Author + information
- Received August 4, 2008
- Revision received October 24, 2008
- Accepted November 16, 2008
- Published online February 24, 2009.
- Maurizio Pieroni, MD, PhD⁎ (, )
- Antonio Dello Russo, MD, PhD,
- Francesca Marzo, MD,
- Gemma Pelargonio, MD, PhD,
- Michela Casella, MD, PhD,
- Fulvio Bellocci, MD and
- Filippo Crea, MD, FACC
- ↵⁎Reprint requests and correspondence:
Dr. Maurizio Pieroni, Cardiology Department, Catholic University, Largo A. Gemelli 8, Rome 00168, Italy
Objectives We evaluated the diagnostic contribution and the therapeutic and prognostic implications of 3-dimensional electroanatomic mapping (EAM)-guided endomyocardial biopsy (EMB) in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC).
Background ARVC is a frequent cause of life-threatening ventricular arrhythmias and sudden death in young people. The value of current diagnostic criteria and the role of imaging techniques and EMB are still debated.
Methods We studied 30 consecutive patients (17 male, mean age 43 ± 17 years) with a noninvasive diagnosis of ARVC according to current criteria. All patients underwent 3-dimensional EAM-guided EMB.
Results Twenty-nine (97%) of 30 patients presented an abnormal voltage map. Histology and immunohistochemistry confirmed the diagnosis of ARVC in 15 patients, and showed active myocarditis according to Dallas criteria in the remaining 15 patients. Patients with ARVC were not distinguishable on the basis of clinical features, presence, and severity of structural and functional right ventricular abnormalities and 3-dimensional EAM findings. On the basis of clinical and histological features, a cardioverter-defibrillator was implanted in 13 patients with biopsy-proven ARVC and in 1 patient only with myocarditis. At a mean follow-up of 21 ± 8 months, 7 (47%) patients with ARVC experienced a recurrence of symptomatic sustained ventricular arrhythmias with appropriate defibrillator intervention in all cases. All patients with myocarditis remained asymptomatic and free from arrhythmic events.
Conclusions Right ventricular myocarditis frequently mimics ARVC. Three-dimensional EAM-guided EMB is a safe and effective tool in differential diagnosis and in the selection of the most appropriate therapeutic strategy.
- arrhythmogenic right ventricular cardiomyopathy
- 3-dimensional electroanatomic mapping-guided endomyocardial biopsy
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a heart muscle disease characterized by atrophy and fibrofatty replacement of right ventricle (RV) myocardium, leading to morphofunctional abnormalities and electrical instability of the RV (1,2). The disease is a frequent cause of life-threatening ventricular arrhythmias in young persons, and concealed forms may underlie sudden death in persons with an apparently normal heart, including athletes (3,4). Its prevalence has been estimated to vary from 1:2,500 to 1:5,000. ARVC is familial in almost one-third of cases, and genetic studies have recently identified causative mutations in genes encoding proteins of the desmosomal cell junction (5,6). Unfortunately, the limited number of genes thus far identified and the large genetic heterogeneity make molecular diagnosis not yet feasible. Clinical diagnosis is currently made on the basis of established criteria (7) but their value, mostly when dealing with nonfamilial cases, is increasingly questioned (8,9). Notably, myocarditis may selectively affect the RV, mimicking the typical electrocardiographic features and causing ventricular arrhythmias and morphofunctional abnormalities detectable by imaging techniques (10–12). Cardiac magnetic resonance has been proposed as an accurate tool to distinguish fat from myocardial tissue and identify localized RV wall motion abnormalities, but significant limitations and a high degree of interobserver variability mostly in the detection of RV free wall thinning and fibrofatty replacement have recently been reported (13).
Thus, histological demonstration of fibrofatty substitution of RV myocardium by endomyocardial biopsy (EMB) remains the gold standard for clinical diagnosis. Yet, extensive application of EMB has been limited by the low sensitivity of biopsies usually obtained from the interventricular septum, not frequently involved by the disease. Recently, 3-dimensional electroanatomic voltage mapping (EAM) has been demonstrated to accurately identify and locate low-voltage regions corresponding to areas of fibrofatty replacement (9), thus representing a potential guide for the execution of biopsies.
