New Observations Regarding Post-Ischemia/Reperfusion Myocardial Swelling

In vivo evaluation and molecular docking studies of Schinus molle L. fruit extract protective effect against isoproterenol-induced infarction in rats

The aim of the current study was to assess the potential cardiopreventive effect of the methanolic extract of S. molle L. (MESM) on isoproterenol-induced infarction in rats. The biomolecules content was evaluated using HPLC-DAD-ESI-QTOF-MS/MS analysis. On the 29th and 30th days, two successive injections of isoproterenol (ISO) were given to Wistar rats to provoke myocardial infarction following pretreatment with either MESM (60 mg/kg b.w) or Pidogrel (Pid; 2 mg/kg b.w.). A total of sixteen phenolics were identified with masazino-flavanone as the most prevalent compound (1726.12 µg/g dm). Results showed that MESM offered cardioprevention by normalizing the ST segment and reducing the elevated cardiac risk parameters. The altered lipid biomarkers together with the plasma ionic levels were improved. Additionally, MESM inhibited the cardiac oxidative stress generated by ISO injection though enhancing antioxidant enzymes (GSH, CAT, SOD and GPX) which reduced lipid peroxidation and protein oxidation. MESM reduced myocardial apoptosis by significantly repressing mRNA expressions of Caspase-3 and Bax, with an upregulated Bcl-2 expression. Moreover, MESM reduced DNA fragmentation as well as the infarct size observed by TTC staining. In addition, MESM exhibited an antifibrotic effect by downregulating TGF-1β expression and reducing collagen deposition in myocardial tissue, as confirmed by Trichrom Masson analysis. The histopathological findings revealed less muscle separation and fewer inflammatory cells in the ISO + MESM-treated rats. Results of the docking simulation indicated that catechin in MESM was inhibitory mainly due to hydrogen bonding interactions with PDI, ACE and TGF-β1 proteins which could highlight the antithrombotic and antifibrotic capacity of MESM.

A Novel Synthetized sulfonylhydrazone coumarin (E)-4-methyl-N'-(1-(3-oxo-3H-benzo[f]chromen-2- yl)ethylidene)benzenesulfonohydrazide Protect against Isoproterenol Induced Myocardial Infarction in Rats by attenuating Oxidative damage, Biological Changes, and Electrocardiogram

Coumarins and their derivatives are becoming a potential source for new drug discovery due to their vast array of biological activities. The present study was designed to investigate the cardioprotective effects of a newly synthesized coumarin, symbolized as 5,6-PhSHC, against cardiac remodeling process in isoproterenol (ISO) induced myocardial infarction (MI) in male Wistar rats by evaluating hematological, biochemical, and cardiac biomarkers. Rats were pre/co-treated with 5,6-PhSHC or clopidogrel (150 μg/kg body weight) daily for a period of 7 days and then MI was induced by injecting ISO (85 mg/kg body weight), at an interval of 24 hours for 2 consecutive days, on 6^th and 7^th days. The in vivo exploration indicated that the injection of 5,6-PhSHC improved the electrocardiographic (ECG) pattern and prevented severe heart damages by reducing leakage of the cardiac injury markers, such as troponin-T (cTn-T), lactate dehydrogenase (LDH), and creatine kinase-MB. The cellular architecture of cardiac sections, altered in the myocardium of infracted rats, was reversed by 5,6-PhSHC treatment. Results showed that injection of 5,6-PhSHC elicited significant cardioprotective effects by prevention of myocardium cell necrosis and inflammatory cells infiltration, along with marked decrease in plasma levels of fibrinogen. In addition, the total cholesterol, triglyceride, LDL-c, and HDL profiles underwent remarkable beneficial changes. It was also interesting to note that 5,6-PhSHC enhanced the antioxidative defense mechanisms by increasing myocardial glutathione (GSH) level, superoxide dismutase (SOD), and catalase (CAT) activities, together with reducing the levels of thiobarbituric-acid-reactive substances (TBARS), when compared with ISO-induced rats. Taken together, these findings suggested a beneficial role for 5,6-PhSHC against ISO-induced MI in rats. Furthermore, in silico analysis showed that 5,6-PhSHC pocess high computational affinities (E-value > - 9.0 kcal/mol) against cyclooxygenase-2 (PDB-ID: 1CX2), vitamin K epoxide reductase (PDB-ID: 3KP9), glycoprotein IIb/IIIa (PDB-ID: 2VDM) and catalase (PDB-ID: 1DGF). Therefore, the present study provided promising data that the newly synthesized coumarin can be useful in the design and synthesis of novel drug against Myocardial infarction. This article is protected by copyright. All rights reserved.

