Recent studies have reported that in patients under antihypertensive treatment visit-to-visit (or long-term) variability of clinic BP within a given patient has an independent prognostic significance. Partly based on between-patient dispersion of BP values during treatment (interindividual variability) it has also been reported that long-term clinic BP variability is greater for β-blocker than for calcium antagonist and other types of treatment.
To measure visit-to-visit intraindividual variations of both clinic and 24-h mean BP in the hypertensive patients of the European Lacidipine Study on Atherosclerosis (ELSA) trial treated for 4 years with either atenolol or lacidipine, and to check whether interindividual clinic and 24-h BP variabilities during treatment can really be considered a surrogate of intraindividual variabilities in exploring differences between β-blocker and calcium antagonist treatments.
Long-term intraindividual BP variability was defined as the coefficient of variation of the average systolic or diastolic values of clinic and 24-h BP measured at each visit throughout the treatment period. Patients in whom at least seven clinic (6-month intervals) or at least three (yearly intervals) 24-h values were available from the end of the drug titration phase to the end of the study were considered.
Visit-to-visit 24-h SBP/DBP variabilities were 20–25% smaller than, and loosely correlated with clinic BP variability (r2 < 0.022). There was also a very limited relationship (r2 < 0.026) between visit-to-visit and within 24-h ambulatory BP variabilities, the latter being two to three times greater than the former. Visit-to-visit intraindividual clinic SBP variability was only slightly lower on calcium antagonist than on β-blocker treatment but little or no between-treatment difference was found for visit-to-visit clinic DBP and ambulatory SBP/DBP particularly in patients under monotherapy throughout the study. Interindividual BP variability was markedly greater than the intra-individiual one of which it did not precisely reflect the treatment-induced changes.
In mild-to-moderate hypertensive patients, visit-to-visit BP variability does not differ substantially between β-blocker and calcium antagonist treatment. Major discrepancies exist between visit-to-visit BP variability as quantified by 24-h vs. clinic BP, making investigation of which of these indices is clinically more relevant important. Interindividual BP variability during treatment shows marked quantitative differences with intraindividual BP variability questioning whether its use can accurately reflect individual BP variations from one visit to another.