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Frontiers in Myocardia, 2015, Vol. 1, 85-103 85
* Corresponding Author Mara Rúbia N. Celes: Department of Pathology, Institute of Tropical Pathology and Public
Health, Federal University of Goias, 74605-050, Goiania, Goias, Brazil; Tel/Fax: +55 62 3209-6363; E-mail:
rubia.celes@gmail.com
Vasilios E. Papaioannou (Ed)
All rights reserved-© 2015 Bentham Science Publishers
CHAPTER 4
Septic Cardiomyopathy: A Distinct Histopatho-
logical Entity
Maria José Figueiredo1, Ana Caroline Silva de Freitas1, Érica Carolina
Campos2, Danilo Figueiredo Soave1, Simone Gusmão Ramos1, Mara Rúbia N.
Celes1,3,*
1 Department of Pathology, Faculty of Medicine of Ribeirao Preto, University of Sao Paulo,
Ribeirao Preto, SP, Brazil
2 Department of Physical Education and Physiotherapy, Clinical Hospital of Federal University of
Uberlandia, MG, Brazil
3 Department of Pathology, Institute of Tropical Pathology and Public Health, Federal University
of Goias, Goiania, GO, Brazil
Abstract: Sepsis is the leading cause of death in critical ill patients in intensive care
units around the world. Cardiac dysfunction is one of the major clinical manifestations
in septic patients (about 60%), with mortality rate of approximately 80%, while septic
patients without cardiovascular impairment present mortality rates around 20%.
However, cardiac involvement as an important contributing factor to the multiple organ
dysfunction in the sepsis syndrome, has been rejected. Principal mechanisms proposed
to explain the cardiac dysfunction in sepsis originates from functional abnormalities,
not from structural changes. In spite of the evolution of septic cardiomyopathy concept,
the study of structural change as an important component in the development of
myocardial dysfunction has been omitted in sepsis. In 2007, morphological analysis of
human heart samples obtained by autopsy reported cases of severe sepsis/septic shock
condition in patients submitted a longer periods of hospitalization. Septic patients
showed structural myocardial alterations classified as "inflammatory cardiomyopathy"
probably responsible for the myocardial depression induced by sepsis. Since then,
structural changes on cardiac dysfunction in sepsis/septic shock has been object of
several studies, experimental and clinical, aiming to improve the diagnosis and
treatment of this syndrome. In this chapter, will be presented results of studies
conducted in our laboratory analyzing cellular and molecular mechanisms underlying
sepsis/septic shock, which may result in morphological alterations in the myocardium
of mice subjected to CLP-sepsis model.
Keywords: Cardiac structural changes, Dystrophin-glycoprotein complex (DGC),
Experimental sepsis model, Myocardial depression, Sepsis, Septic cardiomyopathy.
86 Frontiers in Myocardia, Vol. 1 Figueiredo et al.
1. INTRODUCTION
Sepsis, described as a complex clinical syndrome resulting from hyperactivation of the
immune response to exposure a deleterious or harmful agents in response to infection.
Clinical signs include fever, altered mental status, hypotension, oliguria and coagulation
disorders that could develop irresponsible hypotension and organs dysfunction (severe
sepsis/septic shock) [1].
In the United States, an estimated 750,000 patients develop severe sepsis with mortality
rate around about 230,000 deaths per year and, this condition has been considered as the
third most common cause of death in this country after cardiac disease and cancer [2]
Additionally, the financial costs associated to this syndrome are approximately $24.3
billion to the healthcare system [3 - 5].
Heart is one of most important organs affected during severe sepsis/septic shock and
myocardial dysfunction is observed in approximately 50% of diagnosed patients [6]. The
correlation between severe sepsis/septic shock and myocardial dysfunction elevates the
patients’ susceptibility to death when compared with those without heart dysfunction
[7].This chapter discusses the potential mechanisms responsible for the evolution of
septic cardiomyopathy highlighting myocardial structural changes in the heart of septic
patients and animals subjected to sepsis induced by cecal ligation and puncture (CLP)
with a discussion of experimental model.