In the present study, we assessed the diagnostic utility of EAM-guided endomyocardial biopsy in consecutive patients with a clinical noninvasive diagnosis of ARVC, and evaluated the impact of this approach on the definition of treatment and prognosis.
Patient population and noninvasive studies
We studied 30 consecutive patients (17 male, mean age 43 ± 17 years) admitted to our institution from January to December 2006, with a diagnosis of ARVC on the basis of noninvasive evaluation, including 12-lead electrocardiogram, 24-h Holter monitoring, signal-averaged electrocardiogram, 2-dimensional echocardiography, and contrast-enhanced cardiac magnetic resonance. The latter was not performed in 4 patients because of claustrophobia.
The disease was considered familial in the presence of other family members with autopsy or biopsy-proven disease or premature (<40 years) sudden death at pedigree analysis.
After noninvasive study, all patients fulfilled current criteria for diagnosis of ARVC defined by the European Society of Cardiology and International Society and Federation of Cardiology Task Force (7).
The invasive study was approved by the Institutional Review Board, and all patients gave their written informed consent. All patients underwent coronary and left and right ventricular angiography (right and left anterior oblique views), 3-dimensional EAM, EMB, and programmed ventricular stimulation.
In particular, RV angiography, representing the gold standard for the detection of wall motion abnormalities and aneurysms, was performed before EAM to provide the RV silhouette in 2 views, thus improving the anatomical accuracy of EAM. On the basis of EAM, EMBs were drawn from areas presenting electrical abnormalities, as detailed in the following text.
All patients underwent RV 3-dimensional EAM technique by the CARTO system (Biosense-Webster, Diamond Bar, California), as previously described (14). Briefly, mapping points were sampled with a 7F 4-mm tip Navi-Star catheter (Biosense-Webster) to generate an accurate 3-dimensional EAM, reflecting the shape evidenced by angiography. High-density mapping was obtained in sinus rhythm (reference channel: QRS complex) by sampling at least 100 points in each chamber, uniformly distributed. The voltage maps were edited setting the point density (fill threshold) at 15 mm and manually eliminating intracavitary points, as reported (9,14). According to previous studies, “electroanatomic scar” was defined as an area including at least 3 adjacent points with a bipolar signal amplitude <0.5 mV; the reference value for normal endocardium was set at 1.5 mV (9,14). The color display to identify normal and abnormal voltage myocardium ranged from red (electroanatomic scar tissue; amplitude <0.5 mV), to purple (electroanatomic normal tissue; amplitude ≥1.5 mV). Intermediate colors represented the electroanatomic border zone (amplitude >0.5 and <1.5 mV). Adequate catheter contact was confirmed by concordant catheter tip motion with the cardiac silhouettes on fluoroscopy and by adherence of the voltage map to angiographic RV shape. To avoid low voltage recordings due to poor contact, the following tools were used: 1) the signal had to satisfy 3 stability criteria automatically detected by the CARTO system in terms of cycle length, local activation time, and beat-to-beat difference of the location of the catheter (<2%, <3 ms, and <4 mm, respectively); 2) both bipolar and unipolar signals were simultaneously acquired to confirm true catheter contact through the analysis of local electrogram (in particular the shape of the unipolar electrogram); and 3) in the presence of a low voltage area, at least 3 additional points were acquired in the same site to confirm the reproducibility of the voltage measurement.
The anatomical distribution of the pathological areas was evaluated by dividing the RV voltage map into 5 segments: outflow tract, free (anterolateral) wall, inferior and posterior basal segments, apex, and interventricular septum.
Right ventricular EMB (4 to 5 samples from each patient) were obtained through the femoral vein with the use of a pre-formed long sheath and a disposable Bioptome (Cordis, Johnson & Johnson, Miami, Florida). Once EAM was completed, the mapping catheter's tip was directed against abnormal voltage areas, and the distal end of the sheath was placed close to it. Sheath position was checked in right and left anterior oblique views (Fig. 1),and then biopsies were withdrawn from wall segments with abnormal voltage. In case of normal EAM, EMB were withdrawn from conventional sites including apex and interventricular septum.
