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Aim. To assess the association between changes in interventricular delay (IVD) and response to cardiac resynchronization therapy (CRT) during 24-month postoperative period in patients with quadripolar left ventricular leads.Material and methods. This retrospective non-randomized study included data from 48 patients with implanted CRT devices with quadripolar left ventricular (LV) leads, examined 3, 6, 12, 24 months after operation. CRT responders were considered patients with a decrease in end-systolic volume (ESV) by more than 10% compared with preoperative. To test the hypothesis about the rationale for choosing the maximum IVD when installing the LV lead, the group of patients was divided into two subgroups as follows: one with the maximum IVD (IVDmax, n=24), the other — without this condition (n=24).Results. A correlation was found between changes in IVD and ESV, as well as ejection fraction (EF) in the period of 6, 12 and 24 months after implantation compared to baseline. In the subgroup with IVDmax, the shortening of IVD in the postoperative period is higher at each considered period compared to the second subgroup, and in general, there is a more pronounced decrease in IVD over 24 months. At the same time, 3, 6, 12 months after surgery, patients with IVDmax show a significantly greater decrease in ESV and, accordingly, a greater increase in EF. Prognostic models of CRT response in the long term after implantation were created. Significant predictors were the initial IVD, changes in IVD in the early postoperative period and IVDmax selection. At the same time, not a single factor, taken separately, made it possible to separate responders and non-responders.Conclusion. A greater shortening of the IVD corresponds to a greater decrease in LV ESV and EDV, as well as a greater increase in EF in the long-term postoperative period. The choice of quadripolar LV lead in accordance with the maximum IVD is accompanied by a decrease in the proportion of non-responders, a more pronounced decrease in electrical ventricular dyssynchrony and an improvement in systolic function.

Aim. To study the characteristics of heart rate variability (HRV) in episodes of paro xysmal atrial fibrillation (AF) and sinus rhythm (SR) during the 24-hour Holter electro cardiographic (ECG) monitoring and to assess the presence and nature of their relationships.Material and methods. We analyzed 37 records of 24-hour Holter ECG monitoring obtained from patients with paroxysmal AF. For analysis, records were selected from the Long Term Atrial Fibrillation database (LTAFDB) (n=26), as well as from the long-term storage database “Myocard-holter” of the Sverdlovsk Regional Clinical Hospital № 1 (n=11). Each record contained at least 120 min of SR and at least 120 min of paroxysmal AF episodes. In addition, 48 HRV indices were calculated independently for SR and for AF episodes, after which the 96 HRV parameters obtained for each record were subjected to exploratory data analysis.Results. Analysis of HRV in AF paroxysm showed a significant increase in the RMSSD, SD1, pNN50 indices, which confirmed the great importance of parasympathetic influence in the regulation of AF. Despite the fact that single HRV parameters in AF are not directly related to any single parameters in SR, we have shown that the AF is not completely chaotic and independent of the characteristics of baseline HR variability. We found that for some of the HRV indices determined during AF paroxysm (PAF_CVI, PAF_pNN20, PAF_pNN50, PAF_ApEn, PAF_SDNN, PAF_SD2), up to 74% of the variance of these indices can be explained using multivariate linear models, including 4 HRV indices for SR and taken as predictors. It was shown that among all the indices analyzed, only the PAF_HTI, calculated in paroxysmal AF, had a moderate negative correlation with the duration of AF episodes (r=0,60, p

Aim. To determine quantitative criteria for assessing the therapeutic benefits and the most informative time frames after cardiac resynchronization therapy (CRT) to assess its long-term effectiveness (1, 2, 3 years of follow-up) based on retrospective analysis. To assess the CRT effectiveness, parameters of left ventricular (LV) reverse remodeling and signs characterizing the clinical CRT response were considered.Material and methods. This single-center, retrospective, non-randomized study included data from 278 patients with implanted CRT devices. Quantitative criteria for assessing CRT effectiveness were determined using a two-step cluster analysis of patients 1, 2, and 3 years after CRT by LV reverse remodeling parameters.Results. In the dataset with satisfactory division accuracy, after the first year, two clusters were identified, which are conventionally named as “non-responders” and “responders”. Two and three years after therapy, patients were classified into three clusters: “non-responders”, “responders” and “super-responders”. For the obtained clusters, we found cutoff values for LV reverse remodeling parameters, which can be used as criteria for response to therapy.The study identified the most informative time frames for assessing the postoperative CRT effectiveness 1, 2, 3 years after the surgery. At the same time, the clinical response to therapy is manifested earlier in comparison with the reverse LV remodeling.Despite the high divisibility of patients into responders and non-responders, predictive models of CRT effectiveness created using the available data from standard diagnostic protocols for heart failure patients have insufficient accuracy to be used for making decisions on therapy appropriateness. This circumstance indicates the need to receive additional data to improve the forecasting quality.Conclusion. The study revealed a period for assessing the clinical response and changes in LV reverse remodeling after CRT surgery, which is important for the optimal choice of postoperative therapy. It has been shown that in most cases, one year after surgery is sufficient to assess the clinical response, and the process of LV reverse remodeling can last up to two years on average.When assessing the CRT effectiveness by reverse remodeling, along with a change in LV end-systolic volume (ESV), it is necessary to take into account LV end-diastolic volume (EDV) changes. The change in LV ejection fraction showed a significantly lower value among the analyzed parameters in assessing the CRT effectiveness. Based on the cluster classification of patients, a dividing rule was established for responders and non-responders in the first and second years after surgery with an accuracy of 97%: a decrease in LV ESV and EDV by 9% or more compared to preoperative values.