Electrophysiologic testing for diagnostic evaluation and risk stratification in patients with suspected cardiac sarcoidosis with preserved left and right ventricular systolic function.

INTRODUCTION: While cardiac sarcoidosis (CS) carries a risk of ventricular arrhythmias (VAs) and sudden cardiac death (SCD), risk stratification of patients with CS and preserved left ventricular/right ventricular (LV/RV) systolic function remains challenging. We sought to evaluate the role of electrophysiologic testing and programmed electrical stimulation of the ventricle (EPS) in patients with suspected CS with preserved ventricular function. METHODS: One hundred twenty consecutive patients with biopsy-proven extracardiac sarcoidosis and preserved LV/RV systolic function underwent EPS. All patients had either probable CS defined by an abnormal cardiac positron emission tomography or cardiac magnetic resonance imaging, or possible CS with normal advanced imaging but abnormal echocardiogram (ECG), SAECG, Holter, or clinical factors. Patients were followed for 4.5 ± 2.6 years for SCD and VAs. RESULTS: Seven of 120 patients (6%) had inducible ventricular tachycardia (VT) with EPS and received an implantable cardioverter defibrillator (ICD). Three patients (43%) with positive EPS later had ICD therapies for VAs. Kaplan-Meier analysis stratified by EPS demonstrated a significant difference in freedom from VAs and SCD (P = 0.009), though this finding was driven entirely by patients within the cohort with probable CS (P = 0.018, n = 69). One patient with possible CS and negative EPS had unrecognized progression of the disease and unexplained death with evidence of CS at autopsy. CONCLUSIONS: EPS is useful in the risk stratification of patients with probable CS with preserved LV and RV function. A positive EPS was associated with VAs. While a negative EPS appeared to confer low risk, close follow-up is needed as EPS cannot predict fatal VAs related to new cardiac involvement or disease progression.

Long term follow-up after ventricular tachycardia ablation in patients with congenital heart disease.

BACKGROUND: Ventricular tachycardia (VT) is frequently encountered in patients with repaired and unrepaired congenital heart disease (CHD), causing significant morbidity and sudden cardiac death. Data regarding underlying VT mechanisms and optimal ablation strategies in these patients remain limited. OBJECTIVE: To describe the electrophysiologic mechanisms, ablation strategies, and long-term outcomes in patients with CHD undergoing VT ablation. METHODS: Forty-eight patients (mean age 41.3 ± 13.3 years, 77.1% male) with CHD underwent a total of 57 VT ablation procedures at two centers from 2000 to 2017. Electrophysiologic and follow-up data were analyzed. RESULTS: Of the 77 different VTs induced at initial or repeat ablation, the underlying mechanism in 62 (81.0%) was due to scar-related re-entry; the remaining included four His-Purkinje system-related macrore-entry VTs and focal VTs mainly originating from the outflow tract region (8 of 11, 72.7%). VT-free survival after a single procedure was 72.9% (35 of 48) at a median follow-up of 53 months. VT-free survival after multiple procedures was 85.4% (41 of 48) at a median follow-up of 52 months. There were no major complications. Three patients died during the follow-up period from nonarrhythmic causes, including heart failure and cardiac surgery complication. CONCLUSION: While scar-related re-entry is the most common VT mechanism in patients with CHD, importantly, nonscar-related VT may also be present. In experienced tertiary care centers, ablation of both scar-related and nonscar-related VT in patients with CHD is safe, feasible, and effective over long-term follow-up.

Interaction of Localized Drivers and Disorganized Activation in Persistent Atrial Fibrillation: Reconciling Putative Mechanisms Using Multiple Mapping Techniques.

BACKGROUND: Mechanisms for persistent atrial fibrillation (AF) are unclear. We hypothesized that putative AF drivers and disorganized zones may interact dynamically over short time scales. We studied this interaction over prolonged durations, focusing on regions where ablation terminates persistent AF using 2 mapping methods. METHODS: We recruited 55 patients with persistent AF in whom ablation terminated AF prior to pulmonary vein isolation from a multicenter registry. AF was mapped globally using electrograms for 360±45 cycles using (1) a published phase method and (2) a commercial activation/phase method. RESULTS: Patients were 62.2±9.7 years, 76% male. Sites of AF termination showed rotational/focal patterns by methods 1 and 2 (51/55 vs 55/55; P=0.13) in spatially conserved regions, yet fluctuated over time. Time points with no AF driver showed competing drivers elsewhere or disordered waves. Organized regions were detected for 61.6±23.9% and 70.6±20.6% of 1 minute per method (P=nonsignificant), confirmed by automatic phase tracking (P<0.05). To detect AF drivers with >90% sensitivity, 8 to 32 s of AF recordings were required depending on driver definition. CONCLUSIONS: Sites at which persistent AF terminated by ablation show organized activation that fluctuate over time, because of collision from concurrent organized zones or fibrillatory waves, yet recur in conserved spatial regions. Results were similar by 2 mapping methods. This network of competing mechanisms should be reconciled with existing disorganized or driver mechanisms for AF, to improve clinical mapping and ablation of persistent AF. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT02997254.

