Hyperbaric oxygen treatment does not affect left ventricular chamber stiffness after myocardial infarction treated with thrombolysis

Mild hyperbaric oxygen exposure protects heart during ischemia/reperfusion and affects vascular relaxation

Mild hyperbaric oxygen therapy (mHBOT) is an adjuvant therapy used in conditions where tissue oxygenation is reduced and is implemented using pressures less than 1.5 ATA and 100% O2 (instead of the classical HBOT at 1.9-3 ATA) which results in cheaper, easier to implement, and equally effective. mHBOT is offered for wellness and beauty and as an anti-aging strategy, in spite of the absence of studies on the cardiovascular system. Consequently, we investigated the impact of mHBOT on the cardiovascular system. Mechanical and energetic parameters of isolated heart submitted to ischemia/reperfusion injury and arterial contractile response from mHBOT-exposed rats were evaluated. In the heart, mHBOT increased pre-ischemic velocity of contraction and ischemic end-diastolic pressure and developed pressure and contractile economy during reperfusion. mHBOT decreased infarct size and increased the plasma nitrite levels. In the artery, mHBOT increased acetylcholine sensitivity. mHBOT protects the heart during ischemia/reperfusion and affects vascular relaxation.

Rescuing Cardiac Cells and Improving Cardiac Function by Targeted Delivery of Oxygen-Releasing Nanoparticles after or Even before Acute Myocardial Infarction

Myocardial infarction (MI) causes massive cell death due to restricted blood flow and oxygen deficiency. Rapid and sustained oxygen delivery following MI rescues cardiac cells and restores cardiac function. However, current oxygen-generating materials cannot be administered during acute MI stage without direct injection or suturing methods, both of which risk rupturing weakened heart tissue. Here, we present infarcted heart-targeting, oxygen-releasing nanoparticles capable of being delivered by intravenous injection at acute MI stage, and specifically accumulating in the infarcted heart. The nanoparticles can also be delivered before MI, then gather at the injured area after MI. We demonstrate that the nanoparticles, delivered either pre-MI or post-MI, enhance cardiac cell survival, stimulate angiogenesis, and suppress fibrosis without inducing substantial inflammation and reactive oxygen species overproduction. Our findings demonstrate that oxygen-delivering nanoparticles can provide a nonpharmacological solution to rescue the infarcted heart during acute MI and preserve heart function.

Possibilities of using hyperbaric oxygen therapy at different stages of cardiac surgery

Nowadays, the evolution of cardiac surgery is impossible without a continuous improvement of all the treatment stages. One of the promising ways to achieve this goal is the active use of hyperbaric oxygen therapy in the preoperative preparation and postoperative rehabilitation. In this review, we present a short history of the hyperbaric oxygen therapy development in cardiac surgery, the pathophysiological and pathobiochemical mechanisms of its therapeutic effect and the scenarios for its use in the preoperative preparation and postoperative rehabilitation of cardiac surgery patients. The introduction of hyperbaric oxygen therapy into cardiac surgery can improve the results of the surgical treatment, as well as reduce the times of the preoperative preparation and postoperative rehabilitation of cardiac surgery patients, that will significantly increase the quality and efficiency of cardiac surgery.

Oxygen Delivery Approaches to Augment Cell Survival After Myocardial Infarction: Progress and Challenges

Myocardial infarction (MI), triggered by blockage of a coronary artery, remains the most common cause of death worldwide. After MI, the capability of providing sufficient blood and oxygen significantly decreases in the heart. This event leads to depletion of oxygen from cardiac tissue and consequently leads to massive cardiac cell death due to hypoxemia. Over the past few decades, many studies have been carried out to discover acceptable approaches to treat MI. However, very few have addressed the crucial role of efficient oxygen delivery to the injured heart. Thus, various strategies were developed to increase the delivery of oxygen to cardiac tissue and improve its function. Here, we have given an overall discussion of the oxygen delivery mechanisms and how the current technologies are employed to treat patients suffering from MI, including a comprehensive view on three major technical approaches such as oxygen therapy, hemoglobin-based oxygen carriers (HBOCs), and oxygen-releasing biomaterials (ORBs). Although oxygen therapy and HBOCs have shown promising results in several animal and clinical studies, they still have a few drawbacks which limit their effectiveness. More recent studies have investigated the efficacy of ORBs which may play a key role in the future of oxygenation of cardiac tissue. In addition, a summary of conducted studies under each approach and the remaining challenges of these methods are discussed.

