Uncontrolled hypertension is associated with increased incidence of target end-organ damage. The brain, heart, eyes and kidneys have been identified as the organs that are highly susceptible to damage by the effects of raised blood pressure resulting in stroke, myocardial infarction, congestive cardiac failure and renal failure as well as an increased mortality from these conditions.4,11,21 As mentioned earlier, hypertension is basically asymptomatic until target end-organ damage sets in.11
2.9.1 The Renal System
Arteriolosclerotic lesions of the afferent and efferent arterioles and the glomerular capillary tufts are the most common renal vascular lesions in hypertension, and they result in a decreased glomerular filtration rate and tubular dysfunction.
Proteinuria and microscopic haematuria are a consequence of glomerular lesion21. Adelekun and Akinsola looked at hypertension-induced chronic renal failure among some patients with the established disease in order to identify some clinico-pathological features that may help in identifying this condition early. They identified nocturia as a symptom that preceded
25
other symptoms of chronic renal failure in all cases and hence, could be used to predict the onset of renal insufficiency41
They concluded with a recommendation for the institution of a program for blood pressure screening at primary health care level and the development of an aggressive regimen for the control of elevated blood pressure so as to reduce the number of hypertension-induced chronic renal failure, and those requiring renal replacement therapy41.
2.9.2 The Cardiovascular System
Cardiovascular morbidity and mortality are substantially higher in hypertensive patients, compared with normotensive patients, at all ages and in both sexes.42The presence of mild hypertension is also a powerful predictor of progression to more severe elevations42.
Hypertension may lead to left ventricular hypertrophy as a result of an increased after-load. This will ultimately lead to left ventricular failure. Another important complication which is responsible for a larger proportion of the morbidity and mortality from the cardiovascular complications of hypertension is coronary artery disease, the ischaemic effects of which usually results in myocardial infarction. Other complications include aortic aneurysm and aortic dissection.11, 21
2.9.3 The Central Nervous System
Central nervous system effects include occipital headache which occurs mostly in the morning, and is among the prominent early symptoms. Others include dizziness, light-headedness, vertigo, tinnitus, visual blurring or syncope. Hypertension could result in a cerebrovascular disease or stroke which is defined as focal or global neurological deficit lasting
26
more than 24 hrs. The symptoms develop rapidly and are maximal within a few minutes, lasting for more than 24 hours and may result in death. Another possible central nervous system complication is subarachnoid haemorrhage which could be from a ruptured berry aneurysm, resulting in focal neurological signs.
Severe hypertension could result in hypertensive encephalopathy which is characterized by a very high blood pressure and the presence of neurological symptoms such as transient disturbances of speech or vision, paraesthesia, disorientation, fits and loss of consciousness.
Papilloedema may also be present. These signs of neurological deficit usually reverse with proper control of the hypertension21, 43
Adelekun and Akinsola also identified throbbing headache with visual blurring as common among the hypertensive patients, with the significance of these symptoms lying in their use for predicting the onset of accelerated hypertension.41
Dementia and cognitive impairment are central nervous system complications that can also occur in patients with hypertension42. In a study in which some of the participants were followed up for about 20 years, it was found that high blood pressure was linked to a decline in cognitive function in otherwise healthy people aged 18 - 46 years, as well as those older42. However, reduced progression was seen to occur with effective treatment. Imarhiagbe, Ogunrin and Ogunniyi conducted a case-control study to determine the role of hypertension in the cognitive performances of elderly Nigerian hypertensive patients and found a negative correlation only between diastolic blood pressure and cognitive performance of the hypertensive patients.44
2.9.4 The retina
27
This usually undergoes vascular and neurological changes as a result of long standing severe hypertension. Focal spasms, thickening of the walls of the retinal arterioles causing progressive diffuse or segmental arteriolar narrowing and some arterio-venous nipping, flame-shaped retinal haemorrhages, soft (cotton-wool) and hard exudates and papilloedema are lesions that could occur, resulting in visual blurring, scotomata, and possibly blindness. There is little effect on visual acuity in early hypertensive retinopathy. This is what makes early detection difficult. However subsequent production of extensive soft and hard exudates and haemorrhages can result in visual defects and possible blindness if the macula is affected21, 43
The Keith-Wagener classification of retinal changes in hypertension is used to evaluate and monitor the retina for these lesions (Appendix ii) 43.
2.9.5 Sexual Dysfunction
Sexual dysfunction has also been identified as a complication of hypertension. It manifests as erectile dysfunction in men and reduced desire for sexual intercourse in females.3, 45,
46 However, it has also been widely recognized and proven to be a side-effect of a number of anti-hypertensive medications, notable among which are α-methyldopa and thiazide diuretics.
Oke and Mbakwem in a case-control study on male hypertensive patients reported an increased incidence of erectile dysfunction in the hypertensive population compared with the controls.45In a related case-control study by Okeahialam and Obeka, an attempt was made to determine the existence of sexual dysfunction among women as has been widely reported in males. The study was done as part of a larger study on serum uric acid and lipid profile of adult Nigerian hypertensives. The study identified a reduced desire for sexual intercourse in female
28
hypertensive patients. They concluded that there was a tendency for hypertensive women to have more sexual dysfunction than did controls.46