Edward Keelan

Contemporary management of and outcomes from cardiac device related infections

AIMS To describe the incidence and management of cardiac device infection. Infection is a serious, potentially fatal complication of device implantation. The numbers of device implants and infections are rising. Optimal care of device infection is not well defined. METHODS AND RESULTS We retrospectively identified cases of device infection at our institution between 2000 and 2007 by multiple source record review, and active surveillance. Device infection was related to demographics, clinical, and procedural characteristics. Descriptive analysis was performed. From 2000 to 2007, a total of 2029 permanent pacemakers and 1076 biventricular/implantable cardioverter-defibrillators (ICDs) or ICDs were implanted. Thirty-nine cases of confirmed device infections were identified--27 pacemaker and 12 bivent/ICD or ICD infections, giving an infection rate of 1.25%. Median time from implant or revision to presentation was 150 days (range 2915 days, IQR25% 35-IQR75% 731). Ninety percent of patients presented with generator-site infections. The most common organism was methicillin-sensitive Staphylococcus aureus (30.8%), followed by coagulase negative Staphylococcus (20.5%). Complete device extraction occurred in 82%. Of these, none had relapse, and mortality was 7.4% (n = 2/27). With partial removal or conservative therapy (n = 13), relapse occurred in 67% (n = 8/12), with mortality of 8.4% (n = 1/12). Median duration of antibiotics was 42 days (range 47 days, IQR25% 28-IQR75% 42 days). Re-implantation of a new device occurred in 54%, at a median of 28 days (range 73 days, IQR25% 8.5-IQR75% 35 days). Methicillin-Resistant Staphylococcus Aureus infection predicted mortality (P < 0.004, RR 37, 95% CI 5.3-250). Median follow-up was 36 months. CONCLUSION Cardiac device infection is a rare complication, with significant morbidity and mortality. Complete hardware removal with appropriate duration of antimicrobial therapy results in the best outcomes for patients.

Family-based cardiac screening in relatives of victims of sudden arrhythmic death syndrome

AIMS Sudden arrhythmic death syndrome (SADS) occurs when a person suffers a sudden, unexpected death, with no cause found at postmortem examination. We aimed to describe the cardiac screening outcomes in a population of relatives of SADS victims METHODS AND RESULTS Prospective and retrospective cohort study of consecutive families attending the Family Heart Screening clinic at the Mater Misericordiae Hospital in Dublin, Ireland, from January 2007 to September 2011. Family members of SADS victims underwent a standard screening protocol. Adjunct clinical and postmortem information was sought on the proband. Families who had an existing diagnosis, or where the proband had epilepsy, were excluded. Of 115 families identified, 73 were found to fit inclusion criteria and were retained for analysis, with data available on 262 relatives. Over half of the screened family members were female, and the mean age was 38.6 years (standard deviation 15.6). In 22 of 73 families (30%), and 36 of 262 family members (13.7%), a potentially inheritable cause of SADS was detected. Of the population screened, 32 patients (12.2%) were treated with medication, and 5 (1.9%) have received implantable cardiac defibrillators. Of the five families with long QT syndrome (LQTS) who had a pathogenic gene mutation identified, three carried two such mutations. CONCLUSION In keeping with international estimates, 30% of families of SADS victims were found to have a potentially inherited cardiac disease. The most common positive finding was LQTS. Advances in postmortem standards and genetic studies may assist in achieving more diagnoses in these families.

Cardiac MRI in Arrhythmogenic Right Ventricular Cardiomyopathy

OBJECTIVE Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a cause of sudden cardiac death in otherwise healthy young adults. This article outlines the spectrum of MRI findings in ARVC using a combination of static and cine images. CONCLUSION The detection of right ventricular enlargement, fatty infiltration, fibrosis, and wall motion abnormalities at MRI is useful in the diagnosis of ARVC.

