Cardiology Introduction

Heart and vessel diseases (cardiovascular diseases) are the number-one killer in the world. Thanks to the great contribution of numerous physicians and scientists, lots of the heart and vessel diseases are nowadays not only treatable (even curable) but also preventable. Atherosclerosis-related diseases and cardiac arrhythmias comprise the major part of the cardiovascular diseases. Mackay Memorial Hospital, established in 1880 by a Canadian evangelist Dr. Mackay, is among the leading medical centers in Taiwan that can provide excellent quality of services in the treatment of these potentially fatal diseases.

What Are Atherosclerosis-related Diseases?

Atherosclerosis is a slow, progressive disease that may begin as early as early adolescence. A growing body of evidence suggests that atherosclerosis starts with damage or injury to the inner layer of an artery. The damage may be caused by various factors (See How to Prevent Atherosclerosis-related Diseases below). Once the inner wall of an artery is injured, blood cells called platelets often clump at the injury site to try to repair the artery. Over time, fatty deposits (plaques) made of cholesterol and other cellular waste products also accumulate and harden, narrowing the space in your arteries (See Figure below). Organs and tissues that are served by these narrowed vessels don’t get an adequate supply of blood. Eventually pieces of the fatty deposits may rupture and enter your bloodstream. This can cause a blood clot to form at the site and damage your organs, such as in a heart attack or stroke. Coronary artery disease (CAD) and peripheral arterial disease (PAD) are two common types of atherosclerosis-related diseases.

A. Normal artery
Normal blood flow
Artery wall
Artery cross-section

B. Narrowing of artery
Abnormal blood flow
Narrowed artery

What Is Coronary Artery Disease?

  • Coronary artery disease (CAD) is the most common type of atherosclerosis-related diseases. CAD happens when the arteries that supply blood to heart muscle (that is, coronary arteries) become hardened and narrowed due to atherosclerosis. As a result, the heart muscle is not able to get enough blood or oxygen it needs. This can lead to chest pain (angina) or a heart attack. Most heart attacks happen when a blood clot suddenly cuts off the hearts’ blood supply, causing permanent heart damage. Over time, CAD can also weaken the heart muscle and contribute to heart failure and cardiac arrhythmias (See the Cardiac Arrhythmia)

What Is Peripheral Arterial Disease?

  • Peripheral arterial disease (PAD) happens when there is a narrowing of the blood vessels outside of your heart. A substance made up of fat and cholesterol, called plaque (See What Are Atheroslcerosis-related Diseases above), builds up on the walls of the arteries that supply blood to the arms and legs. The plaque causes the arteries to narrow or become blocked. This can reduce or stop blood flow, usually to the legs, causing them to hurt or feel numb, especially during walking or exercise. If severe enough, blocked blood flow can cause tissue death. If this condition is left untreated, the foot or leg may need to be amputated. A person with PAD also has an increased risk of heart attack and stroke.

How to Prevent Atherosclerosis-related Diseases?

  • The best way to prevent atherosclerosis-related diseases is to reduce the modifiable risk factors, which include high blood pressure (hypertension), high cholesterol and/or triglyceride and/or low high-density lipoprotein (HDL) cholesterol (dyslipidemia), diabetes and smoking.

High Blood Pressure

High blood pressure is called the silent killer because it sometimes has no symptoms. When high blood pressure is not found and treated, it can result in troubles with the vessels, heart, brain, or kidneys.

What Is Blood Pressure?

  • Blood is carried from the heart to all parts of your body in vessels called arteries. Blood pressure is the force of the blood pushing against the walls of the arteries. Each time the heart beats, it pumps out blood into the arteries. Your blood pressure is at its highest when the heart beats, pumping the blood. This is called systolic pressure. When the heart is at rest, between beats, your blood pressure falls. This is the diastolic pressure. Blood pressure is always given as these two numbers, the systolic and diastolic pressures. Both are important. Blood pressure changes during the day. It is lowest as you sleep and rises when you get up. It also can rise when you are excited, nervous, or active.

What Is Normal Blood Pressure?

