Reporting of consistency of blood pressure control in randomized controlled trials of antihypertensive drugs: a systematic review of 1372 trial reports.

OBJECTIVE: Hypertension is a powerful treatable risk factor for stroke. Reports of randomized controlled trials (RCTs) of antihypertensive drugs rightly concentrate on clinical outcomes, but control of blood pressure (BP) during follow-up is also important, particularly given that inconsistent control is associated with a high risk of stroke and that antihypertensive drug classes differ in this regard. METHODS: We performed a systematic review of reporting of BP control in RCTs of antihypertensive drugs. We searched bibliographic databases (1950-2009) for systematic reviews of RCTs of BP-lowering and identified the main report of all trials. RESULTS: We identified 94 larger trials (>100 participants/arm, >1-year follow-up) and 1278 smaller/shorter trials. Ninety-one (96.8%) larger trials reported some data on mean BP during follow-up, but none reported effects on the consistency of control of BP over time. Although 81 (86.2%) larger trials reported group distribution of BP at baseline (usually SD), only 22 (23.4%) reported such data at any follow-up visit. Eleven (11.7%) larger trials reported group distribution of the change in BP from baseline to follow-up, but 61 (64.9%) reported no data at all on group distribution of BP at follow-up. Thirty-nine (41.5%) trials reported the proportion of patients reaching some BP target during follow-up, but no trial reported data on the consistency of control to target within individuals over time. Similar proportions were observed in the 1278 smaller/short trials. CONCLUSION: Reporting of BP control is limited in RCTs of BP-lowering drugs. We suggest reporting guidelines.

Prognostic significance of visit-to-visit variability, maximum systolic blood pressure, and episodic hypertension.

BACKGROUND: The mechanisms by which hypertension causes vascular events are unclear. Guidelines for diagnosis and treatment focus only on underlying mean blood pressure. We aimed to reliably establish the prognostic significance of visit-to-visit variability in blood pressure, maximum blood pressure reached, untreated episodic hypertension, and residual variability in treated patients. METHODS: We determined the risk of stroke in relation to visit-to-visit variability in blood pressure (expressed as standard deviation [SD] and parameters independent of mean blood pressure) and maximum blood pressure in patients with previous transient ischaemic attack (TIA; UK-TIA trial and three validation cohorts) and in patients with treated hypertension (Anglo-Scandinavian Cardiac Outcomes Trial Blood Pressure Lowering Arm [ASCOT-BPLA]). In ASCOT-BPLA, 24-h ambulatory blood-pressure monitoring (ABPM) was also studied. FINDINGS: In each TIA cohort, visit-to-visit variability in systolic blood pressure (SBP) was a strong predictor of subsequent stroke (eg, top-decile hazard ratio [HR] for SD SBP over seven visits in UK-TIA trial: 6.22, 95% CI 4.16-9.29, p<0.0001), independent of mean SBP, but dependent on precision of measurement (top-decile HR over ten visits: 12.08, 7.40-19.72, p<0.0001). Maximum SBP reached was also a strong predictor of stroke (HR for top-decile over seven visits: 15.01, 6.56-34.38, p<0.0001, after adjustment for mean SBP). In ASCOT-BPLA, residual visit-to-visit variability in SBP on treatment was also a strong predictor of stroke and coronary events (eg, top-decile HR for stroke: 3.25, 2.32-4.54, p<0.0001), independent of mean SBP in clinic or on ABPM. Variability on ABPM was a weaker predictor, but all measures of variability were most predictive in younger patients and at lower (

Effects of beta blockers and calcium-channel blockers on within-individual variability in blood pressure and risk of stroke.

