Keywords
atria - COVID19 - fibrillation - pathology - stroke
Introduction
Cytokine release syndrome (CRS) is a well-described pathological state which may occur
after therapy with genetically modified T-cells.[1] In general, CRS is characterized by elevation of several biomarkers such as interleukin
(IL)-6, IL-1, and tumor necrosis factor (TNF)-α. Furthermore, ferritin, D-dimer, and
C-reactive protein (CRP) are elevated. Clinically, CRS causes fever, nausea, tachypnea,
and mental status changes. In more severe forms, CRS is associated with mechanical
ventilation, hypotension requiring vasopressor therapy, organ dysfunction, and shock.
In addition to cancer therapy, diseases like viral infections have been described
to trigger a release of cytokines.[2]
[3]
[4] The novel coronavirus Disease 2019 (COVID-19) is a viral disease induced by severe
acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) that may cause an acute respiratory
distress syndrome (ARDS). At present, the role of CRS in COVID-19 and COVID-19-induced
ARDS is not fully understood.[1]
[5]
[6] In the present case, we can correlate the clinical course of a COVID-19 patient
with systemic biomarkers and histopathological results.
Case Presentation
We report on a 53-year-old male patient with a positive polymerase chain reaction
(PCR) nasal swap for SARS-CoV-2, who was hospitalized due to high-grade fever and
bilateral lung infiltrates ([Fig. 1]). Due to rapid deterioration of respiration and development of ARDS, mechanical
ventilation of the patient was initiated. On admission to intensive care unit (ICU),
the patients also developed atrial fibrillation (AF), which had never been recorded
before in this patient ([Fig. 2]). Due to rapid ventricular rates during AF, the patient was electrically cardioverted
and placed on amiodarone intravenous (IV). Anticoagulation was initiated with unfractionated
heparin IV with partial thromboplastin time at approximately 50 seconds. Venovenous
hemofiltration was initiated because of acute kidney failure with anuria. Even after
prone positioning and relaxation, gas exchange deteriorated. Lowest pH was 6.93 with
a CO2 of 112. Of note, IL-6 reached a maximum level of 2,039 pg/mL (normal value: 0–7 pg/mL),
D-dimer was >35 mg/d: (0–5 mg/dL), fibrinogen maxed at 817 mg/dL (170–420 mg/dL),
CRP at 38.66 mg/dL (0–0.5 mg/dL), ferritin 3,920 ng/mL (30–400 ng/mL), procalcitonin
at 5.47 ng/mL (0–0.5 ng/mL), lactate dehydrogenase reached 1,190 U/L (135–225 U/L),
von Willebrand factor (vWF) (FVIII:C)-Activity was 306% (coagulation), vWF-Activity
was 447% (turbidimetry), and vWF Antigen was 447% (turbidimetry). Angiotensin II levels
were >150 ng/mL (20–40 ng/mL), angiotensin converting enzyme (ACE) decreased to 11
U/L (20–70 U/L), ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin
type 1 motif, member 13) protease activity was reduced to 47%. The patient's blood
group was A Rhesus factor positive. Antipospholipid antibodies could not be detected,
homocysteine levels were normal with 5.8 µmol/L, and serial heparin-induced thrombocytopenia
(HIT) screening tests were negative. At this point, CRS was diagnosed.[5]
[6] After initiation of 70 mg/day prednisolone, the patients gradually improved. At
day 7, a puncture tracheotomy was performed. The procedure was uneventful. But 48 hours
later, the patients developed a sinus node arrest with asystole of >15 seconds ([Fig. 3]). Left ventricular function was not compromised with a normal ejection fraction
on echocardiography. A temporary pacemaker wire was inserted through the left jugular
vein after two more episodes of sinus node arrest for >10 seconds. On day 11, a computed
tomography (CT) scan of the brain and chest revealed that the patient had suffered
multiple pulmonary embolisms ([Fig. 4A]) and multiple thromboembolic strokes of which the largest was in the right posterior
hemisphere ([Fig. 4B]). Due to repetitive episodes of sinus node arrest, a permanent pacemaker was consecutively