In 2 patients with abnormal voltage areas mainly involving the basal posterior wall, the Bioptome was introduced through a steerable introducer (Agilis NxT, St. Jude Medical, Minnetonka, Minnesota) to reach that segment.
Programmed Ventricular Stimulation
All subjects underwent electrophysiological study with stimulation in the apex and the outflow tract of the RV at 2 drives (600 and 400 ms) and up to 3 extrastimuli by decreasing the coupling interval until inducing sustained ventricular arrhythmias, reaching chamber refractoriness, or a minimal coupling interval of 200 ms. The stimulation protocol was interrupted if ventricular fibrillation or sustained (>30 s) or syncopal polymorphic ventricular tachycardia were induced.
Histology and immunohistochemistry
Two to 3 samples were processed for histology and immunohistochemistry. For histology, multiple 5-μm-thick sections were cut and stained with hematoxylin-eosin, Miller's elastic Van Gieson, and Masson's trichrome, and examined by light microscopy. Immunohistochemistry for the characterization of inflammatory infiltrates was performed using the following antibodies: CD3, CD8, CD45RO, CD68 (Dako Corporation, Glostrup, Denmark), as previously described (10–12). To quantify the inflammatory infiltrates, CD8+ and CD45RO+ positive lymphocytes were counted per high-power field (400-fold magnification) in all available fields, and the mean number was calculated, as previously described (10–12).
In patients presenting histological evidence of fibrofatty replacement, a histomorphometric analysis was performed on Masson's trichrome-stained sections to calculate the extent of myocardial atrophy and fibrofatty replacement. Images obtained at ×5 magnification with a digital camera (Leica DFC 420C, Leica Microsystems, Wetzlar, Germany) were stored as TIFF files and analyzed with a dedicated imaging software (Leica Application Suite version 3.0, Leica Microsystems) to calculate the percent area occupied by adipose tissue, replacement fibrosis, and residual myocardium.
The diagnosis of myocarditis was based on Dallas criteria and immunohistochemistry (15); in particular, a T-lymphocyte infiltration (>7/mm2) in the presence of cytotoxic (CD8+) and activated (CD45RO+) lymphocytes was considered diagnostic (16). The diagnosis of ARVC was made on the basis of extensive fibrofatty myocardial atrophy with a percentage of fat >3% and fibrous tissue >40% associated with amounts of residual myocytes <45% of the specimen at morphometric analysis (17).
Molecular biology studies
Two frozen myocardial specimens per patient were used to detect the presence of cardiotropic viruses by polymerase chain reaction, as previously described (10,12).
Continuous variables are expressed as mean ± SD. Categorical differences between groups were evaluated by the 2-tailed Fisher exact text. Differences between group means were compared by the unpaired ttest. All probability values reported are 2 sided, and a probability value <0.05 was considered statistically significant. Survival free of life-threatening ventricular arrhythmias was analyzed by the Kaplan-Meier method, and comparison between groups performed by the log-rank test. Statistical analysis was performed with the SPSS version 13.0 software package (SPSS Inc., Chicago, Illinois).
Clinical characteristics and instrumental findings of the patients are summarized in Tables 1 and 2.⇓Before tissue characterization was obtained, all patients fulfilled current diagnostic criteria, and all but 1 presented at least 1 major criterion. A family history was documented in 4 patients, and clinical symptoms were present in 20, including 1 subject resuscitated from cardiac arrest. The time interval from onset of symptoms to the invasive study ranged from 1 to 36 months (mean 19 ± 31 months).
Ventricular arrhythmias with left bundle branch block morphology were documented in all patients, including sustained monomorphic ventricular tachycardia in 9, nonsustained ventricular tachycardia in 12, and frequent premature ventricular beats in 9. Arrhythmias were symptomatic in 12 patients with ARVC and in 8 patients with myocarditis; in asymptomatic patients, ventricular arrhythmias were documented at Holter monitoring performed after detection of frequent ventricular ectopic beats at resting electrocardiogram. At the time of the invasive study, antiarrhythmic therapy included sotalol in 4 patients and beta-blockers in 15 patients.
