Effect of Loss of Heart Rate Variability on T-Wave Heterogeneity and QT Variability in Heart Failure Patients: Implications in Ventricular Arrhythmogenesis

A Feasibility Open-Labeled Clinical Trial Using a Second-Generation Artificial-Intelligence-Based Therapeutic Regimen in Patients with Gaucher Disease Treated with Enzyme Replacement Therapy

Background/Objectives: Gaucher Disease type 1 (GD1) is a recessively inherited lysosomal storage disorder caused by a deficiency in the enzyme β-glucocerebrosidase. Enzyme replacement therapy (ERT) has become the standard of care for patients with GD. However, over 10% of patients experience an incomplete response or partial loss of response to ERT, necessitating the exploration of alternative approaches to enhance treatment outcomes. The present feasibility study aimed to determine the feasibility of using a second-generation artificial intelligence (AI) system that introduces variability into dosing regimens for ERT to improve the response to treatment and potentially overcome the partial loss of response to the enzyme. Methods: This was an open-label, prospective, single-center proof-of-concept study. Five patients with GD1 who received ERT were enrolled. The study used the Altus Care™ cellular-phone-based application, which incorporated an algorithm-based approach to offer random dosing regimens within a pre-defined range set by the physician. The app enabled personalized therapeutic regimens with variations in dosages and administration times. Results: The second-generation AI-based personalized regimen was associated with stable responses to ERT in patients with GD1. The SF-36 quality of life scores improved in one patient, and the sense of change in health improved in two; platelet levels increased in two patients, and hemoglobin remained stable. The system demonstrated a high engagement rate among patients and caregivers, showing compliance with the treatment regimen. Conclusions: This feasibility study highlights the potential of using variability-based regimens to enhance ERT effectiveness in GD and calls for further and longer trials to validate these findings.

Next-Generation Personalized Medicine: Implementation of Variability Patterns for Overcoming Drug Resistance in Chronic Diseases

Chronic diseases are a significant healthcare problem. Partial or complete non-responsiveness to chronic therapies is a significant obstacle to maintaining the long-term effect of drugs in these patients. A high degree of intra- and inter-patient variability defines pharmacodynamics, drug metabolism, and medication response. This variability is associated with partial or complete loss of drug effectiveness. Regular drug dosing schedules do not comply with physiological variability and contribute to resistance to chronic therapies. In this review, we describe a three-phase platform for overcoming drug resistance: introducing irregularity for improving drug response; establishing a deep learning, closed-loop algorithm for generating a personalized pattern of irregularity for overcoming drug resistance; and upscaling the algorithm by implementing quantified personal variability patterns along with other individualized genetic and proteomic-based ways. The closed-loop, dynamic, subject-tailored variability-based machinery can improve the efficacy of existing therapies in patients with chronic diseases.

Diabetes without Overt Cardiac Disease Is Associated with Markers of Abnormal Repolarization: A Case-Control Study

Patients with diabetes mellitus (DM) are prone to advanced atherosclerosis, microvascular disease, and tissue fibrosis. Despite the increased risk for arrhythmias, little is known about cardiac repolarization abnormalities in DM. We aimed to determine whether abnormal T-wave morphology markers are common among patients with DM and no known cardiac disease. Patients were recruited and classified as having DM or impaired fasting glucose (IFG) according to accepted guidelines. Total cosine R to T (TCRT) and T-wave morphology dispersion (TMD) were computed with custom-designed software for randomly selected and averaged beats. Among 124 patients recruited; 47 were diagnosed with DM and 3 IFG. DM patients and the control group had similar clinical characteristics, other than statins and anti-diabetic drugs, which were more common among DM patients. Patients with DM/IFG had decreased TCRT values computed from a random beat (0.06 ± 0.10 vs. 0.43 ± 0.07, p < 0.01) and an average beat (0.08 ± 0.09 vs. 0.44 ± 0.06, p < 0.01), when compared with the control group. TMD parameters did not differ. In conclusion, TCRT is reduced in patients with DM and no known cardiac diseases. Further research is required to investigate whether repolarization-associated changes in DM are the consequence of subclinical atherosclerosis, diabetic cardiomyopathy, or a combination of the two.

Personalized-Inherent Variability in a Time-Dependent Immune Response: A Look into the Fifth Dimension in Biology

Introduction

Individualized response to the immune triggers influences the course of immune-mediated diseases and the response to immunotherapies. Both inter- and intra-subject variations occur in time-dependent dynamics of biological systems. The present study aimed to establish a model for inherent personalized-time-dependent variability in response to immune triggers.

