Background: Typical chest pain and ECG changes suggest the presence of myocardial ischaemia in cardiac syndrome X (SX) patients and resemble the symptoms observed in subjects with atherosclerotic coronary artery disease (CAD).
Aim: To compare the results of exercise treadmill tests (ETT), 24-hour ECG recordings and echocardiography in SX and CAD patients without previous myocardial infarction with the presence of significant lumen stenosis in one (CA1), two (CA2) or three (CA3) coronary arteries.
Methods: Two hundred six patients were included in the study: 43 SX (28 female), 49 CA1 (11 female), 51 CA2 (7 female) and 63 CA3 patients (8 female) all of whom underwent ETT according to the Bruce protocol, 24-hour ECG recordings and echocardiography.
Results: SX patients had median ST-segment depression during ETT comparable to that in CA1 and CA2 patients but significantly less than the CA3 subjects (p=0.024). Median time to ST depression of at least 1 mm, as well as median time of exercise, was significantly longer in SX individuals than in all CAD patients. The post-exercise recovery time of ST-segment changes was significantly longer in SX patients than in the CA1 group (p=0.006), comparable to that in CA2 subjects and shorter than that in CA3 individuals (p=0.003). Both the maximal ST-segment depression and the duration of significant ST-segment depression in Holter ECG recordings were significantly higher in SX patients than in CA1 subjects, were comparable to the values observed in the CA2 group and significantly lower than in CA3 individuals. The heart rate variability parameters (SDNN and pNN50) were significantly higher in SX patients than in CAD subjects. Patients with SX had a significantly thinner interventricular septum and smaller left ventricular end-diastolic cavity dimension than individuals from the CA1, CA2 and CA3 groups. There were no significant differences in the left ventricular ejection fraction or the thickness of the left ventricular posterior wall between SX patients and CAD patients.
Conclusions: Analysis of the ST segment in SX patients suggests the presence of advanced CAD. However, SX patients have better heart rate variability and exercise performance than patients with CAD.