Decreased CO can be caused by Cardiac disorders that obstruct outflow Cardiac disorders of systolic dysfunction Cardiac disorders of diastolic dysfunction Arrhythmias (too fast or too slow) Conditions that decrease venous return Outflow obstruction can be exacerbated by exercise, vasodilation, and hypovolemia (particularly in aortic stenosis and hypertrophic cardiomyopathy), which may precipitate syncope.