Relevance of the trough-to-peak ratio to the 24 h blood pressure load

The ambulatory blood pressure load is generally defined as the proportion of elevated systolic or diastolic pressures over a 24 h period. This value represents the chronic pressure overload that induces myocardial and vascular damage associated with the hypertensive disease process. Blood pressure load has been defined as either the percentage of blood pressures exceeding 140/90 mm Hg while awake and 120/80 mm Hg during sleep or the integrated area under the blood pressure curve that exceeds the same values. Studies in untreated hypertensive patients have demonstrated that the blood pressure load is a better determinant of indices of hypertensive heart disease or hemodynamic indices than either the casual or mean ambulatory blood pressure. Thus, blood pressure load has become a popular method for the assessment of antihypertensive drug efficacy. Intuitively, drugs that have a low trough-to-peak ratio should be associated with an increased blood pressure load as the agent is losing its effectiveness at the end of the dosing period. However, the extent of the reduction at trough and peak times must be taken into consideration when evaluating these relationships. Some therapeutic modalities clearly have excessive blood pressure loads due to short therapeutic duration. Conversely, some agents with long durations of action may be associated with excessive blood pressure loads secondary to modest blood pressure reduction over time.