Cardiac vagal control in depression: a critical analysis

Rapidly developing research has found abnormal cardiac vagal control (CVC) in several physical and mental health conditions. CVC findings in depression are mixed, and the degree to which CVC is compromised in depression is unclear. A meta-analysis of 13 rigorous cross-sectional studies reveals that a diagnosis of depression exerts a small-to-medium effect size on CVC, and explains only about 2% of the overall variance in CVC. More robust data may emerge from alternative approaches to the depression-CVC relationship, such as the use of CVC to predict the course of the disorder. Despite the vigor of recent work on CVC and depression, overall findings are suggestive rather than conclusive. Methodological desiderata and priorities for future research are discussed, including the need to clarify the etiological significance of CVC.     

Cardiac workload and inhibitory control in younger and older adults

Our goal was to investigate age differences in the role played by cardiovascular regulation in response control. We questioned whether pre-test respiratory sinus arrhythmia (RSA; an index of phasic vagal cardiac control) and/or rate pressure product (RPP; a measure of cardiac workload) were associated with error rate and/or error-related electrocortical responses (ERPs) during a Go/NoGo inhibitory control task across three levels of working memory load. ERPs, RSA and RPP were indirectly associated with performance in young adults. Within the older group, higher resting RPP was directly associated with NoGo errors at all levels of load, an association not seen in the younger group. Thus, for older adults, excessive hemodynamic demands at rest were more relevant than on-task electrocortical responses in the prediction of inhibitory control errors. These data support the relevance of autonomic regulation in understanding age-related change in higher-order neurocognitive function.     

Cardiac vagal control and children's adaptive functioning: A meta-analysis

Polyvagal theory has influenced research on the role of cardiac vagal control, indexed by respiratory sinus arrhythmia withdrawal (RSA-W) during challenging states, in children's self-regulation. However, it remains unclear how well RSA-W predicts adaptive functioning (AF) outcomes and whether certain caveats of measuring RSA (e.g., respiration) significantly impact these associations. A meta-analysis of 44 studies (n = 4996 children) revealed small effect sizes such that greater levels of RSA-W were related to fewer externalizing, internalizing, and cognitive/academic problems. In contrast, RSA-W was differentially related to children's social problems according to sample type (community vs. clinical/at-risk). The relations between RSA-W and children's AF outcomes were stronger among studies that co-varied baseline RSA and in Caucasian children (no effect was found for respiration). Children from clinical/at-risk samples displayed lower levels of baseline RSA and RSA-W compared to children from community samples. Theoretical/practical implications for the study of cardiac vagal control are discussed.     

Cardiac vagal control and respiratory sinus arrhythmia during hypercapnia in humans

Normoxic hypercapnia may increase high-frequency (HF) power in heart rate variability (HRV) and also increase respiratory sinus arrhythmia (RSA). Low-frequency (LF) power may remain unchanged. In this study, 5-min ECG recordings (N = 10) were analyzed in time and frequency domains while human subjects breathed normoxic 5% CO2 (5%CO2) or room air (RA). Tidal volume (VT), inhalatory (TI), and exhalatory (TE) times of breaths in the final minute were measured. ECG time domain measures were unaffected by CO2 inhalation (P > 0.05). Following natural logarithmic transformation (LN), LFLN was unaltered (RA: 7.14 +/- 0.95 vs. 5%CO2: 7.35 +/- 1.12, P > 0.05), and HFLN increased (RA: 7.65 +/- 1.37 vs. 5%CO2: 8.58 +/- 1.11, P < 0.05) with CO2 inhalation. When changes in total power (NU) were corrected, LF(NU) decreased (RA: 34.4 +/- 22.9 vs. 5%CO2: 23.8 +/- 23.1, P < 0.01), and HFNU increased (RA: 56.5 +/- 22.3 vs. 5%CO2: 66.8 +/- 22.9, P < 0.01) with CO2 inhalation. TI (RA: 2.0 +/- 1.0 vs. 5%CO2: 1.9 +/- 0.8 s) and TE (RA: 2.5 +/- 1.1 vs. 5%CO2: 2.4 +/- 0.9 s) remained unchanged, but VT increased with CO2 inhalation (RA: 1.1 +/- 0.3 vs. 5%CO2: 2.0 +/- 0.8 L, P < 0.001). Heart rates during inhalation (RA: 35.2 +/- 4.4, 5%CO2: 34.5 +/- 4.8 beats min(-1)) were different from heart rates during exhalation (RA: 28.8 +/- 4.4, 5%CO2: 29.1 +/- 3.1 beats min(-1)). Hypercapnia did not increase the clustering of heart beats during inhalation, and we suggest that the HF component may not adequately reflect RSA.     

