This section will provide you with information about:

• The normal heart rate
• Heart rate and rhythm differences between men and women
• Differences in abnormal heart rhythms in men and women
• Symptoms of irregular heart rhythms
• Hormones and Irregular heart beats
• How are arrhythmias diagnosed?
• Management of irregular heart rhythms in women
• Arrhythmias and pregnancy

The normal heart rate

The Heart's Electrical System

The heart’s rhythm is coordinated by its own electrical system. With each heartbeat, the electrical impulse begins at the sinus (or sinoatrial, SA) node, also called the heart’s natural pacemaker. The SA node is a cluster of specialized cells, located in the right atrium. The SA node produces the electrical impulses that set the rate and rhythm of your heartbeat. The impulse spreads through the walls of the right and left atria, causing them to contract, forcing blood into the ventricles.

The impulse then reaches the atrioventricular (AV) node, which acts as an electrical bridge allowing impulses to travel from the atria to the ventricles. There is a short delay before the impulse travels on to the ventricles.
From the AV node, the impulse travels through a pathway of fibers called the HIS-Purkinje network. This network sends the impulse into the ventricles and causes them to contract. The contraction forces blood out of the heart to the lungs and body.

The SA node fires another impulse and the cycle begins again.

The heartbeat is triggered by electrical impulses that travel down a special pathway through your heart muscle.

Heart rate and rhythm differences between men and women

Women and men are similar when it comes to the basic heart rate and rhythm. However, while the basic electrical system is the same (impulses originating in the SA node, traveling to the AV node, through the HIS-Purkinje, and then starting over), there are differences:

• Women tend to have a faster baseline heart rate
• Women’s ECG readings may be different

Women Have a Faster Baseline Heart Rate Than Men
First of all, on average, women tend to have a faster baseline heart rate than men. This difference is seen in girls, on an average, as young as five years old. There is also a shorter sinus node refractory time – this means that it takes a shorter time for the SA node to recover and become ready to fire an impulse again¹.

Women’s ECG Readings may be Different
The ECG (also called EKG or electrocardiogram) is a test used to record on graph paper the electrical activity of the heart. The picture, drawn by a computer from information supplied by electrodes placed on the skin of the chest, arms and legs, shows the timing of the different phases of the heart rhythm.

The p wave represents the electrical activity of the upper chambers of the heart (atria). There is a short pause followed by the QRS complex - the electrical activity of the lower chambers (ventricles) - and ends with a small T wave, the recovery phase of the ventricles. The QT interval is the distance from the beginning of the QRS to the end of the T wave and represents the time it takes for the heart muscle to contract and then recover, or for the electrical impulse to fire and then recharge.

On average, the QT interval is shorter in men than in women, beginning after puberty with a linear increase through the major part of adulthood to at least age 55. This period corresponds to the time period when androgen levels are highest in men. Therefore, androgen and estrogen levels may explain the gender differences in QT interval².

Differences in abnormal heart rhythms in men and women

Certain types of arrhythmias are more prevalent in women than in men. These include:

• Supraventricular Tachycardia (SVT) or Paroxysmal SVT (PSVT) – a rapid heart rate that originates above the AV node, in the atria. SVT is common in both men and women, but more women have AV node reentrant tachycardia and atrial tachycardia¹.
• Sinus Node Dysfunction (also called sick sinus syndrome) – a slow or irregular heart rhythm that originates in the SA node. The signal starts in the SA node but may be slow or delayed in progressing to the atria, causing a very slow or irregular heart beat.
• AV Nodal Re-entry Tachycardia (AVNRT) - a type of SVT with a fast heart rate that originates in the AV node. Instead of the AV node sending the impulse down one pathway, there are two pathways through the AV node. The impulses travel through one pathway as well as back up through the second pathway. This allows the impulses to travel around the AV node very quickly in a circular fashion, causing the heart to beat unusually fast.
• Long QT Syndrome - a QT interval longer than normal. This increases the risk for life-threatening forms of ventricular tachycardia.
• Postural Orthostatic Tachcyardia Syndrome (POTS) - a condition that affects 500,000 Americans, primarily women. Those with POTS have an abnormal response to change in position, related to the autonomic nervous system, causing drop in blood pressure, raise in heart rate and sometimes syncope (passing out), dizziness or lightheadedness ².

