Discussion:
Suspicion should arise of lead malposition if there is a pacemaker derived right bundle branch block pattern on a 12-lead electrocardiogram instead of the typical left bundle branch block morphology1. Utilisation of the posterolateral and anterolateral projections can differentiate and provide further evidence that LV malposition may have occurred. Various reports have recommended or used TTE as an imaging modality if there is a suspicion of lead malposition which offers the ability to see the lead using the parasternal, apical and subcostal views2,1. A single centre study by Ohlow and colleagues (2016) concluded that 0.34% of device implants out of 2579 patients between 2007 and 2012 experienced lead malposition of which the leading cause was unusual thoracic anatomy, congenital heart disease and operator inexperience3. Patients with LV lead malposition are often asymptomatic until presenting with systemic thromboembolic related complications such as ischemic stroke4.
The incidence of cerebral embolic events have been reported as high as 37% in patients with LV lead malposition3. The most common cause of systemic emboli is thrombus or fibrosis formation on the lead or at the site of implantation. At present there is no clear recommendations on management of lead malposition with duration between implant and discovery of lead malposition often influencing treatment. Incidental findings of lead malposition are often managed with anticoagulation and antiplatelet therapy in the first instance with the consideration of percutaneous or surgical lead extraction if deemed appropriate2,1. As life-long anticoagulation with Warfarin with a target international nominal ratio of 2.5 – 3.5 has been advised in this population5, some papers have not supported the use of anticoagulation in isolation due to reports of patients with lead malposition presenting with an ischemic stroke after prophylactic anticoagulation6,7. Other serious complications associated with LV lead malposition include mitral valve leaflet perforation8, mitral regurgitation7 and endocarditis9which must be taken into consideration when discussing the benefits and risks of lead extraction. While lead repositioning is a potential treatment option, caution must be taken to ensure percutaneous lead extraction does not displace any material which has formed on the lead10. One strategy recently reported by Contractor and colleagues (2019) suggested that deploying an embolic protection device in the brachiocephalic and left carotid artery can be used to remove the risk of potential cerebral embolisation11. It is beneficial that the patient undergo a TTE and TOE prior to the procedure to identify the presence of mobile thrombus or fibrous material as seen within our case study which may increase the risk of embolisation during extraction12. The addition of three dimensional views during a standard TOE views (3DTOE) has been recognised as a useful technique to offer supplementary information of thrombus characteristics and mobility. The advantage of 3DTOE in addition to the already high spatial resolution and superior visualisation of cardiac anatomy seen in standard two-dimensional TOE offers high specificity and sensitivity when visualising presence of intra-cardiac thrombus including left atrial thrombi. A recent case-study recognised that the use of 3DTOE was beneficial when assessing a large LV apical thrombus when magnetic resonance imaging and computed tomography were not appropriate13. The ability to use offline reconstructive techniques assists operators to augment image quality while visualising any mobile components and its attachments to the surrounding cardiac structures of a suspected thrombus. Another advantage of using 3DTOE within this particular case-study was the high quality images of mitral valve anatomy which offers a better perspective than 2D imaging including good visualisation and size of all scallops and mitral valve geometry. The benefits of 3DTOE in this case study was the ability to observe the exact position of the lead crossing the mitral valve with the use of the ‘surgeons view’, to see if the position of the pacing lead was negatively impeding the behaviour and mobility of the mitral valve leaflets and the thrombus attached to the lead in the left atrium. While some studies have identified that right ventricular lead extraction is viable and safe option of lead extraction, only few publicised cases have demonstrated the safe removal of anomalous rhythm management leads seen in the LV13, 14. Recommendations provided by the heart rhythm society in 2009 discussing indications for lead extraction offered caution when considering LV percutaneous lead extraction with the heightened risk of thromboembolic stroke. Although, the review cautioned that surgical removal of anomalous transvenous leads is a class III indication and could be offered at the same time as other surgical interventions requiring cardiopulmonary bypass15. Based upon the results of the TEE our patient was offered anticoagulation and antiplatelet therapy in the short-term with the goal of percutaneous lead extraction. A TEE was repeated after six months of medical therapy which showed no evidence of a mass and the patient was consented for percutaneous lead extraction due to the patient’s co-morbidities making him high risk for surgery.