Anaesthetic management of a patient with Fontan physiology for electrophysiology study and catheter ablation

Abstract

The success of the Fontan procedure for congenital single ventricle anatomy has resulted in adult patients with Fontan physiology requiring anaesthesia for cardiac and non-cardiac procedures. We present the perioperative management of a patient with Fontan physiology who underwent electrophysiological study with radiofrequency ablation for atrial tachycardia under general anaesthesia. Good communication between the multidisciplinary teams, a detailed understanding of the patient’s complex cardiac anatomy and physiology, as well as the ability to recognise and manage perioperative complications all play a vital role for a successful outcome.

Background

The Fontan procedure effectively diverts systemic venous return to the pulmonary artery without a pump in patients with a functional or anatomic single ventricle such as hypoplastic left heart syndrome, tricuspid atresia, pulmonary atresia and double inlet ventricle.¹ Revolution in Fontan surgical techniques and medical management of congenital heart disease over the last few decades have resulted in an expanding population of patients with unique cardiac physiology surviving to adulthood,^{2 3} with the adult survivors developing various late complications such as thromboembolic events, ventricular dysfunction, arrhythmias, formation of shunts and hepatic dysfunction.⁴ In particular, the occurrence of symptomatic arrhythmias causes significant morbidity in these patients and is potentially reversible.^5–7 Electrophysiological study (EPS) and catheter ablation have proven to be effective in managing these arrhythmias in adult Fontan patients refractory to medical management.^{8 9} Furthermore, advances in mapping techniques for localisation of the foci of arrhythmias have led to an increased success rate, overcoming difficulties due to complex Fontan anatomy.^{10 11} With increasing use of electrophysiology and catheter ablation techniques, anaesthesiologists must be prepared to manage patients with potentially challenging cardiac physiology outside the confines of the operating theatre. Anaesthetic concerns for these scenarios are multi-fold; including knowledge about the patient’s underlying cardiac anatomy and physiology, familiarity with the complications of Fontan physiology and EPS procedures as well as meticulous planning for anaesthesia in a remote location.

Here, the authors present a case of a patient with Fontan physiology undergoing EPS and catheter ablation in the cardiac catheterisation lab (CCL), and outline the approach to perioperative cardiac assessment, stabilisation and anaesthetic management in the remote location.

Case presentation

A male patient (71 kg) aged 34 years with dextrocardia, situs inversus, complete atrioventricular septal defect (AVSD) and Tetralogy of Fallot (TOF) had underwent a right Blalock-Taussig (BT) shunt procedure at the age of 4 years. A modified Fontan’s procedure with BT shunt ligation, anastomosis between the right and left superior vena cava (SVC) to the respective pulmonary arteries, complex intra-atrial baffle creation with fenestration and division of the main pulmonary artery was performed when he was aged 12 years (figure 1). Subsequently, an Amplatzer device closure of atrial baffle fenestration was done 10 years later. At the age of 30, he developed intermittent palpitations with chest discomfort that was increasing in frequency, occurring a few times a month despite being on bisoprolol and digoxin. Holter report showed atrial tachycardia (AT), and he was planned to undergo EPS and catheter ablation. Functionally, he was independent in his activities of daily living and able to tolerate physical activities up to four metabolic equivalents.

Figure 1.

Illustration of patient’s cardiac anatomy. Dextrocardia with tetralogy of fallot post-lateral tunnel. The left ventricle is on the right and posterior and the hypoplastic right ventricle is anterior to the left ventricle. Two superior vena cavas connect to right pulmonary artery and left pulmonary artery (LPA) and the left-sided inferior vena cava through the lateral tunnel to the LPA.

On preoperative assessment, he was noted to have digital clubbing. His resting blood pressure was 127/79 mm Hg with a heart rate of 77 beats per minute and oxygen saturation of 95% on room air. He had a grade 2 systolic murmur and the rest of the systemic examination was unremarkable.

His medication regimen consisted of digoxin, losartan, metoprolol and warfarin. Warfarin was discontinued for 5 days prior to the procedure and coagulation studies were within normal limits. He had a haemoglobin level of 180 g/L, otherwise, the rest of his preoperative blood investigations were unremarkable. ECG showed sinus rhythm. A 2D-echo was performed a day before the procedure, which showed dextrocardia with complete AVSD, a common atrium with large septal defect with bi-directional shunting, large ventricular septal defect with hypoplastic right ventricle, a single atrioventricular valve with mild-moderate regurgitation, normal left ventricular cavity size with ejection fraction of 53%, and a patent Fontan connection. Previous documented cardiac catheterization 5 years prior showed that his mean Fontan pressure was 14 mm Hg with a small shunt demonstrated from the Fontan tunnel to the right atrium with shunt fraction of 1.09. A multidisciplinary team meeting (which included his adult congenital heart disease specialist, EPS proceduralist, the cardiac catheter lab staff and the anaesthesiology team) was conducted the day before, to discuss the potential procedural complications, invasive monitoring and drugs required as well as set up of the CCL.