Gradual Versus Abrupt Reperfusion During Primary Percutaneous Coronary Interventions in ST‐Segment–Elevation Myocardial Infarction (GUARD)

Background

Intramyocardial edema and hemorrhage are key pathological mechanisms in the development of reperfusion‐related microvascular damage in ST‐segment–elevation myocardial infarction. These processes may be facilitated by abrupt restoration of intracoronary pressure and flow triggered by primary percutaneous coronary intervention. We investigated whether pressure‐controlled reperfusion via gradual reopening of the infarct‐related artery may limit microvascular injury in patients undergoing primary percutaneous coronary intervention.

Methods and Results

A total of 83 patients with ST‐segment–elevation myocardial infarction were assessed for eligibility and 53 who did not meet inclusion criteria were excluded. The remaining 30 patients with totally occluded infarct‐related artery were randomized to the pressure‐controlled reperfusion with delayed stenting (PCRDS) group (n=15) or standard primary percutaneous coronary intervention with immediate stenting (IS) group (n=15) (intention‐to‐treat population). Data from 5 patients in each arm were unsuitable to be included in the final analysis. Finally, 20 patients undergoing primary percutaneous coronary intervention who were randomly assigned to either IS (n=10) or PCRDS (n=10) were included. In the PCRDS arm, a 1.5‐mm balloon was used to achieve initial reperfusion with thrombolysis in myocardial infarction grade 3 flow and, subsequently, to control distal intracoronary pressure over a 30‐minute monitoring period (MP) until stenting was performed. In both study groups, continuous assessment of coronary hemodynamics with intracoronary pressure and Doppler flow velocity was performed, with a final measurement of zero flow pressure (primary end point of the study) at the end of a 60‐minute MP. There were no complications associated with IS or PCRDS. PCRDS effectively led to lower distal intracoronary pressures than IS over 30 minutes after reperfusion (71.2±9.37 mm Hg versus 90.13±12.09 mm Hg, P =0.001). Significant differences were noted between study arms in the microcirculatory response over MP. Microvascular perfusion progressively deteriorated in the IS group and at the end of MP, and hyperemic microvascular resistance was significantly higher in the IS arm as compared with the PCDRS arm (2.83±0.56 mm Hg.s.cm −1 versus 1.83±0.53 mm Hg.s.cm −1 , P =0.001). The primary end point (zero flow pressure) was significantly lower in the PCRDS group than in the IS group (41.46±17.85 mm Hg versus 76.87±21.34 mm Hg, P =0.001). In the whole study group (n=20), reperfusion pressures measured at predefined stages in the early reperfusion period showed robust associations with zero flow pressure values measured at the end of the 1‐hour MP (immediately after reperfusion: r =0.782, P <0.001; at the 10th minute: r =0.796, P <0.001; and at the 20th minute: r =0.702, P =0.001) and peak creatine kinase MB level (immediately after reperfusion: r =0.653, P =0.002; at the 10th minute: r =0.597, P =0.007; and at the 20th minute: r =0.538, P =0.017). Enzymatic myocardial infarction size was lower in the PCRDS group than in the IS group with peak troponin T (5395±2991 ng/mL versus 8874±1927 ng/mL, P =0.006) and creatine kinase MB (163.6±93.4 IU/L versus 542.2±227.4 IU/L, P <0.001).

Conclusions

In patients with ST‐segment–elevation myocardial infarction, pressure‐controlled reperfusion of the culprit vessel by means of gradual reopening of the occluded infarct‐related artery (PCRDS) led to better‐preserved coronary microvascular integrity and smaller myocardial infarction size, without an increase in procedural complications, compared with IS.

Registration

URL: https://www.clinicaltrials.gov ; Unique identifier: NCT02732080.

