Ventricular failure. X-ray of the human chest showing left ventricular failure of the heart. The shadow of the heart (at centre) is partly obscured by fluid (appears opaque) which has leaked into the lungs because of increased pressure in the pulmonary veins. The left ventricle is positioned to the right of the image, that is, over the region of the left lung. In left ventricular failure, the left side of the heart fails to empty completely with each contraction or has difficulty accepting blood returning from the lungs. The lungs become congested with blood, which can in turn lead to pulmonary oedema. Heart attack or hypertension may be the cause of this condition.