2. SEPTIC CARDIOMYOPATHY
The concept of septic cardiomyopathy has evolved over the years which imply changes in
the myocardium physical composition [8]. The most important mechanisms proposed to
explain the pathophysiology of cardiac dysfunction in severe sepsis give more emphasis
on functional changes rather than anatomical abnormalities such as [9]: (i) Autonomic
deregulation. In accordance with some authors, during severe sepsis apoptosis of
cardiovascular autonomic centers could lead to autonomic failure that precedes the onset
of septic shock [10 - 12]. In the central nervous system, neuronal and glial apoptosis in
the cardiovascular modulator centers could be related to inflammatory response, mainly
mediated by inducible nitric oxide synthase (iNOS) [13]. Peripherally, increased levels of
IL-6 [14], plasma free fatty acids [15], and constant block of the sinus node [16] occurs in
addition to uncoupling of cells responsible for heart rate from cholinergic neural control
during sepsis [17]; (ii) Microvascular dysfunction. Severe sepsis is associated with
impaired microvascular oxygen transport [18] maldistribution of coronary circulation,
increased resistance of coronary vessels with vascular hyporesponsiveness to vasodilators
[19], and neutrophil emigration to the interstitial space [20]; (iii) Metabolic disorders.
During sepsis, the occurrence of metabolic changes due to accumulation of lipids in
cardiomyocytes as well as glycogen in non-survivors [21] has been proposed. One of the
Histopathological Changes in Severe Sepsis/Septic Shock Frontiers in Myocardia, Vol. 1 87
clinical signs of sepsis is the hyperlactatemia, hearts of septic patients showed a reduced
lactate withdrawal [22] associated with reduced myocardial glucose uptake, free fatty
acids and ketone bodies [23]; (iv) Mitochondrial dysfunction. Alterations in
mitochondrial function have been strongly associated with increased mortality rate in
septic patients. Multiple mechanisms, including changes in mitochondrial energy
metabolism, mitochondrial toxins and triggered caspase activation can result in impaired
organ and systemic failure resulting in death [24]; (v) Nitric Oxide and peroxynitrite
pathways. Overproduction of nitric oxide (NO) with subsequent development of local
oxidative stress has been proposed to be one of the significant pathophysiological
mechanisms for sepsis by exerting a negative inotropic and chronotropic effects on the
heart [25]. Increased production of NO, as a result of iNOS induction, by enzymatic
ligation causes cell injury by stimulating macrophages and neutrophils along with
mitochondrial inhibition by direct or by means of free radicals resulting in the
peroxynitrite formation causing further cellular damage [26]. Peroxynitrite generated can
exert cardiodepressant effects through the prevention of cardiomyocytes contraction even
in the presence of high levels of calcium (Ca+2) [27] leading to mitochondrial respiratory
chain dysfunction [28]; (vi) Inflammatory cytokines. There are many potential
inflammatory mediators that contribute to myocardial depression in sepsis; besides, the
most important cytokine mediators involved are TNF-α and IL-1β. Their cardiovascular
effects include hypotension, increased cardiac output and low systemic vascular
resistance [25, 29]; (vii) Cardiac cell apoptosis. Accumulated evidences have
demonstrated that cardiomyocyte apoptosis is involved in the pathogenesis of sepsis-
related myocardial depression [30, 31]. Cardiac cell apoptosis in sepsis is initiated mostly
through death receptors, caspases and mitochondrial pathway and, can be evidenced by
enhanced cell vacuolation, TUNEL assay, and activation of NF-κB in the myocardium
[32, 33]; and (viii) Intracellular calcium disorders. Alterations of calcium homeostasis
during sepsis are related to calcium behavior, i.e., intracellular handling, calcium influx,
and myofilament calcium sensitivity. The troponin I phosphorylation, at the site where
the calcium ion normally combines to the Troponin Complex [34], the reduction of
cytosolic calcium levels due to diminished calcium release from sarcoplasmic reticulum
via reduced density of ryanodine receptor type 2 (RyR2) [35] and the suppression of L-
type calcium channel in cardiomyocytes in the hyperdynamic stage of septic shock [36],
may be involved in this reduced ability of calcium to activate the cardiac myofilaments.
Over the years, despite of understanding the septic cardiomyopathy evolution [8, 37 - 42]
with phenotypic changes caused by a wide variety of agents acting on the cardiac cells,
the importance of structural changes of the septic myocardium has been left at second
place.
