Cardiovascular Journal of Africa: Vol 32 No 6 (NOVEMBER/DECEMBER 2021)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 32, No 6, November/December 2021 AFRICA 319 Lowering blood pressure significantly reduces cardiovascular risk even at normal levels Even in those with normal or only mildly elevated blood pressure, antihypertensive medication for lowering of blood pressure protects against future cardiovascular events, found a large meta-analysis in The Lancet . A 5-mmHg reduction of systolic blood pressure reduced the risk of major cardiovascular events by about 10%, irrespective of previous diagnoses of cardiovascular disease, and even at normal or high-normal blood pressure values. ‘The take-home message is that pharmacological blood pressure lowering should be considered as a tool for cardiovascular risk management even when blood pressure is normal or mildly elevated, for primary and secondary prevention of cardiovascular disease,’ said lead investigator Dr Kazem Rahimi, University of Oxford. ‘The advice to patients with normal blood pressure and high cardiovascular disease risk is that they are likely to benefit from taking one or several antihypertensive medications to reduce their risk of suffering a major cardiovascular event in the future,’ Rahimi added. For this analysis, Rahimi and colleagues looked at individual participant-level data from 48 randomised antihypertensive treatment trials. Participants were divided into seven subgroups based on systolic blood pressure baseline (less than 120, 120–129, 130–139, 140–149, 150–159, 160–169, 170 and above mmHg). The analysis included 344 716 patients with ≥ 1 000 patient-years per allocated group. Over an average four years of follow up, a 5-mmHg reduction in systolic blood pressure lowered the relative risk for major cardiovascular events by about 10%. The risks for stroke, heart failure, ischaemic heart disease, and death from cardiovascular disease were reduced by 13, 13, 8 and 5%, respectively. The relative risk reductions were proportional to the intensity of blood pressure lowering. Neither the presence of cardiovascular disease nor the level of blood pressure at study entry modified the effect of treatment. ‘This study calls for a change in clinical practice that predominantly confines antihypertensive treatment to people with higher-than-average blood pressure values,’ Rahimi and colleagues write. ‘On the basis of this study, the decision to prescribe blood pressure medication should not be based simply on a previous diagnosis of cardiovascular disease or an individual’s current blood pressure. Rather, blood pressure medication should be viewed as an effective tool for preventing cardiovascular disease when an individual’s cardiovascular risk is elevated,’ they say. In a linked editorial, Dr Thomas Kahan, Karolinska Institute, Stockholm, Sweden, writes that ‘the study by the Blood Pressure Lowering Treatment Trialists’ Collaboration (BPLTTC) represents the largest meta-analysis so far of individual participant-level data for the effects of antihypertensive treatment stratified by initial blood pressure and prevalent cardiovascular disease. The results showed that the benefit of antihypertensive drug treatment is proportional to the intensity of blood pressure reduction, and that the magnitude of relative (and absolute) risk reduction is similar across baseline systolic blood pressure levels from less than 120 mmHg to more than 170 mmHg, extending observations from epidemiological studies.’ ‘In agreement with previous reports, antihypertensive treatment appears to reduce incident stroke and heart failure by a greater extent than ischaemic heart disease. However, the reported benefit at low-entry systolic blood pressure in patients with a high proportion (75%) of ischaemic heart disease suggests that the risk of blood pressure lowering in this group of patients (i.e. a J-curve for risk) might not be a problem in most patients. ‘Of note, this systematic review could not include all eligible trials, which is an inherent limitation of all individual participant data meta-analyses. However, the investigators assessed the risk of acquisition bias, and also did sensitivity analyses excluding trials, without important effects on their findings. The findings might not be generalisable to patient groups with concomitant conditions not studied in these analyses (e.g. heart failure). continued on page 326 … 36. Ale OK, Ajuluchukwu JNA, Oke DA, Mbakwem AC. QT dispersion in hypertensive Nigerians with and without left ventricular hypertrophy. West Afr J Med 2013; 32 (1): 58–61. 37. 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