How doctors guess your heart attack risk
Recently, I read some news about a man who was scheduled for a hip replacement and ended up getting a 4-vessel heart bypass.
Apparently, a 57-year-old man saw his surgeon days before surgery. Because of a heart murmur, he was referred to cardiologists. After a cascade of tests (starting with a not-routine heart test that measures heart calcium score – more about that later), he ended up getting his heart fixed. He thanked the orthopedic surgeon for saving his life.
Wait, I thought, What happened?
While I don’t have a problem with whom he credited for saving his life, I don’t want you to think you need the threat of impending surgery to shed light on a serious heart condition.
So let’s talk about what we do, including the cardiac artery calcium score (CACS) that started everything.
In developed countries, heart disease kills 1 in 3 people. In primary care, we focus on two things: pick out who might be in trouble – and do something about it early.
To estimate your heart disease and stroke risks, we use an old but well researched formula that includes several simple variables – your sex, age, blood pressure, diabetes, smoking status, and cholesterol levels – and can estimate your chance of having a heart attack/stroke in the next 10 years – decently. It takes a minute to do.
In the low-risk group, we reinforce good lifestyle choices. In the high-risk group, we get aggressive with medications, like aspirin and/or statin, a powerful anti-inflammatory and cholesterol-lowering drug.
But there’s a group of people who fall in the intermediate range. We can use CACS to enhance our risk prediction.
CACS uses a CAT scan (CT) which measures calcium in the heart blood vessels. When blood vessels age they develop plaques (crud) on their walls. Some plaques contain calcium, which makes the vessel walls literally bone-like. The total calcium burden correlates well with the degree of heart disease.
So why don’t we schedule CACS CT on everybody?
First, it’s an indirect measure of the actual blockage.
Last year, my brother’s cholesterol shot up. His doctor ordered a CACS CT. His score came back high, surprising us.
He underwent another CT that looked at each blood vessel. Another surprise: the vessel with the high calcium score had minimal blockage, but the vessel with low calcium score had advanced blockage.
CACS is like a tool that measures the extent of rust on a pipe. The rust reflects troubled pipes but not necessarily the extent of crud inside the pipe.
My brother went on statin and aspirin and a second drug for blood pressure. He still exercises. But he admits every time he’s short of breath, he worries he’s getting angina. His diet changed drastically; there are more greens on his plates.
Another issue with CACS: it may underestimate risk in some people, especially women and young people, and be falsely reassuring. A study showed that up to 30% of heart attacks and strokes have a CACS of 0.
Instead of dwelling on the nuances of CACS, I have two urgent messages. First, heart disease starts early, early as in late teens and early 20s.
Calcium in blood vessels takes decades to develop. By mid 50s, 1 in 3 have positive CACS.
My second message: at any stage of heart disease, many risks are modifiable. Sure you can’t change your age, race, family history or tradition that everybody must wear the same sweater for the Christmas photo, but simple lifestyle changes can significantly drop your risk of heart disease.
On a good note, the missing-his-hip-surgery guy did well after his bypass surgery. In a week, he was "able to walk a mile and a half without stopping.” What’s good for the heart is good for the joints.