Treatments aimed at reducing mortality of patients with sepsis, severe sepsis and septic
shock through the manipulation of functional alterations have provided limited success in
early stages of sepsis [43]. It is known that the volume overload is associated with an
88 Frontiers in Myocardia, Vol. 1 Figueiredo et al.
increased risk of mortality [44, 45], also Ognibene et al., showed that the over adminis-
tration of volume was unable to restore ventricular function during the early stages of
sepsis and that also vasopressor therapy has not had positive or negative effects during or
after volume therapy [46]. A potential explanation for this unsuccessful may be structural
changes in the septic heart can favor this aggravation of septic syndrome [42].
2.1. Cardiac Structural Changes in Human Sepsis
Cardiac depression observed in severe sepsis/septic shock is considered one of the
leading causes of death in ill critically septic patients. In spite of this, it remains to be
proved whether the functional changes that affect the myocardium of septic patients are
due to structural changes, once the elevated serum levels of troponin T and I, found in
septic patients, were not associated with clinically recognized heart injury. Although,
increased cardiac troponins levels are indicative of myocardial injury, these increase do
not explain the injury cause. Probably, the origin of troponin elevation during sepsis
include diffuse necrosis, cardiac troponin I degradation or troponin cell release after
partial disruption of the plasma membrane [47].
There are few studies aimed to explain the correlation between structural changes of the
septic human myocardium and pathophysiology of septic injury. Moon et al., (1948)
reported indeterminate myocardial changes after analysis of ten cases of death correlated
to infection [48]. Almost 50 years later, analysis of 71 autopsies of septic patients
separated by morphological changes such as inflammatory responses in two organs or
more; bacterial acute pyelonephritis; acute liver and glomeruli inflammation; presence of
fibrin/thrombin, and neutrophils accumulation in the lungs were described. Nineteen of
cases presented acute myocarditis associated with neutrophilic infiltration in the
interstitium and occasionally abscess formation was observed, focal myocardial necrosis
was observed in 5 cases, and bacterial colonization was found in 8 cases. As controls in
this study, were used 71 patients matched by sex which death was not caused by
infections [49]. The main description of the authors comprise the occurrence of acute
bacterial myocarditis, being proposed by them that the main cause of tissue cardiac
damage and consequent myocardial depression would be the presence of mediators
carried by blood.
Currently, it has been proposed that cellular and molecular mechanisms could be
responsible for structural changes in human heart during severe sepsis [21, 50]. Analysis
of human heart samples, obtained by autopsy, reported cases of severe sepsis/septic shock
condition associated with acute lung inflammation that causes disruption of the lung
endothelial and epithelial barriers in patients with approximately 59 years and submitted a
longer hospitalization time (approximately 24.3 days). The most important results
documented by the morphological analysis in septic heart of patients were structural
myocardial alterations classified as inflammatory cardiomyopathy [51].
Histopathological Changes in Severe Sepsis/Septic Shock Frontiers in Myocardia, Vol. 1 89
Additionally, study performed in our laboratory, attempted to correlate the cellular
mechanisms caused by severe sepsis/septic shock with production of structural changes in
septic human myocardium demonstrated increased number of activated macrophages,
smooth muscle and endothelial cells, elevated diffused expression of TNF-α, cardiac
cytoplasmic lipid accumulation, and increased levels of iNOS and nitrotyrosine as
compared to control patients [21]. Macrophages can cause contractile failure during
induced endotoxemia in rats through activation of TNF-α via TNFR-I and TNFR-II
receptor [52]. Also, TNF-α is considered a potent cytokine that through interaction with
calcium can lead to cardiac dysfunction and cardiomyocyte death. [53]. In addition, a
cytoplasmic lipid accumulation was observed in the heart of septic patients reflecting a
possible myocardial dysfunction. During heart failure, muscle changes also affect the
energetic metabolism, i.e. free fatty acids typically used as an energy source are replaced
by glucose which results in an imbalance between the intake and absorption of fatty acids
and consequently lipid accumulation in cardiomyocytes [54]. Further, raised expression
of iNOS and nitrotyrosine (a biomarker of peroxynitrite formation) were observed in
cardiomyocytes of severe septic patients. Moreover, these results were associated with
focal rupture of actin-myosin interactions, proposing that oxidative lesions could
represent important role in the destabilization of the actin-myosin in septic hearts [21,
55].
