15 Lead ECG and Nitroglycerin Clarification

Submission ID: 4

Question:

 

As per NWRPCP, if there is ST-elevation in the inferior leads (II, III, aVF) we are automatically out of our Nitroglycerine protocol despite determining if has right ventricular involvement. This has lead me to believe that we shouldn't perform a 15-lead to determine symptom relief administration. If we have a normal ECG but notice depression in V3 & V4 (anterior leads), and we perform a 15 lead to check for reciprocal changes that might indicate a posterior STEMI? Are we indicated to administer nitroglycerin for a posterior STEMI that doesn't have V4R involvement? My understanding is that V4R determines if the right ventricle is involved so if V4R is normal, wouldn't we just have a normal posterior MI?

Answer:

Thank you for your question!
Yes, presently the direction from NWRPCP is that if a patient is found to have ST-elevation in the inferior leads (II, III, aVF) that nitrates would be contraindicated and therefore, not considered as a co-treatment in the presence of cardiac ischemia. While there is no current direction with respect to performing a 15 lead in the field, we would certainly support such an intervention if you feel that it may assist in your differential diagnosis. This of course would not currently impact your ability to provide symptom relief. To answer your specific question regarding an isolated posterior MI. If you have findings suggestive of posterior involvement (Horizontal ST depression, Tall broad R waves, Upright T waves in Leads V1-V4), and determine there to be at least 0.5mm of ST elevation in a single modified lead (V8, V9), you would be within your ability to treat with nitroglycerin. Of course this would be determinate on there being no right ventricular involvement as indicated by a negative V4R capture. However, caution must be exercised as isolated posterior MI’s are less common and usually occur in the context of a lateral or inferior MI. In the end, the focus of your treatment for cardiac ischemia should always be on the administration of ASA.
Furthermore, the rationale for capturing a 15 lead ECG in the field is not solely for the purpose of determining symptom relief administration but to also provide the most accurate information to the receiving facility as this may very well impact their treatment process.

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