Non-contact left ventricular endocardial mapping in cardiac resynchronisation therapy

Abstract

Background: Up to 30% of patients with heart failure do not respond to cardiac resynchronisation therapy (CRT). This may reflect placement of the coronary sinus lead in regions of slow conduction despite optimal positioning on current criteria. Objectives: To characterise the effect of CRT on left ventricular activation using non-contact mapping and to examine the electrophysiological factors influencing optimal left ventricular lead placement. Methods and results: 10 patients implanted with biventricular pacemakers were studied. In six, the coronary sinus lead was found to be positioned in a region of slow conduction with an average conduction velocity of 0.4 m/s, v 1.8 m/s in normal regions (p , 0.02). Biventricular pacing with the left ventricle paced 32 ms before the right induced the optimal mean velocity time integral and timing for fusion of depolarisation wavefronts from the right and left ventricular pacing sites. Pacing outside regions of slow conduction decreased left ventricular activation time and increased cardiac output and dP/dt max significantly. Conclusions: In patients undergoing CRT for heart failure, non-contact mapping can identify regions of slow conduction. Significant haemodynamic improvements can occur when the site of left ventricular pacing is outside these slow conduction areas. Failure of CRT to produce clinical benefits may reflect left ventricular lead placement in regions of slow conduction which can be overcome by pacing in more normally activating regions.

Optimal site selection and image fusion guidance technology to facilitate cardiac resynchronization therapy

“…This has been attributed to changes in patterns of excitation and conduction due to altered ion channel activity [50] and decreased cellular connectivity [51] compounded by tortuous conduction through areas of surviving myocytes. This delay in LV activation results in less hemodynamic improvement during BiV pacing [52]. Electrical stimulation in regions of scar can also be pro-arrhythmic [53,54] and is associated with increased morbidity and mortality [8,55].…”

“…Advantages of this system include the ability to acquire multiple endocardial electrograms during a single cardiac cycle; however, this comes at the cost of greater inaccuracy in electrogram timing and morphology at greater distances from the MEA [75]. Work evaluating this system has already established that non-contact mapping can identify regions of electrically viable myocardium, which could be used to inform lead position, particularly among ischemic patients [52]. …”

“…More detailed analysis of LV activation revealed heterogeneity in conduction velocities in both non-ischemic and ischemic patients at the site of LV stimulation in the lateral and posterolateral walls [52]. The location of these areas of slow conduction influenced the pattern and direction of wave front propagation.…”

Regional myocardial contractile reserve assessed by strain echocardiography and the response to cardiac resynchronization therapy

“…Location of the LV electrode tip outside of slow conduction areas was associated with the significant hemodynamic improvement in patients with HF of ischemic and non-ischemic etiology undergoing CRT [15].…”

Ativação elétrica ventricular na ressincronização cardíaca caracterizada pelo mapeamento eletrocardiográfico de superfície

“…The electroanatomic mapping assessment, in turn, demonstrated the importance of the correct positioning of the leads of the pacemaker system for a better resynchronization and favorable responses to CRT [9][10][11] . Thus, body surface potential mapping (BSPM) may be useful in the assessment of biventricular pacing, facilitating the understanding of the mechanisms of cardiac electrical activation, and separating the activation of the right and left chambers, as well as contributing to other methods already described in the identification of the patients more likely to respond to CRT.…”