Left Ventricular Diastolic Functional Reserve during Exercise in Patients with Impaired Myocardial Relaxation at Rest

¹ Yonsei University College of Medicine, Korea, Republic of
² Mayo Clinic, United States

^* To whom correspondence should be addressed. E-mail: jwha{at}yuhs.ac.

Accepted 24 June 2008

	Abstract

Background: A reduced early (E) to late (A) diastolic filling ratio or prolonged deceleration time (DT) of E velocity reflects slowing of left ventricular (LV) relaxation. These findings are believed to indicate significant diastolic dysfunction. However, in patients with a similar grade of diastolic dysfunction at rest, a spectrum of alterations in diastolic function can exist during exercise. This study was sought to evaluate (1) whether exercise could unmask further diastolic abnormalities not evident under rest conditions and (2) whether diastolic functional reserve during exercise is associated with exercise capacity.

Methods: One hundred forty-one subjects (77 male, mean age 57±10) with abnormal LV relaxation, defined as the presence of mitral E/A<0.75 and/or DT>240 ms, underwent 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 graded supine bicycle exercise (25 W, 3 minutes increments). LV diastolic function reserve index (DFRI) was calculated as E'xE'base; where E' is the change of E' from baseline to exercise and E'base is early diastolic mitral annular velocity at rest.

Results: The median DFRI at 50W of exercise was 13.5. Patients were classified into two groups: group 1 (n=64), DFRI<13.5; and group 2 (n=77), DRFI>13.5. The ratio of E/E?to stroke volume was used as an index of ventricular elastance (Ed). There were no significant differences in mitral inflow (E, A, E/A, DT) and annular velocities at rest between the two groups. Ed was not significantly different at rest between the groups (0.19±0.07 vs 0.18±0.06 cm/s, p=0.29). However, Ed was significantly higher during exercise in group 1 as compared to group 2 (25 Watts, 0.21±0.09 vs 0.14±0.04, p<0.0001; 50 Watts, 0.22±0.10 vs 0.15±0.04, p<0.0001). The subjects in group 1 had a shorter exercise duration (8.2±2.7 vs 9.4±3.7 minutes, 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 observed 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.