Machine learning based detection of T-wave alternans in real ambulatory conditions

BACKGROUND AND OBJECTIVE

T-wave alternans (TWA) is a fluctuation in the repolarization morphology of the ECG. It is associated with cardiac instability and sudden cardiac death risk. Diverse methods have been proposed for TWA analysis. However, TWA detection in ambulatory settings remains a challenge due to the absence of standardized evaluation metrics and detection thresholds.

METHODS

In this work we use traditional TWA analysis signal processing-based methods for feature extraction, and two machine learning (ML) methods, namely, K-nearest-neighbor (KNN) and random forest (RF), for TWA detection, addressing hyper-parameter tuning and feature selection. The final goal is the detection in ambulatory recordings of short, non-sustained and sparse TWA events.

RESULTS

We train ML methods to detect a wide variety of alternant voltage from 20 to 100 μV, i.e., ranging from non-visible micro-alternans to TWA of higher amplitudes, to recognize a wide range in concordance to risk stratification. In classification, RF outperforms significantly the recall in comparison with the signal processing methods, at the expense of a small lost in precision. Despite ambulatory detection stands for an imbalanced category context, the trained ML systems always outperform signal processing methods.

CONCLUSIONS

We propose a comprehensive integration of multiple variables inspired by TWA signal processing methods to fed learning-based methods. ML models consistently outperform the best signal processing methods, yielding superior recall scores.

Subjective identification and ablation of drivers improves rhythm control in patients with persistent atrial fibrillation. The CHAOS-AF study

INTRODUCTION AND OBJECTIVES

The optimal approach for persistent atrial fibrillation (AF) ablation remains unknown. In patients with persistent AF, we compared an ablation strategy based on pulmonary vein isolation (PVI) plus ablation of drivers (PVI+D), with a conventional PVI-only approach performed in a 1:1 propensity score-matched cohort.

METHODS

Drivers were subjectively identified using conventional high-density mapping catheters (IntellaMap ORION, PentaRay NAV or Advisor HD Grid), without dedicated software, as fractionated continuous or quasicontinuous electrograms on 1 to 2 adjacent bipoles, which were ablated first; and as sites with spatiotemporal dispersion (the entire cycle length comprised within the mapping catheter) plus noncontinuous fractionation, which were only targeted in patients without fractionated continuous electrograms, or without AF conversion after ablation of fractionated continuous electrograms. Ablation included PVI plus focal or linear ablation targeting drivers.

RESULTS

A total of 50 patients were included in each group (61±10 years, 25% women). Fractionated continuous electrograms were found and ablated in 21 patients from the PVI+D group (42%), leading to AF conversion in 7 patients. In the remaining 43 patients, 143 sites with spatiotemporal dispersion plus noncontinuous fractionation were targeted. Globally, AF conversion was achieved in 21 patients (42%). The PVI+D group showed lower atrial arrhythmia recurrences at 1 year of follow-up (30.6% vs 48%; P=.048) and at the last follow-up (46% vs 72%; P=.013), and less progression to permanent AF (10% vs 40%; P=.001).

CONCLUSIONS

Subjective identification and ablation of drivers, added to PVI, increased 1-year freedom from atrial arrhythmia and decreased long-term recurrences and progression to permanent AF.

Case Series of Ventricular Tachycardia Ablation With Pulsed-Field Ablation: Pushing Technology Further (Into the Ventricle)

Three cases of ventricular tachycardia ablation with pulsed-field ablation technology performed at 2 separate centers are reported, highlighting the advantages and disadvantages of this tool inside the ventricle: its dependence on proximity rather than contact makes it useful in sites with poor stability, while the speed of application and large scope of action provided by commercially available catheters could help with ablating large diseased areas of endocardium in a fast and hemodynamically well-tolerated fashion. However, lesion depth could be insufficient for guaranteeing efficacy in preventing ventricular tachycardias originating at an epicardial site, even in the right ventricle.

Bayesian analysis of the Substrate Ablation vs. Antiarrhythmic Drug Therapy for Symptomatic Ventricular Tachycardia trial

BACKGROUND AND AIMS

Bayesian analyses can provide additional insights into the results of clinical trials, aiding in the decision-making process. We analysed the Substrate Ablation vs. Antiarrhythmic Drug Therapy for Symptomatic Ventricular Tachycardia (SURVIVE-VT) trial using Bayesian survival models.

METHODS AND RESULTS

The SURVIVE-VT trial randomized patients with ischaemic cardiomyopathy and monomorphic ventricular tachycardia (VT) to catheter ablation or antiarrhythmic drugs (AAD) as a first-line strategy. The primary outcome was a composite of cardiovascular death, appropriate implantable cardioverter-defibrillator shocks, unplanned heart failure hospitalizations, or severe treatment-related complications. We used informative, skeptical, and non-informative priors with different probabilities of large effects to compute the posterior distributions using Markov Chain Monte Carlo methods. We calculated the probabilities of hazard ratios (HR) being <1, <0.9, and <0.75, as well as 2-year survival estimates. Of the 144 randomized patients, 71 underwent catheter ablation and 73 received AAD. Regardless of the prior, catheter ablation had a >98% probability of reducing the primary outcome (HR < 1) and a >96% probability of achieving a reduction of >10% (HR < 0.9). The probability of a >25% (HR < 0.75) reduction of treatment-related complications was >90%. Catheter ablation had a high probability (>93%) of reducing incessant/slow undetected VT/electric storm, unplanned hospitalizations for ventricular arrhythmias, and overall cardiovascular admissions > 25%, with absolute differences of 15.2%, 21.2%, and 20.2%, respectively.

