The effectiveness of time domain and nonlinear heart rate variability metrics in ultra-short time series.

Ultra short-term (UST) heart rate variability (HRV) has been used to establish normative HRV values. This study aims to investigate whether HRV metrics can capture changes in HRV from external stimuli, and whether these metrics remain effective under various recording length. Participants completed varying stimulating activities including viewing images, arithmetic tasks, and memory recall of viewed images. SDNN, RMSSD, pNN50, SD2, SD1/SD2, and DFA were extracted from the data. Comparing arithmetic calculation and the first minute of memory recall, SDNN, pNN50, SD2, and SD1/SD2 had significant HRV differences; this suggests that these metrics can distinguish the inherently different stimuli participants were exposed to. However, comparing first minute of viewing with that of the second, SDNN, pNN50, and SD2, presented some significant HRV differences during two inherently similar stimuli. Comparing the first 60-120 s during viewing, SDNN, pNN50, and SD2 also presented significant differences. Our results suggest that SDNN, pNN50, and SD2 may not be robust in evaluating UST HRVs in replacement of the standard short-term HRV. It may be beneficial to analyze multiple HRV metrics, particularly SD1/SD2, to achieve a more holistic understanding of the underlying physiology.

Heart Rate Variability in Healthy Subjects During Monitored, Short-Term Stress Followed by 24-hour Cardiac Monitoring.

Heart Rate Variability (HRV) can be a useful metric to capture meaningful information about heart function. One of the non-linear indices used to analyze HRV, Detrended Fluctuation Analysis (DFA), finds short and long-term correlations in RR intervals to capture quantitative information about variability. This study focuses on the impact of visual and mental stimulation on HRV as expressed via DFA within healthy adults. Visual stimulation can activate the automatic nervous system to directly impact physiological behavior such as heart rate. In this investigation of HRV, 70 participants (21 males) viewed images on a screen followed by a math and recall task. Each viewing segment lasted 2 min and 18 s. The math and memory recall task segment lasted 4 min total. This process was repeated 9 times during which the participants' electrocardiogram was recorded. 37 participants (12 males) opted in for an additional 24-h Holter recording after the viewing and task segments of the study were complete. Participants were randomly assigned to either a pure (organized image presentation) or mixed (random image presentation) image regime for the viewing portion of the study to investigate the impact of the external environment on HRV. DFA α1 was extracted from the RR intervals. Our findings suggest that DFA α1 can differentiate between the viewing [DFA α1 range from 0.96 (SD = 0.25) to 1.08 (SD = 0.22)] and the task segments [DFA α1 range from 1.17 (SD = 0.21) to 1.26 (SD = 0.25)], p < 0.0006 for all comparisons. However, DFA α1 was not able to distinguish between the two image regimes. During the 24-hour follow up, participants had an average DFA α1 = 1.09 (SD = 0.14). In conclusion, our findings suggest a graded response in DFA during short term stimulation and a responsiveness in participants to adjust physiologically to their external environment expressed through the DFA exponent.

Investigating fractal dimension, heart rate variability, and memory during different image sequencing regimes in young adults.

The goal of this study is to investigate patterns that emerge in brain and heart signals in response to external stimulating image regimes. Data were collected from 84 subjects of ages 18-22. Subjects viewed a series of both neutrally and negatively arousing pictures during 2-min and 18-s-long segments repeated nine times. Both brain [electroencephalogram (EEG)] and heart signals [electrocardiogram (EKG)] were recorded for the duration of the study (ranging from 1.5 to 2.5 h) and analyzed using nonlinear techniques. Specifically, the fractal dimension was computed from the EEG to determine how this voltage trace is related to the image sequencing. Our results showed that subjects visually stimulated by a series of mixed images (a randomized set of neutrally or negatively arousing images) had a significantly higher fractal dimension compared to subjects visually triggered by pure images (an organized set of either all neutral or all negatively arousing images). In addition, our results showed that subjects who performed better on memory recall had a higher fractal dimension computed from the EEG. Analysis of EKG also showed greater heart rate variability in subjects who viewed a series of mixed images compared to subjects visually triggered by pure images. Overall, our results show that the healthy brain and heart are responsive to environmental stimuli that promote adaptability, flexibility, and agility.

