- Right heart failure is a potential complication of untreated dyspnea due to pulmonary embolism because the embolus obstructs pulmonary arteries, leading to increased pulmonary vascular resistance.
- This causes right ventricular strain and pressure overload, which may progress to right ventricular failure if the embolism is extensive or unresolved.
- The right heart is unable to effectively pump blood through the obstructed pulmonary circulation, resulting in cor pulmonale and systemic venous congestion.
- This pathophysiological mechanism is the principal reason why untreated pulmonary embolism can cause right heart failure.

Reference: Davidson’s Principles and Practice of Medicine, 24th Edition, Chapter: Disorders of the Respiratory System, Page 732.