His bundle combined with deep septal left bundle branch area pacing for atrial fibrillation prior to atrioventricular node ablation.

Background: To mitigate the risk of dyssynchrony-induced cardiomyopathy, international guidelines advocate His bundle pacing (HBP) with a ventricular backup lead prior to atrioventricular node ablation in treatment-refractory atrial fibrillation and normal left ventricular ejection fraction. As a result of concerns with long-term pacing parameters associated with HBP, this case series reports an adopted strategy of HBP combined with deep septal left bundle branch area pacing (dsLBBAP) in this patient cohort, enabling intrapatient comparison of the two pacing methods. Methods and Results: Eight patients aged 72 ± 10 years (left ventricular ejection fraction 53 ± 4%) underwent successful combined HBP and dsLBBAP implant prior to AV node ablation. Intrinsic QRS duration was 118 ± 46 ms. When compared to dsLBBAP, HBP had lower sensed ventricular amplitude (2.4 ± 1.1 vs. 15 ± 5.3 V, p = .001) and lower lead impedance (522 ± 57 vs. 814 ± 171ohms, p = .02), but shorter paced QRS duration (101 ± 20 vs. 119 ± 17 ms, p = .02). HBP pacing threshold was 1.0 ± 0.6 V at 1 ms pulse width, and dsLBBAP pacing threshold was 0.5 ± 0.2 V at 0.4 ms pulse width. Five patients underwent cardiac CT showing adequate dsLBBAP ventricular septal penetration (8.6 ± 1.3 mm depth, 2.4 ± 0.5 mm distance from left ventricular septal wall). No complications occurred during a mean follow-up duration of 121 ± 92 days. Conclusions: Combined HBP and dsLBBAP pacing is a feasible approach as a pace and ablate strategy for atrial fibrillation refractory to medical therapy.

Risk Factors of Haematoma Formation Following Cardiac Implantable Electronic Device Procedures.

PURPOSE: A single-centre cohort of 2,100 adults who consecutively underwent cardiac implantable electronic device procedures were retrospectively analysed to identify and quantify risk factors of perioperative pocket haematoma formation. RESULTS: Dual antiplatelet therapy was significantly associated with increased odds of haematoma formation (OR 11.7 for aspirin and clopidogrel, OR 11.8 for aspirin and ticagrelor and OR 104 for aspirin and prasugrel, p<0.05) on multivariate binomial logistic regression analysis. Aspirin monotherapy was also associated with increased bleeding risk (OR 3.02, p<0.01). Direct oral anticoagulants and warfarin were also each associated with increased odds of haematoma formation although to a lesser extent than dual anti platelet therapy (DAPT). Amongst oral anticoagulants, apixaban was associated with the lowest bleeding risk (OR 2.59, p=0.03) whilst dabigatran was associated with the highest (OR 3.81, p=0.04). There was a significant incremental reduction in bleeding risk by 8% per 10x103/µL increase in platelet count. CONCLUSION: DAPT was associated with increased odds of pocket haematoma formation following cardiovascular implantable electronic device (CIED) procedure. This likelihood was higher than with oral anticoagulation therapy. Timely medication reconciliation of P2Y12 inhibitors according to guidelines is important to avoid post-procedural bleeding complications. Perioperative policies which account for the half-life of withheld anticoagulant agents may help reduce the haematoma risk.

Cardiac Society of Australia and New Zealand (CSANZ) Position Statement on the Follow-Up of Cardiovascular Implantable Electronic Devices 2022.

Recognising the need for a national approach for the recommended best practice for the follow-up of implanted cardiac rhythm devices to ensure patient safety, this document has been produced by the Cardiac Society of Australia and New Zealand (CSANZ). It draws on accepted practice standards and guidelines of international electrophysiology bodies. It lays out methodology, frequency, and content of follow-up, including remote monitoring; personnel, including physician, allied health, nursing and industry; paediatric and adult congenital heart patients; and special considerations including magnetic resonance imaging scanning, perioperative management, and hazard alerts.

Left bundle branch area pacing in congenitally corrected transposition of great arteries - The obvious choice?

Patients with congenitally corrected transposition of the great arteries (CCTGA) are susceptible to acquired atrioventricular conduction disease in early life. Emerging studies propose that conduction system pacing either by His bundle pacing or bundle branch pacing is advantageous in this population. The anatomical abnormality of CCTGA conveniently positions the left bundle branches on the easily accessible right ventricular septal side. We present a case of a young female CCTGA patient with exercise-induced heart block who received left bundle branch area pacing with the ventricular lead implanted at the conventional right ventricular septal approach without the need for 3-dimensional electroanatomical mapping.

