A Novel Adaptive Noise Elimination Algorithm in Long RR Interval Sequences for Heart Rate Variability Analysis.

As heart rate variability (HRV) studies become more and more prevalent in clinical practice, one of the most common and significant causes of errors is associated with distorted RR interval (RRI) data acquisition. The nature of such artifacts can be both mechanical as well as software based. Various currently used noise elimination in RRI sequences methods use filtering algorithms that eliminate artifacts without taking into account the fact that the whole RRI sequence time cannot be shortened or lengthened. Keeping that in mind, we aimed to develop an artifacts elimination algorithm suited to long-term (hours or days) sequences that does not affect the overall structure of the RRI sequence and does not alter the duration of data registration. An original adaptive smart time series step-by-step analysis and statistical verification methods were used. The adaptive algorithm was designed to maximize the reconstruction of the heart-rate structure and is suitable for use, especially in polygraphy. The authors submit the scheme and program for use.

Daily Heart Rate Variability Indices in Subjects with and Without Metabolic Syndrome Before and After the Elimination of the Influence of Day-Time Physical Activity.

Background and Objectives: The available research shows conflicting data on the heart rate variability (HRV) in metabolic syndrome (MetS) subjects. The discrepancy suggests a methodical shortcoming: due to the influence of physical activity, the standard measuring of HRV at rest is not comparable with HRV assessment based on 24h Holter monitoring, which is preferred because of its comprehensiveness. To obtain a more reliable measure and to clarify to what extent HRV is altered in MetS, we assessed a 24h HRV before and after the elimination of the influence of physical activity. Materials and Methods: We investigated 69 metabolic syndrome (MetS) and 37 control subjects, aged 50-55. In all subjects, 24h monitoring of electrocardiogram, blood pressure, and actigraphy profiles were conducted. To eliminate the influence of day-time physical activity on RR intervals (RRI), a linear polynomial autoregressive model with exogenous terms (ARX) was used. Standard spectral RRI analysis was performed. Results: Subjects with MetS had blunted HRV; the diurnal SDNN index was reliably lower in the MetS group than in control subjects. The elimination of the influence of physical activity did not reveal a significant HRV change in long-term indices (SDNN, SDANN, and SD2), whilst adjacent RRI values (RMSSD, pNN50, and SD1) and SDNN index significantly increased (p < 0.001). An increase in the latter indices highlighted the HRV difference between the MetS and control groups; a significant (p < 0.001) decrease of all short-term HRV variables was found in the MetS group (p < 0.01), and low-frequency spectral components were less pronounced in the MetS group. Conclusion: The application of a polynomial autoregressive model in 24h HRV assessment allowed for the exclusion of the influence of physical activity and revealed that MetS is associated with blunted HRV, which reflects mitigated parasympathetic tone.

Impact of a Cognitive Behavioral Intervention on Health-Related Quality of Life and General Heart Rate Variability in Patients Following Cardiac Surgery: An Effectiveness Study.

BACKGROUND: Although there is evidence supporting the efficacy of cognitive-behavioral therapy (CBT) in decreasing psychologic symptoms and improving health-related quality of life in patients who have undergone coronary artery bypass graft surgery, the effectiveness of these interventions in usual health care practice, and their effect on general heart rate variability (HRV), has not been tested. OBJECTIVE: This study investigated the effectiveness of CBT in improving health-related quality of life and HRV in patients with postcardiac surgery. METHODS: However, 2 months following surgery, 150 patients were assigned sequentially to a CBT group that received the intervention for 9 months or a comparison group that received usual care. Patients were assessed at baseline and after 10 months with the 36-item Short Form Health Survey. HRV was also assessed. RESULTS: In total, 43 patients in the CBT group and 46 in the usual care group completed the study. The CBT group demonstrated significant improvements in health-related quality of life and significant increases in general HRV. Significant group-by-time interaction effects were found for the several 36-item Short Form Health Survey scales and mental component summary and a time-domain HRV parameter indicating that the pattern of change in scores over time differed significantly between the 2 groups. CONCLUSION: CBT administered in a "real-world" clinical setting can effectively improve health-related quality of life and the general HRV in patients who have undergone cardiac surgery.

Relationship of fatigue and exercise capacity with emotional and physical state in patients with coronary artery disease admitted for rehabilitation program.

BACKGROUND: The relationship between subjective fatigue, exercise capacity, and symptoms of depression and anxiety in patients with coronary artery disease (CAD) needs to be specified. METHODS: In this cross-sectional study, a total of 1,470 (64% men; mean age 57 ± 11 years) consecutive CAD patients admitted for cardiac rehabilitation after treatment of acute cardiac events were evaluated for demographic characteristics, for past and current diagnosis and treatment, for New York Heart Association (NYHA) class, for symptoms of depression and for symptoms of anxiety using the Hospital Anxiety and Depression Scale, and for subjective fatigue using the Multidimensional Fatigue Inventory. On the next day, all patients underwent exercise capacity evaluation using a standard bicycle ergometer testing procedure. RESULTS: In univariate regression analyses, there was the strongest positive association between scores on all Multidimensional Fatigue Inventory subscales and scores on the Hospital Anxiety and Depression Scale depression and anxiety subscales and between exercise capacity and NYHA class. Multivariate regression analyses revealed that symptoms of depression were the strongest positive determinants of all dimensions of subjective fatigue and, together with other significant variables, accounted for 17% to 29% of the variance. However, neither depressive nor anxious symptoms were significant determinants of exercise capacity. The association between subjective fatigue and exercise capacity and vice versa was minimal. CONCLUSION: Subjective fatigue in CAD patients is strongly related to symptoms of depression and symptoms of anxiety. In contrast, exercise capacity in CAD patients is strongly related to NYHA functional class, with no relationship to symptoms of depression and anxiety.

