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Evaluation of intermittent capture in a patient who has undergone an urgent temporary transvenous pacemaker lead insertion

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Q1: Describe the ECG (fig 1; see p 431)

The post-procedure ECG shows paced rhythm with complete right bundle branch block morphology and right inferior axis shift (fig 1 below: RR’ complex in V1; QS complex in S1, aVL and V5; R in aVR and aVF). If one sees such an ECG pattern in a paced patient, then one must think of a malpositioned lead that stimulates the heart from the left ventricle.

Q2: What do you see in the fluoroscopic view (fig 2; see p 431)?

The fluoroscopic view taken after temporary pacemaker lead insertion clearly shows a malpositioned temporary pacemaker lead (fig 2 marked as B) in the coronary sinus and another lead in the right ventricle (fig 2 marked as A). The left anterior oblique view is especially important to locate and verify the course of the lead that goes to the left side of the heart. As is seen on the right anterior oblique view, the tip of the lead lies on the epicardial surface of the left ventricle. Because it is epicardially located on the left ventricle and unstably positioned, it might be responsible for inefficient and intermittent capture as well as for an elevated capture threshold. Subsequently, a second pacing lead (fig 2 marked as A) was inserted through the contralateral femoral vein in the right ventricle and the malpositioned lead was pulled out.

Discussion

Either permanent or temporary pacemaker applications are currently being used in various emergency or cardiology departments all around the world. Physicians working in these facilities should know how to apply a temporary pacemaker and be able to manage its proper function as well as deal with problems. One of these problems might be inadvertent malpositioning of the pacing lead in the left ventricle instead of the right ventricle. It often occurs when the physician doesn’t know the anatomy well and overlooks some important points during positioning of the pacemaker lead. Malpositioning of the pacing lead in the coronary sinus and through the patent foramen ovale into the apex of the left ventricle has been previously reported.1,2

This rare complication of pacemaker lead insertion should be suspected by observation of the right bundle branch block morphology on ECG and the unusual orientation of the lead body on fluoroscopy or chest radiography. After puncturing the subclavian vein, the guidewire should be directed into the inferior vena cava first before inserting the sheath. Care must be taken not to enter the arterial system. When using the femoral vein route one should first rotate the lead clockwise and then push it into the right ventricle or go into the superior vena cava and then pull the lead back to avoid entering the coronary sinus. If the ECG during implantation is insufficient for the interpretation of the presence or absence of right bundle branch block morphology, a 12 lead ECG with ventricular capture should be recorded immediately after the procedure by applying a magnet or testing the device with the programmer.1 If there is still doubt about the lead position, then a two dimensional echocardiography (either transthoracic or transoesophageal) should be performed because it is the imaging method of choice for proper diagnosis.

The post-procedure ECG (fig 1; see p 431) in our patient clearly shows paced right bundle branch block morphology and rightward as well as inferiorly directed QRS axis that might help us to locate the stimulation site—namely, the high lateral epicardial left ventricular region. The fluoroscopic view (fig 2; see p 431) also demonstrates the unusual leftward orientation of the pacing lead suggestive of lead malpositioning in the coronary sinus or its tributaries. After confirming malpositioning of the pacing lead in the coronary sinus, as is seen in fig 2, a second temporary pacing lead was inserted through the contralateral vein into the right ventricle and the malpositioned lead in the coronary sinus was safely pulled back.

Malpositioning of the temporary pacing lead in the coronary sinus may be responsible for loss of capture, high capture thresholds, perforation, and thrombus formation. However, inadvertently implanting a permanent pacing lead in the left ventricle by the routes mentioned above may cause more troublesome and unwanted events such as thromboembolism. In such circumstances both lead removal and anticoagulant therapy are recommended therapeutic modalities.

In conclusion, physicians or residents applying temporary pacemakers should be aware of the potential problems and complications of this procedure. Although rarely observed, lead malpositioning may result in troublesome events. Therefore, after every temporary or permanent pacemaker procedure the physician should check the proper function and location of the pacing system with the aid of simple diagnostic tools such as a 12 lead ECG, chest radiography, fluoroscopy, and echocardiography.

Final diagnosis

Malpositioning of a temporary pacing lead in the coronary sinus.

REFERENCES

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