  • A blood pressure reading below 120/80 mmHg is considered normal. In general, lower is better. However, very low blood pressure can sometimes be a cause for concern and should be checked out by a doctor.

What Is High Blood Pressure?

Categories for Blood Pressure Levels in Adults (in mmHg, millimeters of mercury)bloodpressureFor adults 18 and older who are not on medicine for high blood pressure; are not having a short-term serious illness; and do not have other conditions, such as diabetes and kidney disease.


  1. When systolic and diastolic blood pressures fall into different categories, the higher category should be used to classify blood pressure level.
  2. Although the systolic blood pressure is, generally speaking, going up with age, the definition of the high blood pressure remains the
    same. For example, an 80-year-old gentleman with a systolic blood pressure of 145 mmHg is still considered to be hypertensive.
  3. If you are being treated for high blood pressure and have repeated readings in the normal range, you still have high blood pressure.
  4. If your blood pressure is in the pre-hypertension range, it is more likely that you will end up with high blood pressure unless you take action to prevent it.
  5. There is an exception to the above definition of high blood pressure. A blood pressure of 130/80 mmHg or higher is considered high blood pressure in people with diabetes and chronic kidney disease.

How to Prevent and Treat High Blood Pressure?

  • There are some steps you can take to prevent high blood pressure, such as keeping a healthy body weight, doing regular exercise, choosing and preparing food with less salt, as well as limiting alcohol intake. If your blood pressure levels remain high, even after you take the aforementioned steps, you will need blood pressure medicines. These medicines work in different ways to lower blood pressure. Often, two or more medicines work better than one and may be needed to achieve optimal blood pressure control. Furthermore, different classes of blood pressure medicines may have different additional actions other than lowering blood pressure, and doctors will prescribe different medicines according to individual conditions. Therefore, a good and effective regimen for one patient is not necessarily good or suitable for another. It is also important that you take your blood pressure medicine at the same time each day and do not skip days or cut pills in half before consulting your doctor, even you have an ideal blood pressure level.
  • Treating high blood pressure is one of the most effective ways to prevent atherosclerosis-related diseases. Generally speaking, a 2-mmHg decrease in systolic blood pressure is able to reduce 7% death from the heart attack and 10% death from the stroke.

High Cholesterol, High Triglyceride and Low High-density Lipoprotein Cholesterol

What Is Cholesterol?

Cholesterol is a waxy, fat-like substance that is found in all cells of the body. Your body needs some cholesterol to work the right way. In addition, your body also uses cholesterol to make hormones, vitamin D, and substances that help you digest foods. Basically, your body is able to make the cholesterol it needs, but cholesterol is also found in some of the foods you eat.
Blood is watery, and cholesterol is fatty. Just like oil and water, the two do not mix. To travel in the bloodstream, cholesterol is carried in small packages called lipoproteins. The small packages are made of fat (lipid) on the inside and proteins on the outside.
Two kinds of lipoproteins carry cholesterol throughout your body. It is important to have healthy levels of both: Low-density lipoprotein (LDL) cholesterol is sometimes called “bad” cholesterol. High LDL cholesterol leads to a deposit of cholesterol in arteries, a process called “atherosclerosis” (Also see Atherosclerosis-related Diseases). The higher the LDL level in your blood, the greater chance you have of getting atherosclerosis-related diseases. High-density lipoprotein (HDL) cholesterol is sometimes called “good” cholesterol. HDL carries cholesterol from other parts of your body back to your liver, where the cholesterol is removed from your body. The higher your HDL cholesterol level, the lower your chance of getting atherosclerosis-related diseases.

What Is High Blood Cholesterol?

Too much cholesterol in the blood, or high blood cholesterol, can be serious. People with high blood cholesterol have a greater chance of getting atherosclerosis-related diseases. High blood cholesterol on its own does not cause symptoms, so many people are unaware that their cholesterol level is too high.
Cholesterol levels are measured in milligrams (mg) of cholesterol per deciliter (dL) of blood. See how your cholesterol numbers compare to the tables below.


How Is High Blood Cholesterol Treated?

