What Causes Inherited Heart Conditions?

DNA: the instruction set

Every protein in your body is built from instructions written in DNA — a long molecule made of smaller units your cells read much like a book. A complex cellular apparatus translates that simple four-letter language into the three-dimensional structures we call proteins.

You carry two copies of most instructions, because chromosomes come in pairs: one set inherited from your mother, one from your father. When you have children, those pairs separate again, giving a 50:50 chance of passing on either copy.

That redundancy is protective. A faulty instruction on one copy can often be compensated for by the working copy from your other parent. It also means a faulty instruction can pass silently through generations before it causes anyone problems.

Why proteins matter

Proteins are extraordinarily versatile. They form the structural skeleton of cells, break down food into usable energy, contract your muscles, carry oxygen, and coordinate how the body develops. Their production is tightly regulated for good reason.

Most of the time, a faulty instruction has no consequence — there is enough redundancy in the system to absorb it. Occasionally, though, a critical protein is built incorrectly in a place where it matters, and that is when problems arise.

How this affects the heart

The heart offers a clear example. Cardiac muscle relies on a protein called myosin to contract and generate pumping force. A single change at the right point in the myosin instructions produces a protein that does not function properly.

The heart responds to that inefficiency the way any muscle responds to a heavy workload — by growing thicker. But the heart is not any other muscle. The extra thickening reduces the space available inside the chamber, so it cannot fill properly between beats, and it can obstruct blood leaving the heart. Fluid may build up in the lungs, organs may receive inadequate blood supply, and fainting or, rarely, sudden cardiac death can occur.

This condition is hypertrophic cardiomyopathy, and it affects roughly 1 in 500 people. It is the result of a single protein altered by a single change in a single gene.

Not all inherited conditions are simple

Hypertrophic cardiomyopathy is unusually traceable. Many inherited cardiac conditions involve multiple genes interacting with each other and with lifestyle factors. Others — long QT syndrome, Brugada syndrome, familial hypercholesterolaemia — have their own distinct mechanisms. What they share is an origin in DNA changes that either cause disease directly or raise the risk of it.

Warning signs worth acting on

Speak to your GP if you experience fainting during exercise, unexplained palpitations, breathlessness disproportionate to your activity level, or chest pain on exertion — and particularly if a close relative had heart problems young, or died suddenly and unexpectedly under 40.

Testing

Because these conditions arise from specific DNA changes, a saliva or blood sample can be enough for a laboratory to identify relevant variants. Where an inherited cardiac condition is confirmed in a family, NHS specialist clinics offer cascade testing so relatives can be screened.

Rightangled's DNA tests assess genetic markers associated with cardiovascular risk, with results reviewed by our clinical team, which includes GPhC-registered independent prescribers, and medical oversight from our doctor, Dr Abdullah. A consumer test is a screening and awareness tool — if you have a strong family history, ask your GP for referral to an inherited cardiac conditions clinic, where genetic counselling is provided alongside testing.

The British Heart Foundation also runs a Genetic Information Service helpline on 0300 456 8383.

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Related reading: types of inherited heart condition.

This article is for general information and does not replace personalised medical advice.