Abnormal cortical pain processing in patients with cardiac syndrome X

Cardiac syndrome X (SX) is characterised by angina-like chest pain and ST segment depression on the ECG during stress. Our study aimed at investigating whether in patients with cardiac syndrome X the cerebral processing of the nociceptive inputs is impaired and whether this abnormality can play a primary role in generating pain. We observed that the habituation to experimental pain was assessed in 16 SX patients by evaluating the amplitude modification of the scalp potentials to CO2 laser pulses (laser evoked potentials, LEPs) after repetitive stimulation of the right hand and chest. The LEP amplitude habituation in SX patients was compared with that in 13 control subjects (CS). While CS showed a significant habituation of both the LEP amplitude and pain rating, in SX patients neither the LEP amplitude nor the pain rating showed any significant reduction. The lack of habituation to experimental pain observed in SX patients can be due to an abnormal excitability of the cerebral areas involved in pain processing and can be relevant in the pathophysiology of cardiac syndrome X.