QT INTERVAL AND QT DISPERSION IN SYSTEMIC-SCLEROSIS (SCLERODERMA)

Objectives, To measure QT interval and QT dispersion, and to evaluate possible relationships between these measurements, heart rate variabil ity parameters, and early myocardial involvement in patients with syst emic sclerosis (SSc). Design. Prospective study. Setting. Tertiary car e centre, University 'La Sapienza', Rome, Italy. Subjects. Thirty-eigh t patients with SSc (35 females and three males, mean age 47 +/- 11 ye ars), 19 patients with the diffuse form of disease and 19 with the lim ited form, and 17 healthy controls (11 females and six males, mean age 43 +/- 10 years) were studied. Interventions. Both patients and contr ol subjects underwent resting 12-lead electrocardiogram and 24-hour Ho lter monitoring. Moreover, resting myocardial scintigraphy with 99 m T c-sestamibi was performed in all SSc patients. Main outcome measures. Bazett's formula was used to obtain rate corrected value of QT interva l (QTc). QT and QTc dispersion were defined as the difference between maximum and minimum QT or QTc interval, respectively. Twenty-four-hour heart rate variability was analysed both in the frequency and in the time domain. Results. Twenty-three SSc patients (60.5%) had myocardial resting perfusion defects (group A) and 15 (39.5%) did not (group B). Maximum QTc interval, QT and QTc dispersion were significantly increa sed in SSc patients compared to the control subjects. No significant d ifferences between group A and group B were observed for all QT measur ements. Furthermore, maximum QTc interval, QT dispersion and QTc dispe rsion were significantly increased in group A patients compared to the control group. Total power, low-frequency, and high-frequency values were significantly lower in all SSc patients, whether in group A or gr oup B, than in control subjects. On the other hand, low-frequency/high -frequency ratio was similar in all groups. Heart rate variability in time domain analysis showed no statistically significant differences b etween groups. Conclusions. Patients with SSc have increased QTc inter val, QT dispersion, and QTc dispersion. The role of autonomic nervous system and myocardial involvement on ventricular repolarization in pat ients with SSc needs further investigation.