Acupuncture: Could it be a treatment for angina pectoris?

Angina pectoris is caused by a relative reduction in oxygen in coronary blood flow and can lead to myocardial ischemia.1 Organic coronary stenosis or functional coronary artery disease (CAD) such as vasospastic angina (VSA) or microvascular angina (MVA) are suggested to be involved in causing angina pectoris.2 Drugs such as coronary vasodilators, β-blockers, renin-angiotensin-aldosterone system blockers, antiplatelet drugs and statins have generally been used as pharmacological treatments for angina pectoris.2,3 Conversely, revascularization therapy, a non-pharmacological treatment for angina pectoris, is an invasive treatment procedure that has been established and adopted for patients with organic coronary stenosis with evidence of myocardial ischemia in the clinical setting.2 Additionally, lifestyle modifications and exercises have been established as important components of the non-pharmacological treatment methods.2 Among such non-pharmacological treatments for angina pectoris, interest in acupuncture seems to be increasing recently, due to its efficacy.4–6 Therefore, we focus on acupuncture as an additional treatment procedure for angina pectoris. Acupuncture originated in China approximately 2000 years ago and is one of the oldest medical procedures in the world. It has been adopted for controlling pain. It has been shown that acupuncture regulates the autonomic nervous system and reduces sympathetic stimulation to the heart and vasculature by modulating the midbrain; endorphins and dynorphins are released, decreasing the production of norepinephrine and epinephrine.4 Experimental and human evidence has shown that acupuncture prevents endothelial dysfunction7 and inflammation,4 increases blood flow,8,9 protects myocardial reperfusion injury10 and improves cardiac function.11 Because of these favorable effects on the cardiovascular system, acupuncture may be effective against angina pectoris. To date, many studies and meta-analyses investigating the effect of acupuncture in the treatment of angina pectoris have shown that acupuncture improves angina attacks.5,12–17 Besides, many reports have confirmed that acupuncture treatment for angina pectoris showed fewer adverse effects.5,12–18 Among such studies investigating the relationship between acupuncture and anti-anginal effects,5,12–17 a systemic review and meta-analysis by Yang et al. have shown the effect of acupuncture on stable angina pectoris.5 This study seems to be unique considering the two key findings: (1) acupuncture was associated with reduced angina attack frequency but did not improve frequency of nitroglycerine (NTG) use or angina intensity; (2) acupuncture improved depression and anxiety levels compared with sham treatments or standard care alone in angina pectoris. Zhang et al.15 showed that acupuncture did not improve the frequency of NTG use despite improving angina symptoms and changes in the electrocardiogram. On the other hand, some meta-analyses have shown that acupuncture reduces the frequency of NTG use as well as angina attacks.13,16 The discrepancy in these results may be because of the difficulty in studying acupuncture, as discussed later in this paper. Furthermore, patients in the study may vary in the cause of angina pectoris in clinical studies. Conversely, mental stress such as depression and anxiety is associated with coronary artery disease;2,19 elucidating the effect of acupuncture on such mental stress in patients with angina pectoris seems to be a significant finding. Taking these findings into consideration, the meta-analysis by Yang et al.5 underlines the basis of acupuncture treatment for angina pectoris and provides some important information regarding further clinical trials. As discussed earlier, performing acupuncture in clinical studies has several challenges. Several aspects such as the acupoints,7,8,20 procedure time,8 spectral energy21 and types of needle vary in different clinical settings and may affect the results. It has been shown that differences in the acupoints may account for the differences in the increase in blood flow8,20 and the restoration of endothelial dysfunction.7 Thus, selecting and controlling such aspects may be important in future clinical studies. Nonetheless, in assessing the effects of acupuncture, undoubtedly, the major and yet unsolved problem is the placebo effect.4,5 Even with the sham group, such a placebo effect cannot be ruled out; however, it may occur more frequently in patients who undergo the standard medical therapy alone. The study by Yang et al.5 involved patients who underwent the standard medical therapy. Possible placebo effect may affect the results of meta-analyses; further clinical studies should be planned based on these findings. Recently, Zhao et al.6 have demonstrated the effect of acupuncture on stable angina pectoris in a randomized trial. Notably, the study comprised the following four groups: received acupuncture on the disease-affected meridian, received acupuncture on the acupoints on the non-affected meridian, received sham acupuncture, and received no acupuncture; this classification of groups can decrease the placebo effect to the barest minimum. The variation in patients with stable angina pectoris may contribute to another problem. For example, among patients with stable angina pectoris, there are patients with functional CAD such as MVA and patients with organic coronary stenosis who have undergone percutaneous coronary intervention and/or coronary artery bypass grafting.12 A difference in the causes of stable angina pectoris results in a difference in the effects of acupuncture on improving angina attacks. Thus, in future studies, patients should be selected more specifically. Besides, the method of assessment may also be important; for patients with functional CAD such as VSA or MVA, the questionnaire method should be used and should include the frequencies of angina attack and NTG use, as reported in previous studies.5,12–17 On the other hand, for patients with organic coronary stenosis, using myocardial perfusion imaging to analyze the extent and degree of myocardial ischemia leading to the reduction of the placebo effect may be a favorable objective assessment. Acupuncture may be one of the additional treatment options for angina pectoris. Yang et al.’s meta-analysis5 has shown the present status of such treatment more comprehensively. Further clinical studies should be planned based on such findings. The author(s) declared no potential conflicts of interest concerning the research, authorship, and/or publication of this article. The author(s) received no financial support for the research, authorship, and/or publication of this article.