Congenital heart defects

Heart Disease

Types of congenital heart defect

Holes in the heart can occur:

  • In the upper chambers (atrial septal defects)
  • In tower chambers (ventricular septal defects)
  • Between all four chambers (atrioventricular septal defects)
  • In the great artery, which is called patent ductal arteriosus

The holes are part of the circulation system in the foetus but should close up after birth.

More complex conditions include¬†tetralogy of Fallot. The main symptom is cyanosis, and for this reason babies with this problem are commonly known as ‘blue babies’.

In tetralogy of Fallot, the baby has a large hole in the heart, allowing blood to pass from the right ventricle to the left without going through the lungs. There is a narrowing at or just below the pulmonary valve, the right ventricle is more muscular than normal and the aorta lies directly over the hole – the ventricular septal defect.

Babies may have rapid breathing or fall unconscious. Older children may become short of breath and faint.

An obstruction, or stenosis, can occur between the valves between the upper and lower chambers of the heart. More frequently, the obstruction is between the ventricles and trunks coming from them, either the valve to the lungs or the valve to the body.

Only severe aortic stenosis requires surgery, and some children may have the condition without showing any symptoms. The obstruction can also be within the vessels themselves. In this case, the narrowing is within the artery and effects supplies of blood to different parts of the body. This defect may not be picked up for many years.

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Organs – Heart

Heart Disease

Cardiac muscle

Your heart is an incredibly powerful organ. It works constantly without ever pausing to rest. It is made of cardiac muscle, which only exists in the heart. Unlike other types of muscle, cardiac muscle never gets tired.

Four chambers

Your heart is divided into four hollow chambers. The upper two chambers are called atria. They are joined to two lower chambers called ventricles. These are the pumps of your heart.

One-way valves between the chambers keep blood flowing through your heart in the right direction. As blood flows through a valve from one chamber into another the valve closes, preventing blood flowing backwards. As the valves snap shut, they make a thumping, ‘heart beat’ noise.

Double pump

Blood carries oxygen and many other substances around your body. Oxygen from your blood reacts with sugar in your cells to make energy. The waste product of this process, carbon dioxide, is carried away from your cells in your blood.

Your heart is a single organ, but it acts as a double pump. The first pump carries oxygen-poor blood to your lungs, where it unloads carbon dioxide and picks up oxygen. It then delivers oxygen-rich blood back to your heart. The second pump delivers oxygen-rich blood to every part of your body. Blood needing more oxygen is sent back to the heart to begin the cycle again. In one day your heart transports all your blood around your body about 1000 times.

Your right ventricle pumps blood to your lungs and your left ventricle pumps blood all around your body. The muscular walls of the left ventricle are thicker than those of the right ventricle, making it a much more powerful pump. For this reason, it is easiest to feel your heart beating on the left side of your chest.

Pacemaker

Unlike skeletal muscle cells that need to be stimulated by nerve impulses to contract, cardiac muscle cells can contract all by themselves. However, if left to their own devices, cardiac muscle cells in different areas of your heart would beat at different rates. Muscle cells in your ventricles would beat more slowly than those in your atria. Without some kind of unifying function, your heart would be an inefficient, uncoordinated pump. So, your heart has a tiny group of cells known as the sinoatrial node that is responsible for coordinating heart beat rate across your heart. It starts each heartbeat and sets the heartbeat pace for the whole heart.

Damage to the sinoatrial node can result in a slower heart rate. When this is a problem, an operation is often performed to install an artificial pacemaker, which takes over the role of the sinoatrial node.

Heart rate

Without nervous system control, your heart would beat around 100 times per minute. However, when you are relaxed, your parasympathetic nervous system sets a resting heart beat rate of about 70 beats per minute, (resting heart rate is usually between 72-80 beats per minute in women and 64-72 beats per minute in men).

When you exercise or feel anxious your heart beats more quickly, increasing the flow of oxygenated blood to your muscles. This is triggered by your sympathetic nervous system. Your heart rate also increases in response to hormones like adrenalin.

On average, your maximum heart rate is 220 beats per minute minus your age. So a 40 year old would have a maximum heart rate of 180 beats per minute.

Oxygen supply to your heart

Although your heart is continually filled with blood, this blood doesn’t provide your heart with oxygen. The blood supply that provides oxygen and nutrients to your heart is provided by blood vessels that wrap around the outside of your heart.

How Does a Pacemaker Work?

Heart Disease

A pacemaker consists of a battery, a computerized generator, and wires with sensors at their tips. (The sensors are called electrodes.) The battery powers the generator, and both are surrounded by a thin metal box. The wires connect the generator to the heart.

A pacemaker helps monitor and control your heartbeat. The electrodes detect your heart’s electrical activity and send data through the wires to the computer in the generator.

If your heart rhythm is abnormal, the computer will direct the generator to send electrical pulses to your heart. The pulses travel through the wires to reach your heart.

Newer pacemakers can monitor your blood temperature, breathing, and other factors. They also can adjust your heart rate to changes in your activity.

The pacemaker’s computer also records your heart’s electrical activity and heart rhythm. Your doctor will use these recordings to adjust your pacemaker so it works better for you.

Your doctor can program the pacemaker’s computer with an external device. He or she doesn’t have to use needles or have direct contact with the pacemaker.