Defining the nocturnal period in 24-h ambulatory blood pressure monitoring: a comparison of three methods.

OBJECTIVES: The purpose of our study was to compare three definitions of ambulatory blood pressure (BP) nocturnal period and to assess their agreement in determining nocturnal BP dipping patterns. METHODS: We investigated 69 subjects with metabolic syndrome, aged 50-55 years. In all subjects, we assessed 24-h BP monitoring, electrocardiogram and actigraphy profiles. The nocturnal period was defined in three ways: as a fixed narrow nighttime period from 01:00 to 06:00, as a self-reported sleeping period and as a disappearance and onset of physical activity recorded by the actigraph. RESULTS: Our study revealed a significant discrepancy between the self-reported and actigraphy-based nocturnal periods (P < 0.001). In addition, different definitions of the nighttime yielded significant differences in determining nondipping, extreme dipping and dipping BP patterns, the identification of the latter being affected the most. The actigraphy-based approach best aligned with the fixed-time determination of the nocturnal period: Cohen's kappa coefficient for the nondipping pattern was 0.78 (0.58-1), for the dipping pattern 0.75 (0.59-0.91) and for the extreme dipping pattern 0.81 (0.65-0.97). In comparison to the self-reported determination of the nocturnal period, using the actigraphy-based approach resulted in reclassifying the nocturnal BP pattern in 20.3% of subjects. CONCLUSIONS: The lack of agreement between fixed-time, self-reported and actigraphy-based determinations of the nighttime period affects the identification of the nocturnal BP patterns. In comparison to the self-reported nocturnal period estimation, the actigraphy-based approach results in the reclassification of BP dipping status in every fifth subject.

Specific fatigue-related items in self-rating depression scales do not bias an association between depression and fatigue in patients with coronary artery disease.

OBJECTIVE: Self-rating instruments for depression include questions targeting fatigue, which is a common symptom of coronary artery disease (CAD) patients. We evaluated if specific fatigue-related questions in self-reported instruments of depression bias an association between fatigue and depression in CAD patients. METHODS: A total of 1470 CAD patients attending cardiac rehabilitation program were evaluated for fatigue using the Multidimensional Fatigue Inventory (MFI-20) and for symptoms of depression using the depression subscale of the Hospital Anxiety and Depression scale (HADS-D) and the Beck Depression Inventory-II (BDI-II). RESULTS: There was moderate correlation in MFI-20 scores vs. HADS-D scores and in MFI-20 scores vs. BDI-II scores, with stronger association in patients with less severe heart failure when compared to patients with more severe heart failure. Removal of questions targeting fatigue from the HADS-D and the BDI-II did not significantly change the association. CONCLUSIONS: Fatigue-related items should not be removed from the HADS-D and the BDI-II when evaluating CAD patients for depressive symptoms.

Construct and criterion validity of the DUFS and DEFS4 in Lithuanian patients with coronary artery disease.

BACKGROUND: Fatigue has become an important symptom in clinical diagnosis and clinical trials among subjects with cardiovascular diseases and disease-specific fatigue scales were developed in a Dutch and English version. OBJECTIVE: Various questionnaires for measuring fatigue have been developed, but currently no validated questionnaire targeted at subjects with cardiovascular disease and heart failure exists in the Lithuanian language. METHODS: Despite the rigor of the exploratory factor analysis and analyses of the psychometric properties of the disease-specific Dutch Fatigue Scale and the Dutch Exertion Fatigue Scale (DUFS-DEFS) we adopted a confirmatory approach considered as the gold standard method for the evaluation of construct validity in psychometric inventories. To test the criterion validity of the DUFS and DEFS structural equation modelling was employed with the widely used and validated Multidimensional Fatigue Inventory (MFI). RESULTS: The a priori specification of a hypothesized five-factor model of the MFI-20 and a two-factor model of the DUFS and DEFS appeared to have a good fit to the data in Lithuanian patients. The hypothesized model of the criterion validity of the DUFS and DEFS had a good fit and classes of disease severity showed statistically significant and clinically relevant differences on fatigue scores. CONCLUSION: The construct validity and criterion validity of the DUFS and DEFS were confirmed in a Lithuanian sample of cardiac patients. The construct validity of the MFI was also supported and this fatigue measure can be used in Lithuanian settings of clinical practice and research.