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[Mechanism of the B-B' step formation in M-mode echocardiography]
T Ishikawa1, K Kimura, H Yoshimura
1Second Department of Internal Medicine, Yokohama City University School of Medicine.
Insights
The B-B' step in mitral valve movement, linked to diastolic mitral regurgitation, is strongly correlated with atrioventricular block and myocardial infarction. Atropine administration significantly shortens this B-B' step duration.
Area of Science:
- Cardiology
- Echocardiography
- Cardiac Electrophysiology
Abstract:
This study analyzed the mechanism involved in the B-B' step formation of the mitral valve movement using pulsed Doppler and color Doppler echocardiography. We examined 24 patients with first degree atrioventricular block (AVB), 26 with old myocardial infarction (OMI), and 34 with a DDD-pacemaker (PM) (16 with complete AV block and 18 with sick sinus syndrome). In 19 of 24 AVB patients, the B-B' step was associated with diastolic mitral regurgitation (DMR). There was a significant positive correlation between the magnitude of the PQ interval and the B-B' step duration (r = 0.94, p less than 0.001). Intravenous administration of 1 mg of atropine shortened the B-B' step duration from 0.15 +/- 0.06 (SD) to 0.05 +/- 0.07 sec (p less than 0.001). Although changes in the PQ interval were well correlated with changes in the B-B' step duration, the P-B-B' step, or PC interval, did not change significantly. In 12 of the 26 OMI patients, the B-B' step and DMR were both observed. The QC intervals of these patients were longer than those of OMI patients without the B-B' step (0.088 +/- 0.03 vs. 0.066 +/- 0.021 sec, p less than 0.05). The P-B-B' step interval was shorter in the OMI patients than in the AVB patients (0.190 +/- 0.029 vs 0.232 +/- 0.033 sec, p less than 0.01). In 28 of 34 patients implanted with a DDD-pacemaker, the B-B' step and DMR were induced by prolonging the AV delay.(ABSTRACT TRUNCATED AT 250 WORDS)