Comparative Randomized Single-blind Trial of Amiloride in Coronary Heart Disease

The Problem: Treatment of Cardiovascular Diseases (CVD) is a major health care problem across the entire word, and particularly in the United States, Japan and European Countries (1). In fact, these life-threatening disorders are a major cause of emergency medical care and hospitalization in the United States, and according the National Center for Health Statistics (NCHS) there were approximately 1,565,000 hospitalizations for primary or secondary diagnosis of an acute coronary syndrome (ACS), 669,000 for unstable angina (UA) and 896,000 for myocardial infarction (MI). In the 2003, NCHS reported 4,497,000 visits to emergency departments for primary diagnosis of CVD, wherein the average age of a person having a first heart attack is calculated at 65.8 years for men and 70.4 years for women (2)

Although the treatment of angina, chest pain secondary to coronary heart disease (stable chronic angina) and one of the most common and early symptom of Coronary Heart Disease (CHD) can be tracked as far as 1880's, it still represents a medically unresolved problem. Indeed, treatment of angina in particular, as well as associated condition as ACS, UA, and MI, involves a large number of life-style recommendations, dietetic advice, drugs, coronary artery intervention, or coronary bypass surgery aimed to improve symptoms, quality of life of patients, and even primary or secondary prevention of the stable chronic angina. Unfortunately, despite a century of medical advances and epidemiological studies, the current approach to CVD and coronary heart disease remain complex, and at times frustrating.

Among the proposals to treat stable chronic angina new aspects have been considered, including the single "polypill" agent (aspirin + statin + 3 blood pressure lowering agents in half dose, and folic acid), Simvastatin and intravascular ultrasound study, or intra-coronary angiogenesis therapy (3-5). However, most of them are unpractical, whereas it is difficult to determine whether these changes will translate to meaningful reductions in clinical events, or whether results in highly selected patient populations can be matched to the real-world of prevention and treatment of coronary artery syndromes.

Further, a recent large clinical trial, COURAGE study (6), conducted in 50 hospital centers in the United States and Canada showed that optimal drug treatment and percutaneous coronary interventions for stable coronary heart disease, was not more effective than optimal medical therapy alone for preventing cardiovascular events, hospitalization or death, suggesting that drugs, surgical procedures or both were not a statistically effective solution for stable chronic angina. By inference, a therapeutic approach for mot severe coronary syndromes as UA, post- myocardial infarction angina, or aggravated angina episodes, seems to be a more distant goal.

Physiological Basis for Innovation: For more than a century, the extremely rapid coupled tissue O2/CO2 gas exchange and ion H/K transport by Hemoglobin (Hb) in red blood cell (RBC) has been well known for scientific community, the so-called Bohr/Haldane Effect (7). Since then, it has been noted and confirmed that RBC have a critical role to maintain normal vascular function, blood flow and tissue oxygenation and acid-base regulation. These functional roles of RBC include a nitric oxide (NO) transport, NO synthetasa, and regulation of platelet aggregation, vascular rheology, and endothelial function (8). Indeed, recent studies have demonstrated that erythrocyte serves as a regulator of vascular tone and tissue perfusion, whereas the hemoglobin and RBC itself may be sensors for the oxygen tissue requirement (9).