Threshold values by electrocardiogram and echocardiography indicating transition to an arrhythmic phenotype in cardiac laminopathies: a primary prevention cohort study

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): 1) Precision Health Care Center for optimized cardiac care (ProCardio) supported by the Norwegian Research Council 2) European Research Area Network on Cardiovascular Diseases (ERA-CVD) Background/Introduction Cardiac laminopathies are malignant and pro-arrhythmic variants of familial dilated cardiomyopathy caused by mutations in the LMNA gene. Correct timing of implantable cardioverter defibrillator (ICD) implantation is crucial in these patients, but optimal timing of primary preventive ICD remains a great challenge in clinical practice. Purpose We aimed to explore threshold values by electrocardiogram and echocardiography to identify transition to a more arrhythmic phenotype in LMNA disease. Methods We prospectively included consecutively recruited LMNA genotype positive patients in a primary prevention cohort study. Patients underwent repeated clinical-, electrocardiogram- and echocardiographic examinations during long-term follow-up. Ventricular arrhythmia was defined as sustained ventricular tachycardia, appropriate therapy by a primary preventive ICD or aborted cardiac arrest. We explored electrocardiographic and echocardiographic cut-off values for increased odds of experiencing first-time ventricular arrhythmia during follow-up by threshold regression analyses. The cardiac phenotype at time of ventricular arrhythmia was assessed from electrocardiogram recording and echocardiographic examinations acquired ±12 months of the arrhythmic event. Results We included 94 LMNA genotype positive patients with no history of ventricular arrhythmia at baseline (age 38±15 years, 32% probands, 53% female). Incidence of VA was 20% (19 patients) during 4.6 (inter quartile range [IQR] 2.1-7.3) years follow-up, at mean age 50±11 years. We analysed 261 electrocardiogram recordings and 536 echocardiographic examinations. At time of first ventricular arrhythmia, most patients had pronounced conduction delay (PR interval 312 [IQR 204-430] ms) and evident left ventricular pathology (left ventricular ejection fraction [LVEF] 40±12 %, left ventricular end diastolic volume indexed [LVEDVi] 83±22 ml/m2). Electrocardiographic threshold values for increased arrhythmic risk were PR interval 280 ms (OR 1.9, 95% CI 1.5-2.5, per 5 ms increase after threshold, p