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Left bundle branch block disturbs left anterior descending coronary artery flow: study using transthoracic Doppler
Ho-Joong Youn1, Chul-Soo Park, Eun-Joo Cho
1Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea. younhj@catholi.ac.kr
Insights
Left bundle branch block (LBBB) significantly reduces left anterior descending coronary artery (LAD) diastolic flow duration, impacting coronary perfusion. Systolic dysfunction exacerbates this effect, warranting further investigation into the causal relationship.
Area of Science:
- Cardiology
- Cardiovascular Physiology
Background:
- Left bundle branch block (LBBB) is a common cardiac condition.
- Its impact on coronary artery flow, particularly the left anterior descending (LAD) artery, requires detailed evaluation.
Purpose of the Study:
- To assess the influence of LBBB on LAD coronary artery flow.
- To compare LAD flow in LBBB patients with right ventricular (RV) pacing and control groups.
Main Methods:
- Eighty-nine subjects were divided into LBBB, RV pacing, and control groups.
- Transthoracic Doppler echocardiography (TTE) measured coronary flow velocity and diastolic flow duration (%DD) in the LAD.
- Electrocardiography (ECG) assessed QRS duration, and LVEF, LVEDV, LVESV were measured.
Main Results:
- The %DD of the LAD was significantly shorter in the LBBB group compared to RV pacing and control groups, irrespective of LVEF.
- In the LBBB group, %DD positively correlated with LVEF and negatively with LVEDV and QRS duration.
Conclusions:
- LBBB itself impairs LAD coronary perfusion by reducing diastolic flow duration, unlike RV pacing.
- Systolic dysfunction amplifies the negative impact of LBBB on diastolic flow duration.
Background:
This study was performed to evaluate the influence of left bundle branch block (LBBB) on left anterior descending coronary artery (LAD) flow.
Methods:
We divided 89 subjects (34 males and 55 females, mean age 64 +/- 14 years) into an LBBB group (n = 40), a right ventricular (RV) pacing group (n = 26), and a control group (n = 23). All of the patients were examined with surface electrocardiography (ECG) and underwent transthoracic Doppler echocardiography (TTE) to measure QRS duration on the ECG, left ventricular ejection fraction (LVEF), left ventricular end-diastolic volume (LVEDV), and left ventricular end-systolic volume (LVESV). Coronary flow velocity was measured in the distal LAD with TTE, and the percentage of diastolic flow duration (%DD) was expressed as the percentage of diastolic duration of coronary artery flow divided by the R-R interval.
Results:
The %DD of the LAD was significantly shorter in the LBBB group (40.4% +/- 12.4%) with LVEF < 50% than in the RV pacing group (60.3% +/- 7.3%) and the control group (59.3% +/- 7.6%) (P < .01 vs the control and RV pacing groups), and it was also significantly shorter in the LBBB group (49.3% +/- 10.5%) with LVEF > or = 50% than in the control and RV pacing groups (P < .01 vs the control and RV pacing groups). In the LBBB group, the %DD of the LAD had a positive correlation with LVEF (P < .05; r = .50), a negative correlation with LVEDV (P < .05; r = -.57), and a negative correlation with QRS duration (P < .05; r = -.41).
Conclusions:
Unlike RV pacing, LBBB itself can disturb the coronary perfusion of the LAD through shortening of the diastolic flow duration. Furthermore, systolic dysfunction potentiates the shortening effect of diastolic flow duration by LBBB. Whether left ventricular systolic dysfunction is the result of the coronary flow disturbance by LBBB or vice versa merits further investigation.
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