implanted. Twenty-four hours after pacemaker implantation, the patient developed a
fatal hemorrhagic shock due to a massive pulmonary bleeding. Autopsy confirmed a severe
form of SARS–CoV-2 induced ARDS ([Fig. 5A]). Of note, total lung weight was 3 kg. Immunohistochemistry revealed local overexpression
of IL-6 ([Fig. 5B]) and MCP-1 ([Fig. 5C]) in pulmonary macrophages and alveolar epithelial cells type II. Furthermore, arterial
endothelial damage, necrosis, fibrinous exsudation, and inflammatory infiltrates of
the intimal layer were present, that is, in the left carotid artery ([Fig. 5C]). Atypical locations of thrombus formation included a pulmonary vein of the right
lung ([Fig. 5D]) and the right atrial appendage. Histologically, not only subendothelial vascular
walls but also atrial walls were invaded by inflammatory cells. Interestingly, IL-6
overexpression could be found within vascular thrombi, adherent endothelial cells,
and fibroblasts ([Fig. 6A]). In the right atrium signs of inflammatory microangiopathy (“small vessel disease,”
[Fig. 6B]) in conjunction with mild lymphocytic myocarditis and early myocardial necroses
were present ([Fig. 6C]). Interestingly, as a possible cause for AF and sinus node dysfunction, histological
examination also revealed that ganglionated right atrial plexi were infiltrated by
lymphocytes and virus-infected ganglial cells could be observed ([Fig. 6D]). In the kidneys a glomerulonephritis with cytopathogenic effect of the podocytes,
tubular epithelial necroses with cytopathogenic effect of tubular cells ([Fig. 7A, B]) and interstitial nephritis could also be detected ([Fig. 7C]). Furthermore, involvement of the liver was also shown by overexpression of MCP-1
in Kupffer's cells ([Fig. 7D]).
Fig. 1 Extensive bilateral lung infiltrates (blue arrows) associated with SARS-CoV-2 infection
typical for corona-associated adult respiratory distress syndrome. SARS-CoV-2, severe
acute respiratory syndrome–coronavirus-2.
Fig. 2 Atrial fibrillation with tachycardic conduction to the ventricles (electrocardiograms
both upper rows) as a possible sign for atrial cardiomyopathy. Peripheral pulse deficit
as depicted in the arterial pressure measurement due to an increased heart rate of
around 190 beats per minute (bpm) with a peripheral pulse deficit (163 bpm; both lower
rows).
Fig. 3 Intermittent sinus node arrest with asystole of >15 seconds (blue arrow).
Fig. 4 (A) Pulmonary CT scan depicting one of several pulmonal arterial thrombi (right pulmonary
subsegment artery, blue arrow). (B) Cerebral CT scan with evidence of a subacute right posterior territorial ischemic
lesion (red arrow). CT, computer tomography.
Fig. 5 (A) Lung tissue with IL-6 expression (brown colored stain) of plasma cells and alveolar
macrophages (pneumocytes II, IL-6, Zytomed), ×80 magnification. (B) Lung tissue with MCP-1 expression (brown colored stain) in alveolar macrophages
(pneumocytes II) and intra-alveolar fibrin (MCP-1, Santa Cruz), ×40 magnification.
(C) The novel coronavirus disease (COVID-19) lung with activated intra-alveolar pneumocytes
type II, some with virally altered multiple nuclei (blue arrow), H&E, ×20 magnification.
(D) Left arteria carotis communis with endothelial damage (yellow arrow), necroses,
fibrinous exsudation and inflammatory infiltrates of the intimal layer (green arrow),
H&E, ×40 magnification. (E) COVID-19 lung. Early fibrin rich thrombus in a right sided pulmonary vein (red arrow)
as a possible atypical origin of thromboembolic stroke, H&E, ×20 magnification. H&E,
hematoxylin and eosin; IL, interleukin; MCP, monocyte chemoattractant protein.
Fig. 6 (A) Thrombus in organization with IL-6-expression (brown colored stain) of endothelial
cells, Fibroblasts and macrophages (IL-6, Zytomed, ×40 magnification). (B) Right atrium, stenosing microangiopathy “small vessel disease” (blue arrow), Elastika-van-Gieson
(EvG), ×20 magnification. (C) Right atrium, fresh myocardial necroses (green arrows), H&E, ×40 magnification.
