Reactive heart rate variability in male patients with first-episode major depressive disorder

Interoceptive sensibility differentiates the predictive pattern of emotional reactivity on depression

The role of emotional reactivity in the psychopathology of depression has been studied widely but not comprehensively. Inconsistencies in existing literature indicate the presence of other factors may affect this dynamic. An individual's method of processing their physiological sensations is a third variable because emotions are psychophysiological. This study identified the predictiveness of ease of activation, intensity, and duration of negative and positive emotions on depressive symptoms differentiated by interoceptive sensibility (IS). A total of 270 community participants filled-in questionnaires assessing their IS, habitual emotional reactivity, depressive severity, and response bias. A two-step clustering analysis identified the IS characteristics. Negative and positive reactivity models among each IS cluster were tested using bootstrapping regression, controlling for gender and response bias. IS can be clustered into "high IS," "low IS," and "worriers." Both positive and negative reactivity's predictiveness patterns on depression were different between IS clusters. Lower positive reactivity predicted depression among individuals with low IS (harder to activate positive emotions) and worriers (shorter duration of positive emotions) but not among individuals with high IS. Those with high IS also exhibited the highest positive reactivity. Ease of activating negative emotions predicted depression among high IS individuals, and a longer duration of negative emotions predicted depression among worriers. IS may affect the psychopathology of depression through subjective emotional reactivity. Thus, IS characteristics can be incorporated into intervention plans.

Association between Heart Rate Variability Indices and Depressed Mood in Patients with Panic Disorder

Objective

Heart rate variability (HRV) reflects the regulation of the autonomic nervous system. Panic disorder is highly associated with autonomic dysfunction, and is often accompanied by depression. The aim of this study is to determine the association between depression and HRV indices in patients with panic disorder.

Methods

A total of 110 outpatients diagnosed with panic disorder participated in this study. The medical records of patients with panic disorder who visited the outpatient clinic of Konkuk University Hospital between December 2018 and March 2020 were retrospectively reviewed. Measurements used in this study include the Panic Disorder Severity Scale-Self Report, Beck Depression Inventory (BDI-II), Insomnia Severity Index, and HRV. Patients were divided into depressive and non-depressive groups based on their BDI-II scores. The association between HRV indices and depressive symptoms was statistically analyzed.

Results

The low frequency/high frequency (LF/HF) ratio was reduced in patients with depression (mean = -0.095, p = 0.004 in the above moderate depressive group, mean = -0.120, p = 0.020 in the severe depressive group). Significant correlations were found between depressive symptoms and standard deviation of NN interval (SDNN) (ms) (-0.19, p = 0.044), very low frequency (VLF) (ms2/Hz) (-0.22, p = 0.021), LF (-0.25, p = 0.008), HF (-0.19, p = 0.043), and LF/HF (-0.25, p = 0.009). Multiple linear regression analysis showed that BDI predicted SDNN (ms), VLF (ms2/Hz), LF, HF, and LF/HF.

Conclusion

We confirmed that the LF/HF ratio decreases when depression is accompanied by panic disorder. HRV indices may be useful markers for detecting depressive symptoms in patients with panic disorder.

Cardiac Autonomic and Cardiac Vagal Control During and After Depressive and Happiness Autobiographical Memories in Patients With Major Depressive Disorder

BACKGROUND

Heart rate variability (HRV) and respiratory sinus arrhythmia (RSA) are indices of cardiac autonomic and cardiac vagal control (CVC), both of which are markers of emotional regulation and physical health. This study examined (1) the differences in cardiac autonomic regulation and CVC during baseline, depressive, and happiness autobiographical memory tasks between participants with major depressive disorder (MDD group) and healthy controls (HC group); (2) the associations between depressive symptoms and cardiac autonomic and CVC; and (3) the reactivity and recovery of cardiac autonomic and CVC between the MDD and HC groups.

METHODS

A total of 168 and 178 participants were included in the MDD and HC groups, respectively. Demographic data and the Beck Depression Inventory-II were collected before the experimental procedure. Lead II electrocardiograph (ECG) was measured during baseline, depressive, and happiness autobiographical memory tasks, and then interbeat intervals from ECG were converted to the time and frequency domains of HRV and RSA.

