Question

A $69$-year-old man comes to the clinic with progressively worsening lower extremity edema, fatigue, and exertional dyspnea over the last three months. He has a $50$-pack-year smoking history and was diagnosed with severe chronic obstructive pulmonary disease (COPD) four years ago. He is compliant with his long-acting muscarinic antagonist and beta-agonist inhalers. Vital signs show a blood pressure of $132/84\text{ mmHg}$, pulse of $88\text{/min}$, and respirations of $18\text{/min}$. Oxygen saturation is $91\%$ on room air. Physical examination shows a barrel-shaped chest with decreased breath sounds bilaterally. The jugular venous pressure is elevated at $12\text{ cm H}_2\text{O}$. Heart sounds are distant, but a regular rhythm is appreciated. Abdominal examination shows hepatomegaly. There is $2+$ pitting edema extending to the knees bilaterally. The physician is trying to determine if the patient has developed concurrent left ventricular failure or if his symptoms are solely due to cor pulmonale from his severe COPD. Which of the following findings on further evaluation would most strongly indicate the presence of concurrent left-sided heart failure rather than isolated cor pulmonale?