Clinical utility of left atrioventricular coupling index to define the response to cardiac resynchronization therapy in heart failure patients

Background Left atrioventricular coupling index (LACI) reflects the close interaction between left atrial (LA) and left ventricular (LV) dynamics. LACI is calculated by the ratio between LA to LV end-diastolic volumes and expressed as a percentage. The response to cardiac resynchronization therapy (CRT) in heart failure patients with reduced ejection fraction (EF) is variable due to multiple clinical, structural, and electrophysiological factors. Aim of study The study aimed to verify the diagnostic value of LACI in defining the CRT response using Two-dimensional echocardiography. Subjects & Methods 275 heart failure patients (65.1±12.5 years, 71.6% males, 54.6% non-ischemic cardiomyopathy) underwent CRT implantation. Age matched 50 normal subjects were included as control group. Base line LACI was calculated for both HF patients and controls. Patients post CRT were followed at short-term (6 months) and mid to long-term follow up (47.1±30.9 months) clinically and by echocardiography. Patients were divided into CRT responders and non-responders using 4 different criteria; I) ≥5% increase LV-EF, II) combination of ≥5%increase or absence of worsening of LV-EF and ≥10% reduction of LV volume index, III) ≥10% reduction of LACI, and IV) combination of ≥5% increase or absence of worsening of LV-EF and ≥10% reduction of LACI. Results Compared with controls, all patients had significantly higher LACI (22.8±11.8% vs. 17±8%; P< 0.001). Using all criteria, the CRT non-response was higher in ischemic (35%-55% than non-ischemic) with male predominance (72.7%). Definition of CRT response at 6 months using LV-EF alone or combination of LV-EF and LV volume was comparable (P=0.05). Using LACI alone showed no significant differences compared with LV-EF alone or combination of LV-EF and LV volume (P= 0.2 and 0.4 respectively). The combination of LACI to LV-EF showed a significant increase in CRT-responders compared to LV-EF alone and LACI alone (P= 0.0002 and 0.009 respectively). Compared with the short-term results, LACI alone and the combination of LACI to LV-EF, showed no significant difference regarding the number and percentage of CRT-responders during mid to long-term follow up. Using LV-EF alone or combination of LV-EF to LV volume showed significant difference (P= 0.003 and 0.03 respectively). (Table) Conclusion To define the response to CRT, a combination of both LACI and LV-EF improvement was superior in defining the CRT- response than the other conventional parameters in short-term follow up. In addition, this combination showed no discrepancy between short and long-term follow up which supports the integration of LACI to define the CRT response regardless of the follow up time.