Steven E. Williams

Cardiac magnetic resonance and electroanatomical mapping of acute and chronic atrial ablation injury: a histological validation study

AIMS To provide a comprehensive histopathological validation of cardiac magnetic resonance (CMR) and endocardial voltage mapping of acute and chronic atrial ablation injury. METHODS AND RESULTS 16 pigs underwent pre-ablation T2-weighted (T2W) and late gadolinium enhancement (LGE) CMR and high-density voltage mapping of the right atrium (RA) and both were repeated after intercaval linear radiofrequency ablation. Eight pigs were sacrificed following the procedure for pathological examination. A further eight pigs were recovered for 8 weeks, before chronic CMR, repeat RA voltage mapping and pathological examination. Signal intensity (SI) thresholds from 0 to 15 SD above a reference SI were used to segment the RA in CMR images and segmentations compared with real lesion volumes. The SI thresholds that best approximated histological volumes were 2.3 SD for LGE post-ablation, 14.5 SD for T2W post-ablation and 3.3 SD for LGE chronically. T2-weighted chronically always underestimated lesion volume. Acute histology showed transmural injury with coagulative necrosis. Chronic histology showed transmural fibrous scar. The mean voltage at the centre of the ablation line was 3.3 mV pre-ablation, 0.6 mV immediately post-ablation, and 0.3 mV chronically. CONCLUSION This study presents the first histopathological validation of CMR and endocardial voltage mapping to define acute and chronic atrial ablation injury, including SI thresholds that best match histological lesion volumes. An understanding of these thresholds may allow a more informed assessment of the underlying atrial substrate immediately after ablation and before repeat catheter ablation for atrial arrhythmias.

Quantitative Magnetic Resonance Imaging Analysis of the Relationship Between Contact Force and Left Atrial Scar Formation After Catheter Ablation of Atrial Fibrillation

Catheter contact force (CF) is an important determinant of radiofrequency (RF) lesion quality during pulmonary vein isolation (PVI). Late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) allows good visualization of ablation lesions.

Repeat Left Atrial Catheter Ablation: Cardiac Magnetic Resonance Prediction of Endocardial Voltage and Gaps in Ablation Lesion Sets

Background—Studies have reported an inverse relationship between late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) signal intensity and left atrial (LA) endocardial voltage after LA ablation. However, there is controversy regarding the reproducibility of atrial LGE CMR and its ability to identify gaps in ablation lesions. Using systematic and objective techniques, this study examines the correlation between atrial CMR and endocardial voltage. Methods and Results—Twenty patients who had previous ablation for atrial fibrillation and represented with paroxysmal atrial fibrillation or atrial tachycardia underwent preablation LGE CMR. During the ablation procedure, high-density point-by-point Carto voltage maps were acquired. Three-dimensional CMR reconstructions were registered with the Carto anatomies to allow comparison of voltage and LGE signal intensity. Signal intensities around the left and right pulmonary vein antra and along the LA roof and mitral lines on the CMR-segmented LA shells were extracted to examine differences between electrically isolated and reconnected lesions. There were a total of 6767 data points across the 20 patients. Only 119 (1.8%) of the points were ⩽0.05 mV. There was only a weak inverse correlation between either unipolar (r=−0.18) or bipolar (r=−0.17) voltage and LGE CMR signal intensities with low voltage occurring across a large range of signal intensities. Signal intensities were not statistically different for electrically isolated and reconnected lesions. Conclusions—This study demonstrates that there is only a weak point-by-point relationship between LGE CMR and endocardial voltage in patients undergoing repeat LA ablation. Using an objective method of assessing gaps in ablation lesions, LGE CMR is unable to reliably predict sites of electrical conduction.

Auditory verbal hallucinations and brain dysconnectivity in the perisylvian language network: A multimodal investigation

Neuroimaging studies of schizophrenia have indicated that the development of auditory verbal hallucinations (AVHs) is associated with altered structural and functional connectivity within the perisylvian language network. However, these studies focussed mainly on either structural or functional alterations in patients with chronic schizophrenia. Therefore, they were unable to examine the relationship between the 2 types of measures and could not establish whether the observed alterations would be expressed in the early stage of the illness. We used diffusion tensor imaging and functional magnetic resonance imaging to examine white matter integrity and functional connectivity within the left perisylvian language network of 46 individuals with an at risk mental state for psychosis or a first episode of the illness, including 28 who had developed AVH group and 18 who had not (nonauditory verbal hallucination [nAVH] group), and 22 healthy controls. Inferences were made at P < .05 (corrected). The nAVH group relative to healthy controls showed a reduction of both white matter integrity and functional connectivity as well as a disruption of the normal structure−function relationship along the fronto-temporal pathway. For all measures, the AVH group showed intermediate values between healthy controls and the nAVH group. These findings seem to suggest that, in the early stage of the disorder, a significant impairment of fronto-temporal connectivity is evident in patients who do not experience AVHs. This is consistent with the hypothesis that, whilst mild disruption of connectivity might still enable the emergence of AVHs, more severe alterations may prevent the occurrence of the hallucinatory experience.

Trends, indications and outcomes of cardiac implantable device system extraction: a single UK centre experience over the last decade

Background:  The rising number of device implantation has seen a parallel in the rising numbers of lead extraction. Herein we have analysed our experience in cardiac device and lead extraction in a single tertiary centre over the last decade.