RESULTS

The participants in the MDD group showed lower HRV (including standard deviation of normal to normal intervals, low frequency, the natural logarithm of low frequency, and the natural logarithm of high frequency) and CVC (RSA and lnRSA) than those in the HC group. Depressive symptoms were positively correlated with heart rate and negatively correlated with the indices of cardiac autonomic and CVC. There was significantly increased reactivity and recovery of cardiac autonomic and CVC during and after depressive and happiness autobiographical memory tasks in the HC group, but not in the MDD group.

DISCUSSION

Participants with MDD had cardiac autonomic and CVC dysregulation, decreased reactivity, and did not recover to baseline after emotional provocations. These results can be the theoretical basis for clinical intervention by using HRV biofeedback to restore cardiac autonomic regulation and CVC during and after emotional events in the future.

Heart Rate Variability as an Early Objective Indicator of Subjective Feeling of Depression in Daily Life

Objectives

Changes in the autonomic nervous system have been observed in patients with depressive disorders by measuring their heart rate variability (HRV). However, whether HRV associates with depressive events in healthy people remains unknown.

Methods

Four healthy people participated in the present study. Their HRVs were measured routinely for 6 to 13 months. During this time, two participants reported experiencing two and three bouts of depression, respectively. This approach allowed us to examine changes in the participants’ HRVs by comparing their HRVs from before and after the unexpected depressive events. Changes in HRV were compared against those of two participants who did not report any depressive event.

Results

Participants’ low frequency/high frequency (LF/HF) ratios of HRV were lower after the event of depression than before. Their LF/HF ratios increased after recovery from the depressive events. In contrast, two participants who did not report any depressive event showed relatively smaller changes in their LF/HF ratios across measurements.

Conclusions

These results suggest that the LF/HF ratio may provide an objective measure of subjective experiences of depression and help identify potential cases of clinical depression.

Heart Rate Variability Changes in Patients With Major Depressive Disorder: Related to Confounding Factors, Not to Symptom Severity?

Background

The aim of this study was to assess the electrophysiological and other influencing factors correlating with symptom severity in patients with major depressive disorder (MDD) under three different conditions: baseline, stress exposure, and relaxation following stress exposure.

Methods

Symptom severity was assessed using the Beck Depression Inventory (BDI-II) in 89 inpatients (37 women; mean age 51 years) with MDD. Resting heart rate (RHR), heart rate variability (HRV), respiration rate (RR), skin conductance (SC), and skin temperature (ST) were recorded at baseline for 300 s, under stress exposure for 60 s, and under self-induced relaxation for 300 s. Age, nicotine consumption, body mass index, and blood pressure were evaluated as influencing factors.

Results

The BDI-II mean score was 29.7 points. Disease severity correlated positively with SC elevation under stress exposure and with a higher RR in the relaxed state, but no association was found between HRV and symptom severity. Age and higher blood pressure were both associated with lower HRV and higher RHR.

Conclusion

The results indicate that, in patients with MDD, changes in the autonomic nervous system (ANS) are complex; and the assessment of ANS reactivity to stressors is useful. Elevated blood pressure might be underdiagnosed, although it is already relevant in patients with MDD in their early 50s.

Comparison of Autonomic Reactivity to the Stress between Adjustment Disorder and Major Depressive Disorder

OBJECTIVE

Adjustment disorder (AD) remains an ambiguous diagnosis that overlaps with major depressive disorder (MDD). This study compared autonomic reactivity to the stress between AD and MDD to test for biological differences.

METHODS

Physically healthy Korean male soldiers admitted to a psychiatric ward were recruited for participation. Clinical diagnoses indicated that 62 patients with AD and 47 with MDD were selected. Procedures consisted of electrocardiogram measurements according to three consecutive phases lasting five minutes each [i.e., resting, stress (including a mental arithmetic task and Stroop color word test), and recovery].

RESULTS

The reactive trends of all heart rate variability (HRV) parameters related to the stress tasks in participants with AD did not differ from those with MDD. High-frequency HRV (a proxy of parasympathetic activity) increased during times of stress for participants with AD and MDD. Despite similar reactive trends, AD participants had higher HRV values than participants with MDD during whole phases, particularly for variables reflecting overall autonomic activity.

CONCLUSION

AD is associated with higher basal activity in the autonomous nervous system when compared to MDD. However, both are associated with pathophysiology indicating an altered autonomic reactivity to stress.

