Reproducibility and clinical value of the trough-to-peak ratio of the antihypertensive effect: evidence from the sample study

Reproducibility of ambulatory blood pressure values and circadian blood pressure patterns in untreated subjects in a 1-11 month interval

OBJECTIVE

To evaluate in untreated subjects the reproducibility of mean values and four circadian patterns between two ambulatory blood pressure monitoring (ABPM) recordings separated by 1-11 months.

METHODS

We performed a retrospective analysis of 481 individuals (59% women) evaluated by ABPM on two occasions, visit 1 (V1) and 2 (V2), separated by 5.5+0.2 months. Four circadian patterns were defined by night/day systolic blood pressure (SBP) ratios: reverse dippers (RD), ratio >1.0; non-dippers (ND), ratio 0.9-1.0; dippers (D), ratio 0.8-<0.9; and extreme dippers (ED), ratio <0.8. Coefficients of correlation and concordance between the ABPM values at V1 and V2 and the reproducibility of the RD, ND, D and ED patterns were calculated by the percentage of the same profile from V1 to V2.

RESULTS

Mean 24-h blood pressure (BP) at V1 and V2 was 126.8/75.9±0.5/0.5 vs. 126.5/75.7±0.5/0.4 mmHg (NS). Nighttime SBP fall was 9.8±0.4 (V1) and 9.6±0.3% (V2) (NS). The correlation coefficient of ABPM data at V1 vs. at V2 was 0.41-0.69 (p<0.001) and the concordance coefficient was 0.34-0.57 (p<0.01). At V1, 38 subjects were classified as ED (7.9%); D, n=216 (44.9%), 187 as ND (38.9%) and 40 as RD (8.3%). At V2 only 26.3% of ED, 44.9% of D, 54.5% of ND and 40% of RD maintained the same profile as at V1.

CONCLUSION

In untreated subjects ABPM has high reproducibility for mean values but only modest reproducibility for circadian profiles, thereby challenging the prognostic value of BP dipping patterns.

Triple combination therapy in hypertension: the antihypertensive efficacy of treatment with perindopril, amlodipine, and indapamide SR

BACKGROUND AND OBJECTIVE

The blood pressure (BP) of most patients on antihypertensive monotherapy or bitherapy remains uncontrolled. Our study evaluated the efficacy of triple therapy with perindopril, amlodipine, and indapamide sustained release (SR) in patients with uncontrolled hypertension on previous antihypertensive therapy.

METHODS

This 4-month, multicenter, prospective, observational, open-label study included patients switched from previous antihypertensive therapy to triple therapy with perindopril, amlodipine, and indapamide SR. The main outcome was change in office BP from baseline to 4 months, as well as changes in 24-h ambulatory BP monitoring (ABPM) parameters in a subgroup of patients.

RESULTS

Age was 62.8 ± 11.3 years in 6,088 patients (55 % were male). Office BP at baseline was 158.1 ± 13.0/92.6 ± 8.8 mmHg. By 4 months, office BP decreased by 26.7 ± 13.3/12.9 ± 9.4 mmHg (p < 0.001). ABPM was performed in 62 patients. In these patients, 24-h systolic BP decreased (from 138.7 ± 12.5 to 125.5 ± 12.8 mmHg), as did 24-h diastolic BP (from 77.5 ± 11.4 to 70.4 ± 8.7 mmHg) (both p < 0.0001). Heart rate remained unchanged. In patients previously on renin-angiotensin-aldosterone system (RAAS) inhibitor/amlodipine, 24-h ambulatory systolic and diastolic BP decreased from 136.9 ± 12.8 to 125.4 ± 13.3 mmHg (p = 0.0003) and from 76.3 ± 12.6 to 70.2 ± 9.5 mmHg (p = 0.0005). In those previously on RAAS inhibitor/hydrochlorothiazide, 24-h ambulatory systolic and diastolic BP decreased from 137.8 ± 12.7 to 122.7 ± 15.4 mmHg (p = 0.0039) and from 73.6 ± 9.4 to 65.7 ± 7.3 mmHg (p = 0.002). Most (74 and 80 %, respectively) patients reached target ABPM values (<130/80 mmHg).

