title: Management of phrenic stimulation in CRT patients over the long term: still an unmet need ?
abstract: BACKGROUND
  Phrenic stimulation (PS) may cause intolerable symptoms and prevent CRT delivery in 2-5% of patients. We sought to ensure effective cardiac resynchronization therapy (CRT) delivery by management of PS at the left ventricular (LV) target site.
  
  
  RESULTS
  Two hundred and eleven consecutive patients received a CRT device despite PS occurrence at the LV target site at implantation, when a PS-LV difference >2V was achieved by LV stimulation programming (cathode, pacing vector). PS management strategy both at implantation and at follow-up (FU) aimed to keep the target LV implantation site. LV reverse remodeling was assessed by echocardiography before implantation and at follow-up. LV lead placement was lateral/posterolateral in all the 211 patients; 51 of 211 had detectable PS at FU, 26 of 211 (12.3%) were symptomatic. Symptoms occurred more frequently when PS-LV difference was <3V (16/16 vs 10/35, P < 0.001). Cathode and pacing vector reprogramming improved the PS-LV difference and symptoms in 14 of 23 patients. LV output as threshold +0.5V was helpful to manage PS symptoms in patients with a PS-LV ≤2V at FU. Median FU was 34.9 (16-50) months: 12 patients had tolerable PS symptoms, 76% (39/51) were objective responders at echocardiography compared to 74% (119/160) in patients without PS (P = NS).
  
  
  CONCLUSIONS
  CRT delivery at long term is feasible despite PS at the target LV site. PS management is mandatory in about 12.3% of patients at FU, with 6.6% remaining symptomatic. Symptoms improve at FU when a PS-LV >3V is achieved. Further improvement in lead manufacturing and pacing electronics are awaited to meet this clinical need.
authors.affiliation: Institute of Cardiology, Policlinico S.Orsola-Malpighi, University of Bologna, Bologna, Italy. mauro.biffi@aosp.bo.it
authors.forename: Mauro
authors.initials: M
authors.lastname: Biffi
authors.forename: Matteo
authors.initials: M
authors.lastname: Bertini
authors.forename: Matteo
authors.initials: M
authors.lastname: Ziacchi
authors.forename: Beatrice
authors.initials: B
authors.lastname: Gardini
authors.forename: Andrea
authors.initials: A
authors.lastname: Mazzotti
authors.forename: Giulia
authors.initials: G
authors.lastname: Massaro
authors.forename: Igor
authors.initials: I
authors.lastname: Diemberger
authors.forename: Cristian
authors.initials: C
authors.lastname: Martignani
authors.forename: Cinzia
authors.initials: C
authors.lastname: Valzania
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Boriani
mesh_terms: D000368:Aged; D058406:Cardiac Resynchronization Therapy; D004452:Echocardiography; D004558:Electric Stimulation; D005260:Female; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010791:Phrenic Nerve / Q000503:physiopathology*; D013318:Stroke Volume / Q000502:physiology; D016896:Treatment Outcome; D020257:Ventricular Remodeling