Detecting and managing device leads inadvertently placed in the left ventricle

POSTOPERATIVE DETECTION BY ECG

Careful evaluation of the 12-lead electrocardiogram during ventricular pacing is important for confirming correct lead placement. If ventricular pacing is absent, eg, if the device fires only if the natural heart rate drops below a set number and the heart happens to be firing on its own when you happen to be looking at it, programming the device to pace the right ventricle 10 beats per minute faster than the intrinsic heart rate usually suffices. Temporarily disabling atrial pacing and cardiac venous pacing in biventricular devices facilitates interpretation of the paced QRS complex.

Bundle branch block patterns

The typical morphology for paced events originating from the right ventricle has a left bundle branch block pattern, ie, a dominant S wave in leads V₁ and V₂.  Nevertheless, many patients with a safely placed lead in the right ventricle can also demonstrate right bundle branch morphology during pacing,⁶ ie, a dominant R wave in leads V₁ and V₂.

Reprinted from reference 6 with permission.

Klein et al⁷ reported on 8 patients who had features of right bundle branch block in leads V₁ and V₂ and noted that placing these leads 1 interspace lower eliminated the right bundle branch block appearance. The utility of this maneuver is demonstrated in Figure 1.

Almehairi et al⁸ demonstrated transition to a left bundle branch block-like pattern in V₁ in 14 of 26 patients after leads V₁ and V₂ were moved to the fifth intercostal space. Moving these leads to the sixth intercostal space produced a left bundle branch block-like pattern in all the remaining patients. Additional study is needed to validate this precordial mapping technique.⁹

Reprinted from reference 6 and reference 14 with permission.

Coman and Trohman⁶ developed an algorithm using Klein’s technique and simple biaxial data (Table 1). They excluded left ventricular pacing from the proximal and mid-septum. The 2 criteria of a frontal axis of 0° to –90° and precordial transition from a predominantly positive to a predominantly negative paced QRS complex by V₃ separated right ventricular septal pacing from all other forms of left ventricular pacing, including from the cardiac veins (sensitivity 86%, specificity 99% specificity, and positive predictive value 95%). A precordial transition at or before lead V₃ essentially ruled out inadvertent left ventricular pacing (Figure 2).⁹ In addition, criteria were established to distinguish 4 major areas of left ventricular endocardial pacing.⁶

Although the Coman and Trohman algorithm suggests that a frontal plane axis of −90° to –180° is specific for left ventricular pacing,⁶ other reports have identified this axis in the presence of true right ventricular pacing.^6,9–12 Therefore, Barold and Giudici⁹ argue that a frontal plane axis in the right superior quadrant has limited diagnostic value.

POSTOPERATIVE DETECTION BY CHEST RADIOGRAPHY

Adapted with permission from references 14 and 15.

The postoperative chest radiograph is important for identifying complications such as pneumothorax and hemothorax. It is also extremely valuable for identifying lead dislodgement or malposition.

A lead in the left ventricle may be a subtle finding on an anteroposterior or posteroanterior chest radiograph. The definitive view is the lateral projection, which is also true during intraoperative fluoroscopy.^13–15 The tip of a malpositioned left-ventricular lead is characteristically seen farther posterior (toward the spine) in the cardiac silhouette on the lateral view (Figure 3).² If the lead is properly positioned, the general direction of the middle to distal portion should be away from the spine.

ECHOCARDIOGRAPHY TO CONFIRM

Echocardiograms adapted with permission from reference 16; medical illustration by Joseph Pangrace.

Although an electrocardiogram and a lateral chest radiograph should suffice to detect inadvertent left ventricular lead placement, it is common to confirm the diagnosis with a 2-dimensional transthoracic or transesophageal echocardiogram (Figure 4).¹⁶

Two-dimensional echocardiography can help to confirm left ventricular placement via an atrial septal defect, patent foramen ovale, or perforation of the interventricular septum.^16,17

Three-dimensional echocardiography can facilitate cardiac venous lead placement and assess the impact of right ventricular lead placement on tricuspid valve function.^18,19 In one case report, 3-dimensional echocardiography provided a definitive diagnosis of interventricular septal perforation when findings on computed tomography (CT) were indeterminate.²⁰

CT AND MRI: LIMITED ROLES

When echocardiographic findings are equivocal, CT can help diagnose lead perforation. Electrocardiogram-triggered cardiac CT can help visualize lead positions and potential lead perforation. Unfortunately, the precise location of the lead tip (and the diagnosis) can be missed due to streaking (“star”) artifacts and acoustic shadowing from the metallic lead.^21–26 Because of these limitations, as well as radiation exposure and high costs, CT should be used sparingly, if at all, for diagnosing lead malposition.

Technological advances and the increasing use of magnetic resonance imaging (MRI) in clinical practice have led to the development of “MRI-conditional” cardiac implantable electronic devices (ie, safe for undergoing MRI), as well as more lenient regulation of MRI in patients with nonconditional devices.^27,28 Although the widely held opinion that patients with a pacemaker or implantable cardioverter defibrillator are not eligible to undergo MRI has largely been abandoned, it seems unlikely that cardiac MRI will become a pivotal tool in assessing lead malposition.