These arrhythmias occur more often in men, but may present differently in women:

• Atrial fibrillation - one of the most common irregular heart rhythms. It is a rapid irregular heart rhythm originating in the atria. Men have atrial fibrillation more often than women. Atrial fibrillation can be associated with other types of heart disease. Women are more likely to have atrial fibrillation associated with valve disease, while men more often have atrial fibrillation associated with coronary artery disease. The incidence of atrial fibrillation increases in both men and women with age, and when they also have hypertension and diabetes. The Coppenhagen Heart Study showed that women with atrial fibrillation had an increased risk for stroke and cardiovascular death as compared to men. This is particularly true in women who have atrial fibrillation and are older than age 75^3,4.

  Women who have paroxysmal atrial fibrillation, a type of atrial fibrillation that is intermittent (or comes and goes), may have a faster heart rate response than men, and tend to have longer episodes⁵.

• Sudden cardiac death is a sudden, unexpected death caused by loss of heart function (sudden cardiac arrest). Sudden cardiac death (SCD) occurs less frequently in women, but is still related to about 400,000 deaths per year in women. The Nurses’ Health Study showed that while the majority of women who had SCD had no prior history of cardiovascular disease before death, they had at least one cardiac risk factor (smoking, hypertension and diabetes had the greatest impact). Family history also played a role in increased risk if one parent died of heart disease before age 60. The study also showed that as with men, the majority of SCD in women was related to an irregular heart rhythm (88%) ^5-7. This reinforces the need for careful screening of heart disease risk factors in women and managing these concerns even without symptoms present.

Symptoms of irregular heart rhythms

An arrhythmia may be "silent" and not cause any symptoms. A doctor can detect an irregular heartbeat during an examination by taking your pulse, listening to your heart or by performing diagnostic tests.

If symptoms occur, they may include:

• Palpitations -- a feeling of skipped heart beats, fluttering, "flip-flops" or feeling that the heart is "running away"
• Pounding in the chest
• Dizziness or feeling light-headed
• Shortness of breath
• Chest discomfort
• Weakness or fatigue (feeling very tired)

Symptoms of palpitations represent 15-25 percent of all the symptoms reported by female heart patients. They are associated with:

• Premenstrual syndrome
• Pregnancy
• Perimenopausal period

When palpitations are present, the doctor begins his or her evaluation by looking for underlying heart disease. The importance of palpitations and the need for treatment is determined by the presence of underlying heart disease, the type of irregular heart beats that are occurring and other symptoms that are present.

Hormones and Irregular Heart Beats

Estrogen and progesterone levels rise and fall in women with a normal menstrual cycle during the days of the month. The rise of progesterone and the fall of estrogen correspond with:

• More frequent episodes of supraventricular tachycardia (SVT)
• More symptoms associated with SVT
• SVT of longer duration¹

During perimenopause (the time period before menopause), there is a marked decrease in ovarian estrogen production. This is associated with an increase in heart rate (sinus tachycardia) and an increased frequency in palpitations and non-threatening arrhythmias, such as premature ventricular contractions or PVCs.

Menopause causes a further decline in estrogen as the menstrual cycle stops. This time period is associated with irregular heart beats, palpitations, spasmodic chest pain and nightmares in women 40 -64 years old².

The Heart and Estrogen/Progestin Replacement Study (HERS) found no benefit in use of hormone replacement therapy to reduce cardiovascular events, and hormone replacement therapy may even increase risk of thromboembolism (blood clot) during the first year³. HRT is also associated with lengthening the QT interval [link to explanation above], although the relevance of this finding is not known⁴. On the other hand, HRT may decrease palpitations and other symptoms such as hot flashes, insomnia, and sweating. Therefore, it may be considered a treatment option in low risk female patients to relieve symptoms of palpitations.