In summary, these structural changes experienced in the humans myocardium and,
classified as "inflammatory cardiomyopathy" according to the Task Force on the
Definition and Classification of Cardiomyopathies of the World Health Organi-
zation/International Society and Federation of Cardiology [51], could be responsible for
sepsis-induced myocardial depression; however, this concept is evolving.
2.2. Cardiac Structural Changes in Experimental Severe Sepsis
At the same time, studies performed by our research group analyzed the cellular and
molecular mechanisms dependents on sepsis and septic shock, which may result in
morphological alterations in the myocardium of mice subjected to CLP model. Firstly, we
demonstrated significant alterations in the intercalated disks components, reduction of
adherens junctions [N-cadherin] and gap junctions [Connexin-43], proteins that are
considered essential to preservation of myocardium structural integrity through the
connections between cardiac cells [40]. According to Perriard et al., (2003) the rupture of
constituent proteins of intercalated disc could cause heart disease and other potentially
lethal injuries [41]. Thus, our results indicate that modifications in cell-cell
communication and mechanical linkage between neighboring cardiomyocytes occurred in
experimental sepsis and contributed to myocardial depression (Fig. 1).
90 Frontiers in Myocardia, Vol. 1 Figueiredo et al.
Fig. (1). Representative immunofluorescent staining for connexin43, Dystrophin and Actin (phalloidin). The
immunofluorescent signal for connexin43 and Dystrophin are markedly reduced in myocardium of severe
septic mice (left, bottom immunohistochemical panel) in comparison with the immunofluorescent signal in
sham-operated myocardium (left, top immunohistochemical panel). Original magnification, 400x.
Secondly, presence of spread foci of cardiomyocyte lysis associated with focal points of
contractile apparatus disruption (actin and myosin) was demonstrated in heart of septic
animals (Fig. 2). Moreover, detection of intracellular albumin evidencing the increased
permeability of sarcolemma in septic hearts occurred in conjunction lipid peroxidation
that causes direct damage to cell membranes and nitration of cardiac proteins. [56].
Sarcolemmal integrity is maintained through the structural proteins in cardiomyocytes
such as cytoskeletal proteins (tubulin, actin and desmin), proteins of contractile apparatus
(actin, myosin, troponin and tropomyosin) and sarcomeric skeleton proteins (titin and α-
actinin) [57]. Additionally, there are other structural proteins that contribute to cellular
form, mechanical strength and signal transduction in cardiac myocytes which allows
interactions among intracellular cytoskeleton, contractile apparatus and extracellular
matrix conferring structural stability to the cardiomyocyte membrane called dystrophin-
glycoprotein complex (DGC) [58].
The main finding demonstrated by our group was a significant loss/reduction of major
DGC components, dystrophin and β-dystroglican, implicated in the mechanical binding
between the entire arrays of myofibrils to the extracellular matrix. These changes
occurred in association with myofilamentar degeneration and lysis of cardiomyocytes.
Dystrophin disruption was considerate a primary event that occurs followed by
myofilamentar degeneration and lysis of cardiomyocytes. β-dystroglycan and laminin
decreased expression were considered a secondary event [55]. Moreover, sarcolemmal
and myofilamentar damage associated with lipid peroxidation and protein nitration
suggest deterioration of the DGC-complex in cardiomyocytes that may be involved in the
pathogenesis of cardiac dysfunction (Fig. 3).
Histopathological Changes in Severe Sepsis/Septic Shock Frontiers in Myocardia, Vol. 1 91
Fig. (2). Myocardium of mice submitted to severe septic stimulus presents spread foci of myocytolysis
(arrows) and tumefaction of cardiac cells compared with sham-operated myocardium, 24 h after CLP-surgery.
In upper and middle panel, Hematoxylin-eosin and phosphotungstic acid hematoxylin (PTAH) staining,
respectively. The Plastic-embedded material using methyl-methacrylate stained with toluidine blue (bottom
panel) resulted in better morphological detail, with little shrinkage cardiac cells. Original magnification,
400x.
