How common is undiagnosed coronary artery disease in adult patients with long term type 1 diabetes?

This article investigated the frequency of undiagnosed coronary artery disease (CAD) in patients with long-term type 1 diabetes (T1D). The authors concluded that UCAD was very common and that high cholesterol and HbA1c (a measure of blood glucose control over the past 3 months) were associated with CAD. 

In T1D the body does not make insulin and cannot lower the blood glucose. Long-term high blood glucose damages blood vessels to the heart (coronary arteries) causing CAD. Unfortunately, patients with T1D do not always show symptoms of CAD. This makes it hard to identify them to prevent heart attacks and death. Many patients with T1D also have high cholesterol levels. This also leads to CAD.

HbA1c is a measure of blood glucose control. High cholesterol levels are measured through the low-density lipoprotein cholesterol (LDL-C or bad cholesterol). However, these tests do not also detect CAD. An alternative is to carry out computed tomography coronary angiography (CTCA; pictures of the blood vessels supplying the heart are taken which will show CAD). This technique will show CAD in patients that may not show any symptoms of the disease. The frequency of undiagnosed CAD in patients with long-term T1D remains under investigation.

This study involved 105 patients who had T1D for more than 45 years. These were compared to 63 patients without T1D (control group). 20-30 years data on HbA1c, LDL-C and blood pressure (BP) were analyzed. Patients with T1D that never had CAD diagnosed were given CTCA. The CTCA was looking for undiagnosed CAD (>50% of the artery blocked), absent CAD (no CAD) and obstructive CAD (artery blocked). 

Significantly more patients with T1D had undiagnosed and obstructive CAD compared to controls. 24% of patients with T1D had undiagnosed CAD, 16% had absent CAD and 35% had obstructive CAD. The control group had 10% undiagnosed CAD, 50% absent CAD and 14% obstructive CAD. Patients with elevated HbA1c levels were 2.3 more likely to have undiagnosed CAD. Patients with high LDL-C levels were 88% more likely to have undiagnosed CAD. 

The authors concluded that the undiagnosed CAD was common in patients with T1D and LDL-C and HbA1c were associated with CAD in these patients. 

The controls in this study were mainly relatives and partners to the participants and may not reflect the general population accurately. The control group was small so further studies are needed to confirm the results.