Human biology - Research Paper Example

Human Biology Clinical Situation: Mr. H. has a history of coronary artery disease. Immediately after eating, he experienced moderate chest discomfort that radiated to his left shoulder and descended into the left arm and the little finger. The pain was unrelieved by nitroglycerin tablets, so he was admitted to the hospital for further evaluation. A cardiac catheterization revealed a partial blockage of four coronary arteries, and he was scheduled for bypass surgery. Discuss the consequences of decreased coronary blood flow on myocardial function; a description of cardiac catheterization, and a description of the bypass procedure (CABG, coronary artery bypass graft).

The Consequences of Decreased Coronary Blood Flow on Myocardial Function The consequences of decreased coronary blood flow are influenced by the quantum of reduction in blood flow and the duration of the reduced blood flow. Decreased coronary blood flow results in oxygen deprivation to the heart muscles and when this disruption is slight the consequence is impairment in the relaxation of the heart muscle and weakened contraction, as experienced in the case of angina pectoris. This decreased blood flow may be transient, which is reversible through the use of nitroglycerin tablets.

However, when the ischemia due to reduced coronary blood flow is prolonged it may lead to decreased myocardial contraction or dyskinesis that is not easily reversible and prolongs for many hours. The consequence of chronic reduction in coronary blood flow is the failure of the myocardium to contract normally termed hibernation, which may or may not result in necrosis of the myocardium. Severe blockage of the coronary blood flow results in myocardial infarction. In all these consequences due to impaired coronary blood flow substantial dyskinesis occurs, causing the rest of the myocardium to take up this extra load.

This results in hypertrophy of the unaffected portions of the ventricle (Fuster et al, 2004). Description of Cardiac Catheterization Cardiac catheterization is an invasive procedure that is conducted to evaluate blood flow to the myocardium of the heart and assess the effectiveness of the pumping of the heart. In cardiac catheterization a medical professional introduces a thin plastic tube called the catheter into an artery or vein of the arms or leg. From this site it is progressively advanced into the chambers of the heart or the coronary arteries for the required evaluation (American Heart Association, 2009).

Even though there has been continual improvement in the techniques employed in noninvasive testing of hemodynamics to provide greater accuracy, cardiac catheterization has continued to remain the accepted standard for this purpose. This reliance on cardiac catheterization stems from its ability assist in accurately measuring intracardiac pressure measurements, as well as measuring oxygen saturation in blood and cardiac output. These hemodynamic measurements are normally done along with a left ventriculogram that provides an assessment of the functioning of the left ventricle and a coronary angiogram, for which purposes cardiac catheterization is the facilitator (Olade, Safi & Badero, 2008).

Figure – 1 shows the cardiac catheterization sitesFigure – 1 Cardiac Catheterization Sites(Olade, Safi & Badero, 2008)Description of coronary artery bypass graft (CABG) CABG is an invasive surgical procedure that is one of the revascularization procedures available for enhancing blood flow into the heart for patients suffering from severe coronary artery disease (CAD). During a CABG surgical procedure a healthy artery or vein from some other part of the body is removed and grafted to the artery in which the block is present.

This grafting is done in such a manner that it allows blood flow around the blocked portion of the artery, thereby bringing to near normal the flow of blood to the heart, resulting in oxygen saturated blood being made available to the heart muscles that were deprived of the same due to the blockage. In one single CABG procedure it is possible to bypass four major coronary artery blocks. Though the number of CABG procedures done in the U.S.A exceeds 500,000, this procedure is not done on all CAD patients.

CABG may be an option in treating CAD patients with severe blocks in the large coronary arteries that contribute to a major proportion of blood supply to the heart muscles, particularly when the pumping action of the heart has been deteriorated considerably, and also in cases where angioplasty is not considered a suitable intervention option in CAD patients (National Heart Lung and Blood Institute, 2007). Literary References American Heart Association. (2009). Cardiac Catheterization. Retrieved November 5, 2009, from Web Site: http://www.

americanheart.org/presenter.jhtml?identifier=4491 Fuster, V., Alexander, R. W., O’Rourke, R. A., Roberts, R. King, B. S., Nash, I. S. & Prystowsky, E. N. (2004). Hurst’s, The Heart- Volume -1. Eleventh Edition. New York: McGraw-Hill Professional, pp.697-750.National Heart Lung and Blood Institute. (2007). What Is Coronary Artery Bypass Grafting? Retrieved November 5, 2009, from, National Institutes of Health, U.S. Department of Health & Human Services Web Site: http://www.nhlbi.nih.gov/health/dci/Diseases/cabg/cabg_whatis.

html Olade, R. B., Safi, A. & Badero, O. J. (2008). Cardiac Catheterization (Left Heart). Retrieved November 5, 2009, from, emedicine, WebMD Web Site: http://emedicine.medscape.com/article/160601-overview