The electric signals detected by intracardiac electrodes provide information on the occurrence and timing of myocardial depolarization, but are not generally helpful to characterize the nature and ...origin of the sensed event. A novel recording technique referred to as intracardiac ECG (iECG) has overcome this limitation. The iECG is a multipolar signal, which combines the input from both atrial and ventricular electrodes of a dual-chamber pacing system in order to assess the global electric activity of the heart. The tracing resembles a surface ECG lead, featuring P, QRS and T waves. The time-course of the waveform representing ventricular depolarization (iQRS) does correspond to the time-course of the surface QRS with any ventricular activation modality. Morphological variants of the iQRS waveform are specifically associated with each activity pattern, which can therefore be diagnosed by evaluation of the iECG tracing. In the event of tachycardia, SVTs with narrow QRS can be distinguished from other arrhythmia forms based upon the preservation of the same iQRS waveform recorded in sinus rhythm. In ventricular capture surveillance, real pacing failure can be reliably discriminated from fusion beats by the analysis of the area delimited by the iQRS signal. Assessing the iQRS waveform correspondence with a reference template could be a way to check the effectiveness of biventricular pacing, and to discriminate myocardial capture alone from additional His bundle recruitment in para-Hisian stimulation. The iECG is not intended as an alternative to conventional intracavitary sensing, which remains the only tool suitable to drive the sensing function of a pacing device. Nevertheless, this new electric signal can add the benefits of morphological data processing, which might have important implications on the quality of the pacing therapy.
Cardiac β-adrenergic and the muscarinic receptors control contractility and heart rate by triggering multiple signaling events involving downstream targets like the phosphoinositide 3-kinase γ ...(PI3Kγ). We thus investigated whether the lack of PI3Kγ could play a role in the autonomic regulation of the mouse heart. Contractility and
I
CaL of mutant cardiac preparations appeared increased in basal conditions and after β-adrenergic stimulation. However, basal and β-adrenergic stimulated heart rate were normal. Conversely, muscarinic inhibition of heart rate was reduced without alteration of the G
βγ-dependent stimulation of
I
K,ACh current. In addition, muscarinic-mediated anti-adrenergic effect on papillary muscle contractility and
I
CaL was significantly depressed. Consistently, cAMP level of PI3Kγ-null ventricles was always higher than wild-type controls. Thus, PI3Kγ controls the cardiac function by reducing cAMP concentration independently of G
i-mediated signaling.
Multiclass Convolutional Neural Networks for Atrial Fibrillation Classification Sbrollini, Agnese; Tomassini, Selene; Emaldi, Enrico ...
Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference,
07/2022, Letnik:
2022
Journal Article
Atrial fibrillation (AF) is a common supraventricular arrhythmia. Its automatic identification by standard 12-lead electrocardiography (ECG) is still challenging. Recently, deep learning provided new ...instruments able to mimic the diagnostic ability of clinicians but only in case of binary classification (AF vs. normal sinus rhythm-NSR). However, binary classification is far from the real scenarios, where AF has to be discriminated also from several other physiological and pathological conditions. The aim of this work is to present a new AF multiclass classifier based on a convolutional neural network (CNN), able to discriminate AF from NSR, premature atrial contraction (PAC) and premature ventricular contraction (PVC). Overall, 2796 12-lead ECG recordings were selected from the open-source "PhysioNet/Computing in Cardiology Challenge 2021" database, to construct a dataset constituted by four balanced classes, namely AF class, PAC class, PVC class, and NSR class. Each lead of each ECG recording was decomposed into spectrogram by continuous wavelet transform and saved as 2D grayscale images, used to feed a 6-layers CNN. Considering the same CNN architecture, a multiclass classifiers (all classes) and three binary classifiers (AF class, PAC class, and PVC class vs. NSR class) were created and validated by a stratified shuffle split cross-validation of 10 splits. Performance was quantified in terms of area under the curve (AUC) of the receiver operating characteristic. Multiclass classifier performance was high (AF class: 96.6%; PAC class: 95.3%; PVC class: 92.8%; NSR class: 97.4%) and preferable to binary classifiers. Thus, our CNN AF multiclass classifier proved to be an efficient tool for AF discrimination from physiological and pathological confounders. Clinical Relevance-Our CNN AF multiclass classifier proved to be suitable for AF discrimination in real scenarios.
Cardiac β‐adrenergic and the muscarinic receptors control contractility and heart rate by triggering multiple signaling events involving downstream targets like the phosphoinositide 3‐kinase γ ...(PI3Kγ). We thus investigated whether the lack of PI3Kγ could play a role in the autonomic regulation of the mouse heart. Contractility and I
CaL of mutant cardiac preparations appeared increased in basal conditions and after β‐adrenergic stimulation. However, basal and β‐adrenergic stimulated heart rate were normal. Conversely, muscarinic inhibition of heart rate was reduced without alteration of the Gβγ‐dependent stimulation of I
K,ACh current. In addition, muscarinic‐mediated anti‐adrenergic effect on papillary muscle contractility and I
CaL was significantly depressed. Consistently, cAMP level of PI3Kγ‐null ventricles was always higher than wild‐type controls. Thus, PI3Kγ controls the cardiac function by reducing cAMP concentration independently of Gi‐mediated signaling.
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