Perioperative electrophysiology study in patients with tetralogy of Fallot undergoing pulmonary valve replacement will identify those at high risk of subsequent ventricular tachycardia.

BACKGROUND: Ventricular tachyarrhythmias are the most common cause of death in patients with repaired tetralogy of Fallot (TOF), but predicting those at risk remains a challenge. An electrophysiology study (EPS) has been proposed to risk stratify patients with TOF. OBJECTIVE: We sought to evaluate a perioperative EPS-guided approach to risk stratify patients with TOF undergoing pulmonary valve replacement (PVR) and guide concomitant cryoablation. METHODS: A prospective cohort study of patients with TOF undergoing an EPS at the time of PVR from 2006 to 2017 was conducted at 2 centers. Patients inducible at the time of pre-PVR had undergone concomitant cryoablation in addition to PVR. A repeat post-PVR EPS was performed in those initially inducible to guide implantable cardioverter-defibrillator (ICD) implantation. RESULTS: Of 70 patients who underwent a pre-PVR EPS, 34 (49%) had inducible sustained ventricular tachycardia (VT): 25 monomorphic VT and 9 polymorphic VT. Among patients undergoing cryoablation, 14 (45%) had inducible VT and underwent ICD implantation. During a mean follow-up period of 6.1 ± 3.2 years, 3 patients (21%) had appropriate ICD shocks for symptomatic VT. There was an average of 2.3 shocks (range 1-4 shocks), and the mean time to first shock post-device implantation was 3.6 years (range 2.9-4.3 years). Among patients with negative pre- or post-PVR EPS results, 2 had VT requiring radiofrequency ablation and/or subsequent ICD implantation. There were no arrhythmic deaths. CONCLUSION: A pre-PVR EPS identified patients with higher-risk TOF undergoing PVR. Despite empirical VT cryoablation at the time of PVR, a high percentage of patients remained inducible for VT. In this high-risk cohort, post-PVR EPS evaluation is important to identify patients at risk of VT despite cryoablation.

Noninvasive predictors of perioperative atrial arrhythmias in patients with tetralogy of Fallot undergoing pulmonary valve replacement.

BACKGROUND: Patients with tetralogy of Fallot (TOF) have increased risk of atrial arrhythmias. HYPOTHESIS: A measure of atrial dispersion, the P-wave vector magnitude (Pvm), can identify patients at risk for perioperative atrial flutter (AFL) or intra-atrial re-entrant tachycardia (IART) in a large TOF cohort. METHODS: We performed a blinded, retrospective analysis of 158 TOF patients undergoing pulmonary valve replacement between 1997 and 2015. History of AFL/IART was documented using electrocardiogram, Holter monitor, exercise stress test, implanted cardiac device, and electrophysiology study. P-R intervals, Pvm, QRS duration, and QRS vector magnitude were assessed from resting sinus-rhythm 12-lead electrocardiograms and identification of those with AFL/IART was determined. RESULTS: Fourteen patients (8.9%) were found to have AFL/IART. Pvm, QRS duration, and QRS vector magnitude significantly differentiated those with AFL/IART from those without on univariate analysis: 0.09 ± 0.04 vs 0.18 ± 0.07 mV, 161.3 ± 21.9 vs 137.7 ± 31.4 ms, and 1.2 (interquartile range, 1.0-1.2) vs 1.6 mV (1.0-2.3), respectively (P < 0.05 for each). The Pvm had the highest area under the ROC curve (0.88) and was the only significant predictor on multivariate analysis, with odds ratio of 0.02 (95% confidence interval: 0.01-0.53). P-R duration, MRI volumes, and right-heart hemodynamics did not significantly differentiate those with vs those without AFL/IART. CONCLUSIONS: In TOF patients undergoing pulmonary valve replacement, Pvm has significant value in predicting those with perioperative AFL/IART. These clinical features may help further evaluate TOF patients at risk for perioperative atrial arrhythmias. Prospective studies are warranted.

Core isolation of critical arrhythmia elements for treatment of multiple scar-based ventricular tachycardias.

