Effects of cardiac resynchronization therapy and physiologicaL pacing on left atrioventricular coupling index: the REPHYL-LACI study

Introduction Cardiac dyssynchrony and right ventricular pacing are associated with left atrial (LA) remodeling and atrioventricular uncoupling. Cardiac resynchronization therapy -CRT and conduction system pacing –CSP are important therapeutic options. Left atrioventricular coupling index (LACI) is a novel imaging parameter useful to describe the relationship between LA and left ventricle (LV). It could be measured as the ratio between LA end-diastolic volume (EDV) and the LV EDV or, alternatively, as the LA volume indexed for body surface area (LAVi) divided for a’ measured by tissue Doppler imaging (TDI) at medial mitral annulus level. Higher values indicate greater impairment of atrioventricular coupling. However, LACI has not been investigated in patients treated with CRT or CSP, and there is no comparison data about the two different measurement methodologies with echocardiography. Purpose To study the effects of CRT/CSP on LACI. Methods We retrospectively collected clinical, ECG and echocardiographic data of patients treated with standard CRT or CSP. Changes between baseline and follow-up (i.e. before and after CRT/CSP) were tested for significance. Baseline features were compared with these of a control group of patients without established major cardiovascular diseases. Results We enrolled fifty-six patients (median age at first echo 78[72.5-82]years; males 70%) and 56 controls (median age 77[72.5-83]years, p=0.974; males 57%, p= 0.170). Main clinical/instrumental data are shown in Table 1 and 2. In patients treated with CRT/CSP baseline LACIv (LAVid/LV EDV) was significantly lower than in controls (31[21-44]%vs34[29-48]%, p=0.040), despite higher LAVi and LV volumes in the first group (p<0.0001 for both). Conversely, LACId (LAVi/TDI-a’) was significantly higher in the CRT/CSP (4.48[2.81-8.28]vs2.89[2.36-3.67]mlxsecond/cm-1, p<0.0001). After a median follow-up of 515[282-1326]days, patients treated with CRT/CSP showed a significant increase of both LACIv (40[29-50]%, p=0.004) and LACId (4.95[3.77-9.89], p<0.0001). This worsening of atrioventricular coupling was accompanied by a trending LA dilatation with significant reduction of its reservoir function compared to baseline (expansion index 0.58[0.38-1.30]vs0.43[0.29-0.58], p=0.0002), despite a tendency toward stability or improvement of LV size and systolic/diastolic parameters. Conclusions In patients treated with CRT/CSP there is a worsening of LACI over time. We can speculate that the detrimental effects of artificial pacing might not be adequately counterbalanced by CRT/CSP, or that LV and LA pathology follow alternative trajectories with different responses to treatments. Moreover, the measurement of LACId should be probably avoided in patients with conduction disorders or paced. Further larger case-control studies are needed to clarify the usefulness of LACI as a valid parameter to assess atrioventricular coupling and its changes over time in patients treated with CRT/CSP.