Treating hypertension in the diabetic patient: blood pressure goals and recommended drugs

It is well established that in the diabetic hypertensive patient a blood pressure lowering intervention has cardiovascular protective effects, independently of the drug used for achieving the therapeutic goal. This has been shown, for example, with the results of the SHEP Study (1), in which diabetic and non diabetic patients with isolated systolic hypertension displayed a clearcut reduction in cardiovascular mortality when blood pressure values were reduced with a thiazide diuretic, eventually combined with a beta blocking agent. This has also been shown in a number of others studies, which have demonstrated a clearcut reduction in cardiovascular complications in diabetic patients with systodiastolic or isolated systolic hypertension treated with calcium antagonists or ace-inhibitors (2-3). It thus appears that the first goal of the pharmacologic intervention is to lower blood pressure, taking into account that the benefit of the therapeutic intervention is directly related to the degree of the overall risk profile of the patient before the start of the treatment. This means that in the diabetic patient, -usually a very high risk profile- blood pressure reduction exerts extremely favourable results in reduction of both morbidity and mortality. This is further confirmed by the Syst-EUR trial, in which the antihypertensive intervention in aged diabetic individuals with isolated systolic hypertension caused a reduction in the cardiovascular risk almost double the one found in non diabetic hypertensives (2).

The 2003 Guidelines for management of hypertension issued by the European Society of Hypertension and the European Society of Cardiology (4) have clearly established that “the primary goal of antihypertensive treatment in diabetics is to lower blood pressure below 130/80 mmHg whenever possible, the optimal blood pressure being the lowest one that remains tolerated”. The above mentioned therapeutic goal is based on the results of different studies, such as the UKPDS, the HOT and the ABCD Trials (5-7), which have provided conclusive evidence on the favourable effects of “aggressive” treatment of hypertension. In the UKPDS study, the reduction in cerebrovascular events amounted to 44%, while for the HOT and ABCD studies, cardiovascular mortality and total mortality were 43 and 49% respectively. It should also be emphasised that in high risk patients as hypertensive diabetics are, a difference of even a few millimeters of mercury may greatly effect results in term of reduction in cardiovascular events. This has been shown in the HOPE study (8) and in the already quoted HOT study (6), in which the reduction in cardiovascular morbidity in the group achieving diastolic blood pressure levels of 81 mmHg was about double the one in patients with 85 mmHg. As also stressed by the ESH/ESC Guidelines, to reach the above mentioned goal, a combination of two or more drugs is most often required (4).

All antihypertensive drugs with documented efficacy may be used in the diabetic hypertensive patient, also taking into account that the first goal of treatment is to lower blood pressure and the global cardiovascular risk profile. In the case of type 1 diabetes no trial has been performed so far with the aim of 1) assessing the effect of blood pressure lowering on cardiovascular morbidity and mortality and 2) comparing the effects of different drugs on these endpoints. There is evidence, however, that in these patients diuretic or beta blocker treatment may delay the prognosis of nephropathy while in patients already displaying renal damage -documented by the presence of albuminuria- blockade of the renin-angiotensin system via ACE inhibitors appears to be the therapeutic choice capable of guaranteeing the best protection against the onset of renal dysfunction.

In contrast, a number of studies that have been reviewed recently (8) have evaluated the effects of antihypertensive drugs on cardiovascular events in type 2 diabetes. Overall it is difficult to affirm that one class of drugs is superior to the others, taking into account that only two studies have shown a superiority of ACE inhibitors (vs diuretics / beta blockers and calcium antagonists) (3,7). No difference was found between diuretics, ace inhibitors and calcium antagonists in the ALLHAT Study which enrolled a large number of hypertensive diabetics (9). The equality of different drugs, however, does not appear to include angiotensin II receptor blockers, which in the LIFE study have demonstrated a greater efficacy on cardiovascular events, cardiovascular death and total mortality than beta blockers (10). This appears to be the case also for the choice of the antihypertensive agent in patients with diabetic nephropathy in which the recommendation of obtaining a very strict blood pressure control deserves to be coupled with the need to employ drugs which effectively block the adverse effects of angiotensin II, such as ACE inhibitors and angiotensin II receptor blockers. A particular nephroprotection appears to be guaranteed by these latter drugs, as documented by the results of the RENAAL and IDNT studies (11,12).

In diabetic hypertensive patients, it can thus be recommended (4) to use all effective and well tolerated antihypertensive agents to achieve an optimal blood pressure control, ie values below 130/80 mmHg. Among the different antihypertensive drugs a particular place should be made for ace inhibitors and angiotensin II receptor blockers, taking into account the ability of these drugs to exert nephroprotection. Finally the finding of microalbuminuria in type 1 or type 2 diabetes requires the use of agents which effectively block the renin-angiotensin system.

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.