Review Question - QID 100651

The most likely etiology of this man's sleeping troubles is pulmonary congestion in recumbency (orthopnea) secondary to left-sided heart failure (HF).

Left-ventricular failure is the most common cause of orthopnea. In the horizontal position there is redistribution of blood from the lower body to the lungs. In healthy people, this has little consequence, but in individuals in whom the additional volume cannot be pumped out by a diseased left ventricle, there is a reduction in pulmonary compliance and vital capacity, leading to shortness of breath.

King et al. note that there is not a sole feature on clinical history, sign, or symptom which has been shown to be diagnostic (though many are helpful in assessing the probability of heart failure). Signs included in this are dyspnea on exertion and orthopnea.

Schrier and Bansal point out that right-sided HF can occur in isolation, as seen in pulmonary hypertension and COPD. However, the most common cause of right-sided HF is left-sided HF. With right HF, right upper quadrant discomfort secondary to acute hepatic congestion and lower extremity edema are common presenting symptoms.

Illustration A is a diagram comparing right vs. left-sided HF. Illustration B shows a chest X-ray in a HF patient with pulmonary edema.
Illustration C is the Framingham diagnostic criteria for HF. Illustration D shows the pathophysiology of left ventricular failure.

Incorrect answers:
Answer 1: Obstructive sleep apnea (OSA) generally does not cause problems falling asleep; rather, a patient with OSA will have disrupted sleep due to episodes of apnea that awaken the patient.
Answer 2: Respiratory muscle weakness is usually a late complication of ALS, although patients can present with orthopnea due to diaphragmatic paralysis. However, the orthopnea would usually be accompanied by bulbar symptoms.
Answer 3: Myasthenia gravis can cause diaphragmatic weakness leading to orthopnea; however, patients usually present with with weakness in the eye muscles and bulbar muscles.
Answer 4: Isolated right-sided HF would first manifest as bilateral lower extremity edema and congestive hepatomegaly rather than orthopnea.