Peter J. Stafford

Left ventricular dysfunction resulting from frequent unifocal ventricular ectopics with resolution following radiofrequency ablation

A case is presented, in which asymptomatic but persistent right ventricular outflow tract (RVOT) ectopics resulted in left ventricular (LV) dilatation and systolic dysfunction. The patient underwent extensive investigation with no other cause for the cardiomyopathy being found. Successful ablation of the RVOT ectopic focus resulted in normalization of LV size and function. This case suggests that frequent ventricular ectopy should be considered as a potentially remediable cause of LV dysfunction.

Arrhythmia Detection by Patient and Auto-Activation in Implantable Loop Recorders

AbstractAims: The Reveal® Plus implantable loop recorder offers additional automatic detection of arrhythmias that may not be symptomatic. We evaluated the clinical utility of this function compared with standard patient activation. Methods: Over an 18 month period, 50 consecutive patients (age 54 ± 20 years; 24 male) with unexplained dizziness, palpitations and/or syncope had ILR activations which were downloaded for analysis. Patient and auto-activation were analysed with respect to arrhythmia detection and the impact on management of patients was examined. Results: Patient symptoms were syncope in 72% and non-syncope (dizziness and/or palpitations) in 28%. There were 181 patient activation events with 16% showing symptomatic arrhythmia leading to a positive diagnosis in 8 patients. Of 682 auto-activations, detection was appropriate in 17% and inappropriate in 83% (undersensing in 76% and oversensing in 24%). In 8 patients clinically relevant arrhythmia was detected by patient activation alone. In 4 of these patients, further arrhythmia was detected by auto-activation. No patient had important arrhythmia detected only by auto-activation. Conclusion: Automatic detection of asymptomatic arrhythmia did not appear to improve the diagnostic utility of the ILR in our series. The large number of stored inappropriate auto-activation events limits the ability of this function to detect clinically relevant arrhythmia. Symptom-rhythm correlation using the patient activation function remains clinically useful in patients with unexplained syncope or palpitation.

Prediction of Maintenance of Sinus Rhythm after Cardioversion of Atrial Fibrillation by Analysis of Serial Signal‐Averaged P Waves

After cardioversion from atrial fibrillation (AF) many patients develop early recurrence of the arrhythmia. While these patients may be appropriate for immediate prophylaxis against AF recurrence their identification at the time of cardioversion is not possible. Since the signal‐averaged P wave (SAPW) is abnormal in individuals with atrial arrhythmia, we assessed its utility for predicting early AF recurrence after cardioversion. Seventy‐five cardioversions in 31 patients were evaluated. The mean age was 59 (range 28–79) years; 26 were male. Fifty‐eight cardioversions were internal using low energy biphasic DC shocks delivered via electrodes placed in the right atrial appendage and coronary sinus. P wave specific signal averaging was performed at 3 and 24 hours after each cardioversion to estimate filtered P wave duration and energy from 20, 40, and 60 to 150 Hz. Follow‐up was by regular clinic visits and transtelephonic ECG monitoring. Early recurrence of AF (prospectively defined as sinus rhythm duration < 1 week) occurred after 30 cardioversions. No differences were found in any P wave variable measured at 3 hours between these cardioversions and those that resulted in a longer duration of sinus rhythm. Paired 3‐ and 24‐hour signal‐averaged data were available in 47 cardioversions. There were significant falls in P wave energy from 3 to 24 hours after 31 cardioversions that resulted in sinus rhythm for > 1 week, (P40: 3 hours 11.2 [±1.5] μV2· s, 24 hours 8.6 [±1.2] μV2· s, P < 0.001), but not following the 16 after which AF returned within 1 week (P40: 3 hours 9.0 [±1.2] μV2· s, 24 hours 8.5 [±1.2] μV2· s, P = NS). A fall in P40 of > 25% had a positive predictive accuracy for maintenance of sinus rhythm of 87%; negative predictive accuracy was only 37%. Similar falls in P wave energy occurred after cardioversions that resulted in longer term (> 4 weeks) sinus rhythm, but not in those that did not. However, the predictive accuracy of a fall in P40 was less (positive predictive accuracy 38%, negative predictive accuracy 62%). Patients with relapsing permanent AF who remain in sinus rhythm for at least 1 week after cardioversion show a fall in P wave energy within the first 24 hours. However, in these patients the technique does not predict recurrent AF within 1 week nor sinus rhythm > 4 weeks. These observations suggest persistent disordered atrial activation as a mechanism for early recurrence of AF after cardioversion.

