Pacemaker mediated tachycardia response for VDD and VDDR modalities

In a patient having an implanted dual chamber pacemaker, a method for detecting and suppressing a pacemaker mediated tachycardia (PMT), the pacemaker including:

• sensing means for sensing P-waves;
• pulse generation means for generating a V-pulse;
• and timing means for defining a PV delay that begins upon sensing a P-wave, after which a V-pulse is generated, whereby sensed P-waves are tracked by generating a V-pulse one PV delay thereafter, and a post ventricular atrial refractory period (PVARP) that begins following a V-pulse, and during which P-waves are not tracked, said method comprising the steps of:
• determining if a PMT is present;
• and
• suppressing the PMT by:
• extending the PVARP of the pacemaker from an initial value to an extended value, whereby an extended PVARP is generated;
• sensing the occurrence of a P-wave;
• maintaining the PVARP at the extended PVARP in the absence of a P-wave being sensed following the extended PVARP;
• restoring the PVARP to its initial value if:
• (1) a P-wave is sensed following the extended PVARP within at least one of the plurality of subsequent cardiac cycles, or (2) a prescribed number of subsequent cardiac cycles elapse without a P-wave being sensed during the extended PVARP, whichever occurs first.

In a pacemaker having sensing and timing circuits, a method for detecting and suppressing a pacemaker mediated tachycardia (PMT), said method comprising the steps of:

• detecting a PMT using the sensing and timing circuits of the pacemaker;
• and
• suppressing the PMT once detected by:
• increasing a post ventricular atrial refractory period (PVARP) of the pacemaker from an initial value to an extended PVARP;
• sensing a P-wave during the extended PVARP within at least one of a plurality of subsequent cardiac cycles;
• resetting a no-sensed-P-event (NSPE) count in response to the sensing of a P-wave during the extended PVARP within the at least one of the plurality of subsequent cardiac cycles;
• incrementing the NSPE count in response to an extended PVARP interval, within the plurality of subsequent cardiac cycles, during which a P-wave is not sensed;
• determining whether the NSPE count reaches a predefined terminal count;
• restoring the PVARP to its initial value in response to determining that the NSPE count has reached the terminal count.

An implantable dual-chamber pacemaker for detecting and suppressing a pacemaker mediated tachycardia (PMT) comprising:

• detecting means for detecting a PMT;
• and
• suppressing means for suppressing the PMT once detected, the suppressing means including:
• PVARP extension means responsive to the PMT detecting means for extending a post ventricular atrial refractory period (PVARP) of the pacemaker from an initial value to an extended value, thereby creating an extended PVARP;
• first sensing means for sensing a P-wave following the extended PVARP within at least one of a plurality of subsequent cardiac cycles;
• and
• maintaining means for maintaining the PVARP at the extended PVARP in the absence of a P-wave being sensed following the extended PVARP;
• restoring means for restoring the PVARP to its initial value in response to a P-wave being sensed by the first sensing means;
• whereby a PMT is detected, suppressed and the PVARP is restored to its initial value.

An implantable pacemaker for detecting and suppressing a pacemaker mediated tachycardia (PMT), said pacemaker comprising:

• detecting means for detecting a PMT;
• and
• PMT suppressing means responsive to the detecting means for suppressing the PMT, the PMT suppressing means including:
• extension means for increasing a PVARP of the pacemaker from an initial value to an extended value, thereby creating an extended PVARP;
• sensing means for sensing a P-wave during the extended PVARP within at least one of a plurality of subsequent cardiac cycles;
• an incrementable counter coupled to the sensing means, the counter being incremented in response to an extended PVARP interval, within the plurality of subsequent cardiac cycles, during which a P-wave is not sensed by the sensing means;
• reset means coupled to the counter for resetting the counter in response to the sensing of a P-wave during the extended PVARP within the at least one of the plurality of subsequent cardiac cycles;
• processing means coupled to the counter and reset means for determining whether the counter reaches a terminal count;
• restoring means for restoring the PVARP to its initial value in response to the processor means determining that the counter has reached a terminal count.