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Figure 1 Example of exercise progression in two patients of similar age (57 and 59 years), degree of regurgitation (regurgitant volume of 77 and 78 ml/beat), and peak heart rate with exercise (156 vs. 153 beats/min). (A) Plot of peak-VO2 versus exercise time. The first patient (closed circles) displays normal functional capacity (normal peak VO2, 114% of predicted), whereas the second (open circles) has reduced functional capacity (reduced peak VO2, 68% of predicted), with plateau of O2 consumption toward the end of exercise. (B) Plot of respiratory exchange ratio (RER) versus exercise time in these two patients. Note that despite the marked differences in exercise capacity, both patients provide a maximum exercise effort with RER increasing above 1.1 (1.12 and 1.26 at peak exercise, respectively). (C) Plot of O2 pulse versus exercise time. The first patient with normal peak VO2 (closed circles) reaches a higher peak O2 pulse (18.3) versus that reached by the patient with reduced peak VO2 (open circles, 10.8) reflecting higher stroke volume with exercise. Also note the plateau in VO2 and O2 pulse in the patient with mitral regurgitation-related reduced peak VO2.
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