  • The main goal of cholesterol-lowering treatment is to lower your low-density lipoprotein (LDL) level enough to reduce your risk of having a heart attack or diseases caused by hardening of the arteries. In general, the higher your LDL level and the more risk factors you have, the greater your chances of developing heart disease or having a heart attack. (A risk factor is a condition that increases your chance of getting a disease.) Some people are at high risk for heart attack because they already have heart disease. Other people are at high risk for developing heart disease because they have diabetes or a combination of risk factors for heart disease. Follow the steps below to find out your risk for getting heart disease.

Check the list to see how many of the risk factors you have. These are the risk factors that affect your LDL goal:

  • Cigarette smoking
  • High blood pressure (140/90 mg/dL or higher), or if you are on blood pressure medicine
  • Low high-density lipoprotein (HDL) cholesterol (less than 40 mg/dL)
  • Family history of early heart disease (heart disease in father or brother before age 55; heart disease in mother or sister before age 65)
  • Age (men 45 years or older; women 55 years or older)

Use your medical history and number of risk factors to find your risk of developing heart disease or having a heart attack according to the table below.


After following the above steps, you should have an idea about your risk for getting heart disease or having a heart attack. The higher your risk is, the lower your LDL goal will be.

What Is Triglyceride?

  • Triglycerides are a form of fat carried through the bloodstream. Most of your body’s fat is in the form of triglycerides stored in fat tissue. Only a small portion of your triglycerides is found in the bloodstream. High blood triglyceride levels alone do not necessarily cause atherosclerosis (See Atherosclerosis-related Diseases). But some lipoproteins that are rich in triglycerides also contain cholesterol, which causes atherosclerosis in some people with high triglycerides, and high triglycerides are often accompanied by other factors (such as low HDL or a tendency toward diabetes) that raise heart disease risk. Therefore, high triglycerides may be a sign of a lipoprotein problem that contributes to heart disease.


  • Diabetes is a disease in which your blood glucose, or sugar, levels are too high. Glucose comes from the foods you eat. Insulin is a hormone that helps the glucose get into your cells to give them energy. With Type 1 diabetes, your body does not make insulin. With Type 2 diabetes, the more common type, your body does not make or use insulin well. Without enough insulin, the glucose stays in your blood.
  • Over time, having too much glucose in your blood can cause serious problems. It can damage your vessels, causing atherosclerosis and thus resulting in heart attack (CAD), stroke and even the need to remove a limb (PAD) (See Atherosclerosis-related Diseases). In addition, diabetes also damages your eyes, kidneys, and nerves.
  • Symptoms of Type 2 diabetes may include fatigue, thirst, weight loss, blurred vision and frequent urination. Some people have no symptoms. A blood test can show if you have diabetes. Exercise, weight control and sticking to your meal plan can help control your diabetes. You should also monitor your glucose level and take medicine if prescribed. You can get more detailed informations from the website:


  • Tobacco use is the most common preventable cause of death. About half of the people who don’t quit smoking will die of smoking-related problems. Quitting smoking is important for your health and provides many benefits. Soon after you quit, your circulation begins to improve, and your blood pressure starts to return to normal. Your sense of smell and taste return and breathing starts to become easier. In the long term, giving up tobacco can help you live longer. Your risk of getting atherosclerosis-related diseases and cancer decreases with each year you stay smoke-free. For the detailed information of how to quit smoking, please visit:

How to Diagnose Atherosclerosis-related Diseases?

We establish the diagnoses by clinical symptoms or signs, medical history, risk factors, physical examination, as well as diagnostic tests.

What Are the Symptoms or Signs of Coronary Artery Disease?

  • Pain, tightness or discomfort in other areas of the upper body including the arms, left shoulder, back, neck, jaw, or stomach
  • Difficulty breathing or shortness of breath
  • Sweating or “cold sweat”
  • Fullness, indigestion, or choking feeling (may feel like “heartburn”)
  • Nausea or vomiting
  • Light-headedness, dizziness, extreme weakness or anxiety
  • Rapid or irregular heart beats

What Are the Symptoms or Signs of Peripheral Arterial Disease?

