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Liebert A.1,2, Kiat H.3, Bicknell B.4, Goonetilleke N.5, Krause A.6
1Sydney University, Bosch Institute, Sydney, Australia, 2Australasian Research Institute, Photomolecular Research, Wahroonga, Australia, 3University of NSW, Medicine, Sydney, Australia, 4Australian Catholic University, Science, North Sydney, Australia, 5Blacktown Hospital, Cardiology, Blacktown, Australia, 6Muswellbrook Hospital, Physiotherapy, Muswellbrook, Australia
Background: Myocardial ischemia reperfusion injury is a negative pathophysiological event that may result in cardiac cell apoptosis and is a result of coronary revascularization and cardiac intervention procedures. The resulting loss of cardiomyocyte cells and the formation of scar tissue, impair heart function and this is a major prognostic determinant of long-term cardiac outcomes. Photobiomodulation has been practiced by physiotherapists for many years to treat pain, lymphoedema and sports injuries. More recently it has been used as an adjunct to exercise in cardiac rehabilitation programs. Photobiomodulation is potentially a novel cardiac surgery intervention to prevent myocardial ischemia reperfusion related myocardial injury. A growing body of evidence supporting the use of photobiomodulation in myocardial infarct models has implicated multiple molecular interactions.
Purpose: A systemic review was conducted to identify the strength of the evidence for the therapeutic effect of photobiomodulation and to summarise the current evidence as to its mechanisms.
Methods: The review was conducted according to PRISMA guidelines. Articles (English language and post 1994) were extracted from databases using a limited set of keywords. Articles investigating therapeutic, procedural or methodological applications of photobiomodulation were accepted, in animal and tissue studies as well as clinical trials. Experimental design had to be representative of either ischemic and/or reperfusion injury. The primary outcome of the review was changes to mortality, cardiac tissues or cells or a change to molecular markers of cardiac function. Secondary outcomes were changes to other molecular markers, such as signalling molecules, redox markers or cytokines. Laser dose parameters were standardized by conversion into total dose administered (joules per square cm). Qualitative analysis of clinical triasl was conducted using the JADAD scale and risk of bias for animal studies was assessed using the SYRCLE tool.
Results: Photobiomodulation showed consistently positive effects over a range of wavelengths and application parameters, with reductions in total infarct size (up to 69%), decreases in restenosis rates and increases in lumen diameter. Multiple molecular pathways were identified, including modulation of inflammatory cytokines, signalling molecules, transcription factors, enzymes and antioxidants.
Conclusion(s): Photobiomodulation was shown to be a safe and effective adjunct therapy to reducing adverse outcomes of cardiac reperfusion across a range of clinical parameters in tissue, animal and human experiments.
Implications: While it is difficult to generalise from animal experiments to clinical responses, it is clear that photobiomodulation has an overwhelmingly positive effect across similar markers. Photobiomodulation is a safe and cost effective adjunct treatment, without the potentially harmful side-effects of drug therapy. Current evidence regarding the use of photobiomodulation in acute and planned cardiac intervention is still at an early stage but is sufficient to warrant the establishment of a blinded clinical trial.
Funding acknowledgements: No funding
Topic: Cardiorespiratory
Ethics approval: No ethics approval required
All authors, affiliations and abstracts have been published as submitted.
