Anesthetic management of Wolff-Parkinson-White syndrome in a pregnant patient posted for emergency caesarean section.

The most common arrhythmia seen during pregnancy is paroxysmal supraventricular tachycardia and Wolff-Parkinson-White syndrome accounts for majority of this in such population. The presence of pre-disposing factors may facilitate the onset of tachyarrhythmias in previously asymptomatic parturients with the WPW syndrome such as increased hemodynamic, hormonal, autonomic, and emotional changes. Therefore, meticulous monitoring is essential perioperatively. Epidural anesthesia providing added advantage of hemodynamic stability and post-operative analgesia is preferred in such pregnant patients undergoing emergency cesarean section.

INTRODUCTION

In women of reproductive age, the most common arrhythmia is paroxysmal supraventricular tachycardia (PSVT).[1] Wolf-Parkinson-White (WPW) syndrome accounts for the majority of supraventricular tachycardia (SVT) in this population; with incidence of 1.2 per 1000 people.[2] SVT in pregnancy is defined as any tachyarrhythmia with a heart rate greater than 120 beats/min.[1] The diagnosis of WPW syndrome is made with a history and electrocardiographic (ECG), which shows shortened PR interval, delta waves (slurred upstroke of QRS complex) and widened QRS complex. The majority of patients with this syndrome remain asymptomatic throughout their lives. When symptoms do occur, they are usually secondary to tachyarrhythmias such as PSVT, atrial fibrillation, atrial flutter, and ventricular fibrillation that may lead to symptoms of palpitation, dizziness, short of breath, syncope or rare incidence of sudden death.

The exact incidence of WPW syndrome during pregnancy is not known; however, some reports have indicated that pregnancy may facilitate the onset of tachyarrhythmias in patients with previous asymptomatic pre-excitation.[34] The physiologic volume overload occurring during the pregnancy results in an increased left ventricular end diastolic volume that may lead to an increased myocardial irritability. Many case histories suggest a favorable outcome for mother and baby after an uncomplicated SVT.[5] However, changes in physiology of conduction and pre-disposition to complications induced by drugs and the techniques during emergency cesarean section, may lead to increased maternal and fetal risk, so it is important to know about WPW syndrome.

We are presenting a case of the pregnancy with WPW syndrome, posted for emergency lower segment caesarean section due to fetal distress.

CASE REPORT

A 30-year-old, primigravida with known WPW syndrome was referred to us for emergency caesarean section at 38 weeks of gestation. Nothing was significant except that few past uneventful syncopal attacks. Perioperative hemodynamic monitoring including ECG, non-invasive blood pressure, heart rate and Pulse oximetry was continuous, showing pre-operative systolic blood pressure in between 120 mmHg and 134 mmHg and diastolic blood pressure 78-82 mmHg and pulse rate in between 86 beats/min and 96 beats/min. Her physical examination, basic blood investigations, chest X-ray, and two dimensional echocardiography did not show any significant documented finding. ECG finding were suggestive of WPW syndrome [Figure 1]. The case was planned to be performed under combined spinal epidural anesthesia.

Figure 1

Shortening of P-R interval with slurred upstroke of initial segment of QRS complex (delta wave)

All anti-arrhythmic drugs and defibrillator was kept ready to deal with any untoward events. Preloading was carried out with 500 ml ringer lactate over 20 min. The 18 G epidural catheter was placed after proper localization of the epidural space with the loss of the resistance technique in between L3 and L4 intervertebral space. Subarachnoid block was given with 25 G BD Quincke spinal needle with 1.8 ml of 0.5% bupivacaine heavy in between L4 and L5 space. A sensory block up to T6 was achieved. She was kept in left lateral tilt of 15-20° to prevent supine hypotensive syndrome. 100% O2 by Hudson's mask was started at 6 L/min until the delivery of the baby. Only 5 units intravenous syntocinon was given slowly after delivery of baby and 15 units was given in 500 ml of Ringer lactate infusion. Variations in hemodynamic parameters were found within acceptable physiological range during the perioperative period.

Post-operative analgesia was planned at an interval of 5-6 h with 10 ml of 0.125% bupivacaine in divided doses over 15 min using the graded epidural anesthesia technique following 2 h of subarachnoid block to achieve a sensory level up to T8. The epidural catheter was left in situ for 72 h. Additional analgesia was provided with 75 mg diclofenac intramuscularly.