Video‐Assisted Thoracoscopic Implantation of the Left Ventricular Pacing Lead for Cardiac Resynchronization Therapy

Background: To study the feasibility and efficacy of video‐assisted thoracoscopic (VAT) placement of the left ventricular pacing lead for cardiac resynchronization therapy (CRT) where the conventional transvenous coronary sinus approach has failed.

Distinctive Patterns of Dominant Frequency Trajectory Behavior in Drug-Refractory Persistent Atrial Fibrillation: Preliminary Characterization of Spatiotemporal Instability

The role of substrates in the maintenance of persistent atrial fibrillation (persAF) remains poorly understood. The use of dominant frequency (DF) mapping to guide catheter ablation has been proposed as a potential strategy, but the characteristics of high DF sites have not been extensively studied. This study aimed to assess the DF spatiotemporal stability using high density noncontact mapping (NCM) in persAF.

Increase in organization index predicts atrial fibrillation termination with flecainide post-ablation: spectral analysis of intracardiac electrograms.

AIMS The mechanism of the action of flecainide in the termination of human atrial fibrillation (AF) is not fully understood. We studied the acute effects of flecainide on AF electrograms in the time and frequency domain to identify factors associated with AF termination. METHODS AND RESULTS Patients who were still in AF at the end of catheter ablation for AF were given intravenous flecainide. Dominant frequency (DF) and organization index (OI) were obtained by fast Fourier transform of electrograms from the coronary sinus catheter over 10 s in AF, before and after flecainide infusion. Mean AF cycle length (CL) was also calculated. Twenty-six patients were studied (16 paroxysmal AF and 10 persistent AF). Seven converted to sinus rhythm (SR) with flecainide. In all patients, mean CL increased from 211 +/- 44 to 321 +/- 85 ms (P < 0.001). Mean DF decreased from 5.2 +/- 1.03 to 3.6 +/- 1.04 Hz (P < 0.001). Mean OI was 0.33 +/- 0.13 before and 0.32 +/- 0.11 after flecainide (P = 0.90). Comparing patients who converted to SR with those who did not, OI post-flecainide was 0.41 +/- 0.12 vs. 0.29 +/- 0.10 (P = 0.013), and the relative change in OI was 29 +/- 33 vs. -3.9 +/- 27% (P = 0.016), respectively. No significant difference was noted in the change in CL and DF in the two groups. CONCLUSION Increase in OI, independent of changes to CL and DF, appears critical to AF termination with flecainide. Increase in OI holds promise as a sensitive predictor of AF termination.

High-resolution analysis of the surface P wave as a measure of atrial electrophysiological substrate

Background: At present atrial electrophysiology can only be assessed by invasive study. This limits available data in humans concerning atrial electrophysiologic changes in disease and in response to intervention. Indirect evidence suggests that the signal‐averaged P wave (SAPW) may provide noninvasive markers of atrial electrophysiology but no direct evaluations that measure both refractoriness and conduction time have been reported.

Prospective evaluation of two novel ECG-based restitution biomarkers for prediction of sudden cardiac death risk in ischaemic cardiomyopathy

