Kelvin C.K. Wong

High incidence of acute sub-clinical circumflex artery ‘injury’ following mitral isthmus ablation

AIMSnMitral isthmus (MI) ablation is technically challenging, requiring long endocardial ablation times and frequently coronary sinus (CS) ablation. The circumflex artery lies in the epicardium in close proximity to the CS and the mitral annulus and may potentially be injured during radiofrequency ablation.nnnMETHODS AND RESULTSnFifty-four patients underwent catheter ablation procedures that included MI ablation for treatment of atrial fibrillation. Irrigated ablation catheters were used with the following settings: endocardial surface (max power: 40/50 W at the annular end; max temperature: 48°C); CS (max power: 25/30 W; max temperature: 48°C). Coronary angiography was performed pre- and post-ablation and analysed by two cardiologists with quantitative coronary angiography. Mitral isthmus block was achieved in 89% of patients (60% required CS ablation). Fifteen patients (28%) had angiographic changes following ablation: eight had mid-circumflex narrowing only, one had circumflex and obtuse marginal (OM) artery narrowing, one had OM narrowing only, and five had distal circumflex occlusion/narrowing. Five patients had significant narrowing (50-84%), which resolved with intracoronary glycerine trinitrate. Fourteen (93%) of the patients with circumflex injury had CS ablation and a longer mean CS ablation time (5.0 ± 3.0 vs. 2.6 ± 3.3 min, P = 0.03). Patients with distal circumflex occlusion had significantly smaller vessel diameter (1.0 ± 0.1 vs. 2.1 ± 0.2 mm, P = 0.03). A shorter distance between the circumflex and the CS was also associated with circumflex injury (3.2 ± 1.9 vs. 5.6 ± 3.2 mm, P = 0.04). There were no electrocardiographic or echocardiographic abnormalities and no angina symptoms during follow-up.nnnCONCLUSIONnAcute sub-clinical circumflex injury following MI ablation is not uncommon. Ablation within the CS, proximity of the circumflex and the CS, and a small distal circumflex were risk factors for injury.

Balloon occlusion of the distal coronary sinus facilitates mitral isthmus ablation

BACKGROUNDnMitral isthmus ablation is challenging. Blood flow in the coronary sinus (CS) may act as a heat sink and reduce the efficacy of radiofrequency ablation.nnnOBJECTIVEnThis study investigates whether balloon occlusion of CS facilitates mitral isthmus ablation.nnnMETHODSnThis single-center, prospective, randomized controlled trial included patients undergoing ablation for atrial fibrillation. After circumferential pulmonary vein isolation and roof line ablation, mitral isthmus ablation was performed during left atrial appendage pacing using an irrigated ablation catheter (endocardium: maximum power: 40/50 W, maximum temperature: 48°C; CS: maximum power: 25/30 W, maximum temperature: 48°C). An air-filled 40 × 10-mm percutaneous transluminal angioplasty balloon (Opta Pro, Cordis Europa, LJ Roden, The Netherlands) was used to occlude the CS on the epicardial aspect of the ablation line. Left coronary and CS angiography were performed before and after the procedure.nnnRESULTSnForty-six patients were studied. The balloon was successfully positioned in the distal CS in 20 of 23 patients (87%). Mitral isthmus block was achieved in 41 of 46 patients (91%). According to intention-to-treat analysis, there was significant reduction in the need for epicardial CS ablation (48% vs. 83%, P = .01) in the CS occlusion group but no difference in acute success rate. Secondary analysis showed reduction in mean total ablation time (9.4 ± 5.5 vs. 13.3 ± 4.6 minutes, P <.02) and mean CS ablation time (1.5 ± 2.8 vs. 3.4 ± 2.7 minutes, P <.05) in patients who had CS occlusion.nnnCONCLUSIONnBalloon occlusion of the CS during mitral isthmus ablation is feasible and safe. It significantly reduces ablation time and the need for CS ablation to achieve mitral isthmus block. The results support the hypothesis that heat sink is one of the obstacles to successful mitral isthmus ablation.

