We report the case of an 11-year-old child with multisystem inflammatory syndrome
in children (MIS-C) related to COVID-19 who developed cardiac failure and died after
1 day of admission to hospital for treatment. An otherwise healthy female of African
descent, the patient was admitted to the paediatric intensive care unit (ICU) with
cardiovascular shock and persistent fever. Her initial symptoms were fever for 7 days,
odynophagia, myalgia, and abdominal pain. On admission to the ICU, the patient presented
with respiratory distress, comprising tachypnoea (respiratory rate 70 breaths per
min) and hypoxia, and signs of congestive heart failure, including jugular vein distention,
crackles at the base of the lungs, displaced liver, hypotension (blood pressure 80/36
mm Hg), tachycardia (134 beats per min [bpm]), and cold extremities with filiform
pulses. Non-exudative conjunctivitis and cracked lips were present on physical examination.
The patient was promptly intubated and antibiotic treatment was started with ceftriaxone
and azithromycin. Peripheral epinephrine was initiated in the emergency room before
the patient was moved to paediatric ICU.
A point-of-care echocardiogram showed diffuse left-ventricular hypokinesia with no
segmental wall motion abnormalities. Left-ventricular ejection fraction was estimated
with the M-mode Teichholz method in the parasternal short axis view, at the level
of the papillary muscles of the mitral valve; substantial myocardial dysfunction was
noted, with decreased left-ventricular ejection fraction (31%) and no respiratory
collapsibility of the inferior vena cava. The patient received furosemide, and central
line and invasive arterial monitoring were established. Initial radiography showed
an enlarged cardiac area and bilateral lung opacities (appendix p 1). Chest CT showed
multiple ground-glass pulmonary opacities associated with thickening of interlobular
septa and sparse bilateral foci of consolidation, predominantly in the peripheral
and posterior areas of lower lobes (appendix p 1).
Laboratory results showed high concentrations of markers of systemic inflammation
and myocardial injury, including C-reactive protein, interleukin-6, ferritin, triglycerides,
D-dimer, troponin, and creatine kinase myocardial band. Moreover, a left-shifted white-blood-cell
count and substantial lymphopenia were seen. Blood gas analysis showed hypoxia and
acidosis (table
).
Table
Laboratory results at various timepoints after presentation
0 h
7 h
14 h
17 h
24 h
Normal range
Haemoglobin, g/dL
10·0
11·8
12·1
11·4
11·0
12·7–14·7
Hematocrit, %
28·8%
34·3%
36·4%
34·3%
33·0%
38·0–44·0%
Platelets, ×103 cells per μL
167
..
191
..
145
150–450
White blood cell count, ×103 cells per mm3
25·73
24·28
35·90
40·30
38·22
4·50–14·40
Lymphocytes, %
1·03%
0·73%
0·36%
0·40%
3·44%
38·00–42·00%
Urea, mg/dL
67
73
78
78
93
11–38
Creatinine, mg/dL
1·27
1·31
1·56
1·73
2·19
0·53–0·79
D-dimer, ng/mL
11 495
..
54 153
..
..
<500
Troponin, ng/dL
0·281
..
0·290
0·342
..
<0·014
Creatine kinase myocardial band, ng/dL
5·76
..
28·50
15·66
..
0·10–2·88
Interleukin-6, pg/mL
4105·0
..
..
..
..
0·2–7·8
Creatine kinase, U/L
96
..
..
..
..
<167
Blood pH
7·21
7·30
..
7·28
7·31
7·35–7·45
Bicarbonate, mEq/L
15·7
16·4
..
17·6
17·2
21·0–28·0
PaCO2, mm Hg
41
32
..
31
..
35–45
PaO2, mm Hg
60
270
..
133
..
80–90
ScvO2, %
87·2%
97·3%
..
82·0%
82·2%
60·0–85·0%
Lactate, mg/dL
38·0
39·0
..
27·0
..
4·5–14·4
C-reactive protein, mg/dL
266·6
..
309·5
..
..
<500
Total protein, g/dL
5·0
..
..
..
..
6·0–8·0
Albumin, g/dL
2·6
..
..
..
..
3·8–5·4
Aspartate aminotransferase, U/L
61
..
67
..
..
13–35
Alanine aminotransferase, U/L
67
..
67
..
..
7–35
Oxygenation index
..
3·1
..
4·2
..
<4·0
International normalised ratio
..
..
1·4
..
..
0·9–1·2
Fibrinogen, mg/dL
..
..
513
..
..
200–393
Ferritin, ng/mL
..
..
..
1501
..
20–200
Triglycerides, mg/dL
..
..
..
162
..
<100
PaCO2=partial pressure of carbon dioxide in arterial blood. PaO2=partial pressure
of oxygen in arterial blood. ScvO2=central venous saturation of oxygen.
Mechanical ventilation was implemented during the first hour in the ICU and ventilatory
parameters reached a maximum positive end-expiratory pressure of 8 cm H2O and peak
inspiratory pressure of 25 cm H2O, with an initial fraction of inspired oxygen of
60%. After initiation of mechanical ventilation and use of diuretics, ventilatory
parameters could be reduced and less opacification was seen on chest radiography.