Her perioperative period remained uneventful in terms of blood loss, input/output, and adverse events. She was discharged on 4th post-operative day and remained asymptomatic during her follow-up.

DISCUSSION

The goal during perioperative management of anesthesia is to avoid any factor that increases sympathetic activity such as pain, anxiety, stress response of intubation, lighter plane of anesthesia, and hypovolemia[6] as mother and fetus both are at risk, if SVT develops. Gleicher et al. in a report of three pregnant patients, suggested that pregnancy may pre-dispose asymptomatic patients with pre-excitation to tachyarrhythmias.[3] Szekely and Snaith reported on six pregnant women in whom PSVT occurred only during the pregnancy.[7] Several hypothetical mechanisms have been invoked to explain the increased propensity for arrhythmias during the pregnancy. These include hemodynamic, autonomic, hormonal, and emotional changes related to pregnancy leading to increased plasma catecholamine concentrations and adrenergic receptor sensitivity, atrial stretch, and end diastolic volumes due to intravascular volume expansion.[8] Estrogen may alter the actomyocin-ATPase relationships in the myocardium and increase myocardium contractility.[3] Although there are no relevant studies on the effect of sex hormones on the cardiac tissue; however, studies said that estrogens increase the number of β-adrenergic receptors in the myocardium[9] and the α-adrenergic receptors in platelets.[10]

All commonly used anti-arrhythmic drugs cross the placenta and so have direct effects on the fetal well beings. Hence, pharmacological treatment is best reserved for those with hemodynamic changes, severe symptoms or sustained arrhythmias.[5] Non-pharmacological treatment including vagal maneuvers such as carotid massage, Valsalva maneuvre and facial immersion are well tolerated and aid in diagnosis. We did not give any medication to this patient because no cardiac arrhythmias were found on ECG during pregnancy. Regional anesthesia has a significant advantage over general anesthesia as multidrug administration, laryngoscopy stimulation, intubation and light planes leading to sympathetic stimulations are avoided. Epidural anesthesia is preferred to the spinal due to controlled and segmental block with better hemodynamic stability.[11] We preferred combined spinal epidural anesthesia for our patient because of reliable and profound block for prolonged duration with hemodynamic stability and post-operative pain management. Pre-loading and avoidance of aortocaval compression by using left lateral tilt help to prevent decreased atrial filling and thus, hypotension, reduces vasopressors requirement, which may trigger SVT in the WPW syndrome patient. Phenylephrine has been found to be effective in treatment of hypotension without causing an increase in the heart rate in such patients. We used only 1.8 ml of 0.5% bupivacaine (heavy) supplemented with the graded epidural blockade to provide added advantage of hemodynamic stability and post-operative analgesia and continued it for 72 h through the epidural catheter. Drugs used during cesarean section may also precipitate SVT, e.g. tocolytics and oxytocics. Our patient was given oxytocin in low dose only. Present recommendations are that oxytocin should only be given as a bolus of 5 units maximum and administered slowly or as an I.V. infusion especially, in the presence of cardiovascular compromise.[5]

PSVT, a common complication can be treated with vagal maneuvers or adenosine 6-12 mg IV or beta blockers (esmolol 50-300 μg/Kg/min IV). Adenosine is rapidly metabolized with an elimination half-life of less than 10 s, making it ideally suitable for use in pregnancy.[5] If adenosine fails, other anti-arrhythmic may be indicated and the risk of their use should be weighed against the risk of continuing SVT, e.g., β-blockers, verapamil. digoxin, amiodarone. Patients developing the atrial fibrillation with hemodynamic stability should be treated pharmacologically, whereas hemodynamically unstable patients should be treated by cardio version with 150-200 Joules.

CONCLUSION

Studies clearly documented an increased propensity for SVT in pregnant population with or without pre-excitation during the pregnancy, labor or cesarean section. Avoidance of certain drugs and precipitating factors along with meticulous monitoring is must perioperatively. Epidural anesthesia is preferred because of hemodynamic stability and post-operative analgesia. Although, further prospective studies are necessary to document increased arrhythmias susceptibility during the pregnancy, the magnitude of problems, mechanisms, and preferred therapeutic approach in these patients.