  • At least half of the people who have peripheral arterial disease (PAD) don’t have any signs or symptoms of the disease.
  • Pain when walking or climbing stairs, which may be relieved after resting. This pain is called intermittent claudication. About 10 percent of people with PAD have intermittent claudication.
  • Pain, numbness, aching, and heaviness in the muscles
  • Cramping in the legs, thighs, calves, and feet
  • A weak or absent pulse in the legs or feet
  • Sores or wounds on toes, feet, or legs that heal slowly, poorly, or not at all
  • Color changes in skin, paleness, or blueness (called cyanosis)
  • A decreased temperature in one leg compared to the other leg
  • Poor nail growth and decreased hair growth on toes and legs
  • Erectile dysfunction, especially among people with diabetes

What Are the Diagnostic Tests for Coronary Artery Disease?

  • Eectrocardiogram (ECG): It can be used to detect whether there are signs of inadequate blood supply to the heart.
  • Treadmill Exercise Test: It uses the electrocardiogram to evaluate the electrical activity generated by the heart at rest and with activity.
  • Nuclear Imaging: It produces images by detecting radiation from different parts of the heart after the administration of a radioactive tracer material (Thallium scan) to reveal the perfusion of the heart.
  • Invasive Testing: It involves inserting catheters into the blood vessels of the heart in order to get a closer look at the coronary arteries, such as cardiac catheterization and coronary angiogram.

What Are the Diagnostic Tests for Peripheral Arterial Disease?

  • Ankle-brachial index (ABI): ABI can be used to diagnose PAD. The ABI compares blood pressure in the ankle with blood pressure in the arm to see how well blood is flowing. A normal ABI is 1.0 or greater (with a range of 0.90 to 1.30). The test takes about 10–15 minutes to measure both arms and both ankles.
    It can help the doctor find out if PAD is affecting the legs, but it will not identify which blood vessels are blocked. The ABI can be performed yearly if necessary to see if the disease is getting worse.
    The illustration shows the ankle-brachial index (ABI) test. The ABI gives the ratio of the systolic blood pressure in the ankle to the systolic blood pressure in the brachial artery of the arm.
  • Doppler Ultrasound: It is a test that uses sound waves to tell whether a blood vessel is open or blocked. This test uses a blood pressure cuff and special device to measure blood flow in the veins and arteries in the arms and legs. The Doppler ultrasound can help to determine the level and degree of PAD.
  • Treadmill Exercise Test: It will provide more information on the severity of the symptoms and the level of exercise that provokes symptoms. For this test, you will walk on a treadmill, which will help identify any difficulties that you may have during normal walking.
  • Magnetic Resonance Angiogram (MRA): It uses radio wave energy to take pictures of blood vessels inside the body. MRA is a type of magnetic resonance imaging (MRI) scan. An MRA can detect problems that may cause reduced blood flow in the blood vessels. It can determine the location and degree of blockage. A
    patient with a pacemaker, prosthetic joint, stent, surgical clips, mechanical heart valve, or other metallic devices in his or her body might not be eligible for an MRA depending on the type of metallic device.
  • Peripheral Angiogram: It is a “road map” of the arteries used to pinpoint the exact location of the blockage in a limb. An x ray is taken after injecting dye through a needle or catheter into an artery. When the dye is injected, the patient may feel mildly flushed. The pictures from the x ray can determine the location,
    type, and extent of the blockage. Some hospitals are using a newer method that uses tiny ultrasound cameras to take pictures inside the blood vessel.

How to Treat Atherosclerosis-related Diseases?

Treatment of CAD or PAD is in order to control symptoms and slowing the progression of disease. The method of treatment is based on many factors determined by symptoms, a physical examination, and diagnostic testing. Life style modification and drugs are suggested initially and series tests are arranged to evaluate the severity of the diseases. If your symptoms could not be controlled by medication and life style modification and diagnostic studies reveal compatible evidence of CAD or PAD, further evaluations about the anatomy of clogged or narrowed coronary or peripheral arteries are indicated.

How to Evaluate the Anatomy of Heart Arteries?

  • Coronary arteriogram or multislice CT angiography could reveal the anatomy of clogged heart arteries.

How to Treat Coronary Artery Disease by Medical Therapy?

