Stroke prevention with blood pressure control
Hypertension is defined as a systolic blood pressure of 140 mmHg or greater and/ or a diastolic blood pressure of 90 mmHg or greater in persons who are not taking any medication against high blood pressure (Table 13.1). This condition affects millions of men and women and its prevalence in the general population ranges between 20 and 40% (Davis et al., 1987; Collins et al., 1990; Bonita et al., 1992; Mulrow et al., 1998; Colhoun et al., 1998; Chamontin et al., 1998). Hypertension has been recognised as the most prevalent and modifiable risk factor for stroke (Dawber, 1980; Kalache and Aboderin, 1995) and is associated with other major cardiovascular diseases such as myocardial infarction, and cardiovascular mortality (MacMahon et al., 1990). Both systolic (SBP) and diastolic (DBP) blood pressure levels have been shown to be positively related to the risk of stroke (MacMahon and Rodgers, 1994a; Eastern Stroke and Coronary Heart Disease Collaborative Research Group, 1998). Interestingly, blood pressure levels are continuously related to the risk of stroke (Figure 13.1) and numerous blood pressure-related events occur in persons who would normally be considered as normotensive. However, recent reassessment of epidemiologic data has questioned this relationship and proposed age-and sex-dependent thresholds for hypertension (Port, 2000). The treatment of hypertension substantially reduces the risk of stroke (Gorelick et al., 1999). Although most of the evidence on the efficacy of antihypertensive drugs to reduce the incidence of stroke (see below) comes from trials in patients selected on the basis of their high blood pressure, treatment effects from these trials can be extrapolated to individuals with lower blood pressure levels. Thus, the recent HOPE trial (HOPE Study, 2000) has shown that this risk of stroke can be reduced in normotensive individuals with the administration of a blood pressure lowering drug. Indeed, this study has enrolled patients with a high cardiovascular risk, defined as patients with evidence of vascular disease or diabetes plus any other
cardiovascular risk factor, such as smoking or elevated cholesterol level but not necessarily hypertensive. The goal of this study was to assess whether these patients could benefit from a decrease in blood pressure with an angiotensin converting enzyme (ACE) inhibitor, ramipril.