| Long-standing persistent atrial fibrillation (LPAF) was defined as continuous AF lasting for more than1year without the presence of intermittent sinus rhythm. It is believed that circumferentialpulmonary vein isolation (CPVI) alone may be insufficient to achieve good effectiveness due to the existence of atrial remodeling caused by LPAF, and that substrate modification is necessary to have a better clinical result. Stepwise ablation (SA) approach became the mainstay of various approaches for LPAF ablation. However, insufficient data are available with respect to the severity and distribution of fibrosis of diseased atria, rendering the current non-individualized approaches for substrate modification controversial. In Part I of the thesis the voltages and abnormal electrograms were analyzed by means of high density electro-anatomical mapping and the severity of fibrosis of the diseased atria was graded. In part II of the thesis a novel individualized substrate modification (ISM) approach was devised and the clinical study was conducted to compare the safety and effectiveness of ISM with that of SA approach.Part I the study of substrate of left atrium in the setting of long-standing persistent atrial fibrillation.ObjectiveAtrial fibrosis can be caused by LPAF, and has significant impact on the clinical effectiveness of catheter ablation for LPAF. The aim of our study was to investigate the bipolar voltage of each mapping site and abnormal atrial electrograms in patients with LPAF by means of high-density electro-anatomical mapping and to grade the severity of the diseased left atrium.MethodsSixty-four patients with LPAF and60patients with left accessory atrioventricular pathway(LAAP) were enrolled. Three-dimensional mapping system-guided high density mapping was performed in sinus rhythm following the completion of circumferential pulmonary vein isolation for AF or LAAP ablation via transseptal approach. The whole left atrium anatomy was divided into seven segments:free anterior wall, septum, left atrial appendage, roof, postero-medium wall, postero-inferior wall, and mitral isthmus. The location, bipolar voltage and morphology of electrograms (single potential, short double potential, long double potential and fragmented potential) of each mapping site were documented and the difference of such parameters was compared between two groups.ResultsThere was statistically significant difference with respect to left atrial diameter and proportion of hypertension between two groups despite the similar age and sex. Mapping was performed in sinus rhythm in all patients. The mean mapping site acquired was223.8±32.2in LPAF group and210.7±9.2, P=0.01. The mean bipolar voltage in each one of seven segments was significantly lower, while the low potential zone (LPZ) area, left atrial volume and left atrial inner-superficial area was significantly larger in LPAF group than in LAAP group. The LPZ/inner-superficial area proportion was higher in LPAF group than in LAAP, which was=10%(mild) in26.6%of patients,>10%≦20%(moderate) in40.6%of patients,>20%≦35%(moderate to severe)in21.9%of patients and>35%(severe) in10.9%of patients in LPAF group, compared with<10%in all patients in LAAP group. The proportion of abnormal electrograms in each segment was higher in LPAF group than in LAAP group, while the average bipolar voltage was<0.5mV in both groups.ConclusionsThe mean bipolar voltage of left atrium was lower and the proportion of abnormal electrograms was higher in LPAF group than in LAAP group. The severity of diseased left atrium was graded as mild to moderate in two thirds of patients and as moderate to severe in the remaining one third of patients in LPAF group according to the LPZ/inner-superficial area proportion. These findings seem to provide meaningful information to a more individual rather than uniform ablation approach for treating LPAF. Part Ⅱ catheter ablation for the treatment of long-standing persistent atrial fibrillation:comparison between two substrate modification approaches.ObjectiveThe severity of fibrosis in the diseased atria varies dramatically in patients with long-standing persistent atrial fibrillation (LPAF). The current approaches applied in substrate modification during AF ablation remain controversial and are needed to be optimized. The aim of this study was to devise a novel approach for substrate modification and to evaluate the safety and effectiveness of this approach in LPAF ablation.MethodsOne hundred and twenty-four patients with LPAF were enrolled in this study. Sixty-four patients (41male, average age of62.8±10.6years) were assigned to the individualized substrate modification(ISM) group. The average duration of AF was40.8±38.1months in ISM group. Sixty patients with LPAF (35male, average age of59.7±6.4years) were allocated to stepwise ablation(SA) group. The mean duration of AF was32.8±15.9months. Substrate mapping was performed post-CPVI in ISM group, followed by left atrial roof ablation and ablation of abnormal electrograms and/or linear ablation in areas with low voltage, based on the severity of fibrosis in the left atrium. Multiple linear ablation in both atria and complex fractionated atrial electrograms (CFAEs) ablation was performed in SA group, following the completion of CPVI. The clinical effectiveness, safety, as well as the prevalence of recurrent atrial flutter/tachycardia was compared in two groups after the initial and repeated ablation procedures.ResultsThe ablation procedure was accomplished in all patients in two groups. The total procedural duration was significantly longer in SA group than in ISM group, while the duration of CPVI was comparable with100%success rate of PV isolation in two groups. AF was terminated or transitioned to flutter in15patients (25%) in SA group. Bidirectional block was achieved for Mitral isthmus in33(55%), for roof line in40(62.5%), and for cavo-tricuspid isthmus in57(95%) in SA group. AF was terminated in 1during CPVI in ISM group, and roof line block was established in41(68.3%)of patients in ISM group. The mean duration for substrate mapping and ablation was45.9±8.6min. Complications:Hematoma in iliac region in2in ISM group and mild pericardial effusion in3in SA group was treated conservatively. At the end of12months of follow-up, the clinical success ratewas65.6%in ISM group vs.45.0%in SA group after the initial procedure, P=0.03. The prevalence of atrial flutter/tachycardia was22.7%in ISM group vs.60.6%in SA group, P=0.01.Twelve (54.5%) patients in ISM group and19(57.6%) patients in SA group underwent re-ablation due to the recurrence of atrial tachy-arrhythmias (P=0.82). After repeated procedure, the overall clinical effectiveness was comparable between two groups (75%in ISM group vs.63.3%in SA group, P=0.14).ConclusionsThe approach of ISM is safe, simplied and time-saving in LPAF ablation; having a significantly higher clinical success rate and a dramatically lower rate of atrial flutter/tachycardia after initial ablation compared with the stepwise ablation approach. After reablation the clinical effectiveness was similar between two approaches. However, furtherstudies should be carried out to evaluate its efficacy and safety prior to possiblewide clinical practice. |
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