Letter by Jeilan et al regarding article, Longitudinal strain delay index by speckle tracking imaging: a new marker of response to cardiac resynchronization therapy .

We read with interest the recent article by Lim et al.1 This article demonstrated a strong correlation between a novel longitudinal strain delay index and left ventricular end-systolic volume reduction in both ischemic and nonischemic patients. The principle outlined by the authors is that an increased longitudinal strain delay index requires both dyssynchrony (defined in their article as a discrepancy between the time of end-systolic contraction and the time to peak strain) and residual contractility. Their concept elegantly considers the problem of cardiac resynchronization therapy (CRT) nonresponse in heart failure patients who have myocardial segments with delayed contraction due to scarred or akinetic segments. The index appears to address some of the limitations of time delay indices that do not take account of residual myocardial contractility. Patients with a high longitudinal strain delay index (dyssynchronous and contractile) are more likely to respond to CRT than are patients with a lower index (synchronous, akinetic, or both). In the authors’ model, an absolute discrepancy between the time of end-systolic contraction and the time to peak strain is 2 sided. Broadly speaking, resynchronization therapy works by preexciting the areas of latest activation in the dyssynchronous left ventricle. This traditional understanding of CRT-responsive dyssynchrony would suggest that peak strain in the dyssynchronous target segments should be delayed and occur after aortic valve closure (postsystolic segments).2–3 However, the proposed strain delay index also includes “presystolic segments” (peak strain occurring in segments before aortic valve closure) within an averaging calculation. Intuitively, it is difficult to understand why CRT may address this type of presystolic dyssynchrony. It would be useful to see whether data that eliminate these presystolic, earlier-contracting segments from the analysis or incorporate a measure of the variability of delay (eg, standard deviation) across the 16 segments studied within the data set might affect or improve the index’s performance. Also, the authors did not describe the effect of CRT on this index. Although CRT’s effect was not the remit of their article, it would be interesting to use these data to evaluate the differences in changes (pre- and post-CRT) to the longitudinal strain delay index score among responders and nonresponders

Ganglionic Plexus Ablation During Pulmonary Vein Isolation - Predisposing to Ventricular Arrhythmias?

Catheter ablation is increasingly used to treat patients with atrial fibrillation (AF). Ablation of ganglionic plexi is often performed to reduce vagal innervation and has been shown to confer a better long-term outcome in terms of AF recurrence. We report a case of a patient having AF ablation with a profound vagal response, suggesting ganglionic plexus ablation, who subsequently developed ventricular fibrillation after programmed ventricular stimulation. Reduced vagal modulation is known to predispose to ventricular arrhythmias and vagal denervation following AF ablation may predispose to ventricular arrhythmias and requires further study

Pulmonary Vein Isolation using a High Density Mesh Ablator Catheter: Incorporation of three-Dimensional Navigation and Mappin

Background: We evaluated the use of a novel High Density Mesh Ablator (HDMA) catheter in combination with three-dimensional navigation for the treatment of paroxysmal atrial fibrillation. Methods: The HDMA catheter was used to carry out pulmonary vein isolation in a consecutive series of patients. Three-dimensional geometry of the left atrial-pulmonary vein (LA-PV) junctions were first created with the HDMA catheter. Ostial, proximal and distal sites within the pulmonary veins were tagged with catheter shadows on the created geometry to allow for re-interrogation of these exact sites after ablation. Results: The HDMA catheter was successfully used to create three dimensional geometry of the LA-PV junction in a total of 20 pulmonary veins which involved 5 patients. In all cases, ostial ablation alone was sufficient to achieve electrical isolation. No significant pulmonary vein stenosis was seen acutely after ablation. Conclusion: We describe the successful use of the novel HDMA catheter to create three-dimensional geometry of the LA-PV junction to assist with pulmonary vein isolation

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 \u3c 0.001). Mean DF decreased from 5.2 ± 1.03 to 3.6 ± 1.04 Hz ( P \u3c 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

Contributing factors concerning inconsistencies in persistent atrial fibrillation ablation outcomes

