Discussion
Implantation of a pacemaker or defibrillator is the most common surgical procedure involving the heart. Single lead ICDs are used to prevent sudden cardiac death in patients at high risk of life-threatening cardiac arrhythmia by sensing and then delivering electric shock to restore normal cardiac rhythm. They are typically placed in the right ventricular cavity. However, 27% of all complications from ICD insertions are due to lead dislodgment or unsatisfactory position (4). The migration of a lead occurs in different ways, but passage is most commonly through an atrial septal defect (ASD) or patent foramen ovale. Although reported in various cases, misplacement of a lead in the left ventricle is uncommon, but can lead to dangerous thromboembolic (TE) events (5). TE events are the result of thrombus formation around the implantation site and can occur from days to years after implantation (4). Other complications of inadvertent placement of an ICD lead in the left ventricle are pericardial effusion, endocarditis, vascular damage, and peripheral arterial thrombosis (6).
Diagnosis of a misplaced lead in the left ventricle requires high index of suspicion and immediate action. A misplaced lead in the left ventricle creates a RBBB-pattern on an ECG and is often the most important tool in diagnosis (2, 3). Due to the similarity of this pattern with right ventricle dilatation, coronary pacing, or sinus pacing, a confirmatory test is typically used; with AP and lateral chest X-rays being the primary instrument. While a correctly placed lead is seen with a slight bowing at the right ventricle on an AP view, a misplaced lead is typically seen to the left and farther superior. On a lateral projection, a correctly placed ICD lead tip is located anteriorly, but a misplaced lead’s tip points posteriorly (3). As in our case, a transesophageal echocardiogram can show a pacemaker lead crossing from the right atrium to the left atrium, then through the mitral valve before settling in the left ventricle.
Management of an inadvertent left ventricle lead depends heavily on time after implantation. Early detection of a misplaced lead allows for lead extraction, reducing the risk for TE events and avoiding the need for lifelong anticoagulation (7). If diagnosis is delayed, however, the lead becomes fixed in the heart and anticoagulation is needed to avoid TE events. If the patient is young and healthy, surgical extraction can also be considered, but can lead to inadvertent puncture of the vein used to access the heart. While the safer option, leaving a pacing lead in, may also influence function of the aortic valve, leading to heart failure or cardiac perforation (8).