A prospective study comparing the sensed R wave in bipolar and extended bipolar configurations: the PropR study.

BACKGROUND: Progress in implantable cardiac defibrillator (ICD) technology has allowed for switching the sensing polarity for the detection of ventricular fibrillation (VF). However, whether one sensing polarity confers additional advantage over the other is not known. OBJECTIVES: To determine whether one sensing polarity is superior to the other for the detection of VF. METHODS: Patients were enrolled into a prospective randomized study of sensing of VF and R waves in normal rhythm. Sensing of VF was determined by number of under sensed beats (USB), and time to detection of VF (TDVF). Each patient underwent ICD implantation followed by testing of the ICD. At each induction, patients were randomized to sensing in extended bipolar (EBP) or true bipolar (TBP) configuration. Additionally, R waves were compared at implant and at 1-month follow-up. RESULTS: A total of 50 patients were enrolled into the study. When evaluating the primary endpoint, no difference was found between USB in EBP or TBP configuration; 1.1 ± 1.2 beats versus 1.3 ± 1.3 beats; P = NS. Also, no difference was found between TDVF in EBP or TBP configurations; 5.9 ± 0.6 seconds versus 5.9 ± 0.6 seconds; P = NS. With regard to the secondary endpoints, there was no difference between R waves in EBP or TBP configurations at the time of implant 10.9 ± 4.8 mV versus 10.9 ± 4.8 mV P = NS; or at 1-month follow-up 12.4 ± 4.7 mV versus 12.0 ± 5.4 mV P = NS. CONCLUSIONS: There is no difference in the detection of VF between EBP or TBP configurations in patients undergoing ICD implantation.

Thermal mapping of right ventricular outflow tract tachycardia.

BACKGROUND: Acute and long-term success of catheter ablation of right ventricular outflow tract tachycardia (RVOT VT) may be limited by the inability to reproduce the arrhythmia at the time of activation (AM) and pace mapping (PM). We have observed early initiation of the clinical VT when subtherapeutic radiofrequency (RF) energy was applied to the target area (TA), defined as a 2-cm(2) area around a pace match. We describe a novel approach using thermal mapping (TM) to guide the ablation of RVOT VT. METHODS: Thirteen patients (10 female, mean age 46.2 +/- 13.7 years) with symptomatic VT of left bundle branch block (LBBB) inferior axis morphology and no structural heart disease underwent standard electrophysiologic evaluation with PM (n = 13), AM (n = 13), and 3D noncontact mapping (n = 4). Thermal mapping was performed after standard techniques failed to induce stable sustained VT for mapping in all 13 patients: RF was applied for 5-10 seconds in the TA to achieve a tip temperature of 45-50 degrees C. At sites where morphologically consistent with the clinical VT was induced, RF was applied at target temperature between 50 and 60 degrees C for 30-60 seconds. TM was repeated before and after intravenous Isoproterenol infusion until no further VT could be induced by low temperature application. RESULTS: Noninducibility was achieved in all 13 patients. During a mean follow-up of 29 months (9-69 months), all patients remain arrhythmia-free, off antiarrhythmic medications. CONCLUSION: Thermal mapping is a safe and effective adjunctive technique for the mapping and ablation of RVOT VT when sustained tolerated clinical VT cannot be induced.