MI symptoms and Nitroglycerin

[resiliens]

I'm going through Pathoma and noticed it says nitroglycerin doesn't relieve MI symptoms (chest pain, left arm or jaw pain, diaphoresis, dyspnea), although later on, it's mentioned that nitrates are a possible treatment for MI. Can someone please explain this discrepancy to me please?

Thanks fam

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[KGflyboy]

I'm going through Pathoma and noticed it says nitroglycerin doesn't relieve MI symptoms (chest pain, left arm or jaw pain, diaphoresis, dyspnea), although later on, it's mentioned that nitrates are a possible treatment for MI. Can someone please explain this discrepancy to me please?

Thanks fam

Nitrates can help a little, but they may not do much for MI. Patients with stable angina often have complete resolution of symptoms with nitrates. If I have a patient in the ER having anginal type symptoms not relieved by nitroglycerin, I am concerned about unstable angina and stemi. If the pain is relieved by nitrates and doesn't return, it's very likely not an MI. I still give nitrates if the patient has an MI. It may provide partial relief. Then morphine can be added. Those patients will usually continue to have pain until reperfusion occurs with balloon inflation in the cath lab.

 

[lymphocyte]

I'm going through Pathoma and noticed it says nitroglycerin doesn't relieve MI symptoms (chest pain, left arm or jaw pain, diaphoresis, dyspnea), although later on, it's mentioned that nitrates are a possible treatment for MI. Can someone please explain this discrepancy to me please?

Thanks fam

Can you quote where it says "nitroglycerine doesn't relieve MI symptoms"? That's an odd statement.

Nitrates work in multiple ways (dropping preload, reducing afterload, dilating large coronary arteries and arterioles), and they do often relieve symptoms of myocardial ischaemia, though not always. There's also no proven mortality benefit as per GISSI-3 or ISIS-4. For that reason, they're generally for symptomatic relief.

The actual use of nitrates is fairly complicated, and the finer points of using them come out in clinical practice. For example, what if a patient has a hypertensive crisis, develops myocardial ischaemia, and gets dropped off at your doorstep with acute pulmonary oedema? In that case, nitrates might be a life-saving temporising measure to drop ventricular filling and reduce pulmonary congestion. On the other hand, what about a patient with severe aortic stenosis or an evolving inferior infarct--nitrates might actually be quite harmful.

Step 1 doesn't care about any of that. It focuses mainly on mechanism, not treatment. Can you reason through the pathophysiology of what I wrote above? That's what Step 1 is about.

If the pain is relieved by nitrates and doesn't return, it's very likely not an MI. I still give nitrates if the patient has an MI. It may provide partial relief. Then morphine can be added. Those patients will usually continue to have pain until reperfusion occurs with balloon inflation in the cath lab.

One anonymous doctor to another -- this is really bad clinical practice. And morphine is a pretty nasty drug associated with worse outcomes in myocardial ischaemia as per the CRUSADE registry. There's also evidence that morphine interferes with anti-platelet medications. I don't like it. I usually role with a GTN drip after maximal medical therapy.

Henrikson CA, Howell EE, Bush DE, Miles JS, Meininger GR, Friedlander T, Bushnell AC, Chandra-Strobos N. Chest pain relief by nitroglycerin does not predict active coronary artery disease. Ann Intern Med. 2003 Dec 16;139(12):979-86. PMID: 14678917

Parodi G. Chest pain relief in patients with acute myocardial infarction. Eur Heart J Acute Cardiovasc Care. 2016;5(3):277-81.

Shry EA et al. Usefulness of the response to sublingual nitroglycerin as a predictor of ischemic chest pain in the emergency department. Am J Cardiol 2002;90:1264-1266

Steele R, McNaughton T, McConahy M, Lam J. Chest pain in emergency department patients: if the pain is relieved by nitroglycerin, is it more likely to be cardiac chest pain? CJEM. 2006 May;8(3):164-9. PMID: 17320010

 

[KGflyboy]

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[KGflyboy]

One anonymous doctor to another -- this is really bad clinical practice. And morphine is a pretty nasty drug associated with worse outcomes in myocardial ischaemia as per the CRUSADE registry. There's also evidence that morphine interferes with anti-platelet medications. I don't like it. I usually role with a GTN drip after maximal medical therapy. I've also noticed that simple acetaminophen is surprisingly underutilised for non-severe ischaemic chest pain.

Henrikson CA, Howell EE, Bush DE, Miles JS, Meininger GR, Friedlander T, Bushnell AC, Chandra-Strobos N. Chest pain relief by nitroglycerin does not predict active coronary artery disease. Ann Intern Med. 2003 Dec 16;139(12):979-86. PMID: 14678917

Parodi G. Chest pain relief in patients with acute myocardial infarction. Eur Heart J Acute Cardiovasc Care. 2016;5(3):277-81.