CONCLUSION

In patients with ischaemic cardiomyopathy and VT, catheter ablation as a first-line therapy resulted in a high probability of reducing several clinical outcomes compared to AAD. Our study highlights the value of Bayesian analysis in clinical trials and its potential for guiding treatment decisions.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT03734562.

Automatic identification of areas with low-voltage fragmented electrograms for the detection of the critical isthmus of atypical atrial flutters

INTRODUCTION

Critical isthmuses of atypical atrial flutters (AAFLs) are usually located at slow conduction areas that exhibit fractionated electrograms. We tested a novel software, intended for integration with a commercially available navigation system, that automatically detects fractionated electrograms, to identify the critical isthmus in patients with AAFL ablation.

METHODS AND RESULTS

All available patients were analyzed; 27 patients with 33 AAFLs were included. The PentaRay NAV catheter (Biosense Webster) was used for mapping. The novel software was retrospectively applied; fractionated points with duration ≥80 ms and bipolar voltage between 0.05 and 0.5 mV were highlighted on the surface of maps. In 10 randomly chosen AAFLs, an expert electrophysiologist evaluated the positive predictive value of the algorithm to detect true fractionation: 74.4%. We tested the capacity of the software to identify areas of fractionation (defined as clusters of ≥3 adjacent points with fractionation) at the critical isthmus of the AAFLs (defined using conventional mapping criteria). An area of fractionation was identified at the critical isthmus in 30 cases (91%). Globally, 144 areas of fractionation (median number per AAFL 4 [3-6]) were identified. Duration of the fractionation or the surface of the areas was not different between areas at critical isthmuses and the rest. Setting the fractionation score filter of the software in nine provided best performance.

CONCLUSIONS

The novel software detected areas of fractionation at the critical isthmus in most AAFLs, which may help identify the critical isthmus in clinical practice.

Characterization of high-power and very-high-power short-duration radiofrequency lesions performed with a new-generation catheter and a temperature-control ablation mode

INTRODUCTION

High-power short-duration (HPSD) has been proposed to shorten procedure times while maintaining efficacy and safety. We evaluated the differences in size and geometry between radiofrequency lesions obtained with this method and conventional ones.

METHODS AND RESULTS

Twenty-eight sets of 10 perpendicular radiofrequency applications were performed with two commercially available catheters: a temperature-controlled HPSD catheter (QDot-Micro) and a conventional power-controlled catheter (Thermocool SmartTouch) on porcine left ventricle. Different power settings (35, 40, 50, and 90 W), contact force (CF; 10 and 20 g), ablation index (AI; 400 and 550), and application times were combined to create conventional (35-40 W), HPSD (50 W) and very-high-power short-duration (VHPSD; 90 W) lesions, that were cross-sectioned and measured. About 4-s VHPSD lesions were smaller, shallower, and thinner than HPSD performed with the QDot-Micro catheter in any scenario of CF or AI (61 ± 7.8 mm³ , 6.1 ± 0.3 mm wide, and 2.9 ± 0.1 mm deep with 10 g; 72.2 ± 0.5 mm³ , 6.8 ± 0.3 mm wide, and 2.9 ± 0.2 mm deep with 20 g). Conventional and HPSD lesions performed with the temperature-controlled catheter were generally bigger, deeper, and wider than the ones obtained with the power-controlled catheter, as well as more consistent in size. This was especially true with the lower CF and AI scenario, while differences were less notable with other setting combinations.

CONCLUSION

VHPSD lesions performed with QDot-Micro catheter were smaller than any other lesions, which is especially attractive for posterior left atrial wall ablation. On the contrary, conventional-powered and HPSD lesions performed with this catheter were equally sized (or even bigger with lower CF and AI objectives), as well as more consistent in size, which would guarantee transmurality in other locations.

Stabilization of unstable reentrant atrial tachycardias via fractionated continuous electrical activity ablation (CHAOS study)

BACKGROUND

Unstable reentrant atrial tachycardias (ATs) (i.e., those with frequent circuit modification or conversion to atrial fibrillation) are challenging to ablate. We tested a strategy to achieve arrhythmia stabilization into mappable stable ATs based on the detection and ablation of rotors.

METHODS

All consecutive patients from May 2017 to December 2019 were included. Mapping was performed using conventional high-density mapping catheters (IntellaMap ORION, PentaRay NAV, or Advisor HD Grid). Rotors were subjectively identified as fractionated continuous (or quasi-continuous) electrograms on 1-2 adjacent bipoles, without dedicated software. In patients without detectable rotors, sites with spatiotemporal dispersion (i.e., all the cycle length comprised within the mapping catheter) plus non-continuous fractionation on single bipoles were targeted. Ablation success was defined as conversion to a stable AT or sinus rhythm.

RESULTS

Ninety-seven patients with reentrant ATs were ablated. Of these, 18 (18.6%) presented unstable circuits. Thirteen (72%) patients had detectable rotors (median 2 [1-3] rotors per patient); focal ablation was successful in 12 (92%). In the other 5 patients, 17 sites with spatiotemporal dispersion were identified and targeted. Globally, and excluding 1 patient with spontaneous AT stabilization, ablation success was achieved in 16/17 patients (94.1%). One-year freedom from atrial arrhythmias was similar between patients with unstable and stable ATs (66.7% vs. 65.8%, p = 0.946).

CONCLUSIONS

Most unstable reentrant ATs show detectable rotors, identified as sites with single-bipole fractionated quasi-continuous signals, or spatiotemporal dispersion plus non-continuous fractionation. Ablation of these sites is highly effective to stabilize the AT or convert it into sinus rhythm.

