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Efficacy and safety of an irrigated-tip catheter for the ablation of accessory pathways resistant to conventional radiofrequency ablation
Conclusion: Successful ice mapping and cryothermal ablation of AVNRT is feasible with transvenous catheter cryoablation. Perspective: The main advantage of cryoablation over radiofrequency ablation of AVNRT may be the ability to avoid permanent high-degree AVB. Because the efficacy of radiofrequency ablation of AVNRT is high (⬎95%) and the incidence of AVB is low (⬍2%), a very large-scale study will be needed to determine which technique is more effective or safer. FM
sample size, additional studies are needed to confirm the safety of these larger lesions. FM
Genotype-Phenotype Correlation in the Long-QT Syndrome Schwartz PJ, Priori SG, Spazzolini C, et al. Circulation 2001;103: 89 –95. Study Question: Are the three major genotypes of the congenital long-QT syndrome (LQTS) associated with particular triggers for cardiac events? Methods: Information was gathered on the triggers that were associated with syncope, cardiac arrest or sudden death in 670 patients with LQTS who had been genotyped and found to have the LQT1, LQT2 or LQT3 mutation. The triggers were classified as exercise, emotion (including startle from auditory stimuli) and rest or sleep without arousal. The relationship between genotype and response to betablockers also was analyzed. Results: The most common genotype was LQT1 (55%), followed by LQT2 (35%) and LQT3 (10%). One or more triggers for a cardiac event could be identified in 70% of patients. In LQT1, 62% of events were triggered by exercise, and only 3% occurred during rest/sleep. In contrast, in LQT3 only 13% of events were triggered by exercise, and 39% occurred during sleep. In LQT2, the most common trigger was emotion (43%), followed by sleep/rest in 29%. There was a strong association between auditory triggers and LQT2, and between swimming as a trigger and LQT1. Beta-blockers were effective in preventing a recurrent cardiac event more frequently in LQT1 (81%), than in LQT2 (59%) or LQT3 (50%). Conclusions: The triggers associated with cardiac events in LQTS are gene-specific and not random. Beta-blockers are most efficacious in LQT1, in which exercise is the most common trigger for an arrhythmic event. Perspective: The optimal therapy for LQTS (beta-blocker, sodium channel blocker, pacemaker, left cardiac sympathetic denervation or internal cardioverter/defibrillator) is likely to be gene-specific. A prior study demonstrated that the three major genotypes of LQTS are associated with particular electrocardiographic manifestations. Taken with the results of the present study, it appears that an educated guess of the genotype may be possible based on evaluation of the clinical history and electrocardiogram. This may facilitate optimal therapy, at least until the specific mutation has been established by genetic testing. FM
Efficacy and Safety of an Irrigated-Tip Catheter for the Ablation of Accessory Pathways Resistant to Conventional Radiofrequency Ablation Yamane T, Jais P, Shah DC, et al. Circulation 2000;102:2565– 8. Study Question: Cooling at the electrode-tissue interface by irrigation with saline during delivery of radiofrequency (RF) energy allows deeper tissue penetration and the creation of larger lesions. The purpose of this study was to determine the clinical utility of the irrigated-tip catheter in patients in whom conventional RF ablation of an accessory pathway (AP) is ineffective. Methods: In a series of 301 patients who underwent conventional RF ablation of an AP, conduction through the AP persisted in 18 patients (6%), despite a mean of 12 applications (range 5–25) of RF energy. The subjects of this study were these 18 patients. An irrigated-tip catheter was used to deliver RF energy at the best mapping site at which conventional RF delivery had been ineffective. RF energy was delivered using a power limit of 20 –50 W and a target temperature of 50°C, for up to 60 seconds. Results: RF ablation using the irrigated-tip catheter was effective in eliminating AP conduction in 17 of 18 patients (94%). The mean number of energy applications was 3.4 (range 1–15). There were no complications and no recurrences of AP conduction during a mean of 15 months of follow-up. Conclusion: RF ablation with an irrigated-tip catheter is safe and effective in patients with APs that are resistant to conventional RF ablation. Perspective: Some APs may not be within the reach of the relatively small lesion created with conventional RF ablation. This study demonstrates that the larger lesions created with an irrigated-tip catheter usually are effective in ablating these difficult-to-reach APs. However, because of the small
