Investigations for HTN

Lab test

· Serum urea, creatinine, electrolyte levels

· Blood glucose levels

· Lipid profile

· Urinalysis for proteinuria & heamaturia

· Echocardiogram

Imaging

· Chest X-ray

· Echocardiogram

These are routine investigations for essential hypertension used to assess the overall level of CV risk and to look for evidence of end organ damage.

Urinalysis is important as proteinuria is a sensitive marker of early hypertensive renal damage and may also be associated with an increase in plasma urea and creatinine levels. Microscopic haematuria can be seen in hypertensive renal disease but not as good as an indicator of the disease as presence of proteinuria. However, heamaturia may be seen in some forms of glomerulinephritis and would suggest an underlying cause for hypertension.

Electrocardiogram is used to screen for left ventricular hypertrophy (LVH) and may show evidence of underlying ischaemia, previos MI and presence of arrhythmias.

Echocardiography is indicated if there is suspicion of LVH or end organ damage.

Chest X-ray is not routinely indicated in hypertensive patients unless there is evidence of underlying respiratory disease, heart failure or secondary cause like coarctation of the aorta (narrowing of the aorta).

If secondary cause is suspected then further investigations are carried out based on underlying causes:

· Renal artery stenosis (most common cause)-renal artery magnetic resonance image scan/angiography.

· Coarctation of aorta-Angiography

· Hypothyroidism-Thyroid fx test

· Phaeochromocytoma (neuroendocrine tumor of the medulla of the adrenal glands)-Plasma catecholamine levels, 24-hour urinary catecholamine levels, nuclear scan

· Cushing’s syndrome (hormone disorder caused by high levels of cortisol in the blood)-cortisol levels, dexamethasone suppression test*, abdominal computed tomography scan.

· Conn’s disease (high levels of aldosterone)-24 hour aldosterone level test

Dictionary

1. Angiography-Angiography is an X-ray exam of the arteries and veins to diagnose blockages and other blood vessel problems.

2. Nuclear scan-A radiotracer is injected into a peripheral vein. As the radiotracer decays, gamma radiation is emitted and is detected by a Gamma camera. When the tracer has collected in the target organ the area is scanned. Radionuclide scans can detect abnormalities such as fractures, bone infections, arthritis, rickets, and tumors that have spread, among other diseases.

3. Catecholamine-Small molecules made by nerve tissue (including the brain) and the adrenal gland. The major catecholamines are dopamine, norepinephrine, and epinephrine. These substances break down into other compounds, which leave your body through your urine.

4. Aldosterone- produced by the adrenal glands in response to angiotensin II, it affects the amount of sodium, potassium, and fluids excreted by the kidneys.

5. Dexamethasone suppression test-measures response of adrenal glands to ACTH.Dexamethasone is a human-made (synthetic) steroid that is similar to cortisol. It reduces ACTH release in normal people. Therefore, taking dexamethasone should reduce ACTH levels and lead to decreased cortisol levels.

6. Pheochromocytoma- rare catecholamine-secreting tumor derived from chromaffin cells in the adrenal gland, usually benign.