Inverse autonomic stress reactivity in depressed patients with and without prior history of depression

BACKGROUND

There is a considerable association between major depressive disorder (MDD) and cardiovascular disease, most possibly relying on abnormalities in the autonomic nervous system (ANS)-related cardiac reactivity, although the exact underlying pathophysiological pathway is unclear. This study tends to shed some additional light on this background by investigating ANS reactivity in MDD with respect to previous depression history through an objective stress challenge paradigm.

METHODS

The study assessed the effects of an overnight hypothalamus-pituitary-adrenal (HPA) axis stimulation with metyrapone (MET) on baseline ANS activity through linear and non-linear heart rate variability (HRV) measures in the morning of two continuous days in a group of 14 physically healthy, antidepressant-free patients with clinical, non-psychotic MDD, to investigate differences in autonomic reactivity with respect to prior MDD history.

RESULTS

The main findings of this study include statistically significant time × group interactions with respect to several HRV measures, suggesting substantial differences on autonomic reactivity between patients with and without depression history. Hereby, recurrent-episode MDD patients showed lower vagal activity, while first-episode MDD patients increased PNS activity after HPA axis stimulation.

CONCLUSIONS

These findings indicate that HPA axis stimulation in MDD patients leads to inverse vagal response according to MDD history. We suggest that chronic stress system overactivation, as found in MDD, might lead to a progressive inversion of the original stress response through HPA axis and ANS divergence over the course of a recurrent illness. HRV could, thus, represent a significant biomarker in MDD with temporal sensitivity.

Cardiovascular Reactivity to Acute Mental Stress: THE IMPORTANCE OF TYPE D PERSONALITY, TRAIT ANXIETY, AND DEPRESSION SYMPTOMS IN PATIENTS AFTER ACUTE CORONARY SYNDROMES

PURPOSE

Links between psychophysiological reactions to stress stimuli and perceived mental distress, including type D personality, anxiety, and depression, are still under debate. The aim of this study was to examine associations between cardiovascular reactivity to social stress and mental distress in patients after acute coronary syndrome.

METHODS

Patients (n = 116, 86% males, 52 ± 8 yr) with coronary artery disease 2 wk after acute coronary syndrome were evaluated for sociodemographic, clinical characteristics and coronary artery disease risk factors. The Trier Social Stress Test was employed to measure cardiovascular reactions to social stress (systolic and diastolic blood pressure and heart rate). Mental distress assessment included type D personality (Type D Scale), anxiety and depressive symptoms (Hospital Anxiety and Depression Scale), and state and trait anxiety (State-Trait Anxiety Inventory).

RESULTS

Multiple linear regression analysis showed associations between type D personality and lower heart rate during Trier Social Stress Test periods of task instruction (β = -.196, P < .04), preparation time (β = -.232, P < .01), and recovery time (β = -.209, P < .029). Higher trait anxiety was linked with lower heart rate during baseline rest (β = -.287, P < .01), task instruction (β = -.286, P < .01), preparation time (β = -.241, P < .01), and recovery period (β = -.209, P < .05). Depressive symptoms were associated with higher systolic blood pressure during baseline rest (β =.187, P < .05), task instruction (β = .306 P < .01), and free speech (β = .264, P < .05).

CONCLUSIONS

Mental distress was associated with cardiovascular stress reactions independent from possible covariates, suggesting dysregulated psychophysiological reactions to acute stress.

Feature of Heart Rate Variability and Metabolic Mechanism in Female College Students with Depression

Purpose

To explore the effects of depression on cardiac autonomic nerve function and related metabolic pathways, the heart rate variability (HRV) and urinary differential metabolites were detected on the college students with depression.

Methods

12 female freshmen with depression were filtered by the Beck Depression Inventory (BDI-II) and Self-rating Depression Scale (SDS). By wearing an HRV monitoring system, time domain indexes and frequency domain indexes were measured over 24 hours. Liquid chromatography–mass spectrometry (LC-MS) was used to detect their urinary differential metabolites. Differential metabolites were identified by principal component analysis (PCA) and orthogonal projections to latent structures discriminant analysis (OPLS-DA). The metabolic pathways related to these differential metabolites were analyzed by the MetPA database.

Results

Stress time was significantly increased, and recovery time was markedly decreased in the depression group compared with the control group (p < 0.001). Standard deviation of the normal-to-normal R interval (SDNN), root mean square of the beat-to-beat differences (RMSSD), high frequency (HF), and low frequency (LF) were decreased significantly (p < 0.001). Standard deviation of the normal-to-normal R interval (SDNN), root mean square of the beat-to-beat differences (RMSSD), high frequency (HF), and low frequency (LF) were decreased significantly (

Conclusion

Some autonomic nervous system disruption, high stress, and poor fatigue recovery were confirmed in college students with depression. The metabolic mechanism involved the disruption of coenzyme Q biosynthesis, glycine-serine-threonine metabolism, tyrosine metabolism, pyrimidine metabolism, and steroid metabolism under daily stress.

