LV diastolic function assessed by invasive cardiopulmonary exercise testing. The key is the same as in Fig. 4. The pressure-volume relationship was shifted upward and leftward at rest. In the patients undergoing exercise testing, LV diastolic volume did not increase despite the marked increase in diastolic (pulmonary wedge) pressure. Because of diastolic dysfunction, failure of the Frank-Starling mechanism resulted in severe exercise intolerance. (From Kitzman DW, Higginbotham MB, Cobb FR, et al. Exercise intolerance in patients with heart failure and preserved left ventricular systolic function: failure of the Frank-Starling mechanism. J Am Coll Cardiol 1991;17:1065-72; with permission. Copyright © 1991, American College of Cardiology.)