Ventricular tachycardia detection algorithm using only cardiac event intervals

An implantable medical device system comprising:

• an implantable pacemaker comprising:
• a housing sized to fit within a heart;
• at least two electrodes disposed on the housing;
• a pacemaker sensing module enclosed within the housing and electrically coupled to the at least two electrodes, the pacemaker sensing module configured to obtain R-waves from a first cardiac electrical signal received from the at least two electrodes coupled to the sensing module;
• a pulse generator enclosed within the housing and electrically coupled to the at least two electrodes, the pulse generator configured to generate cardiac pacing pulses for delivery to the heart via the at least two electrodes;
• and
• a pacemaker control module enclosed within the housing and electrically coupled to the sensing module and the pulse generator, the pacemaker control module configured to:
• determine RR intervals between consecutive ones of the sensed R-waves;
• apply RR interval-based ventricular tachycardia detection criteria solely to the determined RR intervals;
• detect a monomorphic ventricular tachycardia (VT) when the detection criteria are met;
• and
• control the pulse generator to deliver anti-tachycardia pacing in response to detecting the monomorphic VT,
• wherein applying the detection criteria solely to the determined RR intervals comprises applying at least a non-sinus rhythm criterion, a supraventricular tachycardia rejection criterion that is different than the non-sinus rhythm criterion, and a number of tachycardia intervals to detect criterion to the RR intervals
• an implantable cardioverter defibrillator (ICD) system comprising:
• at least one extravascular defibrillation lead having a plurality of extravascular electrodes;
• an ICD coupled to the at least one extravascular defibrillation lead, the ICD comprising:
• an ICD sensing module electrically coupled to at least a portion of the plurality of extravascular electrodes to receive a second cardiac electrical signal;
• a defibrillation therapy delivery module comprising at least one high voltage capacitor, the defibrillation therapy delivery module being configured to deliver a shock therapy to the heart via at least one of the plurality of extravascular electrodes of the extravascular defibrillation lead;
• an ICD control module electrically coupled to the ICD sensing module and the defibrillation therapy delivery module, wherein the ICD control module is configured to:
• analyze the second cardiac electrical signal received by the ICD sensing module;
• detect the monomorphic VT detected by the pacemaker control module in response to the analyzing of the second cardiac electrical signal;
• and
• control the therapy delivery module to charge the at least one high voltage capacitor in response to detecting the monomorphic VT,
• wherein the number of tachycardia intervals to detect criterion comprises requiring a threshold number of the determined RR intervals being less than a tachycardia detection interval,
• wherein a maximum time interval including the threshold number of the determined RR intervals that are less than the tachycardia detection interval is shorter than an expected time interval required for detecting the monomorphic VT by the ICD and completing charging of the at least one high voltage capacitor by the ICD.