title: Acute hypoglycemia decreases myocardial blood flow reserve in patients with type 1 diabetes mellitus and in healthy humans.
abstract: BACKGROUND
  Hypoglycemia is associated with increased cardiovascular mortality, but the reason for this association is poorly understood. We tested the hypothesis that the myocardial blood flow reserve (MBFR) is decreased during hypoglycemia using myocardial contrast echocardiography in patients with type 1 diabetes mellitus (DM) and in healthy control subjects.
  
  
  RESULTS
  Twenty-eight volunteers with DM and 19 control subjects underwent hyperinsulinemic clamps with maintained sequential hyperinsulinemic euglycemia (plasma glucose, 90 mg/dL [5.0 mmol/L]) followed by hyperinsulinemic hypoglycemia (plasma glucose, 50 mg/dL [2.8 mmol/L]) for 60 minutes each. Low-power real-time myocardial contrast echocardiography was performed with flash impulse imaging using low-dose dipyridamole stress at baseline and during hyperinsulinemic euglycemia and hyperinsulinemic hypoglycemia. In control subjects, MBFR increased during hyperinsulinemic euglycemia by 0.57 U (22%) above baseline (B coefficient, 0.57; 95% confidence interval, 0.38 to 0.75; P<0.0001) and decreased during hyperinsulinemic hypoglycemia by 0.36 U (14%) below baseline values (B coefficient, -0.36; 95% confidence interval, -0.50 to -0.23; P<0.0001). Although MBFR was lower in patients with DM at baseline by 0.37 U (14%; B coefficient, -0.37; 95% confidence interval, -0.55 to -0.19; P=0.0002) compared with control subjects at baseline, the subsequent changes in MBFR during hyperinsulinemic euglycemia and hyperinsulinemic hypoglycemia in DM patients were similar to that observed in control subjects. Finally, the presence of microvascular complications in the patients with DM was associated with a reduction in MBFR of 0.52 U (24%; B coefficient, -0.52; 95% confidence interval, -0.70 to -0.34; P<0.0001).
  
  
  CONCLUSIONS
  Hypoglycemia decreases MBFR in both healthy humans and patients with DM. This finding may explain the association between hypoglycemia and increased cardiovascular mortality in susceptible individuals.
authors.affiliation: Cardiology Department, Poole Hospital NHS Foundation Trust, Longfleet Rd, Poole, BH15 2JB, UK.
authors.forename: Omar
authors.initials: O
authors.lastname: Rana
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Byrne
authors.forename: David
authors.initials: D
authors.lastname: Kerr
authors.forename: David V
authors.initials: DV
authors.lastname: Coppini
authors.forename: Soha
authors.initials: S
authors.lastname: Zouwail
authors.forename: Roxy
authors.initials: R
authors.lastname: Senior
authors.forename: Joe
authors.initials: J
authors.lastname: Begley
authors.forename: Jeremy J
authors.initials: JJ
authors.lastname: Walker
authors.forename: Kim
authors.initials: K
authors.lastname: Greaves
mesh_terms: D000208:Acute Disease; D000328:Adult; D001786:Blood Glucose / Q000032:analysis*; D002097:C-Reactive Protein / Q000032:analysis; D003326:Coronary Circulation; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000503:physiopathology*; D004452:Echocardiography; D019332:Endothelin-1 / Q000097:blood; D004837:Epinephrine / Q000097:blood; D005260:Female; D015309:Glucose Clamp Technique; D006801:Humans; D006946:Hyperinsulinism / Q000503:physiopathology; D007003:Hypoglycemia / Q000209:etiology / Q000503:physiopathology*; D007328:Insulin / Q000097:blood; D008297:Male; D045423:Microbubbles; D016037:Single-Blind Method; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D019332:Endothelin-1; D007328:Insulin; D002097:C-Reactive Protein; D004837:Epinephrine