Substrate Ablation vs Antiarrhythmic Drug Therapy for Symptomatic Ventricular Tachycardia

BACKGROUND

In patients with ischemic cardiomyopathy and an implantable cardioverter-defibrillator (ICD), catheter ablation and antiarrhythmic drugs (AADs) reduce ICD shocks, but the most effective approach remains uncertain.

OBJECTIVES

This trial compares the efficacy and safety of catheter ablation vs AAD as first-line therapy in ICD patients with symptomatic ventricular tachycardias (VTs).

METHODS

The SURVIVE-VT (Substrate Ablation vs Antiarrhythmic Drug Therapy for Symptomatic Ventricular Tachycardia) is a prospective, multicenter, randomized trial including patients with ischemic cardiomyopathy and appropriated ICD shock. Patients were 1:1 randomized to complete endocardial substrate-based catheter ablation or antiarrhythmic therapy (amiodarone + beta-blockers, amiodarone alone, or sotalol ± beta-blockers). The primary outcome was a composite of cardiovascular death, appropriate ICD shock, unplanned hospitalization for worsening heart failure, or severe treatment-related complications.

RESULTS

In this trial, 144 patients (median age, 70 years; 96% male) were randomized to catheter ablation (71 patients) or AAD (73 patients). After 24 months, the primary outcome occurred in 28.2% of patients in the ablation group and 46.6% of those in the AAD group (hazard ratio [HR]: 0.52; 95% CI: 0.30-0.90; P = 0.021). This difference was driven by a significant reduction in severe treatment-related complications (9.9% vs 28.8%, HR: 0.30; 95% CI: 0.13-0.71; P = 0.006). Eight patients were hospitalized for heart failure in the ablation group and 13 in the AAD group (HR: 0.56; 95% CI: 0.23-1.35; P = 0.198). There was no difference in cardiac mortality (HR: 0.93; 95% CI: 0.19-4.61; P = 0.929).

CONCLUSIONS

In ICD patients with ischemic cardiomyopathy and symptomatic VT, catheter ablation reduced the composite endpoint of cardiovascular death, appropriate ICD shock, hospitalization due to heart failure, or severe treatment-related complications compared to AAD. (Substrate Ablation vs Antiarrhythmic Drug Therapy for Symptomatic Ventricular Tachycardia [SURVIVE-VT]: NCT03734562).

Impact of power and contact force on index-guided radiofrequency lesions in an ex vivo porcine heart model

PURPOSE

Lesion size index (LSI) and ablation index (AI) are markers of lesion quality that incorporate power, contact force (CF) and time in a weighted formula to estimate lesion size. Although accurate predicting lesion depth in vitro, their precision in lesion size estimation has not been well established for certain power and CF settings. We conducted an experimental ex vivo study to analyse the effect of power and CF in size and morphology of ablation lesions in a porcine heart model.

METHODS

Twenty-four sets of 10 perpendicular epicardial radiofrequency applications were performed with two commercially available catheters (TactiCath, Sensor Enabled; and SmartTouch) on porcine left ventricle submerged in 37 °C saline, combining different power (25, 30, 35, 40, 50 and 60 W) and CF (10 and 20 g) settings, and aiming at a lower (LSI/AI of 5/400) or higher (LSI/AI of 6/550) index. After each application, lesions were cross-sectioned and measured.

RESULTS

Four hundred eighty lesions were performed. For a given target index and CF, significant differences in lesion volume and depth with different power were observed with both catheters, generally with smaller lesions using higher power. Lesions performed with CF of 10 g were particularly smaller with TactiCath compared to SmartTouch; lesions with CF of 20 g aiming a low LSI/AI were, however, bigger; lesions with CF of 20 g aiming a high LSI/AI were similar. In general, high-power lesions were wider and shallower than low-power lesions, especially with SmartTouch.

CONCLUSION

Size and morphology of index-guided radiofrequency lesions varied significantly with different power and CF settings.

High-density mapping with fragmentation analysis in patients with reentrant atrial tachycardias (MAP-FLURHY study)

PURPOSE

Reentrant atrial tachycardias (ATs) use areas of slow conduction that can be visualized as fragmented electrograms. We aimed to test an ablation strategy based on the identification and ablation of spots with fragmented electrograms in reentrant ATs, using Rhythmia navigation system.

METHODS

All consecutive patients from June 2016 to June 2019 were included. The IntellaMap ORION Catheter was used to detect sites with fragmentation, arbitrarily defined as fragmented electrograms > 70 ms. Entrainment was used to check if these areas belonged to the AT circuit. Ablation targeted the longest fragmented electrogram within the circuit: focal ablation for microreentries and lines for macroreentries. Ablation success was defined from each AT as conversion to sinus rhythm or another AT.

RESULTS

Twenty-seven consecutive patients with 44 mappable ATs were included. All ATs showed sites with fragmented electrograms (104 sites; 2.4 sites per AT); 43/44 ATs had fragmented electrograms within the circuit, which were the target of ablation. Ablation success: 34/36 ATs (94%); success could not be assessed in 8 circuits, in 6 due to mechanical conversion to sinus rhythm at the target fragmented site. Fragmented electrograms within the AT circuits were longer than electrograms outside the circuits (110 ± 30 vs 90 ± 15 ms, p < 0.001). A fragmentation duration > 100 ms/ > 40% of the AT cycle length predicted to be a successful site for ablation with 72.3%/73.8% specificity, respectively. Sixty-two percent of the patients were free from atrial arrhythmias at 1 year.

