(273) Diabetic Cardiovascular Autonomic Neuropathy Unmasked After Cardiac Bypass Surgery

Introduction: Cardiovascular Autonomic Neuropathy (CAN) is the impairment of cardiovascular autonomic control from long-standing diabetes. CAN is present in up to 65% of diabetic patients, with prevalence increasing with age and poor glycemic control. In the setting of the intensive care unit (ICU), awareness of CAN is important as it correlates with increased morbidity and mortality, vasopressor need, and ICU length of stay.

Description: A 58-year-old male with history of insulin-dependent diabetes (HbA1C of 12.9), diabetic neuropathy, and gastroparesis presented with non-ST segment elevation myocardial infarction. Left heart catheterization demonstrated multivessel coronary artery disease and he underwent a 4-vessel coronary artery bypass graft and left atrial appendage excision. His postoperative course was complicated by pericarditis and reduced right ventricular function that quickly resolved. However, he continued to have multiple episodes of asymptomatic hypotension associated with bradycardia (MAPs in the 40s and heart rate of 30s), that required prolonged vasopressor use and fluid boluses. These episodes correlated with mobilizing, stripping of drains, and position changes. When tested with a Valsalva maneuver and positional changes, he developed hypotension and bradycardia which gradually resolved over several minutes without reflexive hypertension. Considering the patient’s history of diabetic neuropathy and gastroparesis, it was evident that these episodes were likely due to CAN. Patient was placed on midodrine with resolution of these episodes.

Discussion: In CAN, the tachycardic response needed to maintain cardiac output is blunted, and therefore there is an inappropriate response. Clinical manifestations of CAN include exercise intolerance, resting tachycardia, orthostatic hypotension, orthostatic tachycardia and bradycardia, silent myocardial infarctions, and perioperative cardiac instability. For diagnosis, the gold standard is to measure the change in heart rate and blood pressure with physiological maneuvers. These can include a deep breathing test, Valsalva maneuver, lying-to-standing test, and measuring blood pressure response to positioning. Although our patient was asymptomatic, his frequent episodes of hypotension and bradycardia led to prolonged vasopressor use and ICU stay.