On the day of the procedure, the anaesthetic team and cardiac lab staff prepared the cardiac lab for general anaesthesia (GA). In addition to extending the ventilator circuit and placing the monitoring devices in an ergonomic fashion, infusion pumps consisting of epinephrine, norepinephrine, glyceryl trinitrate and milrinone were prepared and the lines extended. An 18G peripheral intravenous cannula was secured. Infective endocarditis prophylaxis was initiated with intravenous vancomycin infusion as he was allergic to cloxacillin. Monitoring was established with a five-lead ECG, non-invasive blood pressure monitoring and pulse oximetry. In addition, external defibrillation pads were placed and connected to a biphasic external defibrillator. A 20G radial arterial line and right internal jugular quad-lumen 7 French gauge central venous line (CVL) were placed under local anaesthesia with ultrasound guidance. The CVL was transduced which allowed monitoring of his pulmonary arterial pressure (PAP), of which baseline reading was 19 mm Hg.

GA was induced with midazolam 1 mg, fentanyl 75 mcg and etomidate 10 mg. Laryngoscopy was facilitated with Rocuronium 70 mg and the airway was safely secured with a size 8.0 endotracheal tube. Capnography and temperature monitoring were instituted. A trans-oesophageal echocardiography (TOE) probe was inserted to assist with monitoring of cardiac function intraoperatively and a comprehensive TOE study was performed by his cardiologist which revealed a grade 3 right to left shunt. The shunt originated from a small gap seen on the lateral Fontan, inferior to the closure device. GA was maintained with sevoflurane 1.2%–1.4% in 50% oxygen: 50% air combination with remifentanil infusion 0.03–0.08 mcg/kg/min. The patient was ventilated with tidal volumes of 6 mL/kg with a respiratory rate of 12 without any application of positive end-expiratory pressure (PEEP). His end-tidal carbon dioxide was maintained within the range of 30–35 mm Hg. Intravenous heparin was given to maintain an activated clotting time between 250 and 350 s. During the procedure, it was found that the patient had AT of at least three different foci. During arrhythmia induction, there were transient episodes of hypotension associated with rise in PAP to 22 mmHg which were supported with milrinone and norepinephrine infusion. Two foci of AT were successfully ablated and while the proceduralist was trying to ablate the third focus, the patient developed severe tachycardia (HR 200/minute) with hypotension (SBP 82 mm Hg), desaturation and a sharp rise in pulmonary artery pressures from 16 to 29 mm Hg. Intermittent boluses of 10 mg esmolol were given to reduce heart rate, while cardiologists proceeded to assess with TEE, which showed increased right to left shunting during AT across the lateral Fontan. The decision was made to stop the procedure due to haemodynamic instability. Subsequently, the patient’s blood pressure, PAP and saturations improved to his baseline values with the return of sinus rhythm. Norepinephrine and milrinone infusions were discontinued.

Total amount of intravenous Hartmann’s solution given was 500 mL, and the patient also received 1 L of normal saline. Frusemide 30 mg was given in divided doses and total urine output was 400 mL. IV Ondansetron 4 mg was given to avoid post-operative nausea and vomiting. Reversal of paralysis was achieved with sugammadex 2 mg/kg and the patient was extubated awake. He was transferred to the cardiology intensive care unit for monitoring. Telemetry post procedure showed no arrhythmias and warfarin was restarted. He was then transferred to general ward on post procedure day two and was discharged on post procedure day 4.

Outcome and follow-up

Ability to recognise and manage perioperative complications played a vital role for a successful outcome of this patient. Patient did not have any AT at 3 month follow-up.

