Glossary Of Terms - M

Magnetic resonance imaging Mammary artery Medical records Medicines taking and storing Melatonin Meningitis
Metabolism MRSA Methicillin Resistant Staphylococcus Aureus MI Myocardial infarction MIBI Minerals Mitral regurgitation
Mitral valve Mode Monounsaturated fat Mortality amenable to healthcare MRI Muscle
Myocardial infarction MI Myocardial perfusion MAOI = Monoamine oxidase inhibitor, under Brand names of drugs. <

Magnetic resonance imaging MRI. This can be used eg to see whether the heart muscles are working properly, and if not then is whatever is wrong reversible.

Malignant in pathology or tumour contexts means uncontrollable, resistant to therapy, rapidly spreading, life-threatening, and/or deadly.

Mammary artery. There are two mammary arteries in the breast area – left and right, and one may be diverted to make a coronary artery bypass as in a coronary artery bypass graft.

MAOI = Monoamine oxidase inhibitor, under Brand names of drugs and scroll down.

Mast cells. See mast cells under Allergy.

Mean. See mean under Average, Standard deviation.

Median. See median under Average.

Mediators. See mediators under Allergy.

Medical records. You have a right of access to your health records. The Data Protection Act 1998 allows you to have access to information about you held by a hospital or doctor. You are entitled, upon making a written request, to be supplied with a copy of any personal data held about you. For information on how to apply and the charges contact the appropriate manager – eg of patient services at the hospital, or the hospital PALS.

Medicines and Healthcare products Regulatory Agency, MRHA regulates the authorization of drugs and medicines. They safeguard the health of the public by ensuring that medicines and medical devices work and are acceptably safe. No product is risk free. Underpinning all their work lie robust and fact-based judgments to ensure that the benefits to patients and the public justify the risks.
The MHRA and the Commission on Human Medicines CHM, jointly run a Yellow card scheme. If you suspect some drug is causing an adverse drug reaction ADR, you can report it online at (This is not a link) or by post to MHRA, Market Towers, 1 Nine Elms Lane, London SW8 5NQ. You can request a yellow card be sent to you by phoning them on 0808 100 3352.
They are encouraging the public as well as medics to report potential safety issues. They make fact-based robust judgments and take appropriate action where there is a problem.

Medicines – taking and storing. Patients often need assistance, with emphasis on:

● why particular medicines have been prescribed

● how to take them

● who to contact if there are any concerns.

Suggestions and recommendations include the following.

● Understand what each medicine and/or drug is for. Follow the directions and instructions, including any special warnings.

● Keep a list of all the medicines that you are taking – including vitamins, herbal remedies, over the counter remedies, eye drops, inhalers; and have it with you whenever it might be needed.

● Always keep each medicine in its original labelled container. Keep medicines out of direct sunlight and away from children. Never share medicines with anyone else. Do not store unwanted medicines at home; return them to your pharmacy for disposal.

● Keep medicines out of direct sunlight and away from children.

Try not to miss any dose. Unless told otherwise, if you miss a dose, take it as soon as you remember if that is well before half the time till the next dose is due. But if you do not remember till the next dose is due or nearly due just take it then and regard it as taking that next dose early. Never take a double dose. If in doubt contact your doctor or pharmacist.

Do not stop taking any medicine unless instructed by your doctor, unless exceptionally it is producing some undesirable side effect and you are unable to contact your doctor. Some drugs need a gradual reduction of dose, as stopping abruptly may cause withdrawal symptoms and/or a recurrence of whatever the original trouble was.

When buying over-the-counter remedies, inform your pharmacist of any prescribed medicines that you are taking, so the pharmacist can verify that the medicines do not interact in some undesirable way.

Make sure you never run out of any medication. If you will be travelling or going on holiday, particularly abroad, get a repeat prescription covering the holiday period.

Only get a repeat prescription for the medicines that you are currently taking.

Always keep medicine in its original labelled container.

If going to stay in a hospital, take your medication from home with you.

Keep a list of all the medicines that you are taking – including vitamins, herbal remedies, over the counter remedies, eye drops, inhalers; and have it with you whenever it might be needed.

Never share medicines with anyone else.

Do not store unwanted medicines at home; return them to your pharmacy for disposal.

If you have any problem about your medicines, do not hesitate to ask your pharmacist or doctor.

Medulla means the innermost centre part. Eg see Adrenaline, Epinephrine.

Melatonin is a hormone produced in the pineal gland. See melatonin under circadian rhythm.

Membrane. A membrane is

1 any thin pliable sheet of material; or

2 a pliable sheet-like (and usually fibrous) tissue that covers or forms a lining of an organ or group of cells.

A membrane bone is any bone that develops within a membranous tissue, eg the bones of the skull.