Background: We investigated current clinical methods for complex fractionated atrial electrogram (CFAE) classification during persistent atrial fibrillation (persAF). In particular, factors that directly influence the low reproducibility of CFAE-guided ablation outcomes in persAF therapy, such as inconsistencies in automated CFAE classification performed by different systems, the co-existence of different types of atrial electrograms (AEGs), and insufficient AEG duration for CFAE detection. Methods: 797 bipolar AEGs were exported from NavX (St. Jude Medical) from 18 persAF patients undergoing pulmonary vein isolation and roof line ablation (PVI+RL). CFE-Mean, CFE-StdDev and peak-to-peak were exported from NavX, while the interval confidence level, average and shortest complex interval – as defined by CARTO (Biosense Webster) – were calculated offline using a validated MATLAB script. Sample entropy, dominant frequency and organization index were also calculated offline. Results: First, we show that CFAE classification varies for the same individual, depending on the commercial system being used. Revised thresholds were found for the indices calculated by each system to minimize the differences in automated CFAE detection performed independently by them. Second, our results show that some AEGs are affected by PVI+RL in persAF, while others remain unaffected by it. Different types of AEGs might correlate with distinct underlying persAF mechanisms. Multivariate analysis using the multiple descriptors measured from the AEGs effectively discriminated the different types of AEGs. Finally, we show that consecutive AEGs with 2.5 s resulted in different ablation target identification using the CARTO criterion, which would affect the ablation strategy and contribute to conflicting outcomes in AEGguided ablation in persAF. Our results suggest that CARTO should consider AEGs with longer duration to measure CFAEs. Conclusions: A thorough re-evaluation of the definition of CFAE is necessary in order to refine the identification of critical atrial regions responsible for the perpetuation of the arrhythmia in patients with persAF

Minimizing discordances in automated classification of fractionated electrograms in human persistent atrial fibrillation

Ablation of persistent atrial fibrillation (persAF) targeting complex fractionated atrial electrograms (CFAEs) detected by automated algorithms has produced conflicting outcomes in previous electrophysiological studies. We hypothesize that the differences in these algorithms could lead to discordant CFAE classifications by the available mapping systems, giving rise to potential disparities in CFAE-guided ablation. This study reports the results of a head-to-head comparison of CFAE detection performed by NavX (St. Jude Medical) versus CARTO (Biosense Webster) on the same bipolar electrogram data (797 electrograms) from 18 persAF patients. We propose revised thresholds for both primary and complementary indices to minimize the differences in CFAE classification performed by either system. Using the default thresholds [NavX: CFEMean ≤ 120 ms; CARTO: ICL ≥ 7], NavX classified 70 % of the electrograms as CFAEs, while CARTO detected 36 % (Cohen’s kappa κ ≈ 0.3, P < 0.0001). Using revised thresholds found using receiver operating characteristic curves [NavX: CFE-Mean ≤ 84 ms, CFE-SD ≤ 47 ms; CARTO: ICL ≥ 4, ACI ≤ 82 ms, SCI ≤ 58 ms], NavX classified 45 %, while CARTO detected 42 % (κ ≈ 0.5, P < 0.0001). Our results show that CFAE target identification is dependent on the system and thresholds used by the electrophysiological study. The thresholds found in this work counterbalance the differences in automated CFAE classification performed by each system. This could facilitate comparisons of CFAE ablation outcomes guided by either NavX or CARTO in future works

Electrophysiological Substrates of Atrial Fibrillation: A Frequency Domain Study of Intra-cardiac Electrograms

The mechanisms responsible for maintenance of AF remain poorly understood. This thesis examines the frequency domain characteristics of AF in order to gain further insights into this arrhythmia. Through a series of studies involving patients undergoing catheter ablation for atrial fibrillation, intra-cardiac electrograms of AF were collected and analysed using Fast Fourier Transform to derive frequency domain parameters of dominant frequency (DF) and organization index (OI). It was found that intravenous flecainide reduced DF of AF, but only an associated increase in OI was predictive of successful return to sinus rhythm. In another study of patients having catheter ablation for persistent AF, a higher OI post-ablation was found to be associated with medium-term freedom of AF, suggesting that OI may be a useful guide to determine the extent of radiofrequency ablation needed. The effects of vagal blockade with atropine were also studied and compared with that of catheter ablation using a stepwise strategy of isolating the pulmonary veins, linear ablation and complex fractionated electrogram ablation, without deliberately targeting ganglionated plexi. This showed that atropine reduced DF and increased OI of AF electrograms, while decreasing mean RR intervals, standard deviation of RR intervals and 5th percentile of RR intervals. The directional changes of all the above parameters mirrored that of catheter ablation, suggesting that vagal blockade and catheter ablation not deliberately aimed at autonomic tissue can have similar effects on the frequency spectrum of AF, probably mediated through modulation of the autonomic tone. The relationship of regional DF and electrogram complexity as assessed by automated measurement of complex fractionated electrogram – mean (CFE-mean) were also compared, pre and post-ablation of the left atrium. There appeared to be only a modest correlation between the two and this was further weakened following ablation, suggesting that these are possibly separate substrate entities

