Electrocardiographic risk factors for sudden death : a study with 245 cases of sudden death during a two-year follow-up after 24-hour electrocardiography in 6693 patients

The present study was designed to assess the relation between parameters derived from twelve lead and twenty four hour electrocardiography and the occurrence of sudden death. More specifically, the aim was to study the risk implications of QTc interval duration (a parameter of the total duration of depolarization and repolarization of the myocardium) in the 12 lead electrocardiogram and that of high QTc interval variability, low heart rate variability, and frequent ventricular arrhythmias in the 24 hour electrocardiogram. A further objective of the study was to determine the prognostic value of all electrocardiographic parameters taken together with other clinical data. The epidemiology and etiology of sudden death is described in chapter two. Emphasis is placed on to those mechanisms which are detectable by electrocardiographic methods. In this chapter, the specific aims of the study are formulated. The methodological aspects of the study are presented in chapter three. General aspects of the nested case-referent study design are introduced and a description of the study population, the observed incidence of sudden death, and baseline characteristics are given. In chapter four the risk implications for sudden death of QTc prolongation in the twelve lead electrocardiogram are analysed and compared with the literature. In chapter five the risk implications of parameters concerning QTc and RR interval duration and variability as derived from 24 hour electrocardiography are studied. Detailed information on the computer-aided study analysis of the 24 hour electrocardiograms is supplied in the appendices of this chapter. In chapter six a prognostic model taking into account all electrocardiographic parameters in addition to routine clinical characteristics is developed. Chapter seven provides a general discussion of the findings of this study and their implications. Finally, an english and dutch summary are supplied