Methods

Male C57BL/6 mice were administered concanavalin A (ConA) and followed every 2 h for 10 h and at 24 h for serum alanine aminotransferase (ALT) levels.

Results

A marked intragroup variability was noted for both the timing of the effect of ConA, the magnitude of the increase in ALT levels, and the time to peak. While in some mice, a peak level was achieved, whereas a continuous increase in liver damage was noted in others. Four mice died at different time points during the study irrespective of their liver damage, further supporting the individualized-based response to the trigger.

Conclusions

This feasibility study established a model for determining the personalized-inherent variability in a time-dependent response to the immune triggers. These results highlight the importance of considering both the time and the wide range of individualized variability in immune responses while designing personalized-based immunotherapies.

ECG Ventricular Repolarization Dynamics during Exercise: Temporal Profile, Relation to Heart Rate Variability and Effects of Age and Physical Health

Periodic repolarization dynamics (PRD) is a novel electrocardiographic marker of cardiac repolarization instability with powerful risk stratification capacity for total mortality and sudden cardiac death. Here, we use a time-frequency analysis approach to continuously quantify PRD at rest and during exercise, assess its dependence on heart rate variability (HRV) and characterize the effects of age (young adults/middle-aged adults/older adults), body mass index (non-overweight/overweight) and cardiorespiratory fitness level (fit/unfit). Sixty-six male volunteers performed an exercise test. RR and dT variabilities (RRV, dTV), as well as the fraction of dT variability unrelated to RR variability, were computed based on time-frequency representations. The instantaneous LF power of dT (PdTV), representing the same concept as PRD, and of its RRV-unrelated component (PdTVuRRV) were quantified. dT angle was found to mostly oscillate in the LF band. Overall, 50-70% of PdTV was linearly unrelated to RRV. The onset of exercise caused a sudden increase in PdTV and PdTVuRRV, which returned to pre-exercise levels during recovery. Clustering analysis identified a group of overweight and unfit individuals with significantly higher PdTV and PdTVuRRV values at rest than the rest of the population. Our findings shed new light on the temporal profile of PRD during exercise, its relationship to HRV and the differences in PRD between subjects according to phenotypic characteristics.

Improving Diuretic Response in Heart Failure by Implementing a Patient-Tailored Variability and Chronotherapy-Guided Algorithm

Heart failure is a major public health problem, which is associated with significant mortality, morbidity, and healthcare expenditures. A substantial amount of the morbidity is attributed to volume overload, for which loop diuretics are a mandatory treatment. However, the variability in response to diuretics and development of diuretic resistance adversely affect the clinical outcomes. Morevoer, there exists a marked intra- and inter-patient variability in response to diuretics that affects the clinical course and related adverse outcomes. In the present article, we review the mechanisms underlying the development of diuretic resistance. The role of the autonomic nervous system and chronobiology in the pathogenesis of congestive heart failure and response to therapy are also discussed. Establishing a novel model for overcoming diuretic resistance is presented based on a patient-tailored variability and chronotherapy-guided machine learning algorithm that comprises clinical, laboratory, and sensor-derived inputs, including inputs from pulmonary artery measurements. Inter- and intra-patient signatures of variabilities, alterations of biological clock, and autonomic nervous system responses are embedded into the algorithm; thus, it may enable a tailored dose regimen in a continuous manner that accommodates the highly dynamic complex system.

T-wave morphology descriptors in patients with bulimia nervosa

PURPOSE

Bulimia nervosa (BN) is associated with increased risk of cardiovascular disease and arrhythmias. Some reports found abnormal electrocardiographic markers of arrhythmias in BN, while others did not. This study investigated novel parameters of T-wave morphology that were reported to be associated with adverse cardiovascular outcomes in other patient groups, among patients with BN under medical care.

METHOD

Thirty-five BN patients and 76 healthy controls were included. Total cosine R to T (TCRT) and T-wave Morphology Dispersion (TMD) parameters were computed according to accepted standards for an average beat and a random beat. Patients were followed for 11.1 ± 0.1 years for the emergence of arrhythmias or events of sudden death.

RESULTS

Twenty-five (71.4%) BN patients were hospitalized when enrolled, for a mean duration of 1.1 ± 0.2 months. The rest were ambulatory patients. The BN group had lower blood pressure, more smokers, and used antidepressants, neuroleptic drugs and benzodiazepines more than controls did. Other demographic parameters were comparable between groups. TCRT and TMD parameters were statistically similar and within the normal ranges reported by other research groups. None of the BN patients had prolonged QTc interval or electrolyte abnormalities on inclusion. During the follow-up period, no clinical symptoms suggestive of arrhythmias were reported, and no cardiovascular-related hospitalizations or deaths occurred in either group.

