Dual chamber arrhythmia detection in the implantable cardioverter defibrillator

Dual Chamber Arrhythmia Detection by ICD, Introduction: Dual chamber implan table cardioverter defibrillator (ICD) technology extended ICD therapy to m ore than termination of hemodynamically unstable ventricular tachyarrhythmi as. It created the basis for dual chamber arrhythmia management in which de pendable detection is important for treatment and prevention of both ventri cular and atrial arrhythmias, Methods and Results : Dual chamber detection algorithms were investigated i n two Medtronic dual chamber ICDs: the 7250 Jewel AF (33 patients) and the 7271 Gem DR (31 patients), Both ICDs use the same PR Logic algorithm to int erpret tachycardia as ventricular tachycardia (VT), supraventricular tachyc ardia (SVT), or dual (VT + SVT), The accuracy of dual chamber detection was studied in 310 of 1,367 spontaneously occurring tachycardias in which rate criterion only was not sufficient for arrhythmia diagnosis. In 78 episodes there was a double tachycardia, in 223 episodes SVT was detected in the VT or ventricular fibrillation zone, and in 9 episodes arrhythmia was detecte d outside the boundaries of the PR Logic functioning. In 100% of double tac hycardias the VT was correctly diagnosed and received priority treatment. S VT was seen in 59 (19 %) episodes diagnosed as VT, The causes of inappropri ate detection were (1) algorithm failure (inability to fulfill the PR<RP co ndition in atrial tachyarrhythmias with 1:1 AV conduction, and far-field R wave sensing intermittently present during sinus tachycardia); (2) programm ing settings (atrial fibrillation/atrial flutter with ventricular rate abov e the SVT limit); and (3) algorithm limitations (atrial tachycardia with ve ntricular rate around the shortest programmable SVT limit and SVT redetecti on following VT therapy). Programming measures improved detection ability i n 13 of 59 of inappropriately detected arrhythmias. Conclusion: Dual chamber detection algorithms evaluated in a subset of diag nostically difficult arrhythmias allow safe detection of double tachycardia s but require further extension and programmability to improve VT:SVT discr imination rules.