Combined Epicardial-Endocardial Approach to Ablation of Inappropriate Sinus Tachycardia

Sinus Tachycardia: a Multidisciplinary Expert Focused Review

Sinus tachycardia (ST) is ubiquitous, but its presence outside of normal physiological triggers in otherwise healthy individuals remains a commonly encountered phenomenon in medical practice. In many cases, ST can be readily explained by a current medical condition that precipitates an increase in the sinus rate, but ST at rest without physiological triggers may also represent a spectrum of normal. In other cases, ST may not have an easily explainable cause but may represent serious underlying pathology and can be associated with intolerable symptoms. The classification of ST, consideration of possible etiologies, as well as the decisions of when and how to intervene can be difficult. ST can be classified as secondary to a specific, usually treatable, medical condition (eg, pulmonary embolism, anemia, infection, or hyperthyroidism) or be related to several incompletely defined conditions (eg, inappropriate ST, postural tachycardia syndrome, mast cell disorder, or post-COVID syndrome). While cardiologists and cardiac electrophysiologists often evaluate patients with symptoms associated with persistent or paroxysmal ST, an optimal approach remains uncertain. Due to the many possible conditions associated with ST, and an overlap in medical specialists who see these patients, the inclusion of experts in different fields is essential for a more comprehensive understanding. This article is unique in that it was composed by international experts in Neurology, Psychology, Autonomic Medicine, Allergy and Immunology, Exercise Physiology, Pulmonology and Critical Care Medicine, Endocrinology, Cardiology, and Cardiac Electrophysiology in the hope that it will facilitate a more complete understanding and thereby result in the better care of patients with ST.

Novel SuperMap feature of dipole charge density mapping technique offers advantages for redo catheter ablation in highly symptomatic patients with inappropriate sinus tachycardia: A case series

Ablation procedures using classical sequential mapping systems may fail to eliminate IAST. The AcQMap dipole charge density mapping technique may offer improved accuracy and has a potential added value for the ultimate success of eliminating IAST. The use of the AcQMap should be considered for redo, as well as first line therapy for patients with symptomatic IAST.

Epicardial Ablation of Supraventricular Tachycardias

Supraventricular arrhythmias are the most common cardiac arrhythmias encountered; however, it is uncommon that supraventricular tachycardias require percutaneous epicardial access for successful mapping and ablation. There are particular scenarios where epicardial access and ablation should be considered. Certain accessory pathways particularly in the posteroseptal region may require epicardial access for successful ablation. These pathways may also be approached from within the coronary sinus system. In addition, tachycardias near the phrenic nerve in the right atrium or left atrium may require epicardial access for successful ablation or to allow displacement of the phrenic nerve facilitating safe catheter ablation.

Patient Selection for Epicardial Ablation-Part I: The Role of Epicardial Ablation in Various Cardiac Disease States

Epicardial catheter ablation is most commonly performed following unsuccessful endocardial ablation. Given the frequency of epicardial substrates in certain cardiomyopathic disease states, however, a combined endocardial–epicardial approach should be considered as a primary treatment strategy. Although epicardial ablation is primarily deployed in patients with ventricular arrhythmias, the role of epicardial approaches in supraventricular tachycardias (eg, atrial fibrillation, inappropriate sinus tachycardia, and—rarely—accessory pathways) is growing, with continued advances being made.

Catheter ablation of inappropriate sinus tachycardia

Catheter ablation for inappropriate sinus tachycardia (IST) is recommended for patients symptomatic for palpitations and refractory to other treatments. The current approach consists in sinus node modification (SNM), achieved by ablation of the cranial part of the sinus node to eliminate faster sinus rates while trying to preserve chronotropic competence. This approach has a limited efficacy, with a very modest long-term clinical success. To overcome this, proper patient selection is crucial and an epicardial approach should always be considered. This brief review will discuss the current role and limitations of catheter ablation in the management of patients with IST.

The Emerging Role of Epicardial Ablation

Sosa and colleagues first described a percutaneous approach (via the subxiphoid area) to access the pericardial space in 1996. Epicardial mapping and ablation is increasingly used for the treatment of supraventricular and ventricular arrhythmias and represents an adjunctive approach for challenging arrhythmias to improve procedural success rates. Epicardial ablation should be considered not only after the failure of an endocardial ablation but often as a first-line approach. Complications may occur during percutaneous access and epicardial ablation, and these might be reduced or avoided by improved operator skills and experience. New tools to access the epicardial space are being evaluated.

Epicardial Ablation of Supraventricular Tachycardia

Epicardial catheter-based mapping and ablation of a variety of supraventricular tachycardias is feasible, safe, and effective. Supraventricular tachycardia substrates are not uncommonly epicardial, and approaches with percutaneous epicardial instrumentation or via the epicardial venous structures, such as the coronary sinus, are becoming more widely accepted. These techniques are an important treatment option as an alternative to a more invasive surgical approach or to allowing patients to suffer from an ongoing arrhythmia. New technologies and innovative techniques are being developed that hold great potential to improve the efficacy and safety of the epicardial catheter-based approach to these challenging arrhythmias.

A novel method for sinus node modification and phrenic nerve protection in resistant cases

This is a case report of inappropriate sinus tachycardia in a patient who had a previous unsuccessful endocardial ablation, which had been limited due to concerns of phrenic nerve injury. The patient required a repeat ablation that utilized a novel combined epicardial and endocardial approach for sinus node modification and simultaneous protection of the phrenic nerve via an epicardial balloon.

