P5 Clinical utility of stress echocardiography in remote indigenous and non-indigenous populations: a 10-year study in central Australia

Background

Central Australia is a vast, geographical region spanning some 830,000 square kilometres. It is the most populous Indigenous region in Australia (44%) and a great distance from tertiary centres (1,500km). Non-invasive testing is important in this setting due to the high prevalence of cardiovascular disease and long-distance travel required for coronary angiography, the latter with significant logistical, financial, and cultural barriers. Although stress echocardiography has been extensively validated as a long-term prognostic tool in selected populations, we are not aware of prior studies in remote Indigenous and non-Indigenous individuals.

Purpose

To determine whether stress echocardiography can adequately risk stratify and quantify the long-term prognosis of Indigenous and non-Indigenous individuals in remote Central Australia.

Methods

Consecutive individuals undergoing stress echocardiography in Central Australia between 2007 and 2017 were included. Exercise or dobutamine stress echocardiography was performed and reported via standard protocols.  Individuals were followed up for the primary outcome of all-cause mortality.

Results

One thousand and eight patients (54% Indigenous, 63% dobutamine stress) were included. Indigenous patients were younger, more likely to be female, and had a greater prevalence of cardiometabolic comorbidities (p < 0.05 for all). Overall, 797 (79%) patients had no abnormality during rest or stress echocardiography, with no difference according to ethnicity (p > 0.05).  After a mean follow up of 3.5 ± 2.4 years, 54 (5%) of patients were deceased; 127 (14%) patients underwent revascularization and were censored from follow-up. In patients with a normal test, annual mortality averaged 1.3% over 5 years of follow up, with annual mortality being significantly higher in Indigenous compared to non-Indigenous individuals (2.0% vs 0.6% respectively). Individuals with either ischemia or scar had a significantly worse long-term outcome compared to those with a normal test (Figure). In multivariate analyses, increasing age (HR 1.04 [95% CI 1.01-1.08]), chronic kidney disease (HR 4.83 [1.79-13.02]), and lack of ACEI/ARB use (HR 0.19 [95% CI 0.09-0.42]) were associated with all-cause mortality. Although Indigenous ethnicity was a univariate predictor of mortality, this association was attenuated and non-significant in multivariate analyses.

Conclusion

Indigenous patients in remote Central Australia with a normal stress echocardiogram had a significantly higher annual rate of mortality compared to their non-Indigenous counterparts. However, this association may be in large part due to comorbid conditions. A normal test in Indigenous individuals was still able to adequately risk-stratify and identify a lower risk group of patients in whom ongoing local medical management and focusing on cardiometabolic risk factor reduction is likely to be appropriate.

Abstract P5 Figure. Kaplan Meier survival curve

P2498Exercise capacity and all-cause mortality in remote Indigenous and non-Indigenous populations

Background

Exercise capacity is a powerful predictor of all-cause mortality. However, its association with Indigenous populations in Central Australia, who face disproportionate health burdens, is unclear. Given the isolation from tertiary centers, exercise testing could provide useful local risk-stratification.

Purpose

To characterize the association of exercise capacity with all-cause mortality in Indigenous and non-Indigenous individuals in remote Central Australia.

Methods

Demographic, medication, and all-cause mortality data were prospectively collected from patients undergoing exercise stress tests from 2007–2017.

Results

A total of 3,414 patients (34% Indigenous) were included. At 4.8±2.9 years of follow-up, 86 (2.5%) deaths had occurred. Each 1-MET increase in exercise capacity conferred a 14% lower risk for mortality among Indigenous individuals (HR 0.86, 95% CI 0.79–0.94) and 20% lower risk for mortality among non-Indigenous individuals (HR 0.80, 95% CI 0.73–0.89) after adjusting for age, comorbidities, and medications. Mortality risk reduction for each 1-MET increase in exercise capacity was similar (p=0.32) for Indigenous and non-Indigenous individuals.

Conclusions

Exercise capacity is a significant predictor of all-cause mortality in Indigenous and non-Indigenous individuals. These findings have important clinical implications towards exercise capacity for risk-stratification and preventative importance of physical activity.

Associations of mortality and cardiovascular disease risks with diabetes and albuminuria in urban Indigenous Australians: the DRUID follow-up study

AIM

To assess the relationships of diabetes and albuminuria with all-cause mortality and cardiovascular disease outcomes in a population without prior cardiovascular disease using data from the Darwin Region Urban Indigenous Diabetes (DRUID) study.

METHODS

We conducted a prospective cohort study of 706 participants (aged 15-81 years, 68% women) without prior cardiovascular disease who underwent a 75-g oral glucose tolerance test. Deaths and fatal or non-fatal cardiovascular disease were determined over 7 years, and hazard ratios with 95% CIs and population attributable risks were estimated for baseline glycaemia and albuminuria.

RESULTS

Compared with normoglycaemia and after adjustment for age, sex, hypertension, dyslipidaemia and smoking, known diabetes was associated with an adjusted hazard ratio of 4.8 (95% CI 1.5-14.7) for all-cause mortality and 5.6 (95% CI 2.1-15.2) for cardiovascular disease. Compared with normoalbuminuria, the respective adjusted risks for macroalbuminuria were 10.9 (95% CI 3.7-32.1) and 3.9 (95% CI 1.4-10.8). The Adjusted all-cause mortality and cardiovascular disease estimated population attributable risks for diabetes were 27% and 32%, and for albuminuria they were 32% and 21%, respectively.

CONCLUSIONS

In our study population, the burden of mortality and cardiovascular disease was largely driven by diabetes and albuminuria. This finding on the influence of diabetes and albuminuria is consistent with reports in other high-risk Indigenous populations and should be better reflected in risk scores and intervention programmes.

Northern Territory perspectives on heart failure with comorbidities – understanding trial validity and exploring collaborative opportunities to broaden the evidence base

Congestive Heart Failure (CHF) is an ambulatory care sensitive condition, associated with significant morbidity and mortality, rarely with cure. Outpatient based pharmacological management represents the main and most important aspect of care, and is usually lifelong. This narrative styled opinion review looks at the pharmacological agents recommended in the guidelines in context of the Northern Territory (NT) of Australia. We explore the concept of validity, a term used to describe the basis of standardising a particular trial or study and the population to which it is applicable. We aim to highlight the problems of the current guidelines based approach. We also present alternatives that could utilise the core principles from major trials, while incorporating regional considerations, which could benefit clients living in the NT and remote Australia.