Physiologic frequency adaptation of cardiac pacemakers using systolic time intervals

: Of the parameters in consideration for control of physiological rate responsive pacing special interest is directed to stroke volume. In search of indirect parameters which are correlated to stroke volume it is demonstrated on principle that systolic time intervals could be used. From the relation ejection time versus pre-ejection time (LVET/PEP) which is known for its correlation to stroke volume a simple algorithm is derived which is based on the realization that PEP is related to the reciprocal of cardiac output. First investigations with patients demonstrated the possibility of the computation of heart rate from PEP only, with good physiological significance.