Epicardial Adipose Tissue Changes After Bariatric and Metabolic Surgery: a Systematic Review and Meta-analysis

Epicardial adipose tissue (EAT) is a visceral fat depot located between the myocardium and visceral epicardium. Emerging evidence suggests that excessive EAT is linked to increased risk of cardiovascular conditions and other metabolic diseases. A literature search was conducted from the earliest studies to the 26th of November 2022 on PubMed, Embase, and the Cochrane. All the studies evaluating changes in EAT, pericardial adipose tissue (PAT), or total cardiac fat loss before and after BS were included. From 623 articles, 35 were eventually included in the systematic review. Twenty-one studies showed a significant reduction of EAT after BS, and only one study showed a non-significant reduction (p = 0.2).

Prognostic Value of Combined Biomarkers in Patients With Heart Failure: The Heartmarker Score

Background

Heart failure (HF) biomarkers have prognostic value. The aim of this study was to combine HF biomarkers into an objective classification system for risk stratification of patients with HF.

Methods

HF biomarkers were analyzed in a population of HF outpatients and expressed relative to their cut-off values (N-terminal pro-B-type natriuretic peptide [NT-proBNP] >1,000 pg/mL, soluble suppression of tumorigenesis-2 [ST2] >35 ng/mL, growth differentiation factor-15 [GDF-15] >2,000 pg/mL, and fibroblast growth factor-23 [FGF-23] >95.4 pg/mL). Biomarkers that remained significant in multivariable analysis were combined to devise the Heartmarker score. The performance of the Heartmarker score was compared to the widely used New York Heart Association (NYHA) classification based on symptoms during ordinary activity.

Results

HF biomarkers of 245 patients were analyzed, 45 (18%) of whom experienced the composite endpoint of HF hospitalization, appropriate implantable cardioverter-defibrillator shock, or death. HF biomarkers were elevated more often in patients that reached the composite endpoint than in patients that did not reach the endpoint. NT-proBNP, ST2, and GDF-15 were independent predictors of the composite endpoint and were thus combined as the Heartmarker score. The event-free survival and distance covered in 6 minutes of walking decreased with an increasing Heartmarker score. Compared with the NYHA classification, the Heartmarker score was better at discriminating between different risk classes and had a comparable relationship to functional capacity.

Conclusions

The Heartmarker score is a reproducible and intuitive model for risk stratification of outpatients with HF, using routine biomarker measurements.

Can body position be arrhythmogenic?

INTRODUCTION

Palpitations occurring in specific body positions are often reported by patients, but the effect of body position on arrhythmia has received little research attention. We hypothesize that resting body position can exert pro-arrhythmogenic effects in various ways. For example, lateral body position is known to increase change atrial and pulmonary vein dimensions.

METHODS

This observational study capitalizes on overnight polysomnography (PSG) recordings from a tertiary sleep clinic. PSGs were retrieved based on any mention of cardiac arrhythmia in the clinical report, irrespective of primary sleep diagnosis or (cardiac) comorbidities. Every instance of atrial ectopy was annotated and subgroups with a homogenous rate of atrial ectopy were created based on the Dunn index. A generalized linear mixed-effects model using age, sex, gender, sleep stage and body position was used to analyse the total amount of atrial ectopy in each combination of sleep stage and body position. Backward elimination was then performed to select the best subset of variables for the model. Presence of a respiratory event was then added to the model for the subgroup with a high atrial ectopy rate.

RESULTS

PSGs of 22 patients (14% female, mean age 61y) were clustered and analysed. Body position, sleep stage, age or sex did not have a significant effect on atrial ectopy in the subgroup with a low rate of atrial ectopy (N = 18). However, body position did significantly affect the rate of atrial ectopy in the subgroup with a high rate of atrial ectopy (N = 4; 18%). Respiratory events significantly altered the atrial ectopy rate in only three body positions across two patients.

DISCUSSION

In each individual with a high rate of atrial ectopy, the rate of atrial ectopy was significantly higher in either left or right decubital or supine position. Increase in atrial wall stretch in lateral decubital position and obstructive respiratory events in positional sleep apnea are two possible pathophysiological mechanisms, while avoidance of a body position due to symptomatic atrial ectopy in that position is an important limitation.

