7. Pre-hospital heart attack (Acute coronary syndrome) – July 2015
Chest pain is a concern for one major reason. Within the chest are important organs critical to life. Any problem within the chest has the potential to be significant and so any warning sign should be considered seriously. The major structures within the chest are the heart, the great vessels aorta and vena cava and the lungs. There is also the chest wall itself which is an important distinction when assessing chest pain.
The first distinction when assessing the patient with chest pain is visceral versus parietal or, in other words, inside organ versus the outside chest wall. The chest wall is the protective structure covering the organs within. This presents quite differently to the organs if there is a problem. This difference can provide useful clues when assessing the patient with chest pain.
The chest wall itself is well supplied with nerves that originate from the spinal cord. It is important to know where any contact with the outer body is made and the seriousness of that contact. Any threat to the body allows a chest wall supplied with nerves to immediately let the brain know where and what that threat is and to provide a protective response.
The nerves to each part of the chest wall lead back to one specific part of the spinal cord. As such, the body can identify exactly where it is being touched and with what. Chest wall pain will present as one that can be well localised by the brain to where the problem is. One finger can be used to pinpoint where the problem is. The pain will be clear in its description being sharp, stabbing or knife like right at the point of where it can be felt. Because it is the chest wall, the pain will have a clear relationship to any movement of the chest wall. Typically the act of deep breathing will make the pain worse.
Three questions to ask the patient with chest pain early are:
Show me where the pain is? If the patient can show you with one finger located to one small area this is consistent with chest wall pain.
What does the pain feel like? If the patient says sharp, stabbing or knife like then this is also consistent with chest wall pain.
Does taking a deep breath change the pain? If the patient grimaces and states it hurts a lot to take a deep breath then this too is consistent with chest wall pain.
If all three answers are suggestive of chest wall pain then that is likely the cause. If however one or more of the answers differs from this presentation then this may not be chest wall pain at all. Instead, it may be organ pain, specifically pain that is cardiac in origin. Certainty must be had that the pain is clearly chest wall or else default to cardiac until proven otherwise.
The heart has a different nerve supply to the chest wall. The body does not need to have the fine awareness of problems with organs that it has with the chest wall. The heart has a much smaller supply of nerves. Importantly the nerves from the heart do not lead back to one specific spinal cord segment but to several of them making it difficult for the patient to be able to locate where the problem is.
Cardiac pain presents as poorly localised instead of well localised. It will take the patient one hand to show where it is rather than one finger. Unlike chest wall pain it is difficult for the patient to describe cardiac pain so many descriptions are possible. A variety of terms are used including heavy, burning, crushing, indigestion and aching. The pain may still be described as sharp or stabbing. Cardiac pain may have very unusual descriptions. Because there is no chest wall involvement cardiac pain will not have any clear association with breathing.
Importantly in assessment, questions seek to work out if the pain is clearly chest wall. This is known as pleuritic pain because the pleura is the nerve rich lining of the chest wall. First responders are not trying to work out if the pain is cardiac though this is a common misconception. Chest pain is assumed to be cardiac out of hospital unless clearly pleuritic.
Rule number one: When uncertain, the assumption is the pain is caused by an organ and not the chest wall. The safe assumption is always that chest pain is cardiac until proven otherwise.
Rule number two: No matter what the patient describes, if they have had this before and it is already diagnosed as cardiac this must also be considered cardiac.
Rule number three: Cardiac pain can vary in description but should not sound like clearly chest wall pain. It can be aching, burning, heavy, squeezing, crushing, like indigestion to list the more common. It can even be sharp. The pain can be in the middle of the chest, below the sternum or right across the chest. It can radiate to one or more arms, the neck, the back or jaw. Recall that the nerves to the heart do not accurately tell the body where the problem is and so leaving the brain confused. Importantly, cardiac pain does not get significantly worse on deep inspiration. Chest pain is cardiac pain unless proven otherwise as already discussed.
