14th International Congress
THE "NEW FRONTIERS"
OF ARRHYTHMIAS 2000

Jan. 29 - Feb. 5, 2000
Marilleva, Trento, Italy

RT-51

Peak endocardial acceleration: a new physiologic sensor

A. Colella, L. Padeletti, M.C. Porciani, A. Costoli, A. Michelucci, P. Pieragnoli, P. Ritter*, H. Luttikhuis**, G. Gaggini***, G.F. Gensini.
Dept. of Internal Medicine and Cardiology, University of Florence, Florence, Italy, *InParys, Paris, France, **Sophia Hospital, Zwolle, The Netherlands, ***Sorin Biomedica Cardio, Saluggia, Italy

Background

For many years implantable devices for cardiac pacing applications have been developed with the main aim of treating AV block and sinus node dysfunction. With the introduction of rate responsive pacing in 1983, different kind of sensors have been developed, clinically validated and introduced into the clinical practice for driving rate adaptive pacemakers.

Researches are in progress, at different stages, to develop sensors able to supply information about important vital parameters like blood pressure, oxygen saturation and cardiac output. However, real use of these sensors for long-term applications showed quite severe limitations, particularly because of body tissue reactions adversely affecting their sensitivity and reliability.

In this context, SORIN has developed an implantable acceleration sensor (BEST – Biomechanical Endocardial Sorin Transducer) (Fig. 1), able to measure the amplitude of mechanical vibrations generated by the myocardium during the isovolumetric contraction phase¹. During this phase, the myocardial fibres tensioning generates vibrations which are transmitted to whole myocardium and whose audible component is appreciable as the first heart sound. The sensor housed inside a rigid and hermetic capsule is inserted in the tip of a standard unipolar pacing lead. The rigidity makes the sensor totally insensitive to blood or muscle pressure. The signal component (Fig. 2), directly related to myocardial contractility, is represented by the peak to peak value of endocardial acceleration signal and it is called PEA (peak endocardial acceleration).

Fig. 1: Contractility sensor (BEST) structure.

Fig. 2: Peak endocardial acceleration.

In vivo preclinical tests on animals and humans were carried out to evaluate the PEA signal for rate responsive (RR) pacing. Four years of acute and chronic evaluations on animals and humans demonstrated that PEA signal is:

–independent from pacing rate,

–correlated to spontaneous rate, to LV and RV dP/dt max during adrenergic stimulation,

–detected in the right ventricle but mainly reflects contractility changes in the left ventricle.

A DDDR pacemaker, double sensor (gravimetric and PEA sensor) called Living 1, was the first product using PEA signal as RR physiological parameter. The pacing rate is calculated cycle-by-cycle on the basis of the difference between the current PEA value and the reference one. The reference value is dynamically updated by the algorithm itself. This makes the algorithm independent by any variation in PEA basal value due to changes in the patient situation, for instance related to drugs affecting heart contractility.

From December 1995 to January 1997, 105 patients were enrolled in a multicentric European clinical evaluation and followed for 1 year². The 1 year follow-up data demonstrated that PEA is a long term stable parameter and it can be used for physiological driving of RR pacemakers. The long-term experience also showed the absence of any adverse effect and the reliability of the sensor itself. As of today, an overall implant experience of about 850 units with a maximum follow-up of 3.5 years has been reached. The results of all these studies suggest the possibility of using PEA as a haemodynamic monitor of cardiac function, able to overcome the limitations of other sensors.

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