Ischemic heart disease (IHD) and coronary artery disease (CAD) are essentially the same condition, and the terms are used interchangeably across most of medicine. Both refer to heart problems caused by narrowed coronary arteries that reduce blood flow to the heart muscle. You’ll also see “coronary heart disease” (CHD) used as a third synonym. In practice, if your doctor says one, they mean the same thing another doctor might call by a different name.
That said, there’s a small but meaningful distinction that’s worth understanding. While CAD specifically describes plaque buildup in the coronary arteries, ischemic heart disease is technically a slightly broader concept: it covers any situation where the heart isn’t getting enough oxygen. Most of the time that’s caused by CAD, but not always.
What Both Terms Describe
At the core of both CAD and IHD is a mismatch between how much oxygen your heart muscle needs and how much it actually receives. In the vast majority of cases, the culprit is atherosclerosis: a gradual buildup of fatty material (plaque) inside the walls of the coronary arteries. This process starts with deposits of fat-laden cells forming what pathologists call a “fatty streak” beneath the artery lining. Over years or decades, that streak grows into a plaque that narrows the artery and restricts blood flow.
When the narrowing becomes significant enough, your heart can’t get the oxygen it needs during exertion, stress, or sometimes even at rest. That oxygen shortfall is called ischemia, which is where the name “ischemic heart disease” comes from. CAD is naming the cause (diseased coronary arteries), while IHD is naming the result (a heart starved of oxygen). Since one leads directly to the other in most patients, the terms have become functionally identical.
When Ischemia Happens Without Major Blockages
Here’s where the distinction matters. A condition called INOCA (ischemia with no obstructive coronary arteries) accounts for a notable subset of people who have real ischemia but don’t have significant plaque blockages. In these patients, the problem lies in the tiny blood vessels of the heart (coronary microvascular dysfunction) or in temporary spasms of the larger coronary arteries. Studies suggest that coronary vascular dysfunction explains 59 to 89% of INOCA cases.
INOCA is more common in women than men and can be easy to miss because standard imaging may show open, clear arteries. This is technically a form of ischemic heart disease that doesn’t fit neatly under the CAD label, since there’s no obstructive plaque causing the problem. So while the two terms overlap almost completely, IHD is the slightly larger umbrella.
How It Feels
Whether your doctor calls it CAD or IHD, the most recognizable symptom is angina: chest pain or discomfort often described as squeezing, pressure, heaviness, or a burning sensation. Pain can also radiate to the arms, neck, jaw, shoulder, or back. Other common symptoms include shortness of breath, fatigue, dizziness, nausea, and sweating.
Stable angina is the most common form. It follows a predictable pattern, showing up during physical activity or stress and resolving within about five minutes with rest. Unstable angina is more serious: it strikes unpredictably, occurs at rest, lasts 20 minutes or longer, and doesn’t respond to the usual relief measures. Unstable angina is a medical emergency because it often signals a plaque rupture or a clot forming in a coronary artery.
Women sometimes experience angina differently. Instead of the classic chest pressure, they may feel stabbing chest pain, stomach discomfort, nausea, or pain in the jaw, neck, or back. These less typical presentations can delay recognition and treatment.
Who’s at Risk
Nearly half of adults in the United States have at least one of the three biggest risk factors for coronary heart disease: high blood pressure, high cholesterol, or smoking. Beyond those, physical inactivity, excessive alcohol use, poor sleep quality, chronic stress, and a diet high in saturated fats and refined carbohydrates all contribute to plaque development over time.
Family history plays a significant role. Your risk increases if your father or brother was diagnosed before age 55, or if your mother or sister was diagnosed before age 65. Genetic factors can influence cholesterol levels, blood pressure regulation, and how easily your arteries develop plaque, even when lifestyle habits are reasonable.
How It’s Detected
Doctors use two broad categories of testing, and which one you get depends on whether they’re looking for the plaque itself or the oxygen shortage it causes. Coronary CT angiography (CCTA) is a non-invasive scan that directly visualizes the arteries, showing plaque buildup, narrowing, and even early-stage atherosclerosis that hasn’t yet caused symptoms. It avoids the risks of an invasive catheter procedure like bleeding or vessel injury.
Functional tests, like stress tests (exercise or medication-induced), look for signs that your heart isn’t getting enough blood during increased demand. These tests detect ischemia rather than the anatomy causing it. For patients whose symptoms suggest ischemia but whose arteries look clear on imaging (the INOCA group), specialized invasive testing with functional measurements can pinpoint whether microvascular dysfunction or vasospasm is responsible.
The Global Picture
By any name, this disease is the leading cause of death worldwide. In 2021, there were roughly 247 million people living with ischemic heart disease globally, and it killed an estimated 8.88 million people that year. Those numbers represented an increase of about 15 million prevalent cases and 250,000 additional deaths compared to just two years earlier, driven largely by aging populations and rising rates of metabolic risk factors in lower-income countries.
The scale of the problem is one reason you’ll encounter so many overlapping terms. Cardiologists, epidemiologists, insurance companies, and public health agencies sometimes favor different names for the same disease, which can be confusing when you’re researching your own health. The bottom line: if you see CAD, IHD, or CHD on a medical report or in a conversation with your doctor, they’re all pointing to the same core problem.