Women and cardiac disease: Women can be the exception to these rules. Menstruation actually works to provide some protection from coronary artery disease forming. As such it often presents later in life and in smaller arteries than men. This means it can present differently to men. Great benefit of the doubt must be given to women when cardiac disease is a possibility. There may be no pain and only other associated signs and symptoms instead.
Ultimately electrocardiograph (ECG) and blood analysis looking for content of dying heart cells in the blood is the only way to be certain. This is not available to pre-hospital responders. There are only two other assessment items of importance at this point.
If the pain onset was from to a trauma mechanism then the pain is not cardiac. Ask the patient what they were doing when the pain started. If they were watching television or eating dinner or had been packing shelves yesterday then this is not clearly traumatic in origin. If however the patient fell against a kitchen bench or was involved in a car accident with the steering wheel striking the sternum and now has pain at the point of impact then there is a traumatic origin. It is very likely this pain will present as chest wall pain anyway.
The last way a pre-hospital responder can consider chest pain is not cardiac is if the pain is already diagnosed. Ask the patient if they have had exactly this pain before and if it has been diagnosed. If a diagnosis has already been provided verified by proper medical testing and this pain is exactly the same then that diagnosis can be used. The diagnosis may be cardiac anyway. The diagnosis must be proper medical and not simply an opinion. Where there is any doubt the default position must be back to assuming the cause of the pain is cardiac. Alternatively the diagnosis may be something else such as disease of the gall bladder, gastrointestinal tract or pancreas. Only treat as not cardiac if this pain is exactly like the previous diagnosed pain.
Coronary artery disease: Blood flow is essential for all cells to receive oxygen and nutrients and to remove waste. Just as with the brain and stroke, the blood supply to the heart can be reduced or even stopped due to disease within the coronary arteries. This interruption to blood supply results in cardiac ‘ischemic’ pain from coronary artery disease (CAD).
CAD is typically progressive. Over time cholesterol and fat deposits attach to the walls of the coronary arteries. These damage the walls of the arteries injuring them. These small injuries are wounds and so small blood clots occur to heal them. As they heal, new lining in the blood vessel covers the wound but now there is a lump. Blood flow can further damage this new covering and more deposits can become attached causing a new wound cycle.
This cycle repeats over many years with the artery eventually narrowing to the point where problems arise. The original deposit never fully goes away with repeated attempts to cover it up inside the blood vessel with a new lining. This lining is what is injured each time causing the wounds. Each time this repeats the blockage gets bigger than before. Problems include angina and myocardial infarction and are collectively known as acute coronary syndrome.
Angina: Cell needs at rest compared with during exercise are very different. When the coronary artery becomes partly occluded and any increased need cannot be met then supply of oxygen does not meet demand. This is a common medical problem called angina.
Usually angina is predictable. Symptoms present with particular exercise or activities. Likewise, the symptoms can typically be relieved with rest and sometimes use of anginine (glyceryl trinitrate) medication.
Depending on where the partial blockages are, angina can be treated with diet changes, medications including for cholesterol, hypertension and diabetes and of course specific medications to manage angina. Cholesterol and fat are implicated in the wall damage process, high blood pressure increases the likelihood of injury occurring to the vessel wall as does the extra sugar from diabetes. These are known as risk factors.
There may be more invasive interventions possible. These include coronary artery bypass surgery that involves grafting a replacement blood vessel, usually taken from somewhere else in the patient, from one side to the other around the blockage. Stents are thin tubes placed inside the artery that force the vessel to reopen. Angioplasty is known to many patients as ‘the balloon’ because a small balloon is placed into the blockage and inflated to force it open again. These are all done within cardiac laboratories. All of these options seek to reopen or provide alternative pathways for blood supply.
Angina is said to be ‘unstable’ if it is no longer predictable and its symptoms easily managed. This can happen as the artery becomes progressively more blocked. When it changes like this causing acute problems, it becomes part of acute coronary syndrome.
Importantly, pre-hospital responders do not ‘diagnose’ angina. This will be a diagnosis already given to the patient by a doctor. All episodes of chest pain, particularly first presentations, are treated as myocardial infarction or ‘heart attack’ until proven otherwise.
