Non-invasive continuous blood pressure measurement is an emerging issue that potentially can be applied to cardiovascular disease monitoring and prediction. Recently, many groups have proposed the ...pulse transition time (PTT) method to estimate blood pressure for long-term monitoring. However, the PTT-based methods for blood pressure estimation are limited by non-specific estimation models and require multiple calibrations. This study aims to develop a low-cost wearable piezoelectric-based system for continuous beat-to-beat blood pressure measurement. The pressure change in the radial artery was extracted by systolic and diastolic feature points in pressure pulse wave (PPW) and the pressure sensitivity of the sensor. The proposed system showed a reliable accuracy of systolic blood pressure (SBP) (mean absolute error (MAE) ± standard deviation (SD) 1.52 ± 0.30 mmHg) and diastolic blood pressure (DBP, MAE ± SD 1.83 ± 0.50), and its performance agreed with standard criteria of MAE within 5 mmHg and SD within ±8 mmHg. In conclusion, this study successfully developed a low-cost, high-accuracy piezoelectric-based system for continuous beat-to-beat SBP and DBP measurement without multiple calibrations and complex regression analysis. The system is potentially suitable for continuous, long-term blood pressure-monitoring applications.
Autonomic nervous system activation can induce significant and heterogeneous changes of atrial electrophysiology and induce atrial tachyarrhythmias, including atrial tachycardia and atrial ...fibrillation (AF). The importance of the autonomic nervous system in atrial arrhythmogenesis is also supported by circadian variation in the incidence of symptomatic AF in humans. Methods that reduce autonomic innervation or outflow have been shown to reduce the incidence of spontaneous or induced atrial arrhythmias, suggesting that neuromodulation may be helpful in controlling AF. In this review, we focus on the relationship between the autonomic nervous system and the pathophysiology of AF and the potential benefit and limitations of neuromodulation in the management of this arrhythmia. We conclude that autonomic nerve activity plays an important role in the initiation and maintenance of AF, and modulating autonomic nerve function may contribute to AF control. Potential therapeutic applications include ganglionated plexus ablation, renal sympathetic denervation, cervical vagal nerve stimulation, baroreflex stimulation, cutaneous stimulation, novel drug approaches, and biological therapies. Although the role of the autonomic nervous system has long been recognized, new science and new technologies promise exciting prospects for the future.
Electrocardiogram (ECG)-based intelligent screening for systolic heart failure (HF) is an emerging method that could become a low-cost and rapid screening tool for early diagnosis of the disease ...before the comprehensive echocardiographic procedure. We collected 12-lead ECG signals from 900 systolic HF patients (ejection fraction, EF < 50%) and 900 individuals with normal EF in the absence of HF symptoms. The 12-lead ECG signals were converted by continuous wavelet transform (CWT) to 2D spectra and classified using a 2D convolutional neural network (CNN). The 2D CWT spectra of 12-lead ECG signals were trained separately in 12 identical 2D-CNN models. The 12-lead classification results of the 2D-CNN model revealed that Lead V6 had the highest accuracy (0.93), sensitivity (0.97), specificity (0.89), and f1 scores (0.94) in the testing dataset. We designed four comprehensive scoring methods to integrate the 12-lead classification results into a key diagnostic index. The highest quality result among these four methods was obtained when Leads V5 and V6 of the 12-lead ECG signals were combined. Our new 12-lead ECG signal-based intelligent screening method using straightforward combination of ECG leads provides a fast and accurate approach for pre-screening for systolic HF.
Non-contact electrocardiogram (ECG) measurement is an advanced sensing technique that uses capacitive electrodes to detect cardiac signals through non-conductive fabrics. However, the capacitive ...coupling is a significant factor that affects signal-to-noise ratio (SNR) of non-contact ECG, including skin-electrode active area, material, and thickness of the non-conductive fabric. This study aims to develop a high-fidelity non-contact ECG system to evaluate the influence of capacitive coupling on ECG measurement. In this study, a polymer foam with low surface resistance (<inline-formula> <tex-math notation="LaTeX">0.05\Omega </tex-math></inline-formula>/inch 2 ) was designed for improving the capacitive-coupling interface between the curved body and electrode sensing surface. The system recorded excellent non-contact ECG of 29.8dB, and the accuracy of heart rate was 99.5% compared to wet-contact ECG measurement. The SNR exponentially attenuated with decreasing skin-electrode capacitance by the combined evidence of theoretical calculation and experimental results. The proposed system generates distinguishable ECG signals (SNR>0dB) at the skin-electrode capacitance above 85pF and maximum through-thickness of cotton-based cloth of 1.2mm. In conclusion, this study evaluated the influence of capacitive coupling on non-contact ECG measurements and established a lower bound of the coupling capacitance for satisfactory signal quality. Future studies may investigate whether the coupling capacitance can be further reduced.
neuECG, the simultaneous noninvasive recording of ECG and skin sympathetic nerve activity (SKNA), directly records sympathetic nerve activity over a long period of time. It can be used to measure ...sympathetic tone in healthy subjects and in subjects with non-cardiovascular diseases. The electrical activity that can be measured on the surface of the skin originates from the heart, the muscle or nerve structures. Because the frequency content of nerve activity falls in a higher frequency range than that of the ECG and myopotential, it is possible to use high-pass or band-pass filtering to specifically isolate the SKNA. neuECG is voltage calibrated and does not require invasive procedures to impale electrodes in nerves and thus has advantages over microneurography. Here, we present a protocol that takes <10 min to set up. The neuECG can be continuously recorded over a 24-h period or longer. We also describe methods to efficiently analyze neuECG from humans using commercially available hardware and software to facilitate adoption of this technology in clinical research.
