Myocardial bridging: when a coronary artery runs through the heart muscle

The coronary arteries normally run along the outer surface of the heart. In myocardial bridging, a short segment of one of them dips into the heart muscle and travels beneath a band of muscle before re-emerging. A 2023 review describes it as an encroachment of the coronary artery past its natural surface course and into the myocardium, regarded as an abnormal but benign variant that is being diagnosed more often because imaging has improved. The bridge is made of ordinary heart muscle, hence the name.

The review says the left anterior descending artery, which runs down the front of the heart, is the most commonly involved vessel. In the majority, tunnelling has no clinical significance. When the tunnelled segment is deeper or longer, the squeeze of each heartbeat on the vessel can cause problems such as angina, stress-related symptoms or, rarely, rhythm disturbance.

The numbers depend heavily on how it is looked for. The review says prevalence varies widely according to the diagnostic approach: studies with coronary CT have shown about 25 percent, but with a range of 5 to 86 percent, while invasive angiography shows a prevalence of about 1.7 percent, with a range of 0.5 to 16 percent. It also says the proportion of people with symptoms is approximately 1 to 5 percent in some studies.

The practical message is that many people have a bridge without ever knowing it, and that finding one on a scan does not automatically mean it is the cause of symptoms.

The review says it is most commonly an incidental finding because most patients are asymptomatic. For the minority with symptoms, it describes reproducible stable angina-type pain, unstable angina, heart block, Takotsubo syndrome and, rarely, sudden death.

The NHS describes angina as pain or tightness, usually in the chest, that may spread to the neck, shoulders, jaw or arms and can make you feel sick, breathless, dizzy or sweaty, and is often brought on by exercise, stress, emotion or cold. It advises seeing a GP as soon as possible if you think you may have it, getting help from NHS 111 if chest pain comes and goes or has changed, and calling 999 for chest pain that does not stop after resting, for pain spreading to the arm, neck or jaw, or chest pain with sweating, sickness, light-headedness or breathlessness. Do not drive yourself to A&E.

• Call 999 for chest pain that does not settle with rest, spreads to the arm, jaw or neck, or comes with sweating, sickness or breathlessness.

• Seek same-day advice (GP or NHS 111) for new chest pain that comes and goes, or angina that is more frequent or happens at rest.

• Tell your doctor if you have been told you have a bridge before they prescribe chest-pain medicines.

The review says a diagnosis is made when a substantial or entire coronary artery segment is embedded in the heart muscle, and that it may be made at cardiac catheterisation, on coronary CT, during surgery or after death. It notes there is no specific gold standard test. Coronary CT angiography is increasingly used for chest pain and can show the artery and the muscle around it, classifying bridges as superficial or deep. The classic invasive finding is a narrowing of the artery with each heartbeat, called the milking effect, seen on coronary angiography. Other tools include intravascular ultrasound, pressure-wire measurements and stress imaging.

The NHS says a GP who thinks you may have angina refers you to a cardiologist and that tests may include blood tests, an ECG and scans such as an angiogram, MRI or CT scan. If a bridge is found, your cardiologist will judge whether it is likely to explain your symptoms or whether another cause, such as narrowing from atheroma, needs attention. The review notes that bridging has been associated with plaque forming just before the bridge in some studies.

Most people need no treatment, only reassurance and healthy-heart advice. For symptomatic bridging, the review says treatment aims to relieve symptoms and prevent adverse outcomes. Medical therapy comes first: beta blockers are considered first-line because they slow the heart and lengthen the time for coronary filling, with non-dihydropyridine calcium channel blockers as an alternative. It states that vasodilatory agents should be avoided because they can increase the risk of ischaemia, which is why you should ask your cardiologist about glyceryl trinitrate (GTN), the spray or tablet commonly prescribed for angina by the NHS, if you have a known bridge.

For symptoms that do not settle, procedures have been used. The review reports that stenting has had high rates of repeat treatment and complications such as perforation and stent fracture, and that its usefulness is limited and not recommended. Surgical options are supra-arterial myotomy, in which the overlying muscle is divided, or bypass grafting, with myotomy possibly preferred for refractory symptoms with significant narrowing or ischaemia, though the evidence is limited and which is better is not clear.

Alongside treatment, the NHS angina advice about avoiding triggers such as stress, cold and large meals, not smoking, keeping a healthy weight and being active applies.

The 2023 review concludes that myocardial bridging is a treatable cardiac anomaly and that a combined approach of diagnosis, treatment and follow-up is needed to reduce illness and mortality, while describing the great majority as benign. For most people who have a bridge found incidentally, the outlook is good and no restriction is needed. Ask your cardiologist whether you need follow-up, and about exercise and medicines.

On the NHS, chest pain is assessed through the GP, rapid access chest pain clinics and cardiology departments; bridging is usually found during coronary CT or angiography. Private cardiology reviews and CT coronary angiography are available in the UK. No NHS or British Heart Foundation patient leaflet dedicated to myocardial bridging was found while preparing this page, so the main source is a published clinical review.