Abstract
Background
Dobutamine has been proposed for the assessment of low-flow, low-gradient aortic stenosis (LFLGAS). However, in 1/3 of patients, no increase in stroke volume index can be achieved by Dobutamine, thus hampering its diagnostic value. This study evaluated the manoeuvre of cardiac preload augmentation by passive leg rise (PLR) alone or on top of Dobutamine to increase stroke volume index (SVI) in patients with LFLGAS, particularly in paradoxical LFLGAS.
Methods
We examined 50 patients with LFLGAS. Patients were assigned to the paradoxical LFLGAS (Paradox) group if left ventricular ejection fraction (LVEF) was ≥50% (n=29) and to the LFLGAS with low ejection fraction (LEF) group if LVEF was <50% (n=21). A modified Dobutamine stress echocardiography was performed in all patients with the following 4 steps: Rest, PLR alone, maximal Dobutamine infusion rate alone (Dmax) and Dobutamine plus PLR (Dmax + PLR). Three SVI measurement methods were used: first the left ventricular outflow tract velocity time integral (LVOT VTI) method, second the 2D Simpson's method, and third the 3D method. The corresponding aortic valve area (AVA) was obtained by the continuity equation. The increase of those values compared to measurements at rest was calculated and compared between the 3 stress steps.
Results
In the paradoxical LFLGAS group, delta SVI with Dmax assessed by both Simpson's (depicted in the figures) and 3D method was lowest compared to PLR and Dmax + PLR. PLR alone yielded an equally high delta SVI as Dmax + PLR in Simpson's and 3D, and was at least as high as Dmax across all methods. Dobutamine alone yielded the lowest delta transaortic aortic valve VTI. The highest delta aortic valve area resulted for Dmax + PLR. In the LEF group, the three stress steps yielded an equally high delta SVI with Simpson's method. Dmax never yielded a higher delta SVI than PLR alone. The yielded delta SVI was the highest for Dmax + PLR for both LVOT VTI and 3d method, although the difference was overall not as strong as in the Paradox group.
Conclusions
In patients with paradoxical LFLGAS, Dobutamine alone is inadequate for testing the potential of aortic valve opening augmentation. Instead, PLR alone or the addition of PLR plus Dobutamine should be used for that purpose. In low LVEF, adding PLR to Dobutamine also seems useful although its diagnostic added value is less evident than in the Paradox group.
FUNDunding Acknowledgement
Type of funding sources: Foundation. Main funding source(s): Gottfried und Julia Bangerter-Rhyner-Foundation Paradox group Low ejection fraction group
PARADOXICAL LOW FLOW LOW GRADIENT SEVERE AORTIC STENOSIS WITH PRESERVED LEFT VENTRICULAR EJECTION FRACTION: IMPACT OF SURGERY VERSUS MEDICAL THERAPY
