Herzschrittmacher mit verbesserter Abtastung und Unterdrückung der R-Zacken aus dem Fernfeld

A dual chamber pacemaker (50) is provided with a dynamic PVARP (Fig. 3b) which tracks the occurrence of high rate atrial senses within the normal PVARP range. The dynamic PVARP is a short window (71) of about 50 ms which is moved toward the time of occurrence of any sense signal within the window range of about 50-200 ms following the ventricular event. Senses which occur within the dynamic window are rejected, or blanked (120, 123), while senses occurring within the window range but outside of the window are recognized and evaluated (120, 121). The dynamic window technique accordingly enables the pacemaker to recognize tachycardia senses which would otherwise be blanked by a fixed length PVARP, while providing efficient suppression of FFRS events. The pacemaker also provides a technique (Fig. 9, Fig. 10) for determining whether rejected senses are tachy atrial senses or FFRS, by modulating the AV interval and thus shifting the dynamic window which is coupled to the ventricular pulse. As a result of this modulation, FFRS events move with the dynamic window, but tachy senses are covered, or revealed, enabling the pacemaker to make an appropriate response (136).