BACKGROUND: Latent left ventricular (LV) dysfunction in patients with valvular or myocardial disease may be identified by loss of contractile reserve (CR) at exercise echocardiography. Contraction in the LV longitudinal axis may be more sensitive than radial contraction to minor disturbances of LV function. We sought to determine whether tissue Doppler measurement of longitudinal function could be used to identify CR. METHODS: Exercise echocardiography was performed in 86 patients (20 women, age 53 +/- 18 years), 72 with asymptomatic or minimally symptomatic mitral regurgitation, and 14 normal controls. Pulsed-wave tissue Doppler imaging (DTI) was used to measure maximum annular systolic velocity at rest and stress. Inducible ischemia was excluded by analysis of wall motion by an experienced observer. CR was defined by >or=5% improvement of stress compared with rest ejection fraction (EF). Exercise capacity was assessed from expired gas analysis. RESULTS: CR was present in 34 patients with mitral regurgitation (47%); peak EF in patients with and without CR was 74% +/- 11% versus 54% +/- 15% (P <.0001). CR could not be predicted by resting EF, volumes or sphericity, and DTI measurement of base-apex function was the only resting echocardiographic parameter to distinguish between patients with and without CR (10 +/- 2 vs 8 +/- 2 cm/s, P <.03). This parameter showed greater differences after stress (14 +/- 4 vs 11 +/- 3 cm/s, P <.001). Patients with CR showed lower peak DTI than controls, as well as lower exercise capacity and EF response to exercise. In a multiple linear regression model, rest DTI (P =.03) was an independent correlate of contractile reserve. The other correlates were age (P <.0001), resting (P <.0001) and peak end-systolic volume (P =.01), and resting (P <.0001) and peak end-diastolic volume (P <.0001); the model r(2) was 0.93 (P <.001). CONCLUSION: In the absence of regional LV dysfunction, measurement of longitudinal axis function by DTI may be a marker of CR.