What is the most likely diagnosis?What conditions should be included in the differential diagnosis?

A 63-year-old woman with a history of diabetes mellitus and hypertension presents to
the emergency department complaining that she feels short of breath. She reports that
she began having diffi culty breathing over the past week, which has progressed to the
point that she can no longer walk up one fl ight of stairs without feeling short of breath.
She was previously able to walk fi ve blocks before becoming short of breath. She denies
any history of heart or lung disease, cough or hemoptysis, chest pain, swelling of the
extremities, or fever. She takes no medication. Vitals signs include a temperature of
37.0°C (98.6°F), blood pressure of 170/90 mm Hg, pulse rate of 95/min, respiratory
rate of 22/min, and oxygen saturation of 92% on room air. Physical examination reveals
that her lungs have crackles at the bases bilaterally, and her cardiac examination reveals
a point of maximum impulse at the sixth intercostal space at the midaxillary line.
There is no clubbing, cyanosis, or edema of the extremities. X-ray of the chest reveals
perivascular haziness, interstitial edema, and an enlarged cardiac silhouette.