64-year-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-responder patient with unchanged symptomatology (shortness of breath during daily activities); device interrogation reveals 100% of biventricular pacing.64-year-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-responder patient with unchanged symptomatology (shortness of breath during daily activities); device interrogation reveals 100% of biventricular pacing.
On the tracings, the first line corresponds to the surface ECG with the superimposed markers, the second line to the right ventricular bipolar EGM and the third line to the LV tip / RV coil EGM.
- spontaneous atrial rhythm and biventricular pacing (AS-BV);
- programming change (RV pacing only);
- in right ventricular pacing configuration, the surface and endocardial ECG patterns are identical to that observed during biventricular pacing suggesting an absence of left ventricular capture;
Measurement of left ventricular pacing threshold (VDI 90 bpm);
- ineffective LV pacing;
- LV pacing captures the left atrium; the atrial depolarization is sensed by the right atrial channel after the conduction delay between the right atrium and left atrium;
- the atrial activation is conducted to the ventricle; there is no ventricular marker as this signal falls within the post-ventricular pacing ventricular blanking period; the timing between the signals sensed in the right atrium and the right ventricle is relatively short, whereas the delay between the left atrium and right ventricle is longer and corresponds to the conduction time between atrium and ventricle;
- loss of atrial capture by the LV lead;
- ineffective left ventricular pacing;
- the spontaneous RV activity is sensed by the RV lead since it falls after the blanking period;
The left ventricular lead of this patient had dislodged and fallen into the coronary sinus; he underwent a repositioning of the LV lead in a lateral vein;
New ICD interrogation
- RV pacing;
- modification of the device programming (biventricular pacing);
- clear modification of the surface ECG suggesting a left ventricular capture.
Different access routes have been proposed for the pacing of the left ventricle: the transvenous route, by far the most commonly used, with positioning of the lead in a branch of the coronary sinus; the transseptal route which allows endocardial pacing; the epicardial route after surgical approach, which constitutes the most common recourse in the event of failure of the traditional approach, and finally, a still experimental access route with direct puncture of the pericardial space by transcutaneous approach. Venous access is the first-line approach used in a majority of centers given its high feasibility and limited risk of complications. The stability of the lead, however, remains a limitation with a higher risk of micro or macro-dislodgement than for an endocardial lead.
This tracing allows emphasizing one of the essential points of the interrogation of a triple-chamber defibrillator. A percentage of biventricular pacing nearing 100% is a necessary prerequisite but not sufficient for a good response to resynchronization. Indeed, biventricular pacing does not equate to effective biventricular capture. In this patient, memory interrogation revealed permanent biventricular pacing (100% pacing), whereas the electrocardiogram revealed a characteristic pattern of apical right ventricular pacing: positive QRS in lead I, negative in leads II, III and aVF, negative in V1, wide QRS. The left ventricular lead had moved and receded to a position near a left atrial vein explaining the particular pattern of the left ventricular pacing threshold test. This loss of left ventricular capture accounts for this patient's non-response. Future CRT defibrillator platforms could ultimately be equipped with algorithms enabling to confirm effective capture as opposed to pacing.