Elham Bidar

Indices of bipolar complex fractionated atrial electrograms correlate poorly with each other and atrial fibrillation substrate complexity

BACKGROUND The pathophysiological relevance of complex fractionated atrial electrograms (CFAE) in atrial fibrillation (AF) remains poorly understood. OBJECTIVE The aim of this study was to comprehensively investigate how bipolar CFAE correlates with unipolar electrogram fractionation and the underlying electrophysiological substrate of AF. METHODS Ten-second unipolar AF electrograms were recorded using a high-density electrode from the left atrium of 20 patients with AF (10 with persistent AF and 10 with paroxysmal AF) undergoing cardiac surgery. Semiautomated bipolar CFAE algorithms: complex fractionated electrogram-mean, interval confidence interval, continuous electrical activity, average complex interval, and shortest complex interval were evaluated against AF substrate complexity measures following fibrillation wave reconstruction derived from local unipolar activation time. The effect of interelectrode spacing and electrode orientation on bipolar CFAE was also examined. RESULTS All 5 semiautomated bipolar CFAE algorithms showed poor correlation with each other and AF substrate complexity measures (conduction velocity, number of waves or breakthroughs per AF cycle, and electrical dissociation). Bipolar CFAE also correlated poorly with fractionation index derived from unipolar electrograms. Increased interelectrode spacing resulted in an increase in bipolar CFAE detected except for the interval confidence interval algorithm. CFAE appears unaffected by bipolar electrode orientation (vertical vs horizontal). By contrast, unipolar fractionation index correlated well with AF substrate complexity measures and can be regarded as a marker for conduction block. CONCLUSION The lack of pathophysiological relevance of bipolar CFAE analysis may in part contribute to the divergent and limited success rates of catheter ablation strategies targeting CFAE.

Modalities and Effects of Left Ventricle Unloading on Extracorporeal Life support: a Review of the Current Literature

Veno‐arterial extracorporeal membrane oxygenation (V‐A ECMO) support is increasingly used in refractory cardiogenic shock and cardiac arrest, but is characterized by a rise in afterload of the left ventricle (LV) which may ultimately either further impair or delay cardiac contractility improvement. The aim of this study was to provide a comprehensive overview regarding the different LV venting techniques and results currently available in the literature.

Cost-effectiveness of ablation surgery in patients with atrial fibrillation undergoing cardiac surgery

This study was performed to assess the cost-effectiveness of concomitant ablation surgery (AS) compared to regular cardiac surgery in atrial fibrillation (AF) patients over a one-year follow-up. Cost analysis was performed from a societal perspective alongside a prospective, randomised, double-blinded, multicentre trial. One hundred and fifty patients with documented AF were randomly assigned to undergo cardiac surgery with or without AS. One hundred and thirty-two patients were included in the cost-effectiveness study. All costs (medical and non-medical) were measured during follow-up. Costs data were combined with quality adjusted life years (QALYs) to obtain the incremental costs per QALY. Total costs of the AS group were significantly higher compared to the regular cardiac surgery group [cost difference bootstrap: €4,724; 95% uncertainty interval (UI), €2,770-€6,678]. The bootstrapped difference in QALYs was not statistically significant (0.06; 95% UI: -0.024 to 0.14). The incremental cost-effectiveness ratio is €73,359 per QALY. The acceptability curve showed that, even in the case of a maximum threshold value of €80,000 per QALY gained, the probability of AS being more cost-effective than regular cardiac surgery did not reach beyond 50%. Concluding that concomitant AS in AF is not cost-effective after a one-year follow-up compared to regular cardiac surgery.

Application of phase coherence in assessment of spatial alignment of electrodes during simultaneous endocardial–epicardial direct contact mapping of atrial fibrillation

AIMS Mapping and interpretation of wave conduction patterns recorded during simultaneous mapping of the electrical activity on both endocardial and epicardial surfaces are challenging because of the difficulty of reconstruction of reciprocal alignment of electrodes in space. Here, we suggest a method to overcome this difficulty using a concept of maximized endo-epicardial phase coherence. METHODS AND RESULTS Endo-epicardial mapping was performed in six humans during induced atrial fibrillation (AF) in right atria using two sets of 8 × 8 electrode plaques. For each electrode, mean phase coherence (MPC) with all electrodes on the opposite side of the atrial wall was calculated. Localization error was defined as a distance between the directly opposing electrode and the electrode with the maximal MPC. Overall, there was a linear correlation between MPC and distance between electrodes with R(2) = 0.34. Localization error obtained for electrodes of the plaque in six patients resulted in a mean 2.3 ± 1.9 mm for 25 s electrogram segment length. Eighty-four per cent of the measurements resulted in error smaller than 3.4 mm. The duration of the recording used to compute MPC was negatively correlated with localization error; however, the effect reached plateau for segment durations longer than 15 s. CONCLUSION Application of the concept of maximized endo-epicardial phase coherence to electrograms during AF allows reconstruction of reciprocal alignment of the electrodes on the opposite side of the atrial wall. This approach may be especially useful in settings where the spatial position of endo- and epicardial electrodes for intracardiac mapping cannot otherwise be determined.

Far-field effect in unipolar electrograms recorded from epicardial and endocardial surface: Quantification of epi-endo dissociation during atrial Fibrillation in Humans

In this study we explore whether endo-epicardial dissociation during atrial fibrillation (AF) can explain origin of some of the far-field components in unipolar electrograms. To assess the number of far-field deflections in unipolar electrograms that have a source on the contralateral side of the atrial wall we used simultaneous endo-epicardial high-resolution contact mapping. 30s endo-epicardial electrograms were recorded using two 64 electrode arrays directly opposing each other, placed on the right atrial wall in 5 patients with persistent AF. For all far-field deflections that could not be explained by local activation within the same plane, we searched for a passing wavefront on the other side of the atrial wall. 74±3% of detected far-field deflections could be explained by activation on the same side of the atrial wall. Within the remaining deflections, 42±5% had a source in the activity taking place directly on the other side of the atrial wall. 15±3% of all detected far-fields were of unknown origin. High proportion of the far-field deflections detected using contact mapping during AF results from endo-epicardial dissociation may have an impact on proper annotation of local activity, and therefore on identification of conduction patterns. Calculating the number of far-field deflections in unipolar electrograms due to endo-epi dissociation may help to quantitatively describe transmural dissociation.