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Precise localization of the site of origin of premature ventricular contractions (PVCs) before ablation can facilitate the planning and execution of the electrophysiological procedure.The purpose of this study was to develop a predictive model that can be used to differentiate PVCs between the left ventricular outflow tract and right ventricular outflow tract (RVOT) using surface electrocardiogram characteristics.A total of 851 patients undergoing radiofrequency ablation of premature ventricular beats from January 2015 to March 2022 were enrolled. Ninety-two patients were excluded. The other 759 patients were enrolled into the development (n = 605), external validation (n = 104), or prospective cohort (n = 50). The development cohort consisted of the training group (n = 423) and the internal validation group (n = 182). Machine learning algorithms were used to construct predictive models for the origin of PVCs using body surface electrocardiogram features.In the development cohort, the Random Forest model showed a maximum receiver operating characteristic curve area of 0.96. In the external validation cohort, the Random Forest model surpasses 4 reported algorithms in predicting performance (accuracy 94.23%; sensitivity 97.10%; specificity 88.57%). In the prospective cohort, the Random Forest model showed good performance (accuracy 94.00%; sensitivity 85.71%; specificity 97.22%).Random Forest algorithm has improved the accuracy of distinguishing the origin of PVCs, which surpasses 4 previous standards, and would be used to identify the origin of PVCs before the interventional procedure.

Wolff-Parkinson-White (WPW) concomitant with atrial tachyarrhythmia (ATA) has not been systemically characterized.Detailed electroanatomical mapping of the right atrium (RA) and/or left atrium (LA) was performed using three-dimensional mapping and the accessory pathway (AP) was mapped.WPW syndrome with ATA was diagnosed in 11 patients (median age 60 years). The characteristic of unidirectional anterograde conduction over the AP was displayed in nine patients, six of whom were intermittent. Sustained atrial tachycardia, that is, counterclockwise atrial flutter (AFL) with a median tachycardia cycle length (TCL) of 225 (220-275) ms, was mapped in eight patients; furthermore, "figure 8" right atrial reentry was mapped with TCL 250 ms in one patient with a surgical history of ventricular septal defect repair. The remaining two patients underwent mitral annulus-dependent AT after paroxysmal atrial fibrillation (PAF) ablation and LA micro-reentry AT, respectively. In four patients, the location of the APs was left posterior. Left-lateral APs were identified in four patients. The locations of the APs in the remaining three patients were the right posterior and middle septum. All ATAs and APs were successfully ablated. After a median follow-up of 37 (15-72) months, no anterograde conduction over the AP was recorded, new onset of PAF was recorded in three patients, and all of them underwent circumferential pulmonary vein isolation.WPW with concomitant ATA frequently had continuous anterograde conduction over the AP with a rapid ventricular rate. Most WPWs displayed the characteristic of unidirectional anterograde conduction.

Background Atrial tachycardias (ATs) frequently develop after a surgical Maze procedure. We aimed to elucidate the electrophysiologic mechanisms and their arrhythmogenic substrates of these ATs. Methods and results We retrospectively reviewed 20 patients (14 females, mean age of 55.5 ± 8.6 years) with post-Maze ATs who underwent high-resolution mapping at three institutions. The slow conduction areas, reentry circuits, voltage signals, complex electrograms, and their correlation with the surgical incisions and lesions placed in the surgical Maze procedures were analyzed. Thirty-six ATs with a mean cycle length of 260.0 ± 67.6 ms were mapped in these patients. Among them, 22 (61.1%) were anatomical macro-reentrant ATs (AMAT), 12 (33.3%) non-AMATs (localized ATs), and 2 (5.6%) focal ATs, respectively. Epicardial conduction bridges were observed in 6/20 (30.0%) patients and 7/36 (19.4%) ATs. Different arrhythmogenic substrates were identified in these ATs, including slow conduction regions within the previous lesion areas or between the incisions and anatomical structures, the prolonged activation pathways caused by the short lesions connecting the tricuspid annulus, and the circuits around the long incisions and/or lesions. Conclusions Reentry is the main mechanism of the post-Maze ATs. The pro-arrhythmic substrates are most likely caused by surgical incisions and lesions. The slow conduction regions and the protected channels yielded from these areas are the major arrhythmogenic factors.