Remote Device Interrogation Kiosks (ReDInK) - Pharmacy Kiosk Remote Testing of Pacemakers and Implantable Cardioverter-Defibrillators for Rural Victorians. A Novel Strategy to Tackle COVID-19.

BACKGROUND: In the era of COVID-19, travel restrictions and social distancing measures have changed the landscape for device interrogations of pacemakers and defibrillators for rural Victorians. Previously, device checks were performed infrequently in large volume, face-to-face rural clinics by visiting cardiologists and technicians. Access to remote areas and social distancing restrictions have made these clinics unfeasible to operate. The Cardiac Society of Australia and New Zealand (CSANZ) and Heart Rhythm Society (HRS) COVID-19 consensus statements have suggested the utilisation of remote monitoring to minimise the potential spread of COVID-19 infections between clinicians and high-risk patients. A novel solution to this challenge was the implementation of a remote device interrogation (RI) service located in two kiosks at two rural pharmacies. This service was termed Remote Device Interrogation Kiosks (ReDInK). AIM: This cross-sectional observational study aimed to describe the set-up process, safety and efficacy of RI and customer satisfaction of the ReDInK program. METHODS: Two-hundred-and-ninety-two (292) rurally located patients with implantable cardiac devices were identified via the cardiology department database. Of these, 101 (44%) were enrolled into the ReDInK program across two rurally located pharmacies between April and July 2020. RI was performed and download outcomes were reviewed. A customer satisfaction survey assessed attitudes towards the program and explored options of ongoing service application. RESULTS: Of 101 patients enrolled into ReDInK, 96 (95%) resulted in satisfactory device checks. Four (4) individuals failed-to-attend and one individual experienced technical download issues. Of the 96 satisfactory device checks, three required in-person follow-up for reasons including battery replacement, lead repositioning and in-person programming. No adverse events were reported. A satisfaction telephone survey was conducted with 81 (83%) participants enrolled in ReDInK. Seventy-one (71) individuals (88%) of those surveyed expressed satisfaction and 73 (90%) labelled the process as efficiently conducted. Sixty-nine (69) (85%) participants felt reassured that this service was established during the pandemic. However 47 (58%) participants reported they would still feel comfortable to undergo in-person reviews despite social distancing recommendations. CONCLUSIONS: With the COVID-19 pandemic posing restrictions to social distancing and reducing unnecessary in-person interaction, the ReDInK program emerges as an efficacious and safe solution for patients in rural Victoria. The program's widely positive reception and successful conduction in rural Victoria invites further opportunity for a wider application of similar programs, expanding its role to metropolitan areas.

Learning Curve and Initial Experience With Implementation of a His-Bundle Pacing Program in an Australian Setting.

BACKGROUND: His-bundle pacing (HBP) has emerged as a promising technique to avoid pacing complications associated with dyssynchrony from right ventricular pacing, but data are limited to experienced operators and centres. We aimed to evaluate the implementation and outcomes of an HBP program in an Australian setting. METHODS: Data were retrospectively collected on 140 consecutive HBP procedures attempted at three centres from March 2018 to September 2019. The cohort was divided into three groups (early: procedures 1-47, middle: 48-94, late: 95-140) to determine changes in procedural success in relation to operator experience. RESULTS: Median age was 76 years (IQR 68-80 yrs); 69% were male. Atrial fibrillation was present in 59%, left ventricular ejection fraction (LVEF) ≤40% in 25%, and left and right bundle branch blocks present in 23% and 16% respectively, and atrioventricular (AV) block was present in 26%. Overall procedural success was 87%, median implant threshold 0.8V@1 ms, and QRS duration improved in 64% of procedures. Procedural success (early 83%, middle 89%, late 89%, p=0.58) was not different, while median procedural time (early 98 mins, middle 83 mins, late 70 mins, p<0.001) improved across operator experience groups. Lower success rates were identified for patients with AV block (73% vs. 92%, p<0.01), a previous device (69% vs. 89%, p=0.02), moderate-severe TR (69% vs. 88%, p=0.04), and when right-sided access was required (25% vs. 89%, p<0.01). CONCLUSIONS: His-bundle pacing is a feasible procedure with continued improvement in procedural measures of success after an early learning period. The presence of AV block, a previous device, significant tricuspid regurgitation, or right-sided access may affect procedural success.