The aim of this study was to establish a rapid prescreening tool for heart failure with preserved ejection fraction (HFpEF) by using artificial intelligence (AI) techniques to detect abnormal ...echocardiographic patterns in structure and function on the basis of intrabeat dynamic changes in the left ventricle and the left atrium.
Although diagnostic criteria for HFpEF have been established, rapid and accurate assessment of HFpEF using echocardiography remains challenging and highly desirable.
In total, 1,041 patients with HFpEF and 1,263 asymptomatic individuals were included in the study. The participants’ 4-chamber view images were extracted from the echocardiographic files and randomly separated into training, validation, and internal testing data sets. An external testing data set comprising 150 patients with symptomatic chronic obstructive pulmonary disease and 315 patients with HFpEF from another hospital was used for further model validation. The intrabeat dynamics of the geometric measures were extracted frame by frame from the image sequence to train the AI models.
The accuracy, sensitivity, and specificity of the best AI model for detecting HFpEF were 0.91, 0.96, and 0.85, respectively. The model was further validated using an external testing data set, and the accuracy, sensitivity, and specificity became 0.85, 0.79, and 0.89, respectively. The area under the receiver-operating characteristic curve was used to evaluate model classification ability. The highest area under the curve in the internal testing data set and external testing data set was 0.95.
The AI system developed in this study, incorporating the novel concept of intrabeat dynamics, is a rapid, time-saving, and accurate prescreening method to facilitate HFpEF diagnosis. In addition to the classification of diagnostic outcomes, such an approach can automatically generate valuable quantitative metrics to assist clinicians in the diagnosis of HFpEF.
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Key Points
It is unknown if a sex difference exists in cardiac apamin‐sensitive small conductance Ca2+‐activated K+ (SK) current (IKAS).
There is no sex difference in IKAS in the basal condition. ...However, there is larger IKAS in female rabbit ventricles than in male during isoproterenol infusion.
IKAS activation by isoproterenol leads to action potential triangulation in females, indicating its abundant activation at early phases of repolarization.
IKAS activation in females induces negative Ca2+–voltage coupling and promotes electromechanically discordant phase 2 repolarization alternans.
IKAS is important in the mechanisms of ventricular fibrillation in females during sympathetic stimulation.
Sex has a large influence on cardiac electrophysiological properties. Whether sex differences exist in apamin‐sensitive small conductance Ca2+‐activated K+ (SK) current (IKAS) remains unknown. We performed optical mapping, transmembrane potential, patch clamp, western blot and immunostaining in 62 normal rabbit ventricles, including 32 females and 30 males. IKAS blockade by apamin only minimally prolonged action potential (AP) duration (APD) in the basal condition for both sexes, but significantly prolonged APD in the presence of isoproterenol in females. Apamin prolonged APD at the level of 25% repolarization (APD25) more prominently than APD at the level of 80% repolarization (APD80), consequently reversing isoproterenol‐induced AP triangulation in females. In comparison, apamin prolonged APD to a significantly lesser extent in males and failed to restore the AP plateau during isoproterenol infusion. IKAS in males did not respond to the L‐type calcium current agonist BayK8644, but was amplified by the casein kinase 2 (CK2) inhibitor 4,5,6,7‐tetrabromobenzotriazole. In addition, whole‐cell outward IKAS densities in ventricular cardiomyocytes were significantly larger in females than in males. SK channel subtype 2 (SK2) protein expression was higher and the CK2/SK2 ratio was lower in females than in males. IKAS activation in females induced negative intracellular Ca2+–voltage coupling, promoted electromechanically discordant phase 2 repolarization alternans and facilitated ventricular fibrillation (VF). Apamin eliminated the negative Ca2+–voltage coupling, attenuated alternans and reduced VF inducibility, phase singularities and dominant frequencies in females, but not in males. We conclude that β‐adrenergic stimulation activates ventricular IKAS in females to a much greater extent than in males. IKAS activation plays an important role in ventricular arrhythmogenesis in females during sympathetic stimulation.
Key Points
It is unknown if a sex difference exists in cardiac apamin‐sensitive small conductance Ca2+‐activated K+ (SK) current (IKAS).
There is no sex difference in IKAS in the basal condition. However, there is larger IKAS in female rabbit ventricles than in male during isoproterenol infusion.
