Cardiology (from Greek καρδίᾱ, kardiā, "heart"; and -λογία, -logia) is a medical specialty dealing with disorders of the heart. The field includes diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease andelectrophysiology.
Currently, in non-industrialized regions major infectious diseases cause more twelve million deaths annually. In industrialized regions, these account for less than two million, that are equivalent to those resulting from industrialization itself. In this heterogeneous environment, it is striking that ischemic heart disease appears still to be responsible for 2.5 and 3.5 million deaths annually in the developing and developed areas respectively (WHO). Far from mitigating these figures, the future projections predict that the increased longevity and changing lifestyles will rise these numbers to even higher levels.
In 2006, was published by J. Leal et al (J Leal, 2006) one of the most comprehensive studies performed to date which reflects the socio-economic impact of cardiovascular disease in the European Union. According to official data, in 2003 cardiovascular disease accounted for 12% of total health expenditure, where more than one fourth were justified by ischemic heart disease, a proportion that maintains and even increases in other regions. In 2003, expenses and losses resulting from ischemic heart disease were estimated at 44.725 million euro for the whole European Union, and one third of this amount was due to production and productivity losses due to mortality and morbidity (Leal J, 2006).
The picture is equally disturbing in other economic areas. In the U.S., with a population equal to 70% of European, ischemic heart disease are behind one of every five deaths, and gross expenditure on cardiovascular diseases is twice the European and domestic spending double that derived from all types of cancer (Lloyd-Jones, 2009). In emerging countries like India, China, Brazil, Mexico and South Africa, cardiovascular diseases already account as an important socio-economic factor and as a whole, 21 million years of future productive life are lost annually in the five countries (Gaziano A, 2007). Currently, Africa is the only economic region in which cardiovascular diseases are not the leading cause of death and, if current trends continue, it is estimated that in the coming years, cardiovascular diseases constitute a significant imbalance factor in many economies. No wonder then that, year after year, they devote a major part of the health budget to prevention, diagnosis, treatment and research of various cardiovascular diseases, particularly ischemic heart disease.
Historical perspective and state of the art in prevention, diagnosis and prognosis, with a particular emphasis on IHF.
Historical context. In 1768 William Heberden, in his essay on angina, published the first detailed study on ischemic heart disease. We had to wait 140 years until 1912, when James B. Herrick published the first paper in which he described a case of acute myocardial infarction (JB Herrick, 1912), three years after the introduction of the ECG. In this work, Herrick dismissed the perception of sudden death from heart failure following a deadly toxin, describing myocardial infarction and cardiac ischemia common survival and damage often were not irreversible. It was perhaps this study a starting point or inspiration for works and technological advances that, during the twentieth century have contributed the to increasing knowledge about a set of conditions that, in view of the figures reflected in the previous section, are called to become one of the greatest health challenges of the XXI century. In the 30’s the ECG system by precordial leads was introduced and became one of the cornerstones in the diagnosis of ischemic heart disease. In the 50’s it began the use of defibrillators and external pacemakers, which are essential in the treatment, and it was also introduced the first coronary arteriography. Previously, in 1948, 5,209 people between 30 and 62 years living in Framingham (United States) were recruited to join the first prospective study to reveal patterns in the development of cardiovascular disease. On 3 December 1967 Christiaan Barnard performed in Cape Town (South Africa) the first successful heart transplant between humans. The recipient, Louis Washkansky, 54 years old and suffering from recurrent myocardial infarction, die 18 days later of pneumonia induced by immunosuppressive therapy. Currently, there are already patients who survive more than 25 years with a transplanted heart (Yacoub M, 2008). Worldwide, about 3,500 heart transplantations are performed annually by a surgery that has become routine but yet is awaited by about 800,000 people (Reiner Korf, interview, 2007).
It is fair to say that cardiac transplantation has been a huge advance in the care of patients with severe heart failure but, however, is nonetheless extremely risky surgery to replace an organ that has lost its functionality irreversibly, and therefore it is a solution reserved for cases with no alternative. For this reason, it is essential to foster the development of therapeutic strategies that seek to halt or reverse the processes that ensue to, in the case of myocardial infarction, an event of prolonged ischemia. In the early 70s were introduced in clinical practice techniques are still in force, like reperfusion catheterization or coronary bypass, which tries to restore blood flow in the region affected by the ischemia. At the end of that decade it was established the use of the creatine phosphokinase test for diagnosis and prescription of the β-blockers (β-adrenergic antagonists) in patients who had both angina and myocardial infarction. They became of general use during the next decade, along with the introduction of coronary angioplasty and the use of thrombolytic agents. The '90s saw the emergence and spread of inhibitors of the renin-angiotensin system (ACEIs), the use of coronary stents and implementation of serological tests with the introduction of the troponin-T test.
Current scenario. Classic therapeutic strategies against myocardial infarction were characterized by being geared toward the arrest of the processes initiated after the ischemic event, but none has offered the restoration of the pre-ischemic state and therefore, although they have very significantly reduced the mortality and improved quality of life, patients who have suffered a heart attack continue to suffer limitations that indicate that there is still a long way in treating this and other cardiovascular diseases. Late in the decade of the '90s, with the development of molecular and cell biology, cell therapy was proposed as the first realistic strategy for restoration and regeneration of cardiac tissue. This practice posits the use of cells of different origins, which, after injection into the cardiac environment and subsequent phenotypic differentiation, agents act as restorers of myocardial contractile function thereby preventing heart failure. During the first decade of the 21th century, several clinical trials have been conducted using as a cell source skeletal myoblasts, adipose tissue stem cells and different fractions of hematopoietic s and non-hematopoietic stem cells from bone marrow. But after some optimistic beginnings, the heterogeneity of methods and results have put this practice into question by several authors. Clear controversies exist regarding the most appropriate dose of cells injected, the appropriate time for the injection and the best way to do it. At the moment, it is possible to say that different forms of injection are generally safe, but it is difficult to decide whether small improvements in ejection fraction, are reason enough to assume the risks of surgery. This has meant that currently, cell therapy in heart has been reversed to the in vitro search of the most appropriate source of cells through a more comprehensive phenotypic characterization of stem cells and induction of ex vivo cardiac phenotype previous to its administration. In parallel, new tissue engineering technologies have been proposed and the use of bio-artificial hearts, created from the ex vivo culture of cells with cardiogenic capacity on decellularized natural matrices. While these strategies are still in preclinical stages, its application as therapy is still a realistic prospect for the future.
The advent and establishment of high-performance molecular techniques since the late 90s, has also provided a major advance on the diagnosis and knowledge at the molecular level of the processes that underlying cardiovascular diseases. The identification of protein markers in the serum has been useful to diagnose effectively and quickly many patients, and thus to be able to shorten waiting times and refining treatments. In addition, many of the processes occurring in the myocardium can not be detected in any form to another level. For this reason, in order to be able in the future to have the most accurate diagnosis and therefore select the best treatment, it is necessary in the present to investigate at the basic level, the processes that underlie cardiovascular diseases.