Cardiac rhythm management devices

BACKGROUND: The last decade has seen ongoing evolution and use of cardiac rhythm management devices, including pacemakers, cardiac resynchronisation therapy, implantable cardioverter defibrillators and loop recorders. General practitioners are increasingly involved in follow-up and management of patients with these devices. OBJECTIVE: The aim of this article is to provide an overview of different cardiac rhythm management devices, including their role, implant procedure, post-procedural care, potential complications and follow­up. We also include practical advice for patients regarding driving, exercise, sexual intimacy and precautions with regards to electromagnetic interference. DISCUSSION: Cardiac rhythm management devices perform many functions, including bradycardia pacing, monitoring for arrhythmias, cardiac resynchronisation for heart failure, defibrillation and anti-tachycardia pacing for tachyarrhythmias. Concerns regarding potential device-related complications should be discussed with the implanting physician. In the post-implant period, patients with cardiac rhythm management devices can expect to lead normal, active lives. However, caution must occasionally be exercised in certain situations, such as near appliances with electromagnetic interference. Future innovations will move away from transvenous leads to leadless designs with combinations of different components on a 'modular' basis according to the function required.

Effects of long-term ω-3 polyunsaturated fatty acid supplementation on paroxysmal atrial tachyarrhythmia burden in patients with implanted pacemakers: results from a prospective randomised study.

BACKGROUND: Sino-atrial node disease and aging increase AF risk. We investigated if long-term fish oil supplementation reduces paroxysmal atrial tachycardia/fibrillation (AT/AF) burden in patients aged ≥60 years with sinoatrial node disease and dual chamber pacemakers. METHODS: Following a run-in period of 6 months (p1) where AT/AF burden was logged,78 patients were randomised to control or fish oil group (total omega-3 6 g/d) and AT/AF burden evaluated after 6 months (p2; 39 controls, 39 fish oil) and 12 months (p3; 39 controls; 18 fish oil). A subset of 21 fish oil patients crossed over to controls in the final 6 months (crossover group). RESULTS: Median AT/AF burden increased significantly in controls (1.5%, 3.2%, 4.3%, P<.001) but not in fish oil patients at 6 months (1.4% to 2%, P=.46) or those continuing for 12 months (1.5%, 0.98%, 1%, P=.16). Time to first episode of AT/AF >1 min was not significantly different between the groups (P=.9). There was a rebound increase in AT/AF burden in p3 in cross over patients (2.2% to 5.8%, P=.01) reaching a level similar to controls (crossover vs. controls, 5.8% vs. 4.3%, P=.63) and higher than those who continued fish oil for 12 months (crossover vs. continued intake 5.8% vs. 1.2%, P=.02). Fish oil patients had shorter duration episodes of AT/AF with no difference in frequency compared to controls. CONCLUSION: Long-term fish oil supplementation did not suppress AT/AF burden but may have attenuated its temporal progression related to aging and sinus node disease.

Atrial electrophysiology is altered by acute hypercapnia but not hypoxemia: implications for promotion of atrial fibrillation in pulmonary disease and sleep apnea.

BACKGROUND: Chronic pulmonary disease and sleep apnea have been associated with the development of atrial fibrillation (AF). OBJECTIVE: The purpose of this study was to characterize the atrial electrical changes that occur with hypercapnia and hypoxemia and to determine their role in AF development. METHODS: Seventeen sheep (6 control, 5 hypercapnia, 6 hypoxemia) underwent open chest electrophysiologic evaluation under autonomic blockade. A 64-electrode endocardial basket catheter was positioned in the right atrium, and 2 x 128 electrode epicardial plaques were sutured to the right atrial and left atrial appendages to determine atrial refractoriness (effective refractory period [ERP]) at 9 sites and 5 cycle lengths, conduction time to fixed points on each plaque, and AF vulnerability. RESULTS: Hypercapnia was associated with a 152% lengthening of ERP from baseline and increased conduction time. ERPs rapidly returned to baseline, but recovery of conduction was delayed at least 117 +/- 24 minutes following resolution of hypercapnia. AF vulnerability was reduced during hypercapnia (with increased ERP) but increased significantly with subsequent return to eucapnia (when ERP normalized but conduction time remained prolonged). No significant changes in ERP, atrial conduction time, or AF vulnerability occurred in hypoxemic or control groups. CONCLUSION: Differential recovery of ERP and conduction that occurs following hypercapnia might account for the increased vulnerability to AF observed in the phase after return to eucapnia. This may explain in part the increased prevalence of AF in pulmonary disease and sleep apnea.