Hyperbaric oxygenation improves redox control and reduces mortality in the acute phase of myocardial infarction in a rat model

Among the mechanisms of action of hyperbaric oxygenation (HBO), the chance of reducing injury by interfering with the mechanisms of redox homeostasis in the heart leads to the possibility of extending the period of viability of the myocardium at risk. This would benefit late interventions for reperfusion to the ischemic area. The objective of the present study was to investigate the changes in the redox system associated with HBO therapy maintained during the first hour after coronary occlusion in an acute myocardial infarction (MI) rat model. Surviving male rats (n=105) were randomly assigned to one of three groups: Sham (SH=26), myocardial infarction (MI=45) and infarction+hyperbaric therapy (HBO=34, 1 h at 2.5 atm). After 90 min of coronary occlusion, a sample of the heart was collected for western blot analysis of total protein levels of superoxide dismutase, catalase, peroxiredoxin and 3‑nitrotyrosine. Glutathione was measured by enzyme‑linked immunosorbent assay (ELISA). The detection of the superoxide radical anion was carried out by oxidation of dihydroethidium analyzed with confocal microscopy. The mortality rate of the MI group was significantly higher than that of the HBO group. No difference was noted in the myocardial infarction size. The oxidized/reduced glutathione ratio and peroxiredoxin were significantly higher in the SH and MI when compared to the HBO group. Superoxide dismutase enzymes and catalase were significantly higher in the HBO group compared to the MI and SH groups. 3‑Nitrotyrosine and the superoxide radical were significantly lower in the HBO group compared to these in the MI and SH groups. These data demonstrated that hyperbaric oxygenation therapy decreased mortality by improving redox control in the hearts of rats in the acute phase of myocardial infarction.

An Injectable Oxygen Release System to Augment Cell Survival and Promote Cardiac Repair Following Myocardial Infarction

Oxygen deficiency after myocardial infarction (MI) leads to massive cardiac cell death. Protection of cardiac cells and promotion of cardiac repair are key therapeutic goals. These goals may be achieved by re-introducing oxygen into the infarcted area. Yet current systemic oxygen delivery approaches cannot efficiently diffuse oxygen into the infarcted area that has extremely low blood flow. In this work, we developed a new oxygen delivery system that can be delivered specifically to the infarcted tissue, and continuously release oxygen to protect the cardiac cells. The system was based on a thermosensitive, injectable and fast gelation hydrogel, and oxygen releasing microspheres. The fast gelation hydrogel was used to increase microsphere retention in the heart tissue. The system was able to continuously release oxygen for 4 weeks. The released oxygen significantly increased survival of cardiac cells under the hypoxic condition (1% O₂) mimicking that of the infarcted hearts. It also reduced myofibroblast formation under hypoxic condition (1% O₂). After implanting into infarcted hearts for 4 weeks, the released oxygen significantly augmented cell survival, decreased macrophage density, reduced collagen deposition and myofibroblast density, and stimulated tissue angiogenesis, leading to a significant increase in cardiac function.

Hyperbaric oxygen therapy for acute coronary syndrome

BACKGROUND

Acute coronary syndrome (ACS), includes acute myocardial infarction and unstable angina, is common and may prove fatal. Hyperbaric oxygen therapy (HBOT) will improve oxygen supply to the threatened heart and may reduce the volume of heart muscle that perishes. The addition of HBOT to standard treatment may reduce death rate and other major adverse outcomes.This an update of a review previously published in May 2004 and June 2010.

OBJECTIVES

The aim of this review was to assess the evidence for the effects of adjunctive HBOT in the treatment of ACS. We compared treatment regimens including adjunctive HBOT against similar regimens excluding HBOT. Where regimens differed significantly between studies this is clearly stated and the implications discussed. All comparisons were made using an intention to treat analysis where this was possible. Efficacy was estimated from randomised trial comparisons but no attempt was made to evaluate the likely effectiveness that might be achieved in routine clinical practice. Specifically, we addressed:Does the adjunctive administration of HBOT to people with acute coronary syndrome (unstable angina or infarction) result in a reduction in the risk of death?Does the adjunctive administration of HBOT to people with acute coronary syndrome result in a reduction in the risk of major adverse cardiac events (MACE), that is: cardiac death, myocardial infarction, and target vessel revascularization by operative or percutaneous intervention?Is the administration of HBOT safe in both the short and long term?

SEARCH METHODS

We updated the search of the following sources in September 2014, but found no additional relevant citations since the previous search in June 2010 (CENTRAL), MEDLINE, EMBASE, CINAHL and DORCTHIM. Relevant journals were handsearched and researchers in the field contacted. We applied no language restrictions.

