Cardiac Arrest vs Heart Attack

Heart attack and cardiac arrest are terms that are often, but incorrectly, used interchangeably, or at least with poor understanding amongst non-medical people. Whilst the former is often a precursor to the latter, both are very different physiological states. Read on to understand the difference between them and what you can do in case of sudden heart attack and cardiac arrest recommended by paramedics.

Succinctly, a heart attack is an event where the heart muscle is injured or dying, yet the patient remains conscious, but may be seriously unwell; cardiac arrest is a state of unresponsiveness and abnormal (or no) breathing associated with stoppage or other complete failure of the cardiovascular system. Join a local or online first aid course for more information and to develop lifesaving skills and knowledge.

What is a heart attack?

Heart attack, classically, is crushing, central chest pain which may radiate through the arm, jaw and neck, and is associated with pale or ashen skin, profuse sweatiness and difficulty breathing. The underlying cause for this pain is an interruption  of blood flow through the coronary arteries (those blood vessels supplying the heart muscle), which leads to a build-up of chemicals around tissues of the heart. Special nerve receptors in this area detect the presence of these chemicals and signal to the brain that some form of injury or insult is occurring; the patient interprets this as pain, discomfort, tightness or similar descriptors depending on a range of unique personal factors. Pain to the jaw, arm (or arms) and neck is a symptom experienced by virtue of shared nerve pathways; this nerves detecting chemicals around the heart muscle merge with nerves receiving messages from the arm, shoulder and neck. The brain may struggle to identify where the source of the injury exists, and the patient experiences the sensation of pain in these areas despite no actual injury occurring in those parts of the body. 

An image of a man having a heart attack

What causes a heart attack?

This interruption to blood flow responsible for causing pain, may result in a number of ways, but produces similar signs and symptoms. Commonly, the interruption of is due  to an inability for narrowed vessels to supply sufficient blood flow to the heart muscle during a period of exertion. Vessels become narrowed as fatty substances form plaque inside the arteries The level of exertion required to trigger this supply/demand mismatch depends on a range of factors including the degree of narrowing of the vessels. A condition in which this supply/demand mismatch occurs on a regular basis is named angina. This situation describes the ‘stable’ form of angina which can be easily managed with rest and some basic medications; however, an ‘unstable’ form of angina occurs when coronary arteries become irritated and spasm, causing a sudden impediment to blood flow, even when the patient is at rest. 

Another way in which blood flow may be interrupted is due to formation of a clot which partially or completely occludes  the blood vessel. In this situation, the area of heart muscle which receives its blood supply through this vessel will become injured and if enough time passes, may die (infarct). In a similar way, obstruction may occur when a clot forms elsewhere in the body, breaks away from the affected vessel and travels through the blood stream, finally reaching and lodging in a vessel supplying the heart muscle. 

In these states, the patient may have an altered conscious state and a range of symptoms including low blood pressure, but there is still blood being pumped from the heart and circulated throughout the body. It is also important to understand that a person may experience a heart attack without chest pain; in these instances, according to the Australian Resuscitation Council, the most common symptom is shortness of breath.

What to do in case of a sudden heart attack?

The key management for a patient experiencing heart attack is to rest and reassure them, reducing the workload on their heart. Patients with a diagnosed or recurrent episodes of chest pain may be prescribed medications which you can assist them in administering. If you are concerned, or if the pain worsens or lasts for more than 10 minutes then call 000 and ask for an ambulance.

What is cardiac arrest?

In cardiac arrest, there is no blood pumped from the heart (or such an inadequate amount that it is undetectable and not life-sustaining), hence no blood pumped throughout the body, and the cells, including those of the brain and vital organs, are starved of oxygen and nutrients. It is not uncommon for a patient experiencing a heart attack to deteriorate into cardiac arrest, which is a symptom of the disease process, however, many conditions can lead to cardiac arrest, for instance, bleeding, respiratory distress or choking, septic shock and many others. As you can learn in greater detail through one of the Australian Paramedical College’s accredited training courses, cardiac arrest may be the result of a failure of the heart muscle to contract, failure of the electrical system of the heart to function properly, loss of significant amount of blood, or complete obstruction of one or more of the great vessels, the largest and most central blood vessels.

What to do in case of cardiac arrest?

A patient in cardiac arrest is unresponsive and not breathing normally (often, not breathing at all) and requires immediate ambulance help, CPR and defibrillation using an AED where available. Completing an accredited CPR course is a critical step in preparing yourself to assist family, friends, co-workers or strangers in the event of sudden cardiac arrest and takes only 2 hours to complete.

If you are interested in finding more about paramedical facts and other medical terms, read more in Australian Paramedical College’s other micro-lectures.

Ian Macleod

Jan 20, 2023

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