Research Progress of Sodium Channel and Its Anti-arrhythmic Drugs

With the acceleration of population aging,heart disease has been a high priority,and cardiac ion channel research has been one of the hot spots in the field,Sodium ion channels,as the most important class,have been widely concerned.Therefore,this paper briefly introduces and discusses three aspects of the structure and function of sodium ion channels and the development of drug research.

Arrhythmic risk stratification in ischemic,non-ischemic and hypertrophic cardiomyopathy:A two-step multifactorial,electrophysiology study inclusive approach

Annual arrhythmic sudden cardiac death ranges from 0.6%to 4%in ischemic cardiomyopathy(ICM),1%to 2%in non-ischemic cardiomyopathy(NICM),and 1%in hypertrophic cardiomyopathy(HCM).Towards a more effective arrhythmic risk stratification(ARS)we hereby present a two-step ARS with the usage of seven non-invasive risk factors:Late potentials presence(≥2/3 positive criteria),premature ventricular contractions(≥30/h),non-sustained ventricular tachycardia(≥1episode/24 h),abnormal heart rate turbulence(onset≥0%and slope≤2.5 ms)and reduced deceleration capacity(≤4.5 ms),abnormal T wave alternans(≥65μV),decreased heart rate variability(SDNN<70ms),and prolonged QT_(c)interval(>440 ms in males and>450 ms in females)which reflect the arrhythmogenic mechanisms for the selection of the intermediate arrhythmic risk patients in the first step.In the second step,these intermediate-risk patients undergo a programmed ventricular stimulation(PVS)for the detection of inducible,truly high-risk ICM and NICM patients,who will benefit from an implantable cardioverter defibrillator.For HCM patients,we also suggest the incorporation of the PVS either for the low HCM Risk-score patients or for the patients with one traditional risk factor in order to improve the inadequate sensitivity of the former and the low specificity of the latter.

12-lead electrocardiogram features of arrhythmic risk: A focus on early repolarization

The 12-lead electrocardiogram(ECG) is still the most used tool in cardiology clinical practice. Considering its easy accessibility, low cost and the information that it provides, it remains the starting point for diagnosis and prognosis. More specifically, its ability to detect prognostic markers for sudden cardiac death due to arrhythmias by identifying specific patterns that express electrical disturbances of the heart muscle, which may predispose to malignant arrhythmias, is universally recognized. Alterations in the ventricular repolarization process, identifiable on a 12-lead ECG, play a role in the genesis of ventricular arrhythmias in different cardiac diseases. The aim of this paper is to focus the attention on a new marker of arrhythmic risk, the early repolarization pattern in order to highlight the prognostic role of the 12-lead ECG.

Arrhythmic Risk in Paediatric Patients Undergoing Surgical Repair for Pulmonary Atresia with Intact Ventricular Septum

Introduction:While previous studies only focused on the arrhythmic risk associated with specific correction strategies,this study evaluates this risk in a large cohort of paediatric patients with all phenotypes of PA-IVS after surgical repair.Methods:In this single centre observational cohort study,we retrospectively evaluated 165 patients with a diagnosis of PA-IVS and we excluded those with an exclusively percutaneous treatment,patients lost or with insufficient follow-up and those affected by other arrhythmic syndromes.Surgical history and clinical outcomes were reviewed.Results:86 patients were included in the study(54 male[62.8%],mean age 16.4±6.1 years),with median follow-up from definitive repair of 12.8 years(6.4–18.9 years).They underwent three different final repairs:23 patients(26.7%)univentricular palliation,43(50%)biventricular correction,and 20(23.3%)one and a half ventricle correction.Thirteen patients(15%)developed arrhythmia:6 patients(all the subgroups)sinus node disfunction(SND);2(biventricular repair)premature ventricular complexes;2(one and a half ventricle repair)non-sustained ventricular tachycardia;1(biventricular repair)intra-atrial re-entrant tachycardia;1(one and a half ventricle repair)supraventricular tachyarrhythmia;1(biventricular repair)atrial fibrillation.Three patients with SND needed a pacemaker implantation.Only Fontan circulation showed an association with SND,while the other two groups heterogeneous types of arrhythmias.Conclusions:The low arrhythmic risk is related to surgical repair,it does not appear to be associated with native cardiomyopathy,and it appears to increase with length of follow up.Continuous follow-up in specialized centres is necessary to make an early diagnosis and to manage the potential haemodynamic impact at medium-long term.

Ibutilide and novel indexes of ventricular repolarization in persistent atrial fibrillation patients

AIM: To examine the effect of ibutilide on novel indexes of repolarization in patients with persistent atrial fibrillation (AF). METHODS: We studied consecutive patients scheduled for elective electrical cardioversion. Intravenous ibutilide (1+1mg) was administered before the electrical cardioversion while close electrocardiographic (ECG) monitoring was performed. ECG indexes such as corrected QT interval (QTc), the interval from the peak until the end of T wave (Tpe), and the Tpe/QT ratio were measured before ibutilide infusion and 10 min after the end of infusion. RESULTS: The final study population consisted of 20 patients (mean age: 67.1±9.9 years, 10 men). Six patients were cardioverted pharmacologically and did not proceed to electrical cardioversion. Two patientsdeveloped short non-sustained episodes of torsades de pointes ventricular tachycardia. All but one of the aforementioned ECG indexes increased significantly after ibutilide administration. In specific, the QTc interval increased from 442 ± 29 to 471 ± 37 ms (P=0.037), the Tpe interval in precordial leads from 96 ms (range 80-108 ms) to 101 ms (range 91-119 ms) (P=0.021), the Tpe interval in lead Ⅱ from 79 ms (range 70-88 ms) to 100 ms (range 87-104 ms) (P<0.001), the Tpe/QT ratio in precordial leads from 0.23 ms (range 0.18-0.26 ms) to 0.26 ms (range 0.23-0.28 ms) (P=0.028), and the Tpe interval dispersion from 25 ms (range 23-30 ms) to 35 ms (range 27-39 ms) (P=0.012). However, the Tpe/QT ratio in lead II did not change significantly. CONCLUSION: Ibutilide increases the duration and dispersion of ventricular repolarization. The prognostic value of Tpe and Tpe/QT in the setting of drug-induced proarrhythmia needs further study.

Arterial pulsation on a human patient simulator improved students’ pulse assessment

Even with basic cardiovascular lectures, undergraduates do not usually experience the reality of palpation and, therefore, cannot integrate their physiological knowledge. We created a pulse training scenario of human patient simulators (HPS) to recognize and assess the normal and arrhythmic pulse of the radial artery. All 25 participants were recruited as volunteers to the study from the School of Allied Health Sciences, Kitasato University. Participants received training in radial palpation of arrhythmias on HPS. The test scenario included 10 arrhythmic pulses combined with normal pulses and weak pulses. The average examination scores significantly improved, from 23.8 ± 2.8 of the pretest to 72.9 ± 3.4 of the posttest (mean and SE, N = 25, p < 0.00001). A questionnaire and general written comments for the palpation training were positive. The palpation training improved the participants’ assessment of radial pulses.