Cardiovascular diseases constitute one of the major causes of disability and death all over the world. Increased mechanisation, Westernisation of lifestyle and genetic factors, coupled with an increase in life expectancy owing to control of infectious diseases, have contributed to its rise in the developing world as well.
Despite remarkable advances in the identification of various risk factors and our enhanced knowledge regarding the aetiopathogenesis of cardiovascular diseases and molecular targeting for drug development, effective drug management of cardiovascular diseases still eludes medical researchers. There continues to be an unmet need for better and safer drugs to treat as well as to prevent cardiovascular diseases. In this regard, it is important to remember that many of the cardiovascular diseases are preventable, either by lifestyle modification and/or by drugs.
The past few decades have witnessed the introduction of a remarkable number of not only new drugs, but also new classes of drugs, for the treatment of cardiovascular diseases. These include calcium-channel blockers, angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, various hypolipidaemic agents, and various antiplatelet drugs. On the other hand, a few of the older drugs, such as digoxin, the first to be introduced to treat heart failure, have taken a back seat, not only because of their serious side-effect profile, as well as the discovery of safer and more effective drugs, but also as a consequence of improved understanding of cardiovascular diseases mechanisms.
Herbal medicine and Cardiovascular Diseases
Cardiovascular drugs include many whose origin can be traced to natural sources, e.g. digoxin (Digitalis purpurea), reserpine (Rauwolfia serpentina), aspirin (bark of willow Salix spp.) and taxol (Taxus brevifolia), the last one being used in drug-eluting stents to prevent restenosis following coronary angioplasty. All these examples demonstrate the vast potential of herbal products, their extracts and active principles in the management of cardiovascular diseases.
In many countries, there is a rich tradition of herbal medicine, and herbal preparations are available to patients, for which a prescription from a medical practitioner is not required. Moreover, many of these herbal preparations are prescribed legally by practitioners of some locally recognised alternative systems of medicine but, unfortunately, authentic information about the source and reliability of these herbal preparations is very often not available. Even in many developing countries, over-the-counter herbal preparations are widely used, but have hardly any regulatory control. In view of these issues, there is a global need for adopting guidelines for screening for efficacy, safety and quality (standardisation) of these preparations.
In this chapter, screening methods for herbal products for ischaemic heart disease, hypertension and heart failure are discussed. Cardiac arrhythmias and some cardiomyopathies are not dealt with here because of their more complex aetiopathogenesis and lower incidence, respectively.
Screening for efficacy of herbal preparations in cardiovascular diseases
There is a need to reconsider and reassess our traditional approach for identifying pharmacological activities with reference to our current knowledge and understanding of cardiovascular diseases. For instance, about a half-century ago, drugs with potential positive inotropic effect were thought to be useful candidates for use in heart failure, but today, beta-blockers, which are primarily cardiodepressants, are preferred over positive inotropic agents, even in advanced stages of heart failure! Therefore, understanding the pathological processes behind these diseases is essential before embarking on the task of screening for pharmacological effects.