A right-sided heart failure is heart failure caused by damage to the heart's right-sided chambers. This can occur as a result of pulmonary hypertension or left-sided heart failure. When the left ventricle fails, increased fluid pressure is in effect transferred back through the lungs, ultimately damaging the heart's right side. When the right side loses pumping power, blood backs up in the body's veins. This usually causes increase pressure in the neck veins and swelling in the legs and ankles.