Dual chamber pacer having automatic PVARP

Claim 1

A dual chamber cardiac pacemaker comprising: (a) means for sensing atrial depolarization events; (b) means for sensing ventricular depolarization events; (c) means for stimulating a ventricular chamber; (d) first timing means coupled to the means for sensing atrial depolarization events for establishing an AV interval between the occurrence of an atrial depolarization event and the time following such occurrence at which the ventricular chamber stimulating means stimulates the ventricular chamber; (e) second timing means coupled to the means for sensing ventricular depolarization events for establishing a PVARP time interval during which the first timing means is inhibited from initiating an AV interval; (f) means for detecting the occurrence of pacemaker mediated tachycardia episodes; and (g) means responsive to the detecting means and coupled to the second timing means for increasing the PVARP time interval for at least one beat by a time value in the range of from 350 milliseconds to 500 milliseconds that is sufficient to insure that retrograde P-waves are not tracked by the means for stimulating a ventricular chamber.

Claim 10

A method of operating a dual chamber cardiac pacemaker to avoid pacemaker-induced tachycardia, the pacemaker being of the type which senses atrial depolarization events and ventricular depolarization events, applies a stimulating pulse to ventricular tissue, and establishes an AV delay interval, a base PVARP time interval and a maximum tracking rate for tracking sensed atrial depolarization events, comprising the steps of: (a) sensing when stimulation of ventricular tissue is occurring at the maximum atrial tracking rate over a predetermined number of beats; (b) increasing the PVARP time interval for at least one beat from the base PVARP value to a value insuring that retrograde conducted P-waves will not fall outside of the increased PVARP time interval and thereafter (c) extending the base PVARP value by a predetermined PVARP increment value, each time the condition of step (a) is detected.

Claim 11

A method of operating a dual chamber cardiac pacemaker to avoid pacemaker-induced tachycardia, the pacemaker being of the type which senses atrial depolarization events and ventricular depolarization events, applies a stimulating pulse to ventricular tissue, and establishes an AV delay interval, a base PVARP time interval and a maximum tracking rate for tracking sensed atrial depolarization events, comprising the steps of: (a) sensing when stimulation of ventricular tissue is occurring at the maximum atrial tracking rate over a predetermined number of beats; (b) increasing the PVARP time interval for at least one beat from the base PVARP value to a value insuring that retrograde conducted P-waves will not fall outside of the increased PVARP time interval and thereafter (c) extending the base PVARP value by a predetermined PVARP increment value, each time the condition of step (a) is detected.