SELECTION CRITERIA

Randomised studies comparing the effect on ACS of regimens that include HBOT with those that exclude HBOT.

DATA COLLECTION AND ANALYSIS

Three authors independently evaluated the quality of trials using the guidelines of the Cochrane Handbook and extracted data from included trials. Binary outcomes were analysed using risk ratios (RR) and continuous outcomes using the mean difference (MD) and both are presented with 95% confidence intervals. We assessed the quality of the evidence using the GRADE approach.

MAIN RESULTS

No new trials were located in our most recent search in September 2014. Six trials with 665 participants contributed to this review. These trials were small and subject to potential bias. Only two reported randomisation procedures in detail and in only one trial was allocation concealed. While only modest numbers of participants were lost to follow-up, in general there is little information on the longer-term outcome for participants. Patients with acute coronary syndrome allocated to HBOT were associated with a reduction in the risk of death by around 42% (RR: 0.58, (95% CI 0.36 to 0.92), 5 trials, 614 participants; low quality evidence).In general, HBOT was well-tolerated. No patients were reported as suffering neurological oxygen toxicity and only a single patient was reported to have significant barotrauma to the tympanic membrane. One trial suggested a significant incidence of claustrophobia in single occupancy chambers of 15% (RR of claustrophobia with HBOT 31.6, 95% CI 1.92 to 521).

AUTHORS' CONCLUSIONS

For people with ACS, there is some evidence from small trials to suggest that HBOT is associated with a reduction in the risk of death, the volume of damaged muscle, the risk of MACE and time to relief from ischaemic pain. In view of the modest number of patients, methodological shortcomings and poor reporting, this result should be interpreted cautiously, and an appropriately powered trial of high methodological rigour is justified to define those patients (if any) who can be expected to derive most benefit from HBOT. The routine application of HBOT to these patients cannot be justified from this review.

Oxygen therapy in acute coronary syndrome: are the benefits worth the risk?

Oxygen supplementation is a standard treatment for all patients who present with acute coronary syndrome, regardless of oxygen saturation levels. Most of the data regarding the function of oxygen in myocardial infarction is based on a limited number of basic and clinical studies. We performed a systematic literature review that explores the basic and clinical data on the function of oxygen in ischaemic heart disease and myocardial infarction. This review discusses many aspects of oxygen treatment: (i) basic studies on the effects of oxygen in ischaemia and the potential cardiovascular effects of oxygen metabolites; (ii) clinical trials that have assessed the value of inhaled oxygen, supersaturated oxygen, and intracoronary injection of hyperoxaemic solutions in myocardial infarction; and (iii) the haemodynamic effects of oxygen in various clinical scenarios and its direct effects on the coronary vasculature. Our findings suggest that there are conflicting data on the effects of oxygen treatment. Further, the potential harmful effects of oxygen must be considered, particularly in myocardial infarction. These findings question the current guidelines and recommendations and emphasize the need for large clinical trials.

Hyperbaric oxygen therapy for acute coronary syndrome

BACKGROUND

Acute coronary syndrome (ACS), includes acute myocardial infarction and unstable angina, is common and may prove fatal. Hyperbaric oxygen therapy (HBOT) will improve oxygen supply to the threatened heart and may reduce the volume of heart muscle that perishes. The addition of HBOT to standard treatment may reduce death rate and other major adverse outcomes.

OBJECTIVES

To assess the benefits and harms of adjunctive HBOT for treating ACS.

SEARCH STRATEGY

We updated the search of the following sources in June 2010, finding one further trial: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, CINAHL, DORCTHIM, LILACS and checked the references from selected articles. Relevant journals were handsearched and researchers in the field contacted. No language restrictions were applied.

SELECTION CRITERIA

Randomised studies comparing the effect on ACS of regimens that include HBOT with those that exclude HBOT.

DATA COLLECTION AND ANALYSIS

Three reviewers independently evaluated the quality of trials using the guidelines of the Cochrane Handbook and extracted data from included trials.

MAIN RESULTS

Six trials with 665 participants contributed to this review. There was a significant decrease in the risk of death with HBOT (risk ratio (RR) 0.58, 95% CI 0.36 to 0.92, P = 0.02). The extent of heart muscle damage was lower following HBOT, as shown by a lesser rise in muscle enzyme in the blood (mean difference (MD) 493 IU, P = 0.005) and a better LVEF (MD 5.5%, P = 0.001). There was evidence from individual trials of reductions in the risk of major adverse coronary events (MACE) (RR 0.12, P = 0.03); re-infarction (RR 0.28, P = 0.04) and dysrhythmias following HBOT (RR 0.59, P = 0.01, and the time to relief of pain was reduced with HBOT (MD 353 minutes shorter, P < 0.00001). One trial suggested a significant incidence of claustrophobia in single occupancy chambers of 15% (RR of claustrophobia with HBOT 31.6, P = 0.02).