Idiopathic epicardial ventricular arrhythmias (VAs) are clustered in the areas of the summit and crux. This study was to report a group of idiopathic epicardial VAs remote from the summit and crux areas.In total, 9 patients (6 males, mean age 32 ± 13 years) were enrolled. The locations were identified by epicardial mapping and ablation. The electrocardiographic and electrophysiological characteristics were compared to those of 9 patients who had VAs ablated at the opposite endocardial site.VAs were identified at the epicardium, with 4 patients had VAs located at the inferior wall, one at the anterior wall, one at the apex and 3 patients had VAs at the lateral wall. A "QS" type at the location-related leads was the only identified surface electrocardiogram indication suggesting epicardial origin (compared to that of the controls, 100% vs 0%, p0.001). Endocardial and epicardial mapping revealed pre-maturities of -11 ± 4 ms and -25 ± 8 ms, respectively (VS. -28 ± 8 ms revealed by endocardial mapping in control patients, p0.001 and p=0.389, respectively). All of the study cases demonstrated an "rS" pattern in the endocardial unipolar electrogram. Acute and long-term successful ablation (a median of 11 months of follow-up) was achieved in all patients without complications.A distinct group of idiopathic VAs remote from the summit and crux areas warranting ablation by a subxiphoid approach were identified. Morphological ECG features of a "QS" type among the location-related grouped leads combined with the mapping findings helped in the identification of the epicardial site of origin.

Introduction: For those cardiac resynchronization therapy (CRT) candidates who experience left-ventricular (LV) lead placement failure or underwent concomitant cardiac surgeries, surgical placement of epicardial LV lead guided by electroanatomic mapping may be a promising alternative. Methods: Electroanatomic mapping was used to guide positioning of the LV lead through a surgical approach. The LV lead was placed at the region with the latest local LV activation and normal voltage, away from the scar. Results: From April 2010 to September 2018, 10 consecutive patients (3 female) underwent surgical epicardial LV lead implantation. Among them, 3 had other surgical indications simultaneously (including 1 CRT non-responder), and 7 had failed transvenous LV lead placement. After CRT, the QRS duration was shortened from 149.3 ± 20.4 ms to 125.1 ± 15.2 ms (p = 0.01). At 6 months, the LV ejection fraction was significantly improved and remained stable in the follow-up (FU) period thereafter (baseline vs. 6 months, 31.0 ± 8.3% vs. 42.2 ± 13.4%, p = 0.006). Other parameters, including the threshold and impedance of the LV lead, were also stable at a mean FU of 755 ± 406 days, and the NYHA functional classification decreased from 2.9 ± 0.7 to 1.8 ± 0.8 (p = 0.002). Conclusions: Placement of an epicardial LV lead guided by electroanatomic mapping could be used as an adjunctive strategy in patients who were unable or refractory to conventional CRT therapy. This approach could also be applied in patients who had other surgical indications at the same time.

BackgroundPulmonary vein isolation (PVI) is the standard ablation strategy for treating atrial fibrillation (AF). However, the optimal strategy of a repeat procedure for PVI non-responders remains unclear.ObjectiveThis study aims to investigate the incidence of PVI non-responders in patients undergoing a repeat procedure, as well as the predictors for the recurrence of repeat ablation.MethodsA total of 276 consecutive patients who underwent repeat ablation from August 2016 to July 2019 in two centers were screened. A total of 64 (22%) patients with durable PVI were enrolled. Techniques such as low voltage zone modification, linear ablation, non-PV trigger ablation, and empirical superior vena cava (SVC) isolation were conducted.ResultsAfter the 20.0 ± 9.9 month follow-up, 42 (65.6%) patients were free from atrial arrhythmias. A significant difference was reported between the recurrent and non-recurrent groups in non-paroxysmal AF (50 vs. 23.8%, p = 0.038), diabetes mellitus (27.3 vs. 4.8%, p = 0.02), and empirical superior vena cava (SVC) isolation (28.6 vs. 60.5%, p = 0.019). Multivariate regression analysis demonstrated that empirical SVC isolation was an independent predictor of freedom from recurrence (95% CI: 1.64–32.8, p = 0.009). Kaplan-Meier curve demonstrates significant difference in recurrence between empirical and non-empirical SVC isolation groups (HR: 0.338; 95% CI: 0.131–0.873; p = 0.025).ConclusionAbout 22% of patients in repeat procedures were PVI non-responders. Non-paroxysmal AF and diabetes mellitus were associated with recurrence post-re-ablation. Empirical SVC isolation could potentially improve the outcome of repeat procedures in PVI non-responders.

