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J Cardiovasc Magn Reson. 2018 Sep 20;20(1):66. doi: 10.1186/s12968-018-0457-8.

Effect of isolated left bundle-branch block on biventricular volumes and ejection fraction: a cardiovascular magnetic resonance assessment.

Author information

1
Department of Medicine, Cardiovascular Division, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA, 02215, USA.
2
The NHLBI's Framingham Heart Study, Framingham, MA, USA.
3
Cardiology Section, Veterans Affairs Healthcare System, Boston, MA, USA.
4
Department of Medicine, Cardiovascular Division, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA, 02215, USA. wmanning@bidmc.harvard.edu.
5
Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA. wmanning@bidmc.harvard.edu.

Abstract

BACKGROUND:

Left bundle branch block (LBBB) is associated with abnormal left ventricular (LV) contraction, and is frequently associated with co-morbid cardiovascular disease, but the effect of an isolated (i.e. in the absence of cardiovascular dissease) LBBB on biventricular volumes and ejection fraction (EF) is not well characterized. The objective of this study was to compare LV and right ventricular (RV) volumes and EF in adults with an isolated LBBB to matched healthy controls and to population-derived normative values, using cardiovascular magnetic resonance (CMR) imaging.

METHODS:

We reviewed our clinical echocardiography database and the Framingham Heart Study Offspring cohort CMR database to identify adults with an isolated LBBB. Age-, sex-, hypertension-status, and body-surface area (BSA)-matched controls were identified from the Offspring cohort. All study subjects were scanned using the same CMR hardware and imaging sequence. Isolated-LBBB cases were compared with matched controls using Wilcoxon paired signed-rank test, and to normative reference values via Z-score.

RESULTS:

Isolated-LBBB subjects (n = 18, 10F) ranged in age from 37 to 82 years. An isolated LBBB was associated with larger LV end-diastolic and end-systolic volumes (both p < 0.01) and lower LVEF (56+/- 7% vs. 68+/- 6%; p  <0.001) with similar myocardial contraction fraction. LVEF in isolated LBBB was nearly two standard deviations (Z = - 1.95) below mean sex and age-matched group values. LV stroke volume, cardiac output, and mass, and all RV parameters were similar (p = NS) between the groups.

CONCLUSIONS:

Adults with an isolated LBBB have greater LV volumes and markedly reduced LVEF, despite the absence of overt cardiovascular disease. These data may be useful toward the clinical interpretation of imaging studies performed on patients with an isolated LBBB.

KEYWORDS:

Cardiac function; Cardiovascular magnetic resonance; Left bundle branch block; Left ventricular ejection fraction; Left ventricular size

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