EUROECHO and other imaging modalities 2012 location:Athens, Greece date:05-08 December 2012
Purpose: LV contractility can be estimated only invasively by using the fact that systolic LV response to changing preload depends on its inotropic state. We assumed that if the slope of relation between regional differences in LV function (systolic strain, SS) and preload (stretch during atrial contraction, preS) depends on it as well, it could be used as a LV contractility index. We tested this hypothesis in vivo by changing LV inotropy and preload.
Methods: In 8 healthy subjects (58±11y) tissue Doppler (TDI) of 3 apical LV planes was obtained at rest (BL) and at increased LV inotropy induced by low dose dobutamine (10mkg/kg/min) (LD). In 11 subjects (53±3y) global preload was increased by leg-lift (LL). TDI of inferoseptal (IS) wall was recorded at BL and within 30s of LL. Regional strain curves were extracted with custom software by setting reference point at the onset of P wave on ECG. PreS was measured as peak positive strain after P wave, SS as subsequent systolic shortening. Linear regression between preS and SS was performed per subject at each stage. Mean relations were determined as an average slope and intercept at each stage.
Results: PreS and SS correlated in all subjects (r range 0.74:0.95). SS increased (p<0.05) with LD (-20.4±4. 5% vs -24.2±5.6%) and LL (-19.7±3.8% vs -24.1±3.7%), and PreS only with LL (LL: 6.0 ±1.7% vs 8.6±2.2%, p<0.05; LD: 6.8±2.3% vs 7.3±2.3%, ns). The slope of preS - SS relation steepened with LD (-1.49±0.35 vs -2.25±0.36, p<0.05), but not with LL (-1.39±0.57 vs -1.51±0.39, ns).
Conclusion: The slope of the stretch-strain relationship steepens with increasing inotropy, and not with preload induced changes of LV function. Thus it can be regarded as a non-invasive index of LV contractility. The effect of afterload on it remains to be tested.