Low-Level Laser Application in the Early Myocardial Infarction Stage Has No Beneficial Role in Heart Failure

Abstract

Low-level laser therapy (LLLT) has been targeted as a promising approach that can mitigate post-infarction cardiac remodeling. There is some interesting evidence showing that the beneficial role of the LLLT could persist long-term even after the end of the application, but it remains to be systematically evaluated. Therefore, the present study aimed to test the hypothesis that LLLT beneficial effects in the early post-infarction cardiac remodeling could remain in overt heart failure even with the disruption of irradiations. Female Wistar rats were subjected to the coronary occlusion to induce myocardial infarction or Sham operation. A single LLLT application was carried out after 60 s and 3 days post-coronary occlusion, respectively. Echocardiography was performed 3 days and at the end of the experiment (5 weeks) to evaluate cardiac function. After the last echocardiographic examination, LV hemodynamic evaluation was performed at baseline and on sudden afterload increases. Compared with the Sham group, infarcted rats showed increased systolic and diastolic internal diameter as well as a depressed shortening fraction of LV. The only benefit of the LLLT was a higher shortening fraction after 3 days of infarction. However, treated-LLLT rats show a lower shortening fraction in the 5th week of study when compared with Sham and non-irradiated rats. A worsening of cardiac function was confirmed in the hemodynamic analysis as evidenced by the higher LV end-diastolic pressure and lower +dP/dt and −dP/dt with five weeks of study. Cardiac functional reserve was also impaired by infarction as evidenced by an attenuated response of stroke work index and cardiac output to a sudden afterload stress, without LLLT repercussions. No significant differences were found in the myocardial expression of Akt1/VEGF pathway. Collectively, these findings illustrate that LLLT improves LV systolic function in the early post-infarction cardiac remodeling. However, this beneficial effect may be dependent on the maintenance of phototherapy. Long-term studies with LLLT application are needed to establish whether these effects ultimately translate into improved cardiac remodeling.

Photobiomodulation Leads to Reduced Oxidative Stress in Rats Submitted to High‐Intensity Resistive Exercise

“…We followed the methods of Manchini et al [ 32 ] and Melo et al [ 33 ] for the muscle tissue processing and for protein extraction. Protein samples (20 μ g) were subjected to SDS-PAGE in 10–12% polyacrylamide gel.…”

Effects of exercise training and TrkB blockade on cardiac function and BDNF-TrkB signaling postmyocardial infarction in rats

“…Several studies evaluated in rodents changes in Akt, CaMKII, and AMPK in the LV post-MI. At 4 -6 wk post-MI in rats, the p-Akt-to-total Akt ratio in the non-and peri-infarct areas of the LV was not changed (10,36). Exercise training increased the p-Akt-to-total Akt ratio in the peri-infarct area of the LV (noninfarct area was not assessed) and attenuated the increase in TUNEL-positive cells and the Bax-to-Bcl-2 ratio (10).…”

Aging Attenuates Cardiac Contractility and Affects Therapeutic Consequences for Myocardial Infarction

“…Systolic dysfunction was improved and infarct size was reduced by low-level laser in the early stage of MI. Interestingly, but no effect on ischemia-induced end-stage heart failure [89].…”