First experience with zero-fluoroscopic ablation for supraventricular tachycardias using a novel impedance and magnetic-field-based mapping system

AimsZero- and near-zero-fluoroscopic ablation techniques reduce the harmful effects of ionizing radiation during invasive electrophysiology procedures. We aimed to test the feasibility and safety of a zero-fluoroscopic strategy using a novel integrated magnetic and impedance-based electroanatomical mapping system for radiofrequency ablation (RFA) of supraventricular tachycardias (SVTs).MethodsWe retrospectively studied 92 consecutive patients undergoing electrophysiology studies with/without RFA for supraventricular tachycardia (SVT) performed by a single operator at a single center. The first 42 (Group 1) underwent a conventional fluoroscopic-guided approach and the second 50 (Group 2) underwent a zero-fluoroscopic approach using the Ensite Precision™ 3-D magnetic and impedance-based mapping system (Abbott Inc).ResultsGroup 1 comprised 14 AV-nodal re-entrant tachycardia (AVNRT), 12 typical atrial flutter, 4 accessory pathway (AP), 2 atrial tachycardia (AT), and 9 diagnostic EP studies (EPS). Group 2 comprised 16 AVNRT, 17 atrial flutter, 6 AP, 3 AT, 2 AV-nodal ablations, and 7 EPS. A complete zero-fluoroscopic approach was achieved in 94% of Group 2 patients. All procedures were acutely successful, and no complications occurred. There was a significant reduction in fluoroscopy dose, dose area product, and time (p < 0.0001, for all), with no difference in procedure times. Ablation time for typical atrial flutter was shorter in Group 2 (p = 0.006).ConclusionsA zero-fluoroscopic strategy for diagnosis and treatment of SVTs using this novel 3D-electroanatomical mapping system is feasible in majority of patients, is safe, reduces ionizing radiation exposure, and does not compromise procedural times, success rates, or complication rates.

Automated ultra-high-density mapping of peri-sinus node premature atrial contractions

Catheter ablation of symptomatic premature atrial complexes (PACs) can be challenging, but the use of a 3D-electroanatomical mapping systems might improve accuracy [1]. Ultra-high-density (HD) mapping during routine atrial ablations leads to rapid and accurate generation of the electroanatomical maps [2]. We report on a case of a 72-year-old mildly overweight male patient (body mass index of 27.1 kg/ m2), with a history of coronary artery disease, percutaneous intervention to the left anterior descending artery and hypertension, who presented with high burden of symptomatic PACs (27% on Holter ECG monitor). Surface ECG P-wave morphology was almost identical to sinus p-waves, suggesting high right atrial or superior vena cava or right superior pulmonary vein origin (Fig. 1a). Continuous, automatic ultra-HD activation mapping of the left and right atrium (RA) during PACs was performed (Orion mapping catheter, Rhythmia, Boston Scientific). Typically, with this system, a second timing reference is sufficient to discriminate between atrial rhythms; however, this metric was insufficient due to the proximity of the PAC to the sinus node and the distance of the reference catheter. The PACs were automatically detected and discriminated from sinus rhythm using a strict ‘ECG Morphology Reference’ criterion (typically used for ventricular mapping), where a template of the PAC was compared with subsequent beats (Fig. 1b, PAC template—yellow, rejected sinus beat— white). Using this tool, the user can determine a tolerance level for the match of the template to the actual beat. The points are included in the map if they fulfil the match criteria and the electrograms are within 2 mm of the surface of the geometry. Moreover, in this case, ventricular beat overlap (to detect different PR intervals), respiratory, and motion filters were also used. In summary, the following settings were applied: 5 mm for propagation reference, 0.18 for ECG reference, 1 mm for motion, final 50% end expiration for respiration, 3 for tracking, and 23 ms for ventricular overlap beat metric. The system accurately identified the focus at the high lateral RA (panel C, signals from the mapping catheter in panel D and signals from ablation catheter in panel E), in close vicinity of the sinus node, where a single radiofrequency application (red dots) resulted in automaticity and immediate termination of PACs (43 °C and 30W limit, 30 s, white dots represent consolidation ablation points). The use of activation sequence mapping only would likely be inaccurate in this case. The patient was completely asymptomatic at the 6-month follow-up visit, with 0.8% PAC burden on the Holter. To our knowledge, this is the first known report using an ECG matching criterion with 3D mapping to automatically discriminate between sinus rhythm and a PAC focus, in such close proximity to the sinus node. Ultra-HD mapping allows accurate identification of the substrate for atrial arrhythmias [3–6]. The use of multiple discrimination algorithms, including ECG morphology analysis might be able to improve the accuracy of PAC mapping.

