Myocardial bridging is the part of the coronary artery that tunnels the heart muscle itself for reasons that are still unknown (normally, the coronary arteries run on the outside of the heart, not through it).
What is myocardial bridging?
Every time the heart beats, the „bridged“ part of the artery is squeezed – think of it as a straw that you squeeze with your fingers.
This cuts off blood flow to the left upper chamber of the heart, sometimes 80% or even 100% in severe cases. The left upper chamber is the most important chamber because it is the one that pumps blood to the body.
However, if a band of muscle forms around one of the coronary arteries during fetal development, a myocardial bridge (=muscle bridge) is formed – a „bridging“ of the heart muscle over the artery. Each time the heart squeezes to pump blood, the muscle band exerts pressure and narrows the artery, reducing blood flow to the heart. This defect is present from birth. It is important to note that even a very thin ex. < 1 mm and/or short e.g. 20 mm myocardial bridge can cause significant symptoms. Myocardial bridge can be from a few mm to 10 cm or more in length.
Unfortunately, even people with a muscle bridge whose hearts are circulating well and pass the stress test have many unpleasant symptoms, most often unexplained chest pain (at rest or vice versa during activity), but also e.g. occasional arrhythmias, fatigue, anxiety and shortness of breath.
WERE PEOPLE BORN WITH A MUSCLE BRIDGE? Yes. A myocardial bridge is a congenital heart defect present from birth. Stanford researchers believe that myocardial bridges develop at the end of the first trimester of fetal development.
Myocardial bridges are dynamic blockages and can change from moment to moment depending on blood pressure, heart rate, adrenergic status (adrenaline) and stress hormones in the bloodstream, etc. Stress hormones (e.g. cortisol) give you a tendency for more cramping in addition to the mechanical compression of the blood vessel in the form of the first three examples. Hence symptomatic patients may live a few days fine, and other days in great discomfort of the resulting symptoms.
Compressed arteries open slowly, they do not open immediately when the pressure on them stops. Specifically, after a muscular bridge compresses and compresses the artery, like clutching a plastic straw, when the heart subsequently relaxes, the compressed artery actually remains compressed long into the diastolic phase – in many cases for most of the diastolic phase – which again is when 85% of blood flow should occur. Thus, throughout this time that the artery remains compressed during the diastolic phase, blood flow is interrupted. The compression of the myocardial bridge and the loss of blood flow is combined with the oppression caused by the plaque in the surrounding area and also with the endothelial dysfunction that often occurs internally, leading to an intensification of symptoms.
See more on Bridging the Gap in a Rare Cause of Angina
SOMETIMES I FEEL GOOD AND I CAN LIVE MY LIFE. SOMETIMES I FEEL SO BAD I CAN’T LEAVE THE HOUSE, IS THAT NORMAL WITH A MYOCARDIAL BRIDGE?
Quote from Dr. Schnittger: „Yes, typical. Myocardial bridges are dynamic blockages and can change from moment to moment depending on blood pressure, heart rate, adrenergic status (adrenaline) and stress hormones in the bloodstream, etc. Stress hormones (e.g. cortisol) tend to give you more cramping in addition to the mechanical compression of the blood vessel in the form of the first three examples.“
IS THE DEPTH OF THE MUSCLE BRIDGE RELATED TO THE LEVEL OF SYMPTOMS?
According to Stanford University and the comments of surgeon Dr. Boyd, not necessarily. Even a very thin muscle band <1 mm can cause severe symptoms.
CAN YOU HAVE A MUSCLE BRIDGE ON MULTIPLE ARTERIES?
YES. It is entirely possible to have a muscle bridge on the LAD and also on the RCA (right coronary artery) or LCX (left circumflex coronary artery).
HAS ANYONE EVER HAD 100% COMPRESSION OF AN ARTERY DUE TO A MUSCLE BRIDGE?
Yes, multiple people have.
WHY DO MYOCARDIAL BRIDGES TEND TO DEVELOP MORE SYMPTOMS AS WE AGE?
First, as we age, arteries become less pliable, so when a myocardial bridge compresses, it is harder to elastically bounce back. Second, as we age, plaque builds up, which can combine with the myocardial bridge and worsen symptoms. In particular, research has found that plaque usually accumulates just above/before the muscle bridge in the artery, but not within the muscle bridge. Thus, if blood flow is already reduced due to plaque formation in front of the muscle bridge and then is further reduced by the muscle bridge itself, the combined reduction in flow can be very significant. Thirdly, the more the artery in the area of the muscular bridge is stressed over the years, the greater the endothelial dysfunction (= a type of non-obstructive coronary artery disease (CAD) in which there is no blockage of the heart arteries, but the large vessels on the surface of the heart narrow (constrict) instead of dilate (open), this disease affects women rather than men and causes chronic chest pain) inside the artery, i.e. The lining of the artery no longer works well to stay open and so collapses.
ARE MYOCARDIAL BRIDGES ON ARTERIES OTHER THAN THE LAD SIGNIFICANT, SUCH AS ON THE RCA (RIGHT CORONARY ARTERY) OR LCX (LEFT CIRCUMFLEX CORONARY ARTERY)?
IS HIGH BLOOD PRESSURE ASSOCIATED WITH A MYOCARDIAL BRIDGE?
Not necessarily. Many people with a myocardial bridge have high pressure, others, on the contrary, have low pressure.
IS HIGH HEART RATE ASSOCIATED WITH A MYOCARDIAL BRIDGE?
As above, not necessarily. Many people with a muscular bridge have a high heart rate, others have a low heart rate.
IS THE LENGTH OF THE MUSCLE BRIDGE DIRECTLY RELATED TO THE LEVEL OF SYMPTOMS?
It seems to. Stanford has shown that the longer the bridge (tunnel), the more the flow slows and the more symptoms multiply, the more likely they are to develop.
FOR MORE INFORMATIONS CHECK OUT THE MYOCARDIAL BRIDGE SUPPORT GROUP ON FACEBOOK.
This is amazing patients group and the admin Rob Thornett did great job to prepare a documentary for all MB patients (which summarizes diagnosis, treatment, details about surgery, post-op process, FAQs, myths etc.). These FAQs are taken from that documentary and credit goes to Rob. The group forum is filled with experiences, pre-ops, post-ops, studies.