Heart disease seems to be caused by everything these days — sometimes it feels easier to list the things that don't cause it. In reality, the vast majority of heart disease comes down to a handful of processes affecting your heart and blood vessels. Understanding those processes gives you a much clearer idea of what to look out for.
How the heart works
The heart may look like a single piece of muscle, but it is divided into left and right sides, each with an atrium and a ventricle. The right atrium receives deoxygenated blood returning from the body and feeds it into the right ventricle, which pumps it to the lungs. Once oxygenated, blood returns to the left atrium, passes into the left ventricle, and is pumped out through the aorta to the rest of the body.
The heart supplies itself through the coronary arteries, which branch off just above the left ventricle and wrap around the organ. The whole thing is coordinated by an electrical system that sends impulses across the atria and down the ventricles, producing the wave of contraction we recognise as a heartbeat.
Almost everything that goes wrong with the heart involves one of three things: its structure, its blood supply, or its electrical system.
Arterial insufficiency
The most common cause of heart disease is inadequate blood supply to the heart muscle itself. When flow is restricted, the heart struggles during exertion and can trigger chest pain — angina. If supply is cut off severely enough, heart muscle begins to die. That is a heart attack.
Coronary arteries usually narrow through atherosclerosis, where fatty deposits build up in the vessel walls. Plaques can also rupture, triggering a clot that blocks the artery suddenly. Alternatively a clot formed elsewhere can travel and lodge in a coronary artery.
Heart failure
When the heart's chambers become too enlarged or too weak to pump effectively, blood backs up and organs downstream receive too little. This is heart failure. Causes vary — long-standing high blood pressure, previous heart attacks, valve disease, cardiomyopathies — but the result is progressive strain on the body's other systems. Common signs include breathlessness (especially lying flat), swollen ankles and legs, and persistent fatigue.
Arrhythmias
Any defect in the heart's electrical system causes discoordination in its motion — an arrhythmia. Two categories matter particularly:
- Tachyarrhythmias — the chambers maintain a coordinated rhythm but beat far too fast, sometimes fast enough that blood cannot fill the chamber properly
- Fibrillation — uncoordinated electrical activity causing the chamber to quiver rather than pump. Atrial fibrillation raises stroke risk substantially; ventricular fibrillation is a medical emergency
Structural heart defects
The heart develops along a highly complex pathway in the embryo, involving thousands of proteins. Walls can fail to close, muscle can overgrow, vessels can connect in the wrong place, and valves can leak or narrow. One variation is common enough to appear in a substantial portion of the population: a small opening between the two atria, often only a few millimetres, which rarely causes symptoms.
Risk factors you can influence
- Smoking — the single biggest modifiable risk
- High blood pressure and high cholesterol
- Diabetes and pre-diabetes
- Physical inactivity and excess weight, particularly around the abdomen
- Excessive alcohol
- Poor sleep and chronic stress
Age, sex and family history cannot be changed — but knowing them tells you how aggressively to manage everything else.
When to get urgent help
Call 999 for chest pain or pressure lasting more than 15 minutes, especially with breathlessness, sweating, nausea, or pain spreading to the arm, jaw or back — or for sudden severe breathlessness, or fainting during exertion.
Understanding your own risk
Rightangled offers home blood tests covering cholesterol, HbA1c and other cardiovascular markers, plus DNA tests assessing inherited cardiovascular risk. Results are reviewed by our clinical team, which includes GPhC-registered independent prescribers, with medical oversight from our doctor, Dr Abdullah.
Verify us with the General Pharmaceutical Council (registration 9011933), see our LegitScript certification, and read reviews on Trustpilot.
Related reading: basic heart health and how the heart works.
This article is for general information and does not replace personalised medical advice. If you think you may be having a heart attack, call 999.
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