| Heart failure (HF) associated with arrhythmia is very common, in the past years, clinicians often regarded arrhythmias as a result of heart failure. However, in the clinical practice, it was often difficult to determine the causality relationship. With the development of cardiac electrophysiology and catheter ablation, more and more patients with arrhythmia were cured by catheter ablation, and cardiac enlargement and dysfunction were restored fully or partially, clinicians recognized that tachycardia might be the cause, and heart failure was secondary to it, which the concept of tachycardia-induced cardiomyopathy (tachycardia-induced cardiomyopathy, TIC) was made.Despite there has been 100 years of history after the discovery cardiomyopathy, tachycardia-induced cardiomyopathy has been understood well by clinicians. Most understandings about TIC came from animal models, the procedure of these animal experiments was that heart failure was caused by sustained rapid atrial or ventricular pacing for 1-2 months, then dilated cardiomyopathy was developed. Animal experiments showed that hemodynamic abnormalities emerged in the first 24 hours of rapid pacing and intracardiac filling pressures, cardiac output and changes of vascular resistance were usually terminated after rapid pacing. Although in some cases, normal levels ejection fraction might not be recovered to the normal level, and systolic dysfunction might persist. In humans, the true incidence of TIC has been unknown, because most of the literatures are retrospective analyses of a small sample or case reports, in addition, the incidence is also affected by the characters of TIC diagnosis which is a exclusive diagnosis, the impact of this characteristic, therefore, clinically, the incidence of TIC probably are underestimated the true incidence may be much higher than that of in the reported literatures. TIC can be caused by many types of tachycardia, including supra-ventricular, atrioventricular node, atrioventricular junction and ventricular tachycardia. However, the diagnosis of TIC can not be excluded in those patients with concomitant structural heart disease.Antiarrhythmic drugs, surgery and catheter ablation have become effective treatments for patients with TIC, especially the later two methods, which can reduce significantly left ventricular diameter than pre-treatment, and recover left ventricular function to normal. By controlling ventricular rate and/or heart rhythm, antiarrhythmic drugs improve left ventricular structure and function of TIC, however, the recurrence of tachycardia, heart failure and other adverse outcomes still occur. At present, surgery is no longer a good choose for patients with TIC because its big trauma and postoperative complications. Radiofrequency ablation has become the main treatment method for TIC. Studies have reported that there is a significant improvement of LVEF in most TIC patients accepting catheter ablation in 3-6 months, even in a week of a month after RFCA, and the LV function can return to normal in most patients. Consequently, current opinions is that TIC has a good clinical outcome after effective treatments. Nevertheless, echocardiographic findings revealed that the value of left ventricular structure parameters, including left ventricular end-diastolic diameter and/ or left ventricular end systolic volume index or left ventricular normal value, still higher than those of normal controls, which indicated that the patient with TIC persisted negative remodeling after treatment. Some literatures reported if the tachycardia recurred in patients with a medical history of TIC might lead the recurrent of TIC and heart failure, and this process occurred even faster and more severe comparing with the previous process, suggesting that despite the LVEF returned to the normal value after therapy, the persisting structural abnormality of left ventricle was regarded as the substrate of the recurrent heart failure.Sudden death of patients with TIC were reported in a few of studies. Although the cardiac structure and function had returned to normal level and had no recurrent heart failure or tachycardia, sudden death happened in some cases, considering the cause might be that these patients suffered previously from lower LVEF, higher NYHA grade of heart failure and other factors before RFC A, but the exact causes have not been identified. In addition, clinically, except the "pure" TIC, many patients are diagnosed as "impure" TIC which are simultaneously combined with other structural heart diseases (such as hypertension, diabetes, coronary heart disease, etc.). The diagnosis and treatment of "impure" TIC are influenced by combined factors. Therefore, an opinion has been proposed that the occurrence, development and outcome are unpredictable in patients with TIC influenced by different factors. To this day, there are no large-scale clinical research systems to solve this problem, therefore, the predictors of the degree of the recovery of LV systolic function and the course of myocardial recovery are lack of understandings.So far, although animal experiments and clinical studies have found that effective treatments for patients with TIC include the control of heart rate and/or control of heart rhythm, and most patients with TIC might had a better clinical outcome. However, clinically, a few patients still suffered sudden cardiac death, tachycardia recurrence, rapid deterioration of cardiac function and persistent negative ventricular remodeling after effective treatments.InstructionTachycardia-induced cardiomyopathy (TIC) is characterized by ventricular systolic dysfunction and congestive heart failure that are caused by persistent or highly frequent tachyarrhythmias with rapid heart rate. TIC is considered to be a rare cause of reversible left ventricular dysfunction. Current studies demonstrate that the maintenance of sinus rhythm is superior to ventricular rate control, and the left ventricular ejection fraction (LVEF) could be normalized after successful radiofrequency catheter ablation (RFCA). Although TIC is believed to be benign, several reports have described that sudden death and heart failure recurrence after normalization of cardiac function in a long-term follow-up. Despite that most reports of TIC are isolated