Objective To improve prediction of sudden cardiac death (SCD) in patients with ischaemic cardiomyopathy (ICM). Electrical heterogeneity is known to contribute to risk of SCD. We have previously developed Regional Restitution Instability Index (R2I2), an ECG-based biomarker, which quantifies cardiac electrical instability by measuring heterogeneity in electrical restitution, and demonstrated its potential utility for risk stratification in a retrospective analysis of patients with ICM. Here, we examined R2I2 in a prospective ICM cohort and also tested the predictive value of another ECG-based biomarker, Peak ECG Restitution Slope (PERS). Methods Prospective, blinded, observational study of 60 patients with ICM undergoing implantable cardioverter defibrillator risk stratification. R2I2 was calculated from an electrophysiological study (EPS) using ECG surrogates for action potential duration and diastolic interval. R2I2 quantifies inter-lead electrical restitution heterogeneity. PERS was the peak restitution curve slope taken as a mean across the 12 ECG leads. Endpoints were ventricular arrhythmia (VA)/SCD. Results Over median follow-up of 22 months, 16 (26.6%) patients achieved endpoint. R2I2 was significantly higher in these patients compared with those without an event (mean±SEM: 1.11±0.09 vs 0.84±0.04, p=0.003) as was PERS (median(IQR): 1.35(0.60) vs 1.08(0.52), p=0.014). R2I2≥1.03, the cut-off used in our previous study, identified patients with a significantly higher risk of VA/SCD independent of EPS result, LVEF or QRS duration with a relative risk of 6.5 (p=0.008). Patients positive for R2I2 and PERS had a relative risk of VA/SCD 21.6 times that of those negative for R2I2 and PERS (p<0.0001). Conclusions R2I2 and PERS each independently and in combination, identify patients with ICM that are at high risk of developing ventricular arrhythmias (VA). R2I2/PERS represent promising risk markers for SCD discrimination. Trial registration number ClinicalTrials.gov Identifier: NCT01944514.

A Novel Surface Electrocardiogram–Based Marker of Ventricular Arrhythmia Risk in Patients With Ischemic Cardiomyopathy

Background Better sudden cardiac death risk markers are needed in ischemic cardiomyopathy (ICM). Increased heterogeneity of electrical restitution is an important mechanism underlying the risk of ventricular arrhythmia (VA). Our aim was to develop and test a novel quantitative surface electrocardiogram–based measure of VA risk in patients with ICM: the Regional Restitution Instability Index (R2I2). Methods and Results R2I2, the mean of the standard deviation of residuals from the mean gradient for each ECG lead at a range of diastolic intervals, was measured retrospectively from high-resolution 12-lead ECGs recorded during an electrophysiology study. Patient groups were as follows: Study group, 26 patients with ICM being assessed for implantable defibrillator; Control group, 29 patients with supraventricular tachycardia undergoing electrophysiology study; and Replication group, 40 further patients with ICM. R2I2 was significantly higher in the Study patients than in Controls (mean ± standard error of the mean: 1.09±0.06 versus 0.63±0.04, P<0.001). Over a median follow-up period of 23 months, 6 of 26 Study group patients had VA or death. R2I2 predicted VA or death independently of demographic factors, electrophysiology study result, left ventricular ejection fraction, or QRS duration (Cox model, P=0.029). R2I2 correlated with peri-infarct zone as assessed by cardiac magnetic resonance imaging (r=0.51, P=0.024). The findings were replicated in the Replication group: R2I2 was significantly higher in 11 of 40 Replication patients experiencing VA (1.18±0.10 versus 0.92±0.05, P=0.019). In combined analysis of ICM cohorts, R2I2 ≥1.03 identified subjects with significantly higher risk of VA or death (43%) compared with R2I2 <1.03 (11%) (P=0.004). Conclusions In this pilot study, we have developed a novel VA risk marker, R2I2, and have shown that it correlated with a structural measure of arrhythmic risk and predicted risk of VA or death in patients with ICM. R2I2 may improve risk stratification and merits further evaluation. (J Am Heart Assoc. 2012;1:e001552 doi: 10.1161/JAHA.112.001552.)

Noninvasive Assessment of Atrial Substrate Change after Wide Area Circumferential Ablation: A Comparison with Segmental Pulmonary Vein Isolation

Background: The wide area circumferential ablation (WACA) approach to atrial fibrillation is thought to result in ‘substrate modification’ perhaps related to autonomic denervation. We examined this prospectively by comparing WACA and segmental pulmonary vein isolation (PVI) using noninvasive surrogate markers.