A 45-year-old female with borderline hypertension and irregular pulse wakes up with breathing difficulties. What is the most likely cause?

The scenario describes a 45-year-old female with a history of borderline hypertension and an irregular pulse who wakes up with difficulty breathing. Pulmonary edema is a condition characterized by the accumulation of fluid in the lungs, which can result from heart dysfunction, particularly left-sided heart failure. Given the patient's potential background of hypertension, it's plausible that she may have developed heart-related issues leading to pulmonary edema. Symptoms of pulmonary edema often include sudden onset of shortness of breath, which may be exacerbated when the patient is lying down (orthopnea) or experienced during sleep (paroxysmal nocturnal dyspnea).

While other conditions such as pneumonia, asthma attacks, and acute coronary syndrome could potentially explain her symptoms, pulmonary edema aligns closely with her medical history and the acute presentation of breathing difficulties upon waking, indicating a likely cardiovascular origin for her symptoms.