CONCLUSIONS

Most ATs had detectable fragmented electrograms within the circuit, which could be the target of ablation with high efficacy.

Heart failure hospitalization reduction and cost savings achieved by improved delivery of effective biventricular pacing: economic implications of the OLE study under the US setting

Background: The hOLter for Efficacy analysis (OLE) study demonstrated that current device pacing diagnostics overestimate the amount of cardiac resynchronization therapy (CRT) pacing that effectively stimulates the cardiac tissue. Sub-optimal pacing increases mortality, hospitalizations, and associated health-care costs. We sought to estimate the expected number of hospital admissions due to heart failure (HF) and its respective financial impact in patients with maximized effective pacing versus conventional pacing.

Methods: A Markov model was developed to project HF hospitalizations and quantify the costs that could be avoided if pacing was maximally effective. OLE data were used to inform the prevalence of ineffective pacing among CRT patients and and average loss of pacing by causes. Adaptive CRT trial data quantified the reduction in underlying hospitalization risk by increasing effective pacing delivered. Survival was informed by a meta-analysis of 5 randomized clinical trials. Costs were analyzed from a US payer perspective.

Results: Projected average hospitalizations totaled 4.58 over a lifetime horizon for CRT patients with conventional pacing. Maximizing effective pacing delivery was projected to avoid 1.83 HF admissions/patient over the lifetime. This equates to a savings of 40% (US$22,802) compared with conventional pacing from the Medicare perspective. In a sensitivity analysis, CRT with effective pacing was projected to provide cost savings in all scenarios.

Conclusions: Maximized effective pacing leads to a lower number of HF hospitalizations, thus allowing significant cost offsets in the US setting.

Contact force-sensing catheters: performance in an ex vivo porcine heart model

PURPOSE

Contact force (CF) catheters are useful to address proper contact during ablation. However, interactions between the ablation process, or its associated irrigation flow changes, with the CF sensing may translate into unexpected CF value fluctuations. We aimed to test for unintentional CF value variations during radiofrequency applications at a fixed applied force, with two commercially available catheters (TactiCath™ and SmartTouch™), and to evaluate its theoretical clinical significance by correlating CF-derived automatic ablation algorithms (force-time integral and lesion index) and actual lesion size at two standard CF values.

METHODS

Four series of 20 perpendicular epicardial ablations (20 W, 60 s, 17 ml/min) were performed on porcine left ventricle submerged in 37 °C saline. Catheters were mechanically fixed at a constant position and evaluated at 10 and 20 g. CF values were digitally analysed before each application changing irrigation rate (2-17-30 ml/min), and during ablation. Finally, lesions were quantified.

RESULTS

Increasing irrigation before ablation led to a slight but significant CF decrease. During ablation, CF showed a reproducible pattern: fast initial decrease, subsequent increase until higher-than-initial values and final plateau phase (CF variation up to 69% at 10 g). CF variability was significantly higher at 10 g and using TactiCath™. There were no major differences in lesion size between catheters at the same initial CF. CF only correlated mildly to lesion measures, and automatic algorithms globally failed to predict lesion size.

CONCLUSIONS

CF measured values spontaneously vary during ablation following a predictable pattern (initial decrease, subsequent increase and final plateau). This is especially remarkable applying lower CF.

Device pacing diagnostics overestimate effective cardiac resynchronization therapy pacing results of the hOLter for Efficacy analysis of CRT (OLÉ CRT) study

BACKGROUND

A high percentage of biventricular (BiV) or left ventricular (LV) pacing in cardiac resynchronization therapy (CRT) devices has been associated with superior clinical outcomes. However, the percent ventricular (%V) pacing reported by CRT devices simply indicates the number of paces the device has delivered and not the proportion of pacing that has captured the LV effectively.

OBJECTIVE

The purpose of this study was to determine whether a beat-by-beat evaluation of effective pacing would provide a more accurate evaluation of CRT delivery.

METHODS

An automatic electrogram (EGM)-based algorithm that classifies each LV pace as effective or ineffective based on detection of QS/QS-r morphology on the unipolar LV EGM during pacing was developed and validated. LV EGMs that were recorded by 24-hour Holter from 57 CRT patients were postprocessed. The percent effective CRT (%e-CRT) pacing was calculated by dividing the time spent in e-CRT pacing by the total time of the recording.

RESULTS

In this CRT cohort, the average %V pacing (94.8% ± 8%) significantly overestimated the %e-CRT pacing (87.5% ± 23%; P <.001). A significant minority of subjects (18%) had a discrepancy of at least 3 percentage points between %V pacing and %e-CRT pacing (mean 39% ± 41%).

CONCLUSION

Current device pacing diagnostics overestimate the amount of CRT pacing actually delivered. The new algorithm quantifies ineffective CRT pacing, which enables clinicians to identify patients with this issue and to address the reasons behind suboptimal CRT delivery.

Impact of previous cardiac surgery on long-term outcome of cavotricuspid isthmus-dependent atrial flutter ablation

AIMS

The aim of this study was to determine the acute and long-term outcome of radiofrequency catheter ablation (RFCA) for cavotricuspid isthmus-dependent atrial flutter (CTI-AFL) in adults with and without previous cardiac surgery (PCS), and predictors of these outcomes. Structural alterations of the anatomical substrate of the CTI-AFL are observed in post-operative patients, and these may have an impact on the acute success of the ablation and in the long-term.