Isolation of the superior vena cava to block unidirectional exit conduction from the right-sided pulmonary veins during atrial fibrillation ablation

Unidirectional block is rare [1], but it might lead to failure of pulmonary vein isolation (PVI). During the ablation of a patient with persistent atrial fibrillation, the left-sided veins were easily isolated. Isolation of the right-sided pulmonary veins (PVs) resulted in entrance block (panel A, all electrograms recorded with GE CardioLab 6.9.5, 30and 500-Hz filters, 5000 gain, displayed at 200 mm/s; a SmartTouch ablation and a Lasso 2515 Nav eco variable loop diagnostic catheter with 2-6-2-mm spacing were used, Biosense Webster). High output pacing (12 mV/ 2 ms, >10 g contact) via the ablation catheter roving it around distally to the ablation line revealed conduction to the left atrium (LA, panel B), and far field right atrial (RA) capture could be excluded (panel C). Further ablation proximal to line at the high anterior-superior segment (where capture was demonstrated) failed to block conduction. Next, the superior vena cava (SVC) was isolated (panels D and E, 43 °C and 30-W limit, 10–15-s applications), which resulted in loss of exit conduction from the right sided PVs (panel F). We hypothesize that we were either able to reach the epicardial surface of the right superior pulmonary vein (RSPV) or ablate an epicardial PV-RA/LA pathway [2]. The close anatomical relationship of the RSPV to the SVC (6.4-mm endo-endocardial distance in this case on the 3D electroanatomical maps) might support that. Unidirectional conduction from the PVs can be easily identified by a simple pacing maneuver when validating PVI. Isolation of SVC might help achieve bidirectional block in the right superior pulmonary vein in selected cases.

51 Does degree of low amplitude atrial voltage correlate with poor left atrial function in atrial fibrillation

Background Patients with atrial fibrillation (AF) frequently have atrial scarring characterised by discrete regions of low voltage. Pre-existing left atrial scarring is an independent predictor of pulmonary vein isolation (PVI) failure. Novel mapping algorithms have also been developed to assess the degree of atrial fibrosis. This may be expressed as a percentage of the total left atrial (LA) volume mapped. In addition to the electrical remodelling seen, structural remodelling occurs, with dilatation and reduced function. The most accurate determinant of LA function is debated, but the most frequently used method is transmitral A Wave velocity on pulsed-wave Doppler. The relationship between LA function and electrical changes seen in AF has not been defined. Methods This was a single centre observational study. Left atrial voltage maps were created in patients undergoing PVI for the first time in the Mater Private Hospital between August 2016 and April 2017. LA voltage maps were initially created with a Lasso catheter with some further points taken with a Smarttouch ablation catheter (both Biosense Webster, Diamond Bar, California). Voltage greater than 0.5 mV was accepted as normal tissue and voltages < 0.2 mV scar. After creation of the voltage maps, the percentage scar was assessed using a novel computer algorithm (Biosense Webster). Pre-ablation echocardiograms were studied and the LA function was assessed by measuring the trans-mitral pulse wave Doppler. Assessments were only made in sinus rhythm. Results Out of 96 patients who had undergone PVI, only 24 were found to have had sinus rhythm on pre-procedural echo. The mean age was 63.5 (standard deviation or SD 10.6) years. 66% of the group were men. 58% had paroxysmal AF. The mean amplitude of the A-wave in the study was 0.61 (SD 0.16) ms-1. An average of 1269.7 (SD 857.0) mapping points were taken. The mean LA percentage scar was 25.1 (SD 20.3) %. Using linear regression, adjusted for age at time of procedure, there was a significant negative association between a wave (in ms-1) and % LA scar (Beta coefficient -72.44, 95% CI -122.99 to -21.88, p=0.007). Using pairwise correlation, the correlation coefficient between LA scar and A wave was -0.38, p=0.06. Abstract 51 Figure 1 Two-way scatterplot with fitted regression line between left atrial scar and transmitral A wave velocity. A wave measure in ms-1, LA scar expressed as a percentage Conclusion Our study found an inverse correlation between transmitral A wave and degree of left atrial scarring when LA function was adjusted for patient age, indicating that LA electrical remodelling as measure by percentage scar is associated with decreased LA function in patients with AF. However, there were only 24 patients in this study and ongoing research with more patients is warranted to further substantiate this.