Measurement of pain intensity and statistical analysis to evaluate its relationship with atrial natriuretic factor and myocardial contractility in patients with uncomplicated acute myocardial infarction

Abstract

Circulating levels of atrial natriuretic factor (ANF), the education of myocardial contractility (evaluated by ejection fraction, EF) and different pain intensity were assessed in patients with uncomplicated acute myocardial infarction (AMI). We investigated the relationships between ANF, or EF, and pain intensity by identifying appropriate statistical methods and introducing a procedure for pain intensity measurement. Pain in AMI is variable in intensity, often severe and in some instances intolerable, but in over 20% of AMI patients it may be absent. By using plasma ANF concentration and self-report of AMI pain as parameters, we described a statistical method verifying that AMI patients can be categorized into two significantly different groups: pain and no-pain. Pain is a purely personal experience that includes both the original pain sensation (OPS), depending on the intensity of the stimulus, and the individual emotional reaction component (ER). We developed a method to deduce the OPS from the patient's self-report of AMI pain and then devised an instrument which estimates the ER of each patient by applying electrical stimuli of different intensities. The procedure to disclose a significant correlation (not present by using the self-report of AMI pain) between OPS and ANF, or EF in pain patients is described. The inverse correlation found between EF and OPS suggests that the extent of myocardial damage may play a role in AMI pain onset and affect its intensity. However, when ANF concentration exceeds a threshold value, AMI patients reported only an unpleasant sensation; this result indicates that ANF may be involved in preventing AMI pain. The statistical method introduced for the comparison between the regression lines of ANF and EF in pain and no-pain patients showed that the interdependence between ANF and EF is not influenced by pain, confirming that EF is the major trigger for ANF release in AMI.