METHODS AND RESULTS

Clinical records of consecutive adults undergoing RFCA of CTI-AFL were analysed. Two main groups were considered: No PCS and PCS patients, who were further subdivided into acquired heart disease (AHD: ischaemic heart disease and valvular/mixed heart disease) and congenital heart disease [CHD: ostium secundum atrial septal defect (OS-ASD) and complex CHD]. Multivariate analysis identified clinical and procedural factors that predicted acute and long-term outcomes. A total of 666 patients (73% men, age 65 ± 12 years) were included: 307 of them with PCS. Ablation was successful in 647 patients (97%), 96% in the PCS group and 98% in the No PCS group (P = 0.13). Regression analysis showed that surgically corrected complex CHD was related to failure of the procedure [odds ratio 5.6; 95% confidence interval (CI) 1.6-18, P = 0.008]. After a follow-up of 45 ± 15 months, recurrences were observed in 90 patients (14%), more frequently in the PCS group: absolute risk of recurrence 18 vs. 10.5%, relative risk 1.71, 95% CI: 1.2-2.5, P = 0.006. Multivariate analysis indicated that the types of PCS [OS-ASD vs. No PCS: hazard ratio (HR) 2.57; 95% CI: 1.1-6.2, P = 0.03 and complex CHD vs. No PCS: HR 2.75; 95% CI: 1.41-5.48, P = 0.004], female gender (HR 1.55; 95% CI: 1.04-2.4, P = 0.048), and severe LV dysfunction (HR 1.36; 95% CI: 1.06-1.67, P = 0.04) were independent predictors of long-term recurrence.

CONCLUSION

Radiofrequency catheter ablation of CTI-AFL after surgical correction of AHD and CHD is associated with high acute success rates. The severity of the structural alterations of the underlying heart disease and consequently the type of surgical correction correlates with higher risk for recurrence.

Long-Term Outcome After Ablation of Right Atrial Tachyarrhythmias After the Surgical Repair of Congenital and Acquired Heart Disease

Atrial myopathy, atriotomies, and fibrotic scars are the pathophysiological substrate of lines of conduction block, promoting atrial macroreentry. The aim of this study was to determine the acute and long-term outcome of radiofrequency catheter ablation (RFCA) for right atrial tachyarrhythmia (AT) in adults after cardiac surgery for congenital heart disease (CHD) and acquired heart disease (AHD) and predictors of these outcomes. Clinical records of adults after surgery for heart disease undergoing RFCA of right-sided AT were analyzed retrospectively. Multivariate analyses identified clinical and procedural factors predicting acute and long-term outcomes. A total of 372 patients (69% men; age 61 ± 15 years) after surgical repair of CHD (n = 111) or AHD (n = 261) were studied. Cavotricuspid isthmus-dependent atrial flutter (CTI-AFL) was observed in 300 patients and non-CTI-AFL in 72 patients. Ablation was successful in 349 cases (94%). During a mean follow-up of 51 ± 30 months, recurrences were observed in 24.5% of patients. Multivariate analysis showed that non-CTI-AFL (hazard ratio [HR] 1.78, 95% confidence interval [CI] 1.1 to 2.9) and CHD (HR 1.75, 95% CI 1.07 to 2.9) were independent predictors of long-term recurrences. Multivariate analysis showed that female gender (HR 2.29, 95% CI 1.6 to 3.3), surgery for AHD (HR 95% 2.31, 95% CI 1.5 to 3.7), and left atrial dilatation (HR 2.1, 95% CI 1.3 to 3.2) were independent predictors of long-term atrial fibrillation. In conclusion, RFCA of right-sided AT after cardiac surgery is associated with high acute success rates and significant long-term recurrences. Non-CTI-dependent AFL and surgery for CHD are at higher risk of recurrence. Atrial fibrillation is common during follow-up, particularly in patients with AHD and enlarged left atrium.

Remote monitoring of cardiac implantable electronic devices in Europe: results of the European Heart Rhythm Association survey

The aim of this European Heart Rhythm Association survey was to provide an insight into the current use of remote monitoring for cardiac implantable electronic devices in Europe. The following topics were explored: use of remote monitoring, infrastructure and organization, patient selection and benefits. Centres using remote monitoring reported performing face-to-face visits less frequently. In many centres (56.9%), a nurse reviews all the data and forwards them to the responsible physician. The majority of the centres (91.4%) stated that remote monitoring is best used in patients with implantable cardioverter-defibrillators and those live far from the hospital (76.6% top benefit). Supraventricular and ventricular arrhythmias were reported to be the major events detected earlier by remote monitoring. Remote monitoring will have a significant impact on device management.

Current practice for diagnosis and management of silent atrial fibrillation: results of the European Heart Rhythm Association survey

Although it is well known that silent atrial fibrillation (AF) is associated with morbidity and mortality rates similar to those of symptomatic AF, no specific strategy for screening and management of this form of AF has been advocated. The purpose of this survey was to identify current practices for the diagnosis and management of silent AF. This survey is based on an electronic questionnaire sent to the European Heart Rhythm Association Research Network partners. Responses were received from 33 centres in 16 countries. The preferred screening methods for silent AF in patients with rhythm control by pharmacological therapy was 12-lead electrocardiogram (ECG) at outpatient visits (31.3%) and periodical 24 h Holter ECG recordings (34.4%), while after pulmonary vein isolation the corresponding figures were 6.3 and 65.6%, respectively. No consensus has been reached concerning the therapeutic approach for such patients. Most responders preferred rate control over rhythm control in patients with silent AF, although some favoured pulmonary vein isolation in young patients. However, oral anticoagulant therapy in patients at high thromboembolic risk was considered mandatory by most, provided that at least one episode of silent AF was documented, without recommending further investigations. The results of this survey have confirmed that there is currently no consensus regarding the screening and management of patients with silent AF and that clinical practice is not always consistent with the few existing evidence-based recommendations.