BACKGROUND: Radiofrequency ablation of multiple or unmappable ventricular tachycardias (VTs) remains a challenge with unclear end points. We present our experience with a new strategy isolating core elements of VT circuits. METHODS AND RESULTS: Patients with structural heart disease presenting for VT radiofrequency ablation at 2 centers were included. Strategy involved entrainment/activation mapping if VT was hemodynamically stable, and voltage mapping with electrogram analysis and pacemapping. Core isolation (CI) was performed incorporating putative isthmus and early exit site(s) based on standard criteria. If VT was noninducible, the dense scar (<0.5 mV) region was isolated. Successful CI was defined by exit block (20 mA at 2 ms) within the isolated region. VT inducibility was also assessed. Forty-four patients were included (mean age, 63; 95% male; 73% ischemic cardiomyopathy; mean left ventricular ejection fraction, 31%; 68% with multiple unstable VTs [mean, 3+2]). CI area was 11+12 versus 55+40 cm(2) total scar area. Additional substrate modification was performed in 27 (61%), and epicardial radiofrequency ablation was performed in 4 (9%) patients. CI was achieved in 37 (84%) and led to better VT-free survival (log rank P=0.013). CONCLUSIONS: CI is a novel strategy with a discrete and measurable end point beyond VT inducibility to treat patients with multiple or unmappable VTs. The CI region can be selected based on standard characterization of suspected VT isthmus surrogates thus limiting ablation target size. Exit block within the isolated area is achievable in most and may further improve long-term success.

Electrophysiologic manifestations of cardiac sarcoidosis.

PURPOSE OF REVIEW: Cardiac involvement in sarcoidosis patients is frequently unrecognized with ventricular arrhythmias and sudden cardiac death (SCD) sometimes occurring as its initial presentation. Early involvement of an electrophysiologist as part of a multidisciplinary team is essential to screening, risk stratification, and management of cardiac sarcoidosis patients. This review outlines potential manifestations of cardiac sarcoidosis, as well as diagnostic and treatment strategies. RECENT FINDINGS: Recent retrospective analyses have shown that the incidence of atrioventricular block, atrial tachyarrhythmias, and ventricular tachyarrhythmias in these patients is substantial. In addition to advanced cardiac imaging, there is a role for ECG, signal-averaged ECG, ambulatory telemetry monitoring, and electrophysiologic testing in the initial evaluation of a patient with suspected cardiac sarcoidosis. There have been recent investigations into the role of implantable cardioverter-defibrillators (ICDs) for SCD prevention with a high rate of appropriate therapies observed. Immunosuppressive therapy, antiarrhythmic drugs, and catheter ablation each also have a role in the reduction of overall arrhythmic burden. SUMMARY: The electrophysiologist's approach to a patient with cardiac sarcoidosis can aid in diagnosis, risk stratification, and management with antiarrhythmic therapy, catheter ablation, and ICD implantation for the prevention of SCD.

Percutaneous transhepatic access for catheter ablation of cardiac arrhythmias.

AIMS: Femoral venous access may be limited in certain patients undergoing electrophysiology (EP) study and ablation. The purpose of this study is to review a series of patients undergoing percutaneous transhepatic access to allow for ablation of cardiac arrhythmias. METHODS AND RESULTS: Six patients with a variety of cardiac arrhythmias and venous abnormalities underwent percutaneous transhepatic access. Under fluoroscopic and ultrasound guidance, a percutaneous needle was advanced into a hepatic vein and exchanged for a vascular sheath over a wire. Electrophysiology study and radiofrequency ablation was then performed. All tachycardias, including atrial tachycardia, atrial flutter, atrioventricular nodal tachycardia, and atrial fibrillation, were ablated. Procedural times ranged from 227 to 418 min. Fluoroscopy times ranged from 32 to 95 min. There were no complications. All six patients have been arrhythmia-free in follow-up (5-49 months, mean 23.1 months). CONCLUSION: Percutaneous transhepatic access is safe and feasible in patients with limited venous access who are undergoing EP study and ablation for a range of cardiac arrhythmias.

Typical atrial flutter in an atypical patient.