BackgroundLeft anterior fascicle (LAF) premature ventricular contractions (PVC) are rarely reported. We described the electrocardiographic and electrophysiological characteristics of PVCs originating from LAF and evaluated the results of catheter ablation.MethodsThe baseline AH and HV intervals were recorded during normal sinus rhythm (NSR), and the HV interval of LAF-PVC was measured during the procedure. During the index procedure, the conduction interval from the earliest Purkinje potential (PP) site to the His was labeled as time A, the conduction interval from the earliest site to the onset of the QRS as time B, then the HV interval during NSR (HVNSR) is A + B, and the HV interval during PVC (HVPVC) is B-A; a predicted PP time was calculated using HVNSR and HVPVC. The calculated formula is as follows: Predicted target PP = (HVNSR + HVPVC)/2. During the repeat procedure, the mapping strategy only focuses on the earliest retrograde PP due to the injury or block of LAF sustained at the index procedure.ResultsNotably, 24 patients with LAF-PVC were included. The ECG characteristics of PVC exhibited right bundle branch block (RBBB) morphology with right-axis deviation (RAD) in 18 patients and only RAD in 6 patients. The QRS durations of NSR and PVC were 78.8 ± 7.9 and 106.8 ± 12.3 ms, respectively. There was no significant difference between the predicted and mapped PP site (31.5 ± 8.1 vs. 30.6 ± 7.8 ms; P = 0.17). There was a significant difference between the mean axis deviation before and after ablation (46.3 ± 25.4° vs. 18.3 ± 44.1°; P = 0.001); however, only 10 patients had a complete LAF block. Eight patients had a recurrence, the QRS morphology of LAF-PVC became narrower (95.9 ± 17.2 vs. 105.3 ± 16.9 ms, P = 0.003), and 4 patients’s PVC QRS morphology was similar to NSR. During the repeat procedure, the earliest retrograde PP interval was longer than the index procedure in four patients (12.0 ± 1.9 vs. 37.8 ± 1.1 ms; P < 0.001).ConclusionThe target PP site for ablation of the LAF region can be calculated using the HV interval during NSR and PVC at the index procedure. The mapping strategy at repeat procedures focused on the earliest retrograde PP interval.

Re-ablation has an important role in the control of recurrent atrial fibrillation (AF) post the first ablation. The present study was to report the outcome of AF re-ablation for patients who recurred after initial ablation, and to characterize the clinical and electrophysiological features predicting recurrence after redo ablation. From January 2012 to May 2017, patients undergoing re-ablation for AF in our hospital were consecutively enrolled. Clinical and electrophysiological data for the initial and second procedure were collected retrospectively and prospectively, respectively. All patients were followed up for one year and recurrences during the time were reported. Totally 259 patients entered into the analysis (age, 58.4 ± 10.5 years; 169 men). At the end of one-year follow-up, 85 patients recurred with atrial arrhythmias (32.8%). In the multivariate analysis, higher CHA2DS2-VASC score (p = 0.023, 95% CI 1.03–1.53) and shorter time to recurrence after the initial ablation (p = 0.001, 95% CI 0.93–0.98) were clinical factors predictive of one-year recurrence after the repeat ablation. The reconnection of the right pulmonary vein (PV) (p = 0.034, 95% CI 0.31–0.96) and the absence of not eliminated non-PV trigger at the second procedure (p = 0.032, 95% CI 1.25–142.80) independently predicted the better re-ablation outcome. About one-third of patients recurred after one year following re-ablation. CHA2DS2-VASC score and time to recurrence after the initial ablation were independent clinical factors predicting recurrence. Also, electrophysiological findings during the repeat ablation (the right PV reconnection and absence of not eliminated non-PV trigger) were associated with better outcome during one year of follow-up.

