Background Heart failure is a common cause of morbidity and mortality in patients with diabetes. The early manifestations of diabetic cardiomyopathy are, however, not well established. Left ventricular (LV) twist followed by untwisting during diastole is an important component that affects LV filling. We used speckle tracking echocardiography to study the early changes in the LV twist.
Methods 33 asymptomatic subjects with type 1 diabetes mellitus (T1DM; mean ± 1 SD age 32.9 ± 8.4 years, diabetes duration 13.9 years) and 32 age-matched healthy controls (HC) (age 30.8 ± 8.0 years) were recruited into the study. All subjects underwent echocardiography (Vivid 7) and metabolic exercise testing to exclude heart failure and ischaemic heart disease. LV rotation measurements were made using a commercially available speckle tracking system (ECHOPAC workstation) from a grey-scale two-dimensional image, which tracks the displacement of speckles of myocardium in each spot from frame to frame. Counter-clockwise rotation was marked as a positive value and clockwise rotation as a negative value when viewed from the apex. LV twist curves were obtained by subtracting basal rotation from apical rotation (figs 1 and 2) using graphical software Dplot (version 188.8.131.52, HydeSoft Computing, LLC, Vicksburg, USA). Twist rates were obtained from the first derivative of the twist curve.
Results The baseline characteristics are summarised in table 1. Left ventricular ejection fraction was 60.7 ± .5% in the T1D subjects and maximal oxygen consumption was 38.5 ml/kg per minute ± 9.9 (98.6% of predicted). In the HC, the corresponding values were 61.4 ± 5% (p = 0.29 vs T1DM) and 44.1 ml/kg per minute ± 7.2 (112% of predicted; p<0.01 vs T1DM), respectively. The results are summarised in table 2. There was a significant increase in peak apical rotation (11.3 ± 4.4 vs 8.5 ± 4, p<0.01) and LV twist (15.3 ± 4.4 vs 11.3 ± 6, p<0.01) in T1DM compared with HC. The peak twist rate was also significantly higher in T1DM (103.9 ± 37.8 vs 85.9 ± 37, p<0.05). The early peak untwisting velocity although greater in T1DM (−98.2 ± 37.1 vs −90.3 ± 41.5, p = 0.21), did not reach statistical significance. However, the late untwisting rate, which indicates the atrial phase of filling, was significantly greater in T1DM (−51 ± 22.9 vs −38 ± 28.9, p<0.05).
Conclusion We demonstrate for the first time using speckle tracking that despite normal ejection fraction, the LV twist, twist rate and untwisting rate is increased in patients with uncomplicated T1DM. This may represent compensation of the myocardium to maintain the ejection fraction during the early stages of diabetic cardiomyopathy.