Browsing by Subject "Ventricular fibrillation"

Now showing 1 - 4 of 4
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    Role of Apamin-Sensitive Calcium-Activated Small-Conductance Potassium Currents on the Mechanisms of Ventricular Fibrillation in Pacing-Induced Failing Rabbit Hearts
    (American Heart Association, 2017-02) Yin, Dechun; Hsieh, Yu-Cheng; Tsai, Wei-Chung; Wu, Adonis Zhi-Yang; Jiang, Zhaolei; Chan, Yi-Hsin; Xu, Dongzhu; Yang, Na; Shen, Changyu; Chen, Zhenhui; Lin, Shien-Fong; Chen, Peng-Sheng; Everett, Thomas H., IV; Medicine, School of Medicine
    BACKGROUND: Ventricular fibrillation (VF) during heart failure is characterized by stable reentrant spiral waves (rotors). Apamin-sensitive small-conductance calcium-activated potassium currents (IKAS) are heterogeneously upregulated in failing hearts. We hypothesized that IKAS influences the location and stability of rotors during VF. METHODS AND RESULTS: Optical mapping was performed on 9 rabbit hearts with pacing-induced heart failure. The epicardial right ventricular and left ventricular surfaces were simultaneously mapped in a Langendorff preparation. At baseline and after apamin (100 nmol/L) infusion, the action potential duration (APD80) was determined, and VF was induced. Areas with a >50% increase in the maximum action potential duration (ΔAPD) after apamin infusion were considered to have a high IKAS distribution. At baseline, the distribution density of phase singularities during VF in high IKAS distribution areas was higher than in other areas (0.0035±0.0011 versus 0.0014±0.0010 phase singularities/pixel; P=0.004). In addition, high dominant frequencies also colocalized to high IKAS distribution areas (26.0 versus 17.9 Hz; P=0.003). These correlations were eliminated during VF after apamin infusion, as the number of phase singularities (17.2 versus 11.0; P=0.009) and dominant frequencies (22.1 versus 16.2 Hz; P=0.022) were all significantly decreased. In addition, reentrant spiral waves became unstable after apamin infusion, and the duration of VF decreased. CONCLUSIONS: The IKAS current influences the mechanism of VF in failing hearts as phase singularities, high dominant frequencies, and reentrant spiral waves all correlated to areas of high IKAS. Apamin eliminated this relationship and reduced VF vulnerability.
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    Ventricular divergence correlates with epicardial wavebreaks and predicts ventricular arrhythmia in isolated rabbit hearts during therapeutic hypothermia
    (Public Library of Science, 2020-02-21) Hsieh, Yu-Cheng; Hsieh, Wan-Hsin; Li, Cheng-Hung; Liao, Ying-Chieh; Lin, Jiunn-Cherng; Weng, Chi-Jen; Lo, Men-Tzung; Tuan, Ta-Chuan; Lin, Shien-Fong; Yeh, Hung-I; Huang, Jin-Long; Haugan, Ketil; Larsen, Bjarne D.; Lin, Yenn-Jiang; Lin, Wei-Wen; Wu, Tsu-Juey; Chen, Shih-Ann; Medicine, School of Medicine
    INTRODUCTION: High beat-to-beat morphological variation (divergence) on the ventricular electrogram during programmed ventricular stimulation (PVS) is associated with increased risk of ventricular fibrillation (VF), with unclear mechanisms. We hypothesized that ventricular divergence is associated with epicardial wavebreaks during PVS, and that it predicts VF occurrence. METHOD AND RESULTS: Langendorff-perfused rabbit hearts (n = 10) underwent 30-min therapeutic hypothermia (TH, 30°C), followed by a 20-min treatment with rotigaptide (300 nM), a gap junction modifier. VF inducibility was tested using burst ventricular pacing at the shortest pacing cycle length achieving 1:1 ventricular capture. Pseudo-ECG (p-ECG) and epicardial activation maps were simultaneously recorded for divergence and wavebreaks analysis, respectively. A total of 112 optical and p-ECG recordings (62 at TH, 50 at TH treated with rotigaptide) were analyzed. Adding rotigaptide reduced ventricular divergence, from 0.13±0.10 at TH to 0.09±0.07 (p = 0.018). Similarly, rotigaptide reduced the number of epicardial wavebreaks, from 0.59±0.73 at TH to 0.30±0.49 (p = 0.036). VF inducibility decreased, from 48±31% at TH to 22±32% after rotigaptide infusion (p = 0.032). Linear regression models showed that ventricular divergence correlated with epicardial wavebreaks during TH (p<0.001). CONCLUSION: Ventricular divergence correlated with, and might be predictive of epicardial wavebreaks during PVS at TH. Rotigaptide decreased both the ventricular divergence and epicardial wavebreaks, and reduced the probability of pacing-induced VF during TH.
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    Ventricular fibrillation in congenitally corrected transposition of great arteries treated with pacing: a case report
    (Oxford, 2019-12) Zhang, Lei; Liu, Hongyang; Wan, Qilin; Han, Xinqiang; Medicine, School of Medicine
    Background Congenitally corrected transposition of the great arteries (CCTGA) is a rare form of congenital heart disease which may present with sudden death from malignant arrhythmias including complete heart block and ventricular tachyarrhythmias as late complications. Only few cases about ventricular tachyarrhythmias, usually in those with markedly depressed systemic ventricular function, have been reported. Case summary A 26-year-old woman with a known history of CCTGA presented to the emergency department with palpitations and breathlessness for 3–4 weeks and worsening symptoms for 8 h. She had a history of ventricular septal defect repair 14 years ago. Her initial presentation electrocardiogram demonstrated high degree atrioventricular block with a ventricular rate of 44 b.p.m. She had two episodes of complete syncope during this hospitalization, both required external defibrillation due to documented bradycardia-dependent ventricular fibrillations. Her two-dimensional echocardiography study confirmed the diagnosis of CCTGA with preserved systolic ventricular function. She underwent urgent temporal pacing wire placement with a paced ventricular rate at 90 b.p.m. Having thoroughly reviewed the arrhythmia events and discussed with the patient about the option of defibrillator vs. pacemaker therapy a decision was made upon her request for dual-chamber pacemaker implantation. She was discharged home uneventfully 3 days after hospital presentation and has been physically active at 3-, 6-, and 9-month follow-ups. Discussion Our case illustrates the individualized clinical decision making in choosing device therapy for a rare congenital heart disease presented with malignant arrhythmia. Careful history taking, open communication, and closely planned long-term follow-up will be essential in caring for such patients.