Repeat variation of electrocardiogram, blood pressure, and blood cholesterol within one hour and six months.

The intraindividual repeat variation of the conventional 12-lead electrocardiogram, of blood pressure, and of blood cholesterol was determined in 27 middle-aged healthy men with an interval of one hour and six months. In 7 of 17 analysed electrocardiographic items the variation within six months was significantly greater than that within one hour; in 10 items, the variation was not significantly different. Blood pressure varied as much within one hour as within six months, while the intraindividual variation of serum cholesterol was significantly greater for the six-month period. The intraindividual variation, expressed as the coefficient of variation, was greater for the electrocardiogram than for either blood pressure or cholesterol. There were large differences between various electrocardiographic items in the repeat variation. There was high intraclass correlation of most items analysed, but no significant covariation between electrocardiographic item vs. blood pressure or cholesterol.