Larger coronary sinus diameter predicts the need for epicardial delivery during mitral isthmus ablation

AIMSnMitral isthmus ablation is technically challenging, often requiring both endocardial and epicardial coronary sinus (CS) ablation. Blood flow in the CS and circumflex artery may act as a heat sink and reduce the efficacy of radiofrequency ablation. This study investigates how the CS and circumflex artery diameters affect mitral isthmus ablation.nnnMETHODS AND RESULTSnThirty-five patients underwent ablation for atrial fibrillation. Irrigated-tip catheters were used during mitral isthmus ablation with the following settings: endocardial surface (maximum power: 40-50 W at the annular end of line; maximum temperature: 48°C); CS (maximum power: 25-30 W; maximum temperature: 48°C). The absence of block after 10 min of endocardial ablation led to CS ablation for up to 5 min. If there was still no block, further ablation was at the discretion of the physician. Coronary angiography and CS venography were performed and analysed with quantitative coronary angiography. Mitral isthmus block was achieved in 31 patients (89%). Twenty-three patients (74%) required CS ablation to achieve block. These patients were found to have significantly larger CS diameters (6.5 ± 1.2 vs. 5.4 ± 0.5 mm, P< 0.02). Coronary sinus diameter >59 mm predicted the need for CS ablation (specificity: 100%; sensitivity: 78%). Coronary sinus diameter correlated significantly with total mitral isthmus ablation time (r = 0.52, P < 0.003) and CS ablation time (r = 0.59, P < 0.0005), whereas circumflex diameter did not.nnnCONCLUSIONnLarger-diameter CS is associated with a need for CS ablation during mitral isthmus ablation. Coronary sinus but not circumflex diameter was significantly correlated with total and CS ablation time, supporting the hypothesis that the CS but not the circumflex artery acts as a heat sink.

Mitral Isthmus Ablation Using Steerable Sheath and High Ablation Power: A Single Center Experience

Case Series of Mitral Isthmus Ablation.u2003Background: Mitral isthmus ablation is challenging. The use of steerable sheath and high ablation power may improve success rate.

Questionnaire survey of cardiologists' knowledge, attitudes, and guideline application of implantable cardioverter defibrillator therapy.

Introduction: There are little data on cardiologists’ knowledge and application of current implantable cardioverter defibrillator (ICD) guidelines, attitudes to risk, and how these may influence ICD prescription.

Inter- and intravein differences in cardiac output with cardiac resynchronization pacing using a multipolar LV pacing lead.

Quadripolar left ventricular pacing leads permit a variety of pacing configurations from different sites within a coronary vein. There may be advantages to selecting a specific pacing vector. This study examines whether the range of cardiac outputs obtained at cardiac resynchronization therapy (CRT) implantation is greater between different poles within a vein, or greater between two different veins.

Local activation times at the high posterior wall of the left atrium during left atrial appendage pacing predict roof line block with high specificity and sensitivity.

AIMSnEnsuring complete block after left atrial (LA) linear lesions is important as partial block may be pro-arrhythmic. Techniques to confirm roof line block may be time consuming and challenging and have not been well described. This study investigates whether local activation times (LAT) during left atrial appendage (LAA) pacing help in the assessment of roof line block.nnnMETHODS AND RESULTSnForty-five patients underwent ablation for atrial fibrillation (AF) including circumferential pulmonary vein isolation, roof, and mitral isthmus lines. Local activation times were measured at pre-defined points on the posterior wall and high anterior wall during LAA pacing at the following stages: (i) baseline; (ii) incomplete roof line; (iii) roof block; and (iv) roof and mitral isthmus block. Time from pacing at high posterior wall to LAA was also recorded at each stage. Receiver operator curve analyses were performed on different parameters to assess if they could confirm roof line block. There was a stepwise increase in mean high posterior wall LAT: 83 ± 16 ms (baseline); 105 ± 20 ms (incomplete roof block); 133 ± 26 ms (roof block), and 152 ± 35 ms (roof and MI block; one way analysis of variance, P< 0.0001). Increased LA diameter, amiodarone use, and adjunctive complex fractionated atrial electrogram ablation were associated with longer LATs. For patients with persistent AF, LAA to high posterior wall times of >133 ms, high posterior wall to LAA times of >125 ms and double potential >77 ms predict roof line block with high specificity and sensitivity especially if there was also mitral isthmus block.nnnCONCLUSIONnParameters derived from the measurement of LAT of the high posterior and anterior LA wall help guide the assessment of roof line block.

