Understanding cardiac terminology

Posted: 03/03/2020

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Medical terminology can be confusing at times, which can lead to misunderstandings about the severity of a condition, and the prognosis that comes with it. People may use terms interchangeably, which may create ambiguity over what has happened, and what the likely impact is for a patient. This article explains some commonly used terminology and the difference between some key definitions.

A heart attack, (also called coronary thrombosis or myocardial infarction) is where an obstruction occurs in one of the main blood vessels (the coronary arteries) supplying the heart muscle (or myocardium, myo for muscle, kardia meaning heart in Greek).

Obstruction of these vessels normally starts with a narrowing of the artery, with fatty build ups (heart disease, or atherosclerosis) in the artery wall. A blood clot (thrombus) then develops in the damaged artery wall, which can break off and lodge in the artery, meaning that the heart muscle does not get enough oxygen to function.

Before the infarction itself occurs, a patient may experience transient chest pain which is normally on exertion, because the heart can function reasonably well at rest, but struggles to get enough oxygen when stressed. This is a condition known as angina. Angina itself is not normally life threatening, but can be an indication that a person is at risk of a heart attack (or other condition) because of heart disease.

Several treatments are available to reduce that risk, including anti-clotting medications, drugs to widen the blood vessels, and in some cases, angioplasty and stenting of the vessel. Angioplasty, also known as percutaneous coronary intervention (PCI), is a procedure to place a small balloon inside the narrowed vessel. The balloon is inflated to widen the artery, and then removed. This may be followed by placing a stent, which is a small metal tube to keep the artery open in the longer term.

Angina can be considered stable or unstable. Stable angina tends to have a trigger, such as exercise, and stops within a few minutes of resting. Unstable angina is more serious and can continue after rest. It may be a prelude to a more significant event.

The heart attack, or myocardial infarction normally comes in one of two forms, a non-ST elevated myocardial infarction, or ST-elevated myocardial infarction (NSTEMI or STEMI). The ‘ST- elevation’ is a description of changes seen on an ECG (electrocardiogram), the measurement of electrical activity in the heart. On the trace produced by an ECG machine, a typical heart beat has points labelled P,Q,R,S and T, and in more serious heart attacks, the S-T segment is elevated on that trace.

A NSTEMI suggests significant, but not complete blockage of the coronary artery. Some oxygen is available to the heart muscle, although it is still a serious condition and normally a patient experiencing a NSTEMI will be rapidly sent for PCI and/or stenting to widen the artery before a more serious event takes place.

A STEMI usually represents a complete blockage of the coronary vessel, which means the heart muscle is starved of oxygen. Within minutes to hours the heart muscle cells (cardiomyocytes) will start to die off, and this can lead to permanent damage. However, rapid PCI can often open up the cardiac arteries, and in many cases the patient can survive a STEMI, sometimes with minimal long term damage to the heart muscle.

The key to successful treatment is rapid response, and minutes count. The National Institute for Clinical Excellence (NICE) indicates a ‘call to balloon time’ of 120 minutes, and a ‘door to balloon time’ of 90 minutes, ie from the point that an emergency call is made, or from emergency services arriving at the scene of a heart attack, a patient should be undergoing PCI within two hours, or 90 minutes respectively. With the rapid improvement of PCI technology, and telemetry whereby ambulances can send ECG data ahead to the receiving hospital, overall, over 90% of patients can be expected to survive myocardial infarctions in developed countries.

In most cases of myocardial infarction, the heart will continue to beat and provide oxygen to the body, unless it is very severely damaged. If the heart stops beating, this is known as a cardiac arrest, and is an extremely serious event.

A cardiac arrest is most commonly caused by myocardial infarction, but can be caused by other conditions, and as soon as the heart stops beating, the brain and other organs become starved of oxygen. While the chances of having an ‘out of hospital cardiac arrest’ are less than one in 300,000, the survival rate is poor, with only around 10% of patients surviving.  The chances of survival decrease by around 10% with every minute that the patient is untreated. If the cardiac arrest is witnessed, with early cardiopulmonary resuscitation (CPR) and defibrillation (an electric shock applied to the heart to restore the rhythm) then the chances of survival improve considerably. Defibrillators are routinely placed in shopping centres, sports stadiums and other areas where people congregate. Modern machines will give clear audible instructions to untrained users, and analyse the patient’s heart rhythm before administering a shock. If the patient will not benefit from a shock, it will not be delivered. 

Heart failure can arise after a heart attack, or from other conditions. It is sometimes referred to as congestive heart failure (CHF). It tends to be a more chronic condition and does not imply that the heart is not beating, but that the heart is unable to pump blood around the body efficiently. When the heart is not beating efficiently, it can lead to fluid leaking out of blood vessels into the surrounding tissues (oedema). This means that patients can experience fluid build-up in the legs or ankles, leading to swelling, or in the lungs, leading to breathing difficulties. Heart failure is generally managed with drugs (diuretics to decrease fluid retention, and inotropes to increase the force with which the heart beats), lifestyle changes and in some cases pacemakers, valve replacement, or bypass surgery.  

Emma McCheyne, senior associate in Penningtons Manches Cooper’s clinical negligence team, said: “It is vitally important that medical staff explain to patients and family members exactly what they are experiencing and manage their expectations. Particularly at times of stress, it can be difficult to retain significant amounts of information and medical staff may need to reiterate this information several times in order to ensure that patients understand their condition fully. If the treatment itself has been in any way substandard, poor communication only leads to further patient dissatisfaction, and a failure to explain events is often at the root of many claims.”

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