BACKGROUND: Analyses of some randomised trials show that calcium-channel blockers reduce the risk of stroke more than expected on the basis of mean blood pressure alone and that beta blockers are less effective than expected. We aimed to investigate whether the effects of these drugs on variability in blood pressure might explain these disparities in effect on stroke risk. METHODS: The Anglo-Scandinavian Cardiac Outcomes Trial Blood Pressure Lowering Arm (ASCOT-BPLA) compared amlodipine-based regimens with atenolol-based regimens in 19 257 patients with hypertension and other vascular risk factors and the Medical Research Council (MRC) trial compared atenolol-based and diuretic-based regimens versus placebo in 4396 hypertensive patients aged 65-74 years. We expressed visit-to-visit variability of blood pressure during follow-up in the two trials as standard deviation (SD) and as transformations uncorrelated with mean blood pressure. For ASCOT-BPLA, we also studied within-visit variability and variability on 24 h ambulatory blood-pressure monitoring (ABPM). RESULTS: In ASCOT-BPLA, group systolic blood pressure (SBP) SD was lower in the amlodipine group than in the atenolol group at all follow-up visits (p<0.0001), mainly because of lower within-individual visit-to-visit variability. Within-visit and ABPM variability in SBP were also lower in the amlodipine group than in the atenolol group (all p<0.0001). Analysis of changes from baseline showed that variability decreased over time in the amlodipine group and increased in the atenolol group. The lower risk of stroke in the amlodipine group (hazard ratio 0.78, 95% CI 0.67-0.90) was partly attenuated by adjusting for mean SBP during follow-up (0.84, 0.72-0.98), but was abolished by also adjusting for within-individual SD of clinic SBP (0.99, 0.85-1.16). Findings were similar for coronary events. In the ABPM substudy, reduced variability in daytime SBP in the amlodipine group (p<0.0001) partly accounted for the reduced risk of vascular events, but reduced visit-to-visit variability in clinic SBP had a greater effect. In the MRC trial, group SD SBP and all measures of within-individual visit-to-visit variability in SBP were increased in the atenolol group compared with both the placebo group and the diuretic group during initial follow-up (all p<0.0001). Subsequent temporal trends in variability in blood pressure during follow-up in the atenolol group correlated with trends in stroke risk. INTERPRETATION: The opposite effects of calcium-channel blockers and beta blockers on variability of blood pressure account for the disparity in observed effects on risk of stroke and expected effects based on mean blood pressure. To prevent stroke most effectively, blood-pressure-lowering drugs should reduce mean blood pressure without increasing variability; ideally they should reduce both.

Serum urate predicts long-term risk of acute coronary events in women after a transient ischaemic attack and stroke.

BACKGROUND: Several studies have shown serum urate to be an independent risk factor for vascular disease, but others have not, although a stronger association in women than in men has been a consistent finding. Studies of stroke patients have shown possible associations between urate level and stroke severity, but there have been no large cohort studies of the effect of urate on the long-term risk of future vascular events in patients with a transient ischaemic attack (TIA) or stroke. We studied this relationship in 2 independent cohorts. METHODS: Individual data on 15,483 patient-years of follow-up from the UK-TIA trial (13,182 patient-years) and the Oxford TIA study (2,301 patient-years) were analyzed. Hazard ratios (per unit increase of baseline urate in mg/dl) for the risks of stroke and acute coronary events (ACE) were obtained from Cox models stratified by study, with and without adjustment for potential confounders. Potential interactions between urate and baseline characteristics were also assessed. RESULTS: Linear associations between urate and risk of ACE were found in both studies: pooled age- and sex-adjusted hazard ratio = 1.17, 95% CI 1.06-1.30, per unit increase of urate (p = 0.003). Sex, body mass index and previous myocardial infarction or angina were effect modifiers, but only the effect of sex remained after adjustment for other risk factors (p = 0.002), with a 5th:1st quintile hazard ratio of 4.23 (1.97-9.07, p < 0.0001) in women and 1.09 (0.70-1.71, p = 0.69) in men. These findings were consistent across the 2 studies. No associations were found between urate level and either risk or severity of stroke. CONCLUSIONS: High urate levels were independent predictors of long-term risk of ACE in women who had a TIA or stroke, but not in men, in 2 independent studies. Urate levels could be useful in identifying women at high risk of coronary events in routine practice.

