Background Twisting of the left ventricle (LV) is important for efficient systolic and diastolic function. In normal individuals both twisting and untwisting have been shown to increase with exercise. We aimed to assess whether patients with chronic primary mitral regurgitation (MR) are able to produce the same response.
Methods 28 patients aged 60 ± 14 years with chronic moderate to severe (grade 3–4) primary MR were recruited along with 28 age-matched controls (aged 56 ± 11 years). Subjects underwent echocardiography at rest and during submaximal exercise on a supine bicycle ergometer. Left ventricular rotation and rotational velocity were assessed at rest and during exercise using two-dimensional speckle-tracking echocardiography in short axis basal and apical views. Basal rotation was subtracted from apical rotation to obtain overall LV twist. Velocities of twisting and untwisting were obtained in a similar manner.
Results Resting and peak exercise heart rates (HR) were similar in the two groups (resting HR 73 ± 12 bpm MR vs 69 ± 12 controls, p = ns; peak HR 110 ± 7 vs 109 ± 5, p = ns). Resting ejection fraction (EF) was also comparable in the two groups (64.2 vs 65.68, p = ns). At rest, the amplitude of peak systolic twist (PST) was not significantly different between the two groups, but time to PST (normalised to duration of systole) was delayed in MR compared with controls (p<0.001). Peak untwisting velocity (PUV) in diastole was of greater amplitude in MR than controls (p = 0.04), but occurred later in the MR group (time to PUV, p<0.001). On exercise, the amplitude of PST increased in normals but not patients with MR. PST was reached earlier on exercise than at rest in MR patients but was still delayed relative to controls (p = 0.002). In the MR group, PUV also occurred earlier on exercise than at rest but remained delayed relative to controls (p = 0.007). PUV increased in amplitude in both (see table).
Conclusions A failure in the normal enhancement of systolic twist on exercise is seen in patients with chronic MR even with normal resting left ventricular ejection fraction. In patients with MR, the abnormally delayed resting PST and time to PUV occur earlier on exercise, which may tend to prevent an excessive rise in left atrial pressures and minimise exertional dyspnoea. However, these parameters are still delayed compared with controls.