Cardiovascular Journal of Africa: Vol 31 No 6 (November/December 2020)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 31, No 6, November/December 2020

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AFRICA

this was more effective than ACE inhibitor-plus-thiazide

combination, although potassium needs to be monitored due

to risk of hypokalaemia. However, thiazide-like diuretics may

not be widely available, in which case a thiazide diuretic would

be used.

Importantly, the ISH guidelines stress the importance of

controlling the BP, regardless of what drugs are available for use.

They have provided alternatives to the standard first-line agents.

They have also made it clear that, while it is optimal to use SPC,

free combinations can be used in settings where SPC are limited.

It is optimal to use agents with longer half-lives that require

once-daily dosing. They recommend the use of single agents for

BP control in the setting of frail elderly patients only or in the

setting of stage 1 hypertension, where lifestyle measures have not

improved the BP to target. The long half-life of amlodipine may

make it the drug of choice in this setting, making it the preferred

choice over a diuretic.

If BP is not controlled, the initial combination must have the

dose optimised before adding a diuretic. This is an important

difference to other major guidelines. Beta-blockers are only used

for treatment of hypertension associated with specific cardiac

conditions such as heart failure, ischaemic heart disease and

atrial fibrillation.

The ISH guidelines have stressed the importance of ensuring

good adherence, as have other international guidelines. They

have highlighted means to improve adherence to antihypertensive

therapy, both essential and optimal. It is essential that adherence

to antihypertensive therapy is improved in whatever ways are

available. While it is ideal to be able to monitor adherence,

the methods available may not be feasible and have many

limitations. However, where possible, it is recommended to

monitor adherence using the best tools available/feasible in the

particular setting.

Resistant hypertension

Resistant hypertension should be suspected if office BP is >

140/90 mmHg on treatment with at least three antihypertensives

(in maximal or maximally tolerated doses), including a diuretic.

It is essential to exclude pseudo-resistance (white-coat effect,

non-adherence to treatment, incorrect BP measurements,

errors in antihypertensive therapy) and substance-induced

hypertension, such as non-steroidal anti-inflammatories

(NSAIDs) as contributors. Health behaviours and lifestyle also

need to be optimised.

If truly resistant, low-dose spironolactone is recommended,

especially if K

is < 4.5 mmol/l and eGFR is > 45 ml/min. If

this fails, then referral to a specialist or the investigation of

secondary causes is recommended under the optimal approach.

Under the essential approach, addition of other antihypertensive

medication is recommended and a screen for secondary causes

with a history, examination and basic tests, for example, thyroid-

stimulating hormone, electrolytes, creatinine and eGFR, and

dipstick urine.

Ethnic differences

In populations of African descent, hypertension and HMOD

occur at younger ages. There is greater resistance to treatment,

more nocturnal hypertension, and increased risk of kidney

disease, stroke, heart failure and mortality.

This may be

related to physiological differences in the renin–angiotensin–

aldosterone system, altered renal sodium handling, CV reactivity

and early vascular aging. These are important considerations

when treating patients from SSA. Studies done in SSA suggest

amiloride is a useful agent in controlling BP in patients with

resistant hypertension,

but amiloride is not mentioned in the

ISH guideline.

Hypertensive emergencies/urgencies

Hypertensive emergency is a severely elevated BP associated

with acute HMOD and requires immediate BP lowering,

usually with intravenous therapy. Urgency refers to severely

elevated BP without acute HMOD and can be managed with

oral antihypertensive agents. In SSA these complications of

hypertension are relatively common, but an evidence-based

approach to management is lacking.

The essential requirements are a clinical examination,

evaluation of HMOD, including fundoscopy, and the following

investigations: haemoglobin, platelets, creatinine, sodium,

potassium, lactate dehydrogenase, haptoglobin, urinalysis for

protein, urine sediment and ECG. In SSA, access to ECG

and urinary sediment is limited, and measurement of lactate

dehydrogenase and haptoglobin is unnecessary. A simple dipstick

and creatinine will alert the clinician to kidney damage, which is

the most common complication of a hypertensive emergency.

Hypertensive emergencies require immediate BP lowering to

prevent or limit further HMOD, but unfortunately there is sparse

evidence to guide management, and recommendations are largely

consensus based. The time to lower BP and the magnitude of BP

reduction depends on the clinical context, but in general a 25%

immediate reduction is recommended. Large drops in BP can

precipitate stroke due to loss of cerebral autoregulation.

The ISH guidelines recommend intravenous labetalol and

nicardipine, which are generally safe to use in all hypertensive

emergencies. However, intravenous labetalol has limited

availability in SSA and nicardipine is not listed on the WHO

essential drugs list and in 2010 was only available in Cameroon

and Senegal.

Nitroglycerine is an option, however, access to

high-care and intensive-care units is very limited. In the absence

of the above, an oral long-acting CCB

or oral labetolol is

probably the safest choice and a loop diuretic is an option in the

setting of pulmonary oedema. All patients should be followed up

and should achieve optimal BP control.

Hypertension and co-morbidities

A detailed analysis of this section is beyond the scope of the

review. In addition to BP control under optimal and essential

recommendations, effective treatment of the other risk factors to

reduce the residual cardiovascular risk is essential. Low-density

lipoprotein (LDL) cholesterol should be reduced according to

risk profile: (1) > 50% and < 1.8 mmol/l in hypertension and

cardiovascular disease (CVD), chronic kidney disease, diabetes

mellitus or no CVD and high risk; (2) > 50% and < 2.6 mmol/l in

high-risk patients; (3) < 3 mmol/l in moderate-risk patients. The

fasting serum glucose levels should be reduced below 7 mmol/l or

glycated haemoglobin (HbA

) below 7%. Serum urate should be

maintained below 0.387 mmol/l, and < 0.357 mmol/l in patients