Sana Amraoui

Driver Domains in Persistent Atrial Fibrillation

Background— Specific noninvasive signal processing was applied to identify drivers in distinct categories of persistent atrial fibrillation (AF). Methods and Results— In 103 consecutive patients with persistent AF, accurate biatrial geometry relative to an array of 252 body surface electrodes was obtained from a noncontrast computed tomography scan. The reconstructed unipolar AF electrograms acquired at bedside from multiple windows (duration, 9±1 s) were signal processed to identify the drivers (focal or reentrant activity) and their cumulative density map. The driver domains were catheter ablated by using AF termination as the procedural end point in comparison with the stepwise-ablation control group. The maps showed incessantly changing beat-to-beat wave fronts and varying spatiotemporal behavior of driver activities. Reentries were not sustained (median, 2.6 rotations lasting 449±89 ms), meandered substantially but recurred repetitively in the same region. In total, 4720 drivers were identified in 103 patients: 3802 (80.5%) reentries and 918 (19.5%) focal breakthroughs; most of them colocalized. Of these, 69% reentries and 71% foci were in the left atrium. Driver ablation alone terminated 75% and 15% of persistent and long-lasting AF, respectively. The number of targeted driver regions increased with the duration of continuous AF: 2 in patients presenting in sinus rhythm, 3 in AF lasting 1 to 3 months, 4 in AF lasting 4 to 6 months, and 6 in AF lasting longer. The termination rate sharply declined after 6 months. The mean radiofrequency delivery to AF termination was 28±17 minutes versus 65±33 minutes in the control group (P<0.0001). At 12 months, 85% patients with AF termination were free from AF, similar to the control population (87%,); P=not significant. Conclusions— Persistent AF in early months is maintained predominantly by drivers clustered in a few regions, most of them being unstable reentries.

Positron emission tomography in patients with suspected pacing system infections may play a critical role in difficult cases

BACKGROUND A pacemaker recipient may be hospitalized recurrently with an infection of unknown origin despite detailed investigations. OBJECTIVE The purpose of this study was to investigate whether (18)F-fluorodeoxyglucose positron emission tomography/computerized tomography (FDG-PET/CT) scanning has a role in identifying pacing material infection in these difficult cases. METHODS Ten patients who presented with fever of unknown origin despite detailed investigations including transesophageal echocardiography underwent FDG-PET/CT scanning. Identification of increased FDG uptake along a pacing lead prompted the removal of the entire pacing system, whereas in the absence of increased FDG uptake the pacing material was left in place. Forty control pacemaker recipients underwent FDG-PET/CT scanning as part of investigation of malignancy. RESULTS Among the 40 patients in the control group, FDG-PET/CT scanning was normal in 37 (92.5%) patients. Among the 10 patients who presented with suspected pacing system infections, FDG-PET/CT scanning showed increased FDG uptake along a lead in six patients; as a result of this finding, these patients subsequently underwent complete removal of the implanted material. Cultures of the leads were positive in all six patients, confirming involvement of the leads in the infectious process. In the other four patients, the pacing system was left in place without objective signs of active lead endocarditis during follow-up. CONCLUSION This study demonstrates the potential value of FDG-PET/CT scanning in the diagnosis of pacing lead endocarditis in difficult cases. Increased FDG uptake along a lead in this clinical context appears to be a reliable sign of active infection.

A comparison of left ventricular endocardial, multisite, and multipolar epicardial cardiac resynchronization: an acute haemodynamic and electroanatomical study

AIMS Alternative forms of cardiac resynchronization therapy (CRT), including biventricular endocardial (BV-Endo) and multisite epicardial pacing (MSP), have been developed to improve response. It is unclear which form of stimulation is optimal. We aimed to compare the acute haemodynamic response (AHR) and electrophysiological effects of BV-Endo with MSP via two separate coronary sinus (CS) leads or a single-quadripolar CS lead. METHODS AND RESULTS Fifteen patients with a previously implanted CRT system received a second temporary CS lead and left ventricular (LV) endocardial catheter. A pressure wire and non-contact mapping array were placed into the LV cavity to measure LVdP/dtmax and perform electroanatomical mapping. Conventional CRT, BV-Endo, and MSP were then performed (MSP-1 via two epicardial leads and MSP-2 via a single-quadripolar lead). The best overall AHR was found using BV-Endo pacing with a 19.6 ± 13.6% increase in AHR at the optimal endocardial site over baseline (P < 0.001). There was an increase in LVdP/dtmax with MSP-1 and MSP-2 compared with conventional CRT, but this was not statistically significant. Biventricular endocardial pacing from the optimal site was significantly superior to conventional CRT (P = 0.039). The AHR achieved when BV-Endo pacing was highly site specific. Within individuals, the best pacing modality varied and was affected by the underlying substrate. Left ventricular activation times did not predict the optimal haemodynamic configuration. CONCLUSION Biventricular endocardial pacing and not MSP was superior to conventional CRT, but was highly site specific. Within individuals, however, different methods of stimulation are optimal and may need to be tailored to the underlying substrate.