Background: New-onset atrial fibrillation (AF) after ablation of typical atrial flutter (AFL) is not rare. This study aimed to investigate the predictive value of electrocardiographic parameters on new-onset AF post-typical AFL ablation.Methods: A total of 158 consecutive patients (79.1% males, mean age 57.8 ± 14.3 years) with typical AFL were enrolled between January 2012 and August 2017 in this single-center study. Patients with a history of AF before ablation were excluded. ECGs during sinus rhythm (SR) and AFL were collected. The duration of the negative component of flutter wave in lead II (DFNII), proportion of the DFNII of the total circle length of AFL (DFNII%), amplitude of the negative component of flutter wave in lead II (AFNII), duration (DPNV1), and amplitude (APNV1) of negative component of the P wave in lead V1, and P wave duration in lead II (DPII) during sinus rhythm were measured.Results: During a median follow-up of 26.9 ± 11.8 months, 22 cases (13.9%) developed new-onset AF. DFNII was significantly longer in patients with new-onset AF compared to patients without AF (114.7 ± 29.6 ms vs. 82.7 ± 12.8 ms, p < 0.0001). AFNII was significantly lower (0.118 ± 0.034 mV vs. 0.168 ± 0.051 mV, p < 0.0001), DPII (144.21 ± 23.77 ms vs. 111.46 ± 14.19 ms, p < 0.0001), and DPNV1 was significantly longer (81.07 ± 16.87 ms vs. 59.86 ± 14.42 ms, p < 0.0001) in patients with new-onset AF. In the multivariate analysis, DFNII [odds ratio (OR), 1.428; 95% CI, 1.039–1.962; p = 0.028] and DPII (OR, 1.429; 95% CI, 1.046–1.953; p = 0.025) were found to be independently associated with new-onset AF after typical AFL ablation.Conclusion: Parameters representing left atrial activation time under both the SR and AFL were independently associated with new-onset AF post-typical AFL ablation and may be useful in risk prediction, which needs to be confirmed by further prospective studies.

Background The literature on laminopathy with ventricular phenotype is extensive. However, the pathogenicity of LMNA variations in atrial lesions still lacks research. Objective To characterize the atrial phenotype and possible mechanisms in a large Chinese family with heart-hand syndrome carrying LMNA missense variant in rod 2B domain (c.1003C>T p.R335W). Methods Clinical characteristics were collected based on the pedigree investigation. Comprehensive functional analyses, including molecular dynamic simulation, cellular, and animal functional assays, determined the pathogenicity in atrial myopathy. Results In the pedigree investigation, 6/13 of the mutation carriers showed heterogeneous cardiac phenotypes, and eight carriers also had brachydactyly. In silico molecular dynamics simulations predicted increased binding energy of R335W mutant lamin A. Atrial cardiomyocytes (HL-1, hiPSC-derived atrial cardiomyocytes) expressing R335W showed abnormal nuclear morphology, compromised DNA repair, and dysfunctional contraction. Adult zebrafish expressing mutant lamin A showed increased P wave duration in the electrocardiogram, decreased A peak velocity in echocardiography, and atrial lesions under the transmission electron microscope. Conclusion The LMNA p.R335W mutation leads to a familial heart-hand syndrome characterized by an overlapping phenotype of prominent atrial lesions and brachydactyly. The unstable lamin dimerization and impaired DNA repair are possible mechanisms underlying cardiac phenotypes. Our findings consolidated the genetic role in the course of atrial arrhythmias and cardiac aging, which is helpful to the diagnosis and treatment of cardiac laminopathy.

The role of catheter ablation as an adjunct and alternative to ICD implantation is not known in patients at risk for recurrent ventricular tachycardia (VT) and sudden cardiac death (SCD) across Asia. Patients with nonischemic etiologies of cardiomyopathy, which are highly prevalent in Asia, have not been previously enrolled in randomized trials of VT ablation. To evaluate whether preemptive catheter ablation in patients with monomorphic VT and an indication for ICD implantation results in improved clinical outcomes compared to ICD implantation with standard medical therapy alone. To examine the natural history of ablation outcomes in the absence of background ICD therapy in patients that refuse randomization. The PAUSE-SCD study (NCT02848781) is a prospective, multi-center, randomized controlled trial enrolling patients with structural heart disease (EF

BACKGROUND Variation of atrial electromechanical delay (AED) in early phase after catheter ablation in patients with atrial fibrillation (AF) is lacking. METHODS Fifty-five consecutive patients restored sinus rhythm after ablation was included. Echocardiography was performed at 4 h, 1 day, and 3 days after radiofrequency catheter ablation, and AED was measured simultaneously by echocardiography with pulse Doppler imaging and pulse wave tissue Doppler imaging. RESULTS AED parameters were significantly longer in the nonparoxysmal atrial fibrillation (NPAF) group than in the paroxysmal atrial fibrillation (PAF) group at each checking point after ablation (P