LINC00936 exacerbated myocardial infarction progression via miR-4795-3p/Wnt3a signaling pathway based on biological and imaging methods

OBJECTIVE

LncRNAs show great potential in diagnosing and treating myocardial infarction (MI). Clarifying the mechanism of lncRNAs on MI is of great significance for the application of MI biomarkers. Therefore, this report intended to determine the role and mechanism of LINC00936 on MI by biological and imaging methods.

METHODS

Hypoxia H9C2 model was established by hypoxia treatment. Flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling assay detected the apoptosis of H9C2. H2DCFDA staining and enzyme-linked immunosorbent assay (ELISA) was used to detect the reactive oxygen species (ROS) accumulation and Lactate dehydrogenase (LDH) contents, respectively. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to detect LINC00936, Wnt3a and miR-4795-3p levels. Western blot detected Wnt3a protein expression. Dual luciferase reporter assays detected the relationship of miR-4795-3p to LINC00936 or Wnt3a. Echocardiography analysis detected cardiac function. 2,3,5-Triphenyltetrazolium chloride (TTC) detected the infarct size. Masson staining detected the pathological changes.

RESULTS

LINC00936 level was elevated in the MI patients compared with the controls. Overexpression of LINC00936 promoted apoptosis and ROS accumulation in hypoxia H9C2 model and exacerbated MI progression in vivo. miR-4795-3p bound with LINC00936 in H9C2 cells and miR-4795-3p mimics inhibited apoptosis and ROS accumulation in hypoxia H9C2 model regulated by LINC00936. Wnt3a was targeted by miR-4795-3p and Wnt3a elevation promoted apoptosis and ROS accumulation in hypoxia H9C2 model.

CONCLUSION

In this report, we illustrated that LINC00936 exacerbated MI progression via the miR-4795-3p/Wnt3a signaling pathway based on biological and imaging methods. These findings might provide potential molecular target for the diagnosis and treatment of MI.

Beneficial effects of benfotiamine, a NADPH oxidase inhibitor, in isoproterenol-induced myocardial infarction in rats

BACKGROUND

Acute myocardial infarction (AMI) remains the most common cause of morbidity and mortality worldwide. The present study was directed to investigate the beneficial effects of benfotiamine pre- and post-treatments in isoproterenol (ISO)-induced MI in rats.

METHODS

Myocardial heart damage was induced by subcutaneous injection of ISO (150 mg/kg) once daily for two consecutive days. Benfotiamine (100 mg/kg/day) was given orally for two weeks before or after ISO treatment.

RESULTS

ISO administration revealed significant changes in electrocardiographic recordings, elevation of levels of cardiac enzymes; creatinine kinase (CK-MB) and troponin-I (cTn-I), and perturbation of markers of oxidative stress; nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD) and glutathione peroxidase (GPx) and markers of inflammation; protein kinase C (PKC), nuclear factor-kappa B (NF-κB) and metalloproteinase-9 (MMP-9). The apoptotic markers (caspase-8 and p53) were also significantly elevated in ISO groups in addition to histological alterations. Groups treated with benfotiamine pre- and post-ISO administration showed significantly decreased cardiac enzymes levels and improved oxidative stress, inflammatory and apoptotic markers compared to the ISO groups.

CONCLUSION

The current study highlights the potential role of benfotiamine as a promising agent for prophylactic and therapeutic interventions in myocardial damage in several cardiovascular disorders via NADPH oxidase inhibition.

Cardioprotective effects of (E)-4-hydroxy-N'-(1-(3-oxo-3H-benzo[f]chromen-2-yl)ethylidene)benzohydrazide: a newly synthesized coumarin hydrazone against isoproterenol-induced myocardial infarction in a rat model