Associations of depression severity with heart rate and heart rate variability in young adults across normative and clinical populations

Limitations of current depression treatments may arise from a lack of knowledge about unique psychophysiological processes that contribute to depression across the full range of presentations. This study examined how individual variations in heart rate (HR) and heart rate variability (HRV) are related to depressive symptoms across normative and clinical populations in 152 young adults (aged 18-35 years). Moderating effects of sex and antidepressant medication status were considered. Electrocardiogram data were collected during "vanilla" baseline and in response to positive and negative emotional cues. Linear regressions and repeated-measures mixed models were used to assess the relationships between Beck Depression Inventory-II (BDI-II) scores, sex, antidepressant use, and cardiovascular outcomes. Baseline models yielded significant main effects of BDI-II and sex on HR and significant interactions between antidepressant medication status and BDI-II on HRV outcomes. The main effects of BDI-II and sex on HR were no longer significant after controlling for cardiorespiratory fitness. Participants who denied current antidepressant use (n = 137) exhibited a negative association and participants who endorsed current antidepressant (n = 15) use exhibited a positive association between BDI-II scores and HRV. Emotional reactivity models were largely non-significant with the exception of a significant main effect of antidepressant medication status on high-frequency HRV reactivity. Results indicated antidepressant medication use may moderate the relationship between depression severity and cardiovascular functioning, but this requires replication given the modest proportion of medicated individuals in this study. Overall, findings suggest cardiovascular processes and cardiorespiratory fitness are linked to depression symptomatology and may be important to consider in depression treatment.

Heart rate and high frequency heart rate variability during stress as biomarker for clinical depression. A systematic review

The interaction of physical and mental vulnerability and environmental constraints is thought to foster the development of psychiatric disorders such as major depressive disorder (MDD). A central factor in the development of psychopathology is mental stress. Despite some evidence for parasympathetic withdrawal and sympathetic overactivity in MDD, the psychophysiological response to stress in depression is not clear-cut. Given the growing interest in heart rate and heart rate variability as indicators for remote monitoring of patients, it is important to understand how patients with MDD react to stress in a laboratory-controlled environment. We conducted a systematic review of studies using electrocardiography to derive heart rate and heart rate variability during stress in patients with clinical depression. We focused on well-validated stress tasks- the mental arithmetic stress task, the Trier social stress task and public speaking task- to minimize confounding effects due to the nature of the stressor. The majority of studies found hypo-reactivity during stress as a hallmark of depression as evidenced by lower fluctuation in heart rate and heart rate variability in the high-frequency band. We address the potential underlying biological mechanisms, the influence of covariates on these measures and briefly discuss the specificity and potential for remote monitoring by using these variables.

The development of a novel high-precision major depressive disorder screening system using transient autonomic responses induced by dual mental tasks

12.6% of major depressive disorder (MDD) patients have suicide intent, while it has been reported that 43% of patients did not consult their doctors for MDD, automated MDD screening is eagerly anticipated. Recently, in order to achieve automated screening of MDD, biomarkers such as multiplex DNA methylation profiles or physiological method using near infra-red spectroscopy (NIRS) have been studied, however, they require inspection using 96-well DNA ELIZA kit after blood sampling or significant cost. Using a single-lead electrocardiography (ECG), we developed a high-precision MDD screening system using transient autonomic responses induced by dual mental tasks. We developed a novel high precision MDD screening system which is composed of a single-lead ECG monitor, analogue to digital (AD) converter and a personal computer with measurement and analysis program written by LabView programming language. The system discriminates MDD patients from normal subjects using heat rate variability (HRV)-derived transient autonomic responses induced by dual mental tasks, i.e. verbal fluency task and random number generation task, via linear discriminant analysis (LDA) adopting HRV-related predictor variables (hear rate (HR), high frequency (HF), low frequency (LF)/HF). The proposed system was tested for 12 MDD patients (32 ± 15 years) under antidepressant treatment from Shizuoka Saiseikai General Hospital outpatient unit and 30 normal volunteers (37 ± 17 years) from Tokyo Metropolitan University. The proposed system achieved 100% sensitivity and 100% specificity in classifying 42 examinees into 12 MDD patients and 30 normal subjects. The proposed system appears promising for future HRV-based high-precision and low-cost screening of MDDs using only single-lead ECG.

