Evaluation of Electrocardiographic Measurements by High Density Electrode ECG

Inclusion Criteria: * Patient managed at the Bordeaux University Hospital for assessment of documented severe ventricular arrhythmia (VF, sudden resuscitated death) or suspected (syncope, family history of sudden death, ECG or Holter abnormality) or impaired ventricular conduction, OR * Patients managed for prophylactic ventricular defibrillator implantation, according to international recommendations: Heart disease with ejection fraction \< 35%, heart disease with sustained ventricular tachycardia, cardiomyopathies with high rhythmic risk, * Women of childbearing age with effective contraception. Exclusion Criteria: * patients under 14 years old, * pregnant or nursing woman.