Ventricular repolarization homogeneity in transthyretin cardiac amyloidosis

Abstract

Abstract Funding Acknowledgements Type of funding sources: None. Background Non-sustained ventricular tachycardia is frequently observed in patients with transthyretin cardiac amyloidosis (TTR-CA); however, the incidence of sudden tachyarrhythmic death is low. Homogeneity of amyloid fibril deposition within the myocardium and conduction system may mitigate against sustained ventricular tachyarrhythmias. In contrast, myocardial scar heterogeneity is an established predictor of sudden cardiac death in conditions such as hypertrophic cardiomyopathy (HCM), as evidenced by increased myocardial dispersion of repolarization. Whether such indices of arrhythmogenesis are evident in TTR-CA has not been established. Purpose To compare ventricular repolarization indices in TTR-CA to HCM and controls without known cardiovascular disease. Methods We identified TTR-CA and HCM patients from our single center respective registries, and control patients from our clinical ECG database. Only patients in normal sinus rhythm without bundle branch block, cardiac pacing or artifact were included for analysis. Demographic and clinical data were abstracted. ECGs were analyzed at 25 mm/s paper speed and 10 mm/mV amplitude. ECG parameters included QT interval, QT dispersion, and T peak to T end (TpTe) using the tangent method. All measurements were performed by two blinded independent cardiologists. Results A total of 112 patients (45 TTR-CA, 32 HCM, and 35 controls) were studied. Despite a longer QTc in TTR-CA (468.4 ms in TTR-CA vs. 424.6 in controls; p < 0.001), patients with TTR-CA demonstrated similar repolarization indices as controls, including TpTE (93.0 ± 13.5 ms in TTR-CA vs 86.4 ± 12.2 ms in controls, p = 0.24), and TpTe/QTc (0.20 ± 0.03 in TTR-CA vs 0.2 ± 0.03 in controls, p = 0.99). In contrast, HCM patients demonstrated greater TpTe and TpTe/QTc compared with controls (Figure). and a trend toward increased QT dispersion in HCM vs. TTR-CA (p = 0.06). Conclusion Unlike HCM, patients with TTR-CA demonstrate a relative lack of myocardial repolarization heterogeneity compared with controls. This finding correlates with homogeneous distribution of myocardial amyloid fibrils and may explain the low observed incidence of sudden cardiac death in this population. Abstract Figure