What is a heart attack?
A heart attack is a term employed to describe a sudden occlusion or blockage of a major blood vessel supplying the heart. There are various symptoms that one can experience during a heart attack. These are mostly described as chest pain, chest ache, chest tightness, a heavy weight on the chest or even indigestion (heart burn). Of note, these symptoms are brought on by exertion although they can occur at rest especially during the early hours of the day and in cold weather. More importantly, indigestion brought on by a heart attack is almost universally accompanied by shortness of breath and worsened with physical exertion. On the contrary, indigestion brought on by food is not associated with breathlessness and has a clear relation with food intake.
The initial moments in a hospital during a heart attack can be extremely daunting and tense. Having to breathe on high-flow oxygen, experience excruciating chest pain, be looked after by complete strangers and face a barrage of questions. Importantly, approximately two-thirds of admissions as a result of a heart attack are first time presenters (they have no previous cardiac history). In such a situation having some idea of what to expect could be extremely useful.
Is heart attack common?
Most of the data regarding cardiovascular disease are available from the developed countries. This is due to decades of meticulous and dedicated research. For example, cardiovascular disease causes 208,000 deaths annually in the UK with nearly half of these due to heart attacks. Similarly, it affects both sexes with 1 in 5 and 1 in 6 deaths attributed to heart attacks in males and females respectively.
What leads to a heart attack?
The heart is an organ mostly made of muscle. On an average it contracts 2.6 billion times in a lifetime to allow uninterrupted blood flow to the body. To achieve this remarkable feat, the heart has its own dedicated blood supply via two major blood vessels also known as the coronary arteries. It is a known fact that the inherent property of blood is to clot (a property mainly exhibited by special cells called platelets and associated clotting factors). Therefore, to prevent this, all blood vessels have a smooth lining which allows the blood to flow without much resistance or stagnation.
However, with time, cholesterol deposition (known as plaque formation) occurs in the walls of blood vessels and the lumen of the coronary arteries gets progressively narrowed. This phenomenon if allowed to continue unabated, can lead to the marked narrowing of a vessel lumen. Interestingly, the plaque size does not predict the behaviour of these culprit lesions and in fact, it is the composition of these plaques that determines outcome. The plaque consists of a soft necrotic core containing cholesterol and debris which is surrounded by fibrous tissue and other immune cells of the body. Once this soft core ruptures, it presents a ‘clot-friendly’ surface leading to the rapid occlusion of the blood vessel. In other words the larger or more unstable the soft necrotic core in a plaque, the higher the risk of plaque rupture and a subsequent heart attack. The part of the heart supplied by this blocked artery is deprived of its blood supply and in the absence of any treatment, dies. This process of muscle death leads to the pain associated with a heart attack (see Figure 1).
What are the risk factors for developing a heart attack?
- Age >75 years.
- Male sex up to the age of 65 years.
- History of tobacco
- Elevated blood cholesterol levels.
- High blood pressure.
- Diabetes mellitus.
- Previous stroke.
- Poor circulation elsewhere, for example legs.
- Family history of premature heart attacks (<65 years of age).
- Ethnicity (South Asians have an estimated 50% increased risk of developing heart attacks in comparison to Caucasians).
- Central obesity (increased waist/hip ratio).
- Sedentary life-style.
- Excessive alcohol consumption.
What will happen in the initial moments after I am admitted with a heart attack?
You will most likely be wheeled off to a chest pain bay in the emergency department or straight to the cardiac unit. You will receive high-flow oxygen through a mask and will be attached to a cardiac monitor to keep a close watch on the rhythm of your heart. Following this you will have an electrocardiogram (ECG) which is an electric recording of your heart. It is crucial that this is done in the first few moments of your arrival. This ECG will be looked at by the attending health care professionals (doctor and nurse) as your future treatment will be dictated by it.
What could the ECG possibly show?
The ECG could show one of three things.
- It is normal in which case you will most likely have some pain relief followed by a blood test. This will test for the level of an enzyme called troponin in your blood. If present it may suggest a small heart attack in which case you will most likely need further investigations such as an echocardiogram and coronary angiogram (these will be explained in subsequent columns). If the troponin is within normal limits then you could have a test called an exercise tolerance test (ETT) either within the same admission or at a subsequent visit.
- The ECG suggests partial blockage of one or more of your arteries. It is important to realize that an ECG is an attempt to map the electric activity of your heart in a three dimensional manner. This can be affected by blocked arteries can therefore give clinicians clues as to where the culprit lesion It is by no means the gold standard test to characterize the extent or location or the narrowing in a culprit blood vessel.
- Finally, the ECG may suggest an acute and complete blockage in an artery.
What treatment should I expect to receive?
The treatment strategies are quite similar in the initial approach. You will be given oxygen, pain relief in form of morphine and nitrate tablets or spray followed by a drip. Furthermore, it is vital to administer blood thinners such as aspirin and clopidogrel in cases of suspected heart attacks very quickly. These blood thinners prevent clot formation by inhibiting platelets in our bodies. These are special cells that participate in clot formation and subsequent blockage of a blood vessel.
Following this initial period, the treatment arms separate. In case of a complete blockage of a blood vessel, a ‘clot busting’ drug is given as an infusion or even a slow injection. This procedure is called thrombolysis. This treatment modality has been in the armamentarium of cardiology for nearly three decades. At this point the attending physician will go through a whole list of potential contraindications with you to make sure that this is a safe option for you. This is because this treatment carries with it a 3% risk of major bleeding and is contraindicated in some cases for example, recent surgery, head injury or active cancer.
More recently, in many countries worldwide patients are rushed to a cardiac catheter lab as an emergency to receive primary percutaneous coronary intervention (primary PCI) during which an emergency angioplasty is performed with stent insertion to unblock the coronary artery. This is the gold standard treatment option in such situations. Dr Omar Rana provides this treatment at Omar Hospital & Cardiac Centre which is a heart attack centre in Lahore.
Will I be sent home following this initial treatment?
It is likely that you will be in hospital for at least 5 days. You may need further tests such as an echocardiogram to look at the structure and pumping action of your heart. This may be followed by coronary angiography which is an ‘X-ray test’ to look at the blood vessels of your heart (see Figure 2). These will be explained in subsequent columns.
The aim of these tests is risk stratification and addressing the need for further treatment in case of blocked arteries. This could involve angioplasty and stent insertion or even coronary artery by-pass grafting.
Figure 1. Plaque rupture leading to clot formation and the total occlusion of a coronary artery resulting in myocardial infarction (heart attack) and subsequent muscle death.
Figure 2. Coronary Angiogram
In most situations a small hole is made in the groin and a catheter is advanced to the heart. It engages the arteries of the heart after which radio-active dye is injected and images acquired through the X-ray tube and seen on the screen.