Low flow-low gradient is one of the most challenging conditions among valvular heart disease because parameters of stenosis quantification and left ventricular dysfunction at rest do not reflect disease severity. Therefore dobutamine stress echocardiography is commonly used to grade stenosis severity and the extent of myocardial impairment. In the current study we used 2-dimensional strain parameters measured by speckle tracking to document the extent of myocardial impairment at rest and during dobutamine stress. Further aims of the present work were to investigate the relationship to hemodynamics and the prognostic value of 2-dimensional strain parameters. 47 (fortyseven) patients with low flow-low gradient aortic stenosis underwent dobutamine stress echocardiography and offline speckle tracking for quantification of global peak systolic longitudinal strain (PLS) and peak systolic longitudinal strain rate (PLSR). PLS at rest and peak stress was -7.562.34% and -7.412.89% (P=NS). PLSR at rest and peak stress was -0.380.12 s-1 and -0.530.18 s-1 (P<0.001). There was an inverse correlation of PLS and PLSR to left ventricular ejection fraction at rest (rs=-0.52; P<0.0001 and-0.38; P=0.008) as well as at peak stress (rs=-0.39; P=0.007 and-0.45; P=0.002). Median (Q1-Q3) N-terminal pro-B-type natriuretic peptide (NT-proBNP) level was 3966 (2396 - 9010) pg/mL. 2-year survival of the study group was 60%.
Predictors of survival in univariate analysis were peak stress left ventricular ejection fraction (P=0.0026), peak stress PLS (P=0.0002), peak stress PLSR (P<0.0001), and NT-proBNP (P<0.0001). To test the incremental value of PLSR to clinical risk, NT-proBNP and peak stress left ventricular ejection fraction three hierarchically nested multivariable Cox regression models were built. Model 1: The Society of Thoracic Surgeons score as a marker of clinical risk (AUROC=0.59). Model 2: model 1 plus NT-proBNP and peak stress left ventricular ejection fraction (AUROC =0.83; incremental P<0.0001); model 3: model 2 plus peak stress PLSR (AUROC =0.89; incremental P=0.035).
These data provide evidence that in patients with low flow-low gradient aortic stenosis peak stress PLS and peak stress PLSR are strong predictors of outcome. Furthermore peak stress PLSR may add incremental prognostic value to clinical risk, NT-proBNP and peak stress left ventricular ejection fraction.