Comment

Discussion #1

There are many different risk factors associated with myocardial infarction (MI) or heart attack. Risk factors that are uncontrollable are age, gender and heredity (American Heart Association, 2018). Risk factors that are modifiable are smoking, high cholesterol, blood pressure, obesity and sedentary lifestyle (American Heart Association, 2018). Other risk factors are diabetes, alcohol and stress (American Heart Association, 2018). Although many of these risk factors are preventable, approximately 370,000 people in the US experience an MI annually (Samoraphop, Zahrli, & Hisako, 2018).        Mr. Smith’s injury was a result of hypoxia. Hypoxia develops when there is a lack of oxygen (McCance & Heuther, 2014). A common type of hypoxia is ischemia, which is usually caused by a narrowing or blockage of arteries (McCance & Heuther, 2014). The effects of myocardial ischemia become irreversible and causes necrosis after about twenty minutes (McCance & Heuther, 2014). The most common type of myocardial ischemia is caused by arteriosclerosis which is a gradual narrowing of the arteries induced by plaque build-up (McCance & Heuther, 2014). Mr. Smith’s angiography and requirement of the usage of IV clot dissolvent supports this analysis.         Reversible cell injury is capable when oxygen is supplied back to the cell within a certain amount of time. Irreversible is when the cell has structural changes, mainly damage to the nucleus and has become necrotic (McCance & Heuther, 2014). Rather a cell’s injury is reversible or irreversible depends on factors such as length of time the damage has taken place and the type of damage. Cells can also adapt to damage and still remain functioning (McCance & Heuther, 2014).         The pathophysiological changes that occur to the heart during an MI can be detrimental, it is important to ensure quick diagnostic confirmation of an acute MI to prevent further complication and death. Within 1 minute the heart becomes pale and is not able to contract as efficiently (McCance & Heuther, 2014). In 3-5 minutes. the section of the affected heart stops contracting this causes mitochondria oxygenation to decrease which decreases the production of ATP (McCance & Heuther, 2014). Cellular swelling begins along with the loss of integrity to the plasma membrane (McCance & Heuther, 2014). With the integrity of the plasma membrane compromised the sodium-potassium pump and the sodium-calcium exchanges fail resulting in cellular death if oxygen supplies are not returned (McCance & Heuther, 2014).         Subjective findings for MI are patient complaints of shortness of breath. Chest pain can be described as having severe pain or as though a lot of pressure is “sitting” on the chest (McCance & Heuther, 2014). Some patients complain of nausea and vomiting along with pain described as “shooting” in jaw or left arm (McCance & Heuther, 2014). Objective data for diagnosis of an MI are EKG findings and cardiac enzyme results (McCance & Heuther, 2014).

Discussion #2

Coronary heart disease (CHD) is one of the leading causes of death and accounts for nearly 25% of all deaths in America (McCance & Huether, 2014, p. 171).  Myocardial infarction (MI) results from decreased blood supply to the heart that causes damage to heart tissue from an inadequate supply of oxygen (McCance & Huether, 2014, p. 171).  There are two types of risk factors associated with CHD and MI: non-modifiable and modifiable.  Conventional or non-modifiable risk factors consist of demographics such as age, gender, and family history (McCance & Huether, 2014, p. 1149).  The modifiable risk factors associated with CHD include conditions such as dyslipidemia, hypertension, diabetes and insulin resistance and lifestyle factors such as smoking, obesity, diet, and activity level (McCance & Huether, 2014, p. 1149).

In the provided case study, Mr Smith has sustained ischemic cell injury.  Ischemic cell injury is categorized by lack of oxygen, through reduced blood supply, that causes the destruction of the cell structure and the cell membrane (McCance & Huether, 2014, p. 55).  The lack of adequate oxygen is called hypoxia, the most common cause of ischemia, and is the number one cause of cellular injury (McCance & Huether, 2014, p. 56).  Hypoxia results from a reduction in oxygen that can be related to a number of conditions including anemia, respiratory disorders, and cardiovascular diseases (McCance & Huether, 2014, p. 56).

Cell injury can be either reversible with the possibility of recovery or non-reversible that results in cell death.  Reversible cell injury responses include loss of adenosine triphosphate (ATP), cellular swelling, ribosomal detachment, and autophagy of the lysosomes (McCance & Huether, 2014, p. 55).  Irreversible cell injury is called the “point of no return” and is considered a biochemical puzzle due to the exact mechanism of action responsible for the cell’s transition from reversible to non-reversible remaining undecided (McCance & Huether, 2014, p. 55).  Factors exist, such as nutritional status, that play a role in the cell’s ability to recover and to the extent of damage that occurs from the injury (McCance & Huether, 2014, p. 55).

The pathophysiological changes that occur during an MI began less than one minute after reduction of myocardial blood supply (McCance & Huether, 2014, p. 58).  Cardiac cells are able to survive ischemic conditions for approximately 20 minutes prior to cell death however ECG changes are visible as early as 30-60 seconds after hypoxia occurs (McCance & Huether, 2014, p. 1160).  Immediately after reduced blood flow the affected myocardial tissue becomes cyanotic and all oxygen reserves are used rapidly leading to the use of anaerobic metabolism (McCance & Huether, 2014, p. 1159).  The use of glycogen as an energy source is inadequate to meet the total energy requirements of the myocardium resulting in acidosis from electrolyte imbalances (McCance & Huether, 2014, p. 1159).  These imbalances make the myocardial tissue vulnerable to the effects of lysosomal enzymes, which further reduces the contractile function and impulse conduction and leads to heart failure (McCance & Huether, 2014, p. 1159).

As ischemic damage occurs, the first symptom is typically acute, sudden onset of severe chest pain that has been described as heavy and crushing, like there is “an elephant on my chest”, with radiation reported to the jaw, neck, back, shoulder, and left arm (McCance & Huether, 2014, p. 1160).  Some reports of atypical presentation of MI, usually associated with the elderly or those with diabetes, include no pain, nausea and vomiting, or uncontrollable indigestion (McCance & Huether, 2014, p. 1160).  Objective changes that can be observed include a temporary increase in heart rate (HR) and blood pressure (BP) as the body attempt to compensate, abnormal extra heart sounds resulting from left ventricular dysfunction, cardiac murmurs related to valvular insufficiency, respiratory congestion including percussion that is dulled and inspiratory crackles at the lung bases, and skin that is cool and clammy as the result of peripheral vasoconstriction (McCance & Huether, 2014, p. 1160).