Electrophysiological substrates of atrial fibrillation : a frequency domain study of intra-cardiac electrograms

The mechanisms responsible for maintenance of AF remain poorly understood. This thesis examines the frequency domain characteristics of AF in order to gain further insights into this arrhythmia. Through a series of studies involving patients undergoing catheter ablation for atrial fibrillation, intra-cardiac electrograms of AF were collected and analysed using Fast Fourier Transform to derive frequency domain parameters of dominant frequency (DF) and organization index (OI). It was found that intravenous flecainide reduced DF of AF, but only an associated increase in OI was predictive of successful return to sinus rhythm. In another study of patients having catheter ablation for persistent AF, a higher OI post-ablation was found to be associated with medium-term freedom of AF, suggesting that OI may be a useful guide to determine the extent of radiofrequency ablation needed. The effects of vagal blockade with atropine were also studied and compared with that of catheter ablation using a stepwise strategy of isolating the pulmonary veins, linear ablation and complex fractionated electrogram ablation, without deliberately targeting ganglionated plexi. This showed that atropine reduced DF and increased OI of AF electrograms, while decreasing mean RR intervals, standard deviation of RR intervals and 5th percentile of RR intervals. The directional changes of all the above parameters mirrored that of catheter ablation, suggesting that vagal blockade and catheter ablation not deliberately aimed at autonomic tissue can have similar effects on the frequency spectrum of AF, probably mediated through modulation of the autonomic tone. The relationship of regional DF and electrogram complexity as assessed by automated measurement of complex fractionated electrogram – mean (CFE-mean) were also compared, pre and post-ablation of the left atrium. There appeared to be only a modest correlation between the two and this was further weakened following ablation, suggesting that these are possibly separate substrate entities.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Relationship between the spectral characteristics of atrial fibrillation and atrial tachycardias that occur after catheter ablation of atrial fibrillation

We read with interest the study by Yoshida et al 1 in the January 2009 issue of Heart Rhythm. The authors demonstrated that there was often a spectral component in the baseline atrial fibrillation (AF) periodogram that matched the frequency of atrial tachycardia (AT) that occurred acutely during ablation (group I patients). In contrast, this finding was seen less often in AT occurring late after ablation in a separate group of patients (group II patients). The study used atrial electrograms from both coronary sinus (CS) electrodes and lead V 1 (after QRS subtraction) for analysis, but only the periodogram from the CS electrodes showed convincingly the more frequent presence of a spectral component matching the frequency of AT in group I patients. In the Discussion, the authors suggest that although lead V 1 is more indicative of global atrial depolarization than is a single CS electrode, it may be more representative of the right than the left atrium, quoting work by Dibs el al. 2 This observation was previously reported by Hsu et al. 3Because cavotricuspid isthmus–dependent atrial flutter accounted for 40% of the macroreentrant AT in group I patients, it would be interesting to see whether a matching spectral component was more readily seen in the periodogram from lead V 1 in this group of patients. The ablation approach used in the study included antral pulmonary vein isolation followed by ablation of complex fractionated atrial electrograms in the CS and the left and right atria. We wonder if the authors encountered any problems with signal analysis because ablation or isolation of the CS would impair the signals recorded by the CS electrode. Although group I and group II patients had similar degrees of reduction of dominant frequency of AF signals after ablation, it is interesting that none of the group II patients converted to AT despite undergoing a similar ablation strategy. This finding suggests a difference in AF substrate burden between the two groups that probably is reflected by the significantly longer duration of AF in group II patients