Medium-term variability of blood pressure and potential underdiagnosis of hypertension in patients with previous transient ischemic attack or minor stroke.

BACKGROUND AND PURPOSE: Blood pressure (BP) is a major risk factor for stroke. However, the variability of systolic and diastolic BP (SBP and DBP) means that single measurements do not provide a reliable measure of usual BP. Although 24-hour ambulatory BP monitoring can correct for the effects of short-term variation, there is also important medium-term variability. The extent of medium-term variability in BP is most marked in patients with a previous transient ischemic attack (TIA) or stroke. We studied the potential impact of this variability on the likely recognition of hypertension. METHODS: We analyzed multiple repeated measurements of BP in 3 large cohorts with a TIA or minor stroke: the UK-TIA trial (n=2098), the Dutch TIA trial (n=2953), and the European Carotid Surgery Trial (ECST; n=2646). Regression dilution ratios and coefficients of variation were calculated for SBP and DBP from baseline and repeated measurements during the subsequent 12 months. Categorization based on single baseline measurements was also compared with categorization based on the subsequent "usual" BP. RESULTS: The correlation between measurements of BP at baseline and 3 to 5 months later was poor (R(2) from 0.17 to 0.31 for SBP and from 0.10 to 0.20 for DBP). Categorization of patients by baseline values resulted in substantial misclassification in relation to usual BP. For example, of patients with an SBP <140 mm Hg at baseline, the percentage with a usual SBP >or=140 mm Hg was 31.6% in the UK-TIA trial, 48.2% in the Dutch TIA trial, and 57.7% in the ECST. At least 3 consecutive measurements of SBP <120 mm Hg were required to be >90% certain that subsequent usual SBP would not be >or=140 mm Hg. CONCLUSIONS: Given the greater medium-term variability of BP in patients with a previous TIA or stroke than in the general population, single measurements of "normal" or "low" BP will substantially underestimate the true prevalence of hypertension.

Potential consequences for recruitment, power, and external validity of requirements for additional risk factors for eligibility in randomized controlled trials in secondary prevention of stroke.

BACKGROUND AND PURPOSE: Eligibility criteria determine the external validity (generalizability) of the results of randomized controlled trials. To increase the number of outcome events, and hence statistical power, some recent stroke prevention trials have required additional vascular risk factors for eligibility. METHODS: To assess the merits of additional eligibility criteria in stroke prevention trials, we analyzed data from 3 trials and 1 hospital-referred series of patients with a transient ischemic attack or minor ischemic stroke. Patients were stratified according to 2 sets of additional risk factors similar to those used in recent trials (MATCH, SPORTIF and PRoFESS); risk of stroke, myocardial infarction, or vascular death was calculated in relation to the number of risk factors. RESULTS: Although the observed risk during follow-up did increase with the number of risk factors present (P<0.01 for both sets), the risks in patients with > or =1 risk factors were not substantially greater than those in all patients. Consequently, although the proportions of patients with no risk factors in the 4 cohorts differed substantially between the 2 sets of eligibility criteria (21% to 28% versus 56% to 73%), in neither case could their exclusion be justified on statistical grounds. CONCLUSIONS: The degree of patient selection introduced by use of additional vascular risk factors as eligibility criteria for trials can differ substantially between apparently similar sets of risk factors. Given that the potential for additional eligibility criteria to undermine generalizability and prolong recruitment outweighs any benefits in terms of statistical power, the exclusion of patients with no risk factors is difficult to justify.

Treating individuals 3: from subgroups to individuals: general principles and the example of carotid endarterectomy.

Clinicians often have to make treatment decisions based on the likelihood that an individual patient will benefit. In this article we consider the relevance of relative and absolute risk reductions, and draw attention to the importance of expressing the results of trials and subgroup analyses in terms of absolute risk. We describe the limitations of univariate subgroup analysis in situations in which there are several determinants of treatment effect, and review the potential for targeting treatments with risk models, especially when benefit is probably going to be dependent on the absolute risk of adverse outcomes with or without treatment. The ability to systematically take into account the characteristics of an individual patient and their interactions, to consider the risks and benefits of interventions separately if needed, and to provide patients with personalised estimates of their likelihood of benefit is shown using the example of endarterectomy for symptomatic carotid stenosis.

