Assessment of optimal thresholds for ventricular scar substrate characterization using the high density grid multipolar mapping catheter

Funding Acknowledgements

Type of funding sources: None.

Background

Voltage thresholds for ventricular scar definition are based on historic data collected using catheters with widely spaced bipoles in the absence of contact force. Modern multipolar mapping catheters employ smaller electrodes and interelectrode spacing that theoretically allows for mapping with increased resolution and reduced far-field electrogram (EGM) component. Despite the advancement in technology, historic cut-offs of <0.5mV for dense scar and 0.5-1.5mV for scar borderzone continue to be used in contemporary electrophysiology.

Purpose

We aimed to assess the optimal voltage cut-offs for ventricular scar substrate characterization using the HD Grid multipolar mapping catheter. Voltage cut-offs were assessed against cardiac MRI derived scar. We compared optimal voltage cut-offs using conventional bipolar sampling, the Best Duplicate Algorithm and with the HD wave solution plus best duplicate algorithm on.

Methods

A multicentre study of twenty patients undergoing VT ablation was conducted. Substrate mapping was performed using the high-density HD-grid multipolar mapping catheter. Bipolar voltage maps were co-registered with cardiac MRI obtained prior to the procedure to assess the voltage characteristics of scar defined by cardiac MRI (CMR) (Figure 1). Pre-procedure contrast enhanced CMR data were analysed using ADAS software (Galgo medical). Data points were collected in regions of scar during (1) HD wave mapping with best duplicate algorithm on(Waveon), (2) Mapping with HD wave off and best duplicate on (Waveoff) and (3) with conventional bipolar mapping (Alloff).

Results

The median bipolar voltage for regions of dense CMR scar using (Waveon) HD wave solution and best duplicate algorithm was 0.27mV (IQR 0.14 – 0.46). The median voltage with (Waveoff) HD wave off was 0.29mV (0.15 – 0.45). The median voltage with (Alloff) HD wave off and best duplicate off was 0.32mV (0.19 – 0.5). ROC analysis using AUC suggested the optimal cut-off for endocardial dense scar using (Waveon) HD wave mapping and best duplicate algorithm was 0.30mV (sensitivity: 69.6%, specificity: 60.74%), (Waveoff) cut-off with the best duplicate and without the HD wave mapping was 0.34mV (sensitivity: 69.78%, specificity: 64.46%) and (Alloff) without wave mapping or best duplication was 0.36mV (sensitivity: 84%, specificity: 52%) Figure 2.

Conclusion

Ventricular substrate characterization with newer mapping technology using narrow electrode spacing and smaller electrode size suggests that traditional voltage cut-offs may need revision for delineation of scar characteristics. Additionally, the ability to repeat sample in a region to obtain the best signal (Best Duplicate), and the ability to obviate the effect of wavefront direction using the HD wave solution omnipolar technology, may further increase the fidelity of scar characterization. This has important implications for mapping VT and characterizing channels in order to identify VT circuits.

Utilising the pericardial CO2 insufflation technique to facilitate endo-epicardial AF ablation, achieving linear radiofrequency lesion sets, for persistent atrial fibrillation

Funding Acknowledgements

Type of funding sources: None.

Background

High rates of persistent atrial fibrillation (PsAF) recurrence have been attributed to conduction gaps, non-transmural linear lesion sets and epicardial substrate. Hybrid thorascopic endo-epicardial AF ablation has been shown to reduce PsAF recurrence when compared to endocardial ablation alone, however with higher complication rates.

Aim

We propose that the percutaneous pericardial CO2 insufflation technique to access the pericardial space can be safely and effectively used for epicardial mapping and ablation of the left atrium (LA).

Methods

In a single centre, 15 patients with PsAF (6 with longstanding PsAF) and previous pulmonary vein isolation (PVI), underwent concurrent endo-epicardial AF ablation, using the subxiphoid percutaneous pericardial CO2 insufflation technique, whilst on uninterrupted anticoagulation. Endo-epicardial geometry and bipolar voltage maps were undertaken, and endocardial LA ablation performed comprising a roof, inferior and anterior mitral line (AML) (target LSI 5 for the inferior line and 6 on the roof and AML). If required, additional epicardial ablation was undertaken to establish PVI and linear lesion block.

