Pediatric Left Bundle Branch Block Clinical Presentation
- Author: Bahram Kakavand, MD, FACC; Chief Editor: Stuart Berger, MD more...
Important points to cover when one obtains a history from a child with left bundle branch block (LBBB) include known congenital heart disease, previous cardiac surgery, or both. Questions regarding fatigue, exercise intolerance, presyncope, and syncope may further indicate the clinical significance of the left bundle branch block.
Upon physical examination, auscultatory findings in patients with left bundle branch block include an absent or diminished first heart sound and reversed splitting of the second heart sound. That is, the second heart sound is split in expiration and single in inspiration.
Left bundle branch block
Left bundle branch block is not a benign entity; risk factors include the following:
- Left bundle branch block is associated with anatomic malformations and abnormalities of the conduction system (eg, as is observed in Lenegre disease).
- Left bundle branch block has been observed after surgery in the left ventricular outflow tract, septal myectomy, alcohol septal ablation, replacement of the aortic valve, and transcatheter closure of perimembranous ventricular septal defects.
- Left bundle branch block is also observed in patients with left ventricular hypertrophy, left ventricular noncompaction and neuromuscular disease, progressive conduction system disease, myocarditis, cardiomyopathy, hemochromatosis, sclerodegenerative diseases, myocardial infarction, aortic valve endocarditis, rheumatic fever with aortic valve involvement, perinatal exposure to HIV type 1, Wolff-Parkinson-White Syndrome (when the abnormal conduction pathway enters the right ventricle), and acute pulmonary embolism. (See also Supraventricular Tachycardia, Wolff-Parkinson-White Syndrome.)
- The left bundle branch block pattern, or rather, left ventricular conduction delay, also occurs in patients with Wolff-Parkinson-White Syndrome in whom the abnormal conduction pathway enters the right ventricle.
- Some patients may demonstrate a left bundle branch block pattern during supraventricular tachycardia (ie, rate-dependent bundle branch block).
Left anterior hemiblock
Risk factors for left anterior hemiblock (LAH) include the following:
- LAH has been associated with coronary artery disease, left ventricular hypertrophy, cardiomyopathy, tetralogy of Fallot repair, ventricular septal defect repair, septal myectomy, subvalvar aortic resection, and an anomalous origin of the left coronary artery from the pulmonary artery.
- LAH may be present in patients with autosomal dominant bundle branch disease and has been associated with lentiginosis.
- Among congenital heart defects, LAH is characteristic of endocardial cushion defects, such as ostium primum atrial septal defect complex and complete AV canal, an abnormality frequently seen in patients with Down syndrome. LAH occurs in endocardial cushion defects because of congenital absence or hypoplasia of the left anterior division. LAH has also been described in Noonan syndrome.
- Patients with endocardial cushion defects (ostium primum atrial septal defect, complete AV canal), tricuspid atresia, double-outlet right ventricle, and certain forms of a functional single ventricle have LAH that may reflect absent, hypoplastic, or abnormally coursing left bundle fascicles rather than an anterior hemiblock per se.
Risk factors for left posterior hemiblock
Left posterior hemiblock is observed after congenital heart surgery and in patients with congenital aortic stenosis, endocarditis, or diphtheritic myocarditis.
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