A Case Study on the Causes of Myocardial Infarction
Introduction
This essay will describe the structure, location and function of the heart, including how oxygenated and deoxygenated blood flows through the heart. I will define myocardial infarction and identify modifiable risks that may contribute to this condition. I will explain my management of the patient mentioned in this case study.
Location, structure and function of the heart
The heart is a powerful muscular organ. The heart is located in the thoracic cavity, where it sits between the lungs in the mediastinum area, it is positioned to the left of the body’s midline. The heart consists of two separate pumps (left side and right side) that function together to send blood around every part of the body. The heart has four chambers in total and consist of two atria and two ventricles. The heart wall has three layers of tissue: the pericardium, consisting of a fibrous tissue and a serous membrane, the myocardium which is made up of cardiac muscle and the endocardium, which is a thin membrane that lines the chambers and valves of the heart. Within the right atrium there are a small group of specialised cells, known as the sinoatrial node, this is known as the heart’s natural pacemaker. The sinoatrial node causes a synchronised contraction of the heart by generating electrical impulses, forcing the atrium to contract. There is also a mass of neuromuscular tissue located in the walls of the atrial septum, known as the atrioventricular node. The atrioventricular nodes role to receive the electrical impulse sent by the sinoatrial node and hold this impulse briefly to allow for the atria to finish contracting. The contraction of the atrium causes the ventricles to fill with blood. The atrioventricular node then allows the electrical impulse through, which then generates the contraction of the ventricles, forcing the blood up into the pulmonary and aortic arteries. The hearts functions are to generate blood pressure, routing blood through the separate circulatory pathways and regulating blood supply to meet the body’s demand.
Routes of blood flow through the heart
The contraction of the atria and ventricles is caused by the sinoatrial node initiating an electrical impulse, this allows the blood to flow through the body along the correct routes. This is done via a network of arteries and veins. Deoxygenated blood returns to the heart chambers through the superior and inferior vena cava. The blood empties into the right atrium, as the atrium contract it forces the blood through the atrioventricular valve (Known as the tricuspid valve) and into the right ventricle. As the electrical impulse passes through the atrioventricular node it initiates the ventricles to contract and the blood is pushed up through the pulmonary valve into the pulmonary trunk. The valves are very important in preventing the backflow of blood. The pulmonary trunk then divides into the left and right lungs. As the deoxygenated blood passes through the lungs it becomes oxygenated, before returning to the heart. The oxygenated blood is taken from the lungs by the pulmonary veins (the only veins that carry oxygenated blood) to the left side of the heart. Filling the left atrium. During contraction of the heart the blood is forced through a valve known as the bicuspid valve and into the left ventricles, it is then forced up through the aortic valve and into the arch of the aorta. Although it is explained this way, the heart’s left and right side are synchronised. The two separate pumps ensure the effective delivery of blood to the pulmonary and systemic circulation. The heart also has its own blood supplied by the left and right coronary arteries, these branch off the arch of the aorta and take rich oxygenated blood to the heart muscle and chambers. Deoxygenated blood is then removed via the coronary sinus and returned to the right atrium. When the coronary arteries become blocked through disease or other problems, it is referred to as a myocardial infarction.
Myocardial Infarction
A myocardial infarction occurs when the coronary arteries become rapidly occluded. Damaged endothelium within the vessels, allow substances known as plaque to build up and harden. The more plaque builds up, it starts to disrupt the flow of blood by blocking the artery, or due to the plaque rupturing causing catastrophic consequences. Studies have identified seventy percent of Myocardial Infarctions are caused by a rupture of plaque. When the coronary arteries become blocked everything beyond the blockage does not receive the oxygen and nutrients it requires, causing cell death. Coronary heart disease is the leading cause of myocardial infarction, with many contributing risk factors such as, high blood pressure, diabetes, smoking, alcohol and obesity.
Modifiable risks associated with this patient that could be contributing factors
Alcohol Induced hypertension
If hypertension is left untreated it can cause complications such as cardiac failure, renal failure and stroke. The patient admits to consuming over 10 units of alcohol each day. Recent studies have shown, more than three alcoholic drinks each day is associated with increased incidence of hypertension and increased risk of cardiovascular disease. Studies have also shown that reducing alcohol intake each day to no more than one unit can reduce the risk of myocardial infarction by up to 45 percent.
Diabetes Mellitus type II
The most common cause of death in people who have type II diabetes is cardiovascular diseases, such as angina, myocardial infarction, heart failure and stroke. Type II diabetes is a condition where the pancreas does not produce enough insulin, causing high levels of glucose in the blood. It can also be due to the cells not reacting effectively to the insulin. Insulin production is vital to maintain the blood glucose level within the set point and prevent levels from deviating. Some say that diabetes cannot be reversed, but there is evidence to suggest that a healthy lifestyle and weight loss can increase the chances of remission. Most health care professionals have said, that type II diabetes is not reversible however doctors argue it is almost always reversible, simply by diet alone, mainly reducing the amount of sugar and refines carbohydrates we consume each day. A study of 65,000 people found, half who were obese were significantly more likely to have diabetes.
