Xinchun Yang

Hydrogen Sulfide Opens the KATP Channel on Rat Atrial and Ventricular Myocytes

Objective: Hydrogen sulfide (H2S), an endogenous gaseous transmitter, was found to protect the heart from various forms of injury, but the underlying mechanism is not known. H2S can open the KATP channel on vascular smooth muscle cells, and the objective of this study was to determine whether H2S can open the KATP channel on myocardiocytes. Methods: The whole-cell patch-clamp technique was used to record IK,ATP and action potentials of atrial and ventricular myocytes isolated from the hearts of male Wistar rats. Sodium hydrogen sulfide (NaHS) was used as a donor of H2S to observe the effect of exogenous H2S on IK,ATP. DL-propargylglycine (PPG), an inhibitor of the synthesis of H2S, was used at a concentration of 200 µM to observe the effect of endogenous H2S on IK,ATP. Results: NaHS at concentrations (in µM) of 9.375, 18.75, 37.5, 75 and 150 increased IK,ATP by 12.8% (p > 0.05), 28.4% (p < 0.05), 38.8% (p < 0.01), 51.2% (p < 0.01) and 58.6% (p< 0.01) on ventricular myocytes, respectively, and by 6.8% (p > 0.05), 10.4% (p > 0.05), 18.9% (p < 0.01), 24.8% (p < 0.01) and 37.2% (p < 0.01) on atrial myocytes, respectively. The H2S-induced decrease in the duration of action potentials (APD90) of ventricular myocytes was concentration-dependent, although only NaHS at a concentration of 150 µM decreased the APD90 significantly (15%, p < 0.05). The H2S-induced decrease in APD90 on atrial myocytes was concentration dependent, but the statistical difference was not significant. Inhibition of IK,ATP by PPG was time dependent and the level of inhibition was: ventricular myocytes, 7% (p > 0.05), 10% (p < 0.05), 15.3% (p < 0.01), 24.0% (p < 0.01) and 28.9% (p < 0.01); atrial myocytes, 15.8% (p > 0.05), 21.3% (p > 0.05), 26.5% (p < 0.01), 34.0% (p < 0.01) and 43.2% (p < 0.01) measured at 5, 10, 15, 20 and 25 min, respectively. The increase in the APD90, by PPG was time dependent for ventricular myocytes [increased by 12.8% (p < 0.05) at 25 min]. The same was true for atrial myocytes, although only the value at 25 min was significant (15%, p < 0.05). Conclusions: H2S decreased the APD90,and both the endogenous and exogenous H2S-induced increase in IK,ATP on both atrial and ventricular myocytes was concentration dependent. These results may help to explain, at least in part, how H2S protects heart cells from various forms of injury.

J wave is associated with increased risk of sudden cardiac arrest in patients with hypertrophic cardiomyopathy

Aims A retrospective, case–control study to investigate the J wave, a J-point elevation on resting 12-lead electrocardiograms, as a risk factor for sudden cardiac arrest (SCA) in patients diagnosed with hypertrophic cardiomyopathy (HCM). Methods Patients with HCM and age- and sex-matched healthy control subjects were recruited, and 12-lead electrocardiograms were performed. The prevalence and related characteristics of J waves were assessed. Patients were followed-up for a mean of 47.9 months. Results Patients with HCM (n = 345) had significantly higher prevalence of J waves than healthy controls (n = 690; 11.6% and 7.1%, respectively). During follow-up, 14 patients with HCM experienced SCA (SCA subgroup). The prevalence of J waves was significantly higher in the SCA subgroup than in the non-SCA subgroup (42.9% and 10.3%, respectively). There were no significant differences between the SCA and non-SCA subgroups in J wave morphology. Conclusion The J wave may be a risk factor for SCA in patients with HCM.

