Optimisation of cardiac resynchronisation therapy during exercise

Abstract

The benefits of cardiac resynchronisation therapy (CRT) in selected cohorts with systolic dysfunction and congestive heart failure are well established [1–3]. CRT reduces heart failure hospitalisations, decreases mortality, and improves the quality of life and cardiac function, described as left ventricular (LV) reverse remodelling. CRT improves inter-, intra- and atrio-ventricular dyssynchrony. It is important to stress that there is only a moderate correlation between clinical and echocardiographic response; i.e. patients with improvement in their clinical status might not always show significant reverse remodelling. Nevertheless, the number of patients who do not respond to this therapy remain as high as 30 % to 40 %. The reasons for not responding to CRT are probably complex and multifactorial. Patient selection, accurate assessment of dyssynchrony, LV lead placement and optimal position and device programming are of importance. This necessitates a comprehensive evaluation of baseline and post-implant clinical, electrocardiographic and echocardiographic data. Moreover, LV lead position optimisation and device interrogation are useful for optimising CRT and should be considered to maximise the therapeutic response to CRT. It is recommended to perform AV-delay optimisation in all patients, guided either by the device or by echocardiography. However, the role of AV and VV optimisation regarding long-term outcome remain debatable. The SMART AV trial [4] showed that patients with normal AV delay did not derive benefit from echo-guided or device-guided AV optimisation compared with the empiric settings. However, patients with prolonged AV conduction were not included in this prospective, randomised trial. Moreover, in the Freedom trial [5] the authors concluded that routine AV and VV optimisation, by echo or the QuickOpt algorithm in unselected CRT recipients, did not appear to contribute significantly to further improving responsiveness to CRT. A variety of techniques, including echocardiography-guided methods, have been described to determine the optimal AV and VV delays. Many of these techniques have poor reproducibility and are time-consuming [6, 7]. None of these techniques have been shown to be superior and long-term benefits are lacking. Most device-based algorithms allow a rapid, simplified approach to CRT optimisation. However, their clinical value has also been called into question. Only the CLEAR study [8, 9] results suggest the clinical value of frequent CRT optimisation by SonRTM algorithm or echocardiography in severe chronic heart failure patients in the long-term.