Contributions of Arousal, Attention, Distinctiveness, and Semantic Relatedness to Enhanced Emotional Memory: An Event-Related Potential and Electrocardiogram Study.

Enhanced emotional memory (EEM) describes memory benefits for emotional items, traditionally attributed to impacts of arousal at encoding; however, attention, semantic relatedness, and distinctiveness likely also contribute in various ways. The current study manipulated arousal, semantic relatedness, and distinctiveness while recording changes in event-related potentials and heart rate during memory encoding. Trials were classified as remembered or forgotten by immediate recall performance. Negative images were remembered significantly better than neutral, and related neutral images were remembered significantly better than unrelated neutral images. Higher P300 and late positive potential (LPP) amplitudes were associated with memory for negative images as compared with related neutral images, suggesting that negative images received additional attentional processing at encoding, and that this cannot be accounted for only by the inherent relatedness of negative stimuli. No encoding benefits were found for related neutral images though they were better remembered than unrelated neutral images, indicating retrieval dynamics impacted memory. When image types were intermixed, greater heart rate changes occurred, and negative and unrelated neutral images received increased elaborative processing as compared with related neutral images, perhaps due to the prioritization of encoding resources. These results suggest encoding and retrieval processes contribute to EEM, with emotional items benefiting additively.

Plasma omega-3 polyunsaturated fatty acids and survival in patients with chronic heart failure and major depressive disorder.

The omega-3 fatty acid (FA) concentration is low in patients with coronary heart disease (CHD). Supplement of omega-3 FA improves cardiovascular outcomes in patients with CHD and heart failure (HF). However, plasma omega-3 FA and its role for prognosis in HF patients have not been examined previously. In this study, we explore the prognostic value of omega-3 polyunsaturated FA in HF patients with major depressive disorder (MDD). Plasma was obtained from HF patients with MDD who participated in the Sertraline Against Depression and Heart Disease in Chronic Heart Failure trial. FA methyl esters were analyzed by the method of a flame ionization detector. Weight percent is the unit of the omega compounds. The primary outcome was survival which was analyzed using Cox proportional hazards regression modeling. A total of 109 depressed HF patients had adequate volume for completion of the FA assays. Plasma total omega-3 (hazard ratio [HR] 0.65, 95% confidence interval [CI] 0.43-0.98) and EPA_(0.1 unit) (HR 0.73, 95% CI 0.56-0.96) were significantly associated with survival of patients with HF and co-morbid MDD. The results suggest that low plasma omega-3 FA is a significant factor for reduced survival in HF patients with MDD.

Responses of mental stress-induced myocardial ischemia to escitalopram treatment: background, design, and method for the Responses of Mental Stress Induced Myocardial Ischemia to Escitalopram Treatment trial.

BACKGROUND: Mental stress-induced myocardial ischemia (MSIMI) is common in patients with clinically stable coronary heart disease (CHD) and is associated with poor outcomes. Depression is a risk factor of MSIMI. The REMIT trial investigates whether selective serotonin reuptake inhibitor (SSRI) treatment can improve MSIMI. The rationale and outline of the study are described. METHOD: In this single-center randomized clinical trial, adult patients with clinically stable CHD are recruited for baseline mental and exercise stress testing assessed by echocardiography. In addition, psychometric questionnaires are administered, and blood samples are collected for platelet activity analysis. Patients who demonstrate MSIMI, defined by new abnormal wall motion, ejection fraction reduction ≥8%, and/or development of ischemic ST change in electrocardiogram during mental stress testing, are randomized at a 1:1 ratio to escitalopram or placebo for 6 weeks. Approximately 120 patients with MSIMI are enrolled in the trial. The stress testing, platelet activity assessment, and psychometric questionnaires are repeated at the end of the 6-week intervention. The hypothesis of the study is that SSRI treatment improves MSIMI via mood regulation and modification of platelet activity. CONCLUSION: The REMIT study examines the effect of SSRI on MSIMI in vulnerable patients with CHD and probes some potential underlying mechanisms.