Finally, our recent and important results published [59] using CLP-model showed that:
First, severe sepsis can induce high levels of calpain-1, a calcium-activated, non-
lysosomal cysteine protease, in cardiomyocytes associated with reduced dystrophin
expression and partial disruption of contractile proteins (actin and myosin) in the septic
92 Frontiers in Myocardia, Vol. 1 Figueiredo et al.
Fig. (3). Schematic diagrams illustrating the mechanism of how intercalated disc and dystrophin-glycoprotein
complex can affect cardiac remodeling in septic hearts. N-cadherin of the adherens junction, represented by
green bars, connects to form a strong zipper structure critical to cell-to-cell adhesion in myocardium of
control mice. In the septic myocardium, decreased expression of N-cadherin (missing N-cadherin represented
by gray bars) promotes a weak zipper structure arrangement (upper left illustration). Connexin43
polypeptides (represented in brown) oligomerize to form a hemichannel in the cell membrane establishing a
functional gap junction channel (connexon) in the myocardium of control mice. In the septic myocardium,
decreased expression of connexin43 lead to dehiscence of the gap junction formation schematically
represented in gray (upper right illustration). In addition, in normal myocardium, Dystrophin connects to the
extracellular matrix through the links of actin to the transmembrane proteins dystroglycan and sarcoglycan
and, dystroglycan binds to the extracellular matrix through laminin (bottom left panel). In septic myocardium,
reduction/loss of dystrophin can result in rupture of the mechanical linkage between actin-based
subsarcolemmal cytoskeleton and sarcolemma to the extracellular matrix that may compromise contractile
force transmission (bottom right panel).
Histopathological Changes in Severe Sepsis/Septic Shock Frontiers in Myocardia, Vol. 1 93
myocardium. Second, treatment of septic mice with calcium blocking drugs, both vera-
pamil (a drug that selectively inhibits the influx of calcium through the slow channel (L-
type channel)) and dantrolene (a classical inhibitor of calcium release from the
sarcoplasmic reticulum through the ryanodine receptor type-2 (RyR-2)) inhibited the
increase in cardiac levels of calpain-1 and prevented proteolysis of dystrophin, actin and
myosin in myocardium of animals with severe sepsis; Third, increased cardiac levels of
TNF-α, observed in mice submitted to severe sepsis without treatment, were reduced in
septic mice treated with calcium channel blockers; Fourth, heart function parameters
assessed by echocardiography 24 hours after CLP surgery showed that experimental
sepsis induced cardiac dysfunction characterized by reduction of ejection fraction,
fractional shortening and cardiac output as compared to control mice. On the other hand,
after treatment with calcium blockers verapamil or dantrolene the septic mice completely
recovery cardiac function (EF, FS and CO).
Together, these studies represent an advance in the characterization of septic cardio-
myopathy in acute phase experimental animals with possibility of translational
application. Particularly, experimental studies could represent an example of "Trans-
lational Research" to the extent the evaluations in human allowed observations that led to
the experimental studies revealing important molecular mechanisms involved in the
development of cardiac depression. In this context, our most recent results represent a
significant advance in the understanding of the pathophysiology of cardiac dysfunction in
experimental severe sepsis with opportunity to complete the circle - from the bedside to
the bench and from bench to the bedside. Evidently, there is a long distance between
laboratory benches to clinic, since CLP model does not fully mimic clinical condition of
humans’ sepsis.
2.3. The Question of Experimental Sepsis Model
Over the years, many research groups developed different experimental models of sepsis
in an attempt to promote appropriate analogy to the human form of sepsis. This screening
has been based mainly in models such as: 1) challenge with endotoxin (LPS) from Gram
negative bacteria or exotoxin of Gram positive bacteria [60]; 2) intraperitoneal or
intravenous administration of live organisms [61, 62]; and, 3) models that disrupt the
endogenous intestinal barrier [63, 64]. During sepsis/septic shock it is well known that
the input of bacteria or LPS in the blood circulation is small, increasing the question if
these models indeed represent the septic condition. The colon ascendens stent peritonitis
(CASP) and CLP are examples of models that disturb the endogenous intestinal barrier.
Furthermore, another model that mimics sepsis, induced by intraperitoneal administration
of feces, is the fecal pellet model [65] that in many respects resembles CLP and CASP,
however it is hardly used. In the CASP model a short stent is added into the ascending
colon of animals carrying a continuous extravasation of enteric bacteria in the peritoneal
cavity promoting polymicrobial septic peritonitis [66]. The severity of this model may be
94 Frontiers in Myocardia, Vol. 1 Figueiredo et al.
controlled by diameter from inserted stent. Although the model mimics the clinical course
of abdominal sepsis, the nature of the model limits its use. The CASP is a relatively
newer model than the CLP; however, this surgical procedure is more difficult than the
CLP.