Caring for women undergoing cardiac ablation

Radiofrequency cardiac ablation (RFCA) has become the treatment of choice for many cardiac arrhythmias that have not responded to medication. Complications of cardiac ablation include bleeding, thrombosis, pericardial tamponade, and stroke. Many complications are procedure specific, and several complications can be avoided with appropriate nursing care. Quality patient outcomes begin with competent nursing care. Therefore it is vital for a patient undergoing a percutaneous cardiac ablation procedure to receive supportive care and pre- and post-interventional patient education. This article discusses the nursing care of women undergoing RFCA.

Partial Cardiac Denervation and Sinus Node Modification for Inappropriate Sinus Tachycardia

We describe a case of inappropriate sinus tachycardia refractory to medical therapy and catheter sinus node ablation, which was successfully treated by surgery with approaches on both the sinus node and cardiac autonomic ganglia.

Use of Noncontact Mapping and Saline-Cooled Ablation Catheter for Sinus Node Modification in Medically Refractory Inappropriate Sinus Tachycardia

BACKGROUND

Inappropriate sinus tachycardia (IST) is characterized by heart rate (HR) increase out of proportion to stress level. Radiofrequency (RF) modification of the sinus node (SN) is an accepted treatment modality for medically refractory IST. We describe a new technique using noncontact mapping and a saline irrigated catheter for SN modification.

METHODS

Seven consecutive patients with medically refractory IST were referred for ablation. Intrinsic heart rate (IHR) was calculated with complete autonomic blockade by atropine and propranolol. Isoproterenol (ISO) 1 mcg/min was initiated and increased to 10 mcg/min. Site of earliest activation was tagged at each dose of ISO once stable HR was achieved. RF ablation to target site of earliest activation at peak HR on ISO 10 mcg/min was performed. With any change in P-wave morphology, activation was reassessed and the new site of earliest activation targeted. Endpoint was a decrease in HR and change in P-wave morphology in lead III and aVF.

RESULTS

Five of seven patients had abnormal IHR. Mean number of RF lesions was 25 (10-52). All patients had either flattening of the P wave or development of negative P waves in leads III and aVF post RF associated with a decrease in HR of > or = 25% from baseline off ISO. A caudal shift of the site of early activation compared with baseline was observed. One patient who had a prior SN modification developed symptomatic intermittent junctional bradycardia and required an atrial pacemaker 2 weeks later. The other 6 patients in follow-up from 6 to 24 months had no further IST.

CONCLUSIONS

Noncontact mapping using the described technique in conjunction with the saline-cooled ablation catheter for SN modification in the treatment of IST may provide effective HR control.

Right diaphragmatic paralysis following endocardial cryothermal ablation of inappropriate sinus tachycardia

Inappropriate sinus tachycardia (IST) is a rare disorder amenable to catheter ablation when refractory to medical therapy. Radiofrequency (RF) catheter modification/ablation of the sinus node (SN) is the usual approach, although it can be complicated by right phrenic nerve paralysis. We describe a patient with IST, who had symptomatic recurrences despite previous acutely successful RF SN modifications, including the use of electroanatomical mapping/navigation system. We decided to try transvenous cryothermal modification of the SN. We used 2 min applications at -85 degrees C at sites of the earliest atrial activation guided by activation mapping during isoprenaline infusion. Every application was preceded by high output stimulation to reveal phrenic nerve proximity. During the last application, heart rate slowly and persistently fell below 85 bpm despite isoprenaline infusion, but right diaphragmatic paralysis developed. At 6 months follow-up, the patient was asymptomatic and the diaphragmatic paralysis had partially resolved. This is the first report, we believe, of successful SN modification for IST by endocardial cryoablation, although this case also demonstrates the considerable risk of right phrenic nerve paralysis even with this ablation energy.

How close are the phrenic nerves to cardiac structures? Implications for cardiac interventionalists

BACKGROUND

Phrenic nerve injury is a recognized complication following cardiac intervention or surgery. With increasing use of transcatheter procedures to treat drug-refractory arrhythmias, clarification of the spatial relationships between the phrenic nerves and important cardiac structures is essential to reduce risks.

METHODS AND RESULTS

We examined by gross dissection the courses of the right and left phrenic nerves in 19 cadavers. Measurements were made of the minimal and maximal distances of the nerves to the superior caval vein, superior cavoatrial junction, right pulmonary veins, and coronary veins. Histologic studies were carried out on tissues from six cavaders. Tracing the course of the right phrenic nerve revealed its close proximity to the superior caval vein (minimum 0.3 +/- 0.5 mm) and the right superior pulmonary vein (minimum 2.1 +/- 0.4 mm). The anterior wall of the right superior pulmonary vein was <2 mm from the right phrenic nerve in 32% of specimens. The left phrenic nerve passed over the obtuse cardiac margin and the left obtuse marginal vein and artery in 79% of specimens. In the remaining specimens, its course was anterosuperior, passing over the main stem of the left coronary artery or the anterior descending artery and great cardiac vein.

CONCLUSIONS

The right phrenic nerve is at risk when ablations are carried out in the superior caval vein and the right superior pulmonary vein. The left phrenic nerve is vulnerable during lead implantation into the great cardiac and left obtuse marginal veins.