Arrhythmias in adult congenital heart disease (ACHD) pose unique procedural challenges, especially with intravascular access. We report a unique case of ablation via a left-sided hepatic vein approach in a patient with situs inversus totalis. A 28-year-old woman with situs inversus totalis, ventriculoseptal defect, and dextro-transposition of the great arteries underwent ablation for documented narrow-complex tachycardia. Because of bilateral iliac venous occlusions, the coronary sinus (CS) was accessed through the left internal jugular vein. Rapid atrial pacing resulted in a tachycardia with an atrial cycle length of 225 msec and 2:1 atrioventricular association. Entrainment from the proximal and distal CS was consistent with typical atrial flutter around the left-sided tricuspid valve. Because of the iliac vein occlusions, access for ablation was obtained via a left-sided hepatic vein (Figure 1). Resetting from the cavotricuspid isthmus and three-dimensional electroanatomic mapping (Figure 2) confirmed typical atrial flutter, which, given the dextrocardia, occurred in a clockwise fashion around the tricuspid valve. Ablation was performed at the cavotricuspid isthmus resulting in arrhythmia termination and isthmus block. This case highlights the many unusual challenges that patients with ACHD can pose to the proceduralist, including atypical cardiac anatomy and difficult intravascular access. Unusual and creative approaches are often necessary to treat these patients successfully.

Electrophysiologic study: its predictive value for ventricular arrhythmias.

Studies have shown the predictive value of inducible ventricular tachycardia and clinical arrhythmia in patients who have structural heart disease. We examined the possible predictive value of electrophysiologic study before the placement of an implantable cardioverter-defibrillator. Our retrospective study group comprised 315 patients who had ventricular tachycardia that was inducible during electrophysiologic study and who had undergone at least 1 month of follow-up (247 men; mean age, 66.9 +/- 13.5 yr; mean follow-up, 24.9 +/- 14.8 mo). Recorded characteristics included induced ventricular tachycardia cycle length, atrio-His and His-ventricular electrograms, PR and QT intervals, QRS duration, and drug therapy. Of the 315 patients, 97 experienced ventricular arrhythmia during the follow-up period, as registered by 184 of more than 400 interrogations. There were 187 episodes of ventricular arrhythmia (tachycardia, 178; fibrillation, 9) during 652.5 person-years of follow-up. Subjects with a cycle length > or =240 msec were more likely to have an earlier 1st arrhythmia than those with a cycle length <240 msec (P=0.032). A quarter of the subjects with a cycle length > or =240 msec had their 1st arrhythmia by 19.14 months, compared with 23.8 months for a quarter of the subjects with a cycle length <240 msec (P <0.032). Among the electrophysiologic characteristics examined, inducible ventricular tachycardia with a cycle length > or =240 msec is predictive of appropriate implantable cardioverter-defibrillator therapy at an earlier time. This may have prognostic implications that warrant implantable cardioverter-defibrillator programming to enable appropriate antitachycardia pacing in this group of patients.

Implantable cardioverter-defibrillator shocks in patients with a left ventricular assist device.

BACKGROUND: Left ventricular assist device (LVAD) use is becoming increasingly common for patients with end-stage heart failure. However, the rate of implantable cardioverter-defibrillator (ICD) shocks and the effect of these shocks on outcomes in patients with LVADs remain unknown. METHODS: Medical records were reviewed from patients with both an ICD and a LVAD from September 2000 to February 2009. The association between ICD shocks and survival while receiving device support was assessed using Cox proportional hazards modeling. RESULTS: Thirty-three of 61 patients with a LVAD also had an ICD and form the basis of this report. The mean duration of LVAD support was 238 days. One or more ICD shocks were delivered to 14 patients (42%) with 8 (24%) receiving appropriate shocks for ventricular arrhythmias and 6 (18%) receiving inappropriate shocks. No patients received both appropriate and inappropriate shocks. When compared with receiving no ICD shock, receiving any ICD shock or an appropriate ICD shock were both associated with an increase in the risk of death (hazard ratio [HR] 4.5, 95% confidence interval [CI] 1.2 to 17.3, p = 0.027, and HR 5.3, 95% CI 1.3 to 22.6, p = 0.023, respectively); receipt of an inappropriate shock showed a non-significant trend for an increased risk of death (HR 3.2, 95% CI 0.7 to 16.1, p = 0.151). CONCLUSIONS: ICD shocks are common after implantation of LVADs, with nearly equal numbers of appropriate and inappropriate shocks. ICD shocks are associated with higher mortality. Larger studies are needed for assessing the independent relationship of ICDs to a variety of clinical outcomes in patients with LVADs.

Incidence and predictors of mortality following ablation of ventricular tachycardia in patients with an implantable cardioverter-defibrillator.