Shry EA et al. Usefulness of the response to sublingual nitroglycerin as a predictor of ischemic chest pain in the emergency department. Am J Cardiol 2002;90:1264-1266

Steele R, McNaughton T, McConahy M, Lam J. Chest pain in emergency department patients: if the pain is relieved by nitroglycerin, is it more likely to be cardiac chest pain? CJEM. 2006 May;8(3):164-9. PMID: 17320010

I didn't mean what you read by my response. I agree nitro response cannot reliably differentiate ischemic chest pain from other causes of chest pain reliably. Those articles also don't contradict what I actually wrote. I'm specifically referring to the differences between the varied presentations of ACS and CAD. By definition, stable angina goes away with rest or nitroglycerin... That's the very definition of the disease. So if ischemic chest pain is completely relieved with either rest or nitroglycerin, it is much less likely to be an MI than ischemic chest pain that is progressive despite NTG. I'm specifically referring to patients with typical chest pain here. If someone comes in with gradually increasing, sharp, pleuritic chest pain, reproducible with movement, began a day after hitting the gym for the first time in years, I would not interpret a lack of response to nitro as evidence of MI. Same patient comes in diaphoretic, nauseated, sudden onset radiating substernal pressure, says the first nitro took the edge off but came right back and is getting worse... MI would be higher on the differential.

To reiterate, nitroglycerin response is NOT a reliable way to distinguish cardiac from non cardiac pain. However, in the the right patient with the right presentations, it absolutely is relevant. A patient with unstable angina should be treated differently than a patient with stable angina.

The morphine - platelet stuff is good to keep in mind. I personally think the benefits and risks can favor using morphine in patients with severe pain not improved with other drugs.

 

[KGflyboy]

And morphine is a pretty nasty drug associated with worse outcomes in myocardial ischaemia as per the CRUSADE registry. There's also evidence that morphine interferes with anti-platelet medications. I don't like it. I usually role with a GTN drip after maximal medical therapy. I've also noticed that simple acetaminophen is surprisingly underutilised for non-severe ischaemic chest pain.

I read the actual article cited within the CRUSADE publication that was used to make conclusions about morphine, and it's not very convincing. Are there randomized controlled trials addressing this topic? It looked at a patient population with NSTEMI who received morphine within 24 hours. It did not control for many factors... for instance maybe people who got morphine were more likely to be the people with more severe presentations. I'm pretty sure I could find data that says trauma patients given IV narcotics do worse than patients given po ibuprofen. No one would conclude that narcotics caused the worse outcomes. The person with multiple fractures and positive fast exam would get the narcotics, and the person with no visible injuries who walked in to get "checked out" after a minor MVC would get the ibuprofen. You would need a randomized, controlled trial to make such conclusions.

The following comment was submitted to NEJM to counter the CRUSADE conclusions about morphine.

COMMENT

1. James M. Christenson, MD, FRCPC

Although this study was retrospective, the CRUSADE data were collected prospectively, and the authors used explicit common definitions. However, this study does not allow us to conclude that morphine is or is not harmful, because use of morphine was at the clinician’s discretion; therefore, it is possible that patients who did and did not receive morphine differed in ways that were not captured in the registry. It is also possible, though, that morphine might have a negative effect on clinical outcomes. For example, morphine might mask symptoms, thus delaying antiplatelet therapy or percutaneous coronary intervention; or unexpected hypotension or respiratory depression might worsen outcomes in some patients. While we await a prospective trial, it seems prudent to use morphine judiciously for pain control and to carefully monitor side effects and ongoing ischemia, ensuring timely and effective use of evidence-based interventions.

 

[alkylate]

Aren't nitrates contraindicated in R-sided heart attacks since they're preload dependent?

 

[Instatewaiter]

Aren't nitrates contraindicated in R-sided heart attacks since they're preload dependent?

Yes

 

[Instatewaiter]

By definition, stable angina goes away with rest or nitroglycerin... That's the very definition of the disease. So if ischemic chest pain is completely relieved with either rest or nitroglycerin, it is much less likely to be an MI than ischemic chest pain that is progressive despite NTG.

Not all typical ischemic chest pain which is relieved by nitroglycerin is stable angina. I have seen tons of people with stuttering angina who were found to have hazy thrombus on cath (closer to STEMI physiology and a type of unstable angina) and those with true NSTEMIs who had relief with NTG. The evaluation of chest pain is all about the story.

With regard to morphine in chest pain, I don't use it. If someone is having continued ischemic pain, I want to know about it because if despite heparin, DAPT and IV nitro they are still having pain, I am taking them to the cath lab overnight. I don't want to mask their pain and I don't want to knock them out so they can't tell me about their continued chest pain.

 

[KGflyboy]

Not all typical ischemic chest pain which is relieved by nitroglycerin is stable angina.

I agree... I never said it was. I said the exact inverse of that statement. All stable angina is relieved by something... whether it is rest or nitro... That's the definition. The aggrevating and alleviating factors are just a piece of the larger story which when combined can be helpful in evaluating chest pain. Timing of symptoms, context, and the rest of the story all matter. None of which can rule in or out any etiology, but they sure can be used to assess pretest and post test probability when working up or dispositioning undifferentiated chest pain.