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Physician Assistant Exam: Resistant Hypertension

Hypertension comes in two types and both are covered on the Physician Assistant Exam. The first is the essential, or run-of-the-mill, hypertension. The second type of hypertension is resistant hypertension, which refers to high blood pressure that’s resistant to treatment using environmental and lifestyle measures.

The following case scenarios are indicative of resistant hypertension:

  • Anyone less than 18 or more than 65 years of age who develops acute uncontrolled blood pressure when it was previously controlled or wasn’t even an issue

  • Anyone whose blood pressure is still difficult to control, despite being on three or more optimally dosed, antihypertensive medications, usually including a diuretic

You should be familiar with the causes discussed here in terms of identification, evaluation, and management.

Chronic kidney disease

The most common cause of resistant hypertension is chronic kidney disease. Hypertension and diabetes mellitus are the two leading causes of chronic kidney disease. You should check a blood urea nitrogen and serum creatinine level to look for evidence of intrinsic renal parenchymal disease.

Renal artery stenosis

Renovascular disease, especially renal artery stenosis, is a common cause of resistant hypertension. The most common cause of renal artery stenosis is atherosclerosis at the proximal ostium of the renal artery — right where it branches off of the big trunk known as the aorta. The renal artery becomes narrow enough to cause high blood pressure.

Here are three key points about identifying renal artery stenosis:

  • You may hear an audible flank or abdominal bruit, usually with the bell of the stethoscope.

  • With an initial presentation of renal artery stenosis, you may see flash pulmonary edema, with normal heart function and patent coronary arteries.

  • Acute renal failure, hypotension, and/or hyperkalemia after the use of an ACE inhibitor is a tipoff that renal artery stenosis is likely present. When the artery is really narrow, it becomes dependent on the blood pressure hormone angiotensin for renal perfusion. Block this hormone in someone with renal artery stenosis, and the person can get acute renal failure and hyperkalemia.

The gold standard for diagnosis of renal artery stenosis is the angiogram.

Treatment for renal artery stenosis is somewhat controversial. Certainly angioplasty and stent placement together is one recommended treatment. Studies show that angioplasty with or without stenting is safe and effective, but a number of trials don’t demonstrate improvement in blood or renal function. Recognize angioplasty with or without stenting as a treatment option.

Hyperaldosteronism

You see hyperaldosteronism with new onset hypertension and low potassium. The potassium stays low despite replacement, and the high blood pressure is resistant to treatment. The initial screening for hyperaldosteronism involves obtaining two blood tests, namely an aldosterone level and a renin level. The aldosterone/renin ratio confirms the diagnosis. For hyperaldosteronism, the aldosterone level is usually greater than 16, and the renin level is suppressed, usually unmeasurable.

If those blood tests suggest that hyperaldosteronism may be present, the next step is to order a CT scan of the abdomen and pelvis to look at the adrenal glands. The most common cause is adrenal adenoma, and the second most common cause is bilateral adrenal hyperplasia. The treatment for adenoma may be surgical removal, depending on the size of the adenoma.

The treatment for bilateral adrenal hyperplasia is to block aldosterone secretion using an aldosterone blocker like spironolactone. A major side effect is hyperkalemia.

Pheochromocytoma

Pheochromocytoma is usually an adrenal-producing tumor that can cause refractory labile hypertension. The blood pressure can be refractory to treatment, or it can be very labile, either super high or super low. The initial screening is biochemical, comprising urinalysis and blood testing. Here are some high-yield points about pheochromocytoma:

  • The screening tests include a plasma metanephrines and/or a 24-hour urinary collection for vanillylmandelic acid and urinary metanephrines. The metanephrines test is the more sensitive test.

  • If the metanephrines are elevated, then obtain a CT scan to look at the adrenal glands for an adrenal adenoma. A more sensitive study may be needed to help establish the diagnosis.

  • Remember the 10 percent rule: The pheochromocytma is familial 10 percent of the time, extra-adrenal 10 percent of the time, malignant 10 percent of the time, and present in both adrenal glands 10 percent of the time.

Coarctation of the aorta

Coarctation of the aorta is a common congenital pediatric cause of hypertension. With this condition, narrowing of the aorta causes a difference in the blood pressures between the upper and lower extremities. The area affected is the ductus arteriosus.

A classic physical exam finding is radial-femoral delay, meaning that there’s a significant delay between the radial and the femoral pulses. The upper torso is highly vascularized, and the legs can be small and spindly. Depending on the degree of narrowing, the lower-extremity pulses may not be palpable at all.

Here are some other key points:

  • Initial presentation can include claudication-type symptoms, similar to what you see in older adults with really bad peripheral vascular disease

  • Upper-extremity hypertension and lower-extremity hypotension with decreased palpable pulses is typical for this condition.

  • Treatment can be conservative or involve surgery of the stenosed area.

  • A figure-three sign and scalloped ribs are classic signs on radiograph.

Other causes of resistant hypertension include Cushing’s syndrome, carcinoid syndrome, obesity, and obstructive sleep apnea.

Which of the following is the most common cause of secondary hypertension?

(A) Carcinoid syndrome
(B) Renal artery stenosis
(C) Chronic kidney disease (CKD)
(D) Hyperaldosteronism
(E) Obstructive sleep apnea

The correct answer is Choice (C). The most common cause of resistant hypertension is actually intrinsic renal parenchymal disease. The second most common cause is Choice (B), renal artery stenosis. Choice (E), obstructive sleep apnea, is probably the least-recognized cause of refractory hypertension.

Carcinoid syndrome, Choice (A), can be a cause of refractory hypertension where the carcinoid tumor secretes serotonin. Choice (D), hyperaldosteronism, is a cause of refractory hypertension and hypokalemia but isn’t the most common cause of resistant hypertension.

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