QT dispersion in mild cognitive impairment: a possible tool for predicting the risk of progression to dementia?

Relationship between Alzheimer dementia and QT interval: A meta-analysis

While the link between aging and mortality from dementia is widely appreciated, the mechanism is not clear. The objective of this study was to determine whether there is a direct relationship between Alzheimer dementia (AD) and the QT interval, because the latter has been related to cardiac mortality. A systematic review and meta-analysis were conducted after a Medline and EMBASE search using terms "Alzheimer disease or Dementia AND QT interval, QT dispersion or cardiac repolarization." Four studies with control groups were identified. There were significant differences in QT interval between individuals with AD vs individuals without dementia (controls) (odds ratio (OR)1.665 [random effects model] and 1.879 [fixed effect model]) (p < 0.001). There were significant differences in QT interval between individuals with AD vs individuals with mild cognitive impairment (MCI) (OR 1.760 [random effects] and 1.810 [fixed effect]) (p < 0.001). A significant (p <0.001) correlation exists between the QTc and the Mini-Mental State Exam (MMSE), a test of cognitive function. Two studies examined QT variability (the difference between the longest and shortest QT interval on a 12 lead ECG); the OR for QT variability AD vs MCI was 3.858 [random effects model] and 3.712 [fixed effects model] (p < 0.001). When compared to the control group, the OR for QT dispersion in AD was 6.358 [random effects model] or 5.143 ( P< 0.001) [fixed effects model]. A qualitative analysis of the data raised questions about paucity of data defining the nature of the control groups, the pathophysiologic mechanism, and the uniform use of a poor QT heart rate correction factor. The longer QT in AD, greater QT variability in AD, and the direct relationship between QT interval and AD severity supports a brain-heart connection in AD that might be fundamental to aging-induced AD and mortality. Issues with defining the control group, limited number of studies, conflicting data in population studies, and the lack of a strong electrophysiological basis underscore the need for additional research in this field.

Ventricular Electrocardiographic Signatures Associated with Dementia and Plasma Alzheimer's Disease Biomarkers in Older Adults: A Population-Based Study

BACKGROUND

Evidence has emerged that altered ventricular electrocardiogram profiles are associated with dementia, but the neuropathological mechanisms underlying their associations are poorly understood.

OBJECTIVE

To investigate the interrelationships of ventricular electrocardiogram profiles with dementia and plasma Alzheimer's disease (AD) biomarkers among older adults.

METHODS

This population-based cross-sectional study included 5,153 participants (age ≥65 years; 57.3% women) living in rural communities in China; of these, 1,281 had data on plasma amyloid-β (Aβ)40, Aβ42, total-tau, and neurofilament light chain (NfL) protein. The QT, QTc, JT, JTc, QRS intervals, and QRS axis were derived from the 10-second electrocardiogram recording. The DSM-IV criteria were followed for clinical diagnosis of dementia, the NIA-AA criteria for AD, and the NINDS-AIREN criteria for vascular dementia (VaD). Data were analyzed using general linear models, multinomial logistic models, and restricted cubic splines.

RESULTS

Of the 5,153 participants, 299 (5.8%) were diagnosed with dementia, including 194 with AD and 94 with VaD. Prolonged QT, QTc, JT, and JTc intervals were significantly associated with all-cause dementia, AD, and VaD (p < 0.05). Left QRS axis deviation was significantly associated with all-cause dementia and VaD (p < 0.01). In the subsample of plasma biomarkers (n = 1,281), prolonged QT, JT, and JTc intervals were significantly associated with a lower Aβ42/Aβ40 ratio and higher plasma NfL concentrations (p < 0.05).

CONCLUSION

Alterations in ventricular repolarization and depolarization are independently associated with all-cause dementia, AD, VaD, and AD plasma biomarkers in older adults (age ≥65 years). Ventricular electrocardiogram parameters may be valuable clinical markers for dementia and the underlying AD pathologies and neurodegeneration.

Effects of Alzheimer's disease of varying severity on cardiac and autonomic function

Alzheimer’s disease (AD) is one of the most common neurodegenerative diseases in the elderly. The aim of this study was to explore the effects of AD on cardiac function and autonomic nervous function, and the feasibility of electrocardiogram (ECG) in monitoring the development of AD. APP/PS1 double transgenic mice were used in the Morris water maze (MWM) experiment to evaluate the changes of cognitive ability of AD mice, then the non-invasive ECG acquisition system was used and the changes of ECG intervals and heart rate variability (HRV) were analyzed. AD mice already had cognitive dysfunction at the age of 5 months, reaching the level of mild dementia, and the degree of dementia increased with the course of disease. There were no significant changes in ECG intervals in the AD group at each month. The mean square of successive RR interval differences, percentage of intervals >6 ms different from preceding interval, and normalized high frequency power component in the AD group were decreased and low-to-high frequency power ratio and normalized low frequency power component were increased. Combined with the results of the MWM, it was shown that the regulation mechanism of sympathetic and parasympathetic nerves in mice was already imbalanced in early stage AD, which was manifested as the increase of excessive activity of sympathetic nerves and the inhibition of parasympathetic activities. Therefore, ECG-based analysis of HRV may become a means of daily monitoring of AD and provide an auxiliary basis for clinical diagnosis.