How are arrhythmias diagnosed?

If you have symptoms of an arrhythmia, you should make an appointment with a cardiologist. You may want to choose an electrophysiologist, a cardiologist who has received additional specialized training in the diagnosis and treatment of heart rhythm disorders.

After evaluating your medical history and discussing your symptoms, a physical exam will be performed. The cardiologist also may perform a variety of diagnostic tests to help confirm the presence of an arrhythmia and determine its causes.

Some tests that may be done to confirm the presence of an irregular heart rhythm include:

• ECG
• Ambulatory Monitor
• Stress Test
• Echocardiogram
• Electrophysiology Test
• Head Upright Tilt Test

Management of Irregular Heart Rhythms in Women

Treatment options include:

• Medications
• Lifestyle changes
• Invasive therapies
• Electrical devices
• Surgery

Medications -- antiarrhythmic drugs are medications used to convert the arrhythmia to a normal sinus rhythm or to prevent an arrhythmia. Other medications may include heart-rate control drugs; anticoagulant or antiplatelet drugs such as warfarin (a "blood thinner") or aspirin, which reduce the risk of blood clots or stroke.

Concerns for women: Because women have a longer QT interval than men. some medications that are used in men to treat irregular heart rhythms prolong the QT interval even more. These medications include: Quinidine, Sotolol, Dofetilide and Amiodarone. These medications may increase a woman's risk of developing a life-threatening arrhythmia (torsades de pointes) more than in men who take these medications. Women who take these medications should follow their’ doctor’s and dietitian’s dietary guidelines for potassium and avoid becoming low in potassium, which enhances the arrhythmia affect¹.

The biggest concern for all patients with atrial fibrillation is preventing blood clots or stroke. Warfarin (also called Coumadin) is most often used to prevent strokes in patients. According to the The Canadian Registry of Atrial Fibrillation (CARAF), women were half as likely to be prescribed warfarin as compared to men, although they would benefit from it as much².

Lifestyle changes – arrhythmias may be related to certain lifestyle factors. Here are some ways to change these factors:

• If you smoke, stop. [learn more]
• Limit your intake of alcohol. [learn more]
• Limit or stop using caffeine. Some people are sensitive to caffeine and may notice more symptoms when using caffeinated products (such as tea, coffee, colas, chocolate and some over-the-counter medications).
• Avoid certain stimulants. Beware of stimulants used in cough and cold medications and herbal or nutritional supplements. Some of these substances contain ingredients that cause irregular heart rhythms. Read the label and ask your doctor or pharmacist what medication would be best for you.

Invasive therapies – the following invasive therapies may be used to treat or eliminate irregular heart rhythms. Your doctor will discuss the benefits and risks of these therapies and whether they are appropriate treatments for your condition.

• Electrical cardioversion -- in patients with persistent arrhythmias (such as atrial fibrillation), a normal rhythm may not be achieved with drug therapy alone. After administering a short-acting anesthesia, an electrical shock is delivered to your chest wall that synchronizes the heart and allows the normal rhythm to restart.
• Catheter ablation -- during ablation, energy is delivered through a catheter to tiny areas of the heart muscle. This energy can either "disconnect" the pathway of the abnormal rhythm; block the abnormal pulses and promote normal conduction of impulses; or disconnect the electrical pathway between the atria and the ventricles.
• Pulmonary vein antrum isolation (PVI): during PVI, special catheters are inserted into the heart (catheters are inserted into the right atrium and into the left atrium). Intracardiac echocardiography is used to visualize the left atrium during the procedure. One catheter in the left atrium is used to map or locate the abnormal impulses coming from the pulmonary veins. The other catheter is used to deliver the radiofrequency energy to ablate, or create lesions outside the pulmonary veins. The procedure is repeated for all four pulmonary veins. The lesions form a circumferential scar around the pulmonary veins. The scar blocks any impulses firing from within the pulmonary veins, thereby "disconnecting" the pathway of the abnormal rhythm and potentially curing atrial fibrillation.