Myocardial infarction: Known to many as a ‘heart attack’, myocardial infarction occurs when the partial blockage that causes angina increases to effectively blocking the artery completely. This can follow a history of angina and only needs the addition of a small new clot. Alternatively the clot that forms may be very large and be the first sign of any heart problems.
Unlike angina, myocardial infarction is not easily reversible and can leave a part of the heart muscle without any blood supply at all. Part of the heart muscle will die if this blood supply is not reopened. Methods to reopen the blocked artery have urgency with patients suspected of having an acute myocardial infarction time critical. Early situation reports from first responders and provided to the receiving hospital to allow them to prepare along with transport to a hospital capable of providing acute cardiac care is important.
Recall that part of the new occlusion is a new blood clot forming at the site of an existing wound within the coronary artery. A blood clot is the normal response to heal a wound within the body. Once the wound is healed the clot is no longer required. The body has a process called ‘lysis’ where the old clot is basically dissolved and removed. Medical intervention is able to exploit this process to remove the clot that is blocking the artery by mimicking this.
Thrombolysis is the therapy of injecting a ‘clot dissolving’ drug into a patient having an acute myocardial infarction to remove the clot before the body would naturally be able to do it. This has proven to be very effective and is offered as early as possible to many patients who are not near to major cardiac care hospitals. The sooner the drug is administered the more heart muscle can be saved. It is now being considered as a pre-hospital drug for paramedic use.
Associated signs and symptoms: When troubled, the body can respond with more than just the sensation of chest pain. Nerves that supply the heart can also trigger nausea and vomiting. Part of the nervous system stress response is the patient becoming pale and clammy. This is largely due to vasoconstriction and is part of the so called ‘fight or flight’ response. All of these support the belief there could be a serious cardiac problem.
Another significant symptom of a cardiac problem is shortness of breath. There may be also be visible respiratory difficulty. Lack of blood to the heart arteries may cause the feeling of breathlessness. Worse, a diseased heart may not be able to effectively circulate enough blood through the body as it normally would. Because blood moves from the right side of the heart through the lungs back to the left side, an acute problem with the heart may cause heart failure. This could be an accumulation of blood in the lungs from inadequate heart contraction. This can cause breathlessness and respiratory difficulty. These signs and symptoms in the cardiac patient are always significant. Difficulty breathing or shortness of breath is not a normal feeling or finding. It should always be assumed that it means something significant.
The failure to effectively circulate enough blood also means maintaining normal blood pressure may be difficult for the cardiac patient. Hypotension is a serious sign the heart cannot produce an effective enough circulation for the body. Rarely is hypotension of advantage to any patient and so when found should also be assumed to mean something significant.
Finally, the normal heart rhythm may be seriously disturbed in any acute cardiac event. The normal heartbeat is made up of two very connected activities. These are the electrical impulse that stimulates the heart muscle and the heart muscle itself. Disturbance to the heart rhythm can occur if the electrical impulse is interfered with due to the acute problem. When this happens the pulse may become irregular, slow or alarmingly fast. This can make it difficult to produce a normal blood pressure. However the rhythm may be even more of a problem as some abnormal heart rhythms can be life threatening. These include abnormal racing and chaotic beating of the major part of the heart, the ventricles. The most commonly encountered of these are ventricular tachycardia and ventricular fibrillation. These are cardiac arrest rhythms that are managed using a defibrillator.
Cardiac chest pain management: The management of the patient with cardiac chest pain involves five key elements.
- Early recognition of a cardiac problem
- Helping to keep open the blocked coronary artery
- Reducing the oxygen need of the patient’s heart
- Treating pain to reduce anxiety and stress response
- Patient transfer to an acute cardiac care facility
Underlying all of this is the unbreakable rule that any problem is cardiac until clearly proven otherwise. Cardiac chest pain can present like a classic text book description or it can present most unusually. It is possible for a patient to have a heart attack without any pain at all. Some patients actually find out that they have had a heart attack on routine medical examination afterward.