Results

Epicardial access was achieved in all patients without acute bleeding complication. Epicardial mapping of the LA, in both transverse and oblique pericardial sinuses, was successful in all patients (Figure 1A, B). Excluding one roof line, all other linear lesions were blocked (44/45). Endocardial ablation alone achieved block in 67% (10 of 15) of roof lines, 87% (13 of 15) of inferior lines and 27% (4 of 15) of AMLs despite extensive endocardial ablation. Of AMLs requiring epicardial ablation, in 91% (10/11) block was achieved with ablation on the upper third of AML via the transverse sinus (Figure 1C). Epicardial ablation directly on the roof line via the transverse sinus was required to achieve block in 3 cases, and block achieved remotely on the upper third of the AML in another. Epicardial ablation on the mid inferior line was required in 2 cases to achieve block. Six patients had arrhythmia recurrence during the blanking period with 5 patients requiring DCCV and 1 patient chemically cardioverting. With a mean follow up time of 225 days, 2 patients have had paroxysmal self-terminating episodes of atrial arrhythmia with all patients off anti-arrhythmic medication.

Conclusion

Use of the subxiphoid percutaneous pericardial CO2 insufflation technique to achieve epicardial access for LA mapping and ablation is feasible and safe whilst on uninterrupted anticoagulation. Limited success in ablation for PsAF beyond PVI may be due to difficulty in creating trans-mural linear lesions. Epicardial ablation can be safely performed to achieve linear block in the roof, anterior and inferior LA. Epicardial fibrous structures such as the septopulmonary bundle and Bachmann’s bundle likely contribute to difficulty blocking roof lines and AMLs endocardially.

The evaluation of pulmonary vein isolation and wide-area left atrial ablation to treat atrial fibrillation in patients with implanted permanent pacemakers: the Previously Paced Pulmonary Vein Isolation Study

BACKGROUND

The practise of catheter ablation for atrial fibrillation (AF) is increasing rapidly and is recommended as the treatment of choice in many patient subgroups. At present, the efficacy of this procedure has been assessed by means of electrocardiographic recording, intermittent Holter monitoring and evaluation of patient symptoms. We sought to evaluate the true efficacy of this procedure in patients with sophisticated permanent pacemakers capable of continuous long-term cardiac rhythm monitoring.

METHODS

Twenty-five patients (aged 63.7 (9.4), 20 men), seven with persistent AF and 18 with prolonged paroxysmal AF, underwent a mean of 1.7 AF ablation procedures. All the patients had previously been implanted with a pacemaker or atrial defibrillator device. Data were downloaded from the device Holter before catheter ablation and at 2, 4, 6 and 8 months postprocedure(s). The primary outcome measure was AF burden. The secondary outcomes were patient symptom and quality-of-life measures.

RESULTS

Initial AF burden was 43.8 (35.5)%. After catheter ablation(s), this was significantly reduced at 2 months to 23.8 (35.4)% (p=0.023), at 4 months to 21.4 (34.1)% (p=0.008), at 6 months to 14.5 (28.1)% (p=0.002) and at 8 months to 15.0 (29.4%) (p=0.003). Only nine (36%) of 25 patients demonstrated no recurrence of arrhythmia during follow-up completion, consistent with a long-term cure. Quality-of-life indices showed significant improvement after ablation.

CONCLUSIONS

Catheter ablation for AF significantly improves patient symptoms and reduces AF burden after long-term beat-to-beat monitoring by implanted cardiac pacemaker and defibrillator devices. However, AF recurrence is common after these procedures.

A randomised controlled trial comparing StarClose and AngioSeal vascular closure devices in a district general hospital--the SCOAST study

AIMS

AngioSeal and StarClose are vascular closure devices (VCDs) that can be used following cardiac catheterisation via the femoral artery to achieve haemostasis. Both devices have been demonstrated to be superior to conventional manual pressure, which reduce time to haemostasis and time to patient ambulation. We sought to compare these devices in a prospective, randomised trial.

METHODS

Patients undergoing elective coronary angiography were randomised to receive either AngioSeal VIP or StarClose VCD with immediate postprocedure mobilisation. Bruising was recorded at 30 min, 60 min and at 1 week postprocedure. Patient satisfaction surveys were taken at 1 h and 1 week postprocedure. Complications for both groups were compared.

RESULTS

Four hundred and one patients were included. Arteriotomy closure was achieved in 144 of 208 (69.2%) patients randomised to AngioSeal and 134 of 193 (69.3%) patients randomised to StarClose (p = ns). There was no significant bruising in either group at either 30 or 60 min postprocedure. However, at 1 week, there was significantly more bruising in the AngioSeal group than the StarClose group (63.1 vs. 38.5cm2, p = 0.02). Patient satisfaction and pain perception with the procedure at closure were not significantly different between the groups. Deployment success and instant mobilisation rates were significantly lower for junior, as compared with senior, operators.

CONCLUSION

Achievement of haemostasis is similar with both AngioSeal and StarClose. The StarClose vascular closure device results in significantly less bruising at 1 week postprocedure as compared with AngioSeal, with no significant differences in complication rates. Patients' pain perception and satisfaction are similar with both VCDs.