Fibrinogen concentration and risk of ischemic stroke and acute coronary events in 5113 patients with transient ischemic attack and minor ischemic stroke.

BACKGROUND AND PURPOSE: Fibrinogen is an independent risk factor for coronary events in population-based studies and in patients with coronary heart disease, but there is uncertainty about prediction of stroke, particularly in secondary prevention. METHODS: We studied unpublished data from 3 prospective studies of patients with recent transient ischemic attack (TIA) or minor ischemic stroke: the United Kingdom TIA Aspirin (UK-TIA) trial (n=1860); the Dutch TIA trial (n=2960); and the Oxford TIA Study (n=293). By separate and pooled analysis, we used Cox models to determine the relationship between fibrinogen and risk of ischemic stroke and other vascular events during 23,272 patient-years of follow-up and adjusted for other risk factors. RESULTS: There was no significant heterogeneity in fibrinogen risk associations between studies. Fibrinogen predicted subsequent ischemic stroke, with a pooled hazard ratio (HR) for values above the median of 1.34 (95% CI, 1.13 to 1.60; P=0.001). The association tended to be stronger in patients with nonlacunar (HR=1.42; 95% CI, 1.13 to 1.78; P=0.002) than lacunar syndromes (HR=1.09; 95% CI, 0.80 to 1.49; P=0.58), but was not significantly so (P=0.18). There was no association with hemorrhagic stroke (adjusted HR=1.09; 95% CI, 0.55 to 2.17; P=0.81). Fibrinogen predicted acute coronary events (adjusted HR=1.42; 95% CI, 1.18 to 1.70; P<0.001) and all ischemic vascular events (adjusted HR=1.31; 95% CI, 1.15 to 1.49; P<0.001), but not nonvascular death (adjusted HR=1.24; 95% CI, 0.90 to 1.70; P=0.19). CONCLUSIONS: In patients with a previous TIA or ischemic stroke, risks of recurrent ischemic stroke and acute coronary events increase linearly with fibrinogen levels, but the relationships are weaker than in some previous population-based studies.

Pulse pressure is independently associated with carotid plaque ulceration.

BACKGROUND: Plaque rupture is the principal cause of acute coronary ischaemia, and unstable carotid plaques are associated with a high risk of ischaemic stroke. Carotid plaque ulceration also predicts acute coronary events, suggesting that systemic factors may determine plaque instability. One potentially important factor is pulse pressure. There is indirect evidence that cyclical haemodynamic forces affect plaque stability, and pulse pressure is a strong predictor of coronary events. OBJECTIVE: To study the association between pulse pressure and plaque ulceration. DESIGN AND METHODS: We studied angiograms from 3007 patients with recently symptomatic carotid stenosis in the European Carotid Surgery Trial. Presence of ulceration was related to the different components of blood pressure [pulse pressure, systolic blood pressure (SBP), mean arterial pressure (MAP), and diastolic blood pressure (DBP)], and adjustment was made for age, sex, diabetes, smoking, and the degree of vessel stenosis. RESULTS: Pulse pressure was the strongest independent predictor of ulceration of the symptomatic carotid plaque [adjusted odds ratio (OR) for the upper compared with the lower quintile 2.07, 95% confidence interval (CI) 1.25 to 3.44; P = 0.004]. This relationship was weaker for SBP (OR 1.66, 95% CI 1.05 to 2.62; P = 0.02), and non-significant for MAP (OR 1.58, 95% CI 1.01 to 2.48, P = 0.13) and DBP (OR 1.67, 95% CI 0.73 to 1.87, P = 0.50). CONCLUSIONS: Pulse pressure is independently associated with carotid plaque ulceration, supporting the hypothesis that pulsatile haemodynamic forces are an important cause of plaque rupture.