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sample size, additional studies are needed to confirm the safety of these larger lesions. FM
Genotype-Phenotype Correlation in the Long-QT Syndrome Schwartz PJ, Priori SG, Spazzolini C, et al. Circulation 2001;103: 89 –95. Study Question: Are the three major genotypes of the congenital long-QT syndrome (LQTS) associated with particular triggers for cardiac events? Methods: Information was gathered on the triggers that were associated with syncope, cardiac arrest or sudden death in 670 patients with LQTS who had been genotyped and found to have the LQT1, LQT2 or LQT3 mutation. The triggers were classified as exercise, emotion (including startle from auditory stimuli) and rest or sleep without arousal. The relationship between genotype and response to betablockers also was analyzed. Results: The most common genotype was LQT1 (55%), followed by LQT2 (35%) and LQT3 (10%). One or more triggers for a cardiac event could be identified in 70% of patients. In LQT1, 62% of events were triggered by exercise, and only 3% occurred during rest/sleep. In contrast, in LQT3 only 13% of events were triggered by exercise, and 39% occurred during sleep. In LQT2, the most common trigger was emotion (43%), followed by sleep/rest in 29%. There was a strong association between auditory triggers and LQT2, and between swimming as a trigger and LQT1. Beta-blockers were effective in preventing a recurrent cardiac event more frequently in LQT1 (81%), than in LQT2 (59%) or LQT3 (50%). Conclusions: The triggers associated with cardiac events in LQTS are gene-specific and not random. Beta-blockers are most efficacious in LQT1, in which exercise is the most common trigger for an arrhythmic event. Perspective: The optimal therapy for LQTS (beta-blocker, sodium channel blocker, pacemaker, left cardiac sympathetic denervation or internal cardioverter/defibrillator) is likely to be gene-specific. A prior study demonstrated that the three major genotypes of LQTS are associated with particular electrocardiographic manifestations. Taken with the results of the present study, it appears that an educated guess of the genotype may be possible based on evaluation of the clinical history and electrocardiogram. This may facilitate optimal therapy, at least until the specific mutation has been established by genetic testing. FM
Efficacy and Safety of an Irrigated-Tip Catheter for the Ablation of Accessory Pathways Resistant to Conventional Radiofrequency Ablation Yamane T, Jais P, Shah DC, et al. Circulation 2000;102:2565– 8. Study Question: Cooling at the electrode-tissue interface by irrigation with saline during delivery of radiofrequency (RF) energy allows deeper tissue penetration and the creation of larger lesions. The purpose of this study was to determine the clinical utility of the irrigated-tip catheter in patients in whom conventional RF ablation of an accessory pathway (AP) is ineffective. Methods: In a series of 301 patients who underwent conventional RF ablation of an AP, conduction through the AP persisted in 18 patients (6%), despite a mean of 12 applications (range 5–25) of RF energy. The subjects of this study were these 18 patients. An irrigated-tip catheter was used to deliver RF energy at the best mapping site at which conventional RF delivery had been ineffective. RF energy was delivered using a power limit of 20 –50 W and a target temperature of 50°C, for up to 60 seconds. Results: RF ablation using the irrigated-tip catheter was effective in eliminating AP conduction in 17 of 18 patients (94%). The mean number of energy applications was 3.4 (range 1–15). There were no complications and no recurrences of AP conduction during a mean of 15 months of follow-up. Conclusion: RF ablation with an irrigated-tip catheter is safe and effective in patients with APs that are resistant to conventional RF ablation. Perspective: Some APs may not be within the reach of the relatively small lesion created with conventional RF ablation. This study demonstrates that the larger lesions created with an irrigated-tip catheter usually are effective in ablating these difficult-to-reach APs. However, because of the small
ACC CURRENT JOURNAL REVIEW May/Jun 2001
74