Table 1 Clinical characteristics of the subjects

Age (years)

63.5 ± 10.6

62.8 ± 10.7

65.2 ± 10.5

NS

Male/female gender, No.

70/8

50/6

20/2

NS

Etiology

 Coronary artery disease

43 (55.1)

29 (51.8)

14 (63.6)

NS

 Valvular disease

18 (23.1)

12 (21.4)

6 (27.3)

NS

 Idiopathic dilated cardiomyopathy

17 (21.8)

15 (26.8)

2 (9.1)

NS

Medication

 Diuretics

54 (69.2)

35 (62.5)

19 (86.4)

NS

 Nitrates

39 (50.0)

26 (46.4)

13 (59.1)

NS

 β-blockers

31 (39.7)

23 (41.1)

8 (36.4)

NS

 Angiotensin receptor blockers

29 (37.2)

23 (41.1)

6 (27.3)

NS

 Calcium-channel blockers

19 (24.4)

16 (28.6)

3 (13.6)

NS

 Angiotensin-converting enzyme inhibitors

17 (21.8)

12 (21.4)

5 (22.7)

NS

 Digitalis

17 (21.8)

11 (19.6)

6 (27.3)

NS

LVEF (%)

28.6 ± 7.7

28.8 ± 7.8

27.9 ± 7.8

NS

Heart rate at rest

80.1 ± 13.4

79.9 ± 13.3

80.6 ± 14.2

NS

Systolic blood pressure at rest

118.7 ± 17.1

120.7 ± 16.4

113.8 ± 18.5

NS

Heart rate at peak exercise

124.2 ± 22.3

125.7 ± 21.8

120.4 ± 23.6

NS

Systolic blood pressure at peak exercise

161.9 ± 30.7

168.1 ± 29.9

146.2 ± 27.5

0.004

Respiratory exchange ratio at rest

0.89 ± 0.05

0.89 ± 0.04

0.90 ± 0.08

NS

Respiratory exchange ratio at peak exercise

1.09 ± 0.10

1.09 ± 0.10

1.10 ± 0.10

NS

PETCO₂ at rest (mmHg)

32.5 ± 4.7

34.5 ± 3.3

27.4 ± 3.7

<0.0001

PETCO₂ at peak exercise (mmHg)

34.6 ± 6.4

37.6 ± 4.3

27.0 ± 4.3

<0.0001

Peak \( \dot{\rm{V}} \)O₂ (ml/min/kg)

15.2 ± 4.5

16.6 ± 4.3

11.7 ± 3.0

<0.0001

Δ\( \dot{\rm{V}} \)O₂/ΔWR (ml/min/W)

8.0 ± 2.6

8.6 ± 2.3

6.4 ± 2.5

0.0007

\( \dot{\rm{V}} \)E/\( \dot{\rm{V}} \)CO₂ slope

37.2 ± 12.5

32.6 ± 6.6

49.5 ± 15.9

<0.0001