Diagnostic value of isoproterenol testing in arrhythmogenic right ventricular cardiomyopathy.

Background—Although the Task Force Criteria for arrhythmogenic right ventricular cardiomyopathy (ARVC) have recently been updated, the diagnosis remains challenging in the early stages. The aim of this study was to evaluate the diagnostic value of &bgr;-adrenergic stimulation in ARVC. Methods and Results—We evaluated 412 consecutive patients (213 men, age 41.5±16 years) referred for premature ventricular contractions evaluation or suspected ARVC. Isoproterenol testing was performed with continuous infusion of isoproterenol (45 &mgr;g/min) for 3 minutes. It was considered positive if there were either (1) polymorphic premature ventricular contractions with ≥1 couplet or (2) sustained or nonsustained ventricular tachycardia with left bundle branch block excluding right ventricular outflow tract ventricular tachycardia. ARVC was diagnosed in 35 patients at initial evaluation (23 men, aged 42±15 years). Isoproterenol testing was positive in 32 of 35 (91.4%) patients with ARVC and in 42 of 377 (11.1%) patients without ARVC (P<0.0001). Sensitivity, specificity, positive, and negative predictive values of isoproterenol testing to diagnose ARVC were 91.4%, 88.9%, 43.2%, and 99.1%, respectively. During a mean follow-up period of 5.6±4.4 years, 6 additional patients met diagnostic criteria for ARVC. Importantly, initial isoproterenol testing was positive in 6 of 6 (100%) of these patients. Survival free from ARVC diagnosis was significantly lower in the positive isoproterenol group than in the negative isoproterenol group (P<0.0001, exact log-rank test). Conclusions—Ventricular arrhythmogenicity during isoproterenol testing is highly sensitive (sensitivity, 91.4%) for the diagnosis of ARVC, particularly in its early stages.

Noninvasive Assessment of LV Contraction Patterns Using CMR to Identify Responders to CRT

OBJECTIVES Type II activation describes the U-shaped electrical activation of the left ventricle (LV) with a line of block in patients with left bundle branch block (LBBB). We sought to determine if a corresponding pattern of contraction could be identified using cardiac magnetic resonance (CMR) cine imaging and whether this predicted response to cardiac resynchronization therapy (CRT). BACKGROUND U-shaped LV electrical activation in LBBB has been shown to predict favorable response to CRT. It is not known if the degree of electromechanical coupling is such that the same is true for LV contraction patterns. METHODS A total of 52 patients (48% ischemic) scheduled for CRT implantation prospectively underwent pre-implantation CMR cine analysis using endocardial contour tracking software to generate time-volume curves and contraction propagation maps. These were analyzed to assess the contraction sequence of the LV. The effect of contraction pattern on CRT response in terms of reverse remodeling (RR) and clinical parameters (New York Heart Association functional class, 6-min walk distance and Heart Failure Questionnaire score) was assessed at 6 months. RESULTS Two types of contraction pattern were identified; homogenous spread from septum to lateral wall (type I, n = 27) and presence of block with a subsequent U-shaped contraction pattern (type II, n = 25). Rates of RR in those with a type 2 pattern were significantly greater at 6 months (80% vs. 26%, p < 0.001) as was mean increase in 6-min walk distance (126 ± 106 m vs. 55 ± 60 m; p = 0.004). CONCLUSIONS Cine CMR can identify a U-shaped pattern of contraction which predicts increased echocardiographic and clinical response rates to CRT in patients with LBBB.

Image Integration to Guide Catheter Ablation in Scar-Related Ventricular Tachycardia

Although multi‐detector computed tomography (MDCT) and cardiac magnetic resonance (CMR) can assess the structural substrate of ventricular tachycardia (VT) in ischemic cardiomyopathy (ICM), non‐ICM (NICM), and arrhythmogenic right ventricular cardiomyopathy (ARVC), the usefulness of systematic image integration during VT ablation remains undetermined.

Percolation as a mechanism to explain atrial fractionated electrograms and reentry in a fibrosis model based on imaging data

BACKGROUND Complex fractionated atrial electrograms (CFAEs) have long been associated with proarrhythmic alterations in atrial structure or electrophysiology. Structural alterations disrupt and slow smoothly propagating wavefronts, leading to wavebreaks and electrogram (EGM) fractionation, but the exact nature and characteristics for arrhythmia remain unknown. Clinically, in atrial fibrillation (AF) patients, increases in frequency, whether by pacing or fibrillation, increase EGM fractionation and duration, and reentry can occur in relation with the conduction disturbance. Recently, percolation has been proposed as an arrhythmogenic mechanism, but its role in AF has not been investigated. OBJECTIVE We sought to determine if percolation can explain reentry formation and EGM behavior observed in AF patients. METHODS Computer models of fibrotic tissue with different densities were generated based on late gadolinium-enhanced magnetic resonance images, using pixel intensity as a fibrosis probability to avoid an arbitrary binary threshold. Clinical pacing protocols were followed to induce AF, and EGMs were computed. RESULTS Reentry could be elicited, with a biphasic behavior dependent on fibrotic density. CFAEs were recorded above fibrotic regions, and consistent with clinical data, EGM duration and fractionation increased with more rapid pacing. CONCLUSION These findings confirm percolation as a potential mechanism to explain AF in humans and give new insights into dynamics underlying conduction distortions and fractionated signals in excitable media, which correlate well with the experimental findings in fibrotic regions. The greater understanding of the different patterns of conduction changes and related EGMs could lead to more individualized and effective approaches to AF ablation therapy.