Help to keep open the blocked coronary artery: The only certain way to reopen the blocked coronary artery has already been described as either more advanced in hospital therapies and/or thrombolysis. However it must be remembered that the acute problem is a new blood clot. Aspirin works to interrupt clot formation by destroying the sticky platelets that help to form strong blood clots in a normal healthy person. One 300mg chewable aspirin should be administered to all patients with acute cardiac pain. This helps to at least slow down the construction of the clot that is causing the acute problem and perhaps allow more time for the in hospital therapies to help overcome the heart attack.
This aspirin administration should routinely occur unless there is some particular reason why the patient should not take aspirin. These include past history of aspirin hypersensitivity, bleeding disorders or if the pain is thought to be due to an aortic aneurysm. Some emergency call centres advise callers to take aspirin where available even before first responders arrive.
Some patients will already be taking daily smaller regular doses of aspirin for a similar clot interfering purpose. This is a dose designed to help avoid the problems of cardiac disease and stroke without the aspirin causing gastrointestinal or bleeding problems. The fact that this smaller dose has not worked suggests that this higher one off dose is needed.
Reducing the oxygen need of the patient’s heart: The patient should rest in a semi reclined position and be given reassurance. The use of supportive communication skills and keeping the patient informed as what help is on offer to them is a good idea. Any exertion will increase the oxygen need and worsen the oxygen supply problem. The patient should not be asked to walk around or perform anything other than the lightest of tasks.
Glyceryl trinitrate (GTN or anginine) can be administered. This drug is not an analgesic drug. Instead it causes blood vessels to relax and dilate. The effect of this is that some blood is pooled in the feet. The reduced amount of blood returning to the heart means there is less blood for the heart to push around the body. Less blood to be pushed means less work for the heart to do. This in turn reduces the heart’s need for oxygen. Of course local guidelines and protocols should be followed at all times when administering any medication. The patient must be assessed for effectiveness or problems. If the GTN causes problems such as collapse or hypotension, it should be removed from the patient’s mouth as soon as practicable.
Treating pain to reduce anxiety and stress response: Pain can cause a stress response. This can make the heart beat harder and faster to circulate more blood. It can also make the blood vessels in the arms and legs constrict making it harder for the heart to push blood out. This is not helpful when the heart is being starved of oxygen. Relieving pain can help to minimise this happening. If nitrate therapy does not relieve the pain or if the pain is too severe, direct analgesia should be provided.
It is always worth administering GTN first when treating cardiac chest pain. GTN is not an analgesic but reduces pain through its beneficial actions on the heart. Inhaled methoxyflurane, intranasal fentanyl or even injected morphine or fentanyl are analgesics and reduce the ability to be aware of the pain. If the pain persists despite the administration of one or more GTN tablets then this direct analgesia should be considered. Direct analgesia is most meaningful the more severe the pain the patient is complaining of. There is little advantage in treating mild pain less than two in severity but a lot of potential advantage in treating severe pain.
GTN may continue to be administered even after analgesia is commenced. The two drugs are providing different actions. Analgesia is also most appropriate if GTN is not safe to be administered making it the only remaining option.
Oxygen therapy: Oxygen administration has long been a core part of the pre-hospital management of the patient with chest pain. This thinking has recently been challenged and oxygen is now administered guided by pulse oximetry. Where pulse oximetry is not provided as a standard part of care then oxygen therapy should be administered. Pulse oximetry is not typically a part of first responder practice and so oxygen therapy will be usual.
Patient transfer to an acute cardiac care facility: Early situation reports and notification to a receiving hospital capable of providing acute cardiac care is important. Reopening of the affected coronary artery will be most assisted when this happens. A facility capable of providing acute cardiac care is critical if re-establishing blood flow to the coronary arteries is to happen.
Jeff Kenneally www.prehemt.com
Jeff is the author of the 2014 – 2016 Ambulance Victoria First Responder clinical practice protocols and accompanying education program