Povezanost intraventrikularnih poremećaja provođenja i cirkadijalnih promena varijabilnosti srčane frekvencije kod bolesnika sa ishemijskom miokardiopatijom

Abstract

Introdaction:Left bundle branch block (LBBB) and intraventricular conduction delay (IVCD) are associated with an increased arrhythmic risk in post-infarction patients with left ventricular (LV) dysfunction. The incidence of arrhythmic death is highest in the morning, possibly reflecting an autonomic imbalance. AIM: analysis of circadian heart rate variability changes (HRV) in post- infarction patients with LVEF ≤35%, with and without LBBB/IVCD. METHOD: 2 groups were included: Group-1 (n=27) with narrow QRS complexes (<110 ms), and Group-2 (n=28) with LBBB/ IVCD. Spectral HRV analysis was performed to obtain measures of total variability (total power-TP), low-frequency (LF) and high-frequency (HF) components, and LF/HF ratio. Comparisons between the groups were made using mean day-time (08 am - 08 pm) and night-time (08 pm - 08 am) HRV measures. RESULTS: no differences were found regarding clinical characteristics or LVEF (31.2±3.3 vs. 30.8±3.8%) (p>0.05 for all). Daytime (1986±635 vs. 1284±411 ms; p=0.016) and night-time (2042±701 vs. 1202±318 ms; p=0.001) TP values were higher in Group-1, as well as day-time (39.4±11.9 vs. 24.8±8.8 n.u; p<0.001) and night-time (27.5±7.3 vs. 32.8±6.6 n.u; p=0.014) LF measures, with preserved diurnal variability. Group-2 demonstrated increase in night-time LF component, lower day-time (21.5±11.7 vs. 14.5±4.4 n.u; p=0.021) and night-time (24.5±10.1 vs. 11.4±4.1 n.u; p<0.001) HF and unexpected night-time HF decrease and an increase in LF/HF ratio (p=0.002). CONCLUSION: LBBB/IVCD patients demonstrate reduced total HRV and disturbed circadian HRV pattern. Night-time LF increase and HF decrease and raised LF/HF ratio indicate augmented sympathetic and diminished parasympathetic modulation, possibly reflecting an increased arrhythmic risk.