Abstract

Objective: In this study we evaluated regional myocardial blood flow (MBF) and left ventricular (LV) sympathetic innervation using positron emission tomography (PET) and its relationship to standard autonomic function tests (AFT).

Methods: We studied 12 diabetic patients (7M, 5F) (mean age 62±8), and 5 healthy controls (2M, 3F) (mean age 59±10). All patients underwent AFT and cardiac PET imaging with oxygen-15 labeled water to measure myocardial blood flow (MBF) and carbon –11 hydroxyephedrine (HED) to assess presynaptic cardiac sympathetic nerves. HED images were read semiquantitatively (summed score 4 segment/4 point model) and quantitatively (3-compartment model) to quantify cardiac HED density and flux (B-max). Single compartment model was used for MBF quantification.

Results: All 5 controls had normal MBF, homogeneous uptake of HED, no regional difference in B-max and normal AFT. All 12 diabetic patients had normal MBF, 5 had homogeneous uptake of HED and 7 had heterogeneous uptake. The average HED defects summed score in diabetic patients was 9 in apical, 15 in basal lateral, 11 in distal lateral and 0 in septal region. In heterogeneous group there was a significant difference in B-max between the septal and lateral wall regions (24±12 vs.18 ± 10). On AFT all 12 diabetic patients had normal resting heart rate, RR and normal postural heart rate variability but 6/12 had postural hypotension. All 6 of these patients had heterogeneous HED uptake.

Conclusions: Diabetic patients exhibited LV sympathetic dysfunction predominantly in the lateral wall region and only postural hypotension was significantly correlated with it.

Keywords: Myocardial blood flow, cardiac sympathetic innervation, positron emission tomography, diabetes mellitus, carbon-11 hydroxyephederine