Laser lead extraction to facilitate cardiac implantable electronic device upgrade and revision in the presence of central venous obstruction

Aims The number of procedures involving upgrade or revision of cardiac implantable electronic devices (CIEDs) is increasing and the risks of adding additional leads are significant. Central venous occlusion in patients with pre-existing devices is often asymptomatic and optimal management of such patients in need of device revision/upgrade is not clear. We sought to assess our use of laser lead extraction in overcoming venous obstruction. Methods and results Patients in need of device upgrade/revision underwent pre-procedure venography to assess venous patency. In patients with venous occlusion or stenosis severe enough to preclude passage of a hydrophilic guide wire, laser lead extraction with retention of the outer sheath in the vasculature was performed with the aim of maintaining a patent channel through which new leads could be implanted. Data were recorded on a dedicated database and patient outcomes were assessed. Between July 2004 and April 2012, laser lead extractions were performed in 71 patients scheduled for device upgrade/revision who had occluded or functionally obstructed venous anatomy. New leads were successfully implanted across the obstruction in 67 (94%) cases. There were two major complications (infection) and four minor complications with no peri-procedural mortality. Device follow-up was satisfactory in 65 (92%) cases with mean follow-up up to 26 ± 19 months. Conclusion Laser lead extraction is a safe and effective option when managing patients with central venous obstruction in need of CIED revision or upgrade.

Surface flattening of the human left atrium and proof-of-concept clinical applications

Surface flattening in medical imaging has seen widespread use in neurology and more recently in cardiology to describe the left ventricle using the bulls-eye plot. The method is particularly useful to standardize the display of functional information derived from medical imaging and catheter-based measurements. We hypothesized that a similar approach could be possible for the more complex shape of the left atrium (LA) and that the surface flattening could be useful for the management of patients with atrial fibrillation (AF). We implemented an existing surface mesh parameterization approach to flatten and unfold 3D LA models. Mapping errors going from 2D to 3D and the inverse were investigated both qualitatively and quantitatively using synthetic data of regular shapes and computer tomography scans of an anthropomorphic phantom. Testing of the approach was carried out using data from 14 patients undergoing ablation treatment for AF. 3D LA meshes were obtained from magnetic resonance imaging and electroanatomical mapping systems. These were unfolded using the developed approach and used to demonstrate proof-of-concept applications, such as the display of scar information, electrical information and catheter position. The work carried out shows that the unfolding of complex cardiac structures, such as the LA, is feasible and has several potential clinical uses for the management of patients with AF.

Percutaneous lead and system extraction in patients with cardiac resynchronization therapy (CRT) devices and coronary sinus leads.

Background:  Cardiac resynchronization therapy (CRT) device and coronary sinus (CS) lead extraction is required due to the occurrence of system infection, malfunction, or upgrade. Published series of CS lead extraction are limited by small sample sizes. We present a 10‐year experience of CRT device and CS lead extraction.

Comparison of delayed transvenous reimplantation and immediate surgical epicardial approach in pacing-dependent patients undergoing extraction of infected permanent pacemakers.

BACKGROUND Pacemaker infection in pacing-dependent patients is challenging. After extraction, temporary pacing usually is utilized before delayed reimplantation (after an appropriate course of antibiotics), resulting in prolonged hospital stays. A single combined procedure of epicardial (EPI) pacemaker implantation and system extraction may prevent this. OBJECTIVE The purpose of this study was to evaluate the feasibility and safety of these 2 approaches by comparing clinical outcome for both strategies over 1 year. METHODS In center 1, 80 consecutive pacemaker-dependent patients underwent extraction with an externalized pacemaker and delayed implantation on the contralateral side (ENDO group). In center 2, 80 consecutive patients had 2 epicardial ventricular leads surgically implanted with extraction of the infected pacemaker during the same procedure (EPI group). Patients were followed-up for 12 months. RESULTS One hundred sixty pacing-dependent patients were successfully implanted and extracted (ENDO group 71 ± 13 years vs EPI group 73 ± 14, P = NS). In the EPI group, 2 patients developed significant pericardial bleeding. In-hospital mortality was 0% in the ENDO group and 2.5% in the EPI group. Total hospitalization time was 15 ± 7 days in the ENDO group vs 9 ± 6 days in the EPI group (P <.001). At 1 year, no infection recurrences occurred in either group, and mortality was equal (5% in each group). Median 1-year pacing thresholds were lower in the ENDO vs the EPI group (0.8 ± 0.6 V vs 1.1 ± 0.6 V, P = .02). CONCLUSION The ENDO and EPI strategies had an excellent success rate and low risk of complications. A single procedure using surgical epicardial lead implantation was associated with a shorter duration of hospital stay.

The current practice and perception of cardiac implantable electronic device transvenous lead extraction in the UK.

AIMS The number of patients requiring an extraction of cardiac implantable electronic devices (CIEDs) is rising. Lead extraction of chronically implanted leads is a highly specialized procedure and the Heart Rhythm Society published a consensus document outlining best practice. We sought to ascertain the current practice and perception of lead extraction in the UK. METHODS AND RESULTS A prospective e-mail survey consisting of 21 questions was sent to members of Heart Rhythm UK. Key areas for exploration included case volume, settings for extraction procedures, levels of surgical support, preferred techniques, and the perceptions of difficulty, risk, morbidity, and mortality associated with lead extraction. Thirty responses were received giving a response rate of 9.3%. Eighty-three per cent of responders performed extractions regularly and of these 92% were electrophysiologists. Median number of cases performed per year was 13 (interquartile range 6-26). Fifty-six per cent performed <20 procedures per year. Eighty per cent of procedures were performed in the electrophysiology (EP) laboratory and of these 50% had no identifiable surgeon or operating theatre on standby. Mechanical dissection sheaths were the most widely used method of extraction after failure of manual traction (63%). The risk of minor complications was perceived to be 4% or less by the majority of respondents across the device range. The same measure for major complications and death was 2 and 1%, respectively. CONCLUSION Increased operator caseload and closer links between EP extractors and surgeons should be seen as achievable goals.