Introduction: The presence of multiple comorbidities increases the risk of all-cause mortality, but the effects of the comorbidity sequence before the baseline date on mortality remained unexplored. This study investigated the relationship between coronary heart disease (CHD), atrial fibrillation (AF) and heart failure (HF) sequence on all-cause mortality risk in type 2 diabetes mellitus. Methods: This study included patients with type 2 diabetes mellitus prescribed antidiabetic/cardiovascular medications in public hospitals of Hong Kong between January 1st, 2009 and December 31st, 2009 with follow-up until death or December 31st, 2019. Cox regression was used to identify comorbidity sequences predicting all-cause mortality in patients with different medication subgroups. Results: A total of 249291 patients (age: 66.0±12.4 years, 47.4% male) were included. At baseline, 7564, 10900 and 25589 patients had AF, HF and CHD, respectively. Over follow-up (3524±1218 days), 85870 patients died (mortality rate: 35.7 per 1000 person-years). Sulphonylurea users with CHD developed later, but insulin users with CHD developing earlier, in the disease course had lower mortality risks. Amongst insulin users with two of the three comorbidities, CHD with preceding AF (hazard ratio [HR]: 3.06, 95% CI: [2.60-3.61], p<0.001) or HF (HR: 3.84 [3.47- 4.24], p<0.001) had a higher mortality. In users of lipid-lowering agents with all three comorbidities, those with preceding AF had higher risk of mortality (AF-CHD-HF: HR: 3.22, [2.24-4.61], p<0.001; AF-HF-CHD: HR: 3.71, [2.66-5.16], p<0.001). Conclusion: The sequence of comorbidity development affects the risk of all-cause mortality to varying degrees in diabetic patients on different antidiabetic/cardiovascular medications.

Introduction: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare cardiac ion channelopathy. This study examined the clinical characteristics, genetic basis, and arrhythmic outcomes of CPVT patients from China. Methods: PubMed and EMBASE were systematically searched for case reports or series reporting on CPVT patients from China until February 19th, 2022 using the keyword “Catecholaminergic Polymorphic Ventricular Tachycardia” OR “CPVT”, with the location limited to “China” OR “Hong Kong” or “Macau” in EMBASE, with no language or publication type restriction. Clinical characteristics, genetic findings, and primary outcome of spontaneous ventricular tachycardia/ventricular fibrillation (VT/VF) were analyzed. Results: A systematic search of the PubMed and Embase databases yielded 1049 and 47 articles, respectively. After the exclusion of overlapping cohorts, a total of 58 unique cases from 15 studies (median presentation age: 8 [5.0-11.8] years old) were included. All patients except for one presented at or before 19 years of age. 56 patients (96.6%) were initially symptomatic. Premature ventricular complexes (PVCs) were present in 44 of 51 patients (86.3%) and VT in 52 of 58 patients (89.7%). Genetic tests were performed on 54 patients (93.1%) with a yield of 87%. RyR2, CASQ2, TERCL, and SCN10A mutations were found in 35 (71.4%), 12 (24.5%), one (0.02%) patient, and one patient (0.02%) respectively. 54 patients were treated with beta-blockers, eight received flecainide, five received amiodarone, two received verapamil and one received propafenone. Sympathectomy (n=10) and implantable-cardioverter defibrillator implantation (n=8) were performed. On follow-up, 13 patients developed VT/VF. Conclusion: This is the first systematic review of CPVT patients from China. Most patients had symptoms on initial presentation, with syncope as the presenting complaint. RyR2 mutation accounts for more than half of the CPVT cases, followed by CASQ2, TERCL and SCN10A mutations.

Previous studies have quantified repolarization variability using time-domain, frequency-domain and non-linear analysis in mouse hearts. Here, we investigated the relationship between these parameters and ventricular arrhythmogenicity in a hypokalaemia model of acquired long QT syndrome. Methods: Left ventricular monophasic action potentials (MAPs) were recorded during right ventricular regular 8 Hz pacing during normokalaemia (5.2 mM [K+]), hypokalaemia modelling LQTS (3 mM [K+]) or hypokalaemia with 0.1 mM heptanol in Langendorff-perfused mouse hearts. Results: During normokalaemia, mean APD was 33.5±3.7 ms. Standard deviation (SD) of APDs was 0.63±0.33 ms, coefficient of variation was 1.9±1.0% and the root mean square (RMS) of successive differences in APDs was 0.3±0.1 ms. Low- and high-frequency peaks were 0.6±0.5 and 2.3±0.7 Hz, respectively, with percentage powers of 38±22 and 61±23%. Poincaré plots of APDn+1 against APDn revealed ellipsoid morphologies with SD along the line-of-identity (SD2) to SD perpendicular to the line-of-identity (SD1) ratio of 4.6±1.1. Approximate and sample entropy were 0.49±0.12 and 0.64±0.29, respectively. Detrended fluctuation analysis revealed short- and long-term fluctuation slopes of 1.62±0.27 and 0.60±0.18, respectively. Hypokalaemia provoked ventricular tachycardia in six of seven hearts, prolonged APDs (51.2±7.9 ms), decreased SD2/SD1 ratio (3.1±1.0), increased approximate and sample entropy (0.68±0.08 and 1.02±0.33) and decreased short-term fluctuation slope (1.23 ± 0.20) (ANOVA, P<0.05). Heptanol prevented VT in all hearts studied without further altering the above repolarization parameters observed during hypokalaemia. Conclusion: Reduced SD2/SD1, increased entropy and decreased short-term fluctuation slope are associated with ventricular arrhythmogenesis in hypokalaemia. Heptanol exerts anti-arrhythmic effects without affecting repolarization variability.