CLP model was proposed in 1980 by Wichterman et al. [63] and up to now this sepsis
model is regarded the most lifelike condition by drawing a comparison between the
clinical and experimental situations [67]. In summary, in this model there is a gradual
release of colonic contents into the peritoneal cavity causing acute peritonitis, which can
evolve into sepsis and septic shock. Moreover, it is possible to standardize different
degrees of intensity and course of infection using different number of punctures and
gauge of the needle used [67]. Great attention is given to CLP model since has been
substantially studied in the past 35 years and has contributed to knowledge of many
pathophysiologic and immunologic characteristics of sepsis and, therefore regarded as the
gold standard sepsis model. Meantime, experimental models of sepsis do not fully
reproduce all the complexity of clinical situation.
Septic patients represent a highly heterogeneous population presenting large variations in
clinical course of disease including severity, source of infection, comorbidities, and time
of hospital admission [68]. On the other hand, preclinical animal experiments may be too
simplistic due to animal conditions; usually, the animals are young and have no comor-
bidities. Opposed to experimental designs, the human sepsis/septic shock frequently
affect elderly patients with associated comorbidities, which are strong predictors of
susceptibility and result to sepsis. In addition, supportive care and antibiotics are not
often given in animal models [69].
Certainly, CLP model has been contributed to the basic understanding of the involvement
of immune system in sepsis including identifying of potential new targets for the
development of therapeutic strategies; great attention should be given when effective
results of new therapeutical agents are extrapolated from experimental models to humans.
This has become clear when the majority of promising therapeutic approaches suggested
by experimental studies do not had satisfactory results regarding to improvement of
survival rate in septic patients [70 - 72]. One of major problems regarding the effective
strategies for treatment of sepsis implies in the host immune response changes with the
progression of the disease [73 - 75]. Early deaths in sepsis usually are result of an
exacerbated inflammatory response and, the survivors from initial state evolve to an
immunosuppressive period [76, 77] predisposing the host to development of several
nosocomial infections [78], particularly gram-negative bacterial pneumonia [79, 80]. A
recent published study, asserted that patients who died due to sepsis in the ICUs, as
compared to those who did not died from septic causes, presented biochemical, flow
cytometric and immunohistochemical findings consistent with immunosuppression [81].
Histopathological Changes in Severe Sepsis/Septic Shock Frontiers in Myocardia, Vol. 1 95
Currently, the "treatment" of septic patients is largely supportive focusing on adminis-
tration of wide-spectrum antibiotics designed to eliminate the infectious site and
hemodynamic support requiring the use of fluid, vasopressors and inotropes. Based on the
assumption that in sepsis there is a deregulation of the immune system, new therapeutical
approaches have given particular emphasis in suppressing the inflammatory response in
order to reduce the levels of coagulation factors, cytokines and complement system.
Though, translation of therapeutic strategies derived from animals to man, focused on an
exacerbated inflammatory response have not been successful, probably at least partly
because of the fact that animals models of sepsis not reproduce the complex nature of real
human septic syndrome [71]. For example, the use of therapies with monoclonal anti-
TNF in experimental models of bacteremia and endotoxemia demonstrated increased
survival of treated animals, whereas clinical studies in septic patients failed to show any
advantage from this treatment. Likewise, administration of the antagonist of the IL-1
receptor in experimental models of sepsis showed an improvement in survival of treated
animals. In the meantime, clinical trials using the same therapeutical intervention did not
improve the survival rate of severe sepsis patients. Likewise, numerous experiments in
diverse models of endotoxemia have shown the beneficial effects of systemic use of
corticosteroids with increased survival of the animals, while randomized clinical trials in
septic patients undergoing corticotherapy not resulted in improved survival rates. The use
of anti-Toll-like receptors (TLR4) reduced the cytokine expression and markedly
improved survival in mice subjected to endotoxin shock and sepsis induced by E. coli.