AUTHORS' CONCLUSIONS

For people with ACS, there is some evidence from small trials to suggest that HBOT is associated with a reduction in the risk of death, the volume of damaged muscle, the risk of MACE and time to relief from ischaemic pain. In view of the modest number of patients, methodological shortcomings and poor reporting, this result should be interpreted cautiously, and an appropriately powered trial of high methodological rigour is justified to define those patients (if any) who can be expected to derive most benefit from HBOT. The routine application of HBOT to these patients cannot be justified from this review.

Can hyperbaric oxygen be used as adjunctive heart failure therapy through the induction of endogenous heat shock proteins?

Heart failure (HF) is a chronic condition that is expected to increase in incidence along with increased life expectancy and an aging population. As the incidence of HF increases, the cost to national healthcare budgets is expected to run into the billions. The costs of lost productivity and increased social reliance on state support must also be considered. Recently, acute myocardial infarction (AMI) has come to be seen as the major contributing factor to HF. Although thrombolysis may restore coronary perfusion after an AMI, it may also introduce ischemic reperfusion injury (IRI). In an attempt to ameliorate sustained protein damage caused by IRI, endogenous chaperone proteins known as heat shock proteins (HSPs) are induced as a consequence of the stress of IRI. Recently, hyperbaric oxygen has been shown to induce the production of HSPs in noncardiac tissue, with a resultant protective effect. This current opinion review article suggests a possible role for hyperbaric oxygen, as a technologically modern drug, in augmenting the induction of endogenous HSPs to repair and improve the function of failing hearts that have been damaged by AMI and IRI. In addition, this simple, safe, noninvasive drug may prove useful in easing the economic burden of HF on already overextended health resources.

Hyperbaric oxygen therapy for acute coronary syndrome

BACKGROUND

Acute coronary syndrome (ACS) includes acute myocardial infarction and unstable angina. ACS is common and may prove fatal. Hyperbaric oxygen therapy (HBOT) will improve oxygen supply to the threatened heart and may reduce the volume of heart muscle that will perish. The addition of HBOT to the standard treatment may reduce death rate and other major adverse outcomes.

OBJECTIVES

To assess the benefits and harms of adjunctive HBOT for treating ACS.

SEARCH STRATEGY

We searched the following from inception to November 2004: CENTRAL, MEDLINE, EMBASE, CINAHL, DORCTHIM, and references from selected articles. Relevant journals were handsearched and researchers in the field contacted.

SELECTION CRITERIA

Randomised studies comparing the effect on ACS of regimens that include HBOT with those that exclude HBOT.

DATA COLLECTION AND ANALYSIS

Three reviewers independently evaluated the quality of trials using the guidelines of the Cochrane Handbook and extracted data from included trials.

MAIN RESULTS

Four trials with 462 participants contributed to this review. There was a trend towards, but no significant decrease in, the risk of death with HBOT (relative risk (RR) 0.64, 95% CI 0.38 to 1.06, P=0.08). There was evidence from individual trials of reductions in the risk of major adverse coronary events [MACE] (RR 0.12, 95% CI 0.02 to 0.85, P=0.03; NNT 4, 95% CI 3 to 10) and some dysrhythmias following HBOT (RR 0.59, 95% CI 0.39 to 0.89, P=0.01; NNT 6, 95% CI 3 to 24), particularly complete heart block (RR 0.32, 95%CI 0.12 to 0.84, P=0.02), and that the time to relief of pain was reduced with HBOT (Weighted Mean Difference [WMD] 353 minutes shorter, 95% CI 219 to 488, P<0.0001). One trial suggested a significant incidence of claustrophobia in single occupancy chambers of 15% (RR of claustrophobia with HBOT 31.6, 95%CI 1.92 to 521, P=0.02).

AUTHORS' CONCLUSIONS

For people with ACS, individual small trials suggest the addition of HBOT reduced the risk of Major Adverse Cardiac Events, some dysrrhythmias, and reduced the time to relief from ischaemic pain, but did not reduce mortality. In view of the modest number of patients, methodological shortcomings and poor reporting, this result should be interpreted cautiously, and an appropriately powered trial of high methodological rigour is justified to define those patients (if any) who can be expected to derive most benefit from HBOT. The routine application of HBOT to these patients cannot be justified from this review.