The patient had sinus tachycardia throughout the hospital stay (heart rate >200 bpm);
the initial electrocardiogram is shown in figure 1
. The patient progressed to hyperdynamic vasoplegic shock refractory to volume resuscitation
and vasoactive agents. After 28 h of hospital admission, she developed ventricular
fibrillation and died.
Figure 1
Electrocardiogram showing sinus tachycardia on admission
An ultrasound-guided minimally invasive autopsy was done, with tissue sampling of
the heart, lungs, liver, spleen, kidneys, brain, inguinal lymph node, quadriceps muscle,
and skin.
1
Post-mortem CT angiography was done before tissue collection and did not show any
signs of coronary artery alterations (appendix p 2). Post-mortem ultrasound examination
of the heart showed a hyperechogenic and diffusely thickened endocardium (mean thickness
10 mm), a thickened myocardium (18 mm thick in the left ventricle), and a small pericardial
effusion. Histopathological examination showed myocarditis, pericarditis, and endocarditis
characterised by inflammatory cell infiltration (figure 2A
). Inflammation was mainly interstitial and perivascular, associated with foci of
cardiomyocyte necrosis (figure 2B, C), and was mainly composed of CD68+ macrophages
(figure 2E), a few CD45+ lymphocytes (figure 2F), and a few neutrophils and eosinophils.
C4d immunostaining was used for detection of cardiomyocyte necrosis (figure 2D). Analysis
of cardiac tissue by electron microscopy identified spherical viral particles of 70–100
nm in diameter, consistent in size and shape with the Coronaviridae family, in the
extracellular compartment and within several cell types—cardiomyocytes, capillary
endothelial cells, endocardium endothelial cells, macrophages, neutrophils, and fibroblasts
(figure 3
). Microthrombi in the pulmonary arterioles (appendix p 3) and renal glomerular capillaries
were also noted at autopsy. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-associated
pneumonia was mild, with patchy exudative changes in alveolar spaces and mild pneumocyte
hyperplasia (appendix p 3). Lymphoid depletion and signs of haemophagocytosis were
noted in the spleen and lymph nodes, indicating secondary haemophagocytic lymphohistiocytosis
associated with systemic inflammation. Acute tubular necrosis in the kidneys and hepatic
centrilobular necrosis, secondary to shock, were also seen. Brain tissue showed microglial
reactivity.
Figure 2
Post-mortem histological findings
(A) Diffuse myocardial interstitial inflammation. (B, C) Interstitial and perivascular
myocardial inflammation containing lymphocytes, macrophages, a few neutrophils and
eosinophils, and foci of cardiomyocyte necrosis. (D) Myocardial necrosis indicated
by C4d staining. (E, F) Myocardial interstitial inflammation containing CD68+ (E)
and CD45+ (F) cells.
Figure 3
Post-mortem electron microscopy findings
(A) Part of a cardiomyocyte, with viral particles (arrows) within a cytoplasmic area
close to the nucleus. (B) Part of a fibroblast; arrow points to a viral particle inside
a ruptured fragment of the rough endoplasmic reticulum. Inset in (B) corresponds to
a higher magnification of the virus. (C) Endothelial lining (endocardium and subendocardium)
of the left ventricular lumen; two viral particles (arrows) are present inside the
endocardial endothelial cell. (D) Neutrophil in late stages of NETosis; asterisks
indicate neutrophil extracellular traps (decondensed and dispersed chromatin); arrow
points to a viral particle inside a cytoplasmic vesicle. Inset in (D) shows the viral
particle at high magnification. cm=cardiomyocyte. col=collagen fibrils. end=endothelial
cell. mf=myofibrils. NET=neutrophil extracellular trap. nu=nucleus. se=subendocardial
fibroblast.
SARS-CoV-2 RNA was detected on a post-mortem nasopharyngeal swab and in cardiac and
pulmonary tissues by real time RT-PCR using primers and probes set for E (envelope)
gene.
2
Cycle threshold values for lung and heart samples were 35·6 and 36·0, respectively,
suggesting a low viral load in both organs.
To investigate a primary immunodeficiency, whole-exome sequencing from genomic DNA
extracted from whole blood was done, using a customised Twist Human Core Exome kit
(Twist Bioscience, San Francisco, CA, USA) for exon capture, and sequenced in an Illumina
NovaSeq platform (Illumina, San Diego, CA, USA). Sequence reads were aligned to the
reference human genome (GrCh38/hg38 in the University of California Santa Cruz [UCSC]
Genome Browser) with Burrows-Wheeler Aligner software. Genotyping was done using the
Genome Analysis Toolkit (Broad Institute, Cambridge, MA, USA).
3
No pathogenic, likely pathogenic, or variant of unknown significance was found associated
with inborn errors of immunity.
