Determinants of orthostatic hypotension in type 2 diabetes: is cardiac autonomic neuropathy the main factor?

OBJECTIVES: To evaluate the determinants of orthostatic hypotension (OH) in type 2 diabetes (T2D) and the usefulness of ΔHR/ΔSBP, index of cardiac baroreflex function, in identifying neurogenic OH.

METHODS: In 208 participants with T2D, we performed three heart rate based cardiovascular reflex tests (HR-CARTs) and OH test and assessed clinical history and variables. We defined OH as a systolic blood pressure (BP) fall ≥20 and ≥30 mmHg with supine BP <140 and ≥140 mmHg, respectively, and early and confirmed CAN based on 1 and 2 abnormal HR-CARTs. In participants with OH, we measured ΔHR/ΔSBP, using data from the lying to standing and OH test, and its diagnostic accuracy for neurogenic OH (as OH plus confirmed HR-CAN).

RESULTS: OH was present in 25 participants and associated with lower HR-CARTs (P=0.01), higher HbA1c (P=0.0048), presence of CAN (P=0.0058), retinopathy (P=0.037), and peripheral vascular disease (P=0.0056), absence of hypertension (P=0.0008) and physical activity (P=0.0214), but not with interfering drugs and beta-blockers. In a multiple logistic regression, HR-CAN was the main independent determinant of OH (odds ratio: 4.74) with physical activity and hypertension (odds ratio: 0.16 and 0.23) (R2=0.22). ΔHR/ΔSBP had a good diagnostic accuracy for neurogenic OH (AUC: 0.816±0.087), and at the cut-off of 0.5 bpm/mmHg a sensitivity of 100% and specificity of 63.2%.

CONCLUSION: CAN is still the main determinant of OH in T2D but does not explain all its variance with contribution of comorbidities and physical inactivity. The index ΔHR/ΔSBP might represent a useful clinical tool to identify neurogenic OH.