Fact Sheet: Isolated Hypertension (ISH) by Dr. Peter Sleight
Peter Sleight, M.D., F.R.C.P, F.A.C.C.
Professor Emeritus of Cardiovascular Medicine
University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK
The World Hypertension League is planning a new survey on ISH in selected countries.
Definition: Systolic blood pressure > 160
mmHg with diastolic blood pressure <90-95 mmHg (more usually <90 mm Hg).
Prevalence: Strongly related to age, around 5%
in populations aged 60-69, 10% for age 70-79, and 20% aged 80+ years. It is more
common in women, especially if obese.
Pathophysiology: Rigidity and loss of elasticity
of large arteries due to aging +/ - atherosclerosis exaggerates the systolic peak
in pressure and the lack of elastic recoil in diastole reduces diastolic pressure.
This results in a wide pulse pressure and increasing impedance to left ventricular
ejection, which leads to increasing hypertrophy (LVH) and increasing shear stress
in arteries. The circulation is increasingly sensitive to sodium and fluid loading,
with exaggerated and more rapid diuresis in response.
Prognostic Importance: Although at one time it
was thought that the low diastolic pressure might be a favourable feature, it is
now realized that the reverse is the case. The presence of ISH indicates, not only
the presence of hypertension, but also the presence of diseased vessels and hence
the worse prognosis.
Importance of Treatment of ISH: Some years ago
physicians were cautious in advising treatment for ISH believing, erroneously, that
lowering pressure might compromise coronary and cerebral flow and precipitate myocardial
infarction or stroke. We now know from large randomized trials such as the Systolic
Hypertension in the Elderly Programme (SHEP), the European Working Party on Hypertension
in the Elderly (EWPHE), and the more recent SYST-EUR trial, that treatment of such
patients with ISH gives greater absolute benefits than any other group of patients
so far, with large reductions in both stroke and coronary events.
Which Drugs Are Best for Patients With ISH?:
Diuretics are without doubt the best proven drugs for the treatment of ISH. As well
as being particularly effective in elderly patients they also increase aortic compliance
and help control heart failure and reduce the risk of development of heart failure.
In comparison there is little or no evidence of benefit from beta blockers in elderly
subjects, or in patients with ISH. This was clearly seen in the MRC trial of elderly
hypertension, where diuretics were superior. I prefer potassium-sparing combinations
of a thiazide with amiloride, or a diuretic with less potassium loss and proven
increase in vascular compliance, such as indapamide, in order to reduce the metabolic
and arrhythmic side effects seen with high dose. ACE inhibitors and calcium antagonists
also increase compliance and are useful second to a diuretic when needed.
There has been some recent anxiety (from observational studies) about short acting
dihydropyridine calcium channel blockers (particularly nifedipine) increasing coronary
events, but the recent SYST-EUR trial was reassuring for nitrendipine. Longer acting
calcium blockers which do not cause reflex increases in sympathetic tone, such as
diltiazem or particularly verapamil, seem preferable.
What Target Level of BP, and What Dose of Drug?:
We now realize that diuretics have rather flat dose response curves and so start
with a low dose. Always check the standing blood pressure in patients with ISH,
to avoid too much postural drop as a result of the reduced baroreflex response in
the elderly, which may lead to falls or fractures. A target of 140 mmHg SBP when
standing is usually low enough.
The Swedish Trial in Old People (STOP Hypertension) showed benefit in patients aged
70-84 years. We have not much evidence of benefit over this age, largely because
so few patients in the late eighties or nineties have been studied in trials. However,
since they continue to be a high risk of stroke and coronary events, I continue
to advise treatment in fit, very elderly patients if the treatment is well tolerated.
Conclusions: Isolated systolic hypertension is
a common and serious condition. Do not be falsely reassured (or reassuring!) by
the low diastolic pressure. Treatment of ISH gives even better results (in reducing
stroke and coronary events) than in conventional hypertension. Treatment is important
because elderly subjects with ISH are increasing in numbers as the population ages.
Diuretics remain the first choice of treatment in these elderly people. There is
now good evidence of benefit, certainly up to the age of 84 years.