Diagnostic accuracy of coronary CT angiography combined with dual-energy myocardial perfusion imaging for detection of myocardial infarction

The aim of the present study was to evaluate the diagnostic accuracy of second generation dual-energy computed tomography (DECT) myocardial perfusion imaging for the detection of myocardial infarction (MI) in patients with suspected MI. In total, 56 patients underwent DECT. Among those, 40 patients had MI that was detected by catheter coronary angiography and cardiac troponin I elevation and evolution of acute MI detected by electrocardiogram changes. The diagnostic accuracy, including the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for the detection of MI were evaluated, as well as the coronary image quality of coronary artery and radiation dose. The sensitivity, specificity, PPV and NPV for the detection of MI were 95.0, 97.0, 86.4 and 98.9%, respectively. Moreover, the image quality was rated excellent (score 1) in 90.2% (515/571), good (score 2) in 6.5% (37/571), adequate (score 3) in 1.9% (11/571) and non-diagnostic (score 4) in 1.4% (8/571) of the coronary segments. The effective radiation dose was on average 6.1±1.5 mSv (3.1–10.9 mSv). Therefore, combined DE iodine maps and coronary CT angiography using the DECT may provide a high diagnostic accuracy for detecting MI with lower radiation exposure in patients with suspected MI.

Effect of remote ischemic preconditioning on myocardial injury and inflammatory response induced by ablation for atrial fibrillation: A randomized controlled trial

BACKGROUND Remote ischemic preconditioning (RIPC) has been suggested to reduce postoperative release of cardiac and inflammatory markers in patients undergoing cardiac surgery. This study aimed to evaluate the effect of RIPC on nonischemic myocardial damage and inflammatory response in patients undergoing radiofrequency catheter ablation for paroxysmal atrial fibrillation (AF). METHODS Seventy-two patients with drug-refractory paroxysmal AF undergoing radiofrequency catheter ablation were randomized into RIPC or control groups. RIPC (intermittent arm ischemia through four cycles of 5-min inflation and 5-min deflation of a blood-pressure cuff) was performed once daily on 2 consecutive days before the ablation and immediately before ablation. Cardiac troponin-I (cTnI), high-sensitive C-reactive protein (hs-CRP), and interleukin (IL)-6 levels were measured before RIPC/sham RIPC, after the ablation, and 24 and 72h later. The early recurrence of atrial fibrillation (ERAF) in the two groups was observed over the subsequent 3months. RESULTS Radiofrequency ablation resulted in a significant rise in cTnI, hs-CRP, and IL-6 in both groups, which persisted for 72h. The RIPC group showed a lower increase in cTnI (P<0.001), hs-CRP (P=0.003), and IL-6 (P=0.008) than the control and tended to have a lower risk of ERAF (hazard ratio [HR]=0.77, 95% confidence interval [CI]: 0.32-1.88). CONCLUSIONS These results show that RIPC before ablation for paroxysmal AF significantly reduces the increase in cTnI, hs-CRP, and IL-6 associated with the procedure and results in a lower risk of ERAF. These findings suggest that RIPC could provide cardioprotection against nonischemic myocardial damage.

Differentiating origins of outflow tract ventricular arrhythmias: a comparison of three different electrocardiographic algorithms

Our objective is to evaluate the accuracy of three algorithms in differentiating the origins of outflow tract ventricular arrhythmias (OTVAs). This study involved 110 consecutive patients with OTVAs for whom a standard 12-lead surface electrocardiogram (ECG) showed typical left bundle branch block morphology with an inferior axis. All the ECG tracings were retrospectively analyzed using the following three recently published ECG algorithms: 1) the transitional zone (TZ) index, 2) the V2 transition ratio, and 3) V2 R wave duration and R/S wave amplitude indices. Considering all patients, the V2 transition ratio had the highest sensitivity (92.3%), while the R wave duration and R/S wave amplitude indices in V2 had the highest specificity (93.9%). The latter finding had a maximal area under the ROC curve of 0.925. In patients with left ventricular (LV) rotation, the V2 transition ratio had the highest sensitivity (94.1%), while the R wave duration and R/S wave amplitude indices in V2 had the highest specificity (87.5%). The former finding had a maximal area under the ROC curve of 0.892. All three published ECG algorithms are effective in differentiating the origin of OTVAs, while the V2 transition ratio, and the V2 R wave duration and R/S wave amplitude indices are the most sensitive and specific algorithms, respectively. Amongst all of the patients, the V2 R wave duration and R/S wave amplitude algorithm had the maximal area under the ROC curve, but in patients with LV rotation the V2 transition ratio algorithm had the maximum area under the ROC curve.

