Clinical and epidemiological characteristics of juvenile myocardial infarction in Italy: The GISSI experience

BACKGROUND. No clinical and epidemiological data are available about acute myocardial infarction (AMI) at a young age in large populations, due to the low prevalence of AMI in younger people. The aim of the present study is to analyze epidemiological and clinical characteristics of AMI among younger people in Italy, using the data bases of the three GISSI studies. METHODS. Analysis of epidemiological and clinical characteristics of AMI according to different age groups in the three GISSI studies that collected data from 1985 to 1993. RESULTS. In the GISSI-2 and GISSI-3 data bases, the prevalence of AMI at a young age (2 and 1.8% respectively; difference -0.2% with 95% CI from -0.4 to 0.3%), hospital mortality (2.3 and 1.9% respectively; difference -0.4% with 95% CI from -1.9 to 1.0%), and the rate of young female patients (8 and 7% respectively; difference -1% with 95% CI from -3.6 to 1.6%) are similar. In the GISSI-2 study, we observed that in comparison to elderly patients (> 70 years), young patients (<40 years) are more frequently smokers (83.9 vs 21.0%; difference 62.9% with 95% CI from 58.5 to 67.3%) and have a higher rate of family history for CAD (42.1 vs 21.1%; difference 21.0% with 95% CI from 15.3 to 26.7%) and of hypercholesterolemia (28.3 vs 15.0%; difference 13.3% with 95% CI from 18.5 to 80.8%), but show a lower prevalence of hypertension (12.2 vs 44.3%; difference from -32.1% with 95% CI from - 28.0 to -36.2%) and diabetes (2.9 vs 18.8%; difference -15.9% with 95% CI from -13.5 to -18.3%). AMI at a young age is generally the first event in ischemic heart disease; in comparison with older patients with previous AMI (6.4 vs 17.4%; difference -11.0% with 95% CI from -7.8 to -14.0%) and history of angina (23.2 vs 40.0%, difference -16.8% with 95% CI from -11.8 to - 21.9%) this is less frequent. The rate of complications is lower in younger as opposed to older patients for both early (7.7 vs 31.2%; difference -23.5% with 95% CI from -20.0 to -26.9%) and late heart failure (2.9 vs 18.5%; difference -15.6% with 95% CI from -13.2 to -18.0%), as well as for angina (6.4 vs 10.5%; difference -4.1% with 95% CI from -1.1 to -7.1%), reinfarction (1.0 vs 3.3%; difference -2.3% with 95% CI from -1.1 to -3.6%) and complete AV block (1.6 vs 6.6%; difference -5.0% with 95% CI from -3.3 to -6.7%). In young patients, we observed lower in-hospital (1.6 vs 21.1%; difference - 19.5% with 95% CI from -17.4 to -21.6%) and six-month mortality (1.3 vs 8.1%; difference -6.8% with 95% CI from -5.0 to -8.5%). CONCLUSIONS. The incidence and mortality of AMI at a young age was steady during the period between 1988 and 1993. AMI at a young age is a clinical entity with specific characteristics that differ from those found in old patients. In addition, it has a peculiar risk profile with a better short- and medium-term outcome.