The role of chronic atrial stretch and atrial fibrillation on posterior left atrial wall conduction.

BACKGROUND: The posterior left atrium (LA) is involved in the initiation and maintenance of atrial fibrillation (AF). OBJECTIVE: The purpose of this study was to compare conduction patterns on the posterior LA in patients with mitral regurgitation (MR), with and without AF. METHODS: Epicardial mapping of the posterior LA was performed in 23 patients undergoing cardiac surgery. Patients were included in one of three groups: Group A-patients in sinus rhythm with normal left ventricular function undergoing coronary artery bypass grafting, Group B-patients in sinus rhythm with MR undergoing mitral valve surgery, or Group C-patients in persistent AF with MR undergoing mitral valve surgery. Conduction patterns, regional conduction velocity, conduction heterogeneity, conduction anisotropy, and complex fractionated atrial electrograms (CFAEs) were assessed. RESULTS: LA diameter was greater in patients in Groups C (57 +/- 4mm) and B (54 +/- 6mm) than in Group A (39 +/- 7 mm, P <0.01). Patients in Group C had a greater number of lines of conduction delay than Groups A and B (2.0 +/- 0.8 vs 1 +/- 0 and 1 +/- 0, P <0.05). The extent of conduction delay and conduction heterogeneity was greater in Group C than in Group B, which was greater than in Group A (P <0.05). The percentage of CFAEs that remained stable during AF was 61% +/- 17%. There was a significant correlation between CFAEs during AF and regions of slow conduction during pacing (R = 0.36, P <0.001). CONCLUSION: Patients with MR, LA enlargement, and AF have more extensive regions of conduction slowing in the posterior LA. Anatomically constant lines of conduction delay in this region lead to circuitous wavefront propagation. During persistent AF, fractionated electrograms in the posterior LA are distributed to regions demonstrating slow conduction, and the majority remain stable over time.

Fractionated atrial electrograms during sinus rhythm: relationship to age, voltage, and conduction velocity.

BACKGROUND: Fractionated atrial electrograms (CFAEs) have been implicated in the mechanism of atrial fibrillation (AF). The prevalence and distribution of CFAEs in normal populations have not been clearly defined. OBJECTIVE: This study sought to determine the influence of age on CFAEs and investigate the relationship between CFAEs and the underlying atrial substrate. METHODS: Twenty-one patients without structural heart disease underwent electroanatomic mapping of their right atrium (RA). Patients were categorized into 3 groups according to age: group A, patients <30 years (25.1 +/- 3.1 years, n = 7); group B, patients between 31 and 59 years (51.7 +/- 10.3 years, n = 6); group C, patients >60 years (66.9 +/- 7.7 years, n = 8). The proportion of points with CFAEs was analyzed for the high and low septal RA, high and low lateral RA, and high and low posterior RA. The mean atrial voltage and conduction velocity were assessed in each of these regions. RESULTS: The percentage of CFAEs was greater in group C (14.6% +/- 7.7%) than in group A (2.7% +/- 2.1%; P = 0.001). The percentage of CFAEs in group B (8.5% +/- 3.5%) was not significantly different from that in group A (P = 0.21) and group C (P = 0.14). The CFAEs were predominantly located in the posterior RA and high septal RA. There were significant correlations between the proportion of CFAEs and age (R = 0.72; P < 0.01), atrial voltage (R = -0.57; P < 0.01), and conduction velocity (R = -0.73; P < 0.001). CONCLUSION: CFAEs increase with age and occur in regions of low atrial voltage and slowed conduction. The distribution of CFAE is predominantly along the posterior and high septal RA, regions where there are marked changes in myocardial fiber orientation. This suggests that the underlying myocardial architecture is the main influence on electrogram morphology.

Prevalence of sleep disordered breathing in paroxysmal and persistent atrial fibrillation patients with normal left ventricular function.

