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Essentials of Diagnosis
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- Abrupt onset of hypertension.
- Blood pressure ≥160/100 mm Hg.
- Considerable target-organ damage.
- Positive result of a highly specific diagnostic test.
- Adequate response to therapy for the specific type of secondary hypertension.
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More than 95% of Americans with hypertension have no specific cause for their elevated blood pressure (BP). It is important, however, to consider the possibility that newly diagnosed hypertension has a specific cause, for three reasons. First, BP control is often difficult to achieve in people with secondary causes of hypertension; diagnosing it early is likely to get BP to goal more quickly. Second, and particularly important in younger people, diagnosing and treating secondary hypertension will reduce the future burden of treatment (both expenditures for pills and follow-up and adverse effects of therapy) and improve the quality of life. For some secondary causes, specific and potentially curative therapy is available. Lastly, routine consideration of secondary causes when the diagnosis of hypertension is first made will ensure that at least once during the person's lifetime the possibility of secondary hypertension will be entertained. The risks and benefits of further testing can therefore be critically evaluated.
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Patients with an identifiable secondary cause of hypertension typically present with a relatively abrupt onset of symptoms (BP ≥160/100 mm Hg) and with considerable target-organ damage. They typically do not respond as well to lowering BP and to antihypertensive drug therapy as do patients with primary hypertension. The BP-lowering response to specific antihypertensive drugs may offer important clues to the presence and type of secondary hypertension; for example, patients with early renovascular hypertension often have an impressive BP-lowering response to an angiotensin-converting enzyme (ACE) inhibitor and those with bilateral adrenal hyperplasia as a cause of primary aldosteronism respond well to spironolactone, but not vice versa. The most common forms of secondary hypertension and useful tests for each will be discussed individually. The choice of tests and the order in which they are obtained depend not only on the pretest probability of the disease, but also on safety, availability, local expertise with the test, and its cost.
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Essentials of Diagnosis
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- Renovascular hypertension (RVHT) is the most common cause of secondary hypertension in the United States.
- RVHT is an elevation of blood pressure (BP) due to activation of the renin–angiotensin system in the setting of renal artery occlusive disease.
- The diagnosis of RVHT can be made only if BP improves following intervention, thereby making RVHT a retrospective diagnosis.
- The presence of anatomic renal artery stenosis (RAS) is not synonymous with RVHT.
- Progressive and occlusive renovascular disease may lead to impaired kidney function, termed “ischemic nephropathy.”
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General Considerations
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Recognition of important clinical clues for RVHT is paramount in the clinical diagnosis of this condition. RVHT probably occurs in less than 1% of unscreened patients with mild hypertension. By ...