RESUMO
BACKGROUND: Atrial undersensing despite normal atrial lead parameters and high amplitude electrograms has been described in adult patients as a consequence of atrial amplifier saturation. Repetitive inputs cause amplifier ringing and undersensing occurs as a consequence of quiet timer blanking. High amplitude ventricular electrograms can also result in atrial blanking secondary to cross-chamber effect. This has not been described in pediatric patients or epicardial pacing systems and specific risk factors are not known. We describe five cases of atrial undersensing in pediatric and congenital heart disease patients with epicardial dual-chamber systems and high ventricular lead outputs. METHODS: This was a retrospective cohort study of all patients with dual-chamber pacing systems cared for at the Heart Institute at Children's Hospital Colorado. RESULTS: Five cases of atrial undersensing with normal atrial lead parameters were found. All were epicardial systems with acceptable lead parameters at implantation and Medtronic (Medtronic, Inc., Minneapolis, MN, USA) generators with unipolar leads. Ventricular pacing outputs were elevated at presentation, median 5.5 V (5-7.5). Presenting symptoms were exercise intolerance (four) and detection on routine monitoring (one). Successful interventions included reduction in ventricular lead pacing output (one), programming of rate response (two), and implantation of an alternative generator manufacturer (two). CONCLUSION: Atrial undersensing secondary to amplifier ringing and quiet timer blanking is an uncommon presentation but may be clinically important in patients with unipolar epicardial atrial leads and high pacing outputs from ventricular leads.
Assuntos
Estimulação Cardíaca Artificial/métodos , Análise de Falha de Equipamento , Átrios do Coração/fisiopatologia , Cardiopatias Congênitas/fisiopatologia , Marca-Passo Artificial , Colorado , Eletrocardiografia , Feminino , Humanos , Masculino , Estudos RetrospectivosRESUMO
OBJECTIVES: To identify the clinical presentation of children and adolescents affected by 1 of 4 cardiac conditions predisposing to sudden cardiac arrest: hypertrophic cardiomyopathy, long QT syndrome (LQTS), catecholaminergic polymorphic ventricular tachycardia (CPVT), and anomalous origin of the left coronary artery from the right sinus of Valsalva (ALCA-R). STUDY DESIGN: This was a retrospective review of newly diagnosed pediatric patients with hypertrophic cardiomyopathy, LQTS, CPVT, and ALCA-R referred for cardiac evaluation at 6 US centers from 2008 to 2014. RESULTS: A total of 450 patients (257 male/193 female; median age 10.1 years [3.6-13.8 years, 25th-75th percentiles]) were enrolled. Patient age was ≤13 years for 70.4% of the cohort (n = 317). Sudden cardiac arrest was the initial presentation in 7%; others were referred on the basis of abnormal or suspicious family history, personal symptoms, or physical findings. Patients with LQTS and hypertrophic cardiomyopathy were referred most commonly because of family history concerns. ALCA-R was most likely to have abnormal signs or symptoms (eg, exercise chest pain, syncope, or sudden cardiac arrest). Patients with CPVT had a high incidence of syncope and the greatest incidence of sudden cardiac arrest (45%); 77% exhibited exercise syncope or sudden cardiac arrest. This study demonstrated that suspicious or known family history plays a role in identification of many patients ultimately affected by 1 of the 3 genetic disorders (hypertrophic cardiomyopathy, LQTS, CPVT). CONCLUSION: Important patient and family history and physical examination findings may allow medical providers to identify many pediatric patients affected by 4 cardiac disorders predisposing to sudden cardiac arrest.