Background: Previous studies have associated slowed ventricular conduction in the arrhythmogenesis mediated by the gap junction and sodium channel inhibitor heptanol in mouse hearts but did not study the propagation patterns that might contribute to the arrhythmic substrate. This study used a multi-electrode array mapping technique, to further investigate different conduction abnormalities in Langendorff-perfused mouse hearts exposed to 0.1 or 2 mM heptanol. Methods: Multi-electrode array recordings were made from the left ventricular epicardium in spontaneously beating hearts, during right ventricular regular 8 Hz pacing or S1S2 pacing. Results: In spontaneously beating hearts, heptanol at 0.1 and 2 mM significantly reduced the heart rate from 314±25 to 189±24 and 157±7 bpm, respectively (ANOVA, P<0.05 and P<0.001). During regular 8 Hz pacing, Mean LATs were increased by 0.1 and 2 mM heptanol from 7.1±2.2 ms to 19.9±5.0 ms (P<0.05) and 18.4±5.7 ms (P<0.05). The standard deviation of mean LATs was increased from 2.5±0.8 ms to 10.3±4.0 ms and 8.0±2.5 ms (P< 0.05), and the median of phase differences was significantly increased from 1.7±1.1 ms to 13.9±7.8 ms and 12.1±5.0 ms by 0.1 and 2 mM heptanol (P<0.05). P5 took a value of 0.2±0.1 ms and was not significantly altered by heptanol at 0.1 or 2 mM (1.1±0.9 ms and 0.9±0.5 ms, P>0.05). P50 was increased from 7.3±2.7 ms to 24.0±12.0 ms by 0.1 mM heptanol and then to 22.5±7.5 ms by 2 mM heptanol (P< 0.05). P95 was increased from 1.7±1.1 ms to 13.9±7.8 ms by 0.1 mM heptanol and to 12.1±5.0 ms by 2 mM heptanol (P<0.05). These changes led to increases in the absolute inhomogeneity in conduction (P5-95) from 7.1±2.6 ms to 31.4±11.3 ms, 2 mM: 21.6±7.2 ms, respectively (P<0.05). The inhomogeneity index (P5-95/P50) was significantly reduced from 3.7±1.2 to 3.1±0.8 by 0.1 mM and then to 3.3±0.9 by 2 mM heptanol (P<0.05). Conclusion: Increased activation latencies, reduced CVs and increased dispersion index of conduction were associated with both spontaneous and induced ventricular arrhythmias.

Introduction: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare cardiac ion channelopathy. The aim of this study is to examine the genetic basis and identify predictive factors for arrhythmic outcomes of CPVT patients from China. Methods: PubMed and MedRxiv were systematically searched for case reports or case series reporting on CPVT patients from China. Clinical characteristics, genetic findings and primary outcome of spontaneous ventricular tachycardia/ventricular fibrillation (VT/VF) were analyzed. Results: A total of 56 (median presentation age=9 [6-13] years old) patients were included. All patients except for one presented at or before 19 years of age. Fifty-three patients (94.6%) were initially symptomatic. PVCs were present in 40 out of 45 patients (88.9%) and VT in 51 out of 56 patients (91.1%). Genetic tests were performed in 50 patients (89.3%). RyR2, CASQ2 and TERCL mutations were found in 32 (57.1%), 11 (19.6%) and one (0.02%) patients, respectively. Fifty patients were treated with beta-blockers, eight patients received flecainide, four patients received amiodarone, two received verapamil and one received propafenone. Sympathectomy (n=10) and implantable-cardioverter defibrillator implantation (n=7) were performed. On follow-up, 17 patients developed incident VT/VF. Conclusion: This is the first systemic review and meta-analysis of CPVT patients from China. Most patients had symptoms on initial presentation, and around a third had VT as the presenting complaint. RyR2 mutation accounts for more than half of the CPVT cases, followed by CASQ2 and TERCL mutations. Some of these mutations have not been hitherto reported outside of China. Most patients received β-blocker therapy. Around 18% had sympathectomy and 13% had ICDs implanted.