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MONA (and THROMBINS2) for the USMLEs

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by Alec Palmerton, MD in Cardiovascular

If you’re a med student, you’ve probably heard of MONA – or its variant MONA Hep B. Maybe you’re vaguely aware of what it means or when you should use it. Or maybe you know what it stands for but struggle to remember – or understand – it. You may already know that the MONA isn’t “evidence-based” or that there is a new mnemonic – THROMBINS2 – you should know.

Summary:

  • MONA (Hep B) is a mnemonic used for interventions for ACS (Acute Coronary Syndromes)
  • The common pathophysiology of ACS – which include unstable angina, myocardial infarction, and sudden cardiac death – is a coronary plaque rupture
  • Experts discourage MONA’s use due to much of it not being supported by data
  • The THROMBINS2 mnemonic replaces the MONA mnemonic
  • “Ischemia = Demand > Supply” can be used to explain and understand ACS and the rationale for each of the THROMBINS2 and MONA Hep B components

 

Table of Contents

What is MONA (Hep B)?

MONA – and its variant MONA Hep B – is a mnemonic used to remember the interventions used in Acute Coronary Syndromes (ACS), which comprise unstable angina, myocardial infarction, and sudden cardiac death.

How Can I Understand ACS Conceptually?

The Core Concept behind ACS is Ischemia = Demand > Supply.

In other words, when the demand for blood/nutrients exceeds the supply of blood/nutrients, it leads to ischemia. This mismatch can occur because:

  • Demand increases in the heart (e.g., there is pain + sympathetic surge → heart rate ↑, contractility ↑ → demand for O2 and nutrients ↑) and/or
  • Supply decreases (e.g., a plaque ruptures in the coronary artery → thrombus formation → supply of blood to myocardium ↓)

ACS, at its core, involves a form of “supply ischemia” where a coronary artery thrombus forms and blocks the blood supply to the myocardium. Coronary arteries supply the myocardium (heart muscle) with blood. Therefore, if there is a blockage of blood from the coronaries, it will lead to ischemia.

How Can I Understand MONA Conceptually?

MONA Hep B stands for:

  • Morphine
  • Oxygen
  • Nitroglycerin
  • Aspirin
  • Heparin
  • Beta-blockers

We can use the previous schema of Ischemia = Demand > Supply to understand the various interventions:

InterventionEffectMechanism
MorphineDemand ↓Pain relief → pain / anxiety ↓ → sympathetic tone ↓ → myocardial demand ↓
OxygenSupply ↑O2 content of blood ↑ → supply of O2 ↑
NitroglycerinDemand ↓Venodilation e.g., in lower extremities → pooling of blood → venous return ↓ → preload ↓ → myocardial stretch ↓ → wall tension ↓ → demand ↓
AspirinSupply ↑Mitigation of further spread of coronary artery thrombus → blood supply ↑
HeparinSupply ↑Mitigation of further spread of coronary artery thrombus → blood supply ↑
Beta blockersDemand ↓Contractility and HR ↓ → demand ↓
Are We Still Supposed to Use MONA?

As a mnemonic, MONA is helpful for us to understand some of the interventions for ACS. However, as an evidence-based tool, it has fallen short. In its place, some experts recommend the mnemonic THROMBINS2. (Because where would we be without clever cardiology mnemonics?)

How Can I Understand THROMBINS2 Conceptually?

THROMBINS2 stands for:

  • Thienopyridines – adenosine diphosphate (ADP) receptor antagonists like prasugrel and clopidogrel
  • Heparin/enoxaparin
  • Renin-angiotensin system blockers – e.g., ACE-inhibitors (angiotensin-converting enzyme inhibitors) or ARBs (angiotensin receptor blockers)
  • Oxygen
  • Morphine
  • Beta-blocker
  • Intervention – e.g., stent, coronary artery bypass graft, etc. to “revascularize” and restore/increase the supply of blood
  • Nitroglycerin
  • Statin/Salicylate

Thankfully, we can use our prior schema to understand these interventions:

InterventionEffectMechanism
Thienopyridines (e.g., prasugrel, clopidogrel)Supply ↑Mitigation of further spread of coronary artery thrombus → blood supply ↑
Heparin/enoxaparinSupply ↑Mitigation of further spread of coronary artery thrombus → blood supply ↑
Renin-angiotensin system blockersDemand ↓Angiotensin II effect ↓ → afterload ↓ → myocardial demand ↓
OxygenSupply ↑O2 content of blood ↑ → supply of O2 ↑
MorphineDemand ↓Pain relief → pain / anxiety ↓ → sympathetic tone ↓ → myocardial demand ↓
Beta blockerDemand ↓Contractility and HR ↓ → demand ↓
Intervention (e.g., stent, CABG)Supply ↑"Revascularization" = restore blood flow → supply ↑
NitroglycerinDemand ↓Venodilation e.g., in lower extremities → pooling of blood → venous return ↓ → preload ↓ → myocardial stretch ↓ → wall tension ↓ → demand ↓
StatinSupply ↑Reduce risk of future coronary artery thrombus → maintain blood supply
SalicylateSupply ↑Mitigation of further spread of coronary artery thrombus → blood supply ↑

MONA Hep B and THROMBINS2 – What Should I Know for the USMLEs?

Ischemic heart disease is an essential topic for the USMLEs. As such, Step 1 will test your mastery of the topic, including the pathophysiology, presentation, and risk factors. The Core Concept of Ischemia = Demand > Supply will help you see the underlying structure of the disease.

For Step 2 CK, THROMBINS2 will help you remember ACS management, which is an important topic on the exam. With cardiology being up to 9% of Step 1 and 10% of Step 2 CK, mastering this critical topic will help you more confidently get questions correct.

Want Free Anki Cards to remember THROMBINS2, MONA Hep B, and the pathophysiology of ACS? Sign up for the newsletter for free Anki cards to help you master – not memorize – for impressive Boards scores and more meaningful careers.

References:

Kline KP, Conti CR, Winchester DE. Historical perspective and contemporary management of acute coronary syndromes: from MONA to THROMBINS2. Postgrad Med. 2015;127(8):855-862. doi:10.1080/00325481.2015.1092374

 

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Want FREE Cardiology Flashcards?

Cardiology is key for impressive USMLE scores. Master cardiology from a Harvard-trained anesthesiologist who scored USMLE 270 with these 130+ high-yield flash cards. You’ll be begging for cardio questions - even if vitals make you queasy.

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