Four out of 10 MIs unrecognized in large, population-based study

Shelley Wood

February 15, 2006

Rotterdam, the Netherlands - Researchers performing baseline and follow-up ECGs in subjects 55 years of age and older found that 43% of the time, MIs were clinically unrecognized [1]. The analysis, conducted in 5148 participants in the population-based Rotterdam Study, implies that patients and physicians are not doing a good job of recognizing MI symptoms.

Since previous MI is a major predictor of future cardiovascular events, recognizing MI when it occurs could reduce the risk of future fatal and nonfatal cardiac events, Dr Anneke de Torbal et al (Erasmus Medical Center, the Netherlands) write in a paper published online February 14, 2006 in the European Heart Journal.

In an interview with heart wire , study coauthor Dr Eric Boersma explained that while unrecognized MI is a well-documented phenomenon, most of the epidemiological studies of unrecognized MI were conducted before the 1990s and looked predominantly at younger adults or at people with established heart disease. These studies, he added, have suggested that 4% to 43% of MIs go unrecognized. "Therefore, we were not too surprised to learn that this number was 43% in our study population. On the other hand, 43% clearly is in the upper end of what has been reported so far," he commented.

Unrecognized MI

De Torbal, Boersma, and colleagues examined baseline ECGs conducted between 1990 and 1993 with follow-up ECGs conducted during 1994-95 and 1997-2000. In the 4187 subjects who had at least one follow-up ECG, clinically recognized MIs occurred in 141 subjects over a mean of 6.4 years, yielding a rate of five per 1000 person-years. Follow-up ECGs, however, analyzed using the automated Modular ECG Analysis System (MEANS), pointed to evidence of 328 unrecognized cases, of which 89 were confirmed after expert review, yielding a rate of 3.8 per 1000 patient-years.

The authors also note that the incidence of recognized MI was higher in men than in women (8.4 vs 3.1 per 1000 person-years), while the rate of unrecognized MI (relative to total MI incidence) was higher in women than in men (54% vs 33%).

"Our research did not focus on the question 'why,' but on 'how often,' " Boersma pointed out, adding that to answer the 'why' question, investigators would need to know what kind of symptoms people had felt at the time of the unrecognized infarction—data not collected in the study. Still, he said, "evidence exists that women more often have myocardial infarctions without typical symptoms, such as severe chest pain, shortness of breath, etc, than men," which might explain why more MIs were not initially diagnosed in women.

 
The main problem is that in quite a number of cases, patients do not recognize that their symptoms are related to a problem with their heart.
 

The authors propose that periodic ECG screening may be warranted in people over 55, as a readily available, easily obtained test for identifying people at higher risk for future cardiac events.

"In most countries in the Western world, there are programs for primary and secondary prevention of cardiovascular diseases," Boersma told heart wire . "That is, the medical community pays attention to diabetes, hypertension, hyperlipidemia, overweight, smoking, etc. We believe that the ECG might be integrated in these prevention programs, and repeat ECGs might particularly be considered in subjects at high risk of cardiovascular diseases."

While other screening tools exist, more comprehensive screening is not the central issue, he emphasized. "We believe that the main problem is that in quite a number of cases, patients do not recognize that their symptoms are related to a problem with their hearts. Consequently, they do not seek medical help, and as a second consequence they are not diagnosed as having myocardial infarction. So, in our view, the primary concern is not the diagnostic tool, but the patient."

One thing that is not clear, Boersma noted, is whether the general public, in 2006, is better informed and more likely to recognize and respond to symptoms than people during the 1990s, when de Torbal et al's study was conducted.

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