  • In many cases, if the blockage is less than 70 percent, medications may be the first line of treatment. Risk factor reduction is the most important part of the medical therapy (Also see How to Prevent Atherosclerosis-related Diseases?). This includes: stopping smoking and the use of tobacco products, lowering high blood cholesterol, controlling high blood pressure, maintaining tight diabetes control, following a regular exercise plan, achieving and maintaining your ideal body weight, and controlling stress and anger.

What Is Coronary Angiogram?

The first step is a diagnostic picture of the arteries, called a coronary angiogram or catheterization. The needle puncture is made, using a local anesthetic. The physician then threads a catheter through the entry site and follows the main artery in the body, called the aorta, up and around into the opening of the left, or right, coronary artery (See Figure left). Through this hollow catheter, the physician injects a small amount of special dye, called contrast, which, when viewed in motion under X-rays, reveals any obstructions or plaques located within the coronary vessels. When the dye is injected, the patient may feel a warm sensation. Views from several camera angles are recorded on motion picture film (see the example picture below).

Who Needs Coronary Angioplasty?

  • When medications or lifestyle changes aren’t enough to reduce the symptoms of artery blockages, or if you have a heart attack, worsening chest pain or other symptoms, your doctor might suggest angioplasty. We can use coronary angiogram or multislice CT angiography to determine if your blockages can be treated with angioplasty.

You may be a good candidate for an angioplasty if:

  • Your blockage is small
  • Your blockage can be reached by angioplasty
  • The artery affected isn’t the main vessel supplying blood to the left side of your heart.

In certain conditions, bypass surgery may be more suitable than angioplasty. These may include:

  • The main artery supplying the left side of your heart is narrowed
  • Small, diffusely diseased blood vessels
  • Diabetes and multiple blockages, especially if you have signs of heart failure

The final decision will depend on the details of your heart disease and overall medical condition.

What Happens During An Angioplasty?

  • After change the diagnostic catheter to a guiding catheter, physicians can also pass a variety of instruments through the catheter and into the artery to a lesion site.

Balloon Angioplasty

  • Coronary angioplasty is accomplished using a balloon-tipped catheter inserted through an artery in the groin or arm to enlarge a narrowing in a coronary artery.

Coronary Stents

  • Once the artery is widened, a device called a stent is usually placed in the artery to act as scaffolding to help prevent it from re-narrowing after the angioplasty. The stent looks like a very tiny coil of wire mesh.

Drug-eluting Stents

  • Stents can be coated with drug that’s slowly released to help prevent arteries from re-clogging or re-narrowing. These coated stents are called drug-eluting stents (DES). There has been considerable research showing the benefits of drug-eluting stents. However, not every patient is suitable for drug-eluting stents. The final decision of whether you would be benefited with durg-eluting stents will depend on the details of your vessel and overall medical conditions.

Cutting Balloon

  • It has a special balloon tip with small blades, which are activated when the balloon is inflated, and are able to effectively widen the narrowed vessels, thus limiting the vessel trauma. The advantage of the cutting balloon is its ability to reduce vessel stretch and vessel injury by scoring the vessel longitudinally rather than causing an uncontrolled disruption of the atherosclerotic plaque.


  • A rotating atherectomy catheter (100,000 to 190,000 rpm) with an olive shaped metal tip on which diamond splinters are attached. The olive at the tip measures 1.5-4.5 mm and can be advanced over a guide wire. It is used for heavily calcified lesions in the peripheral arteries as well as in the coronary system.

Intravascular Ultrasound (IVUS)

  • IVUS is a medical imaging system using a specially designed catheter with a miniaturized ultrasound probe attached to the distal end the catheter. It allows the application of ultrasound technology to see from inside blood vessels out through the surrounding blood column, visualizing the inner wall of blood vessels in living individuals. IVUS is used in the coronary arteries to determine the amount of plaque built up at any particular point in the coronary artery. IVUS is of use to determine both plaque volumes within the wall of the artery and/or the degree of the narrowing of the vessel, as shown by the representative pictures below. It can be especially useful in situations in which angiographic imaging is considered unreliable; such as for the lumen of ostial lesions or for where angiographic images do not visualize lumen segments adequately, such as regions with multiple overlapping arterial segments. It is also used to assess the effects of angioplasty and the results of medical therapy over time.

