QT Interval Derived Measurements in Patients with Cardiac Syndrome X Compared to Coronary Artery Disease

Abstract

Previous studies assessing effect of ischemia on ventricular repolarization are mostly directed toward patients with coronary artery disease (CAD); however, similar reports on cardiac syndrome X (CSX) are scarce. Whether microvascular dysfunction of CSX and ischemia induced by CAD produce comparable effect on ventricular repolarization is unclear and deserve further studies. In the present study, ECG measures of ventricular repolarization were compared between CAD and CSX patients (40 subjects in each group). Following evaluation of sociodemographic characteristics, medical and past medical history, a resting ECG was used to assess measurements of ventricular repolarization in each patient, namely, QT interval (QT), corrected QT interval (QTc), QT dispersion (QTd), corrected QT dispersion (QTcd), adjacent QT dispersion (AdQTd), QT dispersion ratio (QTdR), JT dispersion (JTd), and Corrected JT dispersion (JTcd). Results showed comparable QT intervals and QTd in CAD and CSX patients even after adjustment for the possible variations in gender, age and body mass index of the studied groups. Although JTd was increased in CSX subjects (26.6 ± 7.2 ms) compared with CAD patients (22.7 ± 6.5 ms, p = 0.019), statistical significance disappeared after correcting JT for variations in heart rate. QT and QTc were significantly below 440 ms in CAD as well as CSX patients (p < 0.001). In contrast, maximum QTd, maximum QTcd and AdQTd of CAD and CSX patients were significantly above 440 ms (p < 0.001). The means of JTd and JTcd were significantly above 22 ms and 24 ms respectively (p < 0.001, p = 0.001) in CSX but not CAD patients (p = 0.529, p = 0.281). The present findings clearly demonstrate comparable measures of ventricular repolarization in CAD and CSX patients and consequently an equal risk of cardiac events in both groups.

Coronary microvascular dysfunction, arrythmias, and sudden cardiac death: A literature review

“…Although studies with a direct focus on microvascular dysfunction and sudden cardiac death or ventricular arrhythmias are lacking, a relationship can be inferred from its effect on repolarization parameters. This hypothesis is supported by the finding that patients with CXS and CAD exhibit an increase in QT dispersion (QTd), corrected QT dispersion (QTcd), and adjusted QT dispersion (AdQTd) when compared to reference ranges [ 57 ]. Another study noted a greater QTcd at rest in women with CXS and CAD compared to healthy subjects, and this dispersion was augmented by exercise [ 58 ].…”

Kardiyak Sendrom X’li Hastalarda Spatial QRS-T Acisinin Degerlendirilmesi

“…Yapılan bir çalışmada düzeltilmiş QT süresinin koroner mikrovasküler disfonksiyonu olan hastalarda sağlıklı populasyona göre daha uzun olduğu gösterilmiştir (10). EKG'de repolarizasyon anormalliklerini gösteren bazı parametreler bir başka çalışmada araştırılmış ve sonuç olarak KSX'li hastalarda repolarizasyon anormalliklerinin fazla olabileceği sonucuna varılmıştır (11). Arter yatağındaki küçük damarlarda yetersiz gevşeme veya vazokonstriksiyon yanıtının artması bu hastalarda azalmış kan akımı, iskemi ve anjina pektoris gelişmesine neden olabilir.…”

A T-wave Variation Characteristics Evaluation Algorithm for Ischemic Heart Beats

“…QT dispersion is the differenced value between the heart beat with maximum value of QT and the heart beat with minimum value of QT [11]. The QT dispersion values in patients with vasospastic angina are higher than the QT dispersion values of their normal conditions, and the QT dispersion measurement may predict the risk of arrhythmia during ischemia [12].…”