All patients presented structural and functional RV abnormalities at echocardiography, cardiac magnetic resonance imaging, and/or angiography. In particular, wall motion abnormalities were present in 26 subjects, with microaneurysms in 7 subjects. Cardiac magnetic resonance showed areas of RV delayed enhancement in 13 of 26 patients, evidence of RV fatty replacement in 10 of 26 patients, and LV delayed enhancement in 8 of 26 patients (Table 2).
EAM and programmed ventricular stimulation
The mean number of sites sampled in RV EAM was 155 ± 36. Twenty-nine (97%) of 30 patients had an abnormal voltage map. All patients had >1 area (mean 2.4 ± 1.0) with contiguous bipolar electrograms with voltage values <0.5 mV (scar tissue) surrounded by a larger zone with signal amplitudes between 0.5 and 1.5 mV indicating abnormal myocardium.
Right ventricular outflow tract and anterior free wall were the most frequently involved segments, whereas interventricular septum presented abnormal voltages in 1 patient only. Abnormal voltage areas were focal in 12 patients with main involvement of the outflow tract and inferior and posterior wall, and the remaining patients had widespread RV involvement usually associated with dilation and contractile impairment. Interestingly, wall motion abnormalities corresponded in all cases to abnormal voltage areas.
Programmed ventricular stimulation induced sustained monomorphic ventricular tachycardia in 9 patients and ventricular fibrillation in 3 patients.
In 15 patients the presence of myocardial atrophy and fibrofatty replacement confirmed the diagnosis of ARVC. In the remaining 15 cases, histology showed the presence of inflammatory infiltrates associated with necrosis of adjacent myocytes, consistent with the diagnosis of active myocarditis according to Dallas criteria. In all cases, immunohistochemistry showed inflammatory infiltrates to be mainly represented by activated and cytotoxic T lymphocytes. No patients showed histological features of sarcoidosis, granulomatous, and/or giant cell myocarditis. In patients with myocarditis, none of the samples examined presented areas of fatty replacement; moreover, no inflammatory infiltrates were observed in association with fibrofatty replacement in ARVC patients. Molecular biology studies demonstrated the presence of viral genome in 5 patients with myocarditis (parvovirus B19 in 3 cases, influenza virus in 2 cases) and in none with ARVC (p = 0.04).
Safety of EAM-guided endomyocardial biopsy
In all patients, EMB was performed by the same operator (M.P.). No major complications, including cardiac tamponade or perforation, were observed. Echocardiography performed immediately and 24 h after the procedure failed to show pericardial effusion in all cases, including 1 patient having chest pain after EMB. No complications at the site of femoral access, no sustained ventricular arrhythmias, atrial fibrillation, or development of atrioventricular or complete right bundle branch block during the execution of EAM and EMB were documented.
Comparison between ARVC and myocarditis group
The comparison between patients with biopsy-proven ARVC and patients with histological evidence of myocarditis failed to detect any difference in terms of clinical presentation, electrocardiography, arrhythmic profile, and imaging studies. A higher prevalence of family history of sudden death, although statistically not significant, was observed in the ARVC group as expected. Structural and functional abnormalities of the RV, detected either at angiography or cardiac magnetic resonance, were similar in the 2 groups, including the presence of RV delayed enhancement, whereas evidence of RV fatty infiltration was more frequent in ARVC patients (Tables 1 and 2). Similarly, the presence of abnormal voltage areas at 3-dimensional EAM as well as the induction of arrhythmias during programmed ventricular stimulation were not able to distinguish the 2 myocardial disorders (Figs. 2 and 3).⇓⇓The patients showing a normal map and the patients showing involvement of the interventricular septum were both affected by focal myocarditis.