The Recovery Period

You’ll probably remain hospitalized a day — in rare cases two or more days — while your heart is monitored and your vital signs are checked frequently. Your doctor will likely prescribe medications (such as anticoagulants) to prevent blood clots, relax your arteries and protect against coronary spasms.
When you return home, drink plenty of fluids to help rid your body of the contrast dye. Avoid strenuous exercise and lifting heavy objects for several days afterward. Ask your doctor or nurse about other restrictions in activity.
Call your doctor’s office or hospital staff immediately if:
● The catheter insertion site starts bleeding or swelling
● You develop increasing pain or discomfort at the insertion site
● You have signs of infection, such as redness, drainage or fever
● There’s a change in temperature or color of the leg or arm that was used for the procedure
● You feel faint or weak
● You develop chest pain or shortness of breath
You should be able to return to work or your normal routine the week after angioplasty.

Benefits of Angioplasty

  • As with most medical procedures, angioplasty has both benefits and risks.
    Among the benefits are:
  • It doesn’t require a major incision.
  • You don’t need general anesthesia.
  • Major complications are uncommon.
  • It can relieve your symptoms, such as chest pain.

Risks of Angioplasty

  • Restenosis. This means the re-narrowing or re-occlusion of the angioplasty-treated vessels. According the literature, without stent placement — restenosis happens in as many as 30 percent to 40 percent of cases; the bare-metal stents reduce the chance of restenosis to less than 20 percent; and the drug-eluting stents is able to reduce the risk to less than 10 percent.
  • Blood clots. The stent placement may incur the risk of clot formation, regardless of the type of stent placed. Therefore, it is absolutely necessary to take aspirin, clopidogrel (Plavix) and other medications as prescribed to decrease the chance of clots forming in the stent.Other risks of angioplasty include:
  • Bleeding. You may experience heavy bleeding, requiring a transfusion or other medical procedures.
  • Damage. Your artery may be damaged during the procedure, requiring emergency bypass surgery.
  • Heart attack. You may have a heart attack during the procedure, though large heart attacks are rare.
  • Ongoing disease. The procedure doesn’t fix the underlying cause of the blocked artery, which means other parts of the artery and other arteries can become blocked.

Blood Thinners

  • Most people who have undergone angioplasty with or without stent placement will need to take aspirin for life. Those who have had stent placement will need clopidogrel for six to 12 months or longer in some cases. If you need non-cardiac surgery, you should talk to your cardiologist before stopping any of these medications.

After You Go Home…

  • Most people who have angioplasty and stent placement do well, often for many years. However, if you have recurrent symptoms of chest pain or shortness of breath, or other symptoms similar to those before your procedure, you should contact your doctor. If you have chest pain at rest or pain that doesn’t respond to nitroglycerin, you should call for emergency medical help.

How to Treat Peripheral Arterial Disease?

Goals of Treatment
The overall goals for treating peripheral arterial disease (PAD) are to reduce symptoms, improve quality of life, and prevent complications.

Non-invasive Treatments

  • The non-invasive treatments for PAD include lifestyle changes and medicines, which are similar to those for CAD (See How to Treat Coronary Artery Disease?).


  • Surgery may be necessary if blood flow in a limb is completely or almost completely blocked. In bypass grafting surgery, the doctor uses a blood vessel from another part of your body or a tube made of synthetic (man-made) material to make a graft. This graft bypasses the blockage in the artery, allowing blood to flow around it. Surgery does not cure PAD, but it may increase blood flow to the limb.

Peripheral Angioplasty

  • Most people who have undergone angioplasty with or without stent placement will need to take aspirin for life. Those who have had stent placement will need clopidogrel for six to 12 months or longer in some cases. If you need non-cardiac surgery, you should talk to your cardiologist before stopping any of these medications.

Cell Therapy

  • Cell and gene therapies are currently being researched, but are not yet available outside of clinical trials. The research team at Mackay Memorial Hospital is now engaging in translating basic research results into clinical use, and clinical trials will be underway soon.