Catheter ablation vs. antiarrhythmic drug treatment of persistent atrial fibrillation: a multicentre, randomized, controlled trial (SARA study)

Background

Catheter ablation (CA) is a highly effective therapy for the treatment of paroxysmal atrial fibrillation (AF) when compared with antiarrhythmic drug therapy (ADT). No randomized studies have compared the two strategies in persistent AF. The present randomized trial aimed to compare the effectiveness of CA vs. ADT in treating persistent AF.

Methods and results

Patients with persistent AF were randomly assigned to CA or ADT (excluding patients with long-standing persistent AF). Primary endpoint at 12-month follow-up was defined as any episode of AF or atrial flutter lasting >24 h that occurred after a 3-month blanking period. Secondary endpoints were any atrial tachyarrhythmia lasting >30 s, hospitalization, and electrical cardioversion. In total, 146 patients were included (aged 55 ± 9 years, 77% male). The ADT group received class Ic (43.8%) or class III drugs (56.3%). In an intention-to-treat analysis, 69 of 98 patients (70.4%) in the CA group and 21 of 48 patients (43.7%) in the ADT group were free of the primary endpoint (P = 0.002), implying an absolute risk difference of 26.6% (95% CI 10.0–43.3) in favour of CA. The proportion of patients free of any recurrence (>30 s) was higher in the CA group than in the ADT group (60.2 vs. 29.2%; P < 0.001) and cardioversion was less frequent (34.7 vs. 50%, respectively; P = 0.018).

Conclusion

Catheter ablation is superior to medical therapy for the maintenance of sinus rhythm in patients with persistent AF at 12-month follow-up.

Clinical Trial Registration Information

NCT00863213 (http://clinicaltrials.gov/ct2/show/NCT00863213).

Economic assessment of cardiac resynchronization therapy

INTRODUCTION AND OBJECTIVES

Cardiac resynchronization devices have been shown to be effective in treating heart failure. They reduce overall mortality, heart failure mortality and hospitalizations due to heart failure. The aim of this study was to compare the cost-effectiveness of cardiac resynchronization therapy (CRT) with that of optimal drug therapy (ODT) by carrying out an economic assessment in the Spanish healthcare setting.

METHODS

An existing model was adapted for use in the Spanish healthcare setting. The effectiveness of cardiac resynchronization therapy was determined from published systematic reviews. The costs of the various interventions were determined using a range of Spanish data sources. The model adopted the perspective of the public health system and the time horizon considered was the remainder of the patient's life. The outcome variables were life-years gained and quality-adjusted life-years (QALYs) gained.

RESULTS

Overall, ODT, CRT and CRT with a defibrillator resulted in gains of 2.11, 2.8 and 3.19 QALYs, respectively, at a cost of €11,722, €31,629 and €52,592, respectively. Consequently, each QALY gained with CRT relative to ODT involved the consumption of €28,612 of additional resources. Similarly, the use of CRT with a defibrillator cost an additional €53,547 per QALY relative to CRT without a defibrillator.

CONCLUSIONS

The use of CRT without a defibrillator could be a cost-effective alternative to ODT for treating heart failure in a carefully selected group of patients. The study results were sensitive to uncertainties in many of the variables used in the model.

Selecting the best site for pacing leads after cardiac surgery by evaluating the asynchrony of myocardial deformation observed with different pacing sites

INTRODUCTION AND OBJECTIVES

After cardiac surgery, temporary pacing leads are routinely implanted in the right ventricle (RV). The objective was to investigate the effect of different ventricular pacing locations on cardiac synchrony (by evaluating myocardial deformation, or strain) and efficiency in patients undergoing cardiac surgery.

METHODS

Interventricular asynchrony (i.e. the difference in the time of onset of deformation between right and left ventricles; Tε-R/L) and intraventricular asynchrony (i.e. the standard deviation and maximum difference in the time of onset of deformation in six segments of the left ventricle [LV]; Tε-SD and Tε-MD, respectively) were assessed in 19 patients. Doppler echocardiography was used to evaluate these parameters and cardiac output after pacing in the RV and in three different LV segments.

RESULTS

Pacing in the RV resulted in the greatest increases in asynchrony parameters from baseline: Tε-R/L 59.8 ms (standard deviation [SD] 40.5 ms) vs. 28.23 ms (SD 56.9 ms), P=.002; Tε-SD 53.2 ms (SD 34.4 ms) vs. 36.6 ms (SD 34.9 ms), P=.007; and Tε-MD 135.3 ms (SD 82.9 ms) vs. 90.5 ms (SD 87.4 ms), P=.007. Pacing in the LV resulted in less asynchrony: for anterior LV pacing, Tε-R/L was 17.2 ms (SD 53.8 ms), Tε-SD was 35.8 ms (SD 17.9 ms), and Tε-MD was 91.3 ms (SD 45.2). The change from baseline was not significant. Cardiac output was lower after RV pacing than after anterior LV pacing: 4.36 (SD 1) vs. 4.70 (SD 1); P=.001.

CONCLUSIONS

Pacing in the LV produced less asynchrony than RV pacing. In addition, anterior LV pacing resulted in a higher cardiac output than RV pacing. These findings suggest that the location normally used for temporary leads after cardiac surgery should be changed.

