Abstract Background Phospholamban (PLN) p.(Arg14del)-positive individuals are at risk for developing severe heart failure (HF), yet a comprehensive risk model for this outcome is missing. Our PLN registry contains longitudinal data which enables us to capture dynamic changes in covariables over time, while prior prediction models rely on baseline clinical information which may change over time. Using this longitudinal clinical information will enhance the accuracy of HF prediction and may aid patients selection for future (gene)therapy. Purpose The aim of this study is to develop a dynamic HF risk prediction model for PLN p.(Arg14del)-positive individuals. Method Data were collected of 594 PLN p.(Arg14del)-positive individuals who had no documented history of HF or myocardial infarction at time of the first echocardiography. We incorporated two time-dependent covariates in our time-varying Cox regression model: longitudinal individual predicted left ventricular ejection fraction (LVEF) and longitudinal individual predicted relative risk for major ventricular arrhythmia (VA). Predicted LVEF values were derived using observed LVEF values in a linear mixed-effect model, while the relative risk for major VA was predicted using a Cox regression model with major VA as the outcome. These time-dependent covariates were included in the time-varying Cox regression along with baseline covariables age at inclusion and previous major VA. The results were validated using 5-fold cross-validation. Results Over a median follow-up period of 3.6 years (interquartile range 1.4-6.8), 77 (13%) individuals developed HF, defined as a composite endpoint of HF hospitalisation, implantation of left ventricular assist device, heart transplantation and HF-related mortality. Our time-varying Cox regression model demonstrated a robust 5-year mean C-statistic of 0.904 (95% CI 0.901-0.908). The hazard ratio for time-dependent LVEF predictions was 0.89 per % LVEF increase (95% CI 0.87-0.91, p <0.001) and for time-dependent relative major VA risk predictions 3.59 (95% CI 1.49-8.69, p = 0.005). Regarding baseline covariates, age at inclusion had a hazard ratio of 1.01 (95% CI 0.99-1.03, p = 0.47) and previous major VA 0.48 (95% CI 0.21-1.1, p = 0.08). Combining the hazard ratios of time-dependent predicted relative risk for major VA and major VA in history results in a hazard ratio of 1.73. Conclusion Our study introduces a novel time-varying Cox regression model for the individual prediction of heart failure events in PLN p.(Arg14del)-positive individuals which may aid patient selection for future (gene)therapy. Results demonstrate robust predictive performance (C-statistic of 0.904, 95% CI 0.901-0.908), highlighting the significance of incorporating longitudinal data for enhanced prediction accuracy.

Abstract Background Patients with the phospholamban (PLN) p.(Arg14del) variant can develop a severe cardiomyopathy, characterized by progressive heart failure (HF) and major ventricular arrhythmias (VA). However, there is a marked variability in disease expression among affected individuals. There is still a considerable gap of knowledge regarding the influence of comorbidities and substance use on disease progression. Purpose The aim of this study is to investigate whether specific comorbidities and substance use are associated with HF events or major VA events in PLN p.(Arg14del) positive individuals. Method Logistic regression analysis was conducted was conducted in a retrospective cohort of 880 PLN p.(Arg14del) positive individuals (N=847 without heart failure at baseline, N=810 without major arrhythmia at baseline and N=780 without both). Comorbidities and substance use at baseline were assessed in univariable and multivariable models with respect to HF events, major VA events, and a composite endpoint of these two referred to as ‘severe phenotype’. Heart failure was defined as heart failure hospitalization, left ventricle assist device implantation, heart transplantation or HF-related death. Major VA was defined as sustained VA, appropriate implantable cardioverter defibrillator intervention, or (aborted) sudden cardiac death. Results Of all tested comorbidities, only renal dysfunction defined as an eGFR (CKD-EPI) <60 ml/min per 1.73 m² was significantly and independently associated with all endpoints (p<0.001). In the substance use analysis, prior history of smoking was associated with heart failure and a severe phenotype (p<0.002 and p<0.021), however actively smoking was not associated with both endpoints. Conclusion Renal dysfunction and a history of smoking were the only factors identified to be associated with worse outcomes in PLN p.(Arg14del) positive individuals. Whether renal dysfunction signifies a risk factor or an early manifestation of disease has to be further elucidated.

