Mapping for Acute Transvenous Phrenic Nerve Stimulation Study (MAPS Study)

Central sleep apnea syndrome, correlated with the occurrence of heart failure, is characterized by periods of insufficient ventilation during sleep. This acute study in 15 patients aims to map the venous system and determine if diaphragmatic movement can be achieved by phrenic nerve stimulation at various locations within the venous system.

Subjects underwent a scheduled catheter ablation procedure. During the procedural waiting time, one multielectrode electrophysiology catheter was subsequently placed at the superior and inferior vena cava and the junctions of the left jugular and left brachiocephalic vein and right jugular and right brachiocephalic vein, for phrenic nerve stimulation (1-2 seconds ON/2-3 seconds OFF, 40 Hz, pulse width 210 μs). Diaphragmatic movement was assessed manually and by a breathing mask. During a follow-up assessment between 2 and 4 weeks postprocedure, occurrence of adverse events was assessed.

In all patients diaphragmatic movement was induced at one or more locations using a median threshold of at least 2 V and maximally 7.5 V (i.e., e 3.3 mA, 14.2 mA). The lowest median current to obtain diaphragmatic stimulation without discomfort was found for the right brachiocephalic vein (4.7 mA). In 12/15 patients diaphragmatic movement could be induced without any discomfort, but in three patients hiccups occurred.

Diaphragmatic stimulation from the brachiocephalic and caval veins is feasible. Potential side effects should be eliminated by adapting the stimulation pattern. This information could be used to design a catheter, combining cardiac pacing with enhancing diaphragm movement during a sleep apnea episode.