Cardiac Arrhythmia - Normal Electrical Activity in the Heart

The heart is made of muscle and linked by valves that act as doorways. It is comprised of four chambers; the two upper chambers are called the atria, and the lower called the ventricles. The heart’s natural pacemaker, the sinus node, is located at the upper portion of the right atrium and triggers the heartbeat. The heartbeat signal initially causes both of the atria to contract, then travels through the atrioventricular node, or “A-V node”, (the only electrical connection between the atria and the ventricles) and the His-Purkinje fibers (a group of modified heart muscle fibers in the ventricles that conduct the electrical signal) to all parts of the ventricles. This causes the ventricles to contract and produces a heartbeat. In normal adults, the heart beats regularly at a rate of 60 to 100 times per minute. However, this normally occurs 60 to 80 times a minute when a person is at rest.

What are arrhythmias?

  • Arrhythmias (abnormal heart rhythms) are problems that affect the electrical system of the heart. An arrhythmia occurs when the sinus node develops an abnormal rate, or the normal conduction pathway is interrupted or another part of the heart takes over as pacemaker. They can cause the heart to pump less effectively. Cardiac arrhythmias can be classified according to their effect on the heart rate, with bradycardia indicating a heart rate of less than 60 beats per minute and tachycardia indicating a heart rate of more than 100 beats per minute.

Risk factors causing arrhythmias

  • Some arrhythmias have no known cause. However, many conditions can increase the likelihood of developing arrhythmias. They include coronary artery disease, heart failure, high blood pressure, diabetes, hyperthyroidism, anemia, a family history of heart disease, advancing age, obesity, smoking, high cholesterol diet, excessive use of alcohol or caffeine, certain medications, drug abuse and stress. Some herbs and other substances used in over-the-counter remedies are also known to cause arrhythmias in some people.

Signs and symptoms

  • The commonest symptom of arrhythmia is an abnormal awareness of heartbeat, termed palpitations. These may be frequent, infrequent, or continuous. If an arrhythmia results in a heart beat that is too fast, too slow or too weak to supply the body’s needs, this may cause fatigue, dizziness, lightheadedness, fainting or even fatal.
    Some arrhythmias do not cause symptoms, but may associate with adverse events. These may include increase in risk of blood clotting within the heart. If part of a blood clot leaves the heart and lodges in an artery, it will increase the risk of stroke or sudden cardiac death.


  • Cardiac arrhythmias are often first detected by auscultation of the heartbeat with a stethoscope, or feeling for peripheral pulses. These cannot usually diagnose specific arrhythmias, but can give a general indication of the heart rate and whether it is regular or irregular.
    The simplest specific diagnostic test for assessment of heart rhythm is the electrocardiogram (ECG).The ECG takes about ten minutes from start to finish. There are no needles used and the test is painless. Sometimes, patients are required to remain still and hold their breath for short periods of time. It is a safe, commonly performed heart test that rarely causes discomfort. However, because cardiac arrhythmias may come and go, a one-time office EKG may be normal. If this is the case, a Holter monitor may be required. It is an EKG recorded over a 24-hour period, to detect arrhythmias that may happen briefly and unpredictably throughout the day.
    Some patients may need an electrophysiologic, or EP study to unmask suspected arrhythmias. Although it is more invasive than an electrocardiogram (ECG), the test produces data that makes it possible to diagnose infrequent arrhythmias and their sources. The effectiveness of certain medications in controlling the heart rhythm disorder can also be evaluated.
    This procedure is done using local anesthesia. Three to five long, thin tubes (catheters) are placed into the blood vessels in the legs and neck. Then the tips of the catheters are moved into the heart where they stimulate the heart at programmed rates and record electrical signals. These recordings locate abnormal tissue that causes arrhythmias.


  • The first step in treating any arrhythmia is determining the underlying cause of the problem. Then, treatment can be carefully selected by a patient with their physician. In general, the arrhythmia warrants treatment only when it causes symptoms or increases complications of arrhythmias in the future. The least invasive treatment that effectively controls the arrhythmia is the treatment of choice. Options include lifestyle changes, medication, ablation procedures, and surgery, including the implantation of pacemakers and defibrillators.