Wong et al identified a prolonged QTc as a risk factor for cardiac death in patients with a history of stroke. Patients with a prolonged QTc may benefit from closer monitoring and more specific diagnostic testing. The authors are from the University of Dundee.
NOTE: As indicated in the next section, prolongation of the QTc may be seen in subarachnoid hemorrhage.
Time from stroke: median time was 12 months between stroke and first evaluation
Exclusions because of difficulty measuring QTc: atrial fibrillation, atrial flutter, bigeminy, paced rhythm, bundle branch block.
|
|
maximum QTc in 12 lead ECG |
|
Cutoff for QTc in ms |
Sensitivity |
Specificity |
|
>= 400 ms |
100% |
6% |
|
>= 410 ms |
100% |
19% |
|
>= 420 ms |
100% |
31% |
|
>= 430 ms |
90% |
40% |
|
>= 480 ms |
35% |
82% |
from Table 3, page 379
|
|
QTc in Lead V6 |
|
Cutoff for QTc in ms |
Sensitivity |
Specificity |
|
>= 400 ms |
100% |
23% |
|
>= 410 ms |
85% |
39% |
|
>= 420 ms |
70% |
53% |
|
>= 430 ms |
65% |
64% |
|
>= 480 ms |
10% |
94% |
from Table 3, page 379
|
|
QTc in Lead III |
|
Cutoff for QTc in ms |
Sensitivity |
Specificity |
|
>= 400 ms |
75% |
47% |
|
>= 410 ms |
65% |
62% |
|
>= 420 ms |
55% |
73% |
|
>= 430 ms |
45% |
86% |
|
>= 480 ms |
5% |
98% |
from Table 3, page 379
Interpretation:
• A QTc >= 430 ms for any of the 3 measures above gave the maximum Youden index.
Limitations:
• The threshold used to define a prolonged QTc in Table 1 is not stated (at least I could not locate it). The leads with significant p values were II, III, aVL, V4, V6 and max QTc.
• The sensitivity and specificity for the different cut-off points indicate a significant numbers of either false positives and/or false negatives. The cutoff of >= 480 ms for V6 mentioned in the abstract only has a sensitivity of 10% despite a respectable specificity of 94%.
• The areas under the ROC curves for max QTc, QTc in V6 and QTc in lead III was about 0.70, which is not terribly good.
• The authors appear to have used the test to identify patients who may benefit from more definitive tests.
Specialty: Cardiology, Neurology
ICD-10: ,