Altered autonomic reactivity in Korean military soldiers with adjustment disorder

Only few studies addressing the biological background of adjustment disorder (AD) exist. We examined the psychophysiological correlates indicative of autonomic regulation in AD. Heart rate variability (HRV), skin conductance, skin temperature, electromyography, and respiration were measured during serial stress tasks in 33 soldiers with AD and 60 healthy controls (HC). Patients with AD displayed lower relative power of high frequency (rHF) HRV and higher relative power of very low frequency (rVLF) HRV compared with HC at baseline. Inversely, the rHF of patients with AD remained higher and their rVLF remained lower compared with HC parameters after the single stress task, which suggests a reversed sympathovagal balance in AD. Mean heart rate and skin conductance increased during stress tasks in patients, although to a lesser extent than in HC. Skin temperature remained unchanged in all tasks in patients with AD. The tension of the frontalis muscle was higher in patients compared with HC from the second stress task onward. Thoracic breathing was more prevalent in patients with AD. Our study suggests altered autonomic reactivity in AD, which leads to a lack of sympathetic response to stress. We conclude that the distinctive biological mechanisms underlying AD are different from normal stress reactions.

Assessing mood symptoms through heartbeat dynamics: An HRV study on cardiosurgical patients

BACKGROUND

Heart Rate Variability (HRV) is reduced both in depression and in coronary heart disease (CHD) suggesting common pathophysiological mechanisms for the two disorders. Within CHD, cardiac surgery patients (CSP) with postoperative depression are at greater risk of adverse cardiac events. Therefore, CSP would especially benefit from depression early diagnosis. Here we tested whether HRV-multi-feature analysis discriminates CSP with or without depression and provides an effective estimation of symptoms severity.

METHODS

Thirty-one patients admitted to cardiac rehabilitation after first-time cardiac surgery were recruited. Depressive symptoms were assessed with the Center for Epidemiologic Studies Depression Scale (CES-D). HRV features in time, frequency, and nonlinear domains were extracted from 5-min-ECG recordings at rest and used as predictors of "least absolute shrinkage and selection" (LASSO) operator regression model to estimate patients' CES-D score and to predict depressive state.

RESULTS

The model significantly predicted the CES-D score in all subjects (the total explained variance of CES-D score was 89.93%). Also it discriminated depressed and non-depressed CSP with 86.75% accuracy. Seven of the ten most informative metrics belonged to non-linear-domain.

LIMITATIONS

A higher number of patients evaluated also with a structured clinical interview would help to generalize the present findings.

DISCUSSION

To our knowledge this is the first study using a multi-feature approach to evaluate depression in CSP. The high informative power of HRV-nonlinear metrics suggests their possible pathophysiological role both in depression and in CHD. The high-accuracy of the algorithm at single-subject level opens to its translational use as screening tool in clinical practice.

Inflexibility as a Vulnerability to Depression: A Systematic Qualitative Review

The study of vulnerabilities to depression typically identifies factors that are thought to be universally maladaptive or adaptive. In contrast, researchers recently have theorized that the ability to flexibly engage in different thoughts and behaviors that fit situational demands may be most indicative of psychological health. We review empirical evidence from 147 studies reporting associations between five components of flexibility (set-shifting, affective set-shifting, cardiac vagal control, explanatory flexibility, and coping flexibility) and depression and classify studies according to strength of study design. Evidence from correlational and case-controlled studies suggests cross-sectional relationships, but few prospective studies have been conducted. We discuss limitations of existing studies, identify new directions for programmatic research, and discuss implications that flexibility has for the prevention and treatment of depression.

Longitudinal monitoring of heartbeat dynamics predicts mood changes in bipolar patients: A pilot study

OBJECTIVES

Recent research indicates that Heart Rate Variability (HRV) is affected in Bipolar Disorders (BD) patients. To determine whether such alterations are a mere expression of the current mood state or rather contain longitudinal information on BD course, we examined the potential influence of states adjacent in time upon HRV features measured in a target mood state.

