Premature Ventricular Contractions and Ultra-High-Definition Mapping. Contribution and Limits.

BACKGROUND: The utility of ultra-high definition mapping (UHDM) for ablation of premature ventricular contractions (PVC) remains undetermined. The aim of this study was to investigate UHDM for PVC ablation, and additionally to compare to conventional technique. METHODS: Twenty patients investigated using UHDM were prospectively included and analyzed. Electrophysiological caracteristics and results were compared to 40 patients ablated using fluoroscopy only. RESULTS: 2541±2033 EGMs and 331±240 PVC beats were recorded for each patient. Surfaces of isochronal activations were 2.3±1.7 and 6.9±6.1 cm2 (first 10 and 20 ms). Local scar was present in 40% and local block in 65%. Areas of pace-mapping > 95, 90 and 85% concordance were 1.5±3.4, 2.1±3.9 and 3.3±5 cm2. Mean distance between the ablation site and the site of best pace-mapping or of earliest activation was 8±8 mm and 5±7 mm. Pre-potential was noted in 17% vs 26% controls (ns). QS pattern was present in 83% vs 83% controls (ns), and earliest activation was - 31±50 vs - 25±14 ms in controls (ns). Procedure (100±36 vs 190±51 min, p< 0.0001) and fluoroscopy duration (15±9 vs 24±9 min, p=0.005) were shorter in controls. Acute success was achieved in 65% patients with UHDM and in 72% controls (p=ns) with lower residual PVC burden in the control group. Over a follow-up of 19±12 months, long-term success was similar between groups (65 vs 68%). CONCLUSIONS: UHDM may reveal poorly recognized activation features and PVC mechanism. In this series, conventional mapping was quicker and did clinically as well as UHDM.

Long-Lasting Ventricular Fibrillation in Humans ECG Characteristics and Effect of Radiofrequency Ablation.

BACKGROUND: Studies of ventricular fibrillation (VF) in humans are limited because of the short available duration. We sought to study surface ECG waveforms and effect of ablation in long-lasting VF in patients with left assist devices. METHODS: Continuous 12-lead ECG of 5 episodes of long-lasting VF occurring in 3 patients with left ventricular assist device were analyzed. Spectral analysis (dominant frequency) and quantification of waveform amplitude, regularity (Unbiased Regularity Index), and complexity (Nondipolar Index) were performed over a median of 24 minutes of VF. Radiofrequency ablation was performed during VF in 2 patients. RESULTS: There was a significant increase in dominant frequency between VF onset and termination but none of the other parameters significantly changed. Some VF parameters varied from patient to patient and from lead to lead. Dominant frequency decreased after radiofrequency ablation in both cases and VF terminated spontaneously shortly after ablation in one case. The previously incessant VFs in these 2 patients did not recur afterward. CONCLUSIONS: VF rate increases over time in patients with left ventricular assist devices and is lowered by ablation. Long-lasting VF may be modified or even terminated by ablation.

Coagulation and heparin requirements during ablation in patients under oral anticoagulant drugs.

BACKGROUND: Anticoagulation during catheter ablation should be closely monitored with activated clotting time (ACT). However vitamin K antagonists (VKA) or direct oral anticoagulant drugs (DOAC) may act differently on ACT and on heparin needs. The aim of this study was to compare ACT and heparin requirements during catheter ablation under various oral anticoagulant drugs and in controls. METHODS: Sixty consecutive patients referred for ablation were retrospectively included: group I (n = 15, VKA), group 2 (n = 15, uninterrupted rivaroxaban), group 3 (n = 15, uninterrupted apixaban), and group 4 (n = 15, controls). Heparin requirements and ACT were compared throughout the procedure. RESULTS: Heparin requirements during the procedure were significantly lower in patients under VKA compared to DOAC, but similar between DOAC patients and controls.Activated clotting time values were significantly higher in patients under VKA compared to DOAC and similar in DOAC patients versus controls. Furthermore, anticoagulation control as evaluated by the number/proportion of ACT> 300 as well as the time passed over 300 seconds was significantly better in patients under VKA versus DOAC, without significant differences between DOAC and controls. Finally, the number of patients/ACT with excessive ACT values was significantly higher in VKA versus DOAC patients versus controls.There was no significant difference between rivaroxaban and apixaban for ACT or heparin dosing throughout the procedure. CONCLUSION: Vitamin K antagonists allowed less heparin requirement despite reaching higher ACT values and more efficient anticoagulation control (with more excessive values) compared to patients under DOAC therapy and to controls. There was no difference in heparin requirements or ACT between DOAC patients and controls.

