What is the difference between coronary artery disease (CAD) and ischaemic heart disease (IHD), and when should each term be used in patients with suspected or confirmed cardiovascular disease?

Understanding the Terminology: Coronary Artery Disease vs. Ischaemic Heart Disease

Direct Answer

Use "coronary artery disease" (CAD) when referring specifically to atherosclerotic plaque accumulation in the coronary arteries, and use "ischaemic heart disease" (IHD) as the broader umbrella term that encompasses all conditions causing myocardial oxygen supply-demand mismatch, including but not limited to CAD. 1, 2

The Key Distinction

Coronary Artery Disease (CAD)

• CAD specifically describes the anatomical pathology: atherosclerotic plaque accumulation in the epicardial coronary arteries that may or may not cause flow limitation 1, 2
• Use this term when discussing:
  • Angiographic findings of coronary stenosis 1
  • Plaque burden and atherosclerotic disease progression 1
  • Obstructive vs. non-obstructive coronary lesions 1
  • Results from coronary CT angiography or invasive angiography 3, 4

Ischaemic Heart Disease (IHD)

• IHD is the broader clinical syndrome: encompasses all mechanisms causing myocardial ischaemia, not just epicardial coronary atherosclerosis 2, 5
• Use this term when discussing:
  • The overall clinical condition causing myocardial oxygen supply-demand mismatch 1, 2
  • Patients with angina who may have CAD, microvascular disease, or vasospastic disease 1, 5
  • Functional consequences of reduced myocardial perfusion regardless of cause 2, 5

Modern Terminology Evolution

The ESC now prefers "chronic coronary syndromes" (CCS) over "stable CAD" or "stable IHD" to emphasize that CAD is a dynamic process that can be modified by treatment, not truly "stable" 1. This terminology shift recognizes that:

• Clinical presentations are categorized as either acute coronary syndromes (ACS) or chronic coronary syndromes (CCS) 1, 2
• The disease process involves ongoing atherosclerotic plaque accumulation and functional alterations that can stabilize or regress with therapy 1, 2

Clinical Application Examples

When CAD is the Correct Term:

• "The patient has severe three-vessel CAD on angiography" 1, 4
• "Coronary CTA revealed non-obstructive CAD with calcified plaque" 3
• "High clinical likelihood of obstructive CAD warrants invasive evaluation" 1

When IHD is the Correct Term:

• "The patient presents with stable IHD manifesting as exertional angina" 1, 6
• "Risk stratification in patients with suspected IHD" 1
• "IHD may result from epicardial CAD, microvascular dysfunction, or coronary vasospasm" 5, 7

Important Nuance: Not All IHD is CAD

Approximately 40% of patients with angina and suspected IHD do not have obstructive CAD on angiography 7. These patients may have:

• Coronary microvascular disease (CMD) causing ischaemia without epicardial obstruction 7
• Vasospastic angina from coronary artery spasm 1, 5
• Endothelial dysfunction affecting myocardial perfusion 1, 5

This distinction matters clinically because coronary CTA is insensitive for detecting CMD, and functional testing is required to diagnose microvascular ischaemia 7.

Practical Pitfall to Avoid

Do not use CAD and IHD interchangeably when discussing diagnostic testing results. For example:

• A patient with positive stress test has "suspected IHD" requiring further evaluation 1
• Only after angiography confirms epicardial stenosis can you definitively diagnose "obstructive CAD" 1, 4
• If angiography shows no obstruction but ischaemia persists, the patient has "IHD without obstructive CAD," likely from microvascular disease 5, 7