CONCLUSION

A triple combination of perindopril, amlodipine, and indapamide SR controlled BP effectively in hypertensive patients uncontrolled by previous antihypertensive monotherapy or bitherapy, including RAAS inhibitor/amlodipine or RAAS inhibitor/hydrochlorothiazide combinations.

Efficacy of olmesartan/amlodipine combination therapy in reducing ambulatory blood pressure in moderate-to-severe hypertensive patients not controlled by amlodipine alone

This previously unpublished, preplanned analysis investigated the efficacy of the olmesartan/amlodipine combination at different doses on 24-h blood pressure (BP) control, as well as assessed trough estimation of trough-to-peak ratio (TPR) and smoothness index (SI). Ambulatory BP monitoring was performed in patients with moderate-to-severe hypertension whose BP was inadequately controlled after 8 weeks' treatment with amlodipine 5 mg. Patients were randomized to continue with amlodipine 5 mg or to receive olmesartan/amlodipine 10/5, 20/5 or 40/5 mg for 8 weeks (Period II). Patients not achieving BP control were uptitrated to a more powerful regimen for another 8 weeks (Period III). During Period II, each olmesartan/amlodipine combination reduced 24-h systolic and diastolic BP (SBP/DBP), as well as morning and early morning SBP/DBP, significantly more than amlodipine 5 mg (P<0.001 for all). TPRs were higher in each olmesartan/amlodipine group than with amlodipine 5 mg, and SI values showed dose-related increases; olmesartan/amlodipine 40/5 mg produced a significantly higher SI for SBP and DBP (1.55 and 1.33, respectively) than amlodipine 5 mg (0.96 and 0.77, respectively, P<0.0001 for each). During Period III, uptitrated patients showed further BP reductions, which were largest in those on olmesartan/amlodipine 40/10 mg. SI values increased in uptitrated patients and were highest with olmesartan/amlodipine 40/10 mg (SBP 1.62/DBP 1.41). The olmesartan/amlodipine combination effectively reduces BP over 24 h, including the morning hours, in a dose-related manner. Compared with amlodipine alone, the olmesartan/amlodipine combination has a better 24-h coverage (TPR) and a dose-related improvement in BP lowering homogeneity (SI).

A systematic review and meta-analysis of candesartan and losartan in the management of essential hypertension

BACKGROUND

Candesartan is a relatively novel antihypertensive agent of the angiotensin receptor blocker (ARB). Several clinical trials have compared candesartan with losartan in the management of essential hypertension. However, systematic assessment of efficacy and safety between candesartan and losartan is still lacking.

METHODS

We reviewed randomised controlled trials (RCTs) comparing candesartan with losartan for net reduction in blood pressure from baseline, response and control rates, and incidences of common and serious adverse events.Weighted mean differences (WMD), and relative risk (RR) with 95% confidence intervals (CI) were calculated for continuous and dichotomous data, respectively.

RESULTS

A total of 12 RCTs with 3644 patients were included in this meta-analysis. When comparing the efficacy of candesartan and losartan in reducing systolic blood pressure (SBP) and diastolic blood pressure (DBP) at the end of the follow-up period, results with candesartan were superior to losartan in the reduction SBP and DBP (WMD, -2.97; 95% CI, -4.18 - -1.77; p < 0.001; WMD, -1.76; 95% CI, -2.57 - -0.96; p < 0.001; respectively). Candesartan had better response and control rates than losartan. (RR, 1.12; 95% CI, 1.06-1.18; p < 0.01; RR, 1.26; 95% CI, 1.06-1.50; p = 0.008). Reported common adverse events for the two agents were not significantly different (RR, 0.98; 95% CI, 0.86-1.12; p = 0.78). The incidence of serious adverse events for candesartan was lower than for losartan (RR, 0.48; 95% CI, 0.25-0.92; p = 0.03). The net reduction of DBP showed negative correlation with baseline DBP in both candesartan and losartan groups (regression coefficient -1.81, p = 0.03 and regression coefficient -1.56, p = 0.02, respectively).

