Impact of type 2 diabetes mellitus in patients with congenital heart disease (CHD): a study from the Australian National CHD Registry

Introduction Congenital heart disease (CHD) affects approximately 1% of live births. Advances in diagnosis and treatment have markedly improved survival, resulting in a growing adult CHD population with an increasing burden of chronic disease. Here we investigate the prevalence and impact of type 2 diabetes mellitus (T2DM) in patients with CHD.Research design and methods Cohort study from the Australian National CHD Registry, linked to national administrative health data. Control patients without T2DM were selected from the Registry and matched 3:1 by age, sex, rurality, and CHD complexity.Results Of the 58 523 individuals with CHD in the registry, 2077 (3.55%) were identified as having T2DM. Median age was 43.1 (IQR 32.0–57.9) years, and 51% were female. T2DM was associated with a hazard ratio for all-cause mortality or heart transplantation of 1.51 (95% CI 1.31 to 1.73; p<0.001). 27.6% of CHD patients with T2DM experienced any major adverse cardiovascular event (MACE) versus 10.2% of controls (p<0.001). Patients with T2DM had a higher MACE rate (rate ratio 2.87, p<0.001) and had more MACE per patient (odds ratio 4.11, p<0.001) compared with controls. Individuals with T2DM also had significantly higher rates of emergency department presentations than controls (incidence rate ratio 2.35, p<0.001) and higher rates of hospital admissions (incidence rate ratio 2.87, p<0.001).Conclusion T2DM in patients with CHD is associated with significantly lower transplant-free survival, substantially increased MACE, and greater healthcare utilization compared to matched CHD controls.