[How relevant is the trough-to peak ratio?]

A marked blood pressure rise in the early morning hours is associated with an increased prevalence of cardiovascular events. Moreover, it has been reported that the blood pressure fall during the night is inversely correlated with left ventricular mass, peripheral vascular resistance and cerebrovascular insults. Recently, assessment of the so called "trough-to-peak ratio" has been increasingly used in order to evaluate the duration of action of antihypertensive agents. In this review some aspects of this arithmetical index are highlighted, and specifically the fact that this ratio as a surrogate endpoint may in some circumstances influence the choice of an antihypertensive agent but nevertheless does not serve to predict the clinical efficacy of blood pressure lowering drugs. To date the trough-to-peak ratio remains a problematic parameter because of the lack of defined optimal values and the lack of general and standardised methods for its determination. It is thus a purely arithmetical index without major clinical relevance. Evaluation of the clinical efficacy of antihypertensive drugs should rather be based on 24-hour measurements, as a more reproducible parameter.