Pacemakers have one to three wires that are each placed in different chambers of the heart.

The wires in a single-chamber pacemaker usually carry pulses from the generator to the right ventricle (the lower right chamber of your heart).
The wires in a dual-chamber pacemaker carry pulses from the generator to the right atrium (the upper right chamber of your heart) and the right ventricle. The pulses help coordinate the timing of these two chambers’ contractions.
The wires in a biventricular pacemaker carry pulses from the generator to an atrium and both ventricles. The pulses help coordinate electrical signaling between the two ventricles. This type of pacemaker also is called a cardiac resynchronization therapy (CRT) device.

The image shows a cross-section of a chest with a pacemaker. Figure A shows the location and general size of a double-lead, or dual-chamber, pacemaker in the upper chest. The wires with electrodes are inserted into the heart’s right atrium and ventricle through a vein in the upper chest. Figure B shows an electrode electrically stimulating the heart muscle. Figure C shows the location and general size of a single-lead, or single-chamber, pacemaker in the upper chest.

Types of Pacemaker Programming

The two main types of programming for pacemakers are demand pacing and rate-responsive pacing.

A demand pacemaker monitors your heart rhythm. It only sends electrical pulses to your heart if your heart is beating too slow or if it misses a beat.

A rate-responsive pacemaker will speed up or slow down your heart rate depending on how active you are. To do this, the device monitors your sinus node rate, breathing, blood temperature, and other factors to determine your activity level.

Your doctor will work with you to decide which type of pacemaker is best for you.

Heart Attack

Heart Disease

If you are having pain or discomfort in your chest, jaw, shoulder, arm, or back and think you may be having a heart attack, call 911 immediately. Do not delay or try to “wait it out.”

If you think you are having a heart attack, seek help immediately. Do not ignore chest pain or discomfort. Time is of vital importance. Go immediately to a hospital emergency department. Do not attempt to drive yourself or have someone else drive you. Call 911 for emergency transport.

The heart is a muscular pump located in the chest. Its job is to pump blood around the body via the circulatory system of blood vessels. The heart consists of 4 chambers: right atrium and right ventricle, and left atrium and left ventricle.

  • Blood is depleted of oxygen after circulating through the body. This blood returns into the right atrium. From there the blood flows into the right ventricle, which pumps the blood out to the lungs for oxygenation.
  • The oxygen-rich blood then returns to the left atrium. From there it flows into the left ventricle and is pumped out at high pressure into the arteries.

The high pressure is generated by powerful contraction of the heart muscle.

  • This raises the pressure of the blood and enables it to flow through the extensive network of arteries to every part of the body and return to the heart.
  • For this pumping action, the heart has to be strong.

The heart is nourished by the blood supplied directly to the heart muscle through the coronary arteries.

  • The strength of the heart muscle depends very much on this blood supply.
  • The coronary arteries are usually strong, elastic, and quite flexible. The inner lining of the arteries is normally smooth. This allows the blood to flow smoothly without clotting.

Heart attack is caused by sudden loss of blood and oxygen to your heart.

  • The most common condition that predisposes a person to heart attack is coronary heart disease, or coronary artery disease.
  • The plaque and resulting blood clots block the artery partially or completely, reducing the amount of blood that can flow through the artery to the heart.
  • This cuts off the oxygen supply to part of the heart muscle.
  • If the blood supply is cut off long enough, that part of the heart muscle dies. This is a heart attack.
  • If a large enough part of the heart muscle is affected, a dangerous rhythm disorder called ventricular fibrillation may occur.
  • If this happens, the heart may stop. This is called cardiac arrest, and most people who have cardiac arrest die.

Despite immense medical progress in the last 3 decades, heart disease continues to be a major health problem in both industrialized and developing nations.

  • About 1.5 million Americans suffer a heart attack each year (that?s 1 heart attack every 20 seconds).
  • Many people die before getting medical attention. Approximately 90-95% of people who reach a hospital alive after a heart attack will survive.
  • Overall, about one third of people who have a heart attack die.
  • Heart disease is the leading cause of death in the United States.

Clearly, time is of the essence. Recognizing the symptoms of a heart attack and seeking immediate medical attention may mean the difference between life and death.

  • Immediate death may be avoided if cardiopulmonary resuscitation (CPR) is begun within 4 minutes of the cardiac arrest.
  • CPR involves breathing for the person (mouth-to-mouth resuscitation) and performing chest compressions to keep the blood circulating. This provides at least a small amount of oxygen to the heart and brain.

Survival depends on quick action.

  • Emergency personnel will assess the situation quickly. They may record an electrocardiogram (ECG).
  • If the person has ventricular fibrillation or there is no pulse, they may administer electrical current to the chest (defibrillation) to “shock” the heart back to normal rhythm.
  • Other emergency treatments include medications and CPR.

Bystanders can help a cardiac arrest victim before emergency personnel arrive.

  • Ventricular fibrillation often can be treated successfully with a defibrillator.
  • Automated external defibrillators (AEDs) are now becoming available in many public places such as airports and airplanes, shopping malls, sports arenas, and office buildings.
  • These devices are designed so that they can be used in cardiac arrest by untrained bystanders.
  • Even if an AED is not available, you can take part in the “chain of survival” by performing CPR until help arrives.