Chest pain in Brugada syndrome: Prevalence, correlations, and prognosis role.

BACKGROUND: Brugada syndrome (BrS) is sometimes diagnosed because of chest pain. Prevalence and characteristics of such BrS patients are unknown. METHODS: A total of 200 BrS probands were retrospectively included. BrS diagnosis made because of chest pain (n = 34, 17%) was compared to the other ones. RESULTS: BrS probands with diagnosis because of chest pain had significantly more often smoker habits, increased body mass index, and familial history of coronary artery disease but less frequently previous resuscitated sudden death/syncope or atrial fibrillation. Presence of coronary spasm and familial coronary artery disease were independently associated with BrS diagnosed because of chest pain. They presented more often with spontaneous type 1 ST elevation (59% vs 26%, P = .0004) and higher ST elevation during the episode of chest pain compared to other patients or compared to baseline electrocardiogram after chest pain resumption. ST elevation during chest pain was lower compared to ajmaline test. A total of 20% of them had significant coronary artery disease and four (11%) had coronary spasm, and they experienced more often recurrent chest pain episodes (24% vs 5%, P = .0002). Presence of chest pain at BrS diagnosis was not correlated to future arrhythmic events in univariate analysis. Only previous sudden cardiac death (SD)/syncope and familial SD were still significantly associated with outcome in multivariate analysis. CONCLUSION: Chest pain is a common cause for BrS diagnosis, although major part is not apparently explained by ischemic heart disease. Mechanisms leading to chest main remain unknown in the other ones. ST elevation is higher in this situation but does not seem to carry poor prognosis.

Atrial Tachycardia With Atrial Activation Duration Exceeding the Tachycardia Cycle Length: Mechanisms and Prevalence.

OBJECTIVES: This study sought to identify atrial tachycardia (AT) demonstrating atrial activation duration (AAD) lasting longer than the length of the tachycardia cycle (TCL); to assess AT prevalence; and to evaluate the mechanisms and characteristics associated with these AT episodes by using the Rhythmia system (Boston Scientific, Marlborough, Massachusetts). BACKGROUND: Ultra-high-density mapping allows very accurate characterization of mechanisms involved in AT. Some complex patterns may involve AAD which is longer than the tachycardia cycle length (TCL) which makes maps difficult to interpret. Prevalence and characteristics of such ATs are unknown. METHODS: A cohort of 100 consecutive patients undergoing ablation of 125 right (n = 21) or left (n = 104) ATs using ultra-high-density mapping were retrospectively included. Offline calculation of right or left AAD was compared to TCL. RESULTS: Mean TCL was 293 ± 65 ms, and mean AAD was 291 ± 74 ms (p = NS). AT mechanisms were macro-re-entry in 74 cases (59%), localized re-entry in 27 cases (22%), and focal AT in 21 cases (17%) (types were mixed in 3 cases). Fifteen ATs (12%) had AADs that were longer than the TCL (71 ± 45 ms longer, from 10 to 150 ms). TCL was equal to the AAD in 97 ATs (78%), whereas 13 ATs (10%) had AAD shorter than the TCL (focal AT in each case). There were no differences between right and left atria for prevalence of ATs with AADs that were longer than the TCLs. There were significant differences in AT mechanisms according to the AAD-to-TCL ratio (p < 0.0001), with localized re-entry showing more often that AAD was longer than the TCL compared to that in focal AT and macro-re-entry. CONCLUSIONS: ATs with AAD lasting longer than the TCL were present in approximately 10% of the ATs referred for ablation, mostly in ATs caused by localized re-entry. Ultra-high-density mapping allows detection of these complex patterns of activation.

