Pacing sensation with a second generation intercostal extravascular ICD lead

Abstract Background/Introduction An investigational intercostal extravascular ICD lead (EV-ICD Lead) has been developed to provide antitachycardia pacing and shock treatment of ventricular tachyarrhythmias when connected to a commercially available ICD pulse generator. Unlike other available extravascular ICD systems that achieve pacing with ring electrodes which transmit undirected current to cardiac and non-cardiac tissue alike, the intercostal EV-ICD Lead uses button-shaped electrodes backed by an insulative paddle to direct current toward excitable myocytes while minimizing undesired excitation of the adjacent tissues. Purpose The purpose of this analysis was to evaluate pacing sensation with the intercostal EV-ICD Lead connected to a commercially-available ICD pulse generator programmed to the maximum voltage output and pulse width settings. Methods In the STEP ICD Study (n=20), pacing sensation was evaluated at the pre-discharge visit while pacing at the maximum programmable voltage output (7.5 or 8.0 V, depending on manufacturer) and pulse width (1.5 or 2.0 ms). Sensation was reported by the patient as one of four choices: No Sensation, Sensation Only, Tolerable Pain or Intolerable Pain. Results Pacing sensation was assessed in 18 of 20 patients. One (1) patient did not undergo a pacing evaluation due to atrial fibrillation with rapid ventricular response. Responses were as follows: No Sensation in 4 (22%) patients, Sensation Only in 10 (56%) patients, Tolerable Pain in 3 (17%) and Intolerable Pain in 1 (6%). In no patient was the pain so severe that pacing capture threshold testing could not be completed. Of note, the single report of intolerable pain was only reported in the sitting posture. When tested supine, the patient reported sensation only. Conclusion(s) The design of the investigational intercostal EV-ICD Lead, with button-shaped electrodes backed by an insulative paddle, produced low levels of patient sensation at maximum output and pulse width. These sensation levels represent an improvement over designs that employ ring electrodes and indicate that antitachycardia pacing will be well tolerated with the novel EV-ICD Lead. These results corroborate the predictions about patient discomfort from in silico models.