An unusual cardiac magnetic resonance finding in a patient with syphilis presenting with heart block

Syphilis is caused by Treponema pallidum either via sexual exposure or vertical transmission during pregnancy. The disease course of infected individuals is divided into primary, secondary, and tertiary stages over a period of years. Latent syphilis most commonly involves the central nervous system and the aorta. Here we present a case of late latent syphilis presenting as heart block with evidence of myocardial fibrosis involving the septum and lateral wall in cardiac MRI. A 53-year-old female patient, who was clinically diagnosed with late latent syphilis, presented with multiple episodes of syncopal attacks and was rushed to an outside hospital where ECG revealed a complete heart block. She was referred to our tertiary care centre. The patient was received in the Cardiac Care Unit and then referred for a cardiac MRI to identify a potential cause for the complete heart block. Recently published new Lake Louise criteria (nLLC) (Li et al. in Front Cardiovasc Med, 2021. https://doi.org/10.3389/fcvm.2021.739892), following the introduction of myocardial mapping, redefined imaging diagnosis according to the combined presence of a T1 criterion [presence of LGE (late gadolinium enhancement) or increased T1 mapping or extracellular volume values] and a T2 criterion (hyperintensity in T2 weighted STIR or increased T2 mapping values). Cardiac MRI features in our case were consistent with myocarditis based on the above criteria. Myocarditis as a manifestation of late latent syphilis is very rare. Cardiac complications of late syphilis have so far been described in terms of ascending aortitis and dissection with coronary artery rupture. Syphilitic myocarditis occurs most commonly as a coincidental finding of endomyocardial biopsies. Targeted screening for involvement using CMR can be instrumental in elucidating this rare, but treatable diagnosis. We hereby report a rare case of myocarditis with heart block in a patient with late latent syphilis, hitherto unreported in the literature as of date.


Background
Syphilis is caused by Treponema pallidum either via sexual exposure or vertical transmission during pregnancy. The disease course of infected individuals is divided into primary, secondary, and tertiary stages over a period of years [1]. In the stage of primary syphilis, the patient presents with chancre, especially on the genitals and regional lymphadenopathy. Following the resolution of the primary lesion, fever and maculopapular rash occur a few weeks later, which represents the secondary phase [1]. Latent syphilis most commonly involves the central nervous system and the aorta. Myocarditis as a manifestation of late latent syphilis is very rare [2]. We report a unique case of latent syphilis presenting as myocardial fibrosis. Nandagopal and Sathyanathan Egypt J Radiol Nucl Med (2023) 54:10

Case presentation
A 51-year-old female had episodes of syncope and headache a few months back for which the patient had consulted a neurologist. MR imaging of the brain was done to look for organic causes, which revealed no significant abnormality. The patient also had complaints of blurring of vision and was diagnosed with papillitis and was advised to screen for sexually transmitted diseases which revealed a positive Treponema pallidum hemagglutination (TPHA) test and a non-reactive Venereal Disease Research Laboratory (VDRL) test. She was referred to a sexually transmitted diseases clinic in our tertiary care centre and incidentally detected to have ulcers in bilateral groin regions. Serial investigations revealed Venereal Disease Research Laboratory (VDRL)-NR, VCTC (Voluntary Counselling and Testing Center) − ve, Treponema pallidum hemagglutination (TPHA). + ve, HSV (Herpes simplex virus) 1, 2 IgM − ve. The culture for Trichomonas vaginitis and candida was negative. Hence, based on laboratory and clinical findings, the patient was diagnosed with late latent syphilis. Currently, she had presented with multiple episodes of syncopal attacks and was rushed to an outside hospital where ECG (electrocardiogram) revealed a complete heart block. She was again referred to our tertiary care centre. The patient was received in the cardiac care unit, following which she was stabilized.
IM Penicillin injection was continued for late latent syphilis.
The patient was then referred for cardiac MRI to identify a potential cause for the complete heart block. The magnetic resonance imaging was performed in 3T magnetic resonance scanner (Siemens Healthineers, Erlangen, Germany). Standard institute cardiac MR protocol with TRUFISP (True Fast Imaging with steady-state free precision) (white blood) images and HASTE (half Fourier single-shot turbo spin echo) (dark blood) axial and coronal sections were done for morphologic imaging. Twochamber, four-chamber, and short-axis cine images were obtained to evaluate wall motion abnormalities and cardiac function. Parametric mapping with Native T1 and T2 mapping was done, and ECV (extracellular volume) was calculated as per SCMR (Society for Cardiovascular magnetic resonance) guidelines. Pre-contrast T1 maps were obtained from three short-axis images (basal, mid cavity, and apical) of the left ventricle using a single short true FISP based on the modified look-locker inversion recovery (MOLLI) sequence.
Gadolinium contrast was administered at 0.1 mmol/ kg. Late gadolinium images were obtained at 10, 12, and 15 min. The findings noted in cardiac MRI were significant hypertrophy (18 mm) of the lateral wall of base of left ventricle ( No significant wall motion abnormality was noted, and a normal ejection fraction was observed. A temporary pacemaker was inserted to maintain cardiac rhythm. Hence in a patient with late latent syphilis (clinical and laboratory results positive), the above features in parametric mapping and late gadolinium enhancement reflect myocardial infiltration/myocarditis.
To rule out other causes of myocarditis, an infectious panel was done and Treponema pallidum hemagglutination (TPHA) was found to be positive. Investigations for Candida, HSV, Trichomonas, Rubella, Adenovirus, parvovirus, enterovirus, EBV, CMV, and mumps were found to be negative. KOH smear was negative. Venereal Disease Research Laboratory (VDRL) was non-reactive, and VCTC (Voluntary Counselling and Testing Center) was negative. A neurologist's opinion was sought and lumbar puncture was attempted to obtain a diagnostic CSF (cerebrospinal fluid) tap, which was found to be acellular with no growth on CSF culture. Blood cultures were found to be negative.
The patient was later referred to PET (positron emission tomography) scan, which revealed status post-temporary cardiac pacing with few nonspecific subcentimetric nodules in both lungs with low-grade FDG avidity.
A few prominent mediastinal lymph nodes were seen with a few of them showing mild increased FDG (fluorodeoxyglucose) avidity, the largest subcarinal node measuring ~ 19 × 12 mm (SUV max = 3.4).
The likelihood of infective aetiology was suggested, and a differential of sarcoidosis was suspected; however, no other characteristic features like interlobular septal thickening and perilymphatic nodules were detected. ACE (angiotensin-converting enzyme) levels were done to rule out sarcoidosis and were found to be within normal limits. TB quantiferon samples were also sent, which were found to be negative.
Dilated left ventricle with patchy increased metabolic activity was seen in the wall of the left ventricle (SUV  (Fig. 6). Increased metabolic activity was also seen along the right lateral wall of the superior vena cava. Repeated attempts to withdraw the patient from a temporary pacemaker resulted in the patient developing RBBB (right bundle branch block) or CHB (Complete heart block) 2-3 days post-temporary pacemaker removal.
Hence, a permanent pacemaker was inserted, following which the patient maintained a normal sinus rhythm. Based on the above findings, a clinical diagnosis of late latent syphilis, with a rare manifestation presenting as a complete heart block, was made, following which the patient was discharged and advised followup. Cardiac MRI with parametric mapping and delayed contrast imaging was helpful not only in picking up the correct diagnosis of myocarditis in this patient with a