Correlations between arrhythmogenic substrate and noninvasive risk stratification in ischemic heart disease patients modifications by radiofrequency ablation.

INTRODUCTION: Several noninvasive risk factors for ventricular arrhythmias have been described in postmyocardial infarction (MI) patients, whose relationships with scar characteristics and modifications by ablation are unknown. METHODS: Twenty-two patients with previous MI referred for ventricular tachycardia ablation were prospectively included. ECG, heart rate variability (HRV), signal-averaged ECG (SA-ECG), and T wave alternans (TWA) were performed before and after radiofrequency ablation. Scar areas were correlated to preablation parameters. Pre and postablation parameters were furthermore compared. RESULTS: Left ventricular ejection fraction and some spectral and time-domain HRV parameters were significantly correlated to the scar areas. QRS duration was larger after vs before ablation (120 ± 29 vs 105 ± 22 msec, P = .01). No significant modification in time or spectral domain of HRV was observed. There was no significant change in TWA and SA-ECG before and after ablation. Borderline decreases in quantitative TWA parameters were noted in patients with positive TWA and successful ablation procedure. CONCLUSION: Some noninvasive risk factors were linked to the scar areas, but few were significantly modified after ablation. Larger populations are needed to demonstrate significant differences or correlations.

Hemodynamic consequences of premature ventricular contractions: Association of mechanical bradycardia and postextrasystolic potentiation with premature ventricular contraction-induced cardiomyopathy.

BACKGROUND: The relationships between hemodynamic consequences of premature ventricular contractions (PVCs) and development of premature ventricular contraction-induced cardiomyopathy (PVC-CM) have not been investigated. OBJECTIVE: The purpose of this study was to correlate concealed mechanical bradycardia and/or postextrasystolic potentiation (PEP) to PVC-CM. METHODS: Invasive arterial pressure measurements from 17 patients with PVC-CM and 16 controls with frequent PVCs were retrospectively analyzed. PVCs were considered efficient (ejecting PVCs) when generating a measurable systolic arterial pressure. PEP was defined by a systolic arterial pressure of the post-PVC beat ≥5 mm Hg higher than the preceding sinus beat. Every PVC was analyzed for 10 minutes before ablation, and the electromechanical index (EMi = number of ejecting PVCs/total PVC) and postextrasystolic potentiation index (PEPi = number of PVCs with PEP/total PVC) were calculated. RESULTS: EMi was 29% ± 31% in PVC-CM and 78% ± 20% in controls (P <.0001). PEPi was 41% ± 28% in PVC-CM and 14% ± 10% in controls (P = .001). There was no control in groups of low EMi or high PEPi. EMi and PEPi were not significantly correlated to left ventricular dimensions or function in PVC-CM patients. PVC coupling interval was related to both ejecting PVCs and PEP. CONCLUSION: Patients with PVC-CM more often display nonejecting PVCs and PEP compared to controls.

Three-dimensional mapping in the electrophysiological laboratory.

Investigation and catheter ablation of cardiac arrhythmias are currently still based on optimal knowledge of arrhythmia mechanisms in relation to the cardiac anatomy involved, in order to target their crucial components. Currently, most complex arrhythmias are investigated using three-dimensional electroanatomical navigation systems, because these are felt to optimally integrate both the anatomical and electrophysiological features of a given arrhythmia in a given patient. In this article, we review the technical background of available three-dimensional electroanatomical navigation systems, and their potential use in complex ablations.

High density mapping of inappropriate sinus tachycardia further looks into potential mechanisms.

Inappropriate sinus tachycardia (IST) is an incompletely understood condition associating unexpectedly fast sinus rates and debilitating symptoms whose management by sinus node modification/ablation demonstrated limited long-term success. We report about a case of IST who underwent two RF procedures using high density mapping system, highlighting some possibly specific features and discussing potential mechanisms.

Shortening of the Short Refractory Periods in Short QT Syndrome.

