Plasma atrial natriuretic factor levels, impaired myocardial contractility and pain intensity in uncomplicated acute myocardial infarction.

To investigate the relationship between plasma atrial natriuretic factor (ANF) levels, impaired myocardial contractility and pain intensity in acute myocardial infarction (AMI) we introduced a procedure estimating the pain component not influenced by the individual emotional reaction to stress, i.e., the original pain sensation. We deduced this pain component during AMI by correcting the personal report of AMI pain, quantified on a VAS, with the emotional reaction of each patient estimated by using a custom-built instrument which applies electrical stimuli of different intensities. Twenty-five patients with uncomplicated AMI were studied. According to plasma ANF levels and AMI pain values reported on the VAS, patients were categorized into 2 groups: pain and no-pain. Plasma ANF levels were significantly lower in pain (35.9 +/- 2.5 pg/ml) than in no-pain patients (70.8 +/- 3.3 pg/ml), whereas the ejection fraction (EF) was significantly higher in pain (49.6 +/- 1.7%) than in no-pain patients (29.3 +/- 1.9%). Within each group, a negative correlation was found between ANF and EF; the corresponding regression lines did not differ significantly in their slopes or intercepts, suggesting that AMI pain does not affect ANF release. The significant negative correlation between original pain sensation and EF found in pain patients indicates that this pain component may be useful to gauge the severity of impaired myocardial contractility during AMI. Moreover, the much higher plasma ANF levels observed in no-pain patients suggest that ANF may be involved in preventing AMI pain.