Cardiac responses induced during thought-based control of a virtual environment.

Cardiac responses induced by motor imagery were investigated in 3 subjects in a series of experiments with a synchronous (cue-based) Brain-Computer Interface (BCI). The cue specified right hand vs. leg/foot motor imagery. After a number of BCI training sessions reaching a classification accuracy of at least 80%, the BCI experiments were carried out in an immersive virtual environment (VE), commonly referred as a "CAVE". In this VE, the subjects were able to move along a virtual street by motor imagery alone. The thought-based control of VE resulted in an acceleration of the heart rate in 2 subjects and a heart rate deceleration in the other subject. In control experiments in front of a PC, all 3 subjects displayed a significant heart rate deceleration of the order of about 3-5%. This heart rate decrease during motor imagery in a normal environment is similar to that observed during preparation for a voluntary movement. The heart rate acceleration in the VE is interpreted as effect of an increased mental effort to walk as far as possible in VE.     

Cardiac myocyte cell cycle control in development, disease, and regeneration

Cardiac myocytes rapidly proliferate during fetal life but exit the cell cycle soon after birth in mammals. Although the extent to which adult cardiac myocytes are capable of cell cycle reentry is controversial and species-specific differences may exist, it appears that for the vast majority of adult cardiac myocytes the predominant form of growth postnatally is an increase in cell size (hypertrophy) not number. Unfortunately, this limits the ability of the heart to restore function after any significant injury. Interest in novel regenerative therapies has led to the accumulation of much information on the mechanisms that regulate the rapid proliferation of cardiac myocytes in utero, their cell cycle exit in the perinatal period, and the permanent arrest (terminal differentiation) in adult myocytes. The recent identification of cardiac progenitor cells capable of giving rise to cardiac myocyte-like cells has challenged the dogma that the heart is a terminally differentiated organ and opened new prospects for cardiac regeneration. In this review, we summarize the current understanding of cardiomyocyte cell cycle control in normal development and disease. In addition, we also discuss the potential usefulness of cardiomyocyte self-renewal as well as feasibility of therapeutic manipulation of the cardiac myocyte cell cycle for cardiac regeneration.     

The heart of cognitive control: Cardiac phase modulates processing speed and inhibition

Bodily states are heavily intertwined with cognitive processes. A prominent communication channel between bodily signals and brain structures is provided by baroreceptors. Their phasic activity associated with the cardiac phase has been shown to modulate cognitive control in socio-emotional contexts. However, whether this effect is specific to the affective dimension or impacts general cognitive control processes remains controversial. The aim of the present study is to investigate the effect of cardiac phase on different facets of cognitive control. We built a nonemotional cognitive control task to delineate mechanisms such as processing speed, response selection, response inhibition, and conflict monitoring. We showed that the systole (after the blood is ejected from the heart), compared to the diastole, was related to faster responses. Moreover, the cardiac phase dynamics also impacted response inhibition, with an increased probability of failure toward the middle of the course of systole. Although the reported effects were small in terms of magnitude, they highlight the influence of bodily states on abstract cognitive processes.     

Cardiac vagal control predicts spontaneous regulation of negative emotional expression and subsequent cognitive performance

The present research investigated whether cardiac vagal control (as measured by respiratory sinus arrhythmia, RSA) predicts an individual's predisposition to suppress negative emotional expressions. One hundred thirty-six participants watched either a negative film or a neutral film. Facial expressions were recorded during the film and subjective emotional responses were assessed afterwards. Participants performed verbal and spatial working memory tasks both before and after the film clips. We found that resting RSA modulated the degree of coherence between facial expressions of emotion and subjective emotional experience in the negative film condition. Specifically, participants with higher resting RSA expressed less but reported feeling just as much negative emotion as those with lower resting RSA. Moreover, higher resting RSA predicted smaller pre-film to post-film improvements in spatial working memory performance in the negative film condition, suggesting that expressive suppression among high RSA participants temporarily undermined the operation of working memory. In the neutral film condition, resting RSA did not relate to expressive or subjective responses or subsequent working memory performance. These results support the notion that cardiac vagal control reflects an internal marker of self-regulatory tendencies and suggest that spontaneous self-regulation associated with individual differences in resting RSA may temporarily deplete self-regulatory resources.     

