Stress-induced QTc-interval shortening as an ancillary marker of ischemia in patients with complete left bundle branch block.
BACKGROUND
In patients with left bundle branch block (LBBB), ischemia-induced repolarization changes associated with QTc-interval shortening may be recorded during coronary angioplasty. We aimed to assess whether these repolarization changes may be predictive of severe coronary artery disease in patients with LBBB.


METHODS
Fifty noninfarcted LBBB patients underwent dipyridamole stress test and coronary angiography for chest pain. To localize the site of ischemia, we considered four groups of conventional ECG leads (V1-V2-V3; V4-V5-V6; aVL-I; III-aVF-II), exploring the anteroseptal, lateral, high-lateral, and inferior left ventricular walls. ST-T changes and QTc intervals were estimated at rest and peak stress, lead by lead, in each group of leads and the fractional percentage difference between rest-stress QTc intervals ([DELTA]QTc) was calculated. A [DELTA]QTc greater than -10% was used to define significant QTc-interval shortening. Coronary stenosis of more than 70% and more than 90% were considered 'significant' and 'severe'.


RESULTS
According to dipyridamole stress test response, two groups were identified: group I (35 patients) with dipyridamole-induced ischemia and group II (15 patients) without dipyridamole-induced ischemia. The wall motion score index at peak stress (compared with resting wall motion score index) was significantly higher in group I (1.98 +/- 0.13 vs. 1.28 +/- 0.08, P < 0.0001) than in group II (1.36 +/- 0.18 vs. 1.25 +/- 0.08, P = 0.296). The patients of group I showed a significant QTc-interval shortening ([DELTA]QTc = -16.9 +/- 3.9%), whereas this did not happen in patients of group II ([DELTA]QTc = +8.8 +/- 2.4%, P < 0.0001). The patients of group I also had a more severe stenosis in the vessel related to the stress-induced dyssynergic area (I = 90.5 +/- 9.5 vs. II = 34.3 +/- 31.1%; P < 0.0001).


CONCLUSIONS
In patients with LBBB, stress-induced pseudonormalization pattern, associated with QTc-interval shortening, allows the identification of cardiac areas supplied by severely stenosed coronary arteries.
Scalise
Filippo
F
Cardiology Department, Ospedale di Vimercate, Vimercate, Italy. filippo.scalise@policlinicodimonaza.it
Bertella
Mauro
M
Manfredi
Mariella
M
Auguadro
Carla
C
Nanna
Michele
M
Vanoli
Emilio
E
Ferrari
Alberto
A
Specchia
Giuseppe
G
D000368:Aged; D000787:Angina Pectoris / Q000209:etiology / Q000503:physiopathology; D002037:Bundle-Branch Block / Q000150:complications* / Q000473:pathology / Q000503:physiopathology; D017023:Coronary Angiography; D023921:Coronary Stenosis / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology; D004176:Dipyridamole; D025401:Echocardiography, Stress; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D012720:Severity of Illness Index; D013997:Time Factors; D014665:Vasodilator Agents
D014665:Vasodilator Agents; D004176:Dipyridamole