BACKGROUND: Diagnosis of short QT syndrome (SQTS) remains difficult in case of borderline QT values as often found in normal populations. Whether some shortening of refractory periods (RP) may help in differentiating SQTS from normal subjects is unknown. METHODS AND RESULTS: Atrial and right ventricular RP at the apex and right ventricular outflow tract as determined during standard electrophysiological study were compared between 16 SQTS patients (QTc 324±24 ms) and 15 controls with similar clinical characteristics (QTc 417±32 ms). Atrial RP were significantly shorter in SQTS compared with controls at 600- and 500-ms basic cycle lengths. Baseline ventricular RP were significantly shorter in SQTS patients than in controls, both at the apex and right ventricular outflow tract and for any cycle length. Differences remained significant for RP of any subsequent extrastimulus at any cycle length and any pacing site. A cut-off value of baseline RP <200 ms at the right ventricular outflow tract either at 600- or 500-ms cycle length had a sensitivity of 86% and a specificity of 100% for the diagnosis of SQTS. CONCLUSIONS: Patients with SQTS have shorter ventricular RP than controls, both at baseline during various cycle lengths and after premature extrastimuli. A cut-off value of 200 ms at the right ventricular outflow tract during 600- and 500-ms basic cycle length may help in detecting true SQTS from normal subjects with borderline QT values.

Prevalence of early repolarisation pattern in children.

BACKGROUND: Prevalence of early repolarisation ECG pattern (ER) has been repetitively determined in adults, but has not been reported in large unselected children populations so far. METHODS: ECG from 1000 successive healthy children from birth to 17years old were prospectively recorded and analyzed. ER was defined by ≥0.1mV J point elevation in at least two contiguous inferior or lateral ECG leads. Correlations with age, gender, ethnic origin, physical activity, Sokolow index and heart rate were performed. RESULTS: Prevalence of ER pattern was 23,6% (95% CI 21-26.2%) and increased after 8years of age. ER was independently correlated to a non Caucasian origin and a higher Sokolow index, but not to gender or level of physical activity. ER was independently correlated to an older age in children with heart rate <100bpm, and to a slower heart rate in children ≥8yo. CONCLUSION: ER is present in a quarter of children of various age and is related to ethnic origin, an older age, a slower heart rate and a higher Sokolow index.

Diaphragmatic Myopotential Oversensing Caused by Change in Implantable Cardioverter Defibrillator Sensing Bandpass Filter.

Diaphragmatic myopotential oversensing (DMO) causes inhibition of pacing and inappropriate detection of ventricular fibrillation in implantable cardioverter defibrillators (ICDs). It occurs almost exclusively with integrated bipolar leads and is extremely rare with dedicated bipolar leads. If DMO cannot be corrected by reducing programmed sensitivity, ventricular lead revision is often required. The new Low Frequency Attenuation (LFA) filter in St. Jude Medical ICDs (St. Jude Medical, Sylmar, CA, USA) alters the sensing bandpass to reduce T-wave oversensing. This paper aims to present the LFA filter as a reversible cause of DMO. Unnecessary lead revision can be avoided by the simple programming solution of deactivating this LFA filter.

Pacemaker-Mediated Tachycardia: Manufacturer Specifics and Spectrum of Cases.

Pacemaker-mediated tachycardia (PMT) is the term used to describe a repetitive sequence of sensed retrograde P waves followed by ventricular pacing at or below the maximum tracking rate. The following events can promote atrioventricular (AV) dissociation, retrograde conduction, and the onset of PMT: ventricular or atrial extrasystole, an excessively long programmed AV delay, external interference or myopotentials sensed by the atrial channel, atrial sensing or pacing failure, the absence of postventricular atrial refractory period extension after removal of a magnet, and VDD pacing at a higher rate than sinus rate. In contemporary devices, each manufacturer has a proprietary algorithm to detect and terminate PMT. Because of the increase in the number and complexity of the pacing algorithms and because of manufacturer-driven differences, a basic understanding of these new algorithms is important for patient care. We review here the main elements of the physiopathology of this type of tachycardia, describe the specific characteristics of the different manufacturers, and present representative clinical cases.