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Impact of Intraventricular Blocks on Cardiac Cycle Dynamics: An Echocardiographic and Vectorcardiographic Analysis
Carlos Eduardo Duarte1, Katia Regina Silva1, Luciene Dias de Jesus2
1Instituto do Coração do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP - Brasil.
Insights
Intraventricular blocks (IVB) alter cardiac mechanics. Left bundle branch block (LBBB) and right bundle branch block with left anterior fascicular block (RBBB+LAFB) significantly impact the left ventricular cycle, highlighting their complexity.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Mechanics
Background:
- Left bundle branch block (LBBB) is known to alter ventricular cycle mechanics.
- The impact of other intraventricular blocks (IVB) on cardiac function is less understood.
Purpose of the Study:
- To investigate cardiac cycle phases and ventricular synchrony across various ventricular activation patterns.
- To compare the electromechanical effects of different intraventricular blocks.
Main Methods:
- A cross-sectional study involving 328 individuals without structural heart disease or ECG abnormalities.
- Simultaneous echocardiography and vectorcardiography were used to analyze cardiac electromechanics.
- Statistical analysis included one-way ANOVA with Bonferroni's test (significance level of 5%).
Main Results:
- Participants' mean age was 64.8±15.3 years; 57.9% were male.
- ECG findings included normal (32.3%), RBBB (18.6%), LAFB (17.7%), RBBB+LAFB (15.6%), and LBBB (15.9%).
- LBBB and RBBB+LAFB showed significantly increased left ventricular pre-ejection time. All IVBs exhibited post-systolic myocardial contraction; LBBB showed ventricular dyssynchrony. Vectorcardiography revealed significant delays in initial and final R wave activation across different IVBs, particularly LBBB and RBBB+LAFB.
Conclusions:
- All investigated intraventricular blocks modify the cardiac cycle.
- Left bundle branch block (LBBB) and combined right bundle branch block with left anterior fascicular block (RBBB+LAFB) significantly alter the left ventricular cycle.
- These findings underscore the complex electromechanical disturbances associated with LBBB and RBBB+LAFB.
Background:
Left bundle branch block (LBBB) causes delays that alter the mechanics of the ventricular cycle. The effect of other intraventricular blocks (IVB) remains little explored.
Objectives:
To study the phases of the cardiac cycle (CC) and ventricular synchrony in different ventricular activation patterns.
Methods:
Cross-sectional study with 328 consecutive individuals without structural heart disease, normal electrocardiogram or IVB, conducted in the period between August/2020 and January/2022. Echocardiogram and Vectorcardiogram were performed simultaneously to analyze the electromechanics of the CC. A one-way Analysis of Variance (ANOVA) with Bonferroni's multiple comparison test was used, with a significance level of 5%.
Results:
The age of the participants was 64.8±15.3 years, with 57.9% male and an ejection fraction of 67.0±6.8%. The electrocardiogram was normal for 32.3%, 18.6% had right bundle branch block (RBBB), 17.7% had left anterior fascicular block (LAFB), 15.6% had RBBB+LAFB, and 15.9% had LBBB. The echocardiogram showed an increased left ventricular pre-ejection by 18.7% (p<0.001) and 56.8% (p<0.001) in RBBB+LAFB and LBBB, respectively. There was a post-systolic myocardial contraction in all types of IVB and ventricular dyssynchrony in LBBB. Using the vectorcardiogram, initial activation of the R wave was increased by 17.4% in LAFB (p<0.001), 43.5% in RBBB+LAFB (p<0.001) and 47.4% in LBBB (p<0.001) and delayed final activation by 69.4% in LBBB (p<0.001), 73.6% in RBBB+LAFB (p<0.001) and 95.3% in RBBB (p<0.001).
Conclusion:
All IVBs modified the CC; however, only LBBB and RBBB+LAFB significantly changed the left ventricular cycle, thereby evidencing the greater complexity of these disorders.
