The Heart

What is it?

The normal heart is a strong, muscular pump. located within the thorax that measures a little larger than a fist. It pumps blood continuously through the circulatory system.

Each day the average heart beats (expands and contracts) 100,000 times and pumps about 2,000 gallons of blood through the body. In a 70-year lifetime, an average human heart beats more than 2.5 billion times

Anatomy of the Heart

The heart: four chambers, four valves

The heart has four chambers, two on the right and two on the left:

• Two upper chambers are called atria (one is called an atrium).

• Two lower chambers are called ventricles.

The heart also has four valves that open and close to let blood flow in only one direction when the heart contracts (beats). The four heart valves are:

• Tricuspid valve, located between the right atrium and right ventricle

• Pulmonary or pulmonic valve, between the right ventricle and the pulmonary artery

• Mitral valve, between the left atrium and left ventricle

• Aortic valve, between the left ventricle and the aorta

Each valve has a set of flaps (also called leaflets or cusps). The mitral valve has two flaps; the others have three. Blood flow occurs only when there's a difference in pressure across the valves, which causes them to open. Under normal conditions, the valves permit blood to flow in only one direction.

The heart pumps blood to the lungs and to all the body's tissues by a sequence of highly organized contractions of the four chambers. For the heart to function properly, the four chambers must beat in an organized way.

The Electrical System of the Heart

The heart beat (contraction) begins when an electrical impulse from the sinoatrial node (also called the SA node or sinus node) moves through it. The SA node is sometimes referred to as the heart's "natural pacemaker" because it initiates impulses for the heartbeat.

The normal electrical sequence begins in the right atrium and spreads throughout the atria to the atrioventricular (AV) node. From the AV node, electrical impulses travel down a group of specialized fibers called the His-Purkinje system to all parts of the ventricles.

This exact route must be followed for the heart to pump properly. As long as the electrical impulse is transmitted normally, the heart pumps and beats at a regular pace. In an adult, a normal heart beats 60 to 100 times a minute.

What happens if the Heart pumps irregularly?

Arrhythmias are abnormal beats. The term "arrhythmia" refers to any change from the normal sequence of electrical impulses, causing abnormal heart rhythms. Arrhythmias may be completely harmless or life-threatening.

Some arrhythmias are so brief (for example, a temporary pause or premature beat) that the overall heart rate or rhythm isn't greatly affected. But if arrhythmias last longer, they may cause the heart rate to be too slow or too fast or the heart rhythm to be erratic – so the heart pumps less effectively.

• A fast heart rate (in adults, more than 100 beats per minute) is called tachycardia.

• A slow heart rate (less than 60 beats per minute) is referred to as bradycardia.

Causes

• Normally, the heart's most rapidly firing cells are in the sinus (or sinoatrial or SA) node, making that area a natural pacemaker.

• Under some conditions almost all heart tissue can start an impulse of the type that can generate a heartbeat.

• Cells in the heart's conduction system can fire automatically and start electrical activity. This activity can interrupt the normal order of the heart's pumping activity.

• Secondary pacemakers elsewhere in the heart provide a "back-up" rhythm when the sinus node doesn't work properly or when impulses are blocked somewhere in the conduction system.

An arrhythmia occurs when:

• The heart's natural pacemaker develops an abnormal rate or rhythm.

• The normal conduction pathway is interrupted.

• Another part of the heart takes over as pacemaker.

EKGs

What is it?

An electrocardiogram — abbreviated as EKG or ECG — is a test that measures the electrical activity of the heartbeat. With each beat, an electrical impulse (or “wave”) travels through the heart. This wave causes the muscle to squeeze and pump blood from the heart. A normal heartbeat on ECG will show the timing of the top and lower chambers.

Why do we need it?

An ECG gives two major kinds of information. 

1. First, by measuring time intervals on the ECG, a doctor can determine how long the electrical wave takes to pass through the heart. Finding out how long a wave takes to travel from one part of the heart to the next shows if the electrical activity is normal or slow, fast or irregular. 

2. Second, by measuring the amount of electrical activity passing through the heart muscle, a cardiologist may be able to find out if parts of the heart are too large or are overworked.

Some other reasons include

An electrocardiogram is a painless, noninvasive way to help diagnose many common heart problems in people of all ages. Your doctor may use an electrocardiogram to determine or detect:

• Abnormal heart rhythm (arrhythmias)

• If blocked or narrowed arteries in your heart (coronary artery disease) are causing chest pain or a heart attack

• Whether you have had a previous heart attack

• How well certain heart disease treatments, such as a pacemaker, are working

How do I know if I need an EKG?

You may need an ECG if you have any of the following signs and symptoms:

• Chest pain

• Dizziness, lightheadedness or confusion

• Heart palpitations

• Rapid pulse

• Shortness of breath

• Weakness, fatigue or a decline in ability to exercise

Hypertrophic Cardiomyopathy(HCM)

What is it?

Hypertrophic cardiomyopathy is most often caused by abnormal genes in the heart muscle. These genes cause the walls of the heart chamber (left ventricle) to contract harder and become thicker than normal. 

The thickened walls become stiff. This reduces the amount of blood taken in and pumped out to the body with each heartbeat.

