SVT (Supraventricular Tachycardia) vs. Heart Attack

Supraventricular tachycardia (SVT) is a rapid heart rate (100 beats or more per minute, but usually faster; like 140-250 beats per minute) due to electrical impulses that originate in the upper ventricles of the heart. In contrast, a heart attack is a severe reduction or complete blockage of blood to one or more segments of the coronary arteries that can cause death of heart muscle.

• SVTs are considered a general term for tachycardias that originate above the atrioventricular node (AV node), while other physicians prefer to simply name each type of tachycardia and consider any SVT that occurs off and on as either a SVT or a paroxysmal SVT (PSVT). These two terms are used interchangeably; however, heart attacks are considered to be the same entity by most physicians although they may be termed as an infarction or myocardial infarction.
• A heart attack is a medical emergency and intervention can be lifesaving. In contrast, most SVTs are paroxysmal and may come and go quickly in a few minutes without intervention; however, others may linger one or more days and require examination and/or intervention by medical personnel to reduce symptoms.
• Symptoms of SVTs and heart attacks that are similar include:
  • dizziness
  • lightheadedness and/or fainting
  • shortness of breath
  • anxiety
  • chest pain and/or chest tightness
• Some patients with heart attacks may have tachycardia; SVT patients may have intermittent bouts with tachycardia.
• Heart attacks may have additional symptoms such as sweating, nausea and/or vomiting, jaw pain, pain in the shoulders, back and/or arms, extreme weakness, and/or fatigue.
• The causes of SVTs are different from those of a heart attack. SVTs are caused by various electrical problems (conduction of electrical impulses through the atria above the AV node) while many heart attacks are caused by blockage in segments of the coronary arteries. However, heart attacks can occur due to electrical problems below the AV node (in the ventricles) with situations like ventricular fibrillation occur (ventricles twitch and do not produce contractions to move blood through the body).
• Both SVTs and heart attacks require EKGs to help diagnose each condition as each has characteristic EKG patterns.
• Treatment for SVTs depends on decreasing the heart rate, usually with medications and/or interrupting the electrical circuits causing SVT by surgical means (usually elective surgery that ablates [cuts off] the aberrant electrical pathway). In contrast, immediate intervention is needed with heart attacks to either open up a clogged coronary artery by chemical (clot - busting drugs) or surgical (angioplasty, for example) methods.
• Occasionally, SVT may require electroshock to the heart (electrical cardioversion) if SVT symptoms are severe and the patient does not respond to other methods like vagal nerve stimulation. Similarly, a heart attack caused by ventricular fibrillation may also require electrocardioversion.
• The prognosis for individuals with SVT is usually good to excellent; those that need medication or other interventions still have a good to fair outcome; patients with heart attacks can have good to poor outcomes depending upon the extent of muscle damage in the heart and how well they manage to reduce risk factors such as smoking, weight loss, blood pressure control and other follow-up recommendations.
• Prevention of SVT and heart attacks share similar methodologies such as avoiding stimulants or stressors like nicotine in cigarettes, use of illegal drugs especially stimulants like methamphetamines and cocaine and the use of alcohol.

Supraventricular tachycardia is a rapid heart rate (tachycardia, or a heart rate above 100 beats per minute) that is caused by electrical impulses that originate above the heart's ventricles. Many doctors and other health care professional include all of the many tachycardias that involve the atrioventricular node (AV node) under this classification, but others do not.

Supraventricular tachycardia does not include those tachycardia rhythms that originate from the ventricles (ventricular tachycardias) such as ventricular tachycardia or ventricular fibrillation.

Supraventricular tachycardia is also called paroxysmal supraventricular tachycardia and abbreviated either SVT or PSVT.
How does the heart's normal electrical activity work?

• The heart consists of four chambers; two upper chambers called atria and two lower chambers called ventricles.
• The atria receive blood from blood vessels and, with coordinated electrical impulses from the sinoatrial (SA) node, contract to push blood into the ventricles.
• The ventricles then contract to push the blood out of the heart into the blood vessels of the lungs and to the rest of the body.
• The heart usually beats 60-90 times a minute. A heart rate faster than 100 beats per minute is considered tachycardia.
• Specialized heart cells coordinate the contractions by means of electrical signals.
• These specialized cells consist of the SA or sinus node in the right atrium, the AV node and the bundle of His (atrioventricular bundle) in the wall between the right and left ventricles.
• The SA node, the natural pacemaker of the heart, starts the electrical signals and transmits them to the AV node.
• The AV node then activates the bundle of His and its branches, resulting in contraction of the ventricles.
• The atria contract to fill the ventricles with blood; then the ventricles contract in quick sequence to move the blood into the lungs and the rest of the body. Each sequence of atrial then ventricular contraction is one normal heartbeat.
• SA node and AV node and the path of the electrical impulse into the ventricles through the bundle and to the right and left ventricle nerve bundles (RB and LB) to complete a heartbeat.
• Nerve impulses, oxygen demand, the level of hormones in the blood, and other factors influence the rate of heart contraction at any given time. A problem in any of these areas can cause abnormal heart rhythm (arrhythmia or dysrhythmia).