(D) Right atrium, nerval ganglion cells with lymphocyte infiltration (yellow arrow)
and viral alterations (red arrow), H&E, ×40 magnification. H&E, hematoxylin and eosin;
IL, interleukin.
Fig. 7 (A) Kidney, viral glomerulonephritis (blue arrow) with cytopathogenic effect of podocytes
(yellow arrow), H&E, ×40 magnification. (B) Kidney, cytopathogenic effect of the tubular epithelial cells, periodic acid–Schiff
reaction (PAS), ×80 magnification. (C) Kidney, necroses of the tubular epithelium (green arrow), interstitial nephritis
(red arrow), H&E, ×40 magnification. (D) Liver with MCP-1 expression in Kuppfer's cells (dark brown colored stain), necroses
of hepatocytes (MCP-1, Santa Cruz), ×40 magnification. H&E, hematoxylin and eosin;
MCP, monocyte chemoattractant protein.
In summary, the present case shows that severe COVID-19 induces CRS associated with
ARDS, acute kidney failure, liver pathologies, vascular intimal inflammation, pulmonary
arterial, and venous thromboses and an inflammatory atrial cardiomyopathy. In particular,
the presence of unusual clot formation in the right atrial appendage, but also loosely
detached clots within the pulmonary venous system are novel findings, since the latter
might be a source of systemic stroke in COVID-19 patients. Of note, the venous clots
could not be detected by conventional contrast CT scans, which revealed the presence
of embolisms in the pulmonary artery in the presented patient.
ARDS and COVID-19
In COVID-19 patients with ARDS, there are inflammatory infiltrates of alveolar and
interstitial tissue, increased vascular permeability, as well as microcirculatory
flow abnormalities, due to thrombus formation within the capillaries.[7] ARDS appears to occur in 5 to 30% of COVID-19 patients.[8] A recent, to date only on preprint servers and not yet peer reviewed large scale
study with a genome-wide association analysis including 1,980 patients and 8,582,968
single-nucleotide polymorphisms identified blood group A Rhesus factor positive, the
blood group of our patient, as a risk marker for respiratory failure in COVID-19 patients.[9] Ellinghaus et al also found a protective effect for blood group O.[9]
Increased activation of the clotting system appears as one hallmark of COVID-19.[10] There is growing evidence for an impact of the activated coagulation factor X (FXa)
in inflammatory lung diseases.[11] A study investigated the effects of FXa on epithelial lung cells (A549 cell line).[12] Of note, FXa increases expression of cytokines in alveolar epithelial cells, which
can be prevented by an inhibitor of protease-activated receptor 1, vorapaxar. Interestingly,
the presented patient developed arterial and venous pulmonary microthrombi in the
circulatory tree and pulmonary bleeding due to increased capillary permeability. These
venous and arterial thrombotic vascular occlusions in the lungs were found despite
the constant use of effective heparin IV in the current case. Further studies are
warranted to assess the effect of FXa inhibitors to prevent clot formation in the
lungs of COVID-19 patients.
Activation of Clotting System in COVID-19
Activation of Clotting System in COVID-19
Viral infections, such as SARS-CoV-2, may induce systemic inflammatory pathways.[13] Activation of host immune systems can cause activation of the plasmatic clotting
system resulting in thrombogenesis called thromboinflammation or immunothrombosis.[14]
[15] Importantly thrombotic complications have been described in 5 to 23% of COVID-19
cases.[16] The clotting system can be activated by multiple procoagulant pathways. Activated
platelets, mast cells, and tissue factor or FXII may induce the intrinsic coagulation
pathway.[17] Cytokines may cause endothelial injury with endothelial and intimal necrosis and
expression of adhesion molecules, which might later on be associated with thrombocytopenia.[18]
[19] Subsequent decline in clotting factors occurs with enhanced fibrinolysis during
severe infections, which is also characterized by elevated D-dimers.[20] Activation of the clotting system with decline of clotting factors and thrombocytopenia
has been described to occur in patients in later stages of COVID-19.[20]
[21]
Massive systemic inflammation has been described in patients with SARS-CoV-2 infections.
