Congenital heart diseases: the myocardial bridge
Myocardial bridging, is a congenital condition of the heart characterised by the presence of a bridge of muscle fibres passing over the segment of a coronary artery
In the vast majority of cases, the affected artery is the anterior interventricular artery.
The myocardial bridge is an anomaly created during the formation of the fetal heart muscle in utero
The arteries that supply blood to the heart run along the outside of the heart muscle.
There are then small conduits running down from the heart to supply blood to the myocardial muscle.
In a very small part of the population, part of the heart muscle, instead of being under the artery, grows over the top of it.
Thus, when the heart beats and the muscle contracts, part of the blood is pushed out of the artery section.
In 70% of cases, the myocardial bridge will be an asymptomatic alteration that will not have serious consequences; in a small percentage of cases, the myocardial bridge may cause an occlusion of the artery during the systole phase, contraction of the myocardium, which damages the blood flow from the heart to the rest of the body and organs.
The coronary artery, obstructed due to this bridge, will suffer as it will be narrowed and partly closed by the muscle bands.
The myocardial bridge, will degenerate into coronary artery pathology due to the artery being compressed
The passage of blood will no longer be regular and the risk of ischaemia, angina pectoris and arrhythmias will increase.
Symptoms such as asthenia, dyspnoea, chest pain and irregular heartbeat will occur.
The extent of the pathology varies from subject to subject depending on the anatomical characteristics of the muscle fibres that make up the bridge: the thicker, longer and deeper they are, the greater the possibility of the myocardial bridge severely altering the structure of the arteries.
Other factors that may affect the negative development of the pathology are: heart rate, contractility and drug use.
The prognosis may be influenced by other pathologies if they are present, an example of which is hypertrophic cardiomyopathy, which will see myocardial bridging at an incidence of 30% in sufferers.
In patients with myocardial bridging, medical evaluations should be performed to exclude the coexistence of atherosclerotic coronary stenosis or other pathologies that may have more serious consequences for the heart.
Since the myocardial bridge is a congenital deformity, there are nowadays no effective preventive measures to prevent the risk factors of coronary artery disease and consequently prevent atherosclerosis of the coronary artery that will aggravate the pre-existing condition.
Myocardial bridging, when asymptomatic, will be difficult to diagnose
Even coronary angiography can only detect those deep myocardial bridges.
The diagnosis, with the presence of symptoms, will be made by coronarography, which will show the systolic obstruction of a segment of the coronary artery affected by the alteration.
Coronary CT scans will also be important, as they will allow the anatomy of the arteries to be visualised by checking for obstructions.
In addition to clinical symptoms and corresponding ECG changes, the diagnosis of myocardial bridging depends on coronary angiography, intracoronary Doppler and ultrasound.