Cardiac vagal control as a prospective predictor of anxiety in women diagnosed with breast cancer

Low cardiac vagal control (CVC) has been associated with state and trait anxiety and anxiety spectrum disorders. Studies indicate that diagnosis and treatments for breast cancer may be associated with anxiety. The current study examined whether CVC prospectively predicted a trajectory of change in anxiety following breast cancer diagnosis. Forty-three women diagnosed with non-metastatic breast cancer completed the Taylor Manifest Anxiety Scale and the Perceived Stress Scale, and a 5-min resting electrocardiographic (ECG) segment was recorded. Self-report measures were completed approximately every 3 months for a year. Respiratory sinus arrhythmia (RSA) significantly predicted the trajectory of change in anxiety over the follow-up period: participants with higher baseline RSA evidenced decreasing anxiety, whereas those with lower baseline RSA had increasing anxiety. These results are consistent with the hypothesis that CVC facilitates the modulation of anxiety in women coping with significant stressors of breast cancer diagnosis and treatment.     

Cardiac alpha-1 adrenoceptors are not involved in heart rate control of the anaesthetized dog

To study the possible role of cardiac postsynaptic alpha-1 adrenoceptors in heart rate control of the anaesthetized open-chest dog we injected a specific alpha-1 agonist (amidephrine) into the right coronary artery or stimulated electrically the right stellate ganglion. Reflex influences were minimized by bilateral cervical vagotomy and de-afferentiation of both stellate ganglia. Activation of alpha-2, beta- and muscarinic receptors was prevented by intravenous administration of yohimbine, propranolol and atropine, respectively. Since alpha-1 receptor stimulation could affect heart rate indirectly via coronary constriction, a continuous intracoronary infusion of adenosine (0.25 mg/kg/h) was given. Amidephrine did not affect heart rate at the lower dose (1–10 g). After the highest dose (100 g) the maximum variation in heart rate was an increase of 2.2±1.1 bpm at 3 min after injection (mean±SEM;P<0.05). This slight cardioacceleration was simultaneous with an aortic pressure rise of 13.8±3.4 mm Hg and it was abolished by alpha-1 blockade with prazosin (1 mg/kg i.v.). After propranolol (1 mg/kg+0.5 mg/kg/h) the residual positive chronotropic effect of sympathetic stimulation (12.2±4.0 bpm) was not significantly altered (13.8±5.7 bpm) by prazosin administration. Similar results were recorded without adenosine infusion. We conclude that in the anaesthetized dog chronotropic effects directly mediated by alpha-1 adrenoceptors either do not exist or lack physiological significance.     

Cardiac myxomas

Cardiac myxoma is the most common primary tumor of the heart. Between 1970 and 1998, 33 myxomas from patients operated at the Cardiosurgical Department were submitted for pathological examination. A review of age, sex and clinical symptoms of the patients as well as of gross and histological features of the tumors is presented. Immunohistochemical examination was performed on 10 selected myxomas-reactivity to vimentin, desmin, S-100 protein, cytokeratin and FVIIIR-Ag. The necessity of histological examination of the embolectomy material is stressed.     

Cardiac tumors

Primary cardiac tumors are rare and their subdivision often difficult because of their unknown origin. In the most recent classification, cardiac tumors are divided into benign (about 75% and malignant neoplasms in relationship to their tissue differentiation (rhabdomyoma, haemangioma, etc.) or uncertain aetiology (myxoma, papillary fibroelastoma). Primary malignant tumors are maimly represented by sarcomas. The most frequent tumor is cardiac myxoma, which by itself represents about 50% of all primary cardiac neoplasms. Although non-invasive technologies as trans-esophageal ecocardiography allow the detection and exact localization of cardiac mass, clinical diagnosis is often tardive. This is due, besides the intrinsic rarity, to two main factors: first, the tumor is often asymptomatic (incidental autopic finding) or; alternatively, it may show aspecif symptoms mimicking heart failure or other pathologies. In this article, clinicopathological features of main primary cardiac tumors are presented. Investigation of the histogenesis of some of these neoplasms is still a primary field of research.