A Pacemaker Magnet Check Alone Is Sufficient for the Majority of Patients Postpacemaker Implant

Patients postpacemaker implant can undergo a full assessment by pacing system programmer (PSP) or a magnet check. The former takes longer, but provides more detailed information; a magnet‐mode assessment is faster, but provides only capture data in an asynchronous pacing mode. A magnet‐mode assessment alone may be sufficient in most cases, and current clinical practice varies considerably.

A case of difficult RV lead placement

A 65-year-old man with ischaemic cardiomyopathy (EF 23%), NYHA class II–III heart failure symptoms and ECG showing LBBB with QRS duration of 150u2005ms underwent implantation of a Cardiac Resynchronisation Therapy Defibrillator (CRTD). The procedure was uneventful, and the pacing threshold and R wave amplitude during testing of the active dual coil lead were satisfactory.nnFigurexa01 showed a PA fluoroscopic image (1A), 12-lead ECG recorded during pacing from the defibrillator lead (1B), and injury current recording from the pacing system analyser (1C). Where is …

143 Where's the block for primary prevention implantable cardioverter defibrillators?

Introduction The UK has one of the lowest Implantable Cardioverter Defibrillator (ICD) implant rates in the western world and the majority of implants are for secondary prevention. This study was designed to identify the stumbling blocks for potential primary prevention(PP) ICD recipients who might otherwise qualify for an ICD according to current UK NICE guidelines. Methods A search was performed on the Oxford Radcliffe Hospitals echocardiography and heart failure databases for pts with an Oxfordshire postcode who had documentation of left ventricular ejection fraction (LVEF) recorded in the calendar year 2007. Pts <18u2005yrs were excluded. The search criteria included LVEF <35%. In addition, the descriptive terms ‘severely impaired’ or ‘poor LVEF’ were taken to indicate LVEF <30% and the term moderate to severely impaired was taken as LVEF 30–35%. Medical notes were assessed for age, aetiology of heart disease, time from MI, 12 lead ECG QRS duration, evidence of NSVT, Holter or electophysiological studies (EPS), NYHA status, review by a cardiologist and ICD implanter. Results Three hundred nine pts with LVEF <35% were identified from a population of 3554 echo assessments and 1104 heart failure patients. The findings are summarised in Abstract 143 figure 1. 19.5% pts were deemed not suitable for a PP ICD. 6% pts had subsequent improvement in their LVEF to >35%. Wrong documentation was evident in 5.5% pts. Of the 44 (14%) non-IHD (outside of NICE PP guidelines) pts with LVEF <35%, 24/44 (54.5%) had PP ICDs, usually combined with CRT. Missing data constituted 6.4% of our study. 44% pts satisfied the MADIT 2 and NICE criteria for PP ICDs. Thirty eight per cent of those eligible already had an ICD implanted. Fourty three per cent of pts who meet the NICE criteria were not offered PP ICDs. Forty seven per cent of these pts had been reviewed by a General Cardiologist and 40% by a General Physician. Seventy three per cent of potential MADIT 1 pts did not undergo Holter monitoring±electrophysiological studies (EPS) although 57% of them were seen by a General Cardiologist and none were referred for EPS. Abstract 143 Figure 1 Primary prevention study 309 patients with LVEF <35%. Conclusions In the current study of all patients undergoing echocardiography in 2007, half of those with LVEF <35% fulfilled NICE guidelines for PP ICDs. Only 40% had seen a cardiologist and of those only 38% had been offered a PP ICD. Holter screening of potentially eligible pts is not being performed. The barriers to PP ICDs appear to be at the level of the General Physicians and General Cardiologist.