Heart Rate Turbulence after Ventricular Pacing Trains During Programmed Ventricular Stimulation

Background: This study tested the hypothesis that heart rate turbulence (HRT) following ventricular pacing trains depends on train cycle length, presence of retrograde ventriculoatrial (VA) conduction, and left ventricular (LV) function.
Methods: We analyzed digital recordings of programmed ventricular stimulation (PVS) performed in 82 patients (57 men) referred for electrophysiologic studies of ventricular arrhythmias, whose mean age was 64 ± 12 years and LV ejection fraction (EF) was 47 ± 15%. Profiles of sinus RR intervals after all available 8-beat ventricular pacing trains (600-and 400-ms) were averaged. Heart rate turbulence slope (HRTS) was analyzed as the maximum positive slope of a regression line through a sequence of 2–5 (HRTS2 - HRTS5) consecutive RR intervals within the first 5 RR intervals after the pacing train.
Results: Dynamics of RR intervals had biphasic and monophasic patterns, in patients with and without VA conduction, respectively. Sinus nodal response was less prominent after 600-ms than 400-ms pacing trains. After 400-ms pacing trains, HRTS was significantly shallower in patients with LVEF ≤40% than in those with LVEF >40%. HRTS4 was the best discriminator between the two groups (6.8 ± 8.6 ms/RR vs 19.6 ± 26.0 ms/RR, P = 0.017).
Conclusion: In patients with VA conduction, HRT after ventricular pacing trains reflects a combination of vagal withdrawal due to transient hypotension and suppression of sinus node automaticity. Attenuation of vagal modulation was detected in patients with LV dysfunction during standard PVS.     

Real‐World Safety and Effectiveness Outcomes of a Zotarolimus‐Eluting Stent: Final 3‐Year Report of the RESOLUTE International Study

Objectives

We evaluated the safety and effectiveness of the Resolute? zotarolimus‐eluting stent (R‐ZES) in real‐world clinical practice through 3 years.

Background

A randomized comparison of the R‐ZES and the XIENCE V? everolimus‐eluting stent showed no difference in any outcomes through 3‐year follow‐up in high‐volume academic centers. RESOLUTE International is a confirmatory trial designed to evaluate the R‐ZES in real‐world clinical practice.

Methods

RESOLUTE International is a single arm, observational trial that enrolled 2,349 patients from 88 centers with only a few inclusion and exclusion criteria. The primary end‐point was the composite of cardiac death and target vessel myocardial infarction (TV‐MI) at 1 year. Secondary end‐points include target lesion failure (TLF), target vessel revascularization (TVR), and their components, and stent thrombosis (ST).

Results

At 3 years 97.2% of patients completed clinical follow‐up. The mean age was 63.4 ± 11.2 years, 77.8% were male, and 30.4% had diabetes. The average number of stents per patient was 1.6 ± 1.0; and mean stent length was 30.9 ± 20.5 mm. Dual antiplatelet therapy was used in 91.1% of patients at 1 year, 43.0% at 2 years, and 34.6% at 3 years. Cardiac death and TV‐MI occurred in 161 patients (7.0%). There were 6 (0.3%) very late ST events for a total ST rate of 1.1% through 3 years. The rates of clinically driven target lesion revascularization (TLR), TVR, and TLF were 5.7%, 7.4%, and 11.4%, respectively.

Conclusions

The safety and effectiveness of the R‐ZES through 3 years in this real‐world all‐comer study was consistent with previously reported all‐comer trials. (J Interven Cardiol 2013;26:515‐523)

     

A Theoretical and Experimental Analysis of Radiofrequency Ablation with a Multielectrode,Phased, Duty‐Cycled System

Background: The development of a unique radiofrequency (RF) cardiac ablation system, for the treatment of cardiac arrhythmias, is driven by the clinical need to safely create large uniform lesions while controlling lesion depth. Computational analysis of a finite element model of a three‐dimensional, multielectrode, cardiac ablation catheter, powered by a temperature‐controlled, multiphase, duty‐cycled RF generator, is presented. Methods: The computational model for each of the five operating modes offered by the generator is compared to independent tissue temperature measurements taken during in vitro ablation experiments performed on bovine myocardium. Results: The results of the model agree with experimental temperature measurements very closely—the average values for mean error, root mean square difference, and correlation coefficient were 1.9°C, 13.3%, and 0.97, respectively. Lesions are shown to be contiguous and no significant edge effects are observed. Conclusions: Both the in vitro and computational model results demonstrate that lesion depth decreases consistently as the bipolar‐to‐unipolar ratio increases—suggesting a clinical application to potentially control lesion depth with higher fidelity than is currently available. The effect of variable design parameters and clinical conditions on RF ablation can now be expeditiously studied with this validated model. (PACE 2010; 33:1089–1100)     

Catheter Ablation of Focal Atrial Tachycardia from the Aortic Cusp: The Role of Electroanatomic Mapping and Intracardiac Echocardiography

Catheter ablation of periatrioventricular (peri‐AV) nodal atrial tachycardias (AT) from the noncoronary aortic cusp (NCC) can be challenging due to the close proximity of the AV node In such cases, intracardiac echocardiography (ICE) together with three‐dimensional mapping system can be helpful in guiding the ablation catheter and in assessing the anatomic relationship of the aorta to the surrounding structures. We report two patients with AT originating near the AV node who underwent successful catheter ablation from the NCC. ICE proved useful in positioning the ablation catheter within the aortic cusps. Electroanatomic mapping enabled tagging the earliest activation site and renavigation back. (PACE 2013; 36:e19–e22)