CONCLUSION

In a selected cohort of patients with a high rate of atrial ectopy during overnight polysomnography, the occurrence of atrial ectopy is related to resting body position.

Left atrial remodeling in mitral regurgitation: A combined experimental-computational study

Aims

Progressive changes to left atrial (LA) structure and function following mitral regurgitation (MR) remain incompletely understood. This study aimed to demonstrate potential underlying mechanisms using experimental canine models and computer simulations.

Methods

A canine model of MR was created by cauterization of mitral chordae followed by radiofrequency ablation-induced left bundle-branch block (LBBB) after 4 weeks (MR-LBBB group). Animals with LBBB alone served as control. Echocardiography was performed at baseline, acutely after MR induction, and at 4 and 20 weeks, and correlated with histology and computer simulations.

Results

Acute MR augmented LA reservoir and contractile strain (40±4 to 53±6% and -11±5 to -22±9% respectively, p<0.05). LA fractional area change increased significantly (47±4 to 56±4%, p<0.05) while LA end-systolic area remained unchanged (7.2±1.1 versus 7.9±1.1 cm2 respectively, p = 0.08). LA strain ‘pseudonormalized’ after 4 weeks and decompensated at 20 weeks with both strains decreasing to 25±6% and -3±2% respectively (p<0.05) together with a progressive increase in LA end-systolic area (7.2±1.1 to 14.0±6.3 cm2, p<0.05). In the LBBB-group, LA remodeling was less pronounced. Histology showed a trend towards increased interstitial fibrosis in the LA of the MR-LBBB group. Computer simulations indicated that the progressive changes in LA structure and function are a combination of progressive eccentric remodeling and fibrosis.

Conclusion

MR augmented LA strain acutely to supranormal values without significant LA dilation. However, over time, LA strain gradually decreases (pseudornormal and decompensated) with LA dilation. Histology and computer simulations indicated a correlation to a varying degree of LA eccentric remodeling and fibrosis.

Epicardial adipose tissue, obesity and the occurrence of atrial fibrillation: an overview of pathophysiology and treatment methods

INTRODUCTION

Obesity is a chronic disease, which has significant health consequences and is a staggering burden to health care systems. Obesity can have harmful effects on the cardiovascular system, including heart failure, hypertension, coronary heart disease, and atrial fibrillation (AF). One of the possible substrates might be epicardial adipose tissue (EAT), which can be the link between AF and obesity. EAT is a fat deposit located between the myocardium and the visceral pericardium. Numerous studies have demonstrated that EAT plays a pivotal role in this relationship regarding atrial fibrillation.

AREAS COVERED

This review will focus on the role of obesity and the occurrence of atrial fibrillation (AF) and examine the connection between these and epicardial adipose tissue (EAT). The first part of this review will explain the pathophysiology of EAT and its association with the occurrence of AF. Secondly, we will review bariatric and metabolic surgery and its effects on EAT and AF.

EXPERT COMMENTARY

In this review, the epidemiology, pathophysiology, and treatments methods of AF are explained. Secondly the effects on EAT were elucidated. Due to the complex pathophysiological link between EAT, AF, and obesity, it is still uncertain which treatment strategy is superior.

Left atrial reservoir strain as a predictor of cardiac outcome in patients with heart failure: the HaFaC cohort study

BACKGROUND

The left atrium (LA) is a key player in the pathophysiology of systolic and diastolic heart failure (HF). Speckle tracking derived LA reservoir strain (LAS_r) can be used as a prognostic surrogate for elevated left ventricular filling pressure similar to NT-proBNP. The aim of the study is to investigate the correlation between LAS_r and NT-proBNP and its prognostic value with regards to the composite endpoint of HF hospitalization and all-cause mortality within 1 year.

METHODS

Outpatients, sent to the echocardiography core lab because of HF, were enrolled into this study. Patients underwent a transthoracic echocardiographic examination, commercially available software was used to measure LAS_r. Blood samples were collected directly after the echocardiographic examination to determine NT-proBNP.

RESULTS

We included 174 HF patients, 43% with reduced, 36% with mildly reduced, and 21% with preserved ejection fraction. The study population showed a strong inverse correlation between LAS_r and log-transformed NT-proBNP (r = - 0.75, p < 0.01). Compared to NT-proBNP, LAS_r predicts the endpoint with a comparable specificity (83% vs. 84%), however with a lower sensitivity (70% vs. 61%).