This cytokine release syndrome (CRS) is characterized by elevated levels of IL-6,
increased CRP, ferritin, and elevated fibrinogen.[22] A report of COVID-19 patients in China found elevated plasma concentrations of inflammatory
markers in particular in patients with severe infections.[23] In COVID-19, elevated D-dimer levels have been associated with thromboembolism and
worse prognosis.[24]
[25]
[26] Tang et al showed elevated fibrinogen levels.[20] Another study found elevation of fibrinogen, D dimer, and IL-6 levels in patients
with COVID-19-induced ARDS.[11] In COVID-19 patients, 71.4% of nonsurvivors and 0.6% survivors met the criteria
of disseminated intravascular coagulation.[20]
Initial results have described antiphospholipid antibodies as a cause of coagulopathy
in some patients.[27] Unlike other RNA viruses inducing hemorrhagic manifestations (hemorrhagic fever
viruses), SARS-CoV-2 has not been reported to result in significant bleeding.[28] However, the present case showed fatal diffuse pulmonary bleeding, which is one
of the first descriptions that COVID-19 might cause substantial hemorrhagic manifestations
besides thrombogenesis in arteries, veins and as in our case in the heart.
Vascular Intimal Dysfunction in COVID-19
Vascular Intimal Dysfunction in COVID-19
Recent reports have shown the occurrence of an “endotheliopathy,”[29] which contributes to microcirculatory changes in SARS-CoV-2 infections.[30] The receptor for viral adhesion is the ACE-2 receptor, causing inflammatory cell
infiltration, endothelial cell apoptosis, and microvascular prothrombotic effects.[29] The ACE2 receptors are expressed in different organs like lung, heart, kidneys,
and endothelial cells. Thus, SARS-CoV-2 can effect endothelial cells in many different
organs via ACE2 binding. This finding is supported by the present case because we
found a generalized inflammation of the vascular endothelium but also the vascular
intima causing endothelial shedding, thrombus formation and diffuse bleeding, particularly
in the lungs. Recent reports suggest that viral inclusions within endothelial cells
and sequestered mononuclear and polymorphonuclear cellular infiltration might induce
endothelial apoptosis.[29] Nevertheless, CRS has been clearly described to cause massive endothelial dysfunction
and microcirculatory flow abnormalities associated with multiple clots within the
capillaries. As a result, microcirculatory dysfunction in solid organ may occur causing
organ failure in patients with COVID-19. In the present case, we can clearly show
that the intima of the carotid arteries is substantially invaded by inflammatory cells
causing necrosis of the intima and endothelial denudation. Of note, we can show overexpression
of cytokines in areas of vascular necrosis and thrombosis. Thus, the vascular alterations
are much more complex than isolated endothellopathy. Furthermore, we can show for
the very first time that the atrial tissue of the right atrium is affected by the
systemic inflammatory process as well. In the present case, we can show that COVID-19
can induce the occurrences of ARDS, which was associated with pulmonary embolism,
as well as thrombogenesis, in pulmonary veins and the right atrial appendage. Thus,
further studies are warranted to assess the use of antiplatelet therapy and/or oral
anticoagulant therapy in patients with this condition to prevent organ ischemia.
Inflammatory Atrial Cardiomyopathy
Inflammatory Atrial Cardiomyopathy
The term “atrial cardiomyopathy” has been introduced by a worldwide consensus document
in the year 2016.[31] Inflammatory changes of atrial tissue have been described in the presence of various
form of myocarditis or toxic agents. Here, we can describe for the first time that
COVID-19 induces an inflammatory atrial cardiomyopathy that caused sinus node dysfunction
and AF. In the present case, it remains unclear if AF was causally related to the
occurrence of stroke, since severe changes at the endothelium could be documented
in the carotid artery and thromboses were also found in the pulmonary veins and the
right atrial appendage. In contrast to the significant atrial alterations, histological
exam of left ventricular tissue showed only mild subendothelial scarring without significant
lymphocytic infiltration. Accordingly, left ventricular function was normal throughout
the course of hospitalization monitored by echocardiography. Studies have recently
described mild lymphocytic myocarditis and signs of epicarditis in the ventricles
of COVID-19 patients.[32] To our knowledge, however, the manifestation of COVID-19 in cardiac ganglionated
plexi with clinical manifestation of sick sinus syndrome has not been described before.
It remains unclear at this point if parts of right atrial clots may have contributed
to embolic events in the pulmonary arteries.