If you believe that you are having the symptoms of a heart attack, please call 911 immediately and seek medical attention.

The heart is a muscle like any other in the body. Arteries supply it with oxygen-rich blood so that it can contract and push blood to the rest of the body. When there isn't enough oxygen flow to a muscle, its function begins to suffer. Block the oxygen supply completely, and the muscle starts to die.

• The heart muscle gets its blood supply from arteries that originate in the aorta just as it leaves the heart.
• The coronary arteries run along the surface of the heart and supply oxygen-rich blood to the heart muscle.
• The right coronary artery supplies the right ventricle of the heart and the inferior (lower) portion of the left ventricle.
• The left anterior descending coronary artery supplies the majority of the left ventricle, while the circumflex artery supplies the back of the left ventricle.
• The ventricles are the lower chambers of the heart; the right ventricle pumps blood to the lungs and left pumps it to the rest of the body.

Supraventricular Tachycardia Symptoms

PSVT can cause a number of symptoms, depending on a person's overall health and how fast their heart is beating. People with heart damage or other coexisting medical problems experience a greater degree of discomfort and complications than those who are healthy. Some people have no symptoms at all.

Symptoms can come on suddenly and may go away by themselves; they can last a few minutes or as long as 1-2 days. The rapid beating of the heart during PSVT can make the heart a less effective pump so that the body organs do not receive enough blood to work normally. The following symptoms are typical with a rapid pulse of 140-250 beats per minute:

• Palpitations (the sensation of the heart pounding in the chest)
• Dizziness, light-headedness (near-faint), or fainting
• Shortness of breath
• Anxiety
• Chest pain or tightness

Heart Attack Symptoms

Classic symptoms of a heart attack may include:

• chest pain associated with shortness of breath,
• profuse sweating, and
• nausea.

The chest pain may be described as tightness, fullness, a pressure, or an ache.

Unfortunately, many people do not have these classic signs. Other signs and symptoms of heart attack may include:

• indigestion,
• jaw ache,
• pain only in the shoulders or arms,
• shortness of breath, or
• nausea and vomiting.

This list is not complete, since many times people can experience a heart attack with minimal symptoms. In women and the elderly, heart attack symptoms can be atypical and sometimes so vague they are easily missed. The only complaint may be extreme weakness or fatigue.

Pain may also radiate from the chest to the neck, jaw, shoulder, or back and be associated with shortness of breath, nausea, and sweating.

Supraventricular Tachycardia Causes

The following is a list of conditions that fit under the broad definition of SVT:

• Sinus tachycardia
• Inappropriate sinus tachycardia (IST)
• Sinus nodal reentrant tachycardia (SNRT)
• Atrial tachycardia
• Multifocal atrial tachycardia (MAT)
• Atrial flutter (AF)
• Atrial fibrillation (A fib)
• Paroxysmal supraventricular tachycardia (PSVT; also termed AV nodal reentrant tachycardia or AVNRT and AV reentrant tachycardia or AVRT, a subset of PSVT)
• Junctional ectopic tachycardia (JET)
• Nonparoxysmal junctional tachycardia (NPJT)

There are two semantic problems in the literature with supraventricular tachycardias (SVTs). From the strict but extremely broad definition, an SVT can be due to any supraventricular cause. Consequently, atrial fibrillation, atrial flutter, paroxysmal supraventricular tachycardia, and even normal exercise-induced tachycardia could fall under this designation. However, many clinicians consider SVT to be only paroxysmal supraventricular tachycardia (PSVT). The terminology may be somewhat confusing, but the large majority of SVTs are usually discussed separately in articles under their specific name (for example, atrial fibrillation). Because the principal SVTs listed above have separate articles devoted to them in eMedicineHealth, this article will be devoted only to paroxysmal supraventricular tachycardia (PSVT).

