Apparatus for non-invasive diagnosis of vasovagal syncope in a patient
An apparatus for non-invasive diagnosis of states of vasovagal syncope in a patient placed on a tilt table and subjected to a tilt-test, the apparatus comprising: circuits for sensing the patient's endocardiac acceleration; circuits for sensing the patient's heart rate; and analyzer circuits receiving as inputs said endocardiac acceleration and said heart rate, and outputting information about the sympthetico-vagal activity of the patient. The circuits for sensing endocardiac acceleration comprise an external accelerator sensor suitable for being held in contact with the patient's rib cage. The analyzer circuits comprise classifier circuits suitable, in the event of a syncope occurring, for determining one type of syncope amongst a plurality of syncope types as a function of the endocardiac acceleration and heart rate values sensed during a plurality of heart cycles preceding the occurrence of the syncope.
1. An apparatus for non-invasive diagnosis of states of vasovagal syncope in a patient placed on a tilt table and subjected to a tilt-test, the apparatus comprising:
means for sensing the patient's endocardiac acceleration;
means for sensing the patient's heart rate; and
analyzer means receiving as inputs said endocardiac acceleration and said heart rate, and outputting information about the sympathetico-vagal activity of the patient;
wherein:
the means for sensing endocardiac acceleration comprise an external accelerator sensor suitable for being held in contact with the patient's rib cage; and
the analyzer means comprise classifier means suitable, in the event of a syncope occurring, for determining one type of syncope amongst a plurality of syncope types as a function of the endocardiac acceleration and heart rate values sensed during a plurality of heart cycles preceding the occurrence of the syncope.
2. The apparatus of claim 1 , wherein:
the analyzer means are means suitable for determining at least one value as a function of one of a plurality of endocardiac acceleration peaks during a given cycle, these peaks comprising a first peak during the constant volume ventricular contraction stage and a second peak during the constant volume ventricular relaxation stage; and
the classifier means are means suitable for determining the type of syncope as a function of the values of the endocardiac acceleration peaks and of the heart rate as sensed during a plurality of heart cycles preceding the occurrence of the syncope.
3. The apparatus of claim 2 , wherein the classifier means are means suitable for determining the type of syncope as a function of an average of the values of the endocardiac acceleration peaks sensed during a plurality of heart cycles preceding the occurrence of the syncope.
4. The apparatus of claim 2 , wherein the classifier means are means suitable for determining the type of syncope as a function of the variation in the values of the endocardiac acceleration peaks sensed during a plurality of heart cycles preceding the occurrence of the syncope.
5. The apparatus of claim 2 , wherein the analyzer means comprise means for determining:
a long-term average and a short-term average of the values of the first endocardiac acceleration peaks sensed during the constant volume ventricular contraction stage during a plurality of successive cycles; and/or
a long-term average and a short-term average of the values of the second endocardiac acceleration peaks sensed during the constant volume ventricular relaxation stage during a plurality of successive cycles; and
a long-term average and a short-term average of the heart rate values;
and in which the classifier means are means suitable for determining the type of syncope as a function of differences between the long-term and short-term averages of the values of the endocardiac acceleration peak(s) sensed during a plurality of heart cycles preceding the occurrence of the syncope.
6. The apparatus of claim 5 , wherein the classifier means are means suitable for determining a type of syncope when:
the short-term average of the values of the first acceleration peaks is less than the long-term average of the values of the first acceleration peaks weighted by a first proportionality factor; and
the short-term average of the heart rate values is greater than the long-term average of the heart rate values weighted by a second proportionality factor.
7. The apparatus of claim 6 , wherein the classifier means are means suitable for determining a type of syncope when:
the short-term average of the values of the second acceleration peaks is less than the long-term average of the values of the first acceleration peaks weighted by a third proportionality factor; and
the short-term average of the heart rate values is greater than the long-term average of the heart rate values weighted by a fourth proportionality factor.
8. The apparatus of claim 7 , wherein the classifier means are means suitable for determining a type of syncope when:
the short-term average of the values of the second acceleration peaks is less than the long-term average of the values of the first acceleration peaks weighted by a fifth proportionality factor, less than said third proportionality factor; and
the short-term average of the heart rate values is greater than the long-term average of the heart rate values weighted by a sixth proportionality factor, less than said fourth proportionality factor.
9. The apparatus of claim 5 , wherein the classifier means are means suitable for determining a type of syncope when:
the short-term average of the values of the second acceleration peaks is less than the long-term average of the values of the first acceleration peaks weighted by a third proportionality factor; and
the short-term average of the heart rate values is greater than the long-term average of the heart rate values weighted by a fourth proportionality factor.
10. The apparatus of claim 5 , wherein the classifier means are means suitable for
determining a type of syncope when:
the short-term average of the values of the second acceleration peaks is less than the long-term average of the values of the first acceleration peaks weighted by a fifth proportionality factor, less than said third proportionality factor; and
the short-term average of the heart rate values is greater than the long-term average of the heart rate values weighted by a sixth proportionality factor, less than said fourth proportionality factor.
11. An apparatus for non-invasive diagnosis of states of vasovagal syncope in a patient placed on a tilt table and subjected to a tilt-test, the apparatus comprising:
an external accelerator sensor having an output corresponding to endocardiac acceleration;
a plurality of electrodes operative to detect a cardiac activity; and
a microcomputer responsive to said detected cardiac activity and endocardiac acceleration, wherein said microcomputer comprises an algorithm for classifying, in the event of a syncope occurring, one type of syncope amongst a plurality of syncope types as a function of said detected endocardiac acceleration and heart rate values sensed in said detected cardiac activity during a plurality of heart cycles preceding the occurrence of the syncope.