The current study was carried out to evaluate the effect of pretreatment and co-treatment with a newly synthesized coumarin hydrazone, (E)-4-hydroxy-N'-(1-(3-oxo-3H-benzo[f]chromen-2-yl)ethylidene)benzohydrazide (hereinafter EK6), against isoproterenol-induced myocardial infarction in rats. Changes in biochemistry, cardiac biomarkers, electrocardiography, and histopathology after treatment with EK6 or acenocoumarol (Sintrom) were studied. Animals were randomly divided into 4 groups: vehicle control (C), isoproterenol + Sintrom (ISO + Sin), isoproterenol + EK6 (ISO + EK6), and isoproterenol (ISO). Myocardial infarction was induced by subcutaneous ISO administration at a dose of 85 mg·kg^-1·day^-1 with a drug-free interval of 24 h on days 6 and 7. Treatment with ISO led to significant elevation (p < 0.05) in serum levels of cardiac injury biomarkers, namely cardiac troponin-T, lactate dehydrogenase, creatine kinase-MB, alanine aminotransferase, and aspartate aminotransferase compared with levels in the vehicle control. A change in the lipid profile was also observed as a significant increase in total cholesterol and triglycerides. Furthermore, ISO caused significant alterations in the electrocardiogram pattern, including significant ST-segment elevation, significant decreased R wave amplitude, and significant increase in heart rate (16%) as well as marked changes in the histopathology of the heart tissue. Pretreatment and co-treatment with newly synthesized coumarin hydrazone restored all ISO-induced biochemical, lipid, cardiac, and histopathological changes in rats with myocardial infarction.

Hemichannel-mediated volume regulation contributes to IPC-induced cardiomyocyte protection

Cx43 has been documented to be involved in ischemic preconditioning (IPC). However, the participation of Cx43-formed hemichannels in IPC and the potential underlying mechanisms remain unclear. The present study focused on cardiomyocytes' volume regulation during IPC to investigate the role of hemichannels in the IPC-induced cardioprotection. In the study, mice cardiomyocytes were respectively treated with a hemichannel blocker, octanol or 18a-Glycyrrhizic acid (18a-GA), and a Cx43-silenced lentivirus. They were subsequently cultured in hypotonic solution to simulate ischemic reperfusion (SIR) and systemic ischemic preconditioning (SIP). Cell morphology and volumetric (area) change were detected by inverted microscopy at 30 min following the addition of hypotonic solution. Cardiomyocyte mortality was assessed by trypan blue stain assay. The analyses revealed that regardless of the treatments, hypotonic solution aggravated cell edema: Compared with the initial condition (the moment before the solution addition, 0 min), the volumetric area increased significantly 30 min later (for hypotonic+DMSO, 5,050±1,511 vs. 3,464±723 µm²; for hypotonic+scramble lentiviral vector, 5,517±1,128 vs. 2,331±536 µm²; P<0.05, respectively). Either treatment alleviated the edematous condition when a comparison was made between 30 min after the hypotonic addition and 0 min (for hypotonic+octanol, 2,990±765 vs. 2,821±773 µm²; for hypotonic+18a-GA, 4,817±1,306 vs. 4,762±1,271 µm²; for hypotonic+Cx43-silenced, 3,627±688 vs. 3,419±814 µm²; P>0.05 for all). Notably, results indicated that the SIP group had lower mortality rates compared with its SIR counterpart; the hypotonic+octanol, hypotonic+18a-GA, and hypotonic+Cx43-silenced group showed markedly-declined mortality when compared with their respective control groups (respectively, 35.70±1.02, 30.76±2.20 vs. 53.58±2.14%; 30.89±2.37 vs. 54.12±2.55%; P<0.05 for all). The results suggest that ischemic preconditioning may provide cardioprotection by blocking the opening of the hemichannels and further mediating the volume regulation of cardiomyocytes.

Effects of nimodipine, vinpocetine and their combination on isoproterenol-induced myocardial infarction in rats

BACKGROUND

Myocardial infarction (MI) remains a major cause of morbidity and mortality worldwide. Nimodipine is a calcium (Ca²⁺⁾ channel blocker as well as a PDE1 inhibitor and primarily used in subarachnoid haemorrhage (SAH) due to its blood-brain barrier crossing property. Nimodipine and vinpocetine inhibit the degradation of phosphodiester bond which increases cGMP and cAMP levels causing vasodilation.

MATERIAL AND METHODS

We have divided rats randomly into Group I - Vehicle control; Group II - Toxic control (ISO 85 mg/kg, i.p.); Group III, IV and V - Nimodipine (5, 10 and 15 mg/kg, i.p. respectively) with ISO; Group VI- Nimodipine (15 mg/kg) alone; Group VII - Nimodipine + Vinpocetine (10 mg/kg + 10 mg/kg) with ISO; Group VIII - Nimodipine + Vinpocetine (10 mg/kg + 10 mg/kg) alone; Group IX- Diltiazem (25 mg/kg, p.o) with ISO; Group X- Diltiazem (25 mg/kg) alone and Group XI- Vinpocetine (10 mg/kg, p.o.) with ISO for 7 days. After 24 h of the last dose, haemodynamics were assessed then animals were sacrificed and biochemical, histopathological and ultrastructural changes were measured.

