Physiological pacing: just a lot of buzz or the next paradigm shift in bradycardia pacing?

ABSTRACT: Cardiac pacing has been an established therapy for bradyarrhythmia due to sinus or atrioventricular nodal disease since the 1950s. However, contemporary studies have shown that conventional right ventricular pacing (RVP) causes electromechanical dyssynchrony, which can lead to atrial fibrillation, heart failure and even death. Recently, the push for a more physiological cardiac pacing has seen a revival in the utilisation and development of conduction system pacing (CSP). There has been a shift towards adopting His bundle pacing (HBP) or left bundle branch area pacing (LBBaP) in bradycardia patients worldwide and in Singapore. This review serves to outline the electrophysiological concepts behind CSP and illustrate the different paced electrocardiogram characteristics of HBP, LBBaP and RVP to aid understanding of this revolutionary pacing approach among medical practitioners in Singapore.

Predicting atrial fibrillation after ischemic stroke: clinical, genetics and electrocardiogram modelling.

INTRODUCTION: Detection of atrial fibrillation (AF) is challenging in patients after ischemic stroke due to its paroxysmal nature. We aim to determine the utility of a combined clinical, electrocardiographic and genetic variables model to predict AF in a post-stroke population. MATERIALS AND METHODS: We performed a cohort study at a single comprehensive stroke centre from 09/11/2009 to 31/10/2017. All patients recruited were diagnosed with acute ischemic stroke or transient ischemic attacks. Electrocardiographic variables including p-wave terminal force (PWTF), corrected QT interval (QTc) and genetic variables including single nucleotide polymorphisms (SNP) at the 4q25 (rs2200733) were evaluated. Clinical, electrocardiographic and genetic variables of patients without AF and those who developed AF were compared. Multiple logistic regression analysis and receiver operating characteristics were performed to identify parameters and determine their ability to predict the occurrence of AF. RESULTS: Out of 709 patients (median age of 59 years, IQR 52-67) recruited, sixty (8.5%) were found to develop AF on follow-up. Age (odds ratio (OR): 3.49, 95% confidence interval (CI): 2.03-5.98, p<0.0001), hypertension (OR: 2.76, 95% CI: 1.36-5.63, p=0.0052) and valvular heart disease (OR: 8.49, 95% CI: 2.62-27.6, p<0.004 were the strongest predictors of AF, with area under receiver operating value of 0.76 (95% CI: 0.70-0.82), and 0.82 (95% CI: 0.77-0.87) when electrocardiographic variables (PWTF and QTc) were added. SNP did not improve prediction modelling. CONCLUSION: We demonstrated that a model combining clinical and electrocardiographic variables provided robust prediction of AF in our post-stroke population. Role of SNP in prediction of AF was limited.

Rhythm blues in the time of coronavirus disease 2019 (COVID-19): how the cardiac electrophysiologist adapts to a viral pandemic in Singapore.

Coronavirus disease 2019 (COVID-19) is a major healthcare disaster in the modern times. Healthcare services must adapt to effectively juggle between pandemic management and maintenance of business-as-usual services so that both COVID-19 and non-COVID-19 patients receive appropriate clinical care. We share our experience of significant cardiac rhythm abnormalities seen in COVID-19 patients in Singapore, how the viral pandemic has affected the cardiac electrophysiology and pacing service in a large acute care general hospital and the steps taken to alleviate the negative impact.

Toxicity Evaluation and Anti-Tumor Study of Docetaxel Loaded mPEG-Polyester Micelles for Breast Cancer Therapy.

In this work, docetaxel (DTX) was encapsulated in monomethoxy poly(ethylene glycol)-poly(ε-caprolactone) (mPEG-PCL) micelles and monomethoxy poly(ethylene glycol)-poly(D, L-lactic acid) (mPEG-PLA) micelles, respectively. For the further application, the acute/genetic toxicity evaluation and pharmacokinetic/pharmacodynamic study of the two kinds of micellar nanomedicines were performed. In the study of anticancer activity in vitro and in vivo, DTX micelles showed better tumorgrowth inhibition than free DTX. The pharmacokinetic and tissue distribution studies showed that the DTX incorporated in micelles (especially in DTX-mPEG-PCL) retained significantly higher concentration in plasma and tumor tissue compared with free DTX. The acute toxicity and genotoxicity studies indicated that DTX micelles were safer than the docetaxel injection in cancer therapy and DTX-mPEG-PCL had less damage to DNA than DTX-mPEG-PLA. So the micelles had a pronounced effect on reducing acute toxicity and genotoxicity of docetaxel. In conclusion, DTX micelles were efficient and safe on breast carcinoma chemotherapy.

Biodegradable Self-Assembled Micelles Based on MPEG-PTMC Copolymers: An Ideal Drug Delivery System for Vincristine.

Despite advantageous properties, micelles using methoxy poly(ethylene glycol)-poly(trimethylene carbonate) (MPEGPTMC) have not been widely studied. In this work, we aim to develop a novel vehicle for vincristine (VCR) based on a MPEG-PTMC micelle system. MPEG-PTMC with a series of molecular weights were synthesized and screened for the appropriate range for forming stable VCR micelles. The prepared micelles were then characterized in vitro and in vivo . VCR micelles presented high stability and ideal sustained release profile. The passive targeting effect was also enhanced compared with liposomal VCR. These results provide critical data to give the first clues regarding novel VCR micelles which exhibit potential for clinical application.

Modification of charge transport in triphenyldiamine films induced by acid oxidized single-walled carbon nanotube interlayers.

We report the modification of the transport, optical and electrical properties of 200 nm thick N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'biphenyl-4,4'diamine (TPD) films on indium-tin oxide (ITO) when a low density of acid oxidized single-walled carbon nanotubes (o-SWCNTs) are present at the ITO/TPD interface. Most significantly, current-voltage measurements show strong evidence for a change from contact to bulk limited transport. We postulate that these observations result from a change in the structure of the TPD film seeded by the presence of o-SWCNTs at the ITO surface.