Electrocardiographic Predictors of Cognitive Decline and Dementia: A Systematic Review

BACKGROUND

Markers of altered cardiac function might predict cognitive decline and dementia.

OBJECTIVE

This systematic review aims to review the literature that examines the associations of various electrocardiogram (ECG) markers with cognitive decline and dementia in middle-aged and elderly populations.

METHODS

We searched PubMed, Embase, and Web of Science through 1 July 2020 for literature and conducted a systematic literature review. We included studies examining the associations of ECG markers (e.g., left ventricular hypertrophy [LVH], spatial QRS-T angle, and QT prolongation) with cognitive function and dementia in adult populations regardless of study setting and design, but excluded studies examining atrial fibrillation and heart rate variability.

RESULTS

Fourteen community-based cross-sectional and longitudinal studies were identified. ECG markers were investigated in association with dementia in four prospective studies, and with cognitive decline in ten prospective studies. ECG-assessed LVH was associated with dementia in one study while five heterogeneous prospective studies yielded inconsistent associations with cognitive decline. Regarding ventricular repolarization markers, spatial QRS-T angle was associated with cognitive decline in one study while another study found no association between QT prolongation and cognitive decline. High resting heart rate was associated with both dementia and cognitive decline in one study but not associated with dementia in another study. P-wave abnormality was significantly associated with incident dementia and cognitive decline in one prospective study.

CONCLUSION

Some ECG markers were associated with incident dementia and cognitive decline. However, limited number of heterogeneous studies did not allow us to make firm conclusions. Further studies are needed.

Cardiac electrical remodeling and neurodegenerative diseases association

Cardiac impairment contributes significantly to the mortality associated with several neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD), primarily recognized as brain pathologies. These diseases may be caused by aggregation of a misfolded protein, most often, in the brain, although new evidence also reveals peripheral abnormalities. After characterization of the cardiac involvement in neurodegenerative diseases, several studies concentrated on elucidating the cause of the impaired cardiac function. However, most of the current knowledge is focused on the mechanical aspects of the heart rather than the electrical disturbances. The main objective of this review is to summarize the most recent advances in the elucidation of cardiac electrical remodeling in the neurodegenerative environment. We aimed to determine a crosstalk between the heart and the brain in three neurodegenerative conditions: AD, PD, and HD. We found that the most studies demonstrated important alterations in the electrocardiogram (ECG) of patients with neurodegeneration and in animal models of the conditions. We also showed that little is described when considering excitability disruptions in cardiomyocytes, for example, action potential impairments. It is a matter of contention whether central nervous system abnormalities or the peripheral ones increase the risk of heart diseases in patients with neurodegenerative conditions. To determine this notion, there is a need for new heart studies focusing specifically on the cardiac electrophysiology (e.g., ECG and cardiomyocyte excitability). This review could serve as an important guide in designing novel accurate approaches targeting the heart in neuronal conditions.

QTc Prolongation in Patients with Dementia and Mild Cognitive Impairment: Neuropsychological and Brain Imaging Correlations

The QTc interval is the electrocardiographic manifestation of ventricular depolarization and repolarization. This marker is often prolonged in acute and chronic neurological conditions. The cause of the cerebrogenic QT prolongation remains unclear. The aim of the study was to analyze the relation between QTc interval and the degree of cognitive impairment and structural brain imaging changes in patients with dementia and mild cognitive impairment (MCI). To this aim, 269 patients were screened, of whom 61 met one or more exclusion criteria. The remaining 208 patients (56 control subjects, 44 patients with MCI, and 108 with dementia) were recruited. Eighty-five patients using drugs causing prolongation of QT interval were further excluded. The QT interval was measured manually in all 12 leads by a single blinded observer, assuming the longest QT value adjusted for heart rate by using the Bazett's formula. All patients underwent a structural brain imaging and the following measures were obtained: the bicaudate ratio and the periventricular hyperintensity and deep white matter hyperintensity using the modified Fazekas scale. Prolonged QTc interval was prevalent in 1) patients with dementia, especially in those with moderate-severe degree; 2) subjects with impairment of praxis and attention, low functional status, and behavioral symptoms; 3) patients with global and temporal atrophy and with higher scores on the Fazekas or leukoaraiosis scales. Degenerative and vascular processes might play a main role in QTc interval prolongation because of the damage to brain areas involved in the control of the autonomic cardiac nervous system.

Mind the Rhythm: ECG QT Dispersion and Cognition in Healthy Older Adults

Background

Autonomic function has been linked to cognitive abilities in aging. Even in non-clinical states, a certain variability in heart rhythm regulation can be measured with QT dispersion (QTcD), an ECG marker of ventricular repolarization which has been linked to autonomic function and cardiovascular health. QTcD has been shown to be higher in individuals with mild cognitive impairment, and the highest in individuals with Alzheimer’s disease. The goal of this study was to see if QTcD is associated with cognitive performance in healthy individuals.

