Suwei Wang

Circadian Body Temperature Variability is an Indicator of Poor Prognosis in Cardiomyopathic Hamsters

BACKGROUND Low body temperature is an independent predictor of poor prognosis in patients with congestive heart failure. The cardiomyopathic hamster develops progressive biventricular dysfunction, resulting in heart failure death at 9 months to 1 year of life. Our goal was to use cardiomyopathic hamsters to examine the relationship between body temperature and heart failure decompensation and death. METHODS AND RESULTS To this end, we implanted temperature and activity transducers with telemetry into the peritoneal space of 46 male Bio-TO-2 Syrian cardiomyopathic hamsters. Multiple techniques, including computing mean temperature, frequency domain analysis, and nonlinear analysis, were used to determine the most useful method for predicting poor prognosis. Data from 44 hamsters were included in our final analysis. We detected a decline in core body temperature in 98% of the hamsters 8+/-4 days before death (P < .001). We examined the dominant frequency of temperature variation (ie, the circadian rhythm) by using cosinor analysis, which revealed a significant decrease in the amplitude of the body temperature circadian rhythm 8 weeks before death (0.28 degrees C; 95% CI, 0.26-0.31) compared to baseline (0.36 degrees C; 95% CI, 0.34-0.39; P=.005). The decline in the circadian temperature variation preceded all other evidence of decompensation. CONCLUSIONS We conclude that a decrease in the amplitude of the body temperature circadian rhythm precedes fatal decompensation in cardiomyopathic hamsters. Continuous temperature monitoring may be useful in predicting preclinical decompensation in patients with heart failure and in identifying opportunities for therapeutic intervention.

Ionic Mechanisms Underlying the Effects of Vasoactive Intestinal Polypeptide on Canine Atrial Myocardium

Background— Vasoactive intestinal polypeptide (VIP) is released from intracardiac neurons during vagal stimulation, ischemia, and heart failure, which are associated with increased vulnerability to atrial fibrillation. VIP shortens atrial effective refractory periods in dogs. Endogenous VIP contributes to vagally mediated acceleration of atrial electric remodeling. VIP is also shown to prolong the duration of acetylcholine-induced atrial fibrillation. However, the ionic mechanisms underlying VIP effects are largely unknown. Methods and Results— The effects of VIP on transmembrane ion channels were studied in canine atrial cardiomyocytes using patch-clamp techniques. VIP increased delayed rectifier K+ current and L-type calcium current but decreased the transient outward K+ current and sodium current. Optical mapping technique was used to assess effects of VIP on action potential durations (APDs) in isolated canine left atria. VIP shortened APD and slowed conduction velocity in a dose-dependent manner. Furthermore, VIP increased spatial heterogeneity of APD and conduction velocity, as assessed by the SDs of APD and conduction velocity, and atrial fibrillation inducibility. Conclusions— Through its diverse effects on ion channels, VIP shortens APD with increased APD spatial heterogeneity and decreases intra-atrial conduction velocity, which may play an important role in the pathogenesis of atrial arrhythmias in scenarios where VIP release is increased.

Esophageal Temperature Monitoring During Radiofrequency Ablation of Atrial Fibrillation: A Meta-Analysis

Objective: Atrio-esophageal fistula is an infrequent but devastating complication of catheter-based ablation of atrial fibrillation (AF). Thermal esophageal injury may be the precursor of atrio-esophageal fistula. Here, we evaluated the role of esophageal temperature monitoring in preventing thermal esophageal injury during pulmonary vein isolation for AF with radiofrequency energy. Methods: In this meta-analysis, we searched the PubMed, Cochrane, Scopus, Embase, and Refworks databases for all published studies from January 2004 to June 2016 to evaluate the role of esophageal temperature monitoring. We searched for terms esophageal temperature monitoring, AF, radiofrequency ablation, atrio-esophageal fistula, and thermal esophageal injury. We included studies comparing luminal esophageal temperature (LET) monitoring with no LET monitoring during radiofrequency ablation of AF. We excluded studies in which post-ablation esophagogastroduodenoscopy (EGD) was not performed to identify esophageal thermal injuries. To perform the meta-analysis, we used Review Manager statistical software and a fixed-effects modeling to derive the outcomes. Given significant heterogeneity between the studies, we used meta-regression analysis to adjust for age and sex. Results: We identified 4 non-randomized controlled trials that met our search criteria and included a total of 411 patients (n=235 in the LET monitoring group; n=176 in the no LET monitoring group) in the analysis. There were 21 (8.9%) patients with thermal esophageal injury in the LET monitoring group and 12 (6.8%) in the no LET monitoring group. The pooled odds ratio was 0.66 (0.23-1.89), indicating no statistically significant differences between the 2 groups with regard to esophageal injury. Because of the small sample size and the non-randomized nature of the trials, we observed significant heterogeneity in outcomes among the trials. Conclusion: The role of esophageal temperature monitoring in reducing the risk of esophageal thermal lesions during pulmonary vein isolation for AF has not been established, and more studies including randomized controlled trials are needed to assess its true impact.

