Background The predominant complaint of patients with heart failure and normal ejection fraction (HFNEF) is exertional dyspnoea and reduced exercise capacity. There is ongoing controversy regarding the mechanism causing such limitation. We hypothesise that HFNEF patients have reduced left ventricular longitudinal functional reserve, which contributes to their symptoms and exercise limitation.
Methods Patients with a clinical diagnosis of HFNEF and healthy controls were recruited. All subjects underwent cardiopulmonary exercise test to determine their peak maximum oxygen consumption (Vo2max) and predicted oxygen consumption. Rest and submaximal supine exercise echocardiography were performed and images were digitally stored for off-line analysis (Echopac). Global longitudinal strain was analysed using speckle tracking and mean systolic (Sm) and diastolic (Em) mitral annular velocities were derived from colour tissue Doppler analysis of the apical four and two chamber images. All images were analysed by two independent observers and results were averaged. The left ventricular systolic longitudinal functional reserve index was calculated using the equation: (Sm on exercise − Sm at rest) ⋅ (1-1/Sm at rest).
Results 45 patients (aged 71 ± 8 years, 31 women, left ventricular ejection fraction (LVEF) 60 ± 6%) with dyspnoea on exercise and 27 age-matched healthy controls (aged 70 ± 7 years, 19 women, LVEF 62 ± 8%) with adequate images and comparable heart rate responses on exercise were analysed. Sm, Em and global longitudinal strain were significantly lower in patients compared with controls and these differences were even more apparent on exercise (Sm 6.0 ± 1.0 cm/s, p<0.001; Em 6.5 ± 1.4 cm/s, p<0.001; global longitudinal strain −20.1 ± 4.1%, p = 0.001). The systolic longitudinal reserve index was significantly lower in patients (0.6 ± 0.5 vs 1.5 ± 0.7, p<0.001) and correlated with the percentage predicted oxygen consumption and peak Vo2max (r = 0.517, p = 0.016 and r = 0.447, p = 0.042). Sm and Em on exercise also correlated with peak Vo2max (r = 0.597, p = 0.003 and r = 0.417, p = 0.034).
Conclusions Longitudinal function is impaired in patients with HFNEF. This abnormality is more apparent on exercise and is associated with reduced left ventricular longitudinal functional reserve and limited exercise capacity.
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