The ex-Top Gear presenter said he “ignored these things” and later got “pins and needles in my left arm”.
He was taken to John Radcliffe Hospital in Oxford, where a heart attack was ruled out after he had underwent checks, which included an electrocardiogram (ECG), blood tests, and X-rays.
“It seems that of the arteries feeding my heart with nourishing blood, one was completely blocked and the second of three was heading that way,” he said.
Clarkson said he had a stent fitted, which is a tube that is inserted into a narrowed or blocked artery to open it and allow blood to flow more freely.
“The next morning I went home, and here I am, two hours later, writing this and sort of thinking, ‘Crikey, that was close’,” he said.
“Now, thanks to all those tremendous people at the John Radcliffe in Oxford and all of their extraordinary machines, here I am wondering what water tastes like and if it’s possible to make celery interesting.”
Clarkson had previously revealed he had to quit smoking after contracting pneumonia while on holiday in Spain.
He left the TV programme The Grand Tour in September alongside TV show host Richard Hammond and TV presenter James May.