Corner Case -2​ : August 2021

Contributed by Pudhiavan A

MBBS, MD(RD), FCTI (EACVI Level 3)
Consultant Cardiothoracic Radiologist, Department of Radiology and imaging services,
Kovai Medical Centre & Hospital, Coimbatore, Tamil Nadu.

Clinical details: A 35-year-old male, presented with a history of giddiness and presyncope. The patient underwent a routine cardiac evaluation to rule out the cardiac cause of syncope. ECG revealed a complete heart block with bradycardia. Echocardiography revealed normal-sized cardiac chambers with normal systolic function and mild grade 1 diastolic dysfunction. The patient was referred to the radiology department for cardiac MRI to find the cause for heart block and to rule out the presence of infiltrative cardiomyopathy.

Review the representative images from the cardiac MRI.
What is the likely diagnosis?
What would be the next steps in diagnosis and treatment?
Imaging Findings:
CMR revealed normal-sized cardiac chambers with normal indexed left ventricular end-diastolic (LVEDV) and end-systolic volumes (LVESV). No left ventricular (LV) hypertrophy is seen with normal wall motion. No abnormal wall thinning is also seen (Fig 1). Brady arrhythmia was seen throughout the study with an average heart rate of 40-45 bpm.

Delayed enhancement PSIR images taken 10 minutes after gadolinium injection revealed a focal area of late gadolinium enhancement (LGE) in the basal anteroseptal segment of LV myocardium in the subendocardial location and the RV side of septum near the tricuspid septal leaflet attachment (Fig 2). This corresponds to the location of the His bundle in the septum and thus could explain the heart block. The rest of the LV myocardium revealed uniform nulling with no other focus of LGE. Native and post-contrast T1 mapping of the heart also revealed normal native T1 and extracellular volume (ECV) values in the uninvolved rest of the LV myocardium, suggesting no other focus of myocardial infiltration/ fibrosis (Fig 3). A T1 Dixon post-contrast image of the chest acquired in a single breath-hold revealed multiple enlarged nodes in the bilateral hilar, subcarinal, pre tracheal and para-aortic regions (Fig 4). A CT correlation obtained revealed normal lung parenchyma (Fig 4).

Fig 1: Cine bSSFP images in 2 chamber (A&B), 4 chamber (C&D) and short axis (E&F) views. in end diastole (A,C,E) and end systolic (B,D,F) phases.

Fig 2: Delayed enhancement PSIR images in short axis (A) and 4 chamber (B) views.

Fig 3: Native T1 and T1 enhanced maps in short axis mid cavity level (The normal native T1 values at 1.5T in our institution is 975 ± 50 ms).

Fig 4: (A) Coronal T1 post contrast Dixon image (B) Axial CT image through mid thorax in lung window.

Likely Diagnosis
In view of the specificity of focal LGE in the region of His bundle with heart block and the mediastinal and hilar adenopathy, a diagnosis of infiltrative cardiomyopathy due to sarcoidosis was made.
Further steps in diagnosis and management
The patient underwent a PET-CT to confirm the diagnosis, which showed multiple hilar and mediastinal adenopathy with FDG uptake. Note FDG uptake in basal  anteroseptal segment. Lateral wall uptake is artefactual. He underwent a permanent pacemaker implantation (PPI) with selective bundle branch pacing (Fig 6). Lymphnode biopsy was also planned for planning medical management.

Fig 5: PET-CT showing intense FDG uptake in hilar and mediastinal nodes (Black arrow) with focal tracer uptake in the basal septum (White arrow) corresponding to region of LGE on CMR.

Fig 6: Cath angiography with PPI implantation and selective bundle branch pacing.

Discussion
Sarcoidosis is a granulomatous multi system disease of unknown aetiology with variable involvement of the heart. Familial clustering of cases also indicate a strong genetic predisposition (1). Arrhythmias are often the most frequent feature of cardiac sarcoidosis, which include supraventricular tachycardia (SVT), ventricular tachycardia (VT), bundle branch and AV blocks. Presence of atrial LGE on CMR is associated with a three times greater likelihood of developing symptomatic atrial arrhythmias (2). CMR is extremely useful in initial diagnosis and subsequent follow up of treatment response in cardiac sarcoidosis. Non contrast CMR findings are non-specific with ventricular diastolic or systolic dysfunction, focal wall thinning and regional wall motion abnormalities not corresponding to a vascular territory and focal areas of myocardial oedema in active inflammation. Sarcoidosis typically has a patchy and multifocal LGE with sparing of the endocardium and no specific pattern of LGE (3). CMR plays a crucial role in prognostication as it is observed that people with more extensive LGE are at increased risk of ventricular arrhythmias and sudden cardiac death, irrespective of ejection fraction (4). FDG-PET is another important tool in the identification of active inflammation and differentiating it from scarred myocardium, both of which will show LGE (5). T1 and T2 mapping are increasingly used to identify subtle areas of inflammation and scarring (6).
Reference:
  1. Birnie DH, Nery PB, Ha AC, Beanlands RS. Cardiac sarcoidosis. J Am Coll Cardiol. 2016;68: 411–21. 86.
  2. Cain MA, Metzl MD, Patel AR, et al. Cardiac sarcoidosis detected by late gadolinium enhancement and prevalence of atrial arrhythmias. Am J Cardiol 2014;113:1556–60. 110.
  3. Smedema JP, Snoep G, van Kroonenburgh MP, et al. Evaluation of the accuracy of gadolinium-enhanced cardiovascular magnetic resonance in the diagnosis of cardiac sarcoidosis. J Am Coll Cardiol 2005;45:1683–90.
  4. Greulich S, Deluigi CC, Gloekler S, et al. CMR imaging predicts death and other adverse events in suspected cardiac sarcoidosis. J Am Coll Cardiol Img 2013;6:501–11.
  5. Pellegrino D, Bonab AA, Dragotakes SC, Pitman JT, Mariani G, Carter EA. Inflammation and infection: imaging properties of 18F-FDG-labeled white blood cells versus 18F-FDG. J Nucl Med 2005;46:1522–30. 137.
  6. Iles L, Pfluger H, Phrommintikul A, et al. Evaluation of diffuse myocardial fibrosis in heart failure with cardiac magnetic resonance contrast- enhanced T1 mapping. J Am Coll Cardiol 2008; 52:1574–80.
Acknowledgement: Dr Lawrance Jesuraj, Consultant interventional Cardiologist and electrophysiologist, KMCH, Coimbatore.