Meningitis or meningococcal disease and septicaemia are life-threatening diseases. They can come on very fast – often in a few hours or can be as long as 14 days.

The brain has three layers of tissues around it, called the meninges. The two inner layers have an important fluid between them, the cerebrospinal fluid CSF. The meninges extend to the spinal cord so it is also protected. Meningitis is inflammation of the meninges – by a viral or bacterial infection.

There are various types of meningitis explained below, and one of these can cause death within 12 hours. Hence the rule below of take to A&E without delay. It can occur in people of any age from below one year upwards, and can occur in patients who have a heart condition. It has some or all of the following symptoms, with mnemonic THE FARM VioLiNs.

● Temperature
● Headache – Severe headache and sore eyes when looking at light are important symptoms
● Eyes sore
● Fever
● Appetite loss
● Rash or red spots that do not disappear when pressure is applied, eg by a glass tumbler. See * below about taking to A&E.
● Muscular pain
● Violent vomiting, or nausea – feeling about to vomit
● Light aversion, wanting to lie down in the dark, or not look at light
● Neck stiff – an important symptom, caused by inflammation around the brain or along the spinal cord.

*Take the patient to A&E without delay. Tell the doctor / nurse that he or she has a rash that does not disappear, as a medic might not think of Meningitis or Weil's disease. Delay could be fatal.

The symptoms are similar to Weil's disease. In meningitis the spots do not disappear when glass tumbler pressure is applied.

There are two types of meningitis – viral and bacterial.

The viral meningitis is more common and also less dangerous.

The bacterial meningitis type has two forms.

● The less common bacterial type is sudden with severe headache, shock, rash that looks like bruises, and can lead to death in a very short time.

● The other, more common, bacterial type is more like a cold, with severe headache, vomiting, and rash; and usually lasts about two days.

Metabolise means to do the whole of the chemical processes of metabolism.

Metabolism is the sum total of the chemical processes occurring in the body. This includes all body functions – brain, heart, breathing, circulation, digestion, growth, recovery from injury, availability of energy and the right chemicals for everything needing them, and elimination or removal of waste materials and products; as well as usual everyday functions and activities that you might initially think of.

The basal metabolism is the amount of energy per unit time that the patient’s body needs when resting – for breathing, heart, brain, and other body functions.

The basal metabolic rate is the rate at which the patient's body is actually producing energy or heat when resting. Measuring core body temperature when a patient is sitting at rest about mid-morning gives a good indication of basal metabolic rate.

Thyroxine increases metabolism. Lower body temperature and reduced activity go with lower thyroxine. See Circadian rhythm, and an example under Double-blind trial.

Methicillin Resistant Staphylococcus Aureus, MRSA, is also often used to mean any staphylococcus that is resistant to an antibiotic. SA = Staphylococcus Aureus. MRSA is a bacterium responsible for several infections that are difficult to treat. Generally they are resistant to beta-lactam antibiotics such as penicillin - the penicillins include methicillin.

MSSA = Methicillin-Sensitive Staphylococcus Aureus. MSSA is frightening because it often is contracted while inside a hospital, and because it is resistant to powerful drugs.

Staphylococcus (plural Staphylococci) is a bacterium that is common on skin and can cause disease when there is opportunity to enter the human body. Skin, wound, urinary-tract, and blood-stream infections may then develop.

Staphylococci are often present in boils and infected cuts; and grow if transferred to food. This causes food poisoning – usually with abdominal pain, vomiting, retching, and maybe diarrhoea, typically starting six to 24 hours after infection and lasting many days.

MRSA is a common bacterium found in many people's noses and/or on their skin. Normally, healthy people suffer no harm. MRSA is believed to be spread mostly through contact such as people's hands. MRSA is a type of common germ that is resistant to methicillin and other antibiotics usually used to treat staphylococcus aureus.

Unfortunately, MRSA cases and deaths were increasing (2004). Deaths in England and Wales with MRSA mentioned or being the underlying cause given on the death certificate have increased from 487 in 1999, to 800 in 2002, and 955 in 2003. Deaths in England and Wales mentioning any kind of staphylococcus aureus have gone from 964 in 1999, to 1221 in 2002, and 1403 in 2003. See death rates.

However, though MRSA deaths increased 19% from 2002 to 2003, laboratory reports of MRSA only increased by 7% over the same period. This indicates that some of the increase in mentions of MRSA on death certificates may be due to increased reporting, possibly from the increased public profile of the disease.

In 2004 the UK had 7600 MRSA cases; and MRSA accounted for 44% of hospital-acquired infections, which were affecting about 100,000 people a year. About 5000 deaths a year come from hospital infections. These figures are higher than was occurring several years earlier.

In England & Wales in 2005, 455 death certificates mentioned SA, and 1629 MRSA.

