Complications of dilated cardiomyopathy include: Heart failure. The heart can't pump enough blood to meet the body's needs. Untreated, heart failure can be life-threatening. Leaky heart valves (heart valve regurgitation). Cardiomyopathy may make it harder for heart valves to close. Blood may leak backward through a heart valve. Irregular heartbeats (arrhythmias). Changes in the heart's size and shape can interfere with the heart's rhythm. Sudden cardiac arrest. Dilated cardiomyopathy can cause the heart to suddenly stop beating. Blood clots. Pooling of blood in the left lower heart chamber can lead to blood clots. If clots enter the bloodstream, they can block blood flow to other organs, including the heart and brain. Blood clots can cause stroke, heart attack or damage to other organs. Arrhythmias can also cause blood clots.