Background Left ventricular (LV) untwist plays a vital role in the generation of the intraventricular pressure gradient, which is necessary for the LV suction in early diastole. The ability of the left ventricle to untwist in diastole is dependent on systolic twist. We hypothesise that patients with heart failure and normal ejection fraction (HFNEF) have reduced LV untwist to facilitate rapid early diastolic filling, particularly during exercise thus causing symptoms of breathlessness on exertion.
Methods 34 patients with clinical diagnosis of HFNEF and confirmed cardiac limitation on metabolic exercise testing (72 ± 7 years, 23 women, left ventricular ejection fraction (LVEF) 60 ± 7%, maximal oxygen consumption (VO2max) 17.9 ± 3.0 ml/min/kg) and 23 age-matched healthy controls (70 ± 8 years, 15 women, LVEF 63 ± 8%, VO2max 30.9 ± 4.6 ml/min/kg) were recruited. Rest and submaximal supine exercise echocardiography were performed to comparable heart rate and blood pressure. Two-dimensional apical short axis images were used for the analysis of apical rotation and untwist by speckle tracking using custom software (Echopac). The mitral flow propagation velocity (Vp) was derived from colour M-mode Doppler obtained through the mitral valve and measured by the slope along the aliasing isovelocity line.
Results LV apical systolic rotation and early diastolic untwist were significantly less in patients compared with controls both at rest (apical rotation 10.7 ± 4.1° vs 13.9 ± 3.2° p = 0.002; early diastolic untwist 24.3 ± 9.4% vs 30.9 ± 9.7%, p = 0.013) and on exercise (apical rotation 13.5 ± 4.8° vs 17.6 ± 4.0°, p = 0.006; early diastolic untwist 22.1 ± 8.9% vs 29.5 ± 7.8%, p = 0.008). Vp at rest was comparable between the two groups (40.2 ± 10.8 m/s vs 39.8 ± 7.3 m/s, p = 0.875). On exercise, the increase in Vp was significantly less in patients, hence Vp was significantly lower than controls (52.6 ± 12.0 m/s vs 62.4 ± 13.8 m/s, p = 0.012). LV early untwist correlated significantly with the increase in Vp (r = 0.43, p = 0.005) and VO2max (r = 0.526, p = 0.007). Exercise Vp also correlates with VO2max (r = 0.347, p = 0.03; see fig).
Conclusion LV rotation and untwist mechanics are impaired in HFNEF. This is associated with reduced LV suction in early diastole and reduced exercise tolerance. The efficiency of LV rotation and untwist is crucial to aid rapid early diastolic filling particularly on exercise when diastole shortens and disturbances of this may play an important role in generating symptoms in HFNEF.
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