Aortic Stenosis: Evaluation of Severity Before and After Transcatheter Aortic Valve Implantation by Means of Ballistocardiography and Seismocardiography.

Calcific aortic stenosis (AS) (formerly "senile" or "degenerative") is a frequent disease of heart valves and is characterized by a thickness and calcification of leaflets with a significant increase of the pressure gradient, defined as an aortic jet velocity of > 2 m/s. Whenever the aortic jet velocity is > 4 m/s, in association with an aortic valve area of < 1 cm2, the disease is classified as severe and cardiac outflow obstruction develops. AS affects 1-2% of population aged of > 65 years and 12% of those aged > 75 years. Among those aged > 75 years, it is estimated that 3.5% has severe AS. With the aging of population, the prevalence of AS is expected to increase in the forthcoming years. Transcatheter Aortic Valve Implantation (TAVI) has been introduced in 2004 and consists in percutaneous replacement of the aortic valve. It is indicated in those patients with severe AS who cannot undergo surgical replacement because of high surgical risk. TAVI seems to be a good alternative to surgical intervention also for patients deemed at intermediate risk, especially if they are frail or aged. Ballistocardiography (BCG) consists of the measurement of the body's accelerations as a consequence of the recoil forces generated by the blood mass ejection at each cardiac contraction and recorded on the body's surface close to the subject's center of mass. Seismocardiography (SCG) records the heart-induced accelerations generated at each cardiac contraction and transmitted to the local chest surface. Thanks to specific algorithms applied to the SCG and BCG waves, it is possible to compute the kinetic energy (KE) and Power (P) of a single cardiac contractile cycle.

The aims of our study are to demonstrate that: LVOT Vmax and LVOT VTI changes obtained with echocardiography can be estimated reliably throught BCG and SCG signals, before and after TAVI procedure; Pmax and KE computed from the BCG and SCG signals could predict the severity of the AS before the TAVI procedure.

KE and P computed from non invasively recorded BCG and SCG waves may prove useful in the evaluation of AS severity and its evolution before and after TAVI procedure, respectively.