What is the most common cause of right heart failure?

Left heart failure is the most common cause of right heart failure. When anything causes left heart failure — ischemia, valve disease, cardiomyopathy, etc — the left ventricular pressure increases and transmits back to the lungs, causing pulmonary hypertension. This then strains the right heart and eventually causes right heart failure. Know the difference between signs/symptoms of left vs. right heart failure.