Body Temperature Circadian Rhythm Variability Corresponds to Left Ventricular Systolic Dysfunction in Decompensated Cardiomyopathic Hamsters

BACKGROUND A declining amplitude of body temperature circadian rhythm (BTCR) predicts decompensation or death in cardiomyopathic hamsters. We tested the hypothesis that changes in BTCR amplitude accompany significant changes in left ventricular (LV) size and function. METHODS AND RESULTS Using intraperitoneal transmitters, we continuously monitored the temperature of 30 male BIO TO-2 Syrian dilated cardiomyopathic hamsters. Cosinor analysis was used to detect significant changes--defined as changes >1 standard deviation from the baseline amplitude for 3 consecutive days--in BTCR amplitude over each hamsters lifespan. The Student t-test was used to compare BTCR variability and LV size and function (as assessed by 2D echocardiography) between baseline and the time that BTCR amplitude declined. All hamsters received 10 mg/kg furosemide daily. At the time of BTCR amplitude decline, functional parameters had changed significantly (P < .0001) from baseline: ejection fraction (0.31 ± 0.09% vs. 0.52 ± 0.08%), LV end-systolic volume (0.11 ± 0.03 vs. 0.05 ± 0.02 cm(3)), and LV end-diastolic volume (0.16 ± 0.04 vs. 0.10 ± 0.03 cm(3)). CONCLUSIONS In decompensated cardiomyopathic hamsters, a decline in BTCR amplitude was associated with progression of heart failure and cardiac decompensation. Variation in BTCR warrants further investigation because of its potential implications for the diagnosis and treatment of cardiovascular disorders.

Bridging to a Long-Term Ventricular Assist Device With Short-Term Mechanical Circulatory Support: BRIDGING TO A LONG-TERM VENTRICULAR ASSIST DEVICE

Implanting short-term mechanical circulatory support (MCS) devices as a bridge-to-decision is increasingly popular. However, outcomes have not been well studied in patients who receive short-term MCS before receiving long-term left ventricular assist device (LVAD) support. We analyzed outcomes in our single-center experience with long-term continuous-flow (CF)-LVAD recipients with pre-implantation short-term MCS. From November 2003 through March 2016, 526 patients (mean age, 54.7 ± 13.5 years) with chronic heart failure (mean ejection fraction, 21.7 ± 3.6%) underwent implantation of either the HeartMate II (n = 403) or the HeartWare device (n = 123). Before implantation, 269 patients received short-term MCS with the TandemHeart, the Impella 2.5/5.0, an intra-aortic balloon pump (IABP), venoarterial extracorporeal membrane oxygenation (VA-ECMO), or the CentriMag. The short-term MCS patients were compared with the CF-LVAD-only patients regarding preoperative demographics, incidence of postoperative complications, and long-term survival. The 269 patients received the following short-term MCS devices: 57 TandemHeart, 27 Impella, 172 IABP, 12 VA-ECMO, and 1 CentriMag. Survival at 30 days, 6 months, 1 year, and 2 years was 94.2, 87.2, 79.4, and 72.4%, respectively, for CF-LVAD-only patients versus 91.0, 78.1, 73.4, and 65.6%, respectively, for short-term MCS + CF-LVAD patients (P = 0.17). Within the short-term MCS group, survival at 24 months was poorest for patients supported with VA-ECMO or the TandemHeart (P = 0.03 for both), and survival across all four time points was poorest for patients supported with VA-ECMO (P = 0.02). Short-term MCS was not an independent predictor of mortality in multivariate Cox regression models (hazard ratio = 1.12, 95% confidence interval = 0.84-1.49, P = 0.43). In conclusion, we found that using short-term MCS therapy-except for VA-ECMO-as a bridge to long-term CF-LVAD support was not associated with poorer survival.

B-TYPE NATRIURETIC PEPTIDE MAY PROMOTE ARRHYTHMIA IN HEART FAILURE THROUGH INHIBITING TRANSIENT OUTWARD POTASSIUM CURRENT

Background: Elevated B-type natriuretic peptide (BNP) levels were shown to independently predict both the occurrence of sudden cardiac death and ventricular arrhythmia in heart failure (HF) in additional to left ventricular ejection fraction and HF class. Previous studies reported that intravenous BNP (iv-BNP) could improve HF symptoms but was linked with increased risk of death in HF patients. Our study aimed to test whether iv-BNP directly contributes to proarrhythmic effect.