Poor hygiene, eg wound infections and unclean hands, are blamed for SA/MRSA. That is why people should thoroughly wash their hands before touching food. Hospital alcohol gel prevents Staphylococcus, (though not C diff).

To avoid MRSA spreading, hospital staff wear aprons and gloves, wash their hands thoroughly, and/or use an alcohol gel. Patients may be prescribed antibacterial drugs such as ointment for the nose; and/or lotion, soap and shampoo for the skin. Visitors should wash their hands and/or use the gel, and not touch anyone who may be infected. Clothing, towels, and bed linen can be laundered as usual.

Two strains of MRSA, MRSA15 and MRSA16, are contagious and are the commonest strains. In early 2005 some people suggested that the procedures above – such as washing hands, gel, ointment, barrier nursing and isolation, while needed, are not the only issues. With the changing patterns of increasing numbers of hospital day cases and outpatient consultations, high patterns of use of beds, and shorter stays by inpatients, infection control becomes harder. Costs, staffing, buildings and other resources are limited.

Conflicts arise between:

● planning for some spare capacity such as not using all beds all the time – allowing better cleaning and disinfecting both at scheduled times and between patients; isolating patients until the results of tests to find whether or not they are infected; which all costs more per patient and increases patients' waiting times; versus

● higher bed occupancy patterns and throughput, giving shorter waiting times, and being less expensive per patient provided they do not become infected and do not have to stay longer or get other treatment, but perhaps leading to more patients infected.

Methadone is a synthetic drug that is an opioid and an analgesic. It is used to help reduce severe pain, and as a cough suppressant in terminal illness. It is also used to replace morphine and/or heroin when treating dependence.

Brand names of methadone include: Methadose, Metharose, Physeptone, Synastone.

Methoxyisobutylisonitrile = MIBI. See there.

Methyl see methyl under organic chemistry.

mg = milligram = 1/1000 of a gram.

MI means myocardial infarction, essentially the same as a Heart attack.

MIBI scan. MIBI = Methoxyisobutylisonitrile. Also known as a Myocardial perfusion scan.

A MIBI scan is a nuclear medicine procedure. The MIBI scan is in two parts, done on separate days. Each takes 2 to 2½ hours.

Before each part you, the patient, must not have any caffeine for 24 hours; and nothing to eat for six hours before it. You may drink water, fruit juices, and/or squash during the six hours. If you are diabetic you may have a light meal during the six hours.

If you are taking dipyridamole (brand name Persantin) you should discontinue that for the 24 hours. You should not stop any other prescribed medication unless asked by your doctor to so do.

The MIBI scan staff will also need a complete list of whatever medications you are taking.

In the first part you have a stress test. You are given an injection into a vein in your arm of a drug that increases the blood flow to the heart – producing a stress on the heart like exercise would but safely, while an ECG recording is made. A safe radioactive tracer is also injected. Then you are asked to have something to eat and drink, and return later.

When you return your heart will be scanned using a gamma camera. You lie on a couch with your arms and hands up above or behind your head. The camera rotates slowly around your chest for about 15 minutes. You will be asked to wait a short time while the staff check the scan.

The second part is a rest test. You will again be given an injection into a vein of the safe radioactive tracer, but without the drug that increases the heart stress. Then you have something to eat and drink and return for the scan using the gamma camera as before.

After the two scans, the results of the two scans are compared, and may show for example: left ventricle enlarged, how much of its volume of blood is being pumped out per heartbeat, ischaemia – ie heart muscles are / are not short of blood through newly-blocked arteries, and other conditions indicating what treatment you may need.

Minerals are elements – explained under organic chemistry.

A balanced diet as available in the UK contains all the various minerals needed, and in the UK diseases caused by mineral deficiencies are nowadays rare. Healthy people's bodies can get rid of excess amounts without conscious effort or thought.

The usual minimum daily requirements are based on the Reference Nutrient Intake. Several minerals, known as trace elements, are needed but only in tiny amounts for metabolism and health.

Patients only need diet supplements when a doctor has diagnosed a particular deficiency, and/or as a prevention or treatment for a disease or disorder. Some patients have intestinal disorders that prevent absorption of minerals from the diet, so need supplements. Patients with some heart diseases may need their levels of certain minerals to be measured to ensure appropriate treatments.

The minerals in the table are needed. Most of them are needed for growth, so pregnant and breast-feeding mothers and children need relatively more of them. Adults also require most of them for metabolism and body processes, including healing and continual growth and replacement of tissues.

Oily fish twice per week, poultry twice per week (and/or dairy products), and five helpings daily of green vegetables and/or fruit together give enough of all of them!

In the table ● means a good source, * is not as good. The left column gives both the name of the mineral and in some cases the relevant parts of the body.