Furthermore, TLR4 knockout mice have been completely resistant to septic shock
induced by E. coli; in contrast, the use of a compound anti-TLR4, completely failed to
improve mortality in septic patients compared with placebo in the third phase of a
randomized trial worldwide. In addition, activated protein C, with anticoagulant and
fibrinolytic properties and anti-apoptotic, anti-inflammatory and anti-histone activities,
have failed to confirm its clinical efficacy in randomized controlled trials on a global
scale PROWESS Shock [69, 72, 82].
2.4. The Question of Experimental Sepsis Model - Mimicking Clinical Reality
There are over 300 years Isaac Newton asserted that “Errors are not in the art but in the
artificers” [83]. In 1996, Bone reminded us: “We must always be willing to revise our
models as new information becomes available to admit when our explanations are
incomplete and consider new explanations for the same data. We should spend more time
learning how to achieve an accurate diagnosis and less time searching for a magic bullet”
[84]. Recently, Deutschman (2013) advised us: “Einstein is reputed to have stated that
insanity is performing the same experiment again and again in the hope of getting a
different result. We should consider this statement whenever we explored new
approaches to the treatment of sepsis” [85].
96 Frontiers in Myocardia, Vol. 1 Figueiredo et al.
Thus, the understanding of both phase pro- and anti-inflammatory in human sepsis
requires animal models where the hyperinflammatory response can go beyond allowing
the host defense study for a prolonged phase of sepsis [71]. Therefore, in attempt to
mimic human severe sepsis/septic shock long-term observed in UCI patients, several
research groups have modified the CLP model: animals subjected to CLP surgery and
challenged with Aspergillus fumigatus [86] or Candida albicans fungi [87], or
Pseudomonas aeruginosa, Streptococcus pneumoniae [88] or Staphylococcus aureus
bacterium [89]; and animals subjected to trauma/hemorrhage followed by CLP surgery
[90 - 91]. Consequently, the double-injury (two-hit) would provide a useful tool in the
study of sepsis creating a prolonged infection period, in opposite to acute phase,
approximately 24 hours, of infection induced by CLP.
Given this, the current considerations of sepsis focused on agents that block or suppress
the exacerbated inflammatory response (not always present in all patients), would be
responsible, at least in part, by the solution of the problem in this syndrome. Although
septic patients die due to multiple organ failure, the intrinsic pathogenic mechanism of
each organ dysfunction has been relegated to a secondary plane. The consensus is that
hypoperfusion and hypoxia play important roles. General proposed mechanism for organ
failure include: microcirculatory alterations, secondary alterations to thrombus formation
or changes in the rheology of erythrocytes, interstitial edema caused by increased capillar
permeability, reduction of perfusion pressure, mitochondrial dysfunction, vasoplegia and,
tissue injury caused by neutrophil infiltration with release of lysosomal enzymes and
burst oxidative. Multiple Organ Dysfunction Syndrome (MODS) may occur as a result of
a primary infection or after complications caused by nosocomial infections, and for many
patients, the management of this syndrome does not increase survival but prolongs the
dying process.
In summary, the basic requirements for the best design of a translational medicine
request: a) a suitable model mimicking the complex picture of human septic syndrome; b)
a better description and methodological standardization between laboratories and; c)
development of a "slow science" with the main objective: The understanding of the basic
mechanisms involved in this syndrome.
Despite of numerous controversies that move the septic scenario, critical questions
remain unanswered: 1) What causes the myocardial dysfunction? 2) What is the
pathophysiology of heart dysfunction and death? 3) Is there something that could be
made to avoid the outcome? A more coherent approach is essential for the understanding
of the septic pathogenesis and organ dysfunction. Thus, the conjunction of these facts
could lead to development of new therapeutic strategies in an attempt to reduce the high
mortality rate induced by severe sepsis/septic shock.
Histopathological Changes in Severe Sepsis/Septic Shock Frontiers in Myocardia, Vol. 1 97
CONFLICT OF INTEREST
The authors confirm that this chapter has no conflict of interest.
ACKNOWLEDGEMENTS
This work was supported by grants from Fundação de Amparo à Pesquisa do Estado de
São Paulo, FAPESP (04/01777-0, 04/14578-5, 11/23220-0, 11/08234-5, 11/18427-5),
Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPq (470536/2008-0
and 303308/2013-3) and by a Fogarty International Training Grant (D43-TW007129).
Celes, MR. is Investigator (2A) of CNPq and Rossi, MA. (in memoriam) was Senior
Investigator (1A) of CNPq.
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