CONCLUSION

Medically treated BN patients have normal T-wave morphology parameters and hence, low risk for repolarization-associated malignant ventricular arrhythmias. The prognostic importance of these novel repolarization parameters remains to be explored among untreated patients, those who ingest emetic substances and patients with electrolyte imbalance.

LEVEL OF EVIDENCE

Level III.

Sudden cardiac death in HIV-infected patients: A contemporary review

HIV‐infected individuals have an increased risk of sudden cardiac death compared to the general population; yet the mechanisms underlying this increased risk remain unclear. The mechanisms underlying the heightened sudden cardiac death risk in HIV‐infected individuals is likely multifactorial. We reviewed the literature to elucidate and summarize the potential mechanisms contributing to sudden cardiac death in the HIV patient population. There is biologic plausibility that the following mechanisms may be contributing to the significantly heightened risk of sudden cardiac death in HIV to varying degrees: ventricular arrhythmias, myocardial fibrosis and scar, prolonged QTc interval (both as a direct effect of HIV on repolarization as well as a result of concurrent medications/antiretroviral therapies), substance abuse, structural heart disease, and premature atherosclerosis. Further understanding of the mechanisms underlying the increased sudden cardiac death risk in HIV can lead to identification of modifiable risk factors, implementation of public health programs, and potential revision of ICD implantation guidelines to ultimately reduce the incidence of sudden cardiac death in HIV‐infected patients. Further studies are needed to assess the relative contribution of each of these mechanisms and risk factors.

T-wave morphology among medically treated patients with Anorexia Nervosa

Anorexia nervosa (AN) has the highest rate of mortality of any psychiatric disorder, and cardiovascular complications occur in up to 80% of patients with AN and account for up to 30% of mortality. A controversy exists as to whether patients with AN are prone to develop electrocardiographic abnormalities related to repolarization. We aim to study previously unexplored T wave morphology markers in medically-treated patients with AN. Fifty-eight patients with AN (32 with restricting type and 26 with binge-eating/purging type) and 82 healthy controls were included in the study. ECGs were conducted under strict conditions and total cosine R-to-T (TCRT) and T-wave morphology dispersion (TMD) were computed according to accepted standards for a random beat and for an averaged beat. Forty-six AN patients were hospitalized (79.3%) during the study for a mean duration of 1.5 ± 1.1 months. AN patients had comparable QTc, TCRT, mean TMD, TMDpre, TMDpost and TCRTc values to those of healthy adults. Flattened T wave occurred slightly more often among AN patients than in controls (1.57 ± 1.23 leads affected compared with 1.11 ± 0.80 leads, respectively, p = 0.017). QTc, TCRT and TMD parameters' values were unaffected by the clinical type of AN. In conclusion, weight-restored AN patients are characterized by T wave flattening, but normal other T wave morphology parameters, which seemingly reflects an overall low risk of repolarization-associated ventricular arrhythmias. Long-term follow-up studies should be conducted to evaluate the prognostic significance of these novel repolarization markers in untreated patients or early in the refeeding phase.

Dual regulation by subcellular calcium heterogeneity and heart rate variability on cardiac electromechanical dynamics

Heart rate constantly varies under physiological conditions, termed heart rate variability (HRV), and in clinical studies, low HRV is associated with a greater risk of cardiac arrhythmias. Prior work has shown that HRV influences the temporal patterns of electrical activity, specifically the formation of pro-arrhythmic alternans, a beat-to-beat alternation in the action potential duration (APD), or intracellular calcium (Ca) levels. We previously showed that HRV may be anti-arrhythmic by disrupting APD and Ca alternations in a homogeneous cardiac myocyte. Here, we expand on our previous work, incorporating variation in subcellular Ca handling (also known to influence alternans) into a nonlinear map model of a cardiac myocyte composed of diffusively coupled Ca release units (CRUs). Ca-related parameters and initial conditions of each CRU are varied to mimic subcellular Ca heterogeneity, and a stochastic pacing sequence reproduces HRV. We find that subcellular Ca heterogeneity promotes the formation of spatially discordant subcellular alternans patterns, which decreases whole cell Ca and APD alternation for low and moderate HRV, while high subcellular Ca heterogeneity and HRV both promote electromechanical desynchronization. Finally, we find that for low and moderate HRV, both the specific subcellular Ca-related parameters and the pacing sequences influence measures of electromechanical dynamics, while for high HRV, these measures depend predominantly on the pacing sequence. Our results suggest that pro-arrhythmic subcellular discordant alternans tend to form for low levels of HRV, while high HRV may be anti-arrhythmic due to mitigated influence from subcellular Ca heterogeneity and desynchronization of APD from Ca instabilities.

