Detection of arrhythmogenic substrates in prior myocardial infarction patients with complete right bundle branch block QRS using wavelet-transformed ECG.
BACKGROUND
It is important to follow up patients surviving acute myocardial infarction (MI), to detect the presence of any life-threatening arrhythmias. Various non-invasive examinations, such as signal-averaged ECG (SAECG), have been reported to predict the fatal ventricular tachycardia (VT); however, these conventional methods have limitations in detecting VT occurring in patients with complete right bundle branch block (CRBBB) QRS. Wavelet transform has been increasingly reported as a superior time-frequency analysis on the surface ECG in detecting abnormal high-frequency components (HFCs), thus suggesting abnormal myocardial conductions; however, it remains unclear whether wavelet-transformed ECG (WTECG) is useful in patients with CRBBB.


OBJECTIVE
The purpose of this study is to assess the predictive value of WTECG for detecting arrhythmogenic substrates in MI patients with CRBBB.


METHODS
Both the WTECG and SAECG were evaluated in 22 subjects with CRBBB, including 10 subjects without cardiovascular diseases (control group), 7 prior MI patients without VT (Non-VT group), and 5 prior MI patients with sustained VT (VT group). A 12-lead ECG (10 kHz sampling) was recorded and the representative QRS complex (300 ms) was transformed at a frequency range of 40-280 Hz using the Gabor function as the analyzing wavelet. In the power curve along a time course, the percentages of the peak power values at each frequency (60, 80, 120, 150, and 200 Hz) in the corresponding power values at 40 Hz (P60/40, P80/40, P120/40, P150/40, and P200/40, respectively) were calculated. 'The power percentages (P120/40, P150/40, or P200/40) > or =50%' was defined as an abnormal HFC (AHFC), and the number of the leads in which an AHFC was detected (NL-AHFC) of 8 leads (I, aV(F), V1-V6) was counted for comparison of the two MI groups.


RESULTS
There was no significant difference among the three groups in the SAECG recording. The power percentages of HFCs (P120/40, P150/40, and P200/40) in Non-VT group were significantly higher than those in control group (48.2 +/- 36.5 vs. 30.6 +/- 7.7, P<0.001; 47.8 +/- 35.5 vs. 26.9 +/- 7.1, P<0.001; 47.3 +/- 39.4 vs. 24.9 +/- 7.6, P<0.001; respectively). NL-AHFC (P150/40) in VT group significantly increased more than in Non-VT group (3.2 +/- 0.4 vs. 1.4 +/- 0.8, P=0.001). When 'NL-AHFC (P150/40) > or =3' was defined as abnormal, the sensitivity, specificity, positive and negative predictive values for detection of VT in MI patients with CRBBB was 100, 85.7, 83.3, and 100%, respectively.


CONCLUSIONS
WTECG might be a novel non-invasive method to detect arrhythmogenic substrates in MI patients with CRBBB.
Murata
Hiroshige
H
Division of Cardiology, Hepatology, Geriatrics, and Integrated Medicine, Department of Internal Medicine, Graduate School of Medicine, Nippon Medical School. s7086@nms.ac.jp
Ohara
Toshihiko
T
Kobayashi
Yoshinori
Y
Miyauchi
Yasushi
Y
Katoh
Takao
T
Mizuno
Kyoichi
K
D000328:Adult; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000209:etiology*; D002037:Bundle-Branch Block / Q000150:complications* / Q000503:physiopathology; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications* / Q000503:physiopathology