MIS-C is a severe clinical condition that has been described in several paediatric
patients diagnosed with COVID-19 and that might be associated with cardiac dysfunction.4,
5, 6, 7, 8, 9, 10 Since the disorder shares similarities with Kawasaki disease, it
has also been reported as Kawasaki-like disease or Kawasaki-like multisystem inflammatory
syndrome.4, 5, 6, 7, 8 A substantial increase in the incidence of Kawasaki-like disease
has been described in several countries with high incidence of COVID-19.4, 5, 7 In
Italy, the first European country to be affected by the COVID-19 pandemic, Verdoni
and colleagues
4
found that, over a period of 1 month, the spread of SARS-CoV-2 was associated with
a 30-fold increase in the incidence of Kawasaki-like disease. Compared with classic
Kawasaki disease, children with MIS-C are older, have respiratory, gastrointestinal,
neurological, and cardiovascular involvement, substantial lymphopenia, thrombocytopenia,
and markers of myocarditis.4, 7, 8 Although previous studies have reported low mortality
among children with MIS-C (<2%), patients presented with cardiogenic shock, acute
left-ventricular dysfunction, and signs of myocarditis, indicating a potential risk
of a life-threatening condition.4, 5, 6, 7, 8, 9, 10 The mechanism of heart failure
in these patients and its relation to SARS-CoV-2 infection is not understood.
Possible mechanisms involved in cardiac dysfunction in children with COVID-19 include
myocardial stunning or oedema associated with a severe systemic inflammatory state,
direct myocardial injury by SARS-CoV-2, and hypoxia secondary to viral pneumonia.4,
5, 6, 7, 8, 9, 10, 11 Reports of substantial numbers of children presenting with MIS-C
or Kawasaki-like disease during the COVID-19 pandemic indicate that SARS-CoV-2 is
probably a trigger of this clinical condition, either by eliciting a severe systemic
immune response or by direct tissue damage, or both.4, 5, 6, 7, 8, 9, 10
Our case report shows inflammatory changes in the cardiac tissue of a child with MIS-C
related to COVID-19, which led to cardiac failure and death. SARS-CoV-2 could be detected
in cardiac tissue by RT-PCR and electron microscopy. Despite the evident systemic
inflammation and final progression to multiorgan failure, clinical, echocardiographic,
and laboratory findings strongly indicated that heart failure was the main determinant
of the fatal outcome. Further, the autopsy showed myocarditis, pericarditis, and endocarditis,
with intense and diffuse tissue inflammation, and necrosis of cardiomyocytes. Moreover,
the finding of SARS-CoV-2 in heart tissue indicates that myocardial inflammation was
probably a primary response to the virus-induced injury to cardiac cells. The presence
of SARS-CoV-2 in different cell types of cardiac tissue suggests potential mechanisms
for heart damage. First, infection of cardiomyocytes probably leads to local inflammation
in response to cell injury; both the virus-induced injury and the inflammatory response
could lead to necrosis of cardiomyocytes. The finding of viral particles in neutrophils
supports the idea of virus-induced inflammation. Also, infection of endothelial cells
in the endocardium could result in haematogenous spread of SARS-CoV-2 to other organs
and tissues.
Detection of both SARS-CoV-2 RNA by RT-PCR and viral particles by electron microscopy
in cardiac tissue has been reported in endomyocardial biopsy specimens from adults
with COVID-19.12, 13 Tavazzi and colleagues
13
detected viral particles in cardiac macrophages in an adult patient with acute cardiac
injury associated with COVID-19; no viral particles were seen in cardiomyocytes or
endothelial cells. Our case report is the first to our knowledge to document the presence
of viral particles in the cardiac tissue of a child affected by MIS-C. Moreover, viral
particles were identified in different cell lineages of the heart, including cardiomyocytes,
endothelial cells, mesenchymal cells, and inflammatory cells.
Two other reports in adolescents with COVID-19 detected myocarditis by MRI or at autopsy.14,
15 In the report from Craven and colleagues,
15
histological analysis of the heart of a 17-year-old boy showed diffuse myocarditis
with mixed inflammatory infiltrate, with a predominance of eosinophils. In our case
report, cardiac inflammation also included a small number of eosinophils. In these
two previous reports,14, 15 common symptoms of COVID-19 were absent, except for fever;
pulmonary changes were absent or mild, and there was no multiorgan involvement.
The pulmonary involvement noted in our case report was probably the result of mild
pneumonia, cardiogenic oedema, and microthrombi in the pulmonary arteriolar bed, which—associated
with the finding of microthrombi in the kidney and the presence of virus in the cardiac
capillary endothelium—suggest a SARS-CoV-2-induced endothelial dysfunction that probably
involved several organs.
Whole-exome sequencing could not identify any inborn error of immunity in our patient.
It is still unclear which host factors could predispose children to MIS-C; further
investigation of potential genetic determinants is important to understand the pathogenesis
of this syndrome.
10
In conclusion, our pathological observations support the hypothesis that the direct
effect of SARS-CoV-2 infection on cardiac tissue was a major contributor to myocarditis
and heart failure in our patient. Hopefully, our findings could help to shed light
on the understanding of the complex interaction between SARS-CoV-2 infection, MIS-C,
and cardiac dysfunction in children and adolescents with COVID-19.
For the UCSC Genome Browser see http://genome.ucsc.edu