HIV Infection Is Associated With Variability in Ventricular Repolarization: The Multicenter AIDS Cohort Study (MACS)

BACKGROUND

People living with human immunodeficiency virus (HIV+) have greater risk for sudden arrhythmic death than HIV-uninfected (HIV-) individuals. HIV-associated abnormal cardiac repolarization may contribute to this risk. We investigated whether HIV serostatus is associated with ventricular repolarization lability by using the QT variability index (QTVI), defined as a log measure of QT-interval variance indexed to heart rate variance.

METHODS

We studied 1123 men (589 HIV+ and 534 HIV-) from MACS (Multicenter AIDS Cohort Study), using the ZioXT ambulatory electrocardiography patch. Beat-to-beat analysis of up to 4 full days of electrocardiographic data per participant was performed using an automated algorithm (median analyzed duration [quartile 1-quartile 3]: 78.3 [66.3-83.0] hours/person). QTVI was modeled using linear mixed-effects models adjusted for demographics, cardiac risk factors, and HIV-related and inflammatory biomarkers.

RESULTS

Mean (SD) age was 60.1 (11.9) years among HIV- and 54.2 (11.2) years among HIV+ participants (P<0.001), 83% of whom had undetectable (<20 copies/mL) HIV-1 viral load (VL). In comparison with HIV- men, HIV+ men had higher QTVI (adjusted difference of +0.077 [95% CI, +0.032 to +0.123]). The magnitude of this association depended on the degree of viremia, such that in HIV+ men with undetectable VL, adjusted QTVI was +0.064 (95% CI, +0.017 to +0.111) higher than in HIV- men, whereas, in HIV+ men with detectable VL, adjusted QTVI was higher by +0.150 (95% CI, 0.072-0.228) than in HIV- referents. Analysis of QTVI subcomponents showed that HIV+ men had: (1) lower heart rate variability irrespective of VL status, and (2) higher QT variability if they had detectable, but not with undetectable, VL, in comparison with HIV- men. Higher levels of C-reactive protein, interleukin-6, intercellular adhesion molecule-1, soluble tumor necrosis factor receptor 2, and soluble cluster of differentiation-163 (borderline), were associated with higher QTVI and partially attenuated the association with HIV serostatus.

CONCLUSIONS

HIV+ men have greater beat-to-beat variability in QT interval (QTVI) than HIV- men, especially in the setting of HIV viremia and heightened inflammation. Among HIV+ men, higher QTVI suggests ventricular repolarization lability, which can increase susceptibility to arrhythmias, whereas lower heart rate variability signals a component of autonomic dysfunction.

Clinical and Echocardiographic Predictors of Arrhythmias Detected With 24-Hour Holter Electrocardiography Among Hypertensive Heart Failure Patients in Nigeria

Background

Hypertensive heart failure (HHF) is the commonest form of heart failure in Nigeria. There is paucity of data in Nigeria on 24-hour Holter electrocardiography (24-HHECG) and important predictors of arrhythmias among HHF patients.

Objectives

To determine the 24-HHECG characteristics among HHF patients. To determine the clinical and echocardiographic predictors of arrhythmias detected using 24-HHECG among HHF patients.

Methods

A total of 100 HHF patients as well as 50 age-matched and sex-matched apparently healthy controls were prospectively recruited over a period of 1 year. They all had baseline laboratory tests, echocardiography, and 24-HHECG.

Results

Hypertensive heart failure patients had significantly higher counts of premature ventricular contractions (PVCs) than the controls (P ≤ .001). Ventricular tachycardia (VT) was recorded in 29% of HHF patients as compared with controls who had no VT on 24-HHECG. The standard deviation of all normal to normal sinus RR intervals over 24 hours (SDNN) was abnormally reduced among HHF patients when compared with controls (P = .046). There was positive correlation between atrial fibrillation (AF) and the following parameters: PVCs (r = .229, P = .015), New York Heart Association (NYHA) (r = .196, P = .033), and VT (r = .223, P = .018). Following multiple linear regression, left ventricular ejection fraction (LVEF) (P ≤ .001) and serum urea (P = .037) were predictors of PVCs among HHF patients. Serum creatinine (P ≤ .001), elevated systolic blood pressure (SBP) (P = .005), and PVCs (P ≤ .001) were important predictors of VT among HHF patients.

Conclusions

Renal dysfunction and reduced LVEF were important predictors of ventricular arrhythmias. High counts of PVCs and elevated SBP were predictive of the occurrence of VT among HHF patients. The NYHA class and ventricular arrhythmias have a significant positive correlation with AF. The SDNN is reduced in HHF patients.