Cardiorenal syndrome has attracted an enormous amount of attention, particularly in the last decade. A lot of research has been conducted in pathophysiology, haemodynamic manifestations, therapeutic options, and clinical outcomes.1,2 In practice, however, cardiorenal syndrome remains clinically challenging for both cardiologists and nephrologists. Cardiorenal syndrome covers a wide range of structural and functional disorders of both the heart and kidneys. Typically, the acute or chronic dysfunction in one organ induces acute or chronic dysfunction in the other. The interaction between the two organs may well be in multiple interfaces, such as haemodynamic cross-talk between the failing heart and the response of the kidneys and vice versa, alterations in neurohormonal markers, as well as inflammatory molecular characteristics.2 Much of the credit for the initial description of cardiorenal syndrome is attributed to Robert Bright who, in 1836, described the interdependent relationship between the kidney and the heart based on his observations on significant cardiac structural changes seen in patients with advanced kidney disease.3 The formal definition of cardiorenal syndrome and its classifications were established more recently,1,2,4 although uncertainty remains still. The classification appears to be attractive and easily applicable in clinical practice, but its value in aiding treatment or prevention strategy has yet to be ascertained.4
There are many major challenges in managing cardiorenal syndrome, its prevalence is high (in 30% of hospitalised patients with heart failure),5 it is associated with a wide range of comorbidities, its diagnostic criteria remain arbitrary, the fine balance between potential damage and therapeutic effect with the current medical treatment is hard to strike, its prognosis remains poor and its prevention has been hardly explored by the medical profession.
Prevention is better than cure
Prevention of cardiorenal syndrome, as in other medical conditions, would be much more fruitful than any treatment once occurred. The current prevention of cardiorenal syndrome is dependent on the therapeutic medication for co-existing conditions or rather its precipitators, such as hypertension, diabetes mellitus and coronary artery disease.6 Unfortunately, the medication used to treat these conditions often plays an inductive role in the development and progression of cardiorenal syndrome, particularly by worsening renal function.
To achieve effective prevention, the medical profession will have to balance the benefits against risks when treating the most common cardiovascular conditions or the precipitators of the syndrome, including hypertension, diabetes mellitus and coronary artery disease, for all of which the treatment is long term. It might be prudent to broaden our view through the lens of antiquity, that is, the ancient, but continuously practised, traditional Chinese medicine.
In textbooks of ancient Chinese medicine, though there is no specific definition of cardiorenal syndrome, cases with diseases in both heart and kidney have been recorded; for instance, the description of patients with “palpitation”, “distention”, “breathlessness” and “water Qi disorder” are similar to those with cardiorenal syndrome by contemporary concept.
According to Huangdi Neijing,7 the heart is the “dominant fire” and the kidneys are the “subordinate fire”, the functional relationship between the heart and kidneys is one between dominant and subordinate fires. It is believed that the heart, the top hierarchy, controls blood vessels and the kidneys, the subordinate, controls the “kidney water”. The relationship between the two organs is also a mutually dependent one. In other words, the heart fire prevents the kidney water from being too cold, and the kidney water prevents the heart fire from overheating.8 Therefore, the heart–kidney coordination is the foundation of the normal functions of the two organs.9,10 Hence, they must be harmonious, even supportive to each other in a normal subject. If the contrary occurs, the two may adversely affect each other so that disunity or incoordination takes place resulting in a condition called xin shen bu jiao that is quite similar to today’s cardiorenal syndrome.7
According to this ancient theory, in cardiorenal syndrome, there is a “heart–kidney discoordination” or an “imbalance of fire and water”. Heart failure is described as “heart water (Xinshui)” that manifests as “heavy chest, shortness of breath, inability of lying down, fatigue and edema”.10 Renal failure is described as “Guan (oliguria)” and “Ge (vomiting)” manifesting as dysuria with foul odour and nausea. In more severe cases, both Yin and Yang are blocked, the patients become systemically unstable and may die within a short time.7 This description is not dissimilar to the clinical presentation of acute renal failure in patients with chronic kidney disease we see nowadays. Like what we currently know, it is thought that the dysfunction of the heart or the kidneys can lead to discord between the two organs, resulting in “heart and kidney discoordination” or “water and fire discoordination”.7
If the ancient theory can be considered to be of value today, one can then see a ray of hope for preventing cardiorenal syndrome before it has fully developed. It would be a reasonable suggestion that the key to prevention of cardiorenal syndrome is to maintain the harmonious heart–kidney relationship. How can one achieve such a balance? The practical principle is to regulate the two organs in ordinary daily life in order to strengthen them both. Some simple measures are thought to be beneficial, such as keeping a calm mind and having a good sleep could nourish the heart, some herbs including lotus seed, ramulus cinnamomi and astragalus could promote Yang in both heart and kidneys to keep them healthy.11 This theory has been well known and practised in China since ancient times, it has either been taken as definitive or disregarded entirely, the former is more likely to be seen in the general public, particularly in the Chinese society, and the latter in the medical profession, particularly from mainstream medical backgrounds. One could not help but wonder whether such preventive measures could be integrated into lifestyle advice and may well be fruitful to delay or avoid the occurrence of cardiac or renal diseases, hence cardiorenal syndrome.
