimester and was transferred to the ICU after cesarean section.
Previous literature has shown that patients with pre-excitation abnormalities are at a high risk of life-threatening perioperative arrhythmias.2,15 SVT can present at any stage of pregnancy, including labor. The etiology of SVT during labor is multifactorial. Increased cardiac output stretches the myocardial tissues, predisposing pregnant women to tachyarrhythmia. Moreover, catecholamine release, electrolyte disturbances such as hyperkalemia during labor, and vasopressors administered to treat post-epidural hypotension are other common triggers of SVT during labor.15,16 Based on this, cesarean delivery may be relatively safe for patients with pre-excitation syndrome, especially those with a history of SVT, because of the higher catecholamine release during vaginal delivery.17,18 However, anesthesiologists believe that spinal anesthesia during cesarean section can result in a series of blood pressure changes. It is difficult to maintain blood pressure within the reference range in the absence of vasopressors, but vasopressors may prompt the onset of SVT. Therefore, the delivery mode for pregnant women with pre-excitation syndrome is challenging. We believe that the delivery mode for patients with SVT history should be determined prudently, but SVT is not an absolute indication of cesarean section. Multidisciplinary team assessments are necessary to achieve the best benefits for both mothers and neonates, and vaginal delivery is also possible while ensuring the safety of mothers and neonates.18 In our study, 30.42% of patients with vaginal delivery or assisted vaginal delivery achieved good outcomes.
Some obstetric complications were observed, including GDM, PROM, SGA, pre-eclampsia, and fetal distress. Five patients with critical perinatal conditions were transferred to the ICU, and no cases of maternal death occurred. All patients complicated with heart disease were managed conservatively by a multidisciplinary team. Most mothers and newborns had good outcomes, except for four fetuses that died in the second and third trimesters. However, given the recognized familial clustering of many SVT etiologies,9 the potential for fetal SVT should also be expected, and it is important to pay more attention to its associated complications, including in utero heart failure and death.
As mentioned above, pregnant women are prone to develop new-onset or recurrent arrhythmias as a result of physiological changes during pregnancy. Pregnancy creates an arrhythmogenic environment, leading to an increased risk of arrhythmia in the pregnant population.19 Our results showed that pregnant women with GDM (glucose intolerance diagnosed during pregnancy) were more likely to experience SVT during pregnancy. Previous literature has reported that the deterioration of the cardiac autonomic nervous system in patients with diabetes is associated with an increase in cardiac and arrhythmogenic mortality.20 Emerging evidence has also demonstrated that diabetes affects the electrical conduction system of the heart, culminating in lethal arrhythmia and sudden cardiac death. Hypoglycemia, hyperglycemia, and glucose fluctuations can induce arrhythmia by activating various pathways21,22. Therefore, more attention should be paid to the relationship between diabetes and arrhythmia.
The limitations of our work as follow: this is a retrospective analysis so we were limited to know more information about the subtypes of preexcitation syndrome and the metabolic diseases other than diabetes. In addition, we did not clear whether pregnancy itself is a factor that promotes preexcitation, or whether these patients suffered from concealed preexcitation syndrome before pregnancy that have not been found by us. So we need more perfect pre-pregnancy examination program which should include cardiac ultrasound and electrocardiogram. We believe that the suggestions or assistance from cardiologists and anesthesiologists should be more considered in future studies, which can make us considering more plan about the mode of delivery and individual treatment of preexcitation syndrome during pregnancy.
Despite the limitations, the strength of the study is that this study determined the correlation between supraventricular tachycardia and adverse maternal and fetal outcomes in patients with preexcitation syndrome, and fouded the risk factors leading to supraventricular tachycardia during pregnancy.