METHODS

Longitudinal evaluation of HRV was obtained in eight BD patients by using a wearable monitoring system developed within the PSYCHE project. We extracted time-domain, frequency-domain and non-linear HRV-features and trained a Support Vector Machine (SVM) to classify HRV-features according to mood state. To evaluate the influence of adjacent mood states, we trained SVM with different HRV-feature sets: 1) belonging to each mood state considered alone; 2) belonging to each mood state and normalized using information from the preceding mood state; 3) belonging to each mood state and normalized using information from the preceding and subsequent mood states; 4) belonging to each mood state and normalized using information from two randomly chosen states.

RESULTS

SVM classification accuracy within a target state was significantly greater when HRV-features from the previous and subsequent mood states were considered.

CONCLUSIONS

Although preliminary and in need of replications our results suggest for the first time that psychophysiological states in BD contain information related to the subsequent ones. Such characteristic may be used to improve clinical management and to develop algorithms to predict clinical course and mood switches in individual patients.

Atypical reactivity of heart rate variability to stress and depression across development: Systematic review of the literature and directions for future research

Heart rate variability has received growing attention in the depression literature, with several recent meta-analyses indicating that lower resting heart rate variability is associated with depression. However, the role of fluctuations in heart rate variability (or reactivity) in response to stress in depression remains less clear. The present review provides a systematic examination of the literature on heart rate variability reactivity to a laboratory-induced stressor task and depression, including 26 studies of reactivity in heart rate variability and clinical depression, remitted (or history of) depression, and subthreshold depression (or symptom-level depression) among adults, adolescents, and children. In addition to reviewing the findings of these studies, methodological considerations and conceptual gaps in the literature are addressed. We conclude by highlighting the importance of investigating the potential transactional relationship between heart rate variability reactivity and depression and possible mechanisms underlying this relationship.

Maladaptive mood repair, atypical respiratory sinus arrhythmia, and risk of a recurrent major depressive episode among adolescents with prior major depression

BACKGROUND

Because depressive illness is recurrent, recurrence prevention should be a mainstay for reducing its burden on society. One way to reach this goal is to identify malleable risk factors. The ability to attenuate sadness/dysphoria (mood repair) and parasympathetic nervous system functioning, indexed as respiratory sinus arrhythmia (RSA), are impaired during depression and after it has remitted. The present study therefore tested the hypothesis that these two constructs also may mirror risk factors for a recurrent major depressive episode (MDE).

METHOD

At time 1 (T1), 178 adolescents, whose last MDE had remitted, and their parents, reported on depression and mood repair; youths' RSA at rest and in response to sad mood induction also were assessed. MDE recurrence was monitored until time 2 (T2) up to 2 years later. Mood repair at T1 (modeled as a latent construct), and resting RSA and RSA response to sadness induction (RSA profile), served to predict onset of first recurrent MDE by T2.

RESULTS

Consistent with expectations, maladaptive mood repair predicted recurrent MDE, above and beyond T1 depression symptoms. Further, atypical RSA profiles at T1 were associated with high levels of maladaptive mood repair, which, in turn, predicted increased risk of recurrent MDE. Thus, maladaptive mood repair mediated the effects of atypical RSA on risk of MDE recurrence.

CONCLUSIONS

This study documented that a combination of behavioral and physiological risk factors predicted MDE recurrence in a previously clinically referred sample of adolescents with depression histories. Because mood repair and RSA are malleable, both could be targeted for modification to reduce the risk of recurrent depression in youths.

The history, hotspots, and trends of electrocardiogram

The electrocardiogram (ECG) has broad applications in clinical diagnosis and prognosis of cardiovascular disease. Many researchers have contributed to its progressive development. To commemorate those pioneers, and to better study and promote the use of ECG, we reviewed and present here a systematic introduction about the history, hotspots, and trends of ECG. In the historical part, information including the invention, improvement, and extensive applications of ECG, such as in long QT syndrome (LQTS), angina, and myocardial infarction (MI), are chronologically presented. New technologies and applications from the 1990s are also introduced. In the second part, we use the bibliometric analysis method to analyze the hotspots in the field of ECG-related research. By using total citations and year-specific total citations as our main criteria, four key hotspots in ECG-related research were identified from 11 articles, including atrial fibrillation, LQTS, angina and MI, and heart rate variability. Recent studies in those four areas are also reported. In the final part, we discuss the future trends concerning ECG-related research. The authors believe that improvement of the ECG instrumentation, big data mining for ECG, and the accuracy of diagnosis and application will be areas of continuous concern.