Left ventricular diastolic functional reserve during exercise in patients with impaired myocardial relaxation at rest

Abstract

BACKGROUND: Patients with similar grade diastolic dysfunction at rest may have a spectrum of alterations in diastolic function during exercise.

OBJECTIVE: To evaluate (a) whether exercise could unmask further diastolic abnormalities not evident during rest; (b) whether diastolic functional reserve during exercise is associated with exercise capacity.

METHODS: 141 subjects (77 male, mean (SD) age 62 (9)) with abnormal left ventricular (LV) relaxation (mitral E/A <0.75) and/or deceleration time >240 ms, underwent graded supine bicycle exercise with simultaneous respiratory gas analysis and two-dimensional and Doppler echocardiographic study. Mitral inflow and annular velocities were measured at rest and during exercise. The LV diastolic function reserve index (DFRI) was calculated.

RESULTS: Patients were classified into two groups: group 1 (n = 64), DFRI <13.5; group 2 (n = 77), DFRI >or=13.5. The ratio of E/E' to stroke volume was used as an index of ventricular elastance (Ed). No significant differences between the groups in mitral inflow and annular velocities at rest were found. Mean (SD) Ed was not significantly different at rest between the groups (0.19 (0.07) vs 0.18 (0.06), p = 0.29). Ed was significantly higher during exercise in group 1 than in group 2 (25 W, 0.21 (0.09) vs 0.14 (0.04), p<0.001; 50 W, 0.22 (0.10) vs 0.15 (0.04), p<0.001). Group 1 subjects had a shorter exercise duration (8.2 (2.7) vs 9.4 (3.7) min, p = 0.04) and lower peak oxygen consumption (17.5 (4.5) vs 20.2 (5.4) ml/kg/min, p = 0.005).

CONCLUSIONS: Despite similar mitral flow and annular velocities at rest, different responses to exercise were seen in patients with abnormal LV relaxation at rest. Lower LV diastolic functional reserve was associated with higher ventricular elastance during exercise, and reduced exercise capacity.