CONCLUSIONS

Candesartan is superior to losartan in reducing blood pressure. Candesartan also causes fewer serious adverse events than losartan.

The population RDH index: a novel vector index and graphical method for statistical assessment of antihypertensive treatment reduction, duration, and homogeneity

Current indices used in the evaluation of antihypertensive treatment duration and homogeneity such as the trough-peak, smoothness index, and normalized smoothness index were designed to be applied to ambulatory blood pressure monitoring recordings from individual participants. Evaluation of antihypertensive treatment in populations is often carried out by calculating these individual indices for each of the participants and providing summarizing statistics about the population, such as the mean and median. We describe a new population vector index and graphical method for the statistical assessment of antihypertensive treatment reduction, duration, and homogeneity (RDH) from ambulatory blood pressure monitoring. The population (RDH) was specifically designed as a tool to evaluate and compare blood pressure coverage offered by antihypertensive drugs over 24 h in populations. The population RDH is a three-component vector index that incorporates information about the reduction, duration, and homogeneity of antihypertensive treatment, as well as their statistical significance over the 24 h period. In addition to defining the RDH index, in this paper we also demonstrate its usefulness and advantages as an index and graphical method for antihypertensive treatment duration and homogeneity assessment by using it to analyze two data sets.

Efficacy and duration of action of the four selective angiotensin II subtype 1 receptor blockers, losartan, candesartan, valsartan and telmisartan, in patients with essential hypertension determined by home blood pressure measurements

Our objective was to compare the efficacy and duration of action of 4 angiotensin II receptor blockers (ARBs)--losartan (25-100 mg), candesartan (2-12 mg), valsartan (40-80 mg), and telmisartan (10-40 mg)-in patients with essential hypertension using self-measurement of blood pressure at home (home BP) and to examine the differential effect of the four ARBs on home pulse pressure (home PP). After a 2-week run-in period, each of the 4 ARBs was assigned to subjects who were diagnosed as having hypertension on the basis of home BP and who were over 30 years old. The subjects were asked to take the ARB once daily in the morning and to measure home BP once in the evening and in the morning. We compared the efficacy of each ARB on home BP and home PP and assessed the duration of the BP-lowering effect using the morning effect versus evening effect ratio (M/E ratio). The antihypertensive effects of telmisartan on home systolic BP (SBP) both in the evening and in the morning and on home diastolic BP (DBP) in the morning were significantly greater than those of losartan. The effect of each ARB on home BP in the morning and in the evening was expressed as a ratio (M/E ratio). The M/E ratios of SBP/DBP in patients treated with losartan, candesartan, valsartan, and telmisartan were 0.49/0.16, 0.69/1.01, 0.82/0.88, and 0.88/0.88, respectively. The home PP-lowering effect was greater for valsartan and telmisartan than for losartan and candesartan in the morning. Among the 4 ARBs, the duration of the BP-lowering effect of losartan did not persist throughout 24 hr. The effects of the other 3 ARBs, in particular telmisartan, persisted over 24 hr when they were administered once daily in the morning. In addition, the duration of the PP-lowering effect was similar to that of the BP-lowering effect. Such long-acting property of several ARBs is essential for the modern antihypertensive treatment, and home BP measurements are useful for determining the duration of action of antihypertensive drugs. Losartan, 25 mg a day, which is usually used as an initial dose in Japan, is apparently insufficient to obtain adequate antihypertensive effect and sufficient duration of action.

