LV lead displacement

Patient

64 years old man implanted with a triple chamber defibrillator Viva XT CRT-D for idiopathic dilated cardiomyopathy with a left bundle branch block; follow-up 3 months post implant. Non responding patient with unchanged symptomatology (shortness of breath for the daily activities); the device interrogation reveals 100% of biventricular pacing ;

Trace

On the tracings, the first line correspond to the surface ECG with the superimposed markers, the second one to the right ventricular bipolar EGM, the last one correspond to LV tip / RV coil EGM;

spontaneous atrial rythm and biventricular pacing (AS-BV) ;
modification of the programming (RV pacing only) ;
in right ventricular pacing configuration, nothing changes, the aspect of the surface and endocardial ECG are identical to that observed in biventricular suggesting an absence of left ventricular capture;

Measurement of left ventricular pacing Threshold (VDI 90 bpm) ;

ineffective left ventricular pacing;
LV pacing captures the left atrium; atrial depolarization is detected by the right atrial channel after the conduction delay between the right atrium and left atrium.
the atrial activation is conducted to the ventricle; the ventricular signal is high on the right ventricular channel; However, there is no ventricular marker as this signal falls within the post-ventricular stimulation ventricular blanking period; the timing between the signals detected in the right atrium and the right ventricule is relatively short, but the delay between the left atrium and right ventricle is longer and correspond to the conduction time between atrium and ventricle;
loss of atrial capture by the LV leads;
ineffective left ventricular pacing;
this time the spontaneous RV activity is detected by the RV leads because it falls after the blanking period ;The left ventricular lead of this patient had moved and fallen into the coronary sinus; he underwent a repositioning of the LV lead in a lateral vein; ICD interrogation :
RV pacing;
modification of the device programming (biventricular pacing) ;
clear modification of the surface ECG suggesting a left ventricular capture ;

Comments

This tracing demonstrates one of the specificity of the monitoring of CRT patients. A percentage of biventricular pacing close to 100% is a necessary prerequisites but not sufficient for a good response to resynchronization. Indeed, biventricular pacing does not means effective biventricular capture. In this patient, the interrogation of the device memories found a permanent biventricular pacing, but the surface electrocardiogram demonstrated a typical right ventricular apical pacing aspect with negative QRS in DII, DIII, aVF, and V1, and a wide positive QRS in DI. In this patient, the left ventricular lead had moved and had fallen in a position near the left atrial vein explaining the particular aspect of the threshold test. The vast majority of implantation procedures of CRT ends with the positioning of a left ventricular epicardial lead in a side branch of the coronary sinus. The risk of displacement of this type of lead is important because they are not equipped with an active fixation. LV leads are simply placed into the CS veins and blocked distally in small collaterals, or maintained in position by the curvatures of the lead in the vein meanderings.

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