CONCLUSION

LAS_r is inversely correlated with NT-proBNP and a good echocardiographic predictor for the composite endpoint of hospitalization and all-cause mortality in patients with HF.

TRIAL REGISTRATION

https://www.trialregister.nl/trial/7268.

Effects of Bariatric Surgery on Heart Rhythm Disorders: a Systematic Review and Meta-Analysis

The aim of this systematic review is to provide an overview of the literature on the effects of bariatric surgery on obesity-associated electrocardiogram (ECG) abnormalities and cardiac arrhythmias. Fourteen studies were included with a methodological quality ranging from poor to good. Majority of the studies showed a significant decrease of QT interval and related measures after bariatric surgery. Seven studies were included in the meta-analysis on effects of bariatric surgery on QTc interval and a significant decrease in QTc interval of - 33.6 ms, 95%CI [- 49.8 to - 17.4] was seen. Bariatric surgery results in significant decrease in QTc interval and P-wave dispersion, i.e., a normalization of initial pathology. The effects on atrial fibrillation are conflicting and not yet fully understood.

Early or Delayed Cardioversion in Recent-Onset Atrial Fibrillation

BACKGROUND

Patients with recent-onset atrial fibrillation commonly undergo immediate restoration of sinus rhythm by pharmacologic or electrical cardioversion. However, whether immediate restoration of sinus rhythm is necessary is not known, since atrial fibrillation often terminates spontaneously.

METHODS

In a multicenter, randomized, open-label, noninferiority trial, we randomly assigned patients with hemodynamically stable, recent-onset (<36 hours), symptomatic atrial fibrillation in the emergency department to be treated with a wait-and-see approach (delayed-cardioversion group) or early cardioversion. The wait-and-see approach involved initial treatment with rate-control medication only and delayed cardioversion if the atrial fibrillation did not resolve within 48 hours. The primary end point was the presence of sinus rhythm at 4 weeks. Noninferiority would be shown if the lower limit of the 95% confidence interval for the between-group difference in the primary end point in percentage points was more than -10.

RESULTS

The presence of sinus rhythm at 4 weeks occurred in 193 of 212 patients (91%) in the delayed-cardioversion group and in 202 of 215 (94%) in the early-cardioversion group (between-group difference, -2.9 percentage points; 95% confidence interval [CI], -8.2 to 2.2; P = 0.005 for noninferiority). In the delayed-cardioversion group, conversion to sinus rhythm within 48 hours occurred spontaneously in 150 of 218 patients (69%) and after delayed cardioversion in 61 patients (28%). In the early-cardioversion group, conversion to sinus rhythm occurred spontaneously before the initiation of cardioversion in 36 of 219 patients (16%) and after cardioversion in 171 patients (78%). Among the patients who completed remote monitoring during 4 weeks of follow-up, a recurrence of atrial fibrillation occurred in 49 of 164 patients (30%) in the delayed-cardioversion group and in 50 of 171 (29%) in the early-cardioversion group. Within 4 weeks after randomization, cardiovascular complications occurred in 10 patients and 8 patients, respectively.

CONCLUSIONS

In patients presenting to the emergency department with recent-onset, symptomatic atrial fibrillation, a wait-and-see approach was noninferior to early cardioversion in achieving a return to sinus rhythm at 4 weeks. (Funded by the Netherlands Organization for Health Research and Development and others; RACE 7 ACWAS ClinicalTrials.gov number, NCT02248753.).

Cardiac structure and function before and after bariatric surgery: a clinical overview

Obesity, defined as a body mass index of ≥30 kg/m² , is the most common chronic metabolic disease worldwide and its prevalence has been strongly increasing. Obesity has deleterious effects on cardiac function. The purpose of this review is to evaluate the effects of obesity and excessive weight loss due to bariatric surgery on cardiac function, structural changes and haemodynamic responses of both the left and right ventricle.