Obesity
It is well known that a poor diet and being overweight can influence risks to our health in many ways. Some studies show that obesity is consistently associated with increased risk of developing cardiovascular disease, this is caused by the atrial and ventricular enlargement and a disease called atherosclerosis, which is a build of plaque in the arteries causing them to narrow, this the restricts the blood flow and makes the artery easier to become occluded.
Smoking
Smoking has an effect on every organ in the body an is known to be the cause of chronic obstructive pulmonary disease, an umbrella term for a range of respiratory diseases such as emphysema and bronchitis. Smoking impairs endothelial function. The nicotine activates the sympathetic nervous system increasing heart rate and blood pressure, it also increases carboxyhaemoglobin levels in the blood, reducing myocardial oxygen delivery. If the patient was to stop smoking, within the five years his risk of myocardial infarction would be reduced by seventy percent.
Management of this patient who has suffered an inferior myocardial infarction
I would apply my personal protection equipment; I would use the DRCABCDE approach. This involves carrying out a dynamic risk assessment, identifying any dangers present. As I approach the patient, I would identify the level of response by calling out to the patient and introducing myself and ask the patient to introduce themselves. Communication would indicate the patient is alert. I would also be looking for catastrophic bleeding. I would explain what I would need to do by means of my assessment and gain consent. Next I would check for a clear and patent airway, while having considerations for cervical spine injures prior to any airway manoeuvres. I would observe for normal adequate breathing, I can do this by counting the respiration rate, looking for signs of excessive muscle use and if the patient could complete sentences easily. To establish circulation, I would feel for a radial pulse and check the patients capillary refill time, look at skin colour and identify any, cyanosis, flushed, pale or clammy appearance. I would assess a GCS score and pupillary response. I would expose and examine the chest area. These observations are done quite quickly as part of the primary survey. The initial baseline observations would be applying the pulse oximeter to obtain oxygen saturations, to apply the blood pressure cuff to the brachial artery area of the arm. I would connect the electrocardiogram leads to the patient’s limbs and chest area. While doing this I would be asking questions based around the mnemonic. This is a form of questioning to establish details on pain and a brief history.
A confirmed Myocardial infarction is time critical. As a technician, I would check for any allergies, I would administer 300mg of aspirin orally, aspirin is indicated in patients where there is clinical or ECG evidence suggesting myocardial infarction or ischaemia. Aspirin has an anti-platelet action which reduces clot formation. I would also administer Entonox which is an inhaled analgesic, for moderate to severe pain. The patient would be taken to the ambulance on the carry chair, to prevent walking and increasing blood demand to an already compromised heart. I would assist the patient onto the stretcher and apply defibrillator pads to the chest in case of cardiac arrest. I would remain calm and explain the procedures to the patient to reduce any stress. I would provide a pre-alert to the nearest hospital using the (ashice) mnemonic. I would request paramedic back up or a rendezvous point on the way in case the patient required any further interventions. I would then carry out my secondary survey, taking a blood sugar reading and a temperature and reassess the pain score. I would continue to monitor the patient and then on arrival I would hand over the patient to the receiving team. If a paramedic was on scene then the medication treatment options would be greatly increased allowing them to give additional medications such as glyceryl trinitrate, one to two sprays 400mcg per spray sublingually to dilate the arteries. They could administer 10-20mg morphine sulphate for pain relief and 4 mg of ondansetron for any nausea or vomiting. A paramedic would also be able to send the electrocardiogram to the PPCI department. Primary Percutaneous Coronary Intervention is a procedure where a catheter is inserted into the peripheral arteries and up into the coronary arteries. A dye is injected through the catheter to indicate and highlight any narrowing or blockages. Another catheter is then inserted with a balloon at the tip this is then inflated at the point of the occluded artery for a mesh tube to be inserted called a stent. The purpose of the stent is for the artery to be supported and kept open.
Conclusion
In my opinion, this case study highlighted the reason this person has suffered a myocardial infarction. It is known that age, gender, smoking, obesity and the patients ongoing medical conditions have increased his risk of myocardial infarction. The patient’s lifestyle has contributed to this outcome. The daily excessive alcohol consumption is likely to induce hypertension, smoking causing damage to the arteries, restricting them from functioning effectively and obesity caused by poor diet and poor exercise contribute to risks of diabetes type II. Many of these contributing factors can be altered or even removed from the patient’s lifestyle to reduce the cardiovascular risks.
