Cardiac Autonomic Impacts of Bushfire Smoke-A Prospective Panel Study.

BACKGROUND: Air pollution is associated with cardiovascular disease and mortality. Most studies have focussed on urban or traffic-related pollution, and less is known about the impacts from bushfire smoke on cardiovascular autonomic function, although it is associated with increased sudden cardiac death and mortality. We sought to investigate its instantaneous and short-term impacts on heart rate variability (HRV). METHODS: Twenty-four (24)-hour Holter electrocardiography (ECG) was repeated twice (during bushfire [Phase 1] and then clean air [Phase 2]) in 32 participants from two Australian towns (Warburton and Traralgon, Victoria) surrounding planned burning areas. This was compared with 10 control participants in another town (Maffra, Victoria) with two clean air assessments during the same periods. The primary HRV parameters assessed were those assessing overall HRV (Standard Deviation of Normal-to-Normal intervals [SDNN]), long-term HRV (Standard Deviation of the Average of Normal Sinus-to-Normal Sinus intervals for each 5-minutes [SDANN]), low frequency [LF]) and short-term HRV (Root Mean Square of Successive Differences between N-N intervals [RMSSD], High Frequency [HF], LF:HF ratio). Average concentrations of particulate matter <2.5 µm in diameter (PM2.5) were measured at fixed site monitors in each location. RESULTS: Mean PM2.5 levels were significantly elevated during bushfire exposure in Warburton (96.5±57.7 µg/m3 vs 4.0±1.9 µg/m3, p<0.001) and Traralgon (12.6±4.9 µg/m3 vs 3.4±3.1 µg/m3, p<0.001), while it remained low in the control town, Maffra, in each phase (4.3±3.2 µg/m3 and 3.9±3.6 µg/m3, p=0.70). Although SDANN remained stable in controls, the exposed cohort showed significant worsening in SDANN during bushfire smoke exposure by 9.6±25.7ms (p=0.039). In univariable analysis, smoke exposure was significantly associated with higher ΔSDNN and ΔSDANN (p=0.03, p=0.01 exposed vs control). The association remained significant in ΔSDANN after adjusting for age, sex and cigarette smoking (p=0.02) and of borderline significance in ΔSDNN (p=0.06). CONCLUSIONS: Exposure to the bushfire smoke was independently associated with reduced overall and long-term HRV. Our findings suggest that imbalance in cardiac autonomic function is a key mechanism of adverse cardiovascular effects of bushfire smoke.

Incidence and Predictors of Eosinophilic Myocardial Hypersensitivity in Patients Receiving Home Dobutamine.

ABSTRACT: We sought to examine incidence and predictors of eosinophilic myocardial hypersensitivity (EMH) in a cohort of patients in the home inotrope program of a quaternary cardiac transplant center. Patients on home inotropes with progression to heart transplantation or ventricular assist device (VAD) between January 2000 and May 2020 were included. EMH was diagnosed by the presence of an interstitial predominate eosinophilic infiltrate within the myocardium by experienced cardiac pathologists. From a cohort of 74 patients, 58% (43) were on dobutamine and 42% (31) were on milrinone. Dobutamine was associated with EMH incidence of 14% (6/43), with zero cases in the milrinone cohort. Mean age was 52 ± 12 years, 22% were female. More than half (62%) were nonischemic dilated cardiomyopathies, the remainder were ischemic cardiomyopathy. Dobutamine dose [250 (200-282) vs. 225 (200-291) µg/min] and duration of therapy [41 (23-79) vs. 53 (24-91) days] was similar between those with and without EMH. Median change in eosinophil count was 0.31 × 10 9 /L in the EMH group compared with only 0.03 × 10 9 /L in the non-EMH cohort, P = 0.02. Increase in peripheral eosinophil count of >0.20 × 10 9 /L demonstrated good discrimination between those with and without EMH, c-statistic 0.83 (95% CI 0.66-1.0). Heart failure hospitalization occurred in 83% of the EMH group versus 59% in the non-EMH group, P = 0.26. Requirement for VAD was significantly higher in the EMH group (83% vs. 41%, P = 0.05). In conclusion, EMH occurred in 14% of patients receiving home dobutamine. Rising eosinophil count should prompt physicians to consider EMH and switch to milrinone to avoid possible escalation to VAD.

Levosimendan and Continuous Outpatient Support With Inotropes in Patients With Advanced Heart Failure: A Single-Centre Descriptive Study.

ABSTRACT: To describe the use of levosimendan in a quaternary referral center with a dedicated heart failure service and compare its efficacy and safety to continuous outpatient support with inotropes (COSI) among patients with advanced heart failure (AHF) who require bridge-to-decision (BTD) or bridge-to-transplant (BTT) therapy. This study was a retrospective, single-center, descriptive study of patients with AHF who received either a single levosimendan infusion or COSI between 2018 and 2021. A total of 23 patients received a levosimendan infusion, and 14 were started on COSI. Three indications for levosimendan were identified: (1) to facilitate weaning of continuous inotropes, (2) to augment diuresis in cardiorenal syndrome, and (3) as first-line therapy for cardiogenic shock in selected patients. Eighty-three percent (19 of 23) of patients who received levosimendan survived to discharge, and there were few clinically significant adverse events. Overall survival at 12 months among patients who received levosimendan was 74%. No statistically significant difference in survival was observed at 12 months (P = 0.68) or beyond (P = 0.63) between patients who received levosimendan and were discharged with a plan for BTD or BTT and those who received COSI. Levosimendan is a safe and effective short-term therapy in AHF and offers comparable long-term survival to COSI in patients who require BTD or BTT therapy.

Congenital long QT syndrome: a clinician's guide.

Congenital long QT syndrome (LQTS) is a familial cardiac ion channelopathy first described over 60 years ago. It is characterised by prolonged ventricular repolarisation (long QT on electrocardiography), ventricular arrhythmias and associated syncope or sudden cardiac death. As the most closely studied cardiac channelopathy, over the decades we have gained a deep appreciation of the complex genetic model of LQTS. Variability in genetic expression and incomplete penetrance leads to a heterogeneous phenotype that can be challenging to classify clinically. In recent times, progress has been made in diagnostic method, risk stratification and treatment options. This review has been written as a guide for the general cardiologist to understand the basic pathophysiology, diagnosis and management priorities for the most encountered LQTS subtypes: LQT1, LQT2 and LQT3.