RESULTS

Treatment with ISO significantly deviated the haemodynamic parameters (HR, SAP, DAP and MAP), biochemical parameters (CK-MB, LDH, SGOT, cGMP and Troponin-T) and antioxidant markers (TBARS, SOD, CAT, GSH, GPx, GST and GR). Haemotoxylin and eosin staining of the cardiac tissue and ultrastructural study also indicated significant myocardial damage. Pretreatment with nimodipine (10 and 15 mg/kg, i.p), vinpocetine (10 mg/kg, p.o) and their combination significantly restored the antioxidant status, haemodynamic profile, cellular architecture and ultrastructural changes in the heart.

CONCLUSION

Nimodipine and vinpocetine both showed cardioprotection when given alone. However, their combination showed better restoration in terms of oxidative stress, cardiac membrane damage, haemodynamics, histopathology and ultrastructural changes.

Dynamic Edematous Response of the Human Heart to Myocardial Infarction: Implications for Assessing Myocardial Area at Risk and Salvage

Supplemental Digital Content is available in the text.

Background:

Clinical protocols aimed to characterize the post–myocardial infarction (MI) heart by cardiac magnetic resonance (CMR) need to be standardized to take account of dynamic biological phenomena evolving early after the index ischemic event. Here, we evaluated the time course of edema reaction in patients with ST-segment–elevation MI by CMR and assessed its implications for myocardium-at-risk (MaR) quantification both in patients and in a large-animal model.

Methods:

A total of 16 patients with anterior ST-segment–elevation MI successfully treated by primary angioplasty and 16 matched controls were prospectively recruited. In total, 94 clinical CMR examinations were performed: patients with ST-segment–elevation MI were serially scanned (within the first 3 hours after reperfusion and at 1, 4, 7, and 40 days), and controls were scanned only once. T2 relaxation time in the myocardium (T2 mapping) and the extent of edema on T2-weighted short-tau triple inversion-recovery (ie, CMR-MaR) were evaluated at all time points. In the experimental study, 20 pigs underwent 40-minute ischemia/reperfusion followed by serial CMR examinations at 120 minutes and 1, 4, and 7 days after reperfusion. Reference MaR was assessed by contrast-multidetector computed tomography during the index coronary occlusion. Generalized linear mixed models were used to take account of repeated measurements.

Results:

In humans, T2 relaxation time in the ischemic myocardium declines significantly from early after reperfusion to 24 hours, and then increases up to day 4, reaching a plateau from which it decreases from day 7. Consequently, edema extent measured by T2-weighted short-tau triple inversion-recovery (CMR-MaR) varied with the timing of the CMR examination. These findings were confirmed in the experimental model by showing that only CMR-MaR values for day 4 and day 7 postreperfusion, coinciding with the deferred edema wave, were similar to values measured by reference contrast-multidetector computed tomography.

Conclusions:

Post-MI edema in patients follows a bimodal pattern that affects CMR estimates of MaR. Dynamic changes in post–ST-segment–elevation MI edema highlight the need for standardization of CMR timing to retrospectively delineate MaR and quantify myocardial salvage. According to the present clinical and experimental data, a time window between days 4 and 7 post-MI seems a good compromise solution for standardization. Further studies are needed to study the effect of other factors on these variables.