Electrical devices – a small device may be implanted under the skin that can detect an irregular heart rhythm and/or treat it. Your doctor will discuss the benefits and risks of implantable devices and whether they are an appropriate treatment for your condition.

• Permanent pacemaker -- a device that sends small electrical impulses to the heart muscle to maintain a normal heart rate. The pacemaker has a pulse generator (which houses a battery and a tiny computer) and leads (wires) that send impulses from the pulse generator to the heart muscle, as well as sense the heart's electrical activity. Pacemakers are mostly used to prevent the heart from beating too slowly. Newer pacemakers have many sophisticated features that are designed to help with the management of arrhythmias, optimize heart-rate-related functions and improve synchronization.
• Implantable cardioverter-defibrillator (ICD) -- a sophisticated electronic device used primarily to treat ventricular tachycardia and ventricular fibrillation, two life-threatening abnormal heart rhythms. The ICD constantly monitors the heart rhythm. When it detects a very fast, abnormal heart rhythm, it delivers energy to the heart muscle to cause the heart to beat in a normal rhythm again.

Heart surgery -- The Maze, modified Maze and minimally invasive ablation surgeries are used to correct atrial fibrillation that is not controlled with medications or non-surgical treatment methods. Arrhythmia surgery also may be recommended if you need surgery to correct other forms of heart disease (such as valve disease or coronary artery disease).

Treatment also includes regular follow-up with a physician. While women have specific concerns related to irregular heart rhythms, communication with your physician will ensure safe and effective treatment.

Arrhythmias and pregnancy
Premature atrial beats occur in about 50 percent of women during pregnancy, although most are harmless and do not last¹. While sustained arrhythmia is somewhat rare, for those who have supraventricular tachycardia or paroxysmal SVT, the symptoms are worsened in 20 percent of cases¹. Symptoms of SVT may include shortness of breath, palpitations, and dizziness². Arrhythmias may occur more frequently during pregnancy due to changes in hormones, changes in associated hemodynamic, hormonal and autonomic changes and changes in circulating blood volume, sleep and emotion during pregnancy.

Women who have had congenital heart defects repaired have an increased risk of arrhythmias during pregnancy. In 27 women who had repaired congenital heart defects and 29 pregnancies, SVT occurred in 15, ventricular tachycardia in nine, high grade heart block in four and sick sinus syndrome in three women³.

Arrhythmias in pregnancy are treated conservatively. After determining the type of arrhythmia, the physician will evaluate for underlying causes. If symptoms are minimal, rest and vagal maneuvers may be used to help slow the heart rate. Vagal maneuvers include carotid massage, applying ice to the face, and the Valvsalva maneuver, which is the most successful in stopping tachycardias⁴. The Valsalva maneuver involves a person exhaling forcibly with a closed glottis (the windpipe) so that no air exits through the mouth or nose as, for example, in strenuous coughing, straining during a bowel movement or lifting a heavy weight.

When the arrhythmia causes symptoms or a drop in blood pressure, antiarrhythmic medications may be used. No anti-arrhythmic medication is completely safe during pregnancy; therefore medications are avoided during the first trimester if possible to limit risk to the fetus. Drugs with the longest safety record should be tried first. Propranolol, metopropolol, digioxin, adenosine and quinidine have been well tested and shown to be well tolerated and safe during the second and third trimester⁵.

Cardioversion is safe during all trimesters of pregnancy and can be used if necessary¹. In addition, women who have an ICD who become pregnant do not have an increased risk for ICD discharges or ICD complications. A woman who has an ICD can safely become pregnant, unless she has an underlying heart condition that would increase health risks during pregnancy⁶.