Abstract
Over the last 10 years, there has developed an increasing awareness that our diabetes patients have a rising prevalence of myocardial dysfunction accompanied by the development of an array of cardiovascular abnormalities, including both systolic and diastolic heart failure. In the current issue of the Journal, two papers have been presented which characterise different aspects of myocardial function in cohorts of patients with diabetes. Jørgensen et al. 1 describe the prevalence of echocardiographic abnormalities in a large cohort of patients requiring secondary care management of their type 2 diabetes, finding potentially significant abnormalities in almost half. While their cohort is somewhat selected, and not compared with a control group, they reinforce the notion that diabetes is commonly associated with asymptomatic or mildly symptomatic cardiovascular disease, raising many questions about the value of screening. While some of the abnormalities they detected will have been previously diagnosed, they frequently found prognostically significant and treatable cardiovascular disease, including left ventricular (LV) systolic dysfunction (12.5%) and LV hypertrophy (21%). Other markers, including LV diastolic dysfunction (19.4%) and left atrial enlargement (19.6%) and right ventricular dysfunction (14%), while not prompting specific evidence-based prognosis improving interventions, further highlight the adverse impact of diabetes on the heart. Importantly, they found the absence of symptoms, cardiovascular co-morbidity, electrocardiographic abnormalities or markers of nephropathy, individually offered limited capacity to exclude structural heart disease. However, it remains unclear whether combinations of these factors, perhaps in addition to clinically used cardiac biomarkers (such as NT-proBNP), could offer greater reassurance. Cardiac imaging techniques continue to evolve, and it is likely prognostically relevant heart disease would have been more prevalent if echocardiographic speckle tracking methods were adopted to assess LV function.2,3 Moreover, cardiac magnetic resonance imaging is beginning to elicit additional abnormalities of cardiac structure and function in people with diabetes. 4 The paper from Walker et al. 5 describes the results from the study of 628 unselected patients with heart failure of whom 25% had a known diagnosis of diabetes. The results confirmed the adverse risk profile associated with increased mortality in diabetes patients with heart failure and identified evidence of increased pulmonary artery pressure and pulmonary oedoma, and less favourable LV remodelling compared to the non-diabetes cohort. Evidence is accumulating to indicate that there is a common and serious effect of diabetes on myocardial function that contributes to increased morbidity and mortality in this population. The cause of this is probably multifactorial, with insulin resistance, glycation, inflammation and clustering of atheromatous risk all cited as possible culprits. Results from the Diabetes Control and Complications Trial indicated that in Type 1 diabetes subjects, abnormalities in cardiac function correlated with HbA1C but were not ameliorated by improving glycaemic control. 6 This all indicates that we have a relatively recently characterised problem with myocardial dysfunction in diabetes for which we urgently need some answers. These include greater understanding of pathogenesis, the development of novel therapeutic approaches and epidemiological and trial data to inform the continuing debate about screening for asymptomatic cardiac disease in people with diabetes. It seems that as we begin to modify the natural history of some of the microvascular and macrovascular complications of diabetes, another problem requiring our attention arises. However, the emerging data clearly reminds us that diabetes is associated with a distinct cardiovascular phenotype which is easily overlooked, sometimes difficult to diagnose and potentially modifiable which we need to study further as a priority.