Cardiac implantable electronic devices are a safe and effective way of treating arrhythmias, with increasing number of implants as indications widen and, as more devices are used, subsequent increase in generator replacements1. ICD and pacemaker leads are conventionally placed in the right ventricle and right atrium with the leads coursing the subclavian vein and superior vena cava. However, in some cases, there can occur lead malposition, which remains underdiagnosed as patients can be asymptomatic and fluoroscopic guidance during implantation can be misleading2,3. Furthermore, lead thresholds are not always helpful in the diagnosis, as they can be perfectly normal during patient follow-up3,4, which was the case of our patient. As the ICD lead is expected to be implanted in the right ventricular apex, pacing is expected to produce a left bundle branck block pattern. As in the case of our patient, the presence of a paced RBBB pattern must rise suspicion of lead malposition. Sites reported to be associated with the pattern are left ventricular malposition, coronary sinus implantation, lead perforation and pseudo-RBBB even in right ventricular lead placement5,6. Chest radiography is routinely performed after lead placement, generally in order to rule out pneumothorax and malposition of the lead. A correctly implanted lead is expected to a right lateral course through the right atrium in posteroanterior view, with the lateral view showing anterior location of the lead tip. In our patient, radiography revealed more superior and to the left positioning on posteroanterior view, with lateral view showing a more posterior location of lead tip, suggesting lead malposition in the left ventricle. Two-dimensional transthoracic echocardiography is the imaging test of choice in order to confirm lead malposition, as it is a readily available exam quickly performed at bedside. Transoesophageal echocardiography, as performed in our case, can also accurately delineate the course of the lead especially at the level of the interatrial septum, elucidating if we are in the presence of a patent foramen ovale or other types of atrial septal defect.
Complications of left ventricular lead position include valvular damage and thromboembolic events7. A recent trial, ALternate Site Cardiac ResYNChronization (ALSYNC) study, aimed to evaluate the feasibility and safety of left ventricular endocardial pacing (LVEP) using a pacing lead implanted via pectoral access by an atrial transeptal lead delivery system8. Left ventricular endocardial pacing was successful in 118 cases, and all patients received effective anticoagulation with warfarin, with target INR range 2.5-3.5. A total of 5 patients had a post-procedure stroke, however, none of the events led to permanent disability as defined by Rankin class 3 or greater. However, thrombo-embolic episodes may occur in up to 40% of affected patients, at any time after the procedure2. Factors such as timing of implantation, adherent thrombus and age of patients can influence the management of these cases. If the diagnosis is made shortly after implantation, percutaneous lead extraction can reduce embolic events and need of lifelong anticoagulation, however, the procedure carries some risk of systemic embolization from lead manipulation, especially with laser sheaths9. In the patients where diagnosis is delayed, warfarin seems a reasonable option, as thromboembolic events were rare or absent in patients with INR in the range of 2.5-3.53,8. However, it does not address the problem of valvular trauma and increased lifelong anticoagulation complications. As such, percutaneous extraction may be considered because it is a definitive solution for the problem. Surgical lead extraction is also an option, especially if cardiac surgery is warranted.
In our case, as the patient underwent cardiac transplantation for reasons not related to lead malposition, lead extraction did not constitute a problem for patient management. However, if we had to extract the lead, it would probably prove problematic as the lead was implanted 5 years before.
When a paced RBBB pattern is seen in a patient with previous ICD implantation, lead malposition in the left ventricle should be suspected. ECG is a very useful diagnostic tool and should be performed while under pacing, if necessary forcing it with a magnet, in order to clarify the position of cardiac stimulation, paramount for clinical suspicion in our case. Chest radiography with posteroanterior and lateral views can also help with the diagnosis, showing an abnormal lead path. However, it can be insufficient because left ventricular position can be mistaken for coronary sinus position. Therefore, echocardiography is crucial to diagnose lead malposition and its complications, as a readily available diagnosis tool capable of locating lead position and following its course. Computed tomography scan may be needed when other exams fail to diagnose lead malposition and suspicion remains high10.