DISCUSSION
Cardiac sarcoidosis is the most ominous manifestation of sarcoidosis
accounting for as much as 50% of deaths in patients with
sarcoidosis.8 The prevalence of cardiac involvement
amongst patients with systemic sarcoidosis varies widely for unknown
reasons, but ranges between 3.7 to 54.9% depending upon the imaging
techniques used and the population studied.4,14 There
is scanty data on CS in our setting and in Africa as a whole with no
case reports identified. The triad of cardiac manifestations are
conduction abnormality, ventricular tachycardia and heart failure.
CS though often clinically silent is frequently fatal. It’s wide
spectrum of clinical manifestations arise from the variable locations of
sarcoid lesions in the myocardium.4 There is however a
predilection for the base of the interventricular septum, the conduction
system and the left ventricular (LV) free wall, although, other parts of
heart including the papillary muscles, right ventricular wall, atria,
valve leaflets, intramyocardial vessels, pericardium and endocardium may
be involved.3,7,22 Indeed, both patients reported here
had involvement of the base of the interventricular septum, the
conduction system and the left ventricular (LV) free wall.
Conduction disease as observed in our report, is the most common
electrophysiologic manifestation of CS with a prevalence up to
62%.14 Complete heart block and bundle branch blocks
have been reported in 23-30% and 12-32%, respectively of patients with
myocardial sarcoidosis.7 Advanced AV blocks may lead
to syncope or sudden cardiac death, warranting inclusion of sarcoidosis
as a differential in the evaluation of patients with syncope, especially
when it occurs in young and middle-aged patients. Studies suggest CS may
be accountable for unexplained second or third degree atrioventricular
(AV) block in patients less than 60 years old 14,23.
Indeed, implantable cardioverter-defibrillators (ICDs) are recommended
for CS patients with complete heart block, prior ventricular
arrhythmias, cardiac arrest or LV ejection fraction of
<35%.24
A prospective evaluation of patients aged 18 to 60 years presenting with
unexplained Mobitz II or 3rd degree AVB and no previous history of
sarcoidosis by Nery et al found that 34% of patients had CS and were
more likely to experience major adverse cardiac
events.25 Data from the National Inpatient Sample
(NIS) database from 2012-2014 has shown that complete heart block is
more prevalent among patients with sarcoidosis compared to those without
a diagnosis of sarcoidosis and increased the odds of developing complete
heart block among other medical comorbidities like coronary artery
disease, age, gender and heart failure.26
A recent Finnish study of 325 cases of cardiac sarcoidosis from the
Myocardial Inflammatory Diseases in Finland Study Group Registry
diagnosed from 1988 to 2015, reports that 143 (44%) patients presented
with Mobitz II second degree or third degree AVB in the absence of other
explanatory cardiac disease.27 Likewise, another
Finnish study of 72 patients aged <55 presenting with
new-onset, unexplainable Mobitz II second degree or third degree AVB, 14
of 72 (19%) patients had histologically confirmed CS whilst another 4
(6%) had giant cell myocarditis.23
Bundle branch blocks are also a frequent occurrence in CS patients. Our
first case had left bundle branch block (LBBB) which is known to be less
common compared to right bundle branch blocks
(RBBB).7,28,29 Schuller et al found that among a
cohort of patients with biopsy – proven pulmonary sarcoidosis a BBB
pattern is associated with cardiac involvement 29 and
RBBB pattern was more prevalent than LBBB in the CS population in a
Danish study.28
Cardiac sarcoidosis is frequently overlooked as the underlying cause of
heart failure and accounts for 25 – 75% of cardiac deaths in patients
with cardiac sarcoidosis. Left ventricular systolic and diastolic
dysfunction leading to progressive congestive heart failure often occurs
due to conduction or rhythmic abnormalities, or as a result of extensive
myocardial infiltration or both.7,10,30 A study of
core LV biopsies obtained during LV assist device implantation showed
granulomatous myocarditis consistent with sarcoidosis in previously
undiagnosed CS in 6 of 177 mixed cardiomyopathy patients
(3.4%).31 In an examination of explanted hearts,
Roberts et al found that among 130 heart transplants with a clinical
diagnosis of non-ischaemic cardiomyopathy, 8 (6.2%) had undiagnosed
CS.32
Due to the low sensitivity of endomyocardial biopsy, cardiac MRI has
become the investigation of choice for cardiac sarcoidosis in the
patient with a high clinical suspicion. As recommended by experts’
consensus, clinical symptoms with consistent advanced cardiac MRI
findings should be combined with histological presence of noncaseating
granulomas demonstrated in biopsy of other sites of involvement such as
the skin or lungs. In both cases presented, the presence of cardiac
complications prevented biopsy of lung tissue via CT-guided biopsy as
endobronchial ultrasound transbronchial needle aspiration (EBUS-TBNA) is
not available in our practice. High resolution CT-scan (HRCT) of the
chest which has significant correlation with histology in the diagnosis
of pulmonary sarcoidosis was highly suggestive in both cases and
supported by some laboratory markers such as serum ACE level and
hypercalcaemia. 33
Broadly, current treatment for CS involves immunosuppression and
antiarrhythmic agents for inflammation and antiarrhythmic drugs and/or
ablation for scar formation/fibrosis. Optimal duration of treatment
remain controversial, but corticosteroids and other immunosuppressive
agents improve cardiac function, prevent further formation of
granulomas, and reduce arrhythmias and incidence of sudden cardiac death
as depicted in the cases presented, but patients with advanced cardiac
dysfunction (LV ejection fraction <30%) may remain
unresponsive to corticosteroid therapy.3,15,34–36Even though corticosteroids remain the cornerstone in the treatment of
clinically active or symptomatic CS, dosing, selection and timing and
duration of therapy for cardiac sarcoidosis remains
controversial.20,36 Late gadolinium enhancement in
Cardiac MRI has emerged as an important tool for risk stratification for
sudden cardiac death (SCD) in CS and is of key importance in the
decision for ICD implantation in CS patients considered at high risk for
SCD. Although both patients in this report had LGE on their cardiac MRI
scans for which an ICD was indicated, this service was not available in
our country.