Metabolic Activity in Central Neural Structures of Patients With Myocardial Injury

Cerebral hypometabolism mediates the effect of stroke volume on cognitive impairment in heart failure patients

AIMS

The present study aimed to phenotype the cerebral structural and glucose metabolic alterations in patients with heart failure (HF) using simultaneous positron emission tomography (PET)/magnetic resonance (MR) and to investigate their relationship to cardiac biomarkers and cognitive performance.

METHODS AND RESULTS

Forty-two HF patients caused by ischaemic heart disease (mean age 67.2 ± 10.4, 32 males) and 32 age- and sex-matched healthy volunteers (mean age 61.3 ± 4.8, 18 males) were included in this study. Participants underwent simultaneous cerebral fluorine-18 (18 F) fluorodeoxyglucose PET/MR followed by cardiac MR scan, and neuropsychological scores were obtained to assess cognitive performance. The grey matter volume (GMV) and standardized uptake value ratio (SUVR) were calculated to examine cerebral structural and metabolic alterations. Cardiac biomarkers included cardiac MR parameters and cardiac serum laboratory tests. Mediation analysis was performed to explore the associations among cerebral alterations, cardiac biomarkers, and cognitive performance. HF patients demonstrated notable cognitive impairment compared with normal controls (P < 0.001). Furthermore, HF patients exhibited regional brain hypometabolism in the bilateral calcarine cortex, caudate nucleus, thalamus, hippocampus, precuneus, posterior cingulate cortex, lingual and olfactory cortex, and GMV reduction in bilateral thalamus and hippocampus (cluster level at P < 0.05, Gaussian random field correction). The SUVR of the hypometabolic brain regions was correlated with the Montreal Cognitive Assessment (MoCA) scores (r = 0.55, P = 0.038) and cardiac stroke volume (r = 0.49, P = 0.002). Cerebral hypometabolism played a key role in the relationship between the decreased stroke volume and MoCA scores, with a mediation effect of 33.2%.

CONCLUSIONS

HF patients suffered cerebral metabolic and structural alterations in regions associated with cognition. The observed correlation between cardiac stroke volume and cognitive impairment underscored the potential influence of cerebral hypometabolism, suggesting that cerebral hypometabolism due to chronic systemic hypoperfusion may significantly contribute to cognitive impairment in HF patients.

Cardiac vagal afferent neurotransmission in health and disease: review and knowledge gaps

The meticulous control of cardiac sympathetic and parasympathetic tone regulates all facets of cardiac function. This precise calibration of cardiac efferent innervation is dependent on sensory information that is relayed from the heart to the central nervous system. The vagus nerve, which contains vagal cardiac afferent fibers, carries sensory information to the brainstem. Vagal afferent signaling has been predominantly shown to increase parasympathetic efferent response and vagal tone. However, cardiac vagal afferent signaling appears to change after cardiac injury, though much remains unknown. Even though subsequent cardiac autonomic imbalance is characterized by sympathoexcitation and parasympathetic dysfunction, it remains unclear if, and to what extent, vagal afferent dysfunction is involved in the development of vagal withdrawal. This review aims to summarize the current understanding of cardiac vagal afferent signaling under in health and in the setting of cardiovascular disease, especially after myocardial infarction, and to highlight the knowledge gaps that remain to be addressed.

Assessment of cerebral glucose metabolism in patients with heart failure by 18F-FDG PET/CT imaging

BACKGROUND

To evaluate the cerebral metabolism in patients with heart failure (HF).

METHODS

One hundred and two HF patients were prospectively enrolled, who underwent gated 99mTc-sestamibi single photon emission computed tomography (SPECT)/CT, cardiac and cerebral 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT. Fifteen healthy volunteers served as controls. Patients were stratified by extent of hibernating myocardium (HM) and left ventricular ejection fraction (LVEF) into 4 groups where Group1: HM < 10% (n = 33); Group2: HM ≥ 10%, LVEF < 25% (n = 34); Group3: HM ≥ 10%, 25% ≤ LVEF ≤ 40% (n = 16) and Group 4: LVEF > 40% (n = 19). The standardized uptake value (SUV) in the whole brain (SUVwhole-brain) and the SUV ratios (SUVR) in 24 cognition-related brain regions were determined. SUVwhole-brain and SUVRs were compared between the 4 patient groups and the healthy controls.

RESULTS

SUVwhole-brain (r = 0.245, P = 0.013) and SUVRs in frontal areas, hippocampus, and para-hippocampus (r: 0.213 to 0.308, all P < 0.05) were correlated with HM. SUVwhole-brain differed between four patient groups and the healthy volunteers (P = 0.016) and SUVwhole-brain in Group 1 was lower than that in healthy volunteers (P < 0.05). SUVRs of Group 3 in frontal areas were the highest among four patient subgroups (P < 0.05).

CONCLUSIONS

Cerebral metabolism in the whole brain was reduced but maintained in cognition-related frontal areas in HF patients with HM and moderately impaired global left ventricular function.

Metabolic Activity in Central Neural Structures of Patients With Myocardial Injury

Background

Increasing evidence suggests a psychosomatic link between neural systems and the heart. In light of the growing burden of ischemic cardiovascular disease across the globe, a better understanding of heart‐brain interactions and their implications for cardiovascular treatment strategies is needed. Thus, we sought to investigate the interaction between myocardial injury and metabolic alterations in central neural areas in patients with suspected or known coronary artery disease.

Methods and Results

The association between resting metabolic activity in distinct neural structures and cardiac function was analyzed in 302 patients (aged 66.8±10.2 years; 70.9% men) undergoing fluor‐18‐deoxyglucose positron emission tomography and ^99mTc‐tetrofosmin single‐photon emission computed tomography myocardial perfusion imaging. There was evidence for reduction of callosal, caudate, and brainstem fluor‐18‐deoxyglucose uptake in patients with impaired left ventricular ejection fraction (<55% versus ≥55%: P=0.047, P=0.022, and P=0.013, respectively) and/or in the presence of myocardial ischemia (versus normal perfusion: P=0.010, P=0.013, and P=0.016, respectively). In a sex‐stratified analysis, these differences were observed in men, but not in women. A first‐order interaction term consisting of sex and impaired left ventricular ejection fraction or myocardial ischemia was identified as predictor of metabolic activity in these neural regions (left ventricular ejection fraction: P=0.015 for brainstem; myocardial ischemia: P=0.004, P=0.018, and P=0.003 for callosal, caudate, or brainstem metabolism, respectively).

Conclusions

Myocardial dysfunction and injury are associated with reduced resting metabolic activity of central neural structures, including the corpus callosum, the caudate nucleus, and the brainstem. These associations differ in women and men, suggesting sex differences in the pathophysiological interplay of the nervous and cardiovascular systems.