Many surgeons will not operate surgically if the ejection fraction is not normal. The reason is that the risk is high that the left ventricle of the heart will not regain or return to nomal sufficiency (50 to 70%). But many people have a low EF and with medication can lead an almost normal tolerance for exertion, and I'm not sure how kidney disease.
The EF below 30% is heart failure range and that can cause renal failure. Early complications of cardiac insufficiency include renal vasoconstriction and the development of sodium and water retention, which are hallmarks of the very early stages of congestive heart failure. Heart failure is a physiologically delicate condition in which therapy is designed to block the sodium retention and simultaneously interrupt excessively activated neurohumoral mechanisms. Profound reduction of cardiac output and arterial hypotension in severe heart failure may lead to acute renal failure.
Control of high blood pressure and blood volume (diuretic) can preserve your left ventricle function.