Background and Purpose: Complete P wave disappearance (CPWD) in patients without atrial fibrillation is an uncommon clinical phenomenon. We aimed to study the relationship between CPWD and thromboembolism. Methods: Between July 2007 and December 2018, consecutive patients with CPWD on surface ECG and 24-hour Holter recording were recruited into the study from 4 centers in China. All recruited patients underwent transesophageal echocardiography or cardiac computed tomography to screen for atrial thrombus. Atrial electrical activity and scar were assessed by electrophysiological study (EPS) and 3-dimensional electroanatomic mapping. Cardiac structure and function were assessed by multimodality cardiac imaging. Results: Twenty-three consecutive patients (8 male; mean age 48.5±14.7 years) with CPWD were included. Only 3 patients demonstrated complete atrial electrical silence with atrial noncapture. Thirteen patients who had invasive atrial endocardial mapping demonstrated extensive scar. Pulse-wave mitral inflow Doppler demonstrated absent and dampened A waves in 18 and 5 patients, respectively. Pulse-wave tricuspid inflow Doppler showed absent and dampened A waves in 19 and 4 patients, respectively. Upon recruitment, 8 patients had previous stroke and 3 patients had atrial thrombus. Warfarin was prescribed to all patients. During median follow-up of 42.0 months, 2 patients developed massive ischemic stroke due to warfarin discontinuation. Conclusions: Our study suggested that CPWD reflects extensive atrial electrical silence and significantly impaired atrial mechanical function. It was strongly associated with thromboembolism and the clinical triad of CPWD-atrial paralysis-stroke was proposed. Anticoagulation should be recommended in such patients.

INTRODUCTION Atrial fibrosis is associated with atrial fibrillation (AF) recurrence after ablation. This study aims to determine the relationship between soluble ST2 (sST2), a profibrotic biomarker, and AF recurrence after radiofrequency catheter ablation (RFCA). METHODS AF patients referred for RFCA were consecutively included from October 2017 to May 2019. Baseline characteristics were collected, and sST2 levels were determined before ablation. Left atrial substrate mapping was performed after circumferential pulmonary vein isolation under sinus rhythm, and substrate was modified in low-voltage zones. A second procedure was recommended under recurrence. RESULTS Two hundred fifty-eight patients (146 males, average age 61.0 ± 8.8) were included. After a medium follow-up of 13.5 months, 52 patients (20.2%) had recurrence and received a second procedure. Preoperative sST2 level in patients with recurrence was significantly higher than that in patients without (31.3 ng/mL vs 20.3 ng/mL, P

BACKGROUND Catheter ablation strategies for nonparoxysmal atrial fibrillation (NPAF) are in varied forms. The mechanisms that circumferential pulmonary vein isolation (CPVI) alone could achieve success in some of the patients with NPAF are not well studied. This study sought to assess the clinical outcome of only CPVI approach in NPAF patients without significant left atrium scar. METHODS AND RESULTS A total of 241 consecutive patients with NPAF undergoing an initial ablation procedure were studied. After CPVI, cavotricuspid isthmus ablation and direct current cardioversion, high-density atrial voltage mapping was performed during sinus rhythm. Transitional-voltage zone (TZ) was defined as 0.4-1.3 mV, and low-voltage zone (LVZ) as

Introduction Ventricular tachycardia (VT) acceleration due to antitachycardia pacing (ATP) therapy could be often observed in patients with implantable cardioverter defibrillator (ICD), which usually results in additional shock. However, few studies focused on the risk factors for VT acceleration caused by ATP therapy. The purpose of this study was to investigate risk factors for VT acceleration due to ATP delivery. Methods We retrospectively reviewed 1056 ATP episodes in 33 patients with structural heart diseases, of whom clinical characteristics and episodes details were evaluated. Results At individual patient level, number of VT morphologies recorded in electrograms during follow‐up was a risk factor with cutoff point of 1 (AUC 0.79, sensitivity 72.7%, specificity 77.3%, P