Abstract Background PLN p.(Arg14del) positive individuals are at risk for developing arrhythmogenic cardiomyopathy which can cause severe heart failure. Future gene therapy could be lifesaving and is rapidly advancing. It is therefore of importance to identify eligible patients for this evolving treatment, with individuals risk prediction playing an imperative role in this process. Purpose To develop a dynamic prediction model for the individual risk prediction of heart failure in PLN p.(Arg14del) positive individuals. Method Data were collected of 564 PLN p.(Arg14del) positive individuals with no baseline history of heart failure or myocardial infarction. During a median follow-up of 6.3 years (interquartile range 2.9-10.0), 74 individuals experienced heart failure, defined as a composite endpoint of heart failure hospitalization, left ventricle assist device implantation, heart transplantation and heart failure-related death. For the individual prediction of time to heart failure we used a joint model which simultaneously estimates a longitudinal model for repeatedly measured left ventricle ejection fraction (LVEF) during follow-up and a Cox regression model for the hazards of the heart failure endpoint. Using the longitudinal model we predicted the LVEF-values of all patients at future time points using the estimated random-effects and these predicted LVEF values were used as a time-dependent covariate in the Cox model which also contained age at start of follow-up as predictor variable. Results The joint model trained in this study had a very good performance in discriminating the individuals at risk for heart failure, with the 5-year mean AUC of 0.86 and 10-year mean AUC of 0.84. The LVEF had a hazard ratio of 0.89 (95% confidence interval (CI) 0.86-0.93, p<0.001), and age at baseline 1.04 (95% CI 1.03-1.06], p<0.001), meaning a lower LVEF and higher age at presentation were associated with heart failure. Figure 1 shows an example of an individual risk prediction with on the x-axis the follow-up time in years, on the y-axis (left) the LVEF in % and on the y-axis (right) the predicted survival probability. Conclusion Individual risk prediction with a simple model including only LVEF and age is of great importance for identifying PLN p.(Arg14del) positive individuals who are at risk of developing heart failure. The introduction of this novel joint prediction model is the first step in identifying individuals at risk for heart failure and may aid patient selection for future gene therapy interventions.

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The Netherlands Cardio Vascular Research Initiative (CVON): the Dutch Heart Foundation, Dutch Federation of University Medical Center, the Netherlands Organization for Health Re-search and Development and the Royal Netherlands Academy of Sciences Introduction Sudden cardiac death (SCD) is one of the severe manifestations in carriers with a phospholamban (PLN p.Arg14del) cardiomyopathy. Prediction whether a patient with this pathogenic variant will be at risk for SCD is difficult. PLN has an important role in cardiac calcium homeostasis as regulator of the sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA). It has been shown that the p.Arg14del pathogenic variant leads to Ca2+ overload in cardiomyocytes. Recently, it was found that dilated cardiomyopathy (DCM) patients who have a polymorphism in histidine-rich calcium binding protein (HRC Ser96Ala, rs3745297), displayed an increased risk for malignant arrhythmias and SCD. HRC resides within the SR, where it acts as a regulator of Ca2+ homeostasis. This Ser96Ala gene variant is widespread, as 60% of the general population bears at least one copy of this allele. Objective To explore the effect of the HRC Ser96Ala polymorphism on ventricular arrhythmias and disease expression in PLN p.Arg14del pathogenic variant carriers. Methods 337 p.Arg14del patients were included into the study; divided into wildtype (WT) (n=134, 24 index patients), heterozygous for Ser96Ala variant (n=142, 30 index patients) and homozygous for Ser96Ala variant (n=61, 11 index patients). The study was conducted according to the Declaration of Helsinki. Blood samples were genotyped on the Infinium® Global Screening Array-24 v3.0. Clinical data were subtracted from health records. Results In total 23% of PLN variant carriers were diagnosed with DCM while 11% of the variant carriers were diagnosed with arrhythmogenic cardiomyopathy. A significant difference in age of presentation (p=0.019) of p.Arg14del patients diagnosed with a DCM phenotype was found in homozygous HRC variant carriers (median 43 years, [36-47.3], n=8) compared to WT (median 49 years, [41-56.8], n=24) and heterozygous variant carriers (median 58.5 years, [51-66.5], n=22). No significant differences between the 3 groups were detected in manifestations of premature ventricular contractions (n=188, p=0.203), non-sustained ventricular tachycardia (n=248, p=0.314) and appropriate ICD shocks (n=308, p=0.901). Conclusion Although a significant difference in disease onset was found in PLN p.Arg14del patients with DCM who were homozygous for the HRC polymorphism, no correlations with arrhythmogenic parameters were found between patients with and without the HRC polymorphism. Therefore, we conclude that presence of the HRC polymorphism is not a discriminative predictor for arrhythmogenic events in PLN p.Arg14del.