AIMS: Recent studies have suggested an emerging link between sleep apnoea and atrial fibrillation (AF). These studies included patients with reduced left ventricular (LV) function which may cause both AF and sleep disordered breathing (SDB). We examined the prevalence of SDB in a population of patients with AF and normal LV function. METHODS AND RESULTS: Ninety patients with paroxysmal or persistent AF and 45 controls were prospectively enrolled and matched 2:1 for age (AF 56 +/- 12 years; controls 54 +/- 11years) and sex. All patients had normal LV function. SDB was diagnosed using all-night portable polysomnography. Apnoea-hypopnoea index (AHI) in AF patients was higher than in controls (23.19 +/- 19.26 vs. 14.66 +/- 12.43, P = 0.01). The proportion with significant SDB (AHI > 15) was also greater in AF patients (62 vs. 38%, P = 0.01). After adjustment for relevant covariates, the odds ratio for the association between AF and SDB (AHI > 15) was 3.04 (95% CI 1.24-7.46, P = 0.02). The paroxysmal AF group was classified as either 'low-frequency AF' (< or =6) or 'high-frequency AF' (>6) episodes in the past year. High-frequency AF was associated with a higher prevalence (75 vs. 43%, P = 0.012) and severity (mean AHI 28.08 +/- 22.94 vs. 16.69 +/- 15.06, P = 0.028) of SDB when compared with those with low-frequency AF. CONCLUSION: A high prevalence of SDB is found in relatively young patients with both paroxysmal and persistent AF with normal LV function. This AF population warrants careful consideration for the presence of SDB.

Anatomically determined functional conduction delay in the posterior left atrium relationship to structural heart disease.

OBJECTIVES: This study sought to characterize the conduction properties of the posterior left atrium (PLA) in patients with different forms of structural heart disease undergoing cardiac surgery. BACKGROUND: The PLA plays an important role in the initiation and maintenance of atrial fibrillation. METHODS: This study included 34 patients having elective cardiac surgery. There were 4 groups of patients: normal left ventricular (LV) function (coronary artery bypass grafting [CABG]); severe LV dysfunction (LVF/CABG); severe mitral regurgitation (MR); severe aortic stenosis (AS). Epicardial mapping of the PLA was performed in sinus rhythm and during differential pacing. Activation patterns, regional conduction velocity (CV), conduction heterogeneity, anisotropy, and total plaque activation time (TAT) were assessed. RESULTS: Left atrial size in patients with LVF/CABG (47 +/- 7 mm) and MR (54 +/- 6 mm) was larger than patients with CABG (39 +/- 7 mm) and AS (42 +/- 6 mm; p < 0.05). During pacing, all patients developed a vertical line of conduction delay running between the pulmonary veins. The extent of this conduction delay was greater in patients with LVF/CABG and MR than patients with AS and CABG (p < 0.05). Conduction heterogeneity, anisotropy, and TAT were greater in patients with LVF/CABG and MR than patients with CABG (p < 0.05). These changes resulted in circuitous wave front propagation. CONCLUSIONS: There is a line of functional conduction delay in a consistent anatomical location in the PLA in patients with structural heart disease. This is most marked in conditions associated with significant chronic atrial enlargement and leads to circuitous wave front propagation, suggesting a potential role in arrhythmogenesis.

The right ventricular outflow tract: a comparative study of septal, anterior wall, and free wall pacing.

BACKGROUND: There is marked heterogeneity in right ventricular outflow tract (RVOT) pacemaker lead placement using conventional leads. As a result, we have sought to identify a reproducible way of placing a ventricular lead onto the RVOT septum. METHODS AND RESULTS: A major determinant is the shape of the stylet used to deliver the active-fixation lead. We compared stylet shapes and configurations in patients who initially had a ventricular lead placed onto the anterior or free wall of the RVOT and then had the lead repositioned onto the septum. All leads were loaded with a stylet fashioned with a distal primary curve to facilitate delivery of the lead to the pulmonary artery, then using a pullback technique the lead was retracted to the RVOT. All lead placements were confirmed by fluoroscopy and electrocardiography. Anterior or free wall placement was achieved by the stylet having either the standard curve or an added distal anterior angulation. In contrast, septal lead positioning was uniformly achieved by a distal posterior angulation of the curved stylet. This difference in tip shape was highly predictive for septal placement (P < 0.001). With septal pacing, a narrower QRS duration was noted, compared to anterior or free wall pacing (136 vs 155 ms, P < 0.001). All pacing parameters were within acceptable limits. CONCLUSION: Using appropriately shaped stylets, pacing leads can now be placed into specific positions within the RVOT and in particular septal pacing can be reliably and reproducibly achieved. This is an important step in the standardization of lead placement in the RVOT.