[Differential diagnosis in patients with suspected anoxic-ischaemic coma]

Three case studies illustrate that suspected anoxic-ischaemic coma often requires careful differential diagnosis to detect treatable conditions. A 47-year-old man underwent cardiopulmonary resuscitation for ventricular fibrillation caused by myocardial ischaemia. He exhibited rhythmic eyelid movements while in a coma. Epilepsy was suspected, and the patient regained consciousness after being treated with antiepileptic drugs. A 34-year-old man underwent cardiopulmonary resuscitation for multiple episodes of ventricular fibrillation. Treatment was directed toward myocardial ischaemia and included anticoagulants. The patient had bilateral, fixed dilated pupils. A CT of the brain showed traumatic contrecoup haemorrhage in the left temporal lobe with signs of transtentorial herniation. The patient died. A 74-year-old woman was found unconscious at home. An ECG performed by the paramedics showed ST segment elevation in the precordial leads. Anoxic-ischaemic coma following cardiac arrest was suspected. However, a coronary angiogram was normal and a CT of the brain revealed subarachnoid haemorrhage caused by a ruptured intracranial aneurysm. She recovered after cranial surgery.

Arrhythmogenesis in heart failure

In a rabbit model of heart failure produced by combined pressure and volume overload, nonsustained ventricular tachycardias developed in 15 of 23 failing rabbits. Sinus rate was increased in rabbits dying suddenly, but was decreased in survivors. This also was true in isolated preparations. Microelectrode recordings from ventricular trabeculae both from patients with end-stage failure and from failing rabbits showed that in half of the preparations, delayed afterdepolarizations and triggered activity occurred, but only in the presence of norepinephrine and a lowered extracellular K+ concentration of 3 mM. This was due to spontaneous release of Ca2+ from the sarcoplasmic reticulum.

Florid opioid withdrawal-like reaction precipitated by naltrexone in a patient with chronic cholestasis

Findings consistent with the hypothesis that increased central opioidergic tone contributes to the pruritus of cholestasis provide a rationale for treating this form of pruritus with opiate antagonists. However, initiation of therapy with an opiate antagonist in a cholestatic patient may precipitate a transient opioid withdrawal-like reaction. A woman with chronic cholestasis and disabling pruritus experienced severe transient opioid withdrawal-like reactions after oral administration of 12.5 and 2 mg naltrexone. Subsequently, naloxone was administered by intravenous infusion. Initially, the infusion rate was low and subtherapeutic. It was gradually increased to a rate known to be effective in inducing opioid antagonism. Oral naltrexone was then reintroduced without any reaction occurring. During the ensuing 12 months, while taking naltrexone, 25 mg daily, the patient has been completely free from pruritus. These observations strongly support the hypothesis that increased central opioidergic tone is a component of the pathophysiology of cholestasis.

Intracellular Ca2+ and delay of ischemia-induced electrical uncoupling in preconditioned rabbit ventricular myocardium

OBJECTIVE

Short periods of ischemia and reperfusion alter myocardial Ca2+ handling and temporarily induce a mild increase of [Ca2+]i. We hypothesized that these alterations are involved in the cardioprotective mechanism of ischemic preconditioning, possibly via a Ca(2+)-dependent activation of protein kinase C (PKC).

METHODS AND RESULTS

In arterially perfused rabbit papillary muscles, we determined Ca2+ transients (indo 1) and indicators of the onset of irreversible ischemic damage, including [Ca2+]i rise, electrical uncoupling and contracture. We tested three protocols of ischemic preconditioning (1-3). In addition, the effects of infusion of staurosporine, a blocker of PKC (4), or glibenclamide, a blocker of K+ATP channels (5) were analyzed. Furthermore, pretreatment with phorbol 12-myrisate 13-acetate (PMA), an activator of PKC (6), or cyclopiazonic acid (CPA), an inhibitor of the SR Ca2+ pump (7) was tested. During periods of reperfusion in the preconditioning protocols, the duration of the Ca2+ transient and the diastolic Ca2+ level temporarily increased. Only if sustained ischemia was induced during these changes of the transients, cardioprotection was present. Similar alterations of the Ca2+ transient concurring with cardioprotection were induced by pretreatment with PMA as well as CPA. Staurosporine and glibenclamide antagonized the reperfusion-induced changes of the Ca2+ transients as well as cardioprotection. If reperfusion was extended until the Ca2+ transient had normalized, cardioprotection was also absent. Under all conditions tested, the diastolic Ca2+ elevation or the Ca2+ transient prolongation prior to sustained ischemia correlated with the postponement of ischemic injury.

