Optimal Site for Atrial Lead Implantation in Myotonic Dystrophy Patients: The Role of Bachmann’s Bundle Stimulation GERARDO NIGRO, M.D. PH.D.,* VINCENZO RUSSO, M.D.,* PASQUALE VERGARA, M.D.,* ANTONELLO D’ANDREA, M.D.,* GRAZIA DI GREGORIO, M.D.,† LUISA POLITANO, M.D.,† GIOVANNI NIGRO, M.D.,† and RAFFAELE CALABR ` O, M.D.* From the *Chair of Cardiology, Second University of Naples—Monaldi Hospital, Naples, Italy; and †Cardiomyology and Genetic Section, Department of Internal and Experimental Medicine, Second University of Naples, Naples, Italy Aim: The aim of this study was to identify the optimal site for atrial lead implantation in myotonic dystrophy type 1 (MD1) patients. Methods: The atrial pacing lead was positioned in the high-lateral right atrial wall (site A), then in the right atrial appendage (site B), and finally on the interatrial septum (site C) in 22 patients. Pacing and sensing thresholds were obtained for all sites. The lead was repositioned and fixed at the optimal site, defined as the location with the lowest pacing and the highest sensing thresholds. Results: Mean pacing thresholds were 1.46 ± 0.32 V at site A, 1.45 ± 0.33 V at site B, and 0.84 ± 0.24 V at site C. P-wave amplitude was 1.52 ± 0.45 mV at site A, 1.52 ± 0.49 mV at site B, and 2.60 ± 0.48 mV at site C. Atrial lead was implanted at site C in all patients without complications. Conclusions: Interatrial septum in the region of Bachmann’s Bundle seems to be the optimal site for atrial lead implantation in MD1 patients. (PACE 2008; 31:1463–1466) myotonic dystrophy, pacemaker, arrhythmias, heart block, fibrosis, sensing, pacing, optimal site Introduction Myotonic dystrophy type 1 (MD1), or Stein- ert’s disease, is the most common muscular dys- trophy in adult life with an incidence of one in 8,000 births. 1,2 It is an autosomal dominant disor- der caused by an abnormal expansion of an un- stable trinucleotide repeat in the three-prime un- translated region of DMPK gene on chromosome 19. 3 The phenotype is characterized by myotonia and muscle weakness, but multisystem involve- ment is frequent. Heart block is the first and most clinically significant cardiac disease in this group of patients and it is related to fibrosis of the con- duction system and fatty infiltration of the His bun- dle. 4 Several studies documented that right atrial and ventricular myocardium are affected by this disease, together with specialized conduction sys- tem. 5–7 To prevent cardiac sudden death implanta- tion of a pacemaker (PM) is required in 3–22% of cases. 8–10 Due to the progressive nature of the dis- ease, areas of unaffected myocardium are progres- sively replaced by scar and many patients mani- fest during follow-up sensing and pacing defects on the atrial lead. We speculated that some ar- 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. Fax: 081-7062355; e-mail: v.p.russo@libero.it Received May 1, 2008; revised July 18, 2008; accepted July 20, 2008. eas of the atrial myocardium are prone to fibrosis, while other areas remain electrically active even in advanced phases of the disease. The aim of this study was to locate atrial sites less affected by con- duction abnormalities due to interstitial fibrosis, in order to identify the optimal site for atrial lead implantation. Methods Twenty-two consecutive MD1 patients (15 males; 32 ± 7 years) were enrolled in the present study, after having given written informed con- sent. A gender and age-matched control group was selected from non-MD1 patients who under- went permanent PM implantation in our division. The study was approved by our Institution’s Eth- ical Committee. The inclusion criteria were (1) indication for permanent PM implantation accord- ing to the ACC/AHA/NASPE 2002 Guideline for Implantation of Cardiac Pacemakers and Antiar- rhythmia Devices 8 and (2) in absence of ventric- ular arrhythmias both spontaneous and induced during electrophysiological study. A molecular ge- netic test was systematically performed in all pa- tients to evaluate the CTG triplet expansion and to confirm the diagnosis of MD1. DNA was ex- tracted from peripheral blood samples; diagnosis was made in the presence of an expansion of the CTG triplet over 50. Before implantation of a dual- chamber PM (Medtronic Kappa D901, or Adapta ADDR01, Medtronic Inc., Minneapolis, MN, USA), physical examination, 12-lead electrocardiogram (ECG), 24-hour ECG Holter monitoring, and C 2008, The Authors. Journal compilation C 2008, Blackwell Publishing, Inc. PACE, Vol. 31 November 2008 1463