106 | Chapter 6 METHODS Study design and population We included a consecutive primary preventive cohort of ARVC patients and genotype positive family members evaluated at Oslo University Hospital, Rikshospitalet, Norway, between 1997 and 2021 with at least two clinical evaluations. Part of this cohort was reported in previous follow-up studies in ARVC patients.10,24 Patients with previous myocardial infarction and congenital heart disease were excluded. To focus on patients with early-stage structural disease, patients that met a major echocardiographic TFC at first evaluation were excluded. We also excluded patients who experienced sustained VA (defined as a documented history of sustained ventricular tachycardia, aborted cardiac arrest, or appropriated ICD therapy) at or prior to first evaluation. Clinical characteristics were recorded at first evaluation. Subjects were divided into three age-groups (<30 years, 30-50 years and ≥50 years) based on their age at first evaluation, either for complaints or for family screening. Time to first VA was recorded prospectively from time of inclusion. End of observation was cardiac transplantation, death, or last-clinical follow-up by January 1, 2021. All patients gave written informed consent. The study complied with the declaration of Helsinki and was approved by the Regional Ethical Committee of South-Eastern Norway. Echocardiography All available complete echocardiographic examinations in sinus rhythm between inclusion and last clinical follow-up were analysed. First evaluation was defined at the time of first echocardiography on compatible hardware (GE Vivid 7, E9, or E95, EchoPac 203, GE Vingmed, Horten, Norway). Presence of major echocardiographic TFC was determined at first evaluation for the purpose of patient selection. Left ventricular ejection fraction (LVEF) was measured by Simpson’s biplane method and speckle tracking deformation imaging of both the LV and RV was performed in all examinations, according to previously described protocols.18,21,25,26 We assessed segmental RV deformation patterns in an RV-focused 4-chamber view, whereby a single-wall tracing of the RV free wall was automatically divided into a basal, mid, and apical segment. Timing of pulmonary valve closure was assessed by Doppler traces in the RV outflow tract, obtained in the parasternal short-axis view. The following deformation parameters were measured in each segment: time to onset of shortening (or electromechanical interval), systolic peak strain, and the amount of post-systolic shortening. These parameters were used to classify patients into three subgroups, each presenting with a distinct RV deformation pattern as described in previous studies.13,19 In brief, a Type I pattern is normal deformation; a Type II pattern is characterized by delayed onset of shortening, reduced systolic peak strain, and minor post-systolic shortening; and a Type III pattern is characterized by little or no systolic peak strain, predominantly systolic stretching, and major post-systolic shortening (Central illustration, right upper panel). The LV global longitudinal strain (GLS) was calculated as the peak negative strain from the averaged regional 16-segment LV model.21 RV free wall longitudinal strain (RV FWLS) was defined as the peak negative strain from the averaged regional RV free wall deformation characteristic. All measurements were performed by a single observer (FK) blinded to clinical information.
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