Heart Attack Causes

Over time, plaque can build up along the course of an artery and narrow the channel through which blood flows. Plaque is made up of cholesterol buildup and eventually may calcify or harden, with calcium deposits. If the artery becomes too narrow, it cannot supply enough blood to the heart muscle when it becomes stressed. Just like arm muscles that begin to ache or hurt when heavy things are lifted, or legs that ache when you run too fast; the heart muscle will ache if it doesn't get adequate blood supply. This ache or pain is called angina. It is important to know that angina can manifest in many different ways and does not always need to be experienced as chest pain.

If the plaque ruptures, a small blood clot can form within the blood vessel, acting like a dam and acutely blocking the blood flow beyond the clot. When that part of the heart loses its blood supply completely, the muscle dies. This is called a heart attack, or an MI—a myocardial infarction (myo=muscle +cardial=heart; infarction=death due to lack of oxygen).

What Is the Treatment for Supraventricular Tachycardia?

Treatment for PSVT focuses on decreasing the heart rate and breaking up the electrical circuits made by the abnormal conducting pathways. Treatment can be divided into two broad categories: halting the acute episode and preventing any new episodes. One of the most important considerations in treating an acute episode of PSVT is how severely the heart function has been affected.

The doctor may monitor the patient's progress, depending on the severity of the symptoms or the cause and treatment used for the PSVT. The doctor may choose to monitor the patient for a few weeks or months for the following reasons:

• To assess the frequency of the recurrence of arrhythmias and heart rate
• To adjust or change medications based on clinical, repeat ECG, or Holter evaluations
• To plan further therapy if the PSVT condition worsens

What Is the Treatment for Heart Attack?

If the EKG shows that there is an acute heart attack (myocardial infarction), the goal is to open the blocked artery as soon as possible and restore blood supply to the heart muscle.

When a heart attack strikes, the key thing to remember is that time equals muscle. The longer the delay in seeking medical care, the more heart muscle will be damaged. There is a window of opportunity to restore blood supply to the heart muscle by unblocking the affected heart artery. Treatments must be done in a hospital and include administration of clot-busting drugs to dissolve the clot at the site of the ruptured plaque and heart catheterization and angioplasty (in which the blood vessel is opened by balloon, often with adjunctive placement of a stent), or both.

Not all hospitals have the equipment or cardiologists available to perform emergency heart catheterizations, and thrombolytic therapy (the use of clot-busting drugs) may be the first step to open the blood vessel and return blood supply to the heart muscle.

Heart Attack Self-Care at Home

• The first step to take when chest pain occurs is to call 911 and activate the Emergency Medical System. First responders, EMTs, and paramedics can begin treating a heart attack en-route to the hospital, alert the Emergency Department that the patient is on the way, and treat some of the complications of a heart attack should they occur.
• Step two is to take an aspirin. Aspirin makes platelets less sticky and can minimize blood clot formation and prevent further blockage of the artery.
• Step three is to rest. When the body does work, the heart has to pump blood to supply oxygen to the muscles and clear the waste products of metabolism. When heart function is limited because it doesn't have an adequate blood supply itself, asking it to do more work may cause more damage and risk further complications.

Heart Attack Emergency Medical Treatment

Hospitals have established treatment plans to minimize the time to diagnose and treat people with heart attack. National guidelines suggest that an electrocardiogram (EKG) be done within 10 minutes of the patient's arrival in the ER.

Many things will occur at the same time as the EKG being completed. The doctor will take a history and complete a physical exam while the nurses start an intravenous line (IV), place heart monitor lines on the chest, and administer oxygen.

Medications are used to try to restore blood supply to the heart muscle. If it wasn't taken prior to arrival in the ER, aspirin will be used for its anti-platelet action.

Nitroglycerin will be used to dilate blood vessels. Heparin or enoxaparin (Lovenox) will be used to thin the blood. Morphine can also be used for pain control. Antiplatelet medications such as clopidogrel (Plavix) or prasugrel (Effient) are also recommended.

There are two options (depending on the resources at the hospital) 1) if the EKG shows an acute heart attack (myocardial infarction), and 2) if there are no contraindications.

Heart Catheterization

The favored treatment is heart catheterization. Tubes are threaded through the femoral artery in the groin or through the brachial artery in the elbow, into the coronary arteries, and the area of blockage is identified.

