Metaiodobenzylguanidine imaging in diabetes mellitus: assessment of cardiac sympathetic denervation and its relation to autonomic dysfunction and silent myocardial ischemia.

OBJECTIVES

This study in patients with diabetes mellitus was undertaken 1) to evaluate cardiac sympathetic innervation in diabetic patients using metaiodobenzylguanidine (MIBG) imaging; 2) to study the relation between autonomic function assessed by clinical maneuvers and abnormalities in MIBG uptake; and 3) to examine the basis for our previous observation of an association between abnormalities in autonomic nervous system dysfunction and silent myocardial ischemia.

BACKGROUND

The clinical detection of autonomic dysfunction in diabetes mellitus has been linked to both abnormal perception of pain, including angina, and poor prognosis.

METHODS

Uptake of MIBG was measured by dual-isotope imaging in 23 normal subjects and 65 asymptomatic diabetic patients. Silent myocardial ischemia was defined as the presence of a reversible perfusion defect in patients with ST segment depression.

RESULTS

The MIBG uptake in the diabetic patients was significantly lower than that in normal subjects in the apex (67 +/- 17% vs. 82 +/- 7%, p = 0.0001), distal third (77 +/- 11% vs. 85 +/- 3%, p = 0.0001), proximal third (77 +/- 9% vs. 84 +/- 3%, p = 0.0001) and base (71 +/- 9% vs. 80 +/- 4%, p = 0.0001) of the left ventricle. Similarly, MIBG uptake was variable across different vascular territories. When MIBG uptake was corrected for perfusion abnormalities, diabetic patients had a greater MIBG uptake defect than normal subjects on visual score assessment (16 +/- 13 vs. 8 +/- 7%, p = 0.0002) and on quantitative MIBG mismatch assessment (13 +/- 15% vs. 2 +/- 2%, p = 0.0001). Diabetic patients with versus without autonomic dysfunction had more extensive MIBG uptake mismatch (17 +/- 17% vs. 4 +/- 6%, p = 0.0001). There was a greater diffuse abnormality in diabetic patients with versus without silent myocardial ischemia detected by sestamibi/MIBG uptake ratio (68 +/- 35% vs. 19 +/- 33%, p = 0.001).

CONCLUSIONS

Sympathetic cardiac innervation in normal subjects is inhomogeneous. In contrast to normal subjects, diabetic patients have evidence of a significant reduction in MIBG uptake, most likely on the basis of autonomic dysfunction. Furthermore, diabetic patients with silent myocardial ischemia have evidence of a diffuse abnormality in MIBG uptake, suggesting that abnormalities in pain perception may be linked to sympathetic denervation.