Hypertension

IntroductionTop

Classically hypertension was defined as a systolic blood pressure (SBP) ≥140 mm Hg and/or diastolic blood pressure (DBP) ≥90 mm Hg.

Blood pressure (BP) can be measured in a variety of ways: in the physician’s office by a manual sphygmomanometer or an automated oscillometric monitor (attended or unattended by a clinician, averaged over 3-6 measurements), or at home using either a 24-hour ambulatory blood pressure monitor or averaged home blood pressure readings done by the patient (2 measurements taken each morning and 2 measurements taken each evening for 7 days). The numerous methods of measurements and their application to different populations generated multiple diagnostic thresholds, which may additionally differ slightly among professional bodies issuing recommendations.

In general, the threshold for initiation of antihypertensive therapy is lowered by the presence of diabetes mellitus or BP-related target organ damage (cardiovascular, cerebrovascular, renal, or peripheral vascular disease, hypertensive retinopathy). It is also lowered when the automated office blood pressure (AOBP) method is used, as it provides slightly lower BP values than those measured by a clinician (non-AOBP). For example, according to Hypertension Canada’s 2020 guidelines the diagnostic threshold for probable hypertension in patients with diabetes is based on manual in-office measurements with a cutoff value of ≥130/80 mm Hg. For those without diabetes, the in-office diagnostic threshold is BP ≥140/90 mm Hg with a sphygmomanometer or ≥135/85 mm Hg with an automated office BP cuff. The diagnosis of hypertension should then be confirmed with home-based readings, either with a 24-hour ambulatory BP monitor (demonstrating a daytime mean ≥135/85 mm Hg or 24-hour mean ≥130/80 mm Hg) or with an ambulatory average BP cuff measurement of ≥135/85 mm Hg. Full guidelines, including highlights, are available on the Hypertension Canada website (guidelines.hypertension.ca).

Target BP values: see Essential Hypertension.

Depending on etiology, hypertension is classified as:

1) Essential hypertension (>90% of cases).

2) Secondary hypertension.

Causes of secondary hypertension:

1) Kidney diseases:

a) Renal parenchymal diseases (see Renal Parenchymal Hypertension).

b) Renovascular diseases (see Renovascular Hypertension).

c) Renin-secreting tumors originating from the renal juxtaglomerular apparatus.

d) Primary sodium retention syndromes: Liddle syndrome, Gordon syndrome.

2) Endocrine diseases: Primary aldosteronism, Cushing syndrome, pheochromocytoma, thyrotoxicosis, hypothyroidism, hyperparathyroidism, carcinoid syndrome, acromegaly.

3) Coarctation of the aorta.

4) Preeclampsia or eclampsia (see Pregnancy-Related Hypertension).

5) Acute stress: Burns, alcohol withdrawal syndrome, psychogenic hyperventilation, hypoglycemia, major surgery.

6) Obstructive sleep apnea.

7) Increased intravascular fluid volume.

8) Diseases of the nervous system: Increased intracranial pressure, Guillain-Barré syndrome, quadriplegia, familial dysautonomia.

9) Drugs: Sympathomimetic agents, glucocorticoids, erythropoietin-stimulating agents, nonsteroidal anti-inflammatory drugs, calcineurin inhibitors (cyclosporine [INN ciclosporin], tacrolimus), monoamine oxidase inhibitors, oral contraceptives, herbal drugs (eg, ginseng, yohimbine).

10) Toxic substances: Amphetamines, cocaine, heavy metals, alcohol, nicotine.

Causes of isolated systolic hypertension:

1) Increased stiffness of the aorta, most often in the elderly.

2) Conditions causing increased cardiac output: Aortic regurgitation, anemia, thyrotoxicosis, Paget disease, arteriovenous fistulas.