Decrease of the percentage of biventricular pacing due to frequent ventricular extrasystole

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Tracing N° 1
Medtronic Devices: CRT Field: Management of atrial arrhythmias
Patient

68 years old man implanted with a triple chamber defibrillator Viva XT CRT-D for ischemic cardiomyopathy with left bundle branch block ; non responder to cardiac resynchronization ; percentage of biventricular pacing of 78% ; 

Graph and trace

The first line corresponds to an electrocardiographic derivation with superimposed markers; the second line corresponds to the right ventricular EGM, and the third line to the right atrial EGM;

  1. sinus rhythm and biventricular pacing (AS-BV) ;
  2. ventricular extrasystole with atrial detection included the post ventricular atrial blanking ;
  3. alternation of  a biventricular stimulation and a PVC: ventricular bigeminism susceptible to explain the decrease in the percentage of biventricular stimulation ;
  4. persistent ventricular bigeminism; modification of the programming (increase of the minimal heart rate form 55 to 70bpm);
  5. disappearing of the PVC and percentage of ventricular pacing at 100% during the rest of the consultation ;
Comments

Frequent ventricular extrasystole, isolated or paired, bigeminism or trigeminism, at rest or during exercise, is a common cause of decrease in the percentage of biventricular pacing. It also causes a relative bradycardia as the PVCs are relatively ineffective from an hemodynamical point of view. In resynchronized patient, the evolution of the frequency of PVCs should be continuously monitored because they can be promoted by metabolic disorders and induced by drugs, or express the worsening underlying heart disease, or even being at the origin of clinical decompensation. In non-responder patients, suppressing the PVCs is a priority to allow an increase in the percentage of biventricular pacing and thus expect a positive response to the resynchronization therapy. Different options are possible: 1) in this patient, an increase in the minimum rate at 70 bpm has eliminated the PVCs. A rate responsive function has also been programmed to force the atrial pacing during exercise. The effect of this type of programming on the PVC is often incomplete or only temporarily effective. Moreover it is occasionally necessary to program relatively high heart rate at rest (> 80 bpm), which is difficult to accept on the long term in those patients with a severe heart failure; 2) the anti-arrhythmic drug therapy (beta-blockers, amiodarone) are rarely effective in this context; 3) In the presence of monomorphic extrasystole a radiofrequency ablation procedure can be proposed. This last option is indicated in cases of impaired hemodynamic status or left ventricular function. The evaluation of the correlation between the functional and the clinical abnormalities is essential for the decision making process.

Theoritical features / Basic concepts

Resynchronization and atrial fibrillation Resynchronization and defibrillation function RESYNCHRONIZATION AND ATRIAL FIBRILLATION There is a vicious circle between heart failure and atrial fibrillation, one favoring the other and vice versa. The prevalence of atrial fibrillation in CRT candidates is high and increases with the functional class: approximately, 5% for patients in NYHA class I, 10 to 25% for patients in class II and III, 50% for patients in NYHA class IV. The presence atrial fibrillation reduces the probability of positive response after resynchronization, the complete and permanent biventricular capture (an essential prerequisite), being impaired in some patients with atrial fibrillation. A certain number of patients with atrial fibrillation present a rapid and irregular...