Non-contact left ventricular endocardial mapping in cardiac resynchronisation therapy

Echocardiographic examination of atrioventricular and interventricular delay optimization in cardiac resynchronization therapy

In 21 patients implanted with a biventricular pacing device with programmable interventricular delay (VVd), the myocardial performance index (MPI) was evaluated during spontaneous sinus rhythm, simultaneous biventricular pacing, and sequential biventricular pacing at different VVds and atrioventricular delays (AVds). The AVd-VVd combination associated with the minimum MPI defined patient-tailored biventricular pacing. Simultaneous biventricular pacing significantly improved MPI compared with spontaneous sinus rhythm. An additional improvement was obtained by tailored biventricular pacing. The optimal AVds were significantly shorter during right ventricular preactivation than during left ventricular preactivation.

[Patient selection for biventricular pacing]

In heart failure patients with a large QRS width, biventricular pacing has been shown to improve the fonctional status as well as hemodynamic parameters. However, there are non-responders despite of wide QRS complexes (between 15 and 35%). Patients selection might not rely only on electrical parameters. From an electrophysiological concept, clinicians moved toward a more electromechanical analysis, by using non-invasive tools such as Tissue Doppler imaging. Thereby, more than the QRS width, identification of intra-left ventricular asynchrony appears to be a crucial criterion for selecting responders to biventricular pacing. From this fact, several studies have demonstrated the efficacy of biventricular pacing to improve heart failure patients with narrow QRS but with intra-left ventricular asynchrony. Another parameter has been thought to be predominant, i.e. the left ventricular pacing site. If the pacing lead is located within a "slow conduction" area (at this time very difficult to identify during the implant procedure), biventricular pacing will generate a new asynchrony counteracting the beneficial expected. Thus, biventricular pacing appears to be more an electromechanical concept than exclusively electrical for selecting responders. Still, the optimal location of the left ventricular pacing lead remains to be determined.

Non-contact mapping of the left ventricle and new insights into the mechanisms for success of biventricular pacing

Results from cardiac resynchronisation therapy are likely to improve as methods for identifying likely responders and the optimum site for lead placement become more refined