The right ventricular outflow tract: the road to septal pacing.

BACKGROUND: Pacing from the right ventricular apex is associated with long-term adverse effects on left ventricular function. This has fuelled interest in alternative pacing sites, especially the septal aspect of the right ventricular outflow tract (RVOT). However, it is a common perception that septal RVOT pacing is difficult to achieve. METHODS AND RESULTS: In this article, we will review the anatomy of the RVOT and discuss the importance of standard radiographic views and the 12-lead electrocardiogram in aiding lead placement. We will also describe a method utilizing a novel stylet shape, whereby a conventional active-fixation, stylet-driven lead can be easily and reliably deployed onto the RVOT septum.

Focal atrial tachycardias arising from the right atrial appendage: electrocardiographic and electrophysiologic characteristics and radiofrequency ablation.

OBJECTIVE: To characterize the electrocardiographic and electrophysiological features and frequency of focal atrial tachycardia (AT) originating from the right atrial appendage (RAA). BACKGROUND: The RAA has been described as a site of origin of AT, but detailed characterization of these tachycardias is limited. METHODS: Ten patients (3.8%) of 261 undergoing radiofrequency ablation (RFA) for focal AT are reported. Endocardial activation maps (EAM) were recorded from catheters at the CS (10 pole), tricuspid annulus (20 pole Halo catheter), and His positions. P waves were classified as negative, positive, isoelectric, or biphasic. RESULTS: The mean age was 39 +/- 20 years, nine males, with symptoms for 4.1 +/- 5.1 years. Tachycardia was incessant in seven patients, spontaneous in one patient, and induced by programmed extrastimuli in two patients. These foci had a characteristic P wave morphology. The P wave was negative in lead V(1) in all patients, becoming progressively positive across the precordial leads. The P waves in the inferior leads were low amplitude positive in the majority of patients. Earliest EAM activity occurred on the Halo catheter in all patients. Mean activation time at the successful RFA site =-38 +/- 15 msec. Irrigated catheters were used in six patients, due to difficulty achieving adequate power. RFA was acutely successful in all patients. Long-term success was achieved in all patients over a mean follow up of 8 +/- 7 months. CONCLUSIONS: The RAA is an uncommon site of origin for focal AT (3.8%). It can be suspected as a potential anatomic site of AT origin from the characteristic P wave and activation timing. Irrigated ablation catheters are often required for successful ablation. Long-term success was achieved with focal ablation in all patients.

Right ventricular outflow tract pacing: radiographic and electrocardiographic correlates of lead position.

OBJECTIVE: To characterize the pacing site in an unselected series of patients undergoing right ventricular outflow tract (RVOT) lead placement and investigate the role of the electrocardiogram (ECG) in predicting implantation. BACKGROUND: Right ventricular apical pacing is associated with long-term adverse effects on left ventricular function, fuelling interest in alternative pacing sites, especially the RVOT. Previous studies have been conflicting, possibly due to poor definition of pacing site within the RVOT. METHODS: In 150 patients undergoing pacemaker implantation, implanters were asked to place the lead in the RVOT. Radiographs were performed in the antero-posterior (AP) and 40 degrees right and left anterior-oblique projections post procedure. Fifty-six had left lateral radiographs. Lead position was categorized using AP/RAO (right anterior oblique) to confirm RVOT placement and left anterior oblique to distinguish free wall from septum. A 12-lead ECG was performed during ventricular pacing. RESULTS: Leads were below the RVOT in 18. Of the remaining 132, the majority (94%) were in the inferior/low RVOT. Eighty-one out of 132 were septal and 51 free wall. Septal sites were associated with shorter QRS duration (134 ms vs 143 ms, P < 0.02). Free wall sites displayed more frequent notching of the inferior leads (P < 0.01). A negative deflection in lead I provided a positive predictive value of 90% for septal sites. In those with lateral radiographs, a posteriorly projected lead was 100% specific for septal placement. CONCLUSIONS: This study demonstrates the heterogeneity of lead placement within the RVOT. Septal and free wall sites display characteristic ECG patterns which may be used to aid placement. The left lateral radiograph is useful in confirming a true septal location.