The diagnostic utility of recovery phase QTc during treadmill exercise stress testing in the evaluation of long QT syndrome

Utility of the Exercise Electrocardiogram Testing in Sudden Cardiac Death Risk Stratification

“…21 Exercise testing was also shown to unmask concealed LQTS, particularly concealed LQT1, even in the presence of betablockers that are known to obscure the LQT1 diagnostic profile during the epinephrine QT stress test. 25 These findings by Horner et al were similar to a previous study done by Chattha et al on 60 patients separated into 3 groups: LQT1, LQT2, and a control group consisting of patients with the lowest probability of LQTS as determined by the Schwartz score and absence of LQTS mutations. 26 The QT interval increased as the RR interval increased in a linear manner in all three groups during the recovery phase.…”

Genetic and Clinical Advances in Congenital Long QT Syndrome

“…22 Horner et al reported from exercise testing of 243 patients that paradoxical QTc prolongation during the recovery phase (QTc ≥460 ms) distinguished LQTS, particularly LQT1, and ∆QTc ≥30 ms (QTc 3-min recovery minus the baseline supine QTc) showed a high sensitivity and specificity (83% and 93%, respectively). 23 Importantly, both studies reported that exercise testing showed satisfactory results in distinguishing LQTS cases from innocent ones while on β-blockers, suggesting no need for a β-blocker washout. 22, 23 As another diagnostic method in LQTS, brisk movement from supine to upright has been reported.…”

“…23 Importantly, both studies reported that exercise testing showed satisfactory results in distinguishing LQTS cases from innocent ones while on β-blockers, suggesting no need for a β-blocker washout. 22, 23 As another diagnostic method in LQTS, brisk movement from supine to upright has been reported. 24 In that study, QTc was significantly increased by 89±47 ms in the LQTS group compared with 50±30 ms in the control group during maximal sinus tachycardia induced by standing up.…”

“…22, 23 In 69 relatives of LQT1 and LQT2 probands who showed borderline to normal QTc at rest, Sy et al reported that a 4-min recovery QTc ≥445 ms discriminated LQTS gene carriers from noncarriers, and a 4-min recovery ≥480 ms showed 100% specificity. 22 Horner et al reported from exercise testing of 243 patients that paradoxical QTc prolongation during the recovery phase (QTc ≥460 ms) distinguished LQTS, particularly LQT1, and ∆QTc ≥30 ms (QTc 3-min recovery minus the baseline supine QTc) showed a high sensitivity and specificity (83% and 93%, respectively).…”

QTc Behavior During Exercise and Genetic Testing for the Long-QT Syndrome

“…16 Very recently, Horner et al analyzed 243 subjects (82 LQT1, 55 LQT2, 18 LQT3, and 88 genotyped negative cases regarded as normal) using an exercise stress test and observed that a paradoxical increase in QTc during the recovery phase distinguishes LQTS patients, particularly LQT1, from controls and found that LQT2 patients also lengthen their QTc from the third minute of recovery. 17 Thus, many publications over the years have supported a contributory role of the exercise stress test in the assessment of a potential LQTS patient. So far, however, all previous studies have been limited by the absence of clear and easily applicable criteria validated in more than 1 cohort that could be used by clinical cardiologists without specific expertise in LQTS.…”