Reproducibility of postexercise ambulatory blood pressure in Stage I hypertension

The accuracy and reproducibility of ambulatory blood pressure monitoring used in intervention and treatment studies is essential to assure the desired health outcomes. The reproducibility of ambulatory variables in pharmacological studies has been reported, however, the reproducibility of ambulatory blood pressure variables associated with exercise has not been reported. Thus, the purpose of this study was to investigate the reproducibility of the postexercise ambulatory blood pressure in Stage I hypertensive adults. It was hypothesized that the reproducibility of the ambulatory blood pressure variables would not be different following two corresponding exercise and control treatments. A total of 18 Stage I hypertensive adults (142.1+/-3.15/91.6+/-1.80 mmHg) performed four randomized, 24 h AmBP monitoring sessions: two following a 50 min treadmill walk (50% VO(2) peak) and two on control days. Variables measured were: (1) average systolic and diastolic pressures for 24 h, daytime (06:00-22:00 h) and night time (22:00-06:00 h) and (2) systolic and diastolic load for the same time periods. Both a nonsignificant paired t-test and an excellent intraclass correlation were used to define reproducibility of the variables between the 1st and 2nd exercise trials and between the 1st and 2nd control trials. Reproducibility was found for all the control variables except for nighttime diastolic load. Reproducibility was found for all the systolic and diastolic exercise variables. Ambulatory blood pressure measurements, including average systolic and diastolic blood pressures and systolic and diastolic loads for 24 h, daytime and night time periods are reproducible following exercise.

High-dose monotherapy vs low-dose combination therapy of calcium channel blockers and angiotensin receptor blockers in mild to moderate hypertension

The objectives of the study were to compare long-acting dihydropyridine calcium channel blockers (CCBs) with angiotensin II receptor blockers (ARBs) according to the ambulatory blood pressure monitoring (ABPM) profile in stage 1 and 2 newly diagnosed hypertensives and also to evaluate the efficacy of high-dose monotherapy vs low-dose combination therapy of the two drug categories among the subjects with inadequate blood pressure (BP) control after conventional low-dose monotherapy. We obtained 24-h ABPM readings from 302 subjects with newly diagnosed stage 1 or 2 essential hypertension. The study protocol consisted of initial drug treatment with a low dose of either CCBs or ARBs. Hypertensives who did not achieve BP control were randomized to high-dose monotherapy of either category of drug or low-dose combination therapy. CCBs and ARBs in low-dose monotherapy achieved BP control in 53.8 and 55.3% of the cases, respectively. However, subjects under treatment with CCBs experienced side effects more often and required that treatment be discontinued. Hypertensives who failed to control their BP with low-dose monotherapy did significantly better with low-dose combination treatment (61.6%) than with high-dose CCBs (42.8%) or ARBs (40.5%) monotherapy (P<0.05). In terms of ABPM, low-dose combination therapy exhibited better 24-h BP profile according to trough-to-peak ratio, hypertensive burden and BP variability. In conclusion, low-dose ARBs and CCBs have a comparable effect in subjects with grade 1 and 2 arterial hypertension. In hypertensives who are not controlled by low-dose monotherapy, low-dose combination therapy proves be more efficacious than high-dose monotherapy.

The role of blood pressure variability in end-organ damage

The ultimate goal when treating high blood pressure is to reduce the incidence of end-organ damage and prevent cardiovascular disease, and thus reduce the incidence of premature death. Cuff blood pressure measurements have some prognostic value and have traditionally been used to predict the risk of end-organ damage. Such measurements, however, do not reflect accurately the 24-h mean blood pressure and hourly variations. For any value of cuff blood pressure, a lower 24-h mean blood pressure was associated with a lower prevalence and severity of end-organ damage. In the Pressioni Arteriose Monitorate E Loro Associazioni (PAMELA) study, data from 24-h ambulatory blood pressure monitoring (ABPM) were more strongly associated with prognosis than other blood pressure data. Longitudinal evidence of the clinical relevance of 24-h ABPM data in predicting cardiovascular risk is less extensive. However, results from the Study on Ambulatory Monitoring of Pressure and Lisinopril Evaluation (SAMPLE) trial show the superiority of mean 24-h, daytime and night-time blood pressures over clinic readings in predicting the regression of left ventricular mass index in treated hypertensive patients. Furthermore, a direct, positive relationship has been established between 24-h blood pressure variability and the severity and rate of progression of end-organ damage. In addition, ABPM data demonstrate that hypertensive patients who do not exhibit a nocturnal reduction in blood pressure have a higher incidence of end-organ damage. Future directions for research and treatment of hypertension will need to consider the circadian cycle of blood pressure, the effect of treatment on blood pressure variability, and the magnitude of blood pressure changes in daily life.