Characteristics of depression remission and its relation with cardiovascular outcome among patients with chronic heart failure (from the SADHART-CHF Study).

Depression is prevalent in patients with heart failure and is associated with a significant increase in hospitalizations and death. Primary results of the Sertraline Against Depression and Heart Disease in Chronic Heart Failure (SADHART-CHF) trial revealed that sertraline and placebo had comparable effects on depression and cardiovascular outcomes. In this study, we explored whether remission from depression was associated with better survival and aimed to characterize participants who remitted during the trial. Based on depression response during the 12-week treatment phase, SADHART-CHF participants were divided into 2 groups: (1) remission, defined as participants whose last measured Hamilton Depression Rating Scale (HDRS) score was <8, and (2) nonremission, defined as participants whose last measured HDRS score was ≥8. Patients who dropped out before having any repeat HDRS were not included. Baseline characteristics and survival differences up to 5 years were evaluated between the remission and nonremission groups. Of the 469 SADHART-CHF participants, 208 (44.3%) achieved remission, 194 (41.4%) remained depressed, and 67 (14.3%) dropped out or died without any repeat HDRS assessment. Patients in the remission group had significantly fewer cardiovascular events than those in the nonremission group (1.34 ± 1.86 vs 1.93 ± 2.71, adjusted p = 0.01). Men patients were more likely to remit than women patients (56.5 vs 44.8%, p = 0.02). The remission group had milder depressive symptoms at baseline compared to the nonremission group (HDRS 17.0 ± 5.4 vs 19.6 ± 5.5, Beck Depression Inventory scale 17.9 ± 6.5 vs 20.3 ± 7.2, p <0.001 for the 2 comparisons). In conclusion, this study indicates that remission from depression may improve the cardiovascular outcome of patients with heart failure.

Effects of pregabalin on heart rate variability in patients with painful diabetic neuropathy.

UNLABELLED: Many studies have demonstrated that low heart rate variability (HRV) is a risk for high mortality and morbidity in patients with cardiovascular diseases. The primary purpose of the study was to evaluate whether pregabalin improves HRV in patients with diabetes and painful peripheral neuropathy. Resting heart rates were collected by using the LifeShirt System, developed by VivoMetrics (Ventura, Calif), at baseline and at the end of a 4-week intervention of pregabalin or placebo in patients with painful diabetic peripheral neuropathy. Heart rate variability analysis was performed on the collected R-R intervals using the Vivo- VMLA-036-00 3 Logic of the LifeShirt system. Of the 40 patients enrolled in the study, 70% completed the end of 4-week assessments (n = 15 in pregabalin and n = 14 in placebo). Compared with placebo, pregabalin treatment resulted in significant improvement in HRV measured by frequency domain analysis, that is, a reduction in low frequency-high frequency ratio (-1.30 ± 2.89 vs 0.37 ± 0.33, P = 0.03) and power of normalized low frequency (-0.049 ± 0.092 vs 0.0066 ± 0.023, P = 0.02), as well as an increase in power of normalized high frequency (0.039 ± 0.094 vs -0.038 ± 0.066, P = 0.02). Furthermore, pregabalin resulted in greater reduction of pain and symptoms of anxiety and greater improvement of quality of life. The improvement of HRV measures were not correlated with change of those measures. In conclusion, 4-week pregabalin treatment improved HRV in patients with painful diabetic peripheral neuropathy. TRIAL REGISTRATION: NCT00573261 (clinicaltrials.gov).