Long QT Syndrome other diagnostic studies: Difference between revisions
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==Exercise Treadmill Testing== | ==Exercise Treadmill Testing== | ||
Similar to catecholamine provocation testing, an exercise treadmill test with EKG, can unmmask concealed long QT syndrome. This is also used as a provocation test for persons who have history and symptoms, or a family history suggestive of long QT syndrome, but do not have any abnormalities on resting EKG. | Similar to catecholamine provocation testing, an exercise treadmill test with EKG, can unmmask concealed long QT syndrome. This is also used as a provocation test for persons who have history and symptoms, or a family history suggestive of long QT syndrome, but do not have any abnormalities on resting EKG. Studies have shown not only the usefulness of exercise stress testing in the diagnosis of long QT syndrome, but also it's utility in determining the subtype of long QT syndrome that the patient has. Krahn et al. showed that the hysteresis of the QT segment observed during exercise may be helpful in the diagnosis of long QT syndrome. They also showed that differences in teh QT interval that were greater than 21ms between 1 min into recovery and early exercise may be indicative of long QT syndrome. A study done by Takenaka et al. demonstrated that the QTc in LQT1 patients was significantly prolonged during exercise, whereas in LQT2 patients, exercise did not cause any significant changes in the QTc, however did show a prominent notch on the descending limb of the T wave. They also showed that there is a steeper QT/R-R slope in LQT2 patients than in LQT1 patients during exercise. | ||
The analysis of QT during exercise for diagnostic purposes was pursued earlier by other researchers. Krahn et al. (9) showed that QT hysteresis observed during exercise testing may be helpful in the diagnosis of LQTS patients. They described that a difference in QT >21 ms between 1 min into recovery and early exercise measured using matched heart rates may be indicative of LQTS. Takenaka et al. (10) showed that QTc was significantly prolonged during exercise in LQT1 patients, whereas in LQT2 patients, exercise produced a prominent notch on the descending limb of the T-wave, with no significant changes in the QTc. They demonstrated that LQT2 patients have a steeper QT/R-R slope than LQT1 patients during exercis | |||
==References== | ==References== | ||
Revision as of 16:04, 7 October 2012
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Overview
The diagnosis of long QT syndrome can be difficult when abnormalities on electrocardiogram are borderline or intermittent. In cases where the history and symptoms are suggestive of long QT syndrome, but few or no abnormalities are seen on electrocardiogram, further testing can be done to unmask long QT syndrome with the use of exercise treadmill testing, and catecholamine provocation testing.
Non-exercise Catecholamine Stress Testing
During this type of test, an EKG is performed while the patient is given an infusion of epinephrine. This test can unmask what is known as concealed long QT syndrome, which shows a normal QT interval on EKG at rest. This test will usually show a prolonged QT interval in persons who have a history of fainting spells in response to intense exercise or emotional upset.
Exercise Treadmill Testing
Similar to catecholamine provocation testing, an exercise treadmill test with EKG, can unmmask concealed long QT syndrome. This is also used as a provocation test for persons who have history and symptoms, or a family history suggestive of long QT syndrome, but do not have any abnormalities on resting EKG. Studies have shown not only the usefulness of exercise stress testing in the diagnosis of long QT syndrome, but also it's utility in determining the subtype of long QT syndrome that the patient has. Krahn et al. showed that the hysteresis of the QT segment observed during exercise may be helpful in the diagnosis of long QT syndrome. They also showed that differences in teh QT interval that were greater than 21ms between 1 min into recovery and early exercise may be indicative of long QT syndrome. A study done by Takenaka et al. demonstrated that the QTc in LQT1 patients was significantly prolonged during exercise, whereas in LQT2 patients, exercise did not cause any significant changes in the QTc, however did show a prominent notch on the descending limb of the T wave. They also showed that there is a steeper QT/R-R slope in LQT2 patients than in LQT1 patients during exercise.
The analysis of QT during exercise for diagnostic purposes was pursued earlier by other researchers. Krahn et al. (9) showed that QT hysteresis observed during exercise testing may be helpful in the diagnosis of LQTS patients. They described that a difference in QT >21 ms between 1 min into recovery and early exercise measured using matched heart rates may be indicative of LQTS. Takenaka et al. (10) showed that QTc was significantly prolonged during exercise in LQT1 patients, whereas in LQT2 patients, exercise produced a prominent notch on the descending limb of the T-wave, with no significant changes in the QTc. They demonstrated that LQT2 patients have a steeper QT/R-R slope than LQT1 patients during exercis