Myocardial infarction with normal coronary angiography compared with severe coronary artery disease without myocardial infarction: the crucial role of smoking.

BACKGROUND: Why do some patients suffer acute myocardial infarction (MI) despite angiographically normal coronary arteries (NL + MI) whereas others enjoy an acute MI-free life despite extensive three-vessel disease (3VD-MI)? The present study contrasts these two groups to identify some differences in the risk profile.

METHODS: In 10,000 patients admitted to the cardiology service, a first MI was confirmed in 2356 patients, of whom 1609 underwent coronary angiography. In 77 patients with MI, coronary angiography was found to be entirely normal (NL + MI, 77/1609, 4.1%). These were contrasted to 123 patients with severe three-vessel coronary disease but no MI (3VD-MI).

RESULTS: Patients with NL + MI were 13 years younger (42 +/- 8.3 vs 55 +/- 10.5, P < 0.05), with 33 patients (43%) under the age 40 years, in contrast to only 9 patients (7.3%) in the 3VD group being this age. Patients with NC + MI were more often current smokers (80.5% vs 29% in the 3VD group; P < 0.01). Patients with 3VD-MI were, on the other hand, more often diabetic (54% vs 9% in the NL + MI group; P < 0.01) and had a higher cholesterol level (5.6 +/- 1.1 vs 4.9 +/- 1.0 Mmol/l, P < 0.01) as well as a higher incidence of chronic stable angina (52% vs 22%; P < 0.01) and heart failure (6% compared with 0% in the NL + MI group). Sixty-one out of 77 (79%) NL + MI patients had a single risk factor, and in 87%, this was smoking alone. Diabetes mellitus was rare and never occurred alone in this group.

CONCLUSION: In patients who suffer MI despite normal coronary angiography, smoking is a major risk factor: In contrast, in patients with extensive coronary artery disease on angiography but no MI, diabetes rather than smoking is the dominant risk factor. The findings of this study support the view that the risk factors for stable and unstable coronary artery disease are different, as reflected by the contrast of the above groups at the extremes of the spectrum. Smoking appears to be a major risk factor for acute MI (even with normal coronary angiography), whereas diabetes is a major risk factor for more severe but more stable coronary artery disease.