| Autor: |
WU, DING-KWO, BISSETT, JOE K, WATSON, JOHN I, BAKER, JOHN |
| Zdroj: |
Cardiovascular Research; Jan1984, Vol. 18 Issue 1, p60-65, 6p |
| Abstrakt: |
Patients with congenital QT prolongation have an increased incidence of ventricular arrhythmias and sudden death. Altered sympathetic tone has been suggested as an important contributing factor in this syndrome. Although some patients with an increased QT interval and arrhythmias have an abnormal QT response during exercise, the effect of exercise has not been reported in patients with acquired QT prolongation without clinical manifestations. The purpose of this study was to determine the pattern of QT change with exercise in patients with QT prolongation without exercise-induced arrhythmias in order to: 1) determine the most frequent response in this group; 2) observe the effect of posture on QT changes; and 3) compare the rate of QT change with a control group. Treadmill exercise testing was performed in 10 patients (mean age 52.1 ±8.0 years) with a QTc greater than 0.44 s; the results were compared with 14 patients with a normal QTc (mean age 45.8±12.1 years).Patients with an increased QT interval at rest experienced a significant reduction in QT interval during exercise (0.315±0.030 s vs 0.394±0.046 s standing at rest; P<0.01), as cycle length was decreased from 0.732±0.175 s to 0.489±0.062 s. Patients in the control group had a similar change in QT interval (0.297±0.015 s vs 0.359±0.029 s standing at rest (P<0.01), with a comparable change in cycle length 0.733±0.097 s vs 0.511 ±0.059 s. The slope of QT interval versus R-R interval was not significantly different (0.295±0.109 vs 0.259±0.100 s). Changes in QT and R-R intervals between supine and standing positions were similar in both groups.The results demonstrate that patients with QT prolongation without exercise-induced arrhythmias have a significant decrease in QT interval during upright exercise. The change in QT interval is not significantly different from that observed in a control group with normal QT measurements when similar changes in heart rate are produced by treadmill exercise. The results suggest that repolarisation abnormalities in this group respond in a normal manner to changes in autonomic tone produced by upright posture and treadmill exercise. [ABSTRACT FROM PUBLISHER] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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