Discussion

Pathophysiology

Individuals with Fontan physiology often have residual cardiac lesions that promote electrical disturbances and abnormal haemodynamics. Arrhythmias can occur in up to 45% of these patients, and the incidence increases with time from surgical repair.^{7 12} Electrical abnormalities often develop due to surgical scarring across suture lines, damage/fibrosis of the conduction system and chronic pressure overloading of the right atrium leading to dilatation and remodelling.¹³ Atrial tachyarrhythmia, such as intra-atrial re-entry tachycardia, is the most common arrhythmia in Fontan circulation and is associated with impaired quality of life, thromboembolism, deterioration of cardiac function and sudden death. These arrhythmias are often difficult to control, with variable response to antiarrhythmic therapy and may require repeated cardioversion or surgical intervention.¹⁴ Catheter ablation has emerged as a potential treatment option, either as first-line or as an adjunct to pharmacological agents.¹⁵

In the Fontan circulation, blood flow from the systemic venous circulation through the lungs is entirely passive. The main driving force of pulmonary blood flow and hence the cardiac output is dependent on an adequate transpulmonary gradient, which is the pressure difference between the central venous pressure (CVP) and the pulmonary venous atrial pressure (or common atrial pressure). The systemic venous pressure of an ideal Fontan circulation is approximately 10–15 mm Hg and the pulmonary venous atrial pressure is approximately 5–10 mm Hg; this allows a trans pulmonary gradient driving pressure of 5–8 mm Hg.¹⁶ An adequate transpulmonary gradient is dependent on adequate systemic venous pressure (ie, preload), low pulmonary vascular resistance (PVR), good atrioventricular valve function, sinus rhythm and a well-functioning ventricle.¹²

Anaesthetic considerations

Preoperative assessment of the Fontan patient

During preoperative evaluation, it is important to consider the congenital pathology and degree of palliation completed at the time of assessment. A detailed medical history and physical examination should be conducted, with focus on the patient’s functional capacity, recent changes in health status, long-term complications of Fontan physiology and current medications. Baseline haematological and biochemical investigations should be performed. A 12-lead ECG and echocardiography allow assessment of rhythm, ventricular and valvular function, PVR and ventricular end-diastolic pressure. Review of other prior cardiac investigations such as cardiac MRI, CCL or a Holter study is useful for assessment of the patient’s cardiac anatomy and function. End-organ complications to look out for include heart failure, protein-losing enteropathy, renal impairment and hepatic dysfunction.^{12 17}Patients with Fontan physiology are also at increased risk of thromboembolism due to low flow states, arrhythmias and hypercoagulability.¹⁸ Bridging therapy should be considered for patients who are on warfarin, if the thromboembolic risk is higher than the bleeding risk.¹⁹ Perioperative antibiotic prophylaxis is indicated in procedures likely to produce bacteraemia.¹²

Cardiac catheter laboratory environment

Anaesthesiologists should familiarise themselves with their institution’s CCL. Bulky EPS equipment and subdued lighting, in addition to compromised access to the patient, are among some of the issues with planning the set-up and position of the ventilator, monitoring devices and drug infusion pumps in an ergonomic fashion. The ventilator circuit and infusion pump lines may need to be extended depending on the size of the room and distance away from the patient. To prevent errors in drug delivery, connections need to be checked to avoid leakage. As radiation is required, staff need to take appropriate precautions and protection. The non-tipping CCL table may be an issue during the induction of anaesthesia. Patients at risk of aspiration should be induced on a tipping trolley and then transferred onto the CCL table after the airway is secured. As the CCL is often in an isolated environment away from skilled anaesthetic help, it is important that a senior anaesthesiologist with appropriately trained assistance is present. Care should also be taken in the positioning of the patient, as some techniques may require arms above the head to facilitate lateral imaging.

Anaesthetic considerations specific to EPS procedures

EPS involve the placement of multiple diagnostic catheters within the cardiac chambers to define the origin and pathway of arrhythmias, in order to determine therapeutic options. Ablation catheters are then guided to the correct position for ablation and used to assess the success of treatment.²⁰ Arrhythmias have to be reproduced under controlled conditions using timed electrical impulses. The choice of anaesthetic technique, monitored anaesthesia care (MAC) or GA, should be made on the basis of the patient’s risk factors, complexity of the ablation procedure and expected duration. Although MAC anaesthesia is used most frequently, GA may be preferable in patients with significant comorbid conditions or in prolonged complex cases such as those requiring transseptal access or the arrhythmia is due to a scar tissue. The other advantages of GA in this patient population are (1) it provides a better procedural success and a decreased incidence of pulmonary vein reconnection seen on subsequent ablations,²¹ (2) it provides more control and stability over physiological parameters, (3) patients are able to tolerate the procedure better with the invasive monitoring such as TOE (4) ablation demands absolute immobility as movement can result in catheter dislodgement and damage to normal conduction tissue.²²

Anaesthetic agents with the least effects on myocardial contractility, cardiac output and pulmonary blood flow should be chosen. Induction of anaesthesia should be performed with short-acting intravenous agents such as propofol. Propofol has no direct effect on SA node function, AV node conduction, or accessory pathway conduction.²³ Etomidate is a suitable alternative in patients with cardiac comorbidities as it has a negligible effect on myocardial contractility. Volatile anaesthetics have been hypothesised to suppress arrhythmia inducibility, especially in supraventricular tachycardia.¹⁵ A low concentration of an inhalational agent in combination with an infusion of a short-acting opioid such as remifentanil ensures cardio-stability with adequate analgesia without much effect on arrhythmia induction. Remifentanil infusion can also assist with providing conditions suitable to prevent movement and coughing.

