A 72-year-old man presents to the office complaining of several weeks of worsening exertional dyspnea. ,but now he feels short ofbreath after walking 100 feet.Once recently he had felt lightheaded, as if he were about to faint while climbing a flight of stairs, but the symptom passed after he sat down. He had been having some difficulty sleep at night and has to prop himself up with two pillows. Occasionally, he wakes up at night feeling quite short of breath, which is relieved within minutes by sitting upright and dangling his legs over the bed. His feet have become swollen, aspecially by the end of the day. He denies any significant medical history, takes no medications,