BACKGROUND: Long-term outcomes following ablation of ventricular tachycardia (VT) have not been well described. OBJECTIVE: The purpose of this study was to identify the incidence and predictors of mortality following catheter ablation of VT in patients with an implantable cardioverter-defibrillator (ICD). METHODS: The cohort included in the analysis consisted of patients with ischemic or nonischemic cardiomyopathy undergoing electrophysiologic study and ablation of VT. Catheter ablation of VT involved the use of pacemapping, entrainment mapping (when possible), and substrate modification. Clinical recurrences, ICD therapy history, and mortality were recorded for all patients included in the cohort. Comparisons were made between those subjects who died over a 3-year follow-up period and those who survived. RESULTS: A total of 208 subjects underwent 327 VT ablations over the course of the study period. Sixty-seven deaths (75% of all deaths and 32% of the cohort) occurred within 3 years after VT ablation. After multivariable adjustment, clinical predictors of mortality included age, lower left ventricular ejection fraction, and presence of renal insufficiency. Procedural variables associated with reduced mortality following VT ablation included presence of hemodynamically tolerated VT, lack of inducibilty of any VT following ablation, and procedural date in the latter part of the study. CONCLUSION: The survival rate after VT ablation has improved over time and may reflect improved mapping and ablation techniques, in addition to improved therapies for treatment of congestive heart failure. Tolerated VT and lack of inducible ventricular arrhythmias following VT ablation was associated with improved survival in this study, suggesting their value as a risk factor for subsequent mortality.

Arrhythmogenic potential of pulmonary venous tissue: triggers for atrial fibrillation identified within the remnant of a vein.

BACKGROUND: Pulmonary veins (PVs) have frequently been identified as triggers for atrial fibrillation (AF), and higher arrhythmogenic potential of superior PVs has been attributed to their larger size, which can more rigorously support abnormalities of impulse formation and/or conduction. CASE REPORT: Contrary to this belief, we report our observations in a 63-year-old patient with history of lung cancer, S/P left upper lobectomy, undergoing ablation for paroxysmal AF. Circular mapping (Lasso) and ablation (ABL; 8-mm) catheters were deployed in left atrium (LA). Intracardiac ultrasound revealed separate right superior (RS) and inferior (RI) PVs and a single left PV. Segmented LA anatomy from the CT angiogram images corroborated this, although on the latter there appeared to be a "stump" at superior aspect of the left PV. This stump likely was the remnant of the left superior (LS) PV. Thus, the patent left vein was likely the dilated left inferior (LI) PV. With the Lasso and ABL deployed at the LIPV ostium and LSPV remnant, respectively, AF was reproducibly seen to initiate with earliest activity in the latter. Single radio-frequency ablation (RFA) lesion within the LSPV remnant abolished AF triggers. Additional RFA was done to isolate LI, RS, and RI PVs. Over a follow-up period of 24 months, this patient has remained free from AF off any drugs. CONCLUSIONS: Our observations suggest that even very proximal remnants of PVs can serve as triggers for AF. Recognition of this phenomenon was facilitated by the use of advanced imaging technique and the deployment of multiple catheters.

Covering sleeves can shield the high-voltage coils from lead chatter in an integrated bipolar ICD lead.

AIMS: Integrated bipolar implantable cardioverter-defibrillator (ICD) leads use the distal high-voltage coil as both the ventricular sensing anode and the distal shocking electrode. Mechanical interactions between the distal ICD coil and other intracardiac leads have been reported to result in electrical oversensing and inappropriate ICD therapies. We sought to determine whether covering sleeves over the high-voltage coils of an integrated bipolar ICD lead could prevent sensed artefact from mechanical lead interactions. METHODS AND RESULTS: Endotak Reliance 0157 and Endotak Reliance-G 0185 leads, the latter with expanded polytetrafluoroethylene (ePTFE) sleeves covering the high-voltage coils, were connected to ICD generators and the leads were submerged in saline. Device programmers were used to communicate with the ICD generators, providing real-time electrogram recording throughout testing. A series of mechanical interactions were performed with the ICD leads, including sliding and striking each distal coil against metal and non-metal components of other ICD and pacemaker leads. All direct metal-metal interactions resulted in sensed electrical artefact, including interactions between the bare ICD coil and another bare ICD coil or metal pacemaker ring. Identical mechanical interactions where metal-metal contact was prevented due to an interposed ePTFE covering sleeve were electrically silent with no sensed artefact. CONCLUSIONS: A covering sleeve over the distal high-voltage coil of an integrated bipolar ICD lead can mechanically shield the lead from metal-metal interactions, which might otherwise result in sensed artefact and inappropriate ICD therapies or withholding of pacing output. This finding has implications for lead selection when a new ICD lead is to be implanted adjacent to abandoned intracardiac leads or lead fragments.