A 62-year-old recipient of a Virtuoso DR dual chamber ICD implanted for ischemic cardiomyopathy and sustained episodes of VT was complaining of palpitations. (Same patient as in tracing 21, presenting with syncope and palpitations.)
ATP is first line therapy for regular ventricular tachyarrhythmias at rates <250 bpm. However, in some patients, it may be ineffective or proarrhythmic, inducing life-threatening FVT or VF. The aggressiveness of ATP can be limited. In the last ramp delivered in this case, the coupling interval was 200 ms (300 bpm), and could have been limited. Programming a 5-10 J shock as first therapy instead of ATP is another option.
VT therapy is initially withheld because the rhythm is irregular; the stability criterion is programmed ON and overrides the PR Logic algorithm, which probably would have detected the VT. The stability algorithm does not suppress the therapy, and delays the VT detection until it becomes more regular. This episode lasted a total of 53 sec, explaining the palpitations reported by the patient before he lost consciousness, probably when the tachyarrhythmia accelerated.
