174 | Chapter 8 multimodality risk calculation tool.4 This published ARVC risk calculator (www.ARVCrisk.com), which aims to predict the 5-year risk of first sustained VA in patients with definite ARVC, has since been validated in different settings and showed superior performance when compared to existing risk stratification algorithms.5–8 In the current cohort, annual event rate was slightly lower compared to the initial risk calculator study4 (3.6% [95% CI 2.6 – 5.0] vs 5.6% [95% CI 4.7 – 6.6]), which may be caused by a larger proportion of diagnosed family members in the current cohort, identified through cascade genetic testing. Still, the discriminative value was comparable (0.78 [95% CI 0.71 – 0.86] vs 0.77 [95% CI 0.73 – 0.81]). Deformation imaging in ARVC arrhythmic risk stratification Echocardiography has an important role in the diagnosis and follow-up of ARVC patients. However, traditional echocardiographic parameters, such as RV fractional area change and RV outflow tract diameter, may lack sensitivity with regards to detection of early disease substrates.4,25,26 Over the past two decades, echocardiographic deformation imaging has evolved into a sensitive method to detect regional abnormalities in myocardial function, reflecting structural disease manifestation in ARVC.26–28 Distinct abnormalities in regional myocardial function have been identified, which were associated with disease severity. These regional deformation patterns with delayed onset to shortening, reduced peak strain and post-systolic shortening (Figure 1) most likely reflect pathologic changes on tissue level which form the substrate for VA.15 An exploratory study sought to explain these specific deformation types by computer simulation using the CircAdapt model. Indeed, loss in contractility and increase in local myocardial stiffness characterized the regional function abnormalities. Studies consistently showed that the first and most severely affected area was the subtricuspid region of the RV lateral wall10,15,29, a well know predilection site for the earliest disease manifestation of ARVC.30 Echocardiographic deformation imaging is well suited to evaluate this specific region. Of interest, deformation abnormalities appear already early in the development of this disease and remain stable or progress over time.29,31 These observations and modelling data indicate that this specific functional assessment might be of incremental value in predicting VA, since it seems to reflect the microscopic alterations that form the substrate for re-entry tachycardia. Indeed multiple indicators of myocardial deformation have been associated to VA.10–13 In a previous primary prevention study including both ARVC patients and family members at risk, both LVMD and RVFWLS were strong predictors of arrhythmic outcome. 11 In a combined cohort with patients from our two centres, especially negative predictive value of normal regional deformation patterns for prior VA (98%) was high.10 The current prediction study is unique since it included only patients with a definite TFC diagnosis, which explains the high prevalence of abnormal regional RV deformation patterns (65%). Importantly, it confirmed the high negative predictive value of normal deformation, since all patients with VA within 5 years from baseline evaluation already showed regional abnormalities in the RV. In line with previous ARVC studies, the subtricuspid was consistently first and most severely affected. Up to now, added value of deformation imaging has never been tested on top of current clinical practice. The multimodality ARVC risk score4, a validated tool for clinical risk prediction tool guiding management and ICD necessity, created this opportunity. Deformation imaging added to the ARVC risk calculator In a multivariable model, RV deformation patterns and RVFWLS were the strongest independent predictors of first sustained VA. The superiority of RV parameters was not surprising given the
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