Epicardial Sinus Node Modification Using 5% Dextrose Insulation to Prevent Phrenic Nerve Injury: A Case Report

Sinus node modification for drug-refractory inappropriate sinus tachycardia (IST) is limited by the risk of phrenic nerve injury, particularly when the target substrate is located along the high right atrium and superior vena cava region. Various mechanical and electrical strategies have been proposed to mitigate this risk; however, effective insulation of the phrenic nerve during epicardial ablation remains challenging.

We report a patient with highly symptomatic, drug-refractory IST who underwent sinus node modification after failure of conventional endocardial ablation. Due to persistent phrenic nerve capture at the intended ablation sites, a percutaneous epicardial approach was undertaken. Injection of 5% dextrose in water (D5W) into the pericardial space was used as an electrically insulating medium to displace and protect the phrenic nerve, allowing effective epicardial radiofrequency delivery without phrenic nerve injury. Acute procedural success was achieved, with a significant reduction in sinus rate and symptomatic improvement during follow-up.

The post-procedural course was complicated by a localized pericardial effusion and dense pericardial adhesions observed during re-intervention. These findings were managed conservatively and are discussed as potentially related to procedural factors, including extensive epicardial ablation and local inflammatory response, rather than attributed to a single causative mechanism.

This case illustrates the feasibility of using D5W as an epicardial insulating medium to facilitate sinus node modification in close proximity to the phrenic nerve. While effective phrenic nerve protection was achieved, the occurrence of pericardial complications underscores the need for cautious patient selection, meticulous procedural technique, and further evaluation of safety strategies when employing non-physiologic insulating solutions in the epicardial space.