Asian Cardiovasc Thorac Ann 2001;9:119-122
© 2001 Asia Publishing EXchange Pte Ltd
Second Chinese National Registry of Catheter Ablation of Tachyarrhythmia
Hu Da Yi, MD
Department of Cardiology
People's Hospital of Peking University
Beijing, People's Republic of China
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For reprint information contact: Hu Da Yi, MD Tel: 86 10 6879 2845 Fax: 86 10 6879 2845 email: heart{at}public.fhnet.cn.net Department of Cardiology, People's Hospital of Peking University, No. 11 Xizhimen Nandajie, Beijing 100044, People's Republic of China.
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Abstract
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The Chinese national registry of radiofrequency catheter ablation of tachyarrhythmias included data from 134 hospitals over 3 years from January 1995. Ablation was used in 24,343 patients, with 97% success, 3.1% recurrence, 0.95% complications, and 0.02% mortality overall. Accessory pathway ablation was performed in 15,617 patients (64.2%) with atrioventricular reciprocating tachycardia (97% success, 2.8% recurrence, 1% complications). The 6,746 patients (27.7%) with atrioventricular nodal reentrant tachycardia underwent slow pathway ablation (98% success, 2.7% recurrence, 1% complications). Focal ablation in the right or left ventricle was attempted in 1,025 patients (4.2%) with idiopathic or organic ventricular tachycardia (87% success, 6.8% recurrence, 0.5% complications). The 419 patients with atrial tachycardia underwent atrial focal ablation (84% success, 9.9% recurrence, 0% complications). Focal or linear ablation of the isthmus was conducted in 366 patients with atrial flutter (89% success, 10% recurrence, 1.1% complications). Atrioventricular junction ablation was used for rate control in 170 patients with atrial fibrillation (99% success). Multiple atrial linear ablations for rhythm control were 56% successful. Success rates and incidence of complications depended on the type of tachyarrhythmia, and remained constant over the 3 years. Further improvements in technique are needed to improve success rates and decrease the incidence of complications.
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Introduction
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In 1995, the Chinese Society of Pacing and Electro-physiology (CSPE) conducted the first national registry on radiofrequency catheter ablation (RFCA) of tachy-arrhythmia in the mainland of China.1,2 The results summarized the overall outcomes of RFCA up to 1994. To monitor the changes in the practice of RFCA since then, CSPE compiled a second national registry of RFCA in 1999.
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Patients and Methods
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All patients who underwent RFCA to cure or palliate tachyarrhythmia from January 1, 1995 to December 31, 1998, were selected for the collection of registry data. The CSPE identified all electrophysiological laboratories performing RFCA in the mainland of China. Forms with a simple and uniform configuration were sent to the directors of all 160 electrophysiology laboratories; 134 laboratories voluntarily participated in the registry. Data were collected by 2 cardiologists familiar with RFCA. Results of the primary RFCA procedure only were recorded in cases of multiple RFCA procedures. Detailed information on the results of electrophysiological studies was not requested in order to encourage participation. All data were analyzed with SPSS version 8.0 (SPSS, Chicago, IL, USA) software.
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Results
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There were 24,343 patients with various types of tachyar-rhythmia who were treated by RFCA. The ablation was acutely successful in 23,622 patients, giving an overall rate of success of 97%. Recurrence during follow-up of more than 6 months was reported in 735 patients, with an overall rate of recurrence of 3.1%. Symptomatic complica-tions were identified in 232 patients (0.95%), including 4 deaths (0.02%) related to the ablation procedure. Most laboratories (108/134, 81%) performed the ablation procedure using domestic electrophysiological recorders and radiofrequency generators.
The majority of patients (15,617, 64.2%) underwent accessory pathway ablation for atrioventricular recipro-cating tachycardia (AVRT). Ablation of slow or fast pathways for treatment of atrioventricular nodal reentrant tachycardia (AVNRT) was attempted in 6,746 (27.7%) patients. The other types of tachyarrhythmia ablated were idiopathic ventricular tachycardia in 961 patients (3.9%), atrial tachycardia in 419 (1.7%), atrial flutter in 366 (1.5%), atrial fibrillation in 170 (0.7%), and ventricular tachycardia associated with structural heart disease in 64 patients (0.3%).
The outcomes of RFCA for supraventricular tachyar-rhythmias are summarized in Table 1
. The results showed variable rates of success, recurrence, and complications among the different types of tachyarrhythmia. The highest success rate was achieved in ablation of accessory pathways and the lowest success rate was found in ablation of atrial tachycardia. Patients who underwent ablation for atrial flutter had the highest rate of recurrence of arrhythmia. The recurrence rates of AVRT and AVNRT were low in patients who underwent accessory pathway and slow pathway ablation.
Ablation was attempted in 11,373 patients with left-sided accessory pathways and 4,244 patients with right-sided accessory pathways, regardless of free wall or septum. Comparing left and right accessory pathway ablation, the rate of success was higher for left-sided ablation (11,204/11,373 versus 4,018/4,244 or 98.5% versus 94.7%; p < 0.01), the rate of recurrence was lower for left-sided ablation (203/11,204 versus 223/4,018 or 1.8% versus 5.6%; p < 0.01), and the incidence of complications showed no significant difference (116/11,373 versus 34/4,244 or 1% versus 0.8%; p > 0.05) between left and right RFCA.