Angioplasty

Angioplasty (angio= artery + plasty=repair) is then considered if possible. A balloon is placed at the blockage site and as it opens, it compresses the plaque into the blood vessel wall. Afterwards, a stent or a mesh cage is placed across the angioplasty site to keep it from closing down. Guidelines recommend that from the time the patient arrives at the hospital to having the blood vessel open be less than 90 minutes.Not all hospitals have the capabilities of doing heart catheterizations 24 hours a day, and may transfer the patient with an acute heart attack to a hospital that has the technology available. If the transfer time will delay angioplasty treatment beyond the 90 minute window recommendation, clot-busting drugs may be considered to dissolve the blood clot that has obstructed the coronary artery. Tissue plasminogen activator (TPA or TNK) can be used intravenously. After TPA infusion, the patient may still be transferred for heart catheterization and further care.

If the EKG is normal but the history is suggestive of an heart attack or angina, the evaluation will continue with the blood tests described above. However, the patient will likely be treated as if the heart attack was occurring. Patient treatment would include aspirin, oxygen, nitroglycerin, and blood thinning medications until the presence of heart damage is has been ruled out. In other words, the treatment presumes heart disease until proven otherwise.

Heart Attack Complications

When a heart attack occurs, part of the heart muscle dies and is ultimately replaced with scar tissue. This leaves the heart weaker and less able to meet the needs of the body. This will lead to exercise intolerance including early fatigue or shortness of breath on exertion. The amount of disability is dependent on the amount of heart muscle pumping function lost.

Muscle that loses its blood supply becomes electrically irritable. This may cause a short circuit of the electrical conduction system of the heart. This may cause ventricular fibrillation, a situation in which the ventricles do not beat in a coordinated function. Instead, they jiggle like a bowl of Jello and cannot pump blood to the body. Sudden death occurs. Patients are kept in the ER or admitted to the hospital while assessing chest pain to monitor their heart rhythm and hopefully prevent sudden death from acute heart attack or unstable angina which may result in ventricular fibrillation.

If this rhythm occurs while monitored in the hospital, it can be rapidly treated with defibrillation, an electric shock to try to restore a normal electric rhythm and heart beat.

What Is the Outlook for Someone with Supraventricular Tachycardia?

Most people with rare episodes of paroxysmal supraventricular tachycardia (PSVT) live healthy lives without restrictions, so their outlook is excellent. Those people that require medication, cardioversion, or other interventions usually have a good to fair outcome.

• If medications are prescribed, the patient may or may not experience some side effects. Potential side effects should be discussed with the doctor.
• In rare cases, if a patient has a continuous fast heart rate like PSVT that goes untreated, the heart muscle can weaken and lead to heart failure.
• If the doctor finds a specific cause related to an underlying heart or systematic condition, recovery from PSVT may depend on the prognosis for that underlying condition.

What Is the Follow-up for Heart Attack?

Medications that may be recommended on discharge from the hospital include:

• aspirin for its anti-platelet effect,
• a beta blocker to blunt the effect of adrenaline on the heart and make it beat more efficiently,
• a statin drug to control cholesterol and
• clopidogrel (Plavix) or prasugrel (Effient), other anti-platelet drugs.

Since the heart may have been damaged, further testing may be needed to assess its pumping capabilities. Echocardiography can measure ejection fraction, the amount of blood that heart pumps out to the body compared to how much it receives. A normal ejection fraction should be greater than 50% to 60%. A monitored exercise program may be arranged.

Attempts will be made to minimize cardiac risk factors, including:

• smoking cessation,
• weight loss,
• control blood pressure, and
• lower "bad" cholesterol.

Some patients will require coronary artery bypass surgery if their angiogram shows multiple areas of blockage.

What Are Special Situations?

Prinzmetal Angina

In some people, the coronary arteries can go into spasm and cause decreased blood flow to heart muscle. This can lead to chest pain known as Prinzmetal angina, even if there is no buildup of plaque in the blood vessels. In severe episodes the EKG can suggest a heart attack, and muscle damage can be confirmed by measuring cardiac enzymes.

Cocaine

There is a strong correlation between cocaine usage and heart attack. Aside from the artery spasm that cocaine induces, the drug turns on the adrenaline system of the body, increasing pulse rate and blood pressure, requiring the heart to do more work.

How to Prevent a Heart Attack

While people cannot control their family history and genetics, they can minimize risk factors for heart disease by:

• quitting smoking;
• controlling high blood pressure, cholesterol, diabetes;
• exercise regularly, and
• take a baby aspirin a day.

These are all lifelong challenges to prevent heart disease, stroke, and peripheral vascular disease.

Even with the best of preventive care, heart attacks happen. Develop an emergency plan so that if chest pain occurs make certain you, your family, and friends know how to activate the Emergency Medical Services in your area or call 911.