Activity

Clinical Relevance- This indicates that pulse rate variability is affected differently to heart rate variability when autonomic activity is modified and suggests that pulse rate variability is not always a valid surrogate of heart rate variability.The main goal of this research is to evaluate the defibrillation efficacy with the high-frequency waveform on ventricular fibrillation in small animals. A biphasic defibrillator with adjustable frequency was designed for this study. This custom-designed defibrillator can be adjusted to generate four different frequencies of 125, 250, 500, and 1000 Hz. Six rat hearts were induced VT/VF by electrical induction using the waveform of these four frequencies. Success VT/VF-induction by applying those four frequencies were recorded and observed by optical mapping. The results showed that the VT/VF-induction success rate is increasing along with higher frequencies. The VT/VF-induction success rate is 16% in 125Hz and 250 Hz, 33% in 500 Hz, and 100% in 1000 Hz with S1-S2 protocol at 100 ms coupling interval. Also, using optical mapping technique, shock-induced optical potential showed that only high-frequency waveform exhibited the largest tissue responses in the middle position of the heart. In conclusion, high-frequency (1000Hz) defibrillation waveform has the highest defibrillation efficacy comparing to other lower frequencies used in this study.The zebrafish model has been demonstrated as an ideal vertebrate model system for a diverse range of biological studies. Along with conventional approaches, monitoring and analysis of zebrafish electrocardiogram (ECG) have been utilized for cardio-physiological screening and elucidation. ECG monitoring has been carried out with fish treated with anesthetic drugs, rendering the short period of time in recording the signals ( less then 5 min). In this work, a prolonged sedation system for continuous ECG monitoring of multiple zebrafish was proposed and developed. We built a circulation system to provide prolonged mild anesthesia which allows more consistent and intrinsic ECG measurement. The use of prolonged anesthesia helped reduce the concentration of the anesthetic drug (MS222 or Tricaine) from 200 mg/L to 100 mg/L and even lower; thus, maintaining the integrity of intrinsic ECG. compound library chemical Moreover, heartrate variation during recording was investigated, showing minute changes (±3.2 beats per minute – BPM). The development of this prolonged ECG monitoring system would open the possibility of long-term monitoring for studies such as drug screening and forward genetic screening.Over the last few years, the use of cardiac mapping for effective diagnosis and treatment of arrhythmias has increased significantly. In the clinical environment, electroanatomical mapping (EAM) is performed during the electrophysiological procedures using proprietary systems such as CARTO, EnSite Precision, RHYTHMIA, etc. These systems generate the 3D model of patient-specific atria with the electrical activity (i.e., intracardiac electrograms (iEGMs)) displayed on it, for further identification of the sources of arrhythmia and for guiding cardiac ablation therapy. Recently, several novel techniques were developed to perform iEGMs analysis to more accurately identify the arrhythmogenic sites. However, there is a difficulty in incorporating the results of iEGMs analysis back to EAM systems due to their proprietary constraints. This created a hurdle in the further development of novel techniques to help navigate patient-specific clinical ablation therapy. Thus, we developed an open source software, VIEgram1, that allows researchers to visualize the results of the various iEGMs analysis on a patient-specific 3D atria model. It eliminates the dependency of the academic environment on the proprietary EAM systems, thereby making the process of retrospective mapping extremely convenient and time efficient. Here, we demonstrate the features of VIEgram such as visual inspection of iEGMs, flexibility in implementing custom iEGMs analysis techniques and interpolation schemes, and spatial analysis.Rhythm regularity of the heart depends on how electrical impulses spread through the cardiac conduction system. Any abnormal activities in the electrical impulses can lead to serious cardiac disorders or sudden death. It is important to understand the electrical activities of the human heart in both healthy and diseased conditions to determine the cause of cardiac disorders and explore the best therapeutic designs. Mathematical models calibrated with clinical and/or in-vitro data are popularly used to study cardiac function and investigate treatment effects. Most of the current human heart models are highly integrated and couple over a hundred equations across different organizational scales of ion channel, cell, and muscle. The model complex poses a significant computational challenge on cardiac simulation. This study developed a metamodel to replace the time-consuming simulation model. Specifically, Gaussian Process (GP) is used to reconstruct the spatiotemporal variations of the cell membrane potential in left atrium. Four different covariance functions were used to infer the potential distributions. The GP model provides an accurate estimation of the spatiotemporal propagation of electrical waves with a small set of data and shows great advantage in computations as compared to traditional models.

Arterial-ventricular coupling (AVC) has been recognized as a key determinant of global cardiovascular performance. Diastolic dysfunction (DD) occurs when inadequate filling of the ventricles is related to an abnormal elevation of intracardiac filling pressures. In some cases, DD is evidenced during cardiac stress, provoked by exercise.

To evaluate AVC in individuals with stress evidenced DD, in relation to controls.

Stress echocardiography was applied to assess cardiac function during exercise. Arterial-ventricular coupling was evaluated, based on the assessment of left ventricular and arterial elastances.

AVC showed a significant difference at peak exercise compared to controls, basically due to a loss of cardiac contractility.

The manifestation of AVC coupling imbalance could act as a complementary parameter to support the diagnosis of DD.

The manifestation of AVC coupling imbalance could act as a complementary parameter to support the diagnosis of DD.