Treatment and follow-up
On the basis of clinical features and pathological findings, 13 patients with biopsy-proven ARVC received an implantable cardioverter-defibrillator (ICD). Two patients refused ICD implantation and were treated with antiarrhythmic drugs including amiodarone and beta-blockers. Among patients with myocarditis, 1 patient presenting with syncope and inducible ventricular tachycardia received an ICD, and the remaining patients were all treated by beta-blockers.
At a mean follow-up of 21 ± 8 months (range 18 to 26 months), 7 (47%) patients with ARVC experienced recurrence of symptomatic sustained ventricular arrhythmias, in all cases interrupted by appropriate ICD interventions (direct current shocks in 4 cases, pacing in 3). All patients with myocarditis remained asymptomatic and free from arrhythmic events, and no shocks were documented in the patient with the ICD (Fig. 4).Two-dimensional echocardiography failed to show progression of the disease in terms of right and left ventricular dimensions and function in both groups.
Arrhythmogenic right ventricular cardiomyopathy is a leading cause of ventricular arrhythmias and sudden death in the young (3,4), and its recognition has relevant therapeutic and prognostic implications both for patients and for their families. In spite of a better comprehension of molecular and genetic mechanisms underlying this cardiomyopathy, and of the improvement in imaging techniques, its noninvasive diagnosis still remains difficult and represents a major clinical challenge for physicians.
In the present study, we demonstrate that in one-half of patients with a noninvasive diagnosis of ARVC according to current guidelines, EAM-guided EMB allowed the diagnosis of active myocarditis in the absence of fibrofatty replacement, with a profound impact on patient management and prognosis. Adopting this novel diagnostic technique, for the first time EMB was obtained from selected regions of the RV wall characterized by abnormal voltages at EAM, significantly modifying the initial diagnosis. No major complications, including cardiac perforation, occurred in our patients although biopsies were drawn from nonconventional sites including RV outflow tract and free wall. These findings show that RV myocarditis may mimic ARVC in a high percentage of patients and that noninvasive diagnostic techniques do not reliably allow differential diagnosis, mostly in sporadic cases.
Comparison with previous studies
Endomyocardial biopsy and autopsy findings have clearly demonstrated that myocarditis is a frequent cause of ventricular arrhythmias in persons with apparently normal heart or minimal electrocardiographic and cardiac structural abnormalities (12,18–20). Myocarditis may selectively affect the RV causing structural abnormalities, including microaneurysms (9–12), and arrhythmic manifestations typical of ARVC (9,11,21). In fact, myocardial inflammatory infiltrates associated with myocyte necrosis and replacement fibrosis may lead to functional and structural changes of RV myocardium resembling those produced by fibrofatty replacement, and representing the substrate of the abnormal voltage map and ventricular arrhythmias. In this regard, it has been recently reported that RV sarcoidosis may mimic EAM and arrhythmic features of ARVC (22).
At variance with a previous study (12), in our series EAM failed to distinguish ARVC from myocarditis, as we observed abnormal voltage areas in patients with myocarditis as well. This discrepancy is probably due to the shorter interval from the onset of arrhythmias to EMB in our study, reducing the possibility of nonspecific histological findings associated with a spontaneous resolution of the inflammatory process. In addition, EAM guidance, allowing us to obtain myocardial samples from affected areas, reduced the sampling error of EMB. In fact, myocarditis, as well as ARVC, is frequently a focal disorder and can be missed at biopsy, particularly when a limited number of EMBs is drawn from the same conventional site. Noteworthy in a previous study, EMBs obtained by a traditional approach were nondiagnostic in 25% of patients with abnormal EAM (9). These data suggest a significant increase of EMB sensitivity under EAM guidance.
Moreover, the evidence of normal EAM in patients with histological evidence of focal inflammatory cardiomyopathy reported by Corrado et al. (9) supports the notion that, in patients with myocarditis, voltage abnormalities as well as ventricular arrhythmias are mostly related to the persistence of myocardial inflammation rather than to scar tissue.
