Cardiac Markers for Chest Pain Relieved by Nitroglycerin
In patients with chest pain relieved by nitroglycerin, you should obtain serial cardiac troponin I or T levels (preferably high-sensitivity troponin) immediately upon presentation, as nitroglycerin response does not reliably distinguish cardiac from non-cardiac chest pain and should never be used as a diagnostic criterion. 1
Critical Clinical Context
The fact that nitroglycerin relieved this patient's chest pain is diagnostically meaningless and potentially misleading:
- Nitroglycerin relieves chest pain in 35% of patients WITH acute coronary syndrome versus 41% of patients WITHOUT acute coronary syndrome 2, 3, 4
- The American Heart Association and American College of Cardiology explicitly state that relief with nitroglycerin should NOT be used as a diagnostic criterion for myocardial ischemia 1, 2
- Nitroglycerin can relieve non-cardiac chest pain through esophageal smooth muscle relaxation and systemic vasodilation 2
Specific Cardiac Markers to Order
Primary Biomarker (Class 1 Recommendation)
Serial high-sensitivity cardiac troponin (hs-cTn) I or T:
- Measure immediately upon presentation 1
- Repeat serially to detect rising or falling pattern indicative of acute myocardial injury 1
- hs-cTn is superior to conventional troponin assays, enabling more rapid detection/exclusion of myocardial injury with higher sensitivity and negative predictive value 1
- Values >99th percentile upper reference limit (assay-dependent) indicate myocardial injury 1
What NOT to Order (Class 3: No Benefit)
Do NOT order CK-MB or myoglobin:
- These markers are inferior to troponin for diagnosis and prognosis of acute myocardial infarction 1
- Adding CK-MB or myoglobin to troponin provides no additional diagnostic benefit 1
- CK-MB and myoglobin lack cardiac specificity and are hampered by skeletal muscle cross-reactivity 5
Other Biomarkers to Avoid
Do NOT routinely order:
- Natriuretic peptides (BNP/NT-proBNP): Associated with cardiovascular risk but lack sufficient diagnostic accuracy for myocardial injury 1
- Heart fatty acid binding protein (HFABP): Diagnostically inferior to troponin 6
- Copeptin: Not useful in chest pain populations 6
Critical Implementation Details
Assay-Specific Knowledge Required
You must know the specific analytical performance characteristics of YOUR institution's troponin assay 1:
- The 99th percentile upper reference limit (varies by manufacturer)
- Sex-specific thresholds for hs-cTn 1
- Coefficient of variation should be ≤10% at the 99th percentile 1
- Criteria for significant delta (rise/fall pattern)
Timing and Interpretation
- Obtain troponin as soon as possible after presentation 1
- Serial measurements are essential to identify rising or falling patterns that indicate acute injury versus chronic elevation 1
- hs-cTn allows shorter time intervals from symptom onset to detectable concentrations, enabling rapid rule-in/rule-out algorithms 1
Common Pitfalls to Avoid
Troponin Interpretation Challenges
Remember that troponin is organ-specific but NOT disease-specific:
- Elevated troponin can result from numerous ischemic, non-coronary cardiac, and non-cardiac causes of cardiomyocyte injury 1
- Always integrate troponin results with ALL clinical information 1
- Regardless of final diagnosis, myocardial injury (elevated troponin) is associated with higher risk of adverse outcomes 1
The Nitroglycerin Trap
Never delay cardiac evaluation based on nitroglycerin response:
- The European Society of Cardiology explicitly warns that nitroglycerin response "can be misleading" 7
- Even complete symptom resolution after nitroglycerin does not exclude ongoing acute coronary syndrome 7
- Silent ischemia and intermittent coronary occlusion can present with transient symptoms 7
Transfer Delays
For patients initially evaluated in office settings with suspected acute coronary syndrome, delayed transfer to the emergency department for troponin testing should be avoided (Class 3: Harm) 1