Electrocardiographic indicators of autonomic balance and mortality : a case-cohort approach.

Abstract

The aim of the study reported in this thesis is. to investigate in a population of apparently healthy middle-aged civil servants, the predictive value for cardiovascular mortality of presumed electrocardiographic indicators of autonomic imbalance. For the sympathetic/parasympathetic balance RR- and PQ-interval lengths were considered as indicators. QT-interval length was taken as a manifestation of the balance between left and right sympathetic innervation. Minor abnormalities in ST-segment level and T-wave amplitude may reflect both kinds of imbalance. however. may also be a consequence of myocardial or epicardial disease. The following questions were studied in relation to these electrocardiographic parameters: Are these parameters separately. at rest or after exercise. associated with the risk of allcause. cardiovascular and coronary heart disease mortality? Are the observed associations between these parameters and mortality risk independent of established cardiovascular risk factors? To what extent do these electrocardiographic parameters combined predict coronary heart disease mortality risk? In addition to the electrocardiographic subject matter. this thesis also contains a methodological digression. Its purpose is to evaluate the performance of the case-cohort sampling design relative to other cost-efficient designs and to extend methods of data analysis for this design