New onset left bundle branch block in a master athlete.

Description of Clinical Presentation: A 45-year-old man with no cardiovascular risk factors was referred for evaluation of recurrent presyncope. Two years earlier, he had undergone a normal clinical assessment prior to running a marathon. At presentation, the ECG demonstrated sinus rhythm, left bundle branch block (LBBB), fragmented QRS complexes in the inferior leads, and repolarization abnormalities in the lateral leads.

Diagnostic Techniques and Their Most Important Findings: Transthoracic echocardiography revealed a mildly dilated left ventricle (LV) with global hypokinesia, paradoxical interventricular septal (IVS) motion and a reduced ejection fraction (EF: 35%).
Cardiac magnetic resonance (CMR) demonstrated focal LV hypertrophy involving the basal and mid anteroseptal, basal and mid inferoseptal, and mid inferolateral segments. Thinning and akinesia were observed in the basal and mid anterior segments, along with mild global hypokinesia and moderate hypokinesia of the basal inferior segment. Paradoxical IVS motion was again noted, attributable to LBBB. LV systolic function was moderately reduced (EF: 38%). The right ventricle (RV) was not dilated but showed free wall hypertrophy, no regional wall motion abnormalities, and moderately impaired systolic function (EF: 39%). T2-weighted imaging revealed diffusely increased myocardial signal intensity. First-pass perfusion demonstrated resting perfusion defects in the basal anteroseptal, basal inferoseptal, basal inferolateral, and anteroapical segments, as well as in the mid inferoseptal segment and in the RV free wall. Phase Sensitive Inversion Recovery (PSIR) imaging demonstrated subepicardial, mesocardial and subendocardial late gadolinium enhancement (LGE) with transmurality >75% in multiple regions, including the basal and mid anteroseptal, basal and mid inferoseptal, basal inferolateral, mid anterolateral, basal and mid inferior, and anteroapical segments, as well as in the RV free wall and in the interatrial septum (IAS).
The combination of patchy LV wall thickening and thinning, multifocal perfusion defects, and heterogeneous LGE, together with RV and IAS involvement, was highly suggestive of cardiac sarcoidosis. Subsequent fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) confirmed patchy tracer uptake in the LV, RV, and in a paratracheal lymph node. Biopsy of this lymph node demonstrated focal granulomatous inflammation composed of lymphocytes, histiocytes, and multinucleated giant cells containing asteroid bodies, confirming the diagnosis of sarcoidosis.

Learning Points from this Case: This case underscores the value of multimodality imaging, particularly CMR, in the study of patients with new onset LBBB and in the approach to patients with suspected cardiac sarcoidosis. Recognition of combined LV, RV, and atrial involvement, supported by metabolic imaging and histology, was key to establishing the diagnosis. Early identification of cardiac sarcoidosis is essential given its prognostic implications, risk of arrhythmias, and the need for timely initiation of tailored therapy.

Perfusion sequence with multifocal perfusion defects in the LV & RV (SAX).
PSIR Imagng (2Ch (a); 3Ch (b); 4Ch (d); SAX (d)). with multifocal and heterogeneous LGE in LV, RV and IAS.
FDG PET/CT with a patchy tracer uptake in the LV & RV (a) and in a paratracheal lymph node (b).