Examining the Time Course of Endothelium-Independent Dilation by Nitroglycerin

Andrea M. Thelen, Aaron S. Kelly, Eric B. Williamson, Donald R. Dengel

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Arterial smooth muscle function is commonly assessed by measuring the dilation response to sublingual nitroglycerin (NTG), and is referred to as endothelium-independent dilation (EID). The time point at which the brachial artery dilates maximally after NTG administration is generally believed to occur somewhere between three and five minutes. The aim of this study was to examine the time course of brachial artery dilation response to a single dose of sublingual NTG to identify the time point at which maximal dilation occurs and to assess factors effecting EID. Endothelial independent dilation was measured in 125 normal, healthy subjects (male = 67, female = 58) via high-resolution ultrasound on the brachial artery. Mean time to maximal EID was 279.0 ± 26.9 s. There was a significant (p < 0.0001) difference between brachial EID at three minutes vs. five minutes post NTG. There was also a significant gender difference in EID response (p < 0.0001). The results of this study indicate that maximal EID occurs approximately five minutes after NTG administration. Measuring EID at three minutes after NTG administration likely underestimates the true dilation capacity of the artery. (E-mail: athelen@stphc.com).

Original languageEnglish (US)
Pages (from-to)1217-1220
Number of pages4
JournalUltrasound in Medicine and Biology
Issue number8
StatePublished - Aug 2008


  • Endothelial-independent dilation
  • Nitroglycerin
  • Smooth muscle function


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