Introduction
Myocardial ischemia is an injury that arises when there is an obstruction to the flow of blood to the heart muscle (myocardium), either by absolute or partial blockage of a coronary artery. This blockage is usually a result of thrombosis or a build-up of coronary plaques (atherosclerosis). Also known as cardiac ischemia, this pathology can damage the heart muscles or lower their ability to pump blood; therefore, the heart has a limited blood supply. Cardiac ischemia can result in abnormal heart rhythms, and a severe and sudden case can cause a heart attack (8). The metabolic and ultra-structural changes induced by myocardial ischemia result in irreversible injury. Infracts can evolve from sub-endocardium to sub-pericardium within four or fewer hours. Several processes influence this evolution and the timely return of blood supply (reperfusion) to tissues produces a more significant amount of rescue of the myocardium and a component of reperfusion injury (8). Reperfusion and preconditioning can help regulate the response of the myocardium to ischemic injury.
Etiology of Myocardial Ischemia
Etiology refers to the origin or causes of a disease or abnormal condition. Atherosclerosis is responsible for the majority of acute coronary cases (ACS). The oxygen amounts the heart muscle receives are lowered following a decrease in the blood supply to the heart through one or more coronary arteries (6). As the blood vessels become blocked over time, this leads to the gradual development of myocardial ischemia. Several conditions are the root of the development of myocardial ischemia; such as;
Atherosclerosis
Atherosclerosis is a coronary infection which upshots from the accumulation of substances such as cholesterol on the artery’s walls, forming plaque. Plaque narrows the blood vessels leading to a low blood flow velocity. Oxygen is transmitted to the heart in blood. Hindrance to the normal flow of blood lowers the supply of oxygen to the tissues of the heart. A limited oxygen supply to the heart muscles causes necrosis. A person suffering from atherosclerosis in the heart’s arteries may exhibit symptoms like pressure (angina) and pains in the chest area. Angina is the most common cause of cardiac ischemia.
Blood Clots
The development of plaque on blood vessels causes their narrowing, leading to an obstruction of blood that moves to the heart. In some cases, the plaques rupture, leading to blood clots which also hinder the supply of oxygen to the heart tissues. An artery blockage resulting from a clot often causes sudden myocardial ischemia to a heart attack.
Coronary Artery Spasm
Coronary artery spasm is the rarest cause of myocardial ischemia. It is the short-term tightening of the artery walls, which may decrease or even stop blood flow to the heart muscles, which happens for a short period. In addition to this, several factors increase the risk of contracting myocardial ischemia. These factors include; high blood pressure, obesity, both type 1 and 2 diabetes, and effects of tobacco, either through active smoking and long-term exposure to passive smoking. Other agents comprise a lack of physical exercise, high levels of triglyceride in the blood, and a large waist circumference.
Demographics of Cardiac Ischemia
According to the National Library of Medicine, statistics show that myocardial ischemia is a worldwide leading cause of disabilities and death, responsible for one-third of the deaths. According to a study conducted in 2017 about the illness, about 126 million (1655 per 100000) individuals were affected (2). Approximately 9 million deaths were linked to ischemia in the same year, making it the highest mortality cause worldwide. Ischemia has been causing the highest number of fatalities for two decades now (2). The disease is highly prevalent in central and eastern Europe regarding regional distribution.
Distribution based on sex shows that the male gender is at a higher risk of contracting ischemic heart disease. Per 100,000 cases, the prevalence of men was found to be 1786, which is higher than 1522 in women. During the study, this trend was made across all age groups. In men, the onset was also found to be earlier than in women. Cases of ischemic heart diseases were on the rise from the fourth decade onwards, thus reviewing age as a risk factor.
Symptoms of Myocardial Ischemia
Some patients do not usually display symptoms. This condition is called silent myocardial ischemia, whereby one does not experience any pain or symptoms. Silent myocardial ischemia can cause a sudden heart attack or even a stroke. However, some people do experience symptoms. The main sign of cardiac ischemia is angina. Angina is a chest pain predominantly on the left side of the body, resulting from reduced blood flow to the heart (3). Angina is also characterized by pressure, squeezing, and tightness in the chest area. There are also other symptoms though rare; they are occasionally observed in older people, women, and people with prevailing conditions such as diabetes. These include shortness of breath when someone is physically active, unexpected sweating, irregular heartbeat (faster than normal) and stomach upsets. Additionally, there are instances of pain in the neck, arm, shoulder, or jaw; and feeling tired or fatigued.