Methods

Sixty-three healthy inactive older adults (> 60 years) completed an extensive cognitive assessment (including inhibition, divided attention, updating, working memory, and processing speed), a physical fitness assessment, and underwent a resting ECG.

Results

After controlling for age, sex, and education, QTcD significantly predicted global cognition (MoCA) scores (R² = 0.17, F_(4.58) = 3.00, p < 0.03, β = −0.36). Exploratory analysis on the MoCA subcomponents revealed a significant association between the visual/executive subcomponent and QTcD (R² = 0.12, F_(1.61) = 7.99, p < 0.01, β = −0.34). In individuals with high QTcD, QTcD values were linked to executive functions (R² = 0.37), processing speed (R² = 0.34), and dual-task performances (R² = 0.47). No significant associations were found within the low QTcD group.

Conclusion

This study shows an association between ventricular repolarization (QTcD) and cognitive performance, in particular speed and executive functions, in healthy older adults. The results provide further support for linking autonomic heart regulation and age-related cognitive changes, and suggest that deviations on ECG, even within-normal range, could help detect early cognitive deficits.

Ventricular Repolarization is Associated with Cognitive Function, but Not with Cognitive Decline and Brain Magnetic Resonance Imaging (MRI) Measurements in Older Adults

We aimed to investigate the cross-sectional and longitudinal associations of electrocardiogram (ECG)-based QT, QTc, JT, JTc, and QRS intervals with cognitive function and brain magnetic resonance imaging (MRI) measurements in a cohort of older individuals at increased risk for cardiovascular disease, but free of known arrhythmias. We studied 4627 participants (54% female, mean age 75 years) enrolled in the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER). Ten-second ECGs were conducted at baseline. Cognitive function was tested at baseline and repeated during a mean follow-up time of 3.2 years. Structural MRIs were conducted in a subgroup of 535 participants. Analyses were performed with multivariable (repeated) linear regression models and adjusted for cardiovascular risk-factors, co-morbidities, and cardiovascular drug use. At baseline, longer QT, JT, JTc—but not QTc and QRS intervals—were associated with a worse cognitive performance. Most notably, on the Stroop Test, participants performed 3.02 (95% CI 0.31; 5.73) seconds worse per standard deviation higher QT interval, independent of cardiovascular risk factors and medication use. There was no association between longer ventricular de- or repolarization and structural brain measurements. Therefore, specifically ventricular repolarization was associated with worse cognitive performance in older individuals at baseline but not during follow-up.

Incident prolonged QT interval in midlife and late-life cognitive performance

BACKGROUND

Measures of cardiac ventricular electrophysiology have been associated with cognitive performance in cross-sectional studies. We sought to evaluate the association of worsening ventricular repolarization in midlife, as measured by incident prolonged QT interval, with cognitive decline in late life.

METHODS

Midlife QT interval was assessed by electrocardiography during three study visits from 1965/68 to 1971/74 in a cohort of Japanese American men aged 46-68 at Exam 1 from the Honolulu Heart Study. We defined incident prolonged QT as the QT interval in the upper quartile at Exam 2 or 3 after QT interval in lower three quartiles at Exam 1. Cognitive performance was assessed at least once using the Cognitive Abilities Screening Instrument (CASI), scored using item response theory (CASI-IRT), during four subsequent visits from 1991/93 to 1999/2000 among 2,511 of the 4,737 men in the Honolulu-Asia Aging Study otherwise eligible for inclusion in analyses. We used marginal structural modeling to determine the association of incident prolonged QT with cognitive decline, using weighting to account for confounding and attrition.

RESULTS

Incident prolonged QT interval in midlife was not associated with late-life CASI-IRT at cognitive baseline (estimated difference in CASI-IRT: 0.04; 95% CI: -0.28, 0.35; p = 0.81), or change in CASI-IRT over time (estimated difference in annual change in CASI-IRT: -0.002; 95%CI: -0.013, 0.010; p = 0.79). Findings were consistent across sensitivity analyses.

CONCLUSIONS

Although many midlife cardiovascular risk factors and cardiac structure and function measures are associated with late-life cognitive decline, incident prolonged QT interval in midlife was not associated with late-life cognitive performance or cognitive decline.

Highlights in clinical autonomic neurosciences: Brain volume and autonomic regulation

Advances in volumetric magnetic resonance imaging (MRI) technology are beginning to provide structural correlates to functional dysautonomic syndromes in the brain. This paper highlights several interesting recent discoveries in which measurable variations in general or regional subcortical or cortical brain volume corresponded to changes in blood pressure or heart rate. Although these MRI findings currently lack diagnostic value in routine clinical practice, they may provide important clues to the pathophysiology of autonomic disorders and to links between autonomic and cognitive disorders. If validated by further studies, they also have potential implications for the management of orthostatic hypotension, particularly when combined with hypertension.