Is there more than one type of HCM?

In obstructive HCM, the wall (septum) between the two bottom chambers of the heart thickens. The walls of the pumping chamber can also become stiff. It may block or reduce the blood flow from the left ventricle to the aorta. Most people with HCM have this type.

In non-obstructive HCM, the heart’s main pumping chamber still becomes stiff. This limits how much blood the ventricle can take in and pump out, but blood flow is not blocked. 

What are some of the signs and symptoms of HCM?

Some people with hypertrophic cardiomyopathy don’t have symptoms. Others may not have signs or symptoms in the early stages of the disease but may develop them over time. 

Signs and symptoms of HCM include:

• Chest pain, especially with physical exertion

• Shortness of breath, especially with physical exertion

• Fatigue

• Arrhythmias (abnormal heart rhythms)

• Dizziness

• Lightheadedness

• Fainting (syncope)

• Swelling in the ankles, feet, legs, abdomen and veins in the neck

HCM is a chronic disease that can get worse over time. This can lead to poorer function and quality of life, long-term complications and more financial and social burden. 

People with HCM often need to make lifestyle changes, such as limiting their activity, to adjust for their disease.  

As HCM progresses, it can cause other health problems. People with HCM are at higher risk for developing atrial fibrillation, which can lead to blood clots, stroke and other heart-related complications. HCM may also lead to heart failure. It can also lead to sudden cardiac arrest, but this is rare. 

HCM has been cited as the most common reason for sudden cardiac death in young people and athletes under the age of 35.

How is HCM diagnosed?

Hypertrophic cardiomyopathy is most often inherited. HCM is the most common form of genetic heart disease. It can happen at any age, but most receive a diagnosis in middle age. 

It’s estimated that 1 in every 500 people have HCM, but a large percentage of patients are undiagnosed. Of those diagnosed, two-thirds have obstructive HCM and one-third have non-obstructive HCM.

A cardiologist or pediatric cardiologist often diagnoses and treats HCM. You may also be referred to a cardiomyopathy center where the health care team has specialized training.

HCM is diagnosed based on your medical history, family history, a physical exam and diagnostic test results.  

Medical and Family Histories

Knowing your medical history and any signs and symptoms you may have is an important first step. Your physician will also want to know if anyone in your family has been diagnosed with HCM, heart failure or cardiac arrest.

Physical Exam

Your heart and lungs will be checked. Your physician will listen for certain sounds with a stethoscope. For example, the loudness, timing and location of a heart murmur may suggest obstructive HCM. 

Diagnostic Tests

Diagnosis is typically done by echocardiogram. It checks the thickness of the heart muscle and blood flow from the heart. In some cases, another type of echocardiogram, transesophageal echo (or TEE), may be performed. A TEE is done using a probe inserted in the throat while the patient is under sedation.

Other diagnostic tests may include:

• Electrocardiogram (ECG)

• Cardiac MRI

• Stress tests

• Holter and event monitors

• Genetic testing

Diagnostic Procedures

Confirming diagnosis or preparing for surgery may also involve one or more medical procedures including:

• Cardiac catheterization

• Coronary angiography

Is HCM cureable? What treatments are available?

There are currently no disease-specific medications for hypertrophic cardiomyopathy.  

For people with HCM who don’t have symptoms, lifestyle changes and medications for conditions that may contribute to cardiovascular disease are recommended.

For those with symptoms, the focus is on symptom management using medications and procedures.

Medications

Medications called beta-blockers, calcium channel blockers and diuretics offer limited and varying relief of symptoms. They may help with function but may also have adverse side effects. 

Procedures

A range of surgical and nonsurgical procedures can be used to treat HCM:

• Septal myectomy – Septal myectomy is open-heart surgery. It’s considered for people with obstructive HCM and severe symptoms. This surgery is generally reserved for younger patients and for people whose medications aren’t working well. A surgeon removes part of the thickened septum that’s bulging into the left ventricle. This improves blood flow within the heart and out to the body.
  

• Alcohol septal ablation (nonsurgical procedure) – In this procedure, ethanol (a type of alcohol) is injected through a tube into the small artery that supplies blood to the area of heart muscle thickened by HCM. The alcohol causes these cells to die. The thickened tissue shrinks to a more normal size. The risks and complications of heart surgery increase with age. For this reason, ablation may be preferred to myectomy in older patients with other medical conditions.
  

• Surgically implanted devices – Surgeons can implant several types of devices to help the heart work better, including:

  • Implantable cardioverter defibrillator (ICD) – An ICD helps maintain a normal heartbeat by sending an electric shock to the heart if an irregular heartbeat is detected. This reduces the risk of sudden cardiac death.

  • Pacemaker – This small device uses electrical pulses to prompt the heart to beat at a normal rate.

  • Cardiac resynchronization therapy (CRT) device – This device coordinates contractions between the heart’s left and right ventricles.

• Heart transplant – In HCM patients with advanced, end-stage disease, a heart transplant may be considered. In this procedure, a person’s diseased heart is replaced with a healthy donor heart.

All information cited here have been gleaned from:

The American Heart Association

The Mayo Clinic