Secondary hypertension

While most forms of hypertension have no known underlying cause (and are thus known as "essential hypertension" or "primary hypertension"), in about 10% of the cases, there is a known cause, and thus the hypertension is secondary hypertension (or, less commonly, inessential hypertension).

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Types

Renovascular hypertension (I15.0)

• See main article at Renovascular hypertension.

Hypertension secondary to other renal disorders (I15.1)

• Chronic renal failure
• Kidney disease / renal artery stenosis: the normal physiological response to low blood pressure in the renal arteries is to increase cardiac output (CO) to maintain the pressure needed for glomerular filtration. Here, however, increased CO cannot solve the structural problems causing renal artery hypotension, with the result that CO remains chronically elevated.
• Renal segmental hypoplasia (Ask-Upmark kidney)

Hypertension secondary to endocrine disorders (I15.2)

• Pheochromocytoma
• Hyperaldosteronism (Conn's syndrome)
• Cushing's disease
• Hyperparathyroidism
• Acromegaly
• Hyperthyroidism
• Hypothyroidism

Other secondary hypertension (I15.8)

• Obstructive sleep apnea
• Liquorice (when consumed in excessive amounts)
• Scleroderma
• Neurofibromatosis
• Pregnancy: unclear etiology.
• Cancers: tumours in the kidney can operate in the same way as kidney disease. More commonly, however, tumors cause inessential hypertension by ectopic secretion of hormones involved in normal physiological control of blood pressure.
• Drugs: In particular, alcohol, nasal decongestants with adrenergic effects, NSAIDs, MAOIs, adrenoceptor stimulants, and combined methods of hormonal contraception (those containing ethinyl-estradiol) can cause hypertension while in use.
  • Heavy alcohol use
  • Steroid use
• Malformed aorta, slow pulse: these cause reduced blood flow to the renal arteries, with physiological responses as already outlined.
  • Aortic valve disease: unclear etiology.
  • Coarcation of the aorta
• Anemia: unclear etiology.
• Fever: unclear etiology.

Diagnosis

The ABCDE mnemonic can be used to help determine a secondary cause of hypertension

• A: Accuracy, Apnea, Aldosteronism
• B: Bruits, Bad Kidney
• C: Catecholamines, Coarctation of the Aorta, Cushing's Syndrome
• D: Drugs, Diet
• E: Erythropoietin, Endocrine Disorders ^[1]

Laboratory Tests

• Urinalysis
• Complete blood count
• Blood chemistries (potassium, sodium, creatinine, fasting glucose)
• Fasting lipid profile (LDL, HDL, triglycerides, total cholesterol)
• 12-lead electrocardiogram ^[2]
• ABPM (ambulatory blood pressure monitoring) (in the routine evaluation and management of children with hypertension) ^[3]

Children with secondary hypertension were found to have significantly higher diastolic BP loads during both the daytime and nocturnal portions of the ABPM studies and also a significantly greater nocturnal systolic BP load, compared with children with primary hypertension. ^[3]

Risk Factors

• Poor response to therapy (resistant hypertension)
• Worsening of control in previously stable hypertensive patient
• Stage 3 hypertension (systolic blood pressure > 180 mm Hg or diastolic blood pressure >110 mm Hg)
• Onset of hypertension in persons younger than age 20 or older than age 50
• Significant hypertensive target organ damage
• Lack of family history of hypertension
• Findings on history, physical examination, or laboratory testing that suggest a secondary cause ^[4]

Goals

The sixth report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC-VI) defines four goals for the evaluation of the patient with elevated blood pressure:

• detection and confirmation of hypertension;
• detection of target organ disease (e.g., renal damage, congestive heart failure);
• identification of other risk factors for cardiovascular disorders (e.g., diabetes mellitus, hyperlipidemia);
• detection of secondary causes of hypertension.

References