Diagnostic Pathways of Cardiac Ischemia
Although there are several ways of motoring cardiac ischemia, some patients tend to suffer heart attacks without showing any signs and symptoms. Silent ischemia is discovered when someone undertakes a stress test for a different reason, for instance, cardiovascular disease risk. The doctors initiate the diagnosis by inquiring about the medical history and conducting a physical examination of the patient (5). Subsequently, the doctor may recommend various techniques to aid in detecting cardiac ischemia. These recommendations include:
Stress Test: A stress test involves monitoring heartbeat or rhythm, breathing, and blood pressure as a patient engages in physical activity. Engaging in physical exercise causes a faster and harder heartbeat than usual; hence, a stress test can detect any heart complications that wouldn’t be noticeable otherwise.
Electrocardiography: Electrocardiography is a simple test conducted to check one’s electrical activity and rhythm of the heart. It involves positioning sensors with electrodes on a patient’s chest to detect the heart’s electrical signals. Some changes in the heartbeat, which are indicated by the electrical signals, could be a sign of heart complication.
Cardiac Computed Tomography (CT) Scan: A cardiac CT scan is used to check the presence of any calcium build-up in the coronary arteries. A build-up of calcium is a sign of coronary atherosclerosis, the leading cause of cardiac ischemia.
Echocardiography: Echocardiography is more reliable in the detection of cardiac ischemia than electrocardiography. It involves directing sound waves to the patient’s heart from a wand-like device held to the chest (7). During echocardiography, video images from the heart of the patients are generated and assist in the examination of any changes in the heart and any abnormal pumping of blood. A blood test may also be carried out to identify vital health indicators such as blood sugar, cholesterol levels in the blood, and the functioning of the kidney. Unstable patients with cardiac risk factors undertaking surgery should be suspected of having myocardial ischemia (7). The accuracy of myocardial ischemia diagnosis can be boosted by using additional invasive monitors. It is necessary to follow up on any suspected cases using the measurements of a cardiac enzyme (troponin).
Treatment/Management of Myocardial Ischemia
The appropriate treatment for myocardial ischemia depends on factors such as pre-existing health conditions, age, personal preferences, and the risk of heart disease. Some patients experiencing angina can be treated by a non-invasive plan known as improved outer counter-pulsation (1). This therapy aids in the reduction of the patient’s chest pains. External counter-pulsation is, however, not advised for patients suffering a severe heart attacks and peripheral artery diseases.
Cardiac ischemia treatment calls for the enhancement of the flow of blood to the heart tissues or muscles. This includes admission of medications such as nitrates, which widen arteries, ensuring a smooth flow of blood to and from the heart. Also, Aspirin is a blood thinner and reduces the blood clotting risk; Angiotensin-converting enzyme inhibitors aid in lowering the blood pressure and relaxing blood vessels (4). Myocardial ischemia can also be managed by the intake of medications that lower the material (cholesterol) that builds upon the walls of the coronary arteries. Suppose myocardial ischemia is identified timely in the intraoperative phase before the surgical incision. In that case, the surgery can be held on first and the patient can be stabilized by enhancing the oxygen supply. In the event that the operation cannot be avoided, it can be carried on as the coronary blood flow and oxygen delivery is improved.
Cardiac Ischemia sometimes calls for more-aggressive treatment methods to revamp the flow of blood. The choice of these invasive procedures depends on the number of arteries involved, the location of the blockages and their dominance (1). These include carrying out surgical interventions such as angioplasty which is a procedure carried to open blocked arteries by inserting a thin tube to the narrow part of the blood vessel. A tiny balloon attached to a wire is then inserted and inflated to widen the artery. A circular stent is then inserted into the blood vessel to keep it open.
Trans-myocardial laser revascularization and a gastric bypass on the coronary artery are invasive procedures that also aid in the restoration of blood flow. Gastric bypass open heart surgery is usually used for patients with many narrowed coronary arteries and those with diabetes. It involves the creation of a graft through which blood can flow around the impaired artery. The graft is made from vessels from other body parts. In some cases, the doctor may combine angioplasty and open-heart gastric bypass procedures to come up with a more effective treatment. Regeneration of the damaged tissues and restoration of the flow of blood to the heart is crucial to achieving a cure for myocardial ischemia.
Conclusion
In conclusion, myocardial ischemia is a leading cause of death worldwide. This pathology can be managed by living a healthy lifestyle that involves maintaining an average weight, consuming foods with low amounts of cholesterol, avoiding smoking and exercising regularly. More effort should be in research to develop optimal treatment and prevention of perioperative myocardial ischemia.
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