A simple ballistocardiographic measure (IJ/HI amplitude ratio) in relation to electrocardiographic evidence of ischaemic heart disease.

A series of eighteen monozygotic and thirteen dizygotic twin pairs originally selected in 19=7--1968 because of the presence of symptoms of ischemic heart disease in at least one of the pair members was subjected to after examination including ultra-low frequency ballistocardiography. The ratio between IJ and HI amplitudes in the ballistocardiogram was used as an index of myocardial mechanical function. The IJ/HI ratio had a repeatability coefficient of 0.82 before and/or after psychiatric interview. The mean ratio did not change significantly after psychiatric interview. The measure was demonstrated to be independent of height, weight, age, heart rate and systolic and diastolic blood pressure and negatively correlated with a measure of somatic anxiety. The ratio was highly significantly correlated with electrocardiographic evidence of ischemic heart disease. The IJ/HI ratio showed a better discrimination than qualitative readings according to Starr and furthermore has the advantage of providing a continuous measure. The ratio seemed to be more influenced by the functional state of the myocardium than by genetic factors.