Over the past several decades, scientists have developed a good grasp of how atherosclerosis — the narrowing of coronary arteries — progresses.

But until recently, we were at a loss to explain what initiates this deadly process in the first place.

However, the answer is becoming more clear. The culprit is inflammation.

There are two kinds of inflammation: acute and chronic.

Acute inflammation, occurs, for instance, when you cut your finger. Your immune system then goes into action, and within a few days the reddening and swelling has healed. That is a normal, healthy inflammatory response.

But chronic inflammation is different. It festers within your body, and sets the stage for many serious ailments — including heart disease — even though you can’t see it.

Repeated exposure to toxins produced by tobacco smoke, along with stress and belly fat causes this type of inflammation, which mistakenly signals your immune system to produce a response that narrows coronary arteries and makes blood clots more likely.

If plaque ruptures, it can cause a heart attack.