History and clinical significance of early repolarization syndrome.

The early repolarization (ER) pattern has historically been regarded as a benign ECG variant. However, in recent years this view has been challenged based on multiple reports linking the ER pattern with an increased risk of sudden cardiac death. The mechanistic basis of ventricular arrhythmogenesis in ER syndrome is presently incompletely understood. Furthermore, strategies for risk stratification and therapy for ER syndrome remain suboptimal. The recent emergence of novel mapping techniques for cardiac arrhythmia has ushered a new era of research into the mechanistic basis of ER syndrome. This review provides an overview of current evidence relating to ER and risk of ventricular arrhythmias and discusses potential future areas of research to elucidate the mechanisms of ventricular arrhythmogenesis.

Contribution of PET Imaging to the Diagnosis of Septic Embolism in Patients With Pacing Lead Endocarditis.

OBJECTIVES The aim of this study was to investigate the role of 18-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) scanning in identifying septic embolism in patients with lead endocarditis. BACKGROUND Lead endocarditis may be associated with septic embolism, in which case the administration mode, type, and duration of antibiotic therapy must be adapted. However, diagnosis can be challenging: magnetic resonance imaging (MRI) cannot be performed in the vast majority of patients with cardiac implantable electronic devices (CIEDs). FDG PET/CT scanning has been proposed as a diagnostic tool for suspected CIED infection. METHODS Thirty-five consecutive patients with lead endocarditis were prospectively studied. FDG PET/CT scanning was performed and analyzed blindly by experienced nuclear medicine physicians to assess for the presence of septic embolism 2 days before lead extraction. RESULTS FDG PET/CT scanning identified septic emboli in 10 patients (29%): 7 with spondylodiscitis, 2 with septic pulmonary emboli, and 1 with an infected vascular prosthesis. Among the 7 patients with occult spondylodiscitis, 4 were asymptomatic, and 3 had back pain with negative CT imaging, MRI being contraindicated due to non MRI-compatible CIEDs. Antimicrobial therapy was adapted (double antibiotic therapy with good bone penetration) and prolonged. Among other important ancillary findings, 3 patients presented focal FDG uptake in the colon (1 adenocarcinoma, and 2 resected polyps) and 2 in the esophagus (both cases confirmed as neoplasia). CONCLUSIONS This study emphasizes the potential utility of FDG PET/CT scanning as a diagnostic tool for septic emboli in patients with pacing lead endocarditis. This promising diagnostic tool may be integrated in the diagnostic algorithm of patients with lead endocarditis because diagnosis of septic embolisms has a direct and significant impact on the therapeutic care pathway.

Role of High-Resolution Image Integration to Visualize Left Phrenic Nerve and Coronary Arteries During Epicardial Ventricular Tachycardia Ablation

Background—Epicardial ventricular tachycardia (VT) ablation is associated with risks of coronary artery (CA) and phrenic nerve (PN) injury. We investigated the role of multidetector computed tomography in visualizing CA and PN during VT ablation. Methods and Results—Ninety-five consecutive patients (86 men; age, 57±15) with VT underwent cardiac multidetector computed tomography. The PN detection rate and anatomic variability were analyzed. In 49 patients undergoing epicardial mapping, real-time multidetector computed tomographic integration was used to display CAs/PN locations in 3-dimensional mapping systems. Elimination of local abnormal ventricular activities (LAVAs) was used as ablation end point. The distribution of CAs/PN with respect to LAVA was analyzed and compared between VT etiologies. Multidetector computed tomography detected PN in 81 patients (85%). Epicardial LAVAs were observed in 44 of 49 patients (15 ischemic cardiomyopathy, 15 nonischemic cardiomyopathy, and 14 arrhythmogenic right ventricular cardiomyopathy) with a mean of 35±37 LAVA points/patient. LAVAs were located within 1 cm from CAs and PN in 35 (80%) and 18 (37%) patients, respectively. The prevalence of LAVA adjacent to CAs was higher in nonischemic cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy than in ischemic cardiomyopathy (100% versus 86% versus 53%; P<0.01). The prevalence of LAVAs adjacent to PN was higher in nonischemic cardiomyopathy than in ischemic cardiomyopathy (93% versus 27%; P<0.001). Epicardial ablation was performed in 37 patients (76%). Epicardial LAVAs could not be eliminated because of the proximity to CAs or PN in 8 patients (18%). Conclusions—The epicardial electrophysiological VT substrate is often close to CAs and PN in patients with nonischemic cardiomyopathy. High-resolution image integration is potentially useful to minimize risks of PN and CA injury during epicardial VT ablation.