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Monday, July 12, 2010

Hypertension associated with Sleep Apnea (Apnoea)

A 48-year-old man is evaluated in the office for poorly controlled hypertension. His blood pressure has been elevated for 12 years and remains between 150/105 mm Hg and 170/105 mm Hg despite the use of multiple medications. He also has poor exercise tolerance and fatigue and often falls asleep in the afternoon. Medications are atenolol, amlodipine, and hydrochlorothiazide.

On physical examination, blood pressure is 168/110 mm Hg. He is obese (BMI 35) and appears plethoric. The remainder of the examination is normal.

Laboratory Studies
Creatinine 1.4 mg/dL
Sodium 140 meq/L
Potassium 3.9 meq/L
Bicarbonate 25 meq/L

Which of the following is the most likely cause of this patient's resistant hypertension?
A Pheochromocytoma
B Primary hyperaldosteronism
C Renovascular hypertension
D Sleep apnea syndrome

Answer and Critique (Correct Answer = D)

Key Point
Sleep apnea is associated with resistant hypertension and is particularly prevalent in obese patients.

Sleep apnea syndrome may contribute to resistant hypertension as well as to increased cardiovascular and cerebrovascular disease risk. Patients may have excessive fatigue and may fall asleep while driving or working. This condition has a higher prevalence in overweight men. The pathogenesis of sleep apnea syndrome is complex and linked to obesity, insulin resistance, and increased sodium retention. Several studies have shown that patients with sleep apnea syndrome have increased activity of the sympathetic nervous system, which also occurs in obesity. Coexistent insulin resistance and impaired glucose tolerance also may be present in these patients.

Renovascular hypertension may cause resistant hypertension but is less common than sleep apnea. In addition, the patient's age, obesity, plethora, and daytime sleepiness are more suggestive of sleep apnea than renovascular hypertension. Atherosclerotic renovascular hypertension usually develops in older patients, whereas fibromuscular dysplasia of the renal arteries often presents in younger patients and is more common in women.

Primary hyperaldosteronism may be present in as many as 10% of patients with resistant hypertension and should be included in the differential diagnosis. However, this condition is less likely in a patient who takes hydrochlorothiazide and has a normal potassium level.

Pheochromocytoma is a rare form of hypertension mediated by excess catecholamines. This condition causes palpitations, diaphoresis, tremor, flushing, and headaches. Diagnosis of pheochromocytoma may be difficult, and the clinical manifestations vary significantly. This patient's presentation is not fully consistent with this condition, and sleep apnea is more likely because it is more common and more likely to be associated with obesity, plethora, and daytime sleepiness.

1. Poirier P, Giles TD, Bray GA, Hong Y, Stern JS, Pi-Sunyer FX, Eckel RH; American Heart Association; Obesity Committee of the Council on Nutrition, Physical Activity, and Metabolism. Obesity and cardiovascular disease: pathophysiology, evaluation, and effect of weight loss: an update of the 1997 American Heart Association Scientific Statement on Obesity and Heart Disease from the Obesity Committee of the Council on Nutrition, Physical Activity, and Metabolism. Circulation. 2006;113:898-918. Epub 2005 Dec 27. [PMID: 16380542] [PubMed]

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