Methodology to determine duration of action for antihypertensive drugs

OBJECTIVE

To review and comment on methods used to assess the duration of action of antihypertensive drugs.

DATA SOURCES

A MEDLINE search (1966-June 2000) using key terms such as trough-to-peak ratio and ambulatory blood pressure monitoring was conducted.

STUDY SELECTION

An article was considered for this review if it pertained to the assessment of the duration of action of antihypertensive drugs. Special attention was given to articles dealing with methodologic aspects.

DATA SYNTHESIS

Antihypertensive drugs with a long duration of action are thought to provide better therapeutic coverage against hypertensive complications compared with that of short-acting agents. Measuring blood pressure at the end of the dosing interval may be a way to assess the duration of action of a drug. However, the use of high doses of a short-acting agent to obtain sufficient effect when at trough concentrations can potentially cause dose-related adverse effects at the peak time, contributing to nonadherence to therapy and thus to adverse outcomes. To alleviate this problem, the US Food and Drug Administration (FDA) has conceptualized the trough-to-peak (T:P) ratio. Although this arithmetic index has since been widely used to characterize the duration and safety of blood pressure control achieved by antihypertensive agents, several methodologic flaws limit its interpretation in the clinic. Ambulatory blood pressure monitoring (ABPM) is a more reliable approach to assess the duration of action and outcome of antihypertensive therapy.

CONCLUSIONS

Different methodologic approaches exist to evaluate the duration of action of antihypertensive drugs. Although the T:P ratio has been suggested by the FDA, it is difficult to establish a fair comparison among various antihypertensive agents based solely on this index. Treatment evaluation based on ABPM may be preferable to those guided by T:P because ABPM is more reproducible and is now established as a predictor of cardiovascular risk.

Comparison of angiotensin II receptor blockers: impact of missed doses of candesartan cilexetil and losartan in systemic hypertension

Blood pressure remains poorly controlled in the hypertensive population due in large part to low or unsatisfactory patient compliance. Clinical studies that incorporate an intentionally missed dose have been designed to evaluate the impact of poor patient compliance on the effectiveness of antihypertensive medications. In these studies, ambulatory blood pressure monitoring is continued throughout the dosing interval and beyond in order to determine when systolic and diastolic blood pressure increase into the hypertensive range. In an 8-week, randomized, double-blind, placebo-controlled trial in patients with mild-to-moderate hypertension, the antihypertensive effects of candesartan cilexetil 16 mg were maintained after a missed dose, whereas systolic and diastolic blood pressure increased toward baseline levels after a missed dose of losartan 100 mg. Candesartan cilexetil provided a significantly greater reduction in sitting systolic (p = 0.004) and diastolic blood pressure (p = 0.008) than losartan when measured 48 hours after the last dose. Moreover, the homogeneity of antihypertensive effects was greater after candesartan cilexetil than losartan based on calculation of the smoothness index from ambulatory systolic and diastolic measurements during the first 24-hour period after dosing and during the 12-hour period after the missed dose. These results demonstrate that missing or delaying a dose of candesartan cilexetil has less impact on antihypertensive efficacy than missing or delaying a dose of losartan.

Ambulatory blood pressure monitoring

This paper will briefly summarize the available evidence on the diagnostic and prognostic relevance of a number of parameters derived from the analysis of 24 hour ambulatory blood pressure recordings. These parameters include the 24 h average blood pressure values, the difference between daytime and nighttime blood pressure, the difference between clinic blood pressure and daytime average blood pressure as a surrogate measure of the "white coat effect", and 24 hour blood pressure variability as quantified by the standard deviation of the 24 hour average value.