Nogo-C regulates cardiomyocyte apoptosis during mouse myocardial infarction

Myocardial infarction is caused by insufficient coronary blood supply, which leads to myocardial damage and eventually the heart failure. Molecular mechanisms associated with the loss of cardiomyocytes during myocardial infarction (MI) and ischemia-related cardiac diseases are not yet fully understood. Nogo-C is an endoplasmic reticulum protein ubiquitously expressed in tissues including in the heart, however, the cardiac function of Nogo-C is still unknown. In the present study, we found that Nogo-C was upregulated in mouse hearts after MI, and hypoxic treatments also increased Nogo-C protein level in cardiomyocytes. Adenovirus mediated overexpression of Nogo-C led to cardiomyocyte apoptosis, whereas knockdown of Nogo-c by shRNA protected cardiomyocytes from hypoxia-induced cell apoptosis. Importantly, Nogo-C knockout mice displayed improved cardiac function, smaller infarct area, and less apoptotic cells after MI. Moreover, we found that miR-182 negatively regulated Nogo-C expression and was downregulated during MI, expressing miR-182 in cardiomyocytes protected hypoxia- and Nogo-C-mediated cell apoptosis. Our results indicate that increased cardiac Nogo-C expression is both sufficient and necessary for ischemia-induced cardiomyocyte apoptosis and cardiac dysfunction, suggesting that deregulation of Nogo-C by miRNA may be a potential therapeutic target for ischemia-related heart diseases.

Protective Effects of Cardamom in Isoproterenol-Induced Myocardial Infarction in Rats

Cardamom is a popular spice that has been commonly used in cuisines for flavor since ancient times. It has copious health benefits such as improving digestion, stimulating metabolism, and exhibits antioxidant and anti-inflammatory effects. The current study investigated the effect of cardamom on hemodynamic, biochemical, histopathological and ultrastructural changes in isoproterenol (ISO)-induced myocardial infarction. Wistar male albino rats were randomly divided and treated with extract of cardamom (100 and 200 mg/kg per oral) or normal saline for 30 days with concomitant administration of ISO (85 mg/kg, subcutaneous) on 29th and 30th days, at 24 h interval. ISO injections to rats caused cardiac dysfunction evidenced by declined arterial pressure indices, heart rate, contractility and relaxation along with increased preload. ISO also caused a significant decrease in endogenous antioxidants, superoxide dismutase, catalase, glutathione peroxidase, depletion of cardiomyocytes enzymes, creatine kinase-MB, lactate dehydrogenase and increase in lipid peroxidation. All these changes in cardiac and left ventricular function as well as endogenous antioxidants, lipid peroxidation and myocyte enzymes were ameliorated when the rats were pretreated with cardamom. Additionally, the protective effects were strengthened by improved histopathology and ultrastructural changes, which specifies the salvage of cardiomyocytes from the deleterious effects of ISO. The present study findings demonstrate that cardamom significantly protects the myocardium and exerts cardioprotective effects by free radical scavenging and antioxidant activities.

Pathophysiology Underlying the Bimodal Edema Phenomenon After Myocardial Ischemia/Reperfusion

BACKGROUND

Post-ischemia/reperfusion (I/R) myocardial edema was recently shown to follow a consistent bimodal pattern: an initial wave of edema appears on reperfusion and dissipates at 24 h, followed by a deferred wave that initiates days after infarction, peaking at 1 week.

OBJECTIVES

This study examined the pathophysiology underlying this post-I/R bimodal edematous reaction.

METHODS

Forty instrumented pigs were assigned to different myocardial infarction protocols. Edematous reaction was evaluated by water content quantification, serial cardiac magnetic resonance T2-mapping, and histology/immunohistochemistry. The association of reperfusion with the initial wave of edema was evaluated in pigs undergoing 40-min/80-min I/R and compared with pigs undergoing 120-min ischemia with no reperfusion. The role of tissue healing in the deferred wave of edema was evaluated by comparing pigs undergoing standard 40-min/7-day I/R with animals subjected to infarction without reperfusion (chronic 7-day coronary occlusion) or receiving post-I/R high-dose steroid therapy.

RESULTS

Characterization of post-I/R tissue changes revealed maximal interstitial edema early on reperfusion in the ischemic myocardium, with maximal content of neutrophils, macrophages, and collagen at 24 h, day 4, and day 7 post-I/R, respectively. Reperfused pigs had significantly higher myocardial water content at 120 min and T2 relaxation times on 120 min cardiac magnetic resonance than nonreperfused animals. Permanent coronary occlusion or high-dose steroid therapy significantly reduced myocardial water content on day 7 post-infarction. The dynamics of T2 relaxation times during the first post-infarction week were altered significantly in nonreperfused pigs compared with pigs undergoing regular I/R.

CONCLUSIONS

The 2 waves of the post-I/R edematous reaction are related to different pathophysiological phenomena. Although the first wave is secondary to reperfusion, the second wave occurs mainly because of tissue healing processes.