Positive pressure ventilation with increased intrathoracic pressures not only reduces the passive pulmonary flow and the cardiac output but also causes fluctuations in atrial pressure and volume, which can dislodge the ablation catheter. When using positive-pressure ventilation, a ventilator strategy of lower mean airway pressure, moderate alkalosis (pH=7.45, PCO₂=35 mm Hg), tidal volumes of 5–6 mL/kg, short inspiratory times and low PEEP usually allow adequate pulmonary blood flow with minimal haemodynamic effects.²⁴ Choosing a spontaneous breathing mode may facilitate passive pulmonary flow and improves the cardiac output in Fontan patients.

In addition, arrhythmia induction for the purpose of focus identification can severely affect cardiac output. Resuscitation and supportive cardiac drugs should be prepared prior to induction of anaesthesia. Intravenous inodilators such as milrinone are well suited for the Fontan patient due to their lusitropic and pulmonary vasodilatory properties, helping to improve ventricular compliance without raising CVP.²⁴ Vigilance is necessary to watch out for potential complications of catheter ablation, which include cardiac tamponade, pericardial effusion, thromboembolism, complete atrioventricular block and atrio-oesophageal fistula.^{20 22}

Prior to the procedure, active discussion between the anaesthesiologists and electrophysiology specialist is pertinent to ascertain the type of ablation technique performed, if there are special requirements involved, as well as the anticipated duration and complexity of the procedure.

Monitoring and invasive lines

In addition to the standard American Society of Anaesthesiologists monitoring, intra-arterial blood pressure monitoring is essential in Fontan patients due to unpredictable changes in blood pressure, especially during arrhythmia induction and ablation. A CVL may also be useful, and it should be noted that in Fontan patients, the CVP is a reflection of the mean PAP and not ventricular preload.²⁴ Care should also be taken during the placement of the central line, as every patient’s surgical repair may be different. Our patient also had two SVCs, both of which were anastomosed to the respective pulmonary artery. TOE can be used for intraoperative assessment of ventricular preload, function and to monitor for episodes of emboli. Extensive application of ECG electrodes and patches are required for mapping, ablation and defibrillation and these should be positioned strategically to avoid interference.²⁰ Before administering intravenous fluids or medications, lines should be de-aired to prevent systemic air embolism, especially in the presence of fenestrations or residual shunts. Resuscitation equipment and drugs should be prepared beforehand.

Haemodynamic management of Fontan patients

Maintaining an optimal transpulmonary gradient to achieve adequate pulmonary blood flow and hence cardiac output is key in the anaesthetic management of Fontan patients.^{16 24} Hypovolaemia is poorly tolerated, hence prolonged fasting should be minimised and fluid administration should be guided by CVP or TOE.²⁴ Factors that precipitate an increase in PVR such as hypoxia, hypercarbia, acidosis, hypothermia and increased intrathoracic pressures should be actively avoided.²⁵ Both over distension of alveoli with excessive mean airway pressure and reduced lung volumes due to atelectasis can result in increases in PVR. Choosing a spontaneous breathing mode may facilitate passive pulmonary flow and improves the cardiac output.

Postoperative care

Smooth extubation and analgesia are important to avoid groin haematoma after removal of catheters. Access sites should be monitored for signs of bleeding.²⁰ Trained recovery staff and appropriate monitoring are mandatory after catheter ablation in Fontan patients. The patient should be transferred to a monitored cardiology unit (either the high dependency or intensive care unit depending on haemodynamic stability), and monitoring of oxygen saturation, telemetry and blood pressure should be performed in all patients at least for 24 hours after the procedure. Inspired oxygen concentration should be adjusted to maintain saturation at preoperative levels. Thromboprophylaxis should be continued throughout the perioperative period, and anticoagulants should be restarted when appropriate.²⁶

Learning points.

• Advancements in percutaneous interventions have led to a larger population of adults with complex cardiac physiology presenting for treatment.

• Familiarity with the electrophysiological study lab set-up and the peri-procedural complications is crucial to providing safe anaesthesia.

• Good communication among the various members of the healthcare team and prior contingency planning is also paramount in management.