But while that number may sound concerning, it marks an improvement over estimates from earlier studies, according to a report in a recent issue of the American Journal of Cardiology.
It is possible, the study authors explain, that greater public awareness of heart attack symptoms and more-sensitive cardiac tests have led to fewer unrecognized heart attacks in recent years.
Although most heart attacks involve chest pain or discomfort, some occur without these symptoms. In addition, milder chest discomfort and other heart attack symptoms such as dizziness or shortness of breath may not readily signal a heart attack to the patient, or even the doctor.
Previous research in the US and elsewhere has suggested that anywhere from 20% to 40% of heart attacks may go undetected. But these estimates are based on patients who had heart attacks prior to the late 1980s, according to the authors of the new report, led by Lori L. Boland of the University of Minnesota in Minneapolis.
Boland's team analyzed data on more than 12,800 men and women who had participated in a national study of cardiovascular health between 1987 and 1998. Participants were between the ages of 45 and 65, and free of coronary artery disease at the study's start. They were followed for 10 years, on average.
The researchers found that, based on periodic electrocardiograms taken as part of the study, 20% of the 500 heart attacks participants suffered went unrecognized. African Americans had a slightly higher percentage of undetected heart attacks than whites did -- 23%, compared with 19%.
Despite the commonness of undetected heart attacks among these patients, Boland and her colleagues point out that the percentage is "slightly lower than previous estimates from other populations."
Although they don't know for sure, the authors note that it's "plausible" that in the 1990s, Americans became more likely to seek medical care for possible heart attack symptoms. In addition, they write, recent advances in detection, such as cardiac enzyme tests, may have allowed doctors to spot more cases of mild heart attack.
American Journal of Cardiology 2002;90:927-931
With so many heart attacks going unnoticed doesn' t it make sense to concentrate and focus on prevention?
Of course it does.
So the most important blood tests would be two HDL ratios.
First of all, please understand that a total cholesterol level is very close to meaningless unless it is above 300. I have seen a number of people over 250 who actually were at low heart disease risk due to their HDL levels. Conversely, I have seen even more who had cholesterol levels under 200 that were at a very high risk of heart disease based on the following additional tests.
HDL percentage is a very potent heart disease risk factor. Just divide your HDL level by your cholesterol. That percentage should be above 24%. You can also do the same thing with your triglycerides and HDL ratio. That percentage should be below 2.
However, while cholesterol levels are typically related to insulin resistance, there are clearly a certain segment of individuals who have a strong overriding component to their cholesterol levels that is unrelated to insulin issues.
A fasting blood sugar level test is the simplest and least expensive. One used to have a blood sugar level greater than 140 to be diagnosed with diabetes. That has now been reduced to 126. Anyone with a level between 110 and 125 is considered pre-diabetic. Earlier this year, however, the Cleveland Clinic Foundation announced they use a fasting blood sugar of 90 mg/dl or higher as a biomarker of coronary heart disease risk.
Fasting Insulin level should be below 10 for certain, but an better level is below 5 and ideal level is below 2.
Homocysteine levels should be below 8 (Am J Clin Nutr. 2003 Jan;77(1):63-70)
Lipoprotein a [Lp (a)]: Acceptable levels per dl of blood would be <10 mg. 11-24 md/dl are borderline high; >25 are very high. If your Lp (a) levels are over 10, you need to take action at once.
Nearly five years ago I posted information from a JAMA article that is relevant today. The following are four additional blood tests that have been reported to help determine your risk for a hear attack.
1. An elevated C-reactive Protein (CRP) was a risk. CRP is elevated when there is inflammation going on somewhere in the body.
2. An increased white blood cell count (WBC) was also a risk. A WBC count greater than 8.5 was found to be the cutoff.
3. Decreased albumin levels were also a factor that could indicate a relative protein deficiency and excess of carbohydrates.
4. Elevated fibrinogen levels, which indicates an increased tendency towards clotting.