CONCLUSIONS

A pre-ischemic mild increase of [Ca2-]i presents a common effector of preconditioning. Our data suggest that activation of PKC or opening of K+ATP channels may initiate the pathway leading to an alteration of Ca2+ metabolism and a protected status of the myocardium.

Cellular uncoupling during ischemia in hypertrophied and failing rabbit ventricular myocardium: effects of preconditioning

BACKGROUND

Patients with heart failure show a very high incidence of arrhythmias and sudden death that is often preceded by ischemia; however, data on electrophysiological changes during ischemia in failing myocardium are sparse. We studied electrical uncoupling during ischemia in normal and failing myocardium.

METHODS AND RESULTS

Tissue resistance, intracellular Ca2+ concentration (Indo-1 fluorescence ratio), and mechanical activity were simultaneously determined in arterially perfused right ventricular papillary muscles from 11 normal and 15 failing rabbits. Heart failure was induced by combined volume and pressure overload. Before sustained ischemia, muscles were subjected to control perfusion (non-PC) or ischemic preconditioning (PC). The onset of uncoupling during ischemia was equal in non-PC normal (13.6+/-0.9 minutes of ischemia) and non-PC failing hearts (13.3+/-0.7 minutes of ischemia). PC postponed uncoupling in normal hearts by 10 minutes. In failing hearts, however, PC caused a large variability in the onset of uncoupling during ischemia (mean, 12.2+/-2.1; range, 5 to 22 minutes of ischemia). The duration of uncoupling process was prolonged in failing hearts (12.9+/-0.9 minutes) compared with normal hearts (7.8+/-0.4 minutes). The degree of heart failure and relative heart weight of the failing hearts significantly correlated with the earlier uncoupling after PC and the duration of uncoupling. In every experiment, the start of Ca2+ rise and contracture preceded uncoupling during ischemia.

CONCLUSIONS

The duration of the process of ischemia-induced electrical uncoupling in failing hearts is prolonged compared with that in normal hearts. Ischemic PC has detrimental effects in severely failing papillary muscles because it advances the moment of irreversible ischemic damage.

Intracellular Ca2+, intercellular electrical coupling, and mechanical activity in ischemic rabbit papillary muscle. Effects of preconditioning and metabolic blockade

During myocardial ischemia, electrical uncoupling and contracture herald irreversible damage. In the present study, we tested the hypothesis that an increase of intracellular Ca2+ is an important factor initiating these events. Therefore, we simultaneously determined tissue resistance, mechanical activity, pH(0), and intracellular Ca2+ (with the fluorescent indicator indo 1, Molecular Probes, Inc) in arterially perfused rabbit papillary muscles. Sustained ischemia was induced in three experimental groups: (1) control, (2) preparations preconditioned with two 5-minute periods of ischemia followed by reperfusion, and (3) preparations pretreated with 1 mmol/L iodoacetate to block anaerobic metabolism and minimize acidification during ischemia. In a fourth experimental group, intracellular Ca2+ was increased under nonischemic conditions by perfusing with 0.1 mmol/L ionomycin and 0.1 mumol/L gramicidin. Ca2+ transients and contractions rapidly disappeared after the induction of ischemia. In the control group, diastolic Ca2+ began to rise after 12.6 +/- 1.3 minutes of ischemia; uncoupling, after 14.5 +/- 1.2 minutes of ischemia; and contracture, after 12.6 +/- 1.5 minutes of ischemia (mean +/- SEM). Preconditioning significantly postponed Ca2+ rise, uncoupling, and contracture (21.5 +/- 4.0, 24.0 +/- 4.1, and 23.0 +/- 5.3 minutes of ischemia, respectively). Pretreatment with iodoacetate significantly advanced these events (1.9 +/- 0.7, 3.6 +/- 0.9, and 1.9 +/- 0.2 minutes of ischemia, respectively). In all groups, the onset of uncoupling always followed the start of Ca2+ rise, whereas the start of contracture was not different from the rise in Ca2+. Perfusion with ionomycin and gramicidin permitted estimation of a threshold [Ca2+] for electrical uncoupling of 685 +/- 85 nmol/L. In conclusion, the rise in intracellular Ca2+ is the main trigger for cellular uncoupling during ischemia. Contracture is closely associated with the increase of intracellular Ca2+ during ischemia.

