Hypertrophic cardiomyopathy is a hereditary condition where the heart fails to pump properly because the heart muscles (myocardium) have thickened (hypertrophied) and become stiff.
The heart muscle often also becomes scarred. In most cases, it is the muscle in the wall of the left ventricle that thickens, but sometimes the right ventricular wall is also affected. The disease is very common, affecting around 1 in 500 people in the UK. Hypertrophic cardiomyopathy can affect people at any age and is equally common among men and women.
Few people with hypertrophic cardiomyopathy develop symptoms and many find that their quality of life is not compromised. For this reason, the condition often goes undiagnosed. However, a small percentage of people do develop symptoms such as shortness of breath and difficulty breathing, heart palpitations, chest pain and light headedness, especially when exercising. Abnormal electric signalling in the heart can lead to arrhythmia and, in some cases, put sufferers at risk of sudden cardiac arrest and death.
The type and severity of the symptoms in each individual depends on which parts of the heart muscle are affected and how stiff the muscle has become.
Hypertrophic cardiomyopathy is caused by one or more gene mutations within the proteins of heart muscle cells. The cells enlarge and become disorganised in their arrangement, rather than forming straight lines. This is referred to as myofiber disarray and it can sometimes lead to arrhythmia. The thickened ventricles may eventually obstruct blood flow from the heart and the disease is sometimes referred to as obstructive hypertrophic cardiomyopathy. When blood flow from the heart is not significantly restricted, the ventricular thickening can still decrease the chamber’s capacity to hold blood and therefore its ability to pump blood around the body. This is sometimes referred to as non-obstructive hypertrophic cardiomyopathy.
The condition is usually inherited and there is a 50% chance that each child born to a parent with hypertrophic cardiomyopathy will inherit the mutation for the disease. The condition may also develop as a result of aging, high blood pressure, diabetes or thyroid disease.
Some of the health problems that affected individuals may experience are described in more detail below.
The disordered arrangement of the heart cells and the thickened ventricular wall may interfere with the heart’s electrical signaling system, which can cause the organ to beat rapidly or irregularly. Examples of the different forms of arrhythmia that may develop include the following:
Atrial fibrillation: This is the most common form of arrhythmia. The upper chambers or atria of the heart contract very quickly and in an irregular manner, which means blood is not completely emptied into the ventricles below. This can cause angina and heart failure, as well as increasing the risk of stroke.
Ventricular tachycardia: This term refers to a rapid resting heart rate, usually between 160 and 240 beats per minutes (bpm), as compared with a healthy resting heart rate of between 60 and 100 bpm. The problem originates in the ventricles of the heart as a result of abnormal electrical signaling due to scarred heart muscle tissue. This can cause angina, shortness of breath and palpitations, as well as increasing the risk of sudden cardiac arrest.
Ventricular fibrillation: This is the most serious form of arrhythmia and is characterized by fast and poorly synchronized contraction of the ventricles. The ventricles pump little or no blood, which causes collapse and cardiac arrest.
Obstructed Blood Flow
The thickened ventricles may obstruct the flow of blood from the heart to other parts of the body. This can lead to shortness of breath, particularly on physical exertion, and lead to light-headedness, fainting and angina.
Eventually, the thickened muscle can weaken and become dilated. The dilated heart wall cannot contract hard enough to pump blood properly. This complication affects only a small proportion of people with hypertrophic cardiomyopathy.
Mitral Valve Problems
Thickening of the heart muscle can result in less space for blood flow. Blood may be forced through the mitral valve from the left atrium to the left ventricle with greater force. The valve is then unable to fully close and blood can move back up into the atrium when the ventricle contracts. This can increase the severity of symptoms.
Thickening of the muscle can eventually mean it becomes so stiff that the heart cannot fill properly with blood and is unable to pump blood effectively enough for the body’s requirements to be met.