Discussion
The clinical manifestations of syphilis are due to the local inflammatory response elicited by spirochetes. At present, serological tests are utilized to diagnose syphilis both in symptomatic patients and as a screening tool in asymptomatic patients. Serodiagnostic tests for syphilis can be broadly categorized into non-treponemal tests (NTTs)-Venereal Disease Research Laboratory (VDRL) tests-and treponemal tests (TTs)-T. pallidum haemagglutination (TPHA) assay [1].
NTTs measure immunoglobulins (IgM and IgG) produced in response to lipoidal material released from bacteria. In patients who have been diagnosed and have not undergone any treatment, the titre reaches its peak 1-2 years after infection and has low titres even in the late stage of the disease [1]. In cases where the patient has undergone treatment, the titres usually decline and become non-reactive 6 months later in immunocompetent individuals, whereas TTs used to detect the antibodies that are produced against T. pallidum proteins are highly specific. TTs become positive 6-14 days after the primary chancre appears and may be used to diagnose early syphilis missed by NTT tests [1].
We have accustomed ourselves to thinking of latent syphilis as involving most commonly the central nervous system and the aorta. Myocarditis as a manifestation of latent syphilis is extremely rare [2]. Cardiac MR imaging may play a major role in the identification of this entity, with the findings of diffuse non-ischaemic (epicardial and intramyocardial) late gadolinium enhancement pattern within the LV myocardium and elevated native T1 and native T2 values [2], reflecting fibrosis.
In our case, the presence of late gadolinium enhancement in anteroseptal and anterolateral walls reflects focal myocardial fibrosis. Parametric mapping also revealed a corresponding increase in native T1 and T2 values as well as ECV values, reflecting ongoing myocarditis. No other areas of increased values were noted in the rest of the myocardium.
This presence of focal myocardial infiltration may reflect myocarditis or focal infiltrative lesion.
The gold standard for the diagnosis of acute myocarditis is still endomyocardial biopsy (EMB). However, EMB being an invasive procedure has several limitations, such as lack of standard protocols, sampling errors, and low sensitivity [3]. Since the clinical condition of our patient was not conducive to myocardial biopsy, the latter could not be done to obtain the pathological diagnosis.
Recently published new Lake Louise criteria (nLLC) [3], following the introduction of myocardial mapping, redefined imaging diagnosis according to the combined presence of a T1 criterion (presence of LGE or increased T1 mapping or extracellular volume values) and a T2 criterion (hyperintensity in T2 weighted STIR or increased T2 mapping values).
Cardiac MRI features in our case were consistent with myocarditis based on the above criteria. This is one of the very few rare reports of cardiac MR showing myocardial infiltration in a patient with clinically proven syphilis, presenting with heart block. Other viral causes of myocarditis were excluded. PET scan  features also did not suggest the possibility of sarcoidosis. Based on the above features, it was concluded that the cause of myocarditis in this patient with heart block was syphilis.
The heart block could be explained due to the presence of fibrosis involving the conducting system, elegantly depicted with cardiac MRI [4].

Conclusions
Myocarditis as a manifestation of late latent syphilis is very rare. Cardiac complications of late syphilis have so far been described in terms of ascending aortitis and dissection with coronary artery rupture. Syphilitic myocarditis occurs most commonly as a coincidental finding of endomyocardial biopsies. Targeted screening for involvement using CMR can be instrumental in elucidating this rare, but treatable diagnosis. We hereby report a rare case of myocarditis with heart block in a patient with late latent syphilis, hitherto unreported in literature as of date.