The highest incidence of complications occurred in patients who underwent ablation for atrial fibrillation. The recurrence rate after ablation for atrial fibrillation was 0%; since the majority of the patients undergo atrioventricular (AV) nodal modification for rate control, no specific criteria for the recurrence of AV conduction have been developed. For control of ventricular rate during atrial fibrillation, AV nodal modification had a similar success rate (122/123, 99.2%) to that of AV junctional ablation (30/31, 96.8%). For atrial fibrillation, 16 patients underwent multiple linear ablation of the atria with a lower success rate (9/16, 56.3%). No patient had undergone focal ablation for atrial fibrillation by the end of 1998.
The majority of patients who underwent RFCA for ventricular tachyarrhythmia suffered from idiopathic left or right ventricular tachycardia (Table 2). The success rate was higher (853/961, 88.8%) and the recurrence rate was lower (50/853, 5.9%) in patients without structural heart disease compared to those with structural heart disease (success in 43/64, 67.2%; recurrence in 10/43, 23.3%). Patients with idiopathic left ventricular tachy-cardia had a higher success rate and lower recurrence rate than those with idiopathic right ventricular tachycardia. Ablation of ventricular tachycardia tended to have a better outcome when associated with cardiomyopathy rather than chronic myocardial infarction.
Significant complications occurred in 232 patients (Table 3), including 4 procedure-related deaths from third-degree AV block in 1 patient, pulmonary embolism in 1, cerebral embolism in 1, and acute myocardial infarction in the other. Complications of peripheral arteries and veins included thrombosis, arteriovenous fistula, and bleeding. Significant injury to the subclavian artery and pulmonary embolism were infrequent. Rare complications were reported in 18 patients (sinoatrial block, seconddegree AV block, hemathorax, and mediastinal hematoma).
The results were compared in pediatric patients (aged 14 years or less) and adults (Table 4). Pediatric patients had comparable rates of success and complications to those of adults, but a higher recurrence rate was noted in the pediatric age group.
The incidence of success, recurrence, and significant complications were compared among laboratories that performed less than 100 procedures (group 1), from 101 to 500 procedures (group 2), and over 500 procedures (group 3). The greatest number of procedures were recorded in the few centers with the highest volume of cases (Table 5). There were no significant differences in recurrence or mortality rates among the 3 groups, but group 3 showed a higher success rate and a lower incidence of complications than group 2 (Table 5).
In Table 6, the ablation outcomes are summarized by year from 1995 to 1998. Despite technological developments in electrophysiology and ablation, no notable changes in the overall outcomes of ablation occurred during these years.
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Discussion
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Since the introduction of RFCA for tachyarrhythmias, several registry studies have been reported. Surveys of ablation practice have mainly been carried out in Europe and North America.3–5 This second Chinese national registry study updates ablation practice in the mainland of China since the first survey conducted in 1995.2 Changes since the first survey include an increase in the number of laboratories performing RFCA and more laboratories using domestic equipment. The number of ablations for atrial flutter, atrial fibrillation, and ventricular tachycardia associated with structural heart disease continued to increase but the overall outcomes remained constant over the years.
The North American registry of catheter ablation was reported recently.5 Although the overall outcomes were compatible, a much larger number of patients (24,343) were involved in this study compared to the North American registry (3,357).5 A marked difference can be seen in the types of tachyarrhythmia requiring RFCA in the North American and Chinese registries. In North America, AVNRT accounted for the greatest number of procedures (36%), followed by accessory pathway ablation (20%), and AV junctional ablation (19%) for rate control. In China, the majority of patients (64.2%) underwent accessory pathway ablation, followed by ablation for AVNRT (27.7%); AV junctional ablation for rate control during atrial fibrillation was rare (0.13%, 10th in order of frequency). Although no direct comparison could be made between the North American and Chinese registries, the differences in outcome suggest a big difference in the practice of RFCA.
Compared to other registry studies, this study suffered from several limitations. First, no resources were available to check the accuracy of the forms submitted from various laboratories. Second, not all laboratories performing RFCA participated in the registry. Third, the incidence of com-plications might be underreported due to police scrutiny of hospitals. Fourth, detailed information on electro-physiological studies, follow-up, and drugs used were not included in this registry. Thus, effects on outcome of the mechanisms of arrhythmias, use of antiarrhythmic drugs, and anticoagulant therapy could not be determined. In spite of these serious limitations, the data appear to be consistent with those obtained from other parts of the world.
The results of this study confirm the efficacy and safety of RFCA performed in the mainland of China. The updated outcomes since 1995 suggest that the success rate and incidence of complications depend on the nature of the tachyarrhythmia and they remained constant over the years. Improvements in technique are needed to further increase the success rate and decrease the incidence of complications, especially for ablation of complex arrhyth-mias such as atrial fibrillation and ventricular tachycardia associated with structural heart diseases.
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References
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Hu DY. The data summary on radiofrequency catheter ablation for tachyarrhythmias in China. Chinese J Card Pacing Electrophysiol 1996;10:120–1.
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Hu DY. National survey on catheter ablation in China. Asian-Pacific Soc Intervent Cardiol Newsletter 1996;3: 2–4.
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Scheinman MM. NASPE survey on catheter ablation. Pacing Clin Electrophysiol 1995;18:1474–8.[Medline]
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Hindricks G for the Multicentre European Radiofrequency Survey (MERFS) Investigators of the Working Group on Arrhythmias of the European Society of Cardiology. The Multicentre European Radiofrequency Survey (MERFS): complications of radiofrequency catheter ablation of arrhythmias. Eur Heart J 1993;14:1644–53.[Abstract/Free Full Text]
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Scheinman MM, Huang S. The 1998 NASPE prospective catheter ablation registry. Pacing Clin Electrophysiol 2000; 23:1020–8.[Medline]
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Abstract
Introduction
