Role of interactions between psychological and clinical factors in determining 6-month mortality among patients with acute myocardial infarction. Application of recursive partitioning techniques to the GISSI-2 database. Gruppo Italiano per lo Studio della Sopravvivenza nell' Infarto Miocardico.
BACKGROUND
Clinical and epidemiological studies support the hypothesis that ischaemic cardiovascular diseases are consistently associated with psychological, social and behavioural factors. Nevertheless, the joint effect of clinical characteristics and psychological variables in determining the prognosis of acute myocardial infarction survivors has been seldom investigated.


RESULTS
In the framework of the GISSI-2 trial, the impact of psychological factors on 6-month mortality and their interaction with clinical features was included as an ad hoc research project. Overall, 2449 patients were evaluated, 63 of whom died during the study period. All patients undertook a self-administered questionnaire (Cognitive Behavioural Assessment Hospital Form), investigating 16 psychological dimensions relative to three areas (state variables, vital exhaustion, trait variables). The impact of psychological variables on prognosis and their interaction with clinical variables were investigated by using a tree-growing technique (RECursive Partitioning and AMalgamation-RECPAM) applied to survival analysis. This statistical method allowed the identification of three separate classes, characterized by different prognoses: Class I (presence of vital exhaustion), Class II (concomitance of no vital exhaustion, depression and low levels of anxiety) and Class III (all other patients). After adjusting for the clinical variables, Class I was associated with an intermediate prognosis (hazard ratio [HR] = 2.2; 95% confidence intervals [CI], 1.2-4.0) and Class II to the worst (HR = 3.2; 95% CI = 1.6-6.2), as compared to Class III. High levels of neuroticism and extroversion were associated with a better prognosis. When clinical and psychological variables were simultaneously investigated by RECPAM, Type A behaviour was shown to be an important risk predictor among patients with better clinical conditions, i.e. those eligible for exercise test (HR = 2.6, 95% CI = 1.2-5.5). Finally, a striking difference in the impact of the most predictive clinical variables (exercise test ineligibility, late and early ventricular failure) was found among patients with and without vital exhaustion.


CONCLUSIONS
This study shows that acute myocardial infarction survivors are heterogeneous with respect to 6-month mortality according to their psychological profile. More important, the impact of these variables appears comparable to that of very well known clinical risk predictors. The availability of a large study population, together with the use of innovative statistical techniques, allowed us to identify subgroups of patients for whom the joint action of clinical and psychological characteristics has been clearly documented. This suggests the need for incorporating psychological evaluation in the care of acute myocardial infarction patients.
Carinci
F
F
Department of Clinical Pharmacology and Epidemiology, Consorzio Mario Negri Sud, Veruno (Novara), Italy.
Nicolucci
A
A
Ciampi
A
A
Labbrozzi
D
D
Bettinardi
O
O
Zotti
A M
AM
Tognoni
G
G
D015331:Cohort Studies; D004562:Electrocardiography / Q000706:statistics & numerical data; D005500:Follow-Up Studies; D006333:Heart Failure / Q000175:diagnosis / Q000401:mortality / Q000523:psychology; D006801:Humans; D009203:Myocardial Infarction / Q000175:diagnosis / Q000401:mortality* / Q000523:psychology; D010555:Personality Inventory / Q000706:statistics & numerical data; D011237:Predictive Value of Tests; D011594:Psychometrics; D015203:Reproducibility of Results; D012803:Sick Role; D015996:Survival Rate