case reports or small retrospective cohorts, there are some common characters and worth noting opinions. In order to further evaluate the effects of RFCA on LV structure and function of TIC, we sought to determine using meta-analysis approach. Moreover, the degree of recovery and its effective factors of LV dysfunction before and after RFCA, heart failure recurrence and sudden death were investigated in patients with different tachyarrythmias.Methods1. Search strategy:A thorough computer-based search was performed using MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials to identify trials in English language. Search terms included:(catheter ablation) AND ((tachycardia-mediated cardiomyopathy) OR (tachycardia-induced cardiomyopathy) OR tachycardiomyopathy OR(tachycardia-induced myopathy) OR (tachycardia AND cardiomyopathy)). No limit to the start date was applied, and the search was conducted up to June 1,2015.2. Trial selection:We included comparative studies (both randomized and non-randomized controlled trials). All published controlled clinical trials that provided original data on the effects of RFCA on LV diameter, and function in patients with TIC with a follow-up duration of 3 months or longer were collected. Furthermore, only studies with> 6 patients were considered eligible and all studies were published in English. When data were reported from overlapping study samples, the most recent study or the one with the highest number of patients was included in the analysis. If there were several different therapy methods in a same study, such as simple anti-arrhythmic drugs therapy or RFCA, we only exacted original data in patients with effective RFCA. The Single case reports and previous systematic reviews on TIC were excluded.3. Screening and quality assessment of documents. Design features of the research literatures, the basic characteristics of the patients with TIC, the left ventricular function and/or structure before and after RFCA were extracted. Review manager 5.3 statistical software was used for Meta analysis. Meta-analysis was conducted according to the randomized effects model, and original data were analyzed in heterogeneity, quantitative synthesis, and sensitivity. Effective amount was represented by weighted mean difference (WMD) and 95% confidence intervals (CI). Q value, P value (chi-square test) and I2 test were applied for heterogeneity test of the entry. According to study variables (duration of postoperative follow-up, different types of tachycardia, different degrees of cardiac dysfunction before RFCA), different subgroups were analyzed separately to explore possible sources of heterogeneity. Funnel plot was used to identify and assess bias.Result1.A total of 15 final trials including 428 participants with TIC were qualified for this meta-analysis.75%(n= 321) patients were male, and the average age at diagnosis was 47.84 years. Patients with supraventricular tachycardia induced TIC in 6 trials, ventricular tachycardia induced TIC in 5 trials, and both supraventricular tachycardia and ventricular tachycardia induced TIC in residual 4 trials were studied. In all subjects, patients with supraventricular tachycardia accounted for 63.8%(n= 273), and patients with ventricular tachycardia 36.2%(n= 155). The average duration of postoperative follow-up time was 3 to 72 months. About 5.1%(n= 22) patients recurred tachycardia after the last RFCA. The recurrence rate of TIC was 0.99%(n= 3), the mortality rate 2.3%(n= 7), of which,14.3%(n= 1) mortality was related directly to the cardiac complications.2.Meta-analysis(1) Compared with the pre-RFCA, there were significant improvements in the left ventricular systolic function and negative remodeling after RFCA. The left ventricular end-diastolic diameter (LVEDD) which represented left ventricular negative remodeling decreased significantly (WMD-4.82cm,95%CI,-7.98 to-1.66, P= 0.004) and the left ventricular ejection fraction (LVEF) which represented left ventricular systolic function increased significantly (WMD 19.62%,95%CI,17.20 to 22.03, P O.00001). There was a significant decrease in the ventricular rate (WMD-55.51bpm, 95%CI,-92.14 to-18.87, P<0.00001).(2) Subgroup analysis demonstrated that patients with supra-ventricular tachycardia (WMD 17.81%; 95% CI,13.89 to 21.73) and patients with ventricular tachycardia cardiomyopathy (WMD 17.88%; 95% CI,13.51 to 22.25) gained a similar benefits in the improvement of LV systolic function. There was no significant difference in the improvement of left ventricular systolic function after RFCA (WMD 17.85%; 95% CI, 15.08 to 20.62, P=0.98) between the two subgroups. There was significant difference (WMD 18.68%; 95%CI,16.02 to 21.33, P= 0.003) in the degree of improvement of LVEF between pre-RFCA LVEF≤35%(WMD 23.13%; 95%CI,20.28 to 25.98) and LVEF> 35%(WMD 17.04%; 95%CI,14.21 to 19.87) subgroups. Patients with pre-RFCA LVEF≤35% gained more benefits than those with pre-RFCA LVEF> 35%. Besides, patients with follow-up duration≤6 months (WMD 17.68%; 95% CI,14.15 to 21.20, P< 0.00001) after RFCA and follow-up duration> 6 months (WMD 20.53%; 95%CI,16.62 to 24.43, P< 0.00001) got a similar improvement of cardiac function (WMD 18.68%; 95%CI,16.02 to 24.43, P= 0.29).Conclusion1. Patients with TIC were more frequently male and supraventricular tachycardia was more common in the etiology of TIC than ventricular tachycardia.2. Patients with supraventricular tachycardia induced cardiomyopathy and those with ventricular tachycardia induced cardiomyopathy gained a similar benefit in the improvement of LV systolic function after RFCA.3.There was a significant improvement of left ventricular systolic function in all patients with TIC after RFCA, and the worse pre-RFCA LVEF, the more improvement of LVEF after RFCA.4. The left ventricular systolic function of the majority of TIC reversed to normal or improved at an maximum degree in six months or less after RFCA.5. Despite left ventricular function and structure can recover, a small part of patients still faced the risks of recurrent heart failure or sudden death. Therefore, long-term drug treatment of ventricular remodeling may be necessary to further reduce the incidence of clinical adverse outcomes after RFCA. |
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