IKAS activation by isoproterenol leads to action potential triangulation in females, indicating its abundant activation at early phases of repolarization.
IKAS activation in females induces negative Ca2+–voltage coupling and promotes electromechanically discordant phase 2 repolarization alternans.
IKAS is important in the mechanisms of ventricular fibrillation in females during sympathetic stimulation.
Objectives The purpose of this study was to evaluate the changes of left stellate ganglionic nerve activity (SGNA) and left thoracic vagal nerve activity (VNA) after acute myocardial infarction (MI). ...Background Whether MI results in remodeling of extracardiac nerve activity remains unclear. Methods We implanted radiotransmitters to record the SGNA, VNA, and electrocardiogram in 9 ambulatory dogs. After baseline monitoring, MI was created by 1-h balloon occlusion of the coronary arteries. The dogs were then continuously monitored for 2 months. Both stellate ganglia were stained for growth-associated protein 43 and synaptophysin. The stellate ganglia from 5 normal dogs were used as control. Results MI increased 24-h integrated SGNA from 7.44 ± 7.19 Ln(Vs)/day at baseline to 8.09 ± 7.75 Ln(Vs)/day after the MI (p < 0.05). The 24-h integrated VNA before and after the MI was 5.29 ± 5.04 Ln(Vs)/day and 5.58 ± 5.15 Ln(Vs)/day, respectively (p < 0.05). A significant 24-h circadian variation was noted for the SGNA (p < 0.05) but not the VNA. The SGNA/VNA ratio also showed significant circadian variation. The nerve densities from the left SG were 63,218 ± 34,719 μm2 /mm2 and 20,623 ± 4,926 μm2 /mm2 for growth-associated protein 43 (p < 0.05) and were 32,116 ± 8,190 μm2 /mm2 and 16,326 ± 4,679 μm2 /mm2 for synaptophysin (p < 0.05) in MI and control groups, respectively. The right SG also showed increased nerve density after MI (p < 0.05). Conclusions MI results in persistent increase in the synaptic density of bilateral stellate ganglia and is associated with increased SGNA and VNA. There is a circadian variation of the SGNA/VNA ratio. These data indicate significant remodeling of the extracardiac autonomic nerve activity and structures after MI.
Diabetes has become a chronic metabolic disorder, and the growing diabetes population makes medical care more important. We investigated using a portable and noninvasive contact lens as an ideal ...sensor for diabetes patients whose tear fluid contains glucose. The key feature is the reversible covalent interaction between boronic acid and glucose, which can provide a noninvasive glucose sensor for diabetes patients. We present a phenylboronic acid (PBA)-based HEMA contact lens that exhibits a reversible swelling/shrinking effect to change its thickness. The difference in thickness can be detected in a picture taken with a smartphone and analyzed using software. Our novel technique offers the following capabilities: (i) non-enzymatic and continuous glucose detection with the contact lens; (ii) no need for an embedded circuit and power source for the glucose sensor; and (iii) the use of a smartphone to detect the change in thickness of the contact lens with no need for additional photo-sensors. This technique is promising for a noninvasive measurement of the glucose level and simple implementation of glucose sensing with a smartphone.
The relationship between autonomic activation and the mechanisms of paroxysmal atrial fibrillation remains unclear.
We implanted a pacemaker and a radio transmitter in 7 dogs (group 1). After ...baseline recording, we paced the left atrium at 20 Hz for 1 week and then monitored left stellate ganglion nerve activity, left vagal nerve activity, and left atrial electrogram without pacing for 24 hours. This protocol repeated itself until sustained atrial fibrillation (>48 hours) was induced in 3+/-1 weeks. In another 6 dogs (group 2), we cryoablated left and right stellate ganglia and the cardiac branch of the left vagal nerve during the first surgery and then repeated the same pacing protocol until sustained atrial fibrillation was induced in 7+/-4 weeks (P=0.01). There were 4+/-2 episodes of paroxysmal atrial fibrillation per day and 10+/-3 episodes of paroxysmal atrial tachycardia per day in group 1. Simultaneous sympathovagal discharges were observed to immediately precede the onset of atrial arrhythmias in 73% of episodes. In comparison, group 2 dogs had no paroxysmal atrial fibrillation (P=0.046) or paroxysmal atrial tachycardia (P<0.001) episodes. Nerve sprouting, sympathetic hyperinnervation, and a massive elevation of transcardiac norepinephrine levels occurred in both groups.
Intermittent rapid left atrial pacing results in sympathetic hyperinnervation, paroxysmal atrial fibrillation, and paroxysmal atrial tachycardia. Simultaneous sympathovagal discharges are common triggers of these arrhythmias. Cryoablation of extrinsic sympathovagal nerves eliminated paroxysmal atrial fibrillation and paroxysmal atrial tachycardia, which suggests that simultaneous sympathovagal discharges and these arrhythmias are causally related. Because cryoablation only delayed but did not prevent sustained atrial fibrillation, autonomic nerve activity is not the only factor that determines atrial fibrillation maintenance.
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