|Number 15-00: Etiology of Atrioventricular Block Visualized by CMR|
number 15-00: Etiology of atrioventricular block visualized by cardiac magnetic resonance
Authors - Barbara E. U. Burkhardt, MD, Christian Balmer, MD PhD, Angela Oxenius MD, Emanuela R. Valsangiacomo Buechel MD PhD
Affiliation - Paediatric Heart Centre, Division of Pediatric Cardiology, University of Zurich, Switzerland
An 8-year old girl with a structurally normal heart presented with acute symptoms of low cardiac output. ECG revealed complete atrio-ventricular block with a ventricular rate of 35 bpm and wide QRS complexes (120 ms) with variable axis deviation and bundle branch block morphology (Figure 1).
Temporary VVI pacing in the right ventricle was started transfemorally. AV conduction improved spontaneously one day later, but a bifascicular block persisted (right bundle branch block and left anterior hemiblock)(Figure 2). Two days later, bigeminal ventricular ectopic beats and an episode of non-sustained ventricular tachycardia were registered (Figure 3).
Figure 1: Electrocardiogram: complete AV block
Figure 2: Electrocardiogram: right bundle branch block and left anterior hemi-block
Figure 3: Electrocardiogram (top) and arterial pressure (bottom): ventricular tachycardia
Cardiac magnetic resonance (CMR) was performed on a General Electric 1.5 Tesla scanner. In the acute phase, CMR showed decreased ejection fractions (33%) in both ventricles. Cine sequences demonstrated akinesia/dyskinesia of the proximal interventricular septum and in the right ventricular apex (Movies 1 and 2). Late gadolinium enhancement (LGE) was positive in the proximal ventricular septum (Figure 4), in the anterior septum, and in the inferior segments of both ventricles (Figure 5), which represent the localization of the conduction anomalies observed in this patient.
Movie 1: ECG-gated SSFP images in horizontal long axis (four chamber) view showing hypokinesia of the proximal interventricular septum
Movie 2: ECG-gated SSFP images in short axis slices showing thinning and hypokinesia of the proximal interventricular septum
ECG-gated SSFP images in short axis slices showing thinning and hypokinesia of the proximal interventricular septum
Figure 4: Late gadolinium enhancement (LGE) in the proximal ventricular septum (arrow)
Figure 5: Late gadolinium enhancement (LGE) in the inferior segments of both ventricles (arrow)
Acute lymphocytic myocarditis was demonstrated by endomyocardial biopsy. During follow up, AV conduction recovered further, except for a complete right bundle branch block. Five months later, CMR demonstrated improved global ventricular function (LVEF 53%) but a persistent scar with inferoseptal thinning and LGE of the left ventricular myocardium (Figure 6).
Figure 6: Inferoseptal thinning (left panel) and LGE (right panel) of the left ventricular myocardium (arrows)
LGE is correlated with inducible ventricular tachycardia and sudden death in many myocardial diseases, such as ischemic, hypertrophic, dilated, or arrhythmogenic right ventricular cardiomyopathy as well as in chronic Chagas’ heart disease (Mavrogeni 2013). The presence and the extent of LGE is also associated with recurrent tachyarrhythmia and even sudden cardiac arrest (Neilan 2015). New onset left bundle branch block has been described in patients with myocarditis (Mavrogeni 2014).
We report a case of acute lymphocytic myocarditis with a pattern of LGE correlating with conduction disturbances such as total AV Block, and with ventricular arrhythmia. This case illustrates the occurrence of right bundle branch block, left anterior hemi-block, and even transient complete atrioventricular block in myocardial inflammation and its visibility by CMR.
This case proves that CMR examination with LGE is able to demonstrate substrates of electrophysiological disturbances during myocardial inflammation.
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