This systematic review is the first to investigate the potential relationships between moxibustion prescription parameters (moxibustion equipment, moxibustion materials, frequency, and duration) in TCM therapy and clinical efficacy in HF patients. Previous reviews combined moxibustion prescriptions but did not examine each parameter separately [29]. In particular the relationships of moxibustion materials and/or duration with clinical efficacy and changes in prognosis following TCM treatment had not been previously investigated.
Moxibustion is an effective method for prevention and treatment of HF and is a commonly used adjuvant therapy in clinical practice. Moxibustion has functions such as warming meridians, dispersing cold, and promoting blood circulation and qi circulation. Previous studies have demonstrated the therapeutic role of moxibustion using volatile oil of wormwood leaves (which includes platyclone, eucalyptus oil essence, β-caryophyllene, and 39 other compounds) and infrared resonance radiation of acupoints under pathological conditions [30–31]. In addition, this treatment has the potential to improve cardiac function and regulate neuroendocrine reactions [32]. Clinical research has suggested that TCM therapy (e.g. moxibustion) can effectively alleviate symptoms and improve the quality of life of patients with CHF [33].
Although previous systematic evaluations and meta-analyses indicate that acupuncture and moxibustion are inseparable, they both act on acupoints and meridians. However, the primary mode of action of moxibustion involves a photothermal effect, whereas acupuncture involves mechanical stimulation. In addition, acupuncture is mainly used to dispel the causes of disease, so it is mostly used in excess heat syndrome, whereas moxibustion is mainly used to nourish the body and is mostly used in deficiency cold syndrome. Because the theory of TCM believes that the disease nature of HF is mainly deficiency cold, moxibustion is more suitable for the treatment of HF than acupuncture.
None of the 11 studies included were placebo-controlled. In fact, in China, the birthplace of acupuncture and moxibustion, clinical trials rarely include sham acupuncture groups. Thousands of years of clinical experience and curative effects have proved the effectiveness of acupuncture and moxibustion. Moreover, traditional Chinese medicine includes both physiological and psychological interventions. Regulating the mind is an essential purpose of acupuncture and moxibustion treatment. The so-called placebo effect is closely related to psychological suggestion. Through our meta-analysis, we found that the material, treatment time, and times of wormwood leaves may affect the curative effect of moxibustion. Through further research, we found that in most cases, the materials of moxibustion included wormwood leaves and/or other Chinese herbal medicines such as aconite and ginger. The average retention time of moxibustion is about 25 min (excluding long snake moxibustion). Most studies were conducted over 3 to 12 weeks, three to seven times a week.
This meta-analysis showed that compared with conventional therapy, moxibustion therapy could significantly improve the 6-MWD and LVEF scores of patients with HF and reduce their NT-proBNP scores. In addition, the evidence was assessed as medium and low quality, respectively. 6-MWT can be used for efficacy detection, cardiac function evaluation, and prognostic evaluation in cardiovascular diseases [34–35]. Studies of patients with CHF have shown that a 6-MWT walking distance of less than 300 m is associated with a 1-year mortality as high as 50%. In patients with a walking distance greater than 450 m, mortality is significantly reduced [36]. In the current study, we found that moxibustion could improve the 6-MWT scores of patients. Sensitivity analysis showed that when similar moxibustion materials were used, the statistical heterogeneity disappeared, indicating that the use of different moxibustion materials may affect the heterogeneity. Finally, the included literature was of low quality. More reliable evidence is needed to demonstrate that moxibustion improves cardiac function in patients with HF.
Cardiac ultrasound has a vital role in hemorheology and examination of cardiac structural changes in patients with HF. LVEF is an important index that is used to judge cardiac ejection function [37]. According to this meta-analysis, moxibustion could improve LVEF scores. Sensitivity analysis showed that the use of different materials of moxibustion may have led to high heterogeneity. The occurrence and development of HF are closely related to changes in various humoral factors. In particular, NT-proBNP has high specificity and sensitivity for the detection of ventricular function [38]. As well as indicating early changes in ventricular function, it can reflect the severity of CHF and is a significant predictor of cardiac system death and events. According to this meta-analysis, moxibustion could reduce NT-proBNP scores. Sensitivity analysis showed that differences in the number of moxibustion treatments may have been the reason for the heterogeneity among studies. In addition, two studies were of medium quality and thus represent important references for evaluating the efficacy of moxibustion.
Leehfs is a scoring system that was formulated by Lee in 1982, based on clinical manifestations and changes in patient X-rays. It has been widely recognized as a relatively objective standard that can be used to evaluate the curative effects of HF treatments. Leehfs can comprehensively reflect the therapeutic effect of moxibustion on HF [39]. During the onset of HF, the rise of ventricular wall pressure and ventricular endocrine BNP leads to increased BNP levels in the blood. Some studies have shown that detection of BNP is helpful for early diagnosis of CHF [40]. These two indexes demonstrate the superiority of moxibustion combined with conventional treatment.
The advantages of this review include the following. (1) Acupuncture, traditional Chinese medicine decoction, heaven moxibustion, and other therapies with essentially different effects from moxibustion were excluded, to ensure the consistency of the therapies received by patients with HF. (2) The moxibustion materials, treatment frequency, and the duration of each individual treatment of moxibustion were analyzed in detail, and the curative effects of different moxibustion methods could be compared. (3) A comprehensive search strategy covering seven databases was formulated. (4) The review evaluated the quality of the literature and provides quality reference for the clinical use of moxibustion.
This study also had some limitations. (1) Owing to the differences in moxibustion implementation methods, moxibustion materials, treatment frequency, and treatment time, some heterogeneity of results was evident. (2) There were some differences between acute HF and CHF. (3) Most studies did not specifically describe the process of randomization, allocation concealment, and blinding, resulting in low overall quality and high risk of bias. (4) Most studies did not describe their ethical review status, and there is the possibility that experimental ethics were violated.
This paper provides some insight for future research. First, moxibustion materials, single treatment time, and total treatment times have different effects on the improvement in cardiac function. Their relevance can be further clarified later. Second, previous studies have lacked long-term follow-up, so it is necessary to evaluate the efficacy of moxibustion therapy further to determine whether it can reduce the hospitalization rate and mortality. Third, to further determine the optimal frequency and amount of moxibustion for the treatment of HF and promote this therapy, a strict, standardized, and high-quality RCT design is required to provide high-quality evidence.