1. Volume 8, Issue 11, Pages 1698-1704 (November 2011)
The diagnostic utility of recovery phase QTc during treadmill exercise stress testing in the evaluation of long QT syndrome 
Justin M. Horner, MD, MPH, Melissa M. Horner, MD, Michael J. Ackerman, MD, PhD 
Heart Rhythm 
Volume 8, Issue 11, Pages (November 2011)
DOI: /j.hrthm
Copyright © 2011 Heart Rhythm Society Terms and Conditions

2. Figure 1
Shown are examples of the treadmill stress test profiles ECG tracings for controls (A), concealed LQT1(B), and concealed LQT2 patients (C). Note that in the control patient there is an initial decrease in their QTc at peak exercise with a gradual return to baseline with recovery. In contrast, the concealed LQT1 patient initially lengthens during peak exercise and continues with maladaptive/paradoxical lengthening of QTc during recovering. Finally, the concealed LQT2 patient also displays an initial decrease in QTc at peak exercise; however, the patient continues to increase QTc during recovery beyond baseline. Whereas LQT1 patients show minimal recovery latency, the QTc at 5 minutes of recovery is much greater than the QTc at 1 minute of recovery in patients with LQT2. The end of the T wave in each example is marked with an arrow.
Heart Rhythm 2011 8, DOI: ( /j.hrthm )
Copyright © 2011 Heart Rhythm Society Terms and Conditions

3. Figure 2
Effect of peak exercise on QTc and ΔQTc. A: Shown is the QTc distribution at rest and peak exercise for control, LQT1, LQT2, and LQT3 patients. The boxes represent the interquartile range (25th to 75th percentiles), with the thick black or white line within the box representing the mean, and the bars represent the range of results excluding extreme outliers. B: Their respective peak ΔQTc's, or change from resting QTc, are also displayed. Note that the LQT1 patients' QTc values remained relatively unchanged compared with the observed shortening of the QTc values in the rest of the cohort.
Heart Rhythm 2011 8, DOI: ( /j.hrthm )
Copyright © 2011 Heart Rhythm Society Terms and Conditions

4. Figure 3
Effect of peak exercise on QTc and ΔQTc in concealed LQTS. A: Shown is the QTc distribution at rest and peak exercise for controls with a resting QTc <460 ms, all concealed LQTS patients, and concealed LQT1, concealed LQT2, and concealed LQT3 patients (concealed LQTS equals QTc <460 ms at rest like the controls). The boxes represent the interquartile range (25th to 75th percentiles), with the thick black or white line within the box representing the mean, and the bars represent the range of results excluding extreme outliers. B: Their respective peak ΔQTc's are also displayed. Note that while QTc values for the overall concealed LQTS cohort remained relatively unchanged, the QTc values increased at peak exercise in concealed LQT1 but shortened in concealed LQT2/3.
Heart Rhythm 2011 8, DOI: ( /j.hrthm )
Copyright © 2011 Heart Rhythm Society Terms and Conditions

5. Figure 4
QTc and ΔQTc during the recovery phase. A: Shown is the QTc distribution at rest and at 1, 2, 3, 4, and 5 minutes of recovery for control, LQT1, LQT2, and LQT3 patients. The boxes represent the interquartile range (25th to 75th percentiles), with the thick black or white line within the box representing the mean, and the bars represent the range of results excluding extreme outliers. B: Their respective recovery phase ΔQTc values (QTc recovery minus QTc baseline) are also displayed. Note the significant difference in the recovery QTc values and the ΔQTc values of the LQT1 patients compared with the rest of the cohort.
Heart Rhythm 2011 8, DOI: ( /j.hrthm )
Copyright © 2011 Heart Rhythm Society Terms and Conditions

6. Figure 5
QTc and ΔQTc during the recovery phase in concealed LQTS. A: Shown is the QTc distribution at rest and at 1, 2, 3, 4, and 5 minutes of recovery for controls with a resting QTc <460 ms, all concealed LQTS patients, and concealed LQT2 and concealed LQT3 patients. The boxes represent the interquartile range (25th to 75th percentiles), with the thick black or white line within the box representing the mean, and the bars represent the range of results excluding extreme outliers. B: Their respective peak ΔQTc values are also displayed. Note that the concealed LQT1 patients separate from controls in recovery.
Heart Rhythm 2011 8, DOI: ( /j.hrthm )
Copyright © 2011 Heart Rhythm Society Terms and Conditions

7. Figure 6
Shown is the QTc recovery latency for control, LQT1, LQT2, and LQT3 patients. Here the ΔQTc recovery latency is defined as the QTc at 5 minutes of recovery minus the QTc at 1 minute of recovery. Note the significant difference in the QTc recovery latency for LQT2 and LQT3 patients when compared with controls and LQT1 patients.
Heart Rhythm 2011 8, DOI: ( /j.hrthm )
Copyright © 2011 Heart Rhythm Society Terms and Conditions