Non-antiarrhythmic drugs to prevent atrial fibrillation

Atrial fibrillation (AF) is the most frequent arrhythmia found in clinical practice. The majority of patients with AF are still candidates for antiarrhythmic drug treatment, not only for acute reversion to sinus rhythm but also for long-term treatment to prevent recurrences of AF. Currently available antiarrhythmic drugs, however, are unable to provide complete efficacy in all patients, and present problematic risks of proarrhythmia. The progressively increasing prevalence of AF supports the need to develop improved therapeutic approaches for the clinical management of arrhythmia. Accordingly, new treatment techniques aimed at suppressing the origin of the arrhythmogenic foci have been developed in the last decade. However, ablative treatments are only available for selected patients. Because of these factors, and also because primary prevention of AF should be our goal, the introduction of non-antiarrhythmic agents that could prevent both new-onset AF and recurrences of AF may eventually improve patient outcomes and reduce the incidence of this epidemic disease. The potential clinical value of these non-antiarrhythmic options is currently under active investigation. There is now clinical and experimental evidence that many drugs may have beneficial effects in preventing AF through several possible mechanisms. Non-antiarrhythmic drugs, such as ACE inhibitors and angiotensin receptor blockers, HMG-CoA reductase inhibitors (statins), corticosteroids, and N-3 polyunsaturated fatty acids may have a positive effect in patients with AF or in preventing AF in patients at risk.

[Clinical characteristics of patients with persistent atrial fibrillation referred for cardioversion: Spanish Cardioversion Registry (REVERSE)]

The objectives were to investigate the treatment and clinical characteristics of patients referred for cardioversion in Spain and to compare them with those reported in the AFFIRM (Atrial Fibrillation Follow-up Investigation of Rhythm Management) and RACE (RAte Control versus Electrical cardioversion) studies. The prospective study involved 1515 consecutive patients with persistent atrial fibrillation who were referred for cardioversion at 96 Spanish hospitals. Half of the patients were being treated with Vaughan-Williams group-I or -III antiarrhythmic drugs. The most frequently used approach to anticoagulation was to administer dicoumarins 34 weeks before and after cardioversion. Our patients were younger than those in the AFFIRM and RACE studies. Compared with AFFIRM patients, our patients had a lower prevalence of previous embolism, ischemic heart disease, hypertension, diabetes, and systolic dysfunction. Compared with RACE patients, our patients had a lower prevalence of ischemic heart disease and previous embolism, but a slightly higher prevalence of hypertension and diabetes. We conclude that patients referred for cardioversion in Spain clearly had a lower cardiovascular risk profile than those in the AFFIRM study, and appeared to have a lower risk profile than those in the RACE study.

Extracción de electrodos de marcapasos y desfibrilador mediante técnicas percutáneas

INTRODUCTION AND OBJECTIVES

There is an increasing need for endocardial pacing and defibrillators leads to be removed. However, the procedure can be complex and it is not risk-free. We reviewed our experience between April 1989 and June 2006 with the percutaneous extraction of leads.

METHODS

In total, 314 electrodes were extracted from 187 patients. The leads had been implanted over an average period of 69.16 months (range 0.11-234.6 months, median 60.25 months). Some 115 were atrial leads, 196 were ventricular, and three were in the coronary veins; of these, 78 had been abandoned in the vascular bed.

RESULTS

Indications for removal were infection (26.1%), dysfunction (22.9%), erosion (25%), endocarditis (20.7%), and bacteremia (2.7%). Overall, 58.8% of patients were referred from other departments. In 96.8%, the electrodes were completely removed. Simple traction was used in 23.4%, and countertraction techniques (with and without radiofrequency current support) were used in 60.7%. For abandoned leads, a biopsy clamp was used in combination with countertraction (4.3%) or a femoral approach with a snare (10.1%). A sternotomy was required in three of the 10 patients with remaining electrode fragments. The complication rate was 4.6% (with major complications in 2.5%). Complications were associated with age < 60 years (odds ratio [OR]=5.38, 95% confidence interval [CI] 1.07-27.23), the presence of endocarditis (OR=4.97: 95%CI, 1.04-23.70), and right side implantation (OR=17.09; 95% CI, 2.15-135.70).

CONCLUSIONS

In the majority of cases, pacing and defibrillator leads can be removed without difficulty using modern extraction techniques. However, because there is a risk of complications during extraction, even though it is low, the procedure should be carried out in specialized centers with surgical facilities.

Predictors of lack of response to resynchronization therapy

About 30% of patients treated with cardiac resynchronization therapy (CRT) do not respond to treatment. The aim of this study was to identify clinical predictors of lack of improvement in patients receiving CRT. From 197 consecutive patients scheduled to receive CRT, 143 fulfilled the inclusion criteria. Mean age was 68 +/- 7 years and 79% were men. Heart failure was due to ischemic heart disease in 49 patients (34%). Mean QRS duration was 165 +/- 26 ms, and left ventricular ejection fraction was 27 +/- 7%. Nonresponder patients were defined as those who died of heart failure, underwent heart transplantation, or did not increase the distance walked in 6 minutes >10%. At 6-month follow-up, there were 28 nonresponders (20%). Among nonresponders, 2 patients received a heart transplantation and 9 patients died of heart failure. In logistic regression analysis, independent predictors of lack of response to CRT were ischemic heart disease (odds ratio [OR] 2.9, 95% confidence interval [CI] 1.2 to 7; p = 0.023), severe mitral regurgitation (OR 3.5, 95% CI 1.3 to 9; p = 0.014), and left ventricular end-diastolic diameter > or =75 mm (OR 3.1, 95% CI 1.1 to 8; p = 0.026). Patients with these 3 predictors had a probability response of 27%.

