Heart attack MI

What a heart attack is and what happens in the heart

A heart attack can occur for several different reasons, but it is essentially when the heart muscle is deprived of any blood flow to a portion of the heart muscle, or myocardium. That is why a heart attack is usually referred to as a myocardial infarction, shortened to MI.

The area of heart muscle deprived of blood flow is not able to receive any oxygen from the fresh blood, which means that the myocardium begins to die. That part of the muscle will not move or pump blood efficiently, and so the event affects the cardiac cycle, the conduction system and the heart's overall function.

Heart attacks can be treated if they are detected early, and treatment usually requires an immediate procedure to reopen the affected vessel. A prolonged heart attack could lead to haemodynamic compromise and even death if the heart muscle is irreparable. Time is the factor that changes what can be saved, which is why speed matters more than certainty about what is happening.

Why heart attacks happen

The coronary arteries are the blood vessels that supply the heart with oxygenated blood to keep the muscle pumping. When they become narrowed or blocked, symptoms worsen and events such as heart attacks and angina pains become more likely. Narrowing and blockages are commonly caused by increased cholesterol levels, leading to a condition known as atherosclerosis.

As atherosclerosis progresses it damages the vessel wall, or the wall ruptures, and that may lead to a blood clot. A blood clot, or thrombus, can restrict blood flow to the heart muscle and cause a myocardial infarction. A thrombus might also break off from the original vessel and travel in the blood, at which point it is known as an embolus, and it can then block another area of the heart, the lungs (a pulmonary embolism) or the brain (a stroke).

Most people who experience heart attacks will usually have associated risk factors which put them at higher risk of developing coronary artery disease or cardiovascular disease. Risk factors are usually split into two categories, modifiable ones which can be changed and are largely reversible, and non-modifiable ones which cannot.

Even some people with no visible risk factors might experience a heart attack, which is one reason people sometimes doubt their own symptoms. These silent risk factors may only present themselves when a heart attack occurs, so someone may not be aware of any issue until that point.

• Modifiable risk factors include obesity or a high BMI, a poor diet, high cholesterol levels (hypercholesterolaemia), high blood pressure (hypertension), diabetes and smoking
• Non-modifiable risk factors include age and gender, congenital heart issues present from birth, genetic predisposition, and the higher risk of heart disease associated with some ethnic backgrounds
• Sustained high blood pressure raises the risk of heart disease, heart attacks, strokes, heart failure, peripheral artery disease, aortic aneurysms, kidney failure and vascular dementia

The symptoms to look out for

Heart attack symptoms can vary from person to person, and they are usually different in males and females. Most patients will experience chest pain, shortness of breath, sweating, pain radiating to the jaw, back or left arm, and sometimes nausea.

Collapse is one way a heart attack can present, and it is often what alerts bystanders to what is happening, but it is not the usual first sign and it is not something to wait for. Most people having a heart attack are conscious and able to describe their symptoms. On rare occasions a heart attack can be silent, causing no preceding symptoms at all.

Symptoms in women often do not match the textbook description. Chest pain does still occur, but it is more likely to be pressure, tightness, burning or heaviness rather than the dramatic crushing pain shown on television. Jaw, neck, back or upper stomach discomfort is more commonly reported as a heart symptom in women than in men, and it can easily be mistaken for dental problems, muscle strain or indigestion. Nausea, sweating and lightheadedness can be signs of a cardiac event, particularly during a heart attack, and a sudden feeling of dread has occasionally been the earliest warning.

This matters because BHF funded research found women have a 50 per cent higher chance than men of receiving the wrong initial diagnosis following a heart attack. If something feels different from anything you have felt before, that is worth acting on rather than explaining away.

If you or someone with you has these symptoms now, call 999 rather than waiting to see whether they pass. This may be a heart attack and minutes matter.