Mechanisms of Stroke in COVID-19
Mechanisms of Stroke in COVID-19
Several reports have shown an increased rate of pulmonary thromboembolic events, stroke,
and systemic embolism in COVID-19.[33] Neurologic manifestations might occur in up to 36%.[33] These events appear to be related to activation of the plasmatic clotting system,
platelet activation, and vascular intimal dysfunction or endothelial denudation causing
local thrombus formation and organ ischemia. The present case further suggests that
AF and the development of pulmonary vein thrombosis might also be additional factors
that may contribute to the development of stroke in COVID-19 patients. There are rare
reports on patients with pulmonary arteriovenous shunts, which might become clinically
apparent by repetitive cerebral strokes.[34] Thus, the pulmonary venous system might be the source of thrombus formation with
cerebral clot embolization. The present case also shows that COVID-19-induced ARDS
is associated with massive clotting in the pulmonary microcirculation. In addition,
clot formation may also occur in pulmonary veins, and therefore, pulmonary venous
clots might be a source for systemic embolism and stroke in COVID-19.
Novel Therapeutic Approaches in COVID-19
Novel Therapeutic Approaches in COVID-19
In the lack of an effective vaccine for preventing severe medical conditions associated
with SARS-CoV-2 infections ([Fig. 8]), several novel therapeutic approaches have been proposed, encompassing antivirals,
antimalarials, and immunomodulators that have shown activity against SARS-CoV-2.[35]
[36] In particular, hydroxychloroquine, remdesivir, interferon β-1b, lopinavir-ritonavir,
ribavirin, favipiravir, arbidol, tocilizumab, and bevacizumab have been investigated.[35] Mostly, however, these therapies have been evaluated in single cases or small-scale
studies. Remdesivir (Gilead Science), a nucleotide analogue prodrug that inhibits
viral RNA polymerases, was originally evaluated for treatment in Ebola Virus disease,
but it has also shown in vitro activity against SARS-CoV-2. Preliminary data show
that remdesivir may be beneficial in the early phase of SARS-CoV-2 infection.[37] Hung et al have recently evaluated a combined antiviral and imunomodulator therapy
with interferon β-1b, lopinavir-ritonavir, and ribavirin in a multicenter, open label,
randomized phase-IIb trial in COVID-19 patients.[38] The authors conclude that early treatment with the triple combination therapy may
successfully reduce viral shedding and hence hospitalization duration. Zhagn et al
reported on successfully treating a severely ill COVID-19 patient with dose adjustment
methylprednisolone according to inflammation parameters and T-cell count.[39] In our case, however, despite early initiation of corticosteroid therapy, the patient
developed a severe form of CRS with highly elevated IL-6 levels. Early reports show
that tocilizumab, an IL-6 inhibitor, may be beneficial in this patient population.[40]
[41]
[42] Furthermore, due to the observed alterations at the arterial, venous, and atrial
endothelium further studies are warranted to assess the optimal anticoagulative strategy
including different anticoagulants and potential combinations of anticoagulants with
antiplatelet drugs.
Fig. 8 Summary figure about cytokine release syndrome (CRS) in COVID-19. CRS is associated
adult respiratory stress syndrome (ARDS) of the lungs, vascular intimal inflammation
and coagulopathy with increased incidence of thromboembolic complications. COVID-19,
novel coronavirus disease 2019; CRS, cytokine release syndrome; MCP, monocyte chemoattractant
protein; SARS-CoV-2, severe acute respiratory syndrome–coronavirus-2.
Conclusion
COVID-19 is associated with development of CRS, which contributes to fatal damage
of solid organs. Massively increased IL-6 levels and MCP-1 appear a systemic blood
marker of CRS. In addition to COVID-19-induced ARDS, CRS might be associated with
pulmonary artery, as well as vein thromboses, atrial fibrillation, sinus node dysfunction,
right atrial clot formation, and inflammatory invasion of autonomic atrial nerve ganglia.
Furthermore, hepatitis and glomerulonephritis might occur at a very early stage of
the disease leading to acute organ failure within days of COVID-19 ([Fig. 8]). Studies are warranted to examine, if therapeutic agents against CRS-like IL-6
receptor antagonist tocilizumab and/or anticoagulants plus antiplatelet therapy are
useful to treat patients with severe COVID-19.
