Upright graded cycle exercise at 75-W revealed significantly lower stroke volume in POTS patients compared to healthy controls (70 vs 94 ml, P<0.01), driving excessive tachycardia.
Case-Control (n=23)
Does cardiovascular regulation during exercise differ between POTS patients and healthy controls?
In patients with POTS, the greater elevation in heart rate during exercise, especially while upright, appears secondary to reduced stroke volume and is associated with exercise intolerance.
Absolute Event Rate: 70% vs 94%
p-value: p=<0.01
Postural tachycardia syndrome (POTS) is characterized by excessive tachycardia without hypotension during orthostasis. Most POTS patients also report exercise intolerance. To assess cardiovascular regulation during exercise in POTS, patients (n = 13) and healthy controls (n = 10) performed graded cycle exercise at 25, 50, and 75 W in both supine and upright positions while arterial pressure (arterial catheter), heart rate (HR; measured by ECG), and cardiac output (open-circuit acetylene breathing) were measured. In both positions, mean arterial pressure, cardiac output, and total peripheral resistance at rest and during exercise were similar in patients and controls (P > 0.05). However, supine stroke volume (SV) tended to be lower in the patients than controls at rest (99 +/- 5 vs. 110 +/- 9 ml) and during 75-W exercise (97 +/- 5 vs. 111 +/- 7 ml) (P = 0.07), and HR was higher in the patients than controls at rest (76 +/- 3 vs. 62 +/- 4 beats/min) and during 75-W exercise (127 +/- 3 vs. 114 +/- 5 beats/min) (both P < 0.01). Upright SV was significantly lower in the patients than controls at rest (57 +/- 3 vs. 81 +/- 6 ml) and during 75-W exercise (70 +/- 4 vs. 94 +/- 6 ml) (both P < 0.01), and HR was much higher in the patients than controls at rest (103 +/- 3 vs. 81 +/- 4 beats/min) and during 75-W exercise (164 +/- 3 vs. 131 +/- 7 beats/min) (both P < 0.001). The change (upright - supine) in SV was inversely correlated with the change in HR for all participants at rest (R(2) = 0.32), at 25 W (R(2) = 0.49), 50 W (R(2) = 0.60), and 75 W (R(2) = 0.32) (P < 0.01). These results suggest that greater elevation in HR in POTS patients during exercise, especially while upright, was secondary to reduced SV and associated with exercise intolerance.
Masuki et al. (Fri,) conducted a case-control in Postural tachycardia syndrome (POTS) (n=23). Graded cycle exercise (supine and upright) vs. Healthy controls was evaluated on Upright stroke volume during 75-W exercise (p=<0.01). Upright graded cycle exercise at 75-W revealed significantly lower stroke volume in POTS patients compared to healthy controls (70 vs 94 ml, P<0.01), driving excessive tachycardia.