Introduction Detailed description of longstanding persistent accelerated idioatrial rhythm (AIAR) is lacking. This observational study investigated the clinical manifestations, electrophysiological characteristics, diagnosis, treatment and prognosis of this unusual arrhythmia. Methods and results Fifteen patients (11 males; average age 25.9±15.7 years) suspected with longstanding persistent AIAR were enrolled in our study. All patients had ECG, 24-hour Holter monitoring, isoproterenol provocation test, echocardiogram, and exercise treadmill test. Electrophysiological study (EPS) and catheter ablation were performed if necessary. The above noninvasive tests would be repeated during follow-up. Among the patients, 10 were asymptomatic; 5 had concomitant paroxysmal atrial tachycardia. Two asymptomatic patients had impaired left ventricular function. AIAR was observed throughout 24-hour Holter monitoring, showing chronotropic profile similar to sinus rhythm. Such AIAR exhibited competitive property with sinus rhythm (SR) when provoked by isoproterenol or during treadmill test. Twelve patients had EPS and 8 of them had successful ablation to eliminate AIAR. During a medium follow-up of 3.7 years, all patients were in well clinical course and preserved left ventricular dysfunction, and 3 patients spontaneously reverted to SR at 10-year follow-up. Conclusions Longstanding persistent AIAR is an unusual entity of atrial arrhythmias and in most situations a benign rhythm requiring no treatment. The clinical course will be worsened when AIAR develops rapid focal firing, is associated with focal atrial tachycardias or results in tachycardia-mediated cardiomyopathy, but can be resolved via catheter ablation. This article is protected by copyright. All rights reserved

Background Right atrial tachycardia (AT) is a common arrhythmia postsurgical valve replacement in patients with rheumatic heart disease (RHD). However, the substrate and the mechanism of left AT in such patients and the ablation efficacy is less known. Methods and results Twenty-seven RHD patients with AT were enrolled in this study; nine of them (33%) had left AT. Five and four patients had left AT during the first and second procedure, respectively. A spontaneous scar in the left posterior wall was identified in all patients, and obvious anterior scar in three patients. Dual-roof-dependent AT was found in three patients and macroreentry AT surrounding right pulmonary vein was identified in one patient, two of whom had left anterior scar. Three patients had AT circuit going around the mitral annulus, one of whom had left anterior scar. Entrainment pacing at different sites confirmed the mechanism of these macroreentries. Two patients had a focal origin, one was localized in posterior wall at the edge of the scar and the other one was originated from the left septum with normal voltage. After a mean follow-up of 27.4 ± 7.9 months, the left AT group had a similar recurrence rate compared with the right AT group alone (67% vs 56%, P = 0.58). In the left AT group, 11% of patients had AT recurrence and 56% of patients developed atrial fibrillation. Conclusion Left atrial AT can occur in RHD patients postmitral valve replacement. Catheter ablation is feasible with high acute success rate. The incidence of late development atrial fibrillation is considerable after successful ablation.

Introduction Myocardium fibrosis is a hallmark of cardiomyopathy and a proposed substrate for cardiac arrhythmias. Nevertheless, fibrosis of atrial myocardium and fibrotic atrial cardiomyopathy has not been systemically addressed. Hypothesis We hypothesized that idiopathic, isolated, fibrotic atrial cardiomyopathy (IIF-ACM) is a specific cardiomyopathy, which is characterized by atrial fibrosis and related arrhythmias. Methods In the past 8 years, 34 patients (male 13, mean age 46.5±13.3 yrs) were diagnosed with IIF-ACM based on: 1) clinical evaluation; 2) cardiac image examination; and 3) electro-anatomic mapping detected atrial scarring. Serum biomarkers of collagen metabolism and cardiomyopathy-related genetic screening were performed. Tissue pathology and virus detections were done for two patients. Results During clinical evaluation, electric silent areas were detected in all patients by intra-cardiac electro-anatomical mapping. Among 34 patients, 26 presented with atrial tachycardia (AT), 5 with sick sinus syndrome (SSS) and 3 with atrial standstill. 5 AT patients further developed SSS during the correction of AT by radiofrequency ablation. Late gadolinium-enhancement cardiovascular magnet resonance showed mild to severely dilated atria, without bilateral ventricular scarring or functional impairment. Serum biomarkers of collagen screening demonstrated significant increased collagen synthesis than collagen degradation in IIF-ACM patients. Cardiomyopathy-related genetic screening depicted no clinically relevant mutation. Histological studies showed global fibrosis of atria (Fig. 1). Conclusions We systemically reported 34 patients with IIF-ACM, which is characterized by atrial scarring and relevant arrhythmias. Ventricular functions of note were preserved in all patients. However, the underlying etiology of IIF-ACM remains to be investigated.