Clinical and therapeutic implications
The differential diagnosis between RV myocarditis and ARVC has relevant clinical implications regarding the management of arrhythmias and the prevention of sudden death. Current treatment strategies suggest the implantation of an ICD in most symptomatic patients with ARVC and even in asymptomatic patients presenting risk factors such as family history and severe right ventricular involvement or positive programmed ventricular stimulation. Conversely, no guidelines concerning the treatment of life-threatening ventricular arrhythmias in the context of active myocarditis are currently available. Several studies suggest that, in these patients, ventricular arrhythmias are associated with the persistence of the inflammatory process, are generally self-limited, and exhibit a benign course (9–12) usually not requiring major therapeutic strategies including defibrillator implantation. Accordingly, in the present study, an ICD was implanted in 13 of 15 patients with a histological diagnosis of ARVC, but only 1 patient with myocarditis received a defibrillator because of syncope and inducible ventricular tachycardia. Recurrent symptomatic sustained ventricular arrhythmias with appropriate defibrillator therapy were documented in 7 patients with ARVC. In contrast, the outcome of patients with myocarditis was excellent, thus confirming the benign prognosis of ventricular arrhythmias in this subset of patients. These findings, although obtained in a small selected population with midterm follow-up, suggest that the identification of the underlying myocardial disease may represent adjunctive useful information to define the therapeutic approach to young persons with life-threatening ventricular arrhythmias and may warrant the execution of a complete invasive study.
It is needless to emphasize that inappropriate ICD implantation, beside costs, may have a devastating effect on life-style, in particular for young patients, due to the risk of inappropriate shocks and infection related to multiple device substitution. Of note, in a recent study, patients with the Brugada syndrome showed a rate of inappropriate shocks far exceeding the appropriate ICD interventions (23), with youngest age representing a risk factor for inappropriate activation due to sinus tachycardia and over-sensing of muscular activity.
Although dealing with a rare condition, the relatively small sample size of study population and the short duration of the follow-up may represent limitations of the present study. In addition, as our institution is a tertiary center for the study of cardiomyopathies, many patients with clinical suspicion of ARVC were sent from other hospitals, and a possible referral bias may have influenced the features of study population and the time of enrollment. Genetic studies for known desmosomal gene mutations were not performed as they are not necessary for the diagnosis of ARVC. Further studies comparing electroanatomical, histological, and genetic features in larger populations could clarify other aspects of the pathogenesis of ARVC. With regard to the safety of the invasive procedure, we must acknowledge that the high experience level of the cardiologist performing the biopsies could have minimized the risks related to this new approach, which should, therefore, be considered in referral centers with experience on endomyocardial biopsy.
Our results, together with those of other recent studies (9,11), confirm the limitations of current guidelines for the diagnosis of ARVC and suggest the need for the definition of new criteria taking into account the potential contribution of 3-dimensional EAM-guided EMB and possibly of genetic testing (24). Currently available imaging techniques, including cardiac magnetic resonance, are crucial to recognize RV wall motion abnormalities but they appear still unreliable for detecting fibrofatty replacement, mostly in nonadvanced disease (13). Notably, a recent statement from the American Heart Association, American College of Cardiology, and European Society of Cardiology recommends that EMB may be considered in the setting of suspected ARVC, although its role is still considered controversial owing to the potential risks and possible sampling error (25). Our results demonstrate that 3-dimensional EAM-guided EMB is a safe and effective diagnostic technique for differential diagnosis in patients with noninvasive evidence of ARVC, and has a profound impact on patient management.
The authors wish to thank engineer Lidia Visigalli (Biosense Webster, Italy), and Fabio Bonelli and Manlio Fabbrucci (Cardiology Department, Catholic University) for their expert technical support.
Drs. Pieroni and Dello Russo contributed equally to this work.
- Abbreviations and Acronyms
- arrhythmogenic right ventricular cardiomyopathy
- electroanatomic mapping/map
- endomyocardial biopsy
- implantable cardioverter-defibrillator
- right ventricle
- Received August 4, 2008.
- Revision received October 24, 2008.
- Accepted November 16, 2008.
- American College of Cardiology Foundation
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