IHD vs ACS: What Every Medical Student Should Know

Ischaemic Heart Disease (IHD) and Acute Coronary Syndrome (ACS) are terms that often get used interchangeably—but they’re not the same. If you want to sound like you know what you’re talking about on ward rounds (or ace your exams), here’s what you need to remember.

IHD: The Bigger Picture

IHD is the chronic condition caused by coronary artery atherosclerosis leading to reduced blood supply to the heart muscle. It’s an umbrella term that includes:

✅ Stable angina – Predictable chest pain on exertion that resolves with rest/nitroglycerin

✅ Asymptomatic IHD – Often found incidentally on ECGs or stress tests

Think of IHD as the long-standing process of coronary artery narrowing, which may or may not cause symptoms—until something tips it over the edge…

ACS: When Things Get Serious

ACS is the acute manifestation of IHD due to sudden plaque rupture and thrombus formation. It’s a medical emergency! It includes:

🚨 Unstable angina (UA) – New or worsening chest pain without myocardial infarction

🚨 NSTEMI – Myocardial infarction without ST elevation but with raised troponins

🚨 STEMI – Complete coronary occlusion with ST elevation and myocardial infarction

Why Does This Matter?

❗ Management differs – Stable angina gets long-term risk factor management (statins, aspirin, beta-blockers), whereas ACS needs urgent intervention (DAPT, heparin, reperfusion therapy).

❗ ECG interpretation is key – A patient with exertional angina and a normal ECG is different from a patient with chest pain and ST changes.

❗ Troponins tell a story – Raised troponins = myocardial injury, but always consider the clinical context.

Take-Home Message

✔ All ACS is IHD, but not all IHD is ACS.

✔ Stable angina = predictable, ACS = unpredictable and dangerous.

✔ Timely recognition of ACS saves lives—learn to read ECGs and act fast!

Quick Quiz:

Which of the following best differentiates stable angina from unstable angina?

• A) Stable angina occurs at rest, while unstable angina occurs with exertion.
• B ) Unstable angina is associated with troponin elevation, while stable angina is not.
• C) Stable angina is predictable and relieved by rest, while unstable angina can occur at rest and is more unpredictable.
• D) ST elevation is present in unstable angina but not in stable angina.

💡 Think about how these conditions fit into the bigger picture of IHD and ACS.

Correct Answer: C

✅ Stable angina is predictable, occurs with exertion, and is relieved by rest or nitroglycerin. It results from a fixed atherosclerotic narrowing of coronary arteries and does not indicate an acute event.

✅ Unstable angina is part of ACS. It can occur at rest or with minimal exertion, is less predictable, and may not be relieved by rest or nitrates. It indicates plaque rupture and thrombus formation without complete occlusion.

Why the Other Options Are Incorrect:

❌ A) Stable angina does NOT occur at rest—it happens with exertion. Unstable angina can occur at rest.

❌ 😎 Troponin is NOT elevated in unstable angina—only in NSTEMI and STEMI.

❌ D) ST elevation is NOT seen in unstable angina—ST elevation occurs in STEMI, whereas unstable angina may show ST depression or T-wave changes.

Key Learning Point:

Stable angina = chronic & predictable

Unstable angina = acute & unpredictable (but without myocardial infarction!)

Does this help with the distinction ?