[The value of cardiac troponin I as diagnostic test in the study of chest pain]

BACKGROUND AND OBJECTIVES

Cardiac troponin I is a highly sensitive and specific myocardial injury marker. We have analyzed the use of cardiac troponin I values in the diagnosis of coronary artery disease, in previously healthy patients who developed chest pain with inconclusive analytical and ECG diagnostic findings.

PATIENTS, MATERIAL AND METHODS

A one year cross-sectional consecutive study was conducted, in a total of 37 patients with no previously known heart disease who were admitted to the coronary unit for suspected anginal chest pain with normal cardiac enzymes and ECG. Abnormal cardiac troponin I levels at admission were defined as > or = 0.4 ng/ml, and were compared with coronary angiography or exercise test results and related to the duration of pain and the time from the appearance of symptoms to blood extraction.

RESULTS

Thirty-three of the 37 initially included patients were studied. Coronary artery disease was diagnosed in 22, 15 of whom had increased troponin I values, yielding a sensitivity of 68% (48%-84%) and a specificity of 82% (53%-97%). In the subgroup of patients with pain lasting > 30 min, sensitivity reached 85% (59%-97%) and specificity 83% (42%-99%). There were no significant differences between subgroups with different time delays from appearance of symptoms to blood extraction.

CONCLUSIONS

Cardiac troponin I is very useful for the studying ischemic chest pain without a definitive diagnostic ECG nor biochemical data, resulting in a high sensitivity and specificity for myocardial ischemic injury detection. Its diagnostic value increases in cases of prolonged pain episodes.

Protective effects of acidic fibroblast growth factor against cardiac arrhythmias induced by ischemia and reperfusion in rats

An in vivo study has been conducted to evaluate the effect of acidic fibroblast growth factor (aFGF) on cardiac arrhythmias which occur in transient myocardial ischemia followed by reperfusion. In a rat model of myocardial ischemia and reperfusion, cardiac arrhythmias were assessed during the first three minutes of reperfusion. Systemic administration of 2.6 micrograms aFGF just before coronary recirculation resulted in a significant reduction in incidence and severity of ventricular extra beats (VEBs), ventricular tachycardia (VT) and ventricular fibrillation (VF), compared with control rats (VT incidence: 30% vs 80%, VF incidence: 10% vs 40%; episodes of VT: 4.1 +/- 0.34 vs 8.8 +/- 0.95; episodes of VF: 4.8 +/- 0.32 vs 11.5 +/- 1.47). Our results suggest a novel role for FGFs as potential antiarrhythmic agents.

Cardiovascular toxicities related to the infusion of cryopreserved grafts: results of a controlled study

To evaluate cardiovascular toxicities associated with the infusion of cryopreserved grafts, we prospectively monitored the infusions of 29 autologous bone marrow transplant (BMT) recipients. Fifteen allogeneic BMT recipients served as a control group. Cardiac rhythm was recorded continuously with the Holter technique from at least 2 h before the start of graft infusion until 24 h after completion. Blood pressure was closely monitored during the same period. Graft infusions were performed through a standard transfusion filter with breaks between aliquots. When the infusion had commenced, diuretics were given frequently (40 and 40% of allogeneic BMT and autologous BMT recipients, respectively) to avoid fluid overload. Non-cardiovascular clinical toxicities were observed more frequently in autologous BMT patients (41% vs 6%, p = 0.02) and no significant differences were seen between autograft and allograft recipients in any of the measured cardiovascular parameters. The heart rate decreased slightly in both groups but no patient in either group had a heart rate of < 60 b.p.m. or heart block. No significant changes in blood pressure were detected in either group. Ventricular ectopic beats/atrial ectopic beats ratio increased in the autologous BMT group after graft infusion (0.7 vs 0, p = 0.1). Time to engraftment did not differ significantly from other published series. Our results suggest that increasing infusion time of cryopreserved material and using a standard filter may reduce toxicities associated with the infusion of cryopreserved grafts. Early administration of diuretics may contribute to better control of blood pressure.

Third-degree atrioventricular block in an athlete

There is a wide spectrum of changes in the resting electrocardiograms of athletes. We here present a case of third-degree atrioventricular block in an asymptomatic young athlete.

[Cardiac fulguration. A healing treatment for intranodal re-entry tachycardias refractory to medication]

Six patients underwent fulguration of the AV junction for typical paroxysmal intranodal reentry tachycardias, refractory to medical treatment. Unipolar cathodic discharges at distal electrode were administered against an external plate. Bipolar His and atrial deflections showed mean values of 0.16 and 0.54 mv, respectively. Mean energy used was 233 J (range 50-750), with a mean number of 1.6 (range 1-3) discharges per patient. Complete AV block was achieved, but conduction reappeared in all, within a mean of 30 minutes. Electrophysiologic evaluation was assessed 3-8 days after ablation. Intranodal reentry tachycardias could not be initiated in any patient. Retrograde conduction was abolished in 3 patients, and in three it was slow and decremental. First degree AV block, with intranodal delay was diagnosed in 4 with a mean AH interval of 237 msec (range 190-300). Mean rate for appearance of Wenckebach AV block was 154 b/m. None of the patients required permanent pacing. Mean follow-up of the patients was 6.8 months. One of the patients required a new ablation for reappearance of intranodal tachycardia and CAVB was achieved in the second ablation. The other five remain asymptomatic. Intranodal reentry tachycardias can be cured by fulguration. Less energy and less discharges should be administered to abolish functional dissociation of the AV node, without complete interruption of anterograde conduction.