Diagnosis of Hypertrophic Cardiomyopathy, HCM Diagnosis - Stanford Hospital & Clinics

Diagnosis of Hypertrophic Cardiomyopathy

Before giving any advice, we gather as much information as we can on your condition.

History and Physical Exam

Our first step is always to listen to you. In fact, we begin to gather information on your presentation even before you arrive. We ask that you fill in a comprehensive questionnaire on your medical history. We may have follow up questions, particularly in relation to any family history, and so may be in touch by phone before your visit. Please contact us with any questions or concerns before your appointment. Please provide your medical records to us before your appointment. At the visit itself, a cardiologist and specialist nurse will ask further questions and carry out a detailed physical exam.

Electrocardiogram (ECG)

All clinic patients have an electrocardiogram, an electrical tracing of the heart. This is often called a ‘12 lead’ ECG (or EKG) because it gives 12 different electrical ‘views’ of the heart. It tells us about heart rhythm and heart size.

Holter Monitor

A “Holter” monitor is a recording of all your heart beats in a 24 hour period. We attach some sticky pads to your chest and you wear a small recording box on your waist. Sometimes, we use a monitor that can stay on for longer, even up to a month.

Echocardiogram ("Echo")

The echocardiogram is one of the most important tests in understanding your heart and diagnosing hypertrophic cardiomyopathy. It is an ultrasound scan of your heart (the same ultrasound used to take pictures of babies in the womb). The ultrasound allows us to view your heart beating in real time. In particular, we can check the heart valves, measure the thickness of the heart walls, and watch the motion of blood as it travels through the heart. We can even use the scan to measure pressures inside the heart: for example, some patients with hypertrophic cardiomyopathy have a build-up of pressure as the blood tries to leave the heart (sometimes called an ‘outflow tract gradient’ – this is why hypertrophic cardiomyopathy is sometimes called hypertrophic obstructive cardiomyopathy). This build-up of pressure (‘gradient’) can be monitored by echocardiography.

Magnetic Resonance Imaging (“MRI”)

In some patients, where very fine measurements are required or where echocardiography does not give good views, we use magnetic resonance imaging. In this test, you lie on a table in the middle of a large magnet and many images are captured all at the same time. Magnetic resonance imaging can also pick up abnormalities of muscle fibres known as “myofibrillar disarray” (see Figure) which would otherwise need a biopsy.

Exercise Testing

All our patients undergo at least one exercise test. This is usually performed on a treadmill. At the beginning we estimate how much exercise we think you will be able to do, then we grade the treadmill so that you will reach this level in about 10 minutes. During the test, we will monitor the electrical activity of your heart and we will ask you to breathe through a face mask. This allows us to monitor your oxygen uptake. At the beginning and end of the test, we do an ultrasound (“echo”) to look at the heart.

The Athletic Heart & Detraining

Sometimes high performance athletes can have slightly thickened heart muscle and this can present a difficult challenge to decide whether this is just the result of training or actually an indication of hypertrophic cardiomyopathy. Although there are many approaches to this, one of the most definitive is a period of detraining. Over 6 weeks of minimal exercise, most athletes’ hearts will return to normal.

Blood Tests

Part of your work up will include blood tests. We can measure many things in your blood such as salts, blood cell counts and protein markers specific to the heart (one is called BNP). In addition, we can carry out genetic tests to look for mutations in specific genes which cause hypertrophic cardiomyopathy. At Stanford, we have a significant research interest in the diagnosis of hypertrophic cardiomyopathy through gene testing. To date, several hundred mutations have been described around the world and we may ask that you consider joining one of our ongoing studies by storing some of your blood and potentially helping us contact other family members so we can ask for permission to store their blood as well. In return, we may be able to tell you more about your family’s disease immediately, or as new gene discoveries are made.

Cardiac Catheterization ("Angiogram" or "Cardiac Cath")

In this procedure, a small hole is made in a blood vessel at the top of the leg and a tube passed up to the heart to measure pressures or inject dye so we can take pictures of arteries. It is usually done as a day case procedure so you do not need to be admitted to hospital. We use local anesthetic to numb the skin and give you some tablets to make you feel sleepy. However, you do not receive a general anesthetic for this procedure and so are never completely ‘out’. In fact, some patients like to watch as the tube is passed up (you don’t feel it). Using this technique we can measure pressures on the right and left of the heart and in the lungs. In addition, we can measure the pressure at different points in the main pumping chamber (left ventricle). Finally, we can take pictures of and measure pressures in the arteries which supply blood and oxygen to your heart to rule out blockages or abnormalities of the large or small vessels, or to detail the anatomy of your coronary arteries for consideration of septal ablation (see below). Although the incision in the leg is less than half an inch in diameter, you may need to lie flat for up to six hours at the end of the procedure to prevent bleeding from the artery in the leg.