Therefore, it is high time to test whether the theory of “heart–kidney coordination” can help prevent cardiorenal syndrome and even its comorbidities. In order to act on such an approach, the medical profession must take the lead and work closely with patients at risk, even better if it involves public health professionals.
- Cardiorenal syndrome is common and its management remains challenging
- There is a lack of prevention of cardiorenal syndrome
- Traditional Chinese medicine may provide food for thought on the prevention of cardiorenal syndrome
Conflicts of interest
1. Ronco C, Haapio M, House AA, Anavekar N, Bellomo R. Cardiorenal syndrome. J Am Coll Cardiol 2008;52:1527–39. https://doi.org/10.1016/j.jacc.2008.07.051
2. Ronco C, McCullough P, Anker SD et al. Cardio-renal syndromes: report from the Consensus Conference of the Acute Dialysis Quality Initiative. Eur Heart J 2010;31:703–11. https://doi.org/10.1093/eurheartj/ehp507
3. Bright R. Cases and observations illustrative of renal disease accompanied by the secretion of albuminous urine. Med Chir Rev 1836;25:23–35. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5093576/
4. Rangaswami J, Bhalla V, Blair JEA et al. On behalf of the American Heart Association Council on the Kidney in Cardiovascular Disease and Council on Clinical Cardiology. Cardiorenal syndrome: classification, pathophysiology, diagnosis, and treatment strategies. A scientific statement from the American Heart Association. Circulation 2019;139:e840–e878. https://doi.org/10.1161/CIR.0000000000000664
5. Smith GL, Lichtman JH, Bracken MB et al. Renal impairment and outcomes in heart failure: systematic review and meta-analysis. J Am Coll Cardiol 2006;47:1987–96. https://doi.org/10.1016/j.jacc.2005.11.084
6. McCullough PA. Cardiorenal syndromes: pathophysiology to prevention. Int J Nephrol 2010;2011:762590. https://doi.org/10.4061/2011/762590
7. Huangdi Neijing (Inner Canon of the Emperor). The ancient text and the fundamental source of Chinese Medicine, was probably written between 400BC to 200BC. It includes Suwen (Basic Questions) and Lingshu (Spiritual Pivot). Many versions have been published. The most recent version is by Tian Daihua, Huangdi Neijing. Beijing: People’s Health Press, 2019.
8. Sun Simiao (581–682 AD). Emergency Preparations. Beijing: China Science and Technology Press (Traditional Chinese Medicine), 2011; pp. 222.
9. Yan L, Shengyuan Z, Qingqing L, Guangya L, Changbai G. To explore the pathogenesis of cardiorenal syndrome from the perspective of integrated Chinese and Western Medicine. Yunnan Journal of Traditional Chinese Medicines 2019;40:80–2.
10. Zhang Zhongjing (150–219 AD). Treatise on Exogenous Febrile Disease. Arranged by Qian Chaochen and Hao Wanshan. Beijing: People’s Health Press, 2019; pp. 88.
11. Yan D, Jie W. Discussion on the treatment of cardiorenal syndrome base on heart and kidney coordination. Zhongguo Zhong Xi Yi Jie He Za Zhi [Chinese Journal of Integrated Traditional and Western Medicine] 2017;37:1255.