Heterogeneities in [K+]o and TQ potential and the inducibility of ventricular fibrillation during acute regional ischemia in the isolated perfused porcine heart

BACKGROUND

The relation between the inducibility of ventricular fibrillation (VF) and heterogeneity of the extracellular potassium concentration ([K+]o) and of TQ potential is unknown.

METHODS AND RESULTS

Data from 78 epicardial DC electrodes or from up to 32 intramural K+ electrodes were acquired simultaneously. Induction of VF was attempted with one or two ventricular premature beats induced in normal myocardium in isolated porcine hearts during (1) regional perfusion of the left anterior descending artery (LAD) with a normoxic, hyperkalemic solution ([K+] 6 to 19.6 mmol/L), (2) simulated ischemia, ie, LAD perfusion with a glucose-free, hypoxic solution ([K+] 4 to 16 mmol/L, PO2 < 5 mm Hg, pH 6.98), and (3) regional ischemia produced by stopping LAD flow. During normoxic, hyperkalemic LAD perfusion, no VF could be induced (12 interventions, 7 hearts). During simulated ischemia (27 interventions), VF could be induced only when [K+]o was between 8 and 13.5 mmol/L. After 5 minutes of true regional ischemia, more sites with [K+]o between 8 and 13.5 mmol/L were present than after 10 minutes. VF could be induced with 1 ventricular premature beat in 11 of 17 interventions after 5 minutes and in 0 of 14 interventions after 10 minutes of ischemia (P < .001). Regional simulated ischemia presents a relatively homogeneous condition compared with 5 minutes of regional ischemia (SD +/- SEM of TQ potential in LAD tissue, 0.9 +/- 0.05 versus 2.1 +/- 0.13 mV, respectively). True ischemia superimposed on regional simulated ischemia caused the rapid development of heterogeneities in [K+]o and TQ potential and caused VF after 45 +/- 7 seconds in all interventions. Activation maps of induction of VF suggest a different mechanism of unidirectional block during simulated ischemia from that in true ischemia.

CONCLUSIONS

(1) In the presence of hypoxia and acidosis, [K+]o between 8 and 13.5 mmol/L provides the conditions necessary for the induction of VF; (2) after 5 minutes of ischemia, these conditions are present in a larger area and inducibility of VF is higher than after 10 minutes of ischemia; and (3) small heterogeneities within the intermediate K(+)-concentration domain (8 to 13.5 mmol/L) are associated with high inducibility of VF.

Interaction of sympathetic and parasympathetic nervous system on ventricular refractoriness assessed by local fibrillation intervals in the canine heart

OBJECTIVE

The aim was to assess the effects of autonomic nerve stimulation on local ventricular refractoriness by measuring local ventricular fibrillation intervals.

METHODS

In 10 dogs on cardiopulmonary bypass, ventricular fibrillation intervals were recorded simultaneously at up to 32 sites before and after neural stimulation. In four dogs (group 1) the response to bilateral stellate ganglion stimulation was measured before and after bilateral cervical vagotomy. In three dogs (group 2) bilateral stellate ganglion stimulation, vagal nerve stimulation, and combined vagal and stellate ganglia stimulation were performed. In three dogs (group 3) the same protocol was applied after total decentralisation of the autonomic nervous system.

RESULTS

Bilateral stellate ganglion stimulation shortened the ventricular fibrillation interval at 44-50% of myocardial sites before and after vagotomy, whereas prolongation of the interval was observed at 14-18% of the sites. At higher stimulus strength shortening of the interval was measured at 85% of the sites in the intact and decentralised groups. No prolongation was observed. The shortening was largest in the decentralised group (11.1 ms). Dispersion in refractoriness increased in hearts from all groups, but not in each individual heart. Left, right, or bilateral vagal stimulation was without effect at about 75% of the tested sites. The fact that the response to autonomic nerve stimulation varies from site to site warrants our approach of simultaneous recordings at multiple sites. Dispersion in refractoriness was not affected by vagal stimulation. Combined autonomic stimulation had approximately the same effect on dispersion in refractoriness as bilateral stellate ganglion stimulation alone. However, vagal stimulation attenuated the responses to bilateral stellate ganglion stimulation by some 20% in the decentralised group.

CONCLUSIONS

Vagal stimulation has minor effects on ventricular refractoriness, but this is not due to sparse innervation, since vagal stimulation is able to mitigate the effects of sympathetic stimulation in decentralised hearts.