Right Atrial Appendage Versus Bachmann’s Bundle Stimulation: A Two-Year Comparative Study of Electrical Parameters in Myotonic Dystrophy Type-1 Patients GERARDO NIGRO, M.D., PH.D.,* VINCENZO RUSSO, M.D.,* LUISA POLITANO, M.D.,† NADIA DELLA CIOPPA, M.D.,‡ DONATELLA MANFREDI, M.D.,* RAFFAELE CHIANESE, M.D.,* ANNABELLA DE CHIARA, M.D.,* ANNA RAGO, M.D.,* GIULIA ARENA, M.D.,* ALBERTO PALLADINO, M.D.,† and RAFFAELE CALABR ` O, M.D.* From the *Chair of Cardiology, Second University of Naples—Monaldi Hospital, Naples, Italy; †Cardiomyology and Genetic Section, Department of Internal and Experimental Medicine, Second University of Naples, Italy; and ‡Department of Anestesy and Rianimation, Monaldi Hospital, Naples, Italy Aim: We performed a two-year follow-up comparative study of long-term electrical parameters between the right atrial appendage (RAA) and Bachmann’s Bundle (BB) stimulation in myotonic dystrophy type 1 (MD1) patients. Methods: Twenty-five MD1 patients (18 men; age: 54 ± 13 years) with no difference in the electrical parameters between the RAA site and the BB region at implantation were randomized into two groups: in group I (13 patients; age: 52 ± 14 years; four women) the atrial lead was placed in the RAA and in group II (12 patients, age: 56 ± 12 years, three women) the lead was placed in the BB region. Measurements of electrical parameters were recorded at follow-up intervals of 6 weeks and then 12 and 24 months postimplant. Results: There was no statistically significant different in P-wave amplitude, pacing threshold, and impedance values between the two groups at 6 weeks. At 24 months follow-up, the intrinsic P-wave amplitude was 2.05 ± 1.45 mV in the RAA group versus 3.28 ± 1.09 mV in the BB group (P < 0.05); the pacing threshold was 1.85 ± 1.8 V in the RAA group versus 0.50 ± 0.39 V in the BB group (P = 0.03); there were no differences in the atrial impedance between the two groups during the follow-up period. Conclusions: In a direct two-year follow-up comparison between the RAA and BB atrial pacing sites, we showed a statistically significant increased pacing threshold and decreased intrinsic P-wave amplitude during RAA stimulation in MD1 patients. (PACE 2009; 32:1191–1196) Bachmann’s bundle, myotonic dystrophy, pacemaker, arrhythmias, heart block, fibrosis, sensing, pacing, impedance, atrial lead Introduction Myotonic dystrophy type 1 (MD1), or Stein- ert’s disease, is a multisystem disorder with autosomal dominant inheritance, caused by an unstable expansion mutation of the cytosine thymine-guanine (CTG) trinucleotide repeat situ- ated in the 3 ′ noncoding exon of a gene on chro- mosome 19q13.3, that encodes a serine-threonine protein kinase (DMPK). The MD1 has an incidence of 1/8,000 births and is characterized by highly variable clinical manifestation. 1–3 This disorder affects specific tissues, such as distal limb and This study was supported by Telethon Italy, Grant Number GUP02067. Address for reprints: Vincenzo Russo, M.D., Via della Re- sistenza, 48, 80021 Afragola, Naples, Italy; e-mail: v.p.russo@ libero.it Received December 19, 2008; revised March 8, 2009; accepted March 26, 2009. facial muscles, smooth muscles (gastrointestinal tract, uterus), the eye (primarily the lens), and the brain (especially the anterior temporal and frontal lobes), as well as endocrine function (testosterone deficiency, abnormal growth hormone regulation, insulin resistance). The cardiac involvement is noticed in about 80% of cases, and it often pre- cedes the skeletal muscle one. Histopathology studies disclosed fibrosis in the conducting sys- tem and in the sinoatrial node associated with myocyte hypertrophy and fatty acid infiltration. 4 Pacemaker (PM) implantation should be consid- ered in symptomatic patients with conduction abnormalities. 5 In our clinical experience, MD1 patients who underwent conventional right atrial appendage (RAA) lead implantation manifested during follow-up period sensing and pacing de- fects on the atrial lead. We recently reported 6 that interatrial septum in the region of Bachmann’s bundle (BB) is the atrial site with better sensing and pacing threshold at implantation compared C 2009, The Authors. Journal compilation C 2009 Wiley Periodicals, Inc. PACE, Vol. 32 September 2009 1191