Alcohol ablation at the posterior papillary muscle prevents ventricular fibrillation in swine without affecting mitral valve function

AIMS Radiofrequency ablation at the posterior papillary muscle (PM) significantly reduced ventricular fibrillation (VF) inducibility in rabbits and dogs, suggesting that PM may be involved in the generation of VF. However, the effect of ablation at the PM on VF inducibility remains unknown in normal intact swine hearts because in this species radiofrequency energy delivered at PM provoked incessant VF. METHODS AND RESULTS Twelve anesthetized swine underwent median sternotomy. Under the ultrasonographic guidance, chemical ablation was performed via injection of dehydrated alcohol into the base of the posterior PM (group PM, n = 6) or anterior wall (control group, n = 6) in the left ventricle. Ventricular fibrillation inducibility and mitral valve function were measured pre- and post-ablation. Hearts were explanted and the ablated myocardium was stained with haematoxylin and eosin. Ventricular fibrillation inducibility was significantly decreased from 100 ± 0% pre-ablation to 11.9 ± 7.8% post-ablation in group PM (P = 0.001), whereas it was not statistically different in the control group (100 ± 0 vs. 92.9 ± 7.1%, pre-ablation vs. post-ablation). Haemorrhage and cellular necrosis was observed in the centre of ablated myocardium and no significant mitral regurgitation was observed following ablation at the posterior PM. CONCLUSION Alcohol ablation of the left posterior PM reduced VF inducibility in normal intact swine hearts, with no significant mitral regurgitation. This suggests that the posterior PM may be involved in the generation of VF, and the recurrence of VF may be prevented by chemical ablation at the posterior PM.

Masquerading bundle branch block as a presenting manifestation of complete atrioventricular block that caused syncope

A 59-year-old male patient was admitted with the main complaints of stuffiness and shortness of breath. An ECG from precordial leads on admission showed masquerading bundle branch block. Syncope frequently occurred after admission. During syncope episodes, ECG telemetry showed that the syncope was caused by intermittent complete atrioventricular block, with the longest RR interval lasting for 4.36 s. At the gap of syncope, ECG showed complete right bundle branch block accompanied by alternation of left anterior fascicular block and left posterior fascicular block. The patient was implanted with a dual-chamber permanent pacemaker. Follow-up of 9 months showed no reoccurrence of syncope.

The Evaluation of Dual-Energy Myocardial Perfusion Imaging for theDetection of Acute Myocardial Infarction by Using the Second GenerationDual-Source CT in a Porcine Model

Objectives: To evaluate the diagnostic accuracy of “one-step” dual-energy combined coronary CT angiography and first-pass myocardial perfusion imaging for the detection of acute myocardial infarction by using the second generation dual-source CT compared with conventional digital subtraction angiography and histopathological findings in a porcine model. Methods: Five minipigs underwent transcatheter embolization of coronary using gelatin sponge to produce acute myocardial infarction. Arterial-phase myocardial DECT imaging were performed prior to and immediately and 24 hours after the procedure. A colour-coded iodine map was used for evaluation of myocardial perfusion defect using the 17-segment model. Two radiologists in consensus interpreted all iodine map imaging studies at DECT and coronary CT angiography images that were acquired during the DECT-acquisition. Statistical analysis for diagnostic accuracy was performed. Results: Following the coronary embolization, DECT iodine maps showed 45 infarcted segments and 40 non infarcted segments. Based on the per-segment analysis, the sensitivity, specificity, positive predictive value and negative predictive value were 93%, 95%, 95% and 93%, respectively. The corresponding values to per-territory analysis were 100%, 86%, 89% and 100% using histopathological findings as the reference standard. The average dose length product (DLP) was 219.4 ± 60.9 mGy.cm (172-321 mGy.cm). Conclusions: Our experimental study demonstrates that “one-step” dual-energy combined coronary CT angiography and first-pass myocardial perfusion imaging provides high diagnostic accuracy for detecting acute myocardial infarction and a comprehensive image quality of coronary artery with a relatively low dose of radiation in a porcine model.