• Chest pain, often described as pressure, tightness, heaviness or squeezing
• Shortness of breath
• Sweating
• Pain radiating to the jaw, back or left arm
• Nausea
• Lightheadedness
• A feeling of impending doom
• Collapse, which can be the first sign a bystander sees

How a heart attack is diagnosed

When a heart attack is being diagnosed in hospital, a few tests are used together. Blood tests are always useful, because raised inflammatory markers and cardiac markers can reliably indicate an acute heart attack.

An ECG is the other immediate tool. The ST segment on the ECG is a good indicator of myocardial health, and ST elevation can indicate the presence of a recent or ongoing heart attack. A heart attack diagnosed with the use of ST elevation on an ECG is known as a STEMI, short for ST elevation myocardial infarction. Heart attacks without that pattern are known as NSTEMIs.

A coronary angiogram is the invasive test that shows the condition of the coronary arteries directly. A small tube called a catheter is inserted through the wrist or leg and advanced to the aorta, the large blood vessel that carries blood from the left ventricle to the rest of the body. The coronary arteries branch off from the aorta, so the catheter can be used to look inside them and assess their condition. A contrast dye is used to allow the arteries to be seen on a special type of X-ray known as fluoroscopy.

Outside the emergency setting, where symptoms are ongoing rather than acute, Dr Jogiya will usually arrange a full assessment made up of a careful history, an examination, an ECG, an echocardiogram and blood tests, with further imaging arranged when the clinical picture warrants it.

• Blood tests to look for raised inflammatory and cardiac markers
• A 12 lead ECG to look at the ST segment and identify a STEMI or an NSTEMI
• A coronary angiogram to see the coronary arteries directly and find the vessel responsible
• An echocardiogram to assess how well the heart muscle is pumping

How a heart attack is treated

A heart attack usually requires an immediate percutaneous coronary intervention, or PCI, to the affected vessel. PCI is carried out through a catheter using the same route as a coronary angiogram, so the two are often done in the same sitting.

Where an artery is narrowed, a balloon angioplasty pushes the artery walls open and allows more blood to flow through the vessel. Because there can be a risk of the vessel closing up again or re-narrowing, a stent may be inserted to keep it open. Where an artery is completely blocked, a coronary artery bypass graft, shortened to CABG, can be performed to bypass the affected artery. A CABG usually means staying in hospital for a few days, whereas angiograms and stents are normally day-case procedures.

Controlling cholesterol levels sits alongside these procedures rather than after them, and usually requires medication together with a controlled diet to reduce fats and oils.

Medication, monitoring and recovery afterwards

Following a heart attack, a patient might require monitoring for a few days before being discharged from hospital. Regular medication such as blood thinners, aspirin, and cholesterol-controlling medication such as statins might be required on a long-term prescription.

Some patients need rehabilitation sessions to regain strength and cardiac function following a more severe heart attack. It may take a few weeks to return to your normal level of activity, but regular rehabilitation can make a real difference to your prognosis and can help you to return to normality.

Lifestyle changes make a genuine difference to the underlying disease. A balanced diet, cutting down on alcohol, quitting smoking, losing weight and regular exercise all support cardiac health and reduce the risk of further events. Dr Jogiya will discuss which of these matter most in your case, alongside blood pressure and cholesterol control.

When to call 999 and when to arrange an assessment

If chest pain is severe, lasts more than 15 minutes, does not ease with rest, or comes with sweating, sickness, breathlessness or a feeling of impending doom, call 999. This may be a heart attack and minutes matter, because delay costs heart muscle. The same applies if someone collapses.

If a familiar angina pattern has changed, coming on with less effort, at rest, or more frequently, that is unstable angina until proven otherwise and needs same-day medical assessment rather than a routine appointment.

For symptoms that are ongoing rather than acute, or if you have already been told your symptoms are unlikely to be cardiac but still feel something is not right, a proper cardiology assessment is the right next step. Dr Jogiya sees patients privately across Kingston-upon-Thames and South West London, with ECG, echocardiography and onward imaging available where they are needed.