MineralOily fishPoultryRed meatLiver/
EggsCerealsGreen vegRoot vegPulsesNutsFruit
calcium, bones, teeth, cell function*        
chromium, balances blood sugar *        
cobalt, B12          
copper, process oxygen, nerves      
iron, haemoglobin, carry oxygen       
MineralOily fishPoultryRed meatLiver/ kidneyMilkCheeseButter/ margEggsCerealsGreen vegRoot vegPulsesNutsFruit
magnesium, bones, teeth, nerves        
phosphorus, B12, bones, teeth 
potassium, alternative salt          
sodium, salt
zinc, growth, taste, smell         

Mini heart attack. This usually means an attack of unstable angina.

Mitral regurgitation MR is blood flowing backwards the wrong way through the mitral valve. MR also means medium release - ie the rate of release of a drug in a tablet.

Mitral valve. The mitral valve is between the left atrium and the left ventricle, to allow blood flow into the ventricle but not back. See mitral regurgitation above, and Valve.

Mitral stenosis (MS) is stenosis (narrowing) of the mitral valve.

ml = millilitre(s) = 1/1000 of a litre. ml/hr = ml per hour.

mm = millimetre(s) = 1/1000 of a metre. mmHg = mm of mercury.

Mode. See mode under Average.

Molecule. See molecule or molecular weight both under organic chemistry.

MND = motor neurone disease.

Monounsaturated fat. See Monounsaturated under Fats.

Monovalent see monovalent under organic chemistry.

Morphine, diamorphine. These belong to opioids - analgesics, derived from opium that is obtained from unripe seed capsules of opium poppies. They relieve severe pain eg from heart attacks, surgery, injuries, and/or cancer. They are sometimes used as premedication before surgery. The pain-relieving effect doesn't last long. They can be in a slow-release form to relieve continuous longterm pain. They are habit-forming and can thus lead to addiction. patients who only take them for a short time eg when in hospital do not become addicted and can stop without any trouble.

Brand names of morphine drugs: Morphgesic SR, MST Continus, MXL, Oramorph, Oramorph SR, Sevredol, Zomorph. Also in Cyclimorph, which is a combination.

Mortality amenable to healthcare is how many deaths per year the NHS could plausibly have averted. A Taxpayers' Alliance report says for 2004 (the latest year for which data was available when I looked into this) there could have been 17,157 fewer deaths if the UK's performance had been as good as the average of other European countries studied.

MR = mitral regurgitation, blood flowing backwards the wrong way through the mitral valve. MR also means medium release - ie the rate of release of a drug in a tablet - see half-life.

MRHA. See Medicines and Healthcare products Regulatory Agency.

MRI = magnetic resonance imaging. This can be used eg to see whether the heart muscles are working properly, and if not then is whatever is wrong reversible. Thus it does something slightly different from MIBI and angiography.

MRSA stands for Methicillin Resistant Staphylococcus Aureus or Multiply Resistant Staphylococcus Aureus.

MS = mitral stenosis (you may click on either word) as explained under CHD. MS also stands for multiple sclerosis.

MSSA stands for Methicillin-Sensitive Staphylococcus Aureus. See MRSA.

MSG =monosodium glutamate.

Muscle. A body part that contracts to cause movement.

Smooth muscle is involuntary muscle, not consciously controlled. It also has a smooth surface. It occurs in arteries, veins, and some other parts of the body.

Striated muscle has fibres with bands across. These make voluntary movements, ie controlled from the brain.

Sphincter muscle is a ring of muscle surrounding an opening in an organ of the body. The sphincter muscle can contract to close the opening.

My- and myo- mean muscle, from Greek.

Myalgia means muscle pain in a muscle or a group of muscles. The adjective is myalgic. See algia, which means pain, from Greek.

Myocardial infarction, MI, means roughly the same as heart attack. Strictly it means destruction of an area of heart muscle as a result of obstruction of a coronary artery.

Myocardial ischaemia is another term for where the heart muscle is deprived of oxygen due to poor blood circulation. See Ischaemic heart disease.

Myocardial perfusion scan. See MIBI.

Myocarditis means means inflammation of a heart muscle. Patients typically have shortness of breath and/or an irregular heartbeat. It can be due to a viral infection.


This information was created and edited by Richard Maddison for the BCPA.
Copyright © 1997-2017 The British Cardiac Patients Association, and/or Richard Maddison.
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First published in this form 2002, and updated 2005, 2007, 2008, 2011, 2012, 2013, 2017.
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Authors, sources and acknowledgements

The main sources are BCPA Journal published articles, other information from authors, and publicly available documents and websites. In many cases the journal articles give sources and further information than the Glossary entries.

Parts of the wordings under ECG and Echocardiogram are adapted with permission from BUPA's health information resources, available at

We hope we have thanked everyone.

Richard Maddison

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