A Review on Supra Ventricular Tachycardia. An ECG Explanation on Irregular Heart Beats

Script 2018 30 Pages

Medicine - General




Introduction of SVT:


Signs and Symptoms:
SVT Symptoms and Signs in Infants and Children:

Risk Factors:

Prevention of SVT:


Life Style Modifications:

Types of SVT’s:

Atrial Fibrillation:

Atrial Flutter:

Paroxysmal Supra Ventricular Tachycardia:

Wolf Parkinson White Syndrome:

Atrio Ventricular Re-Entrant Tachycardia:


Introduction of SVT:

Supra Ventricular Tachycardia refers to rapid rhythm of heart for a reason other than exerscise, high fever and stress. This kind of faster heart beats originates and is sustained in atrial or atrioventricular nodal tissue, and then transmits improper electrical activity from upper part of the heart through the bundle of His and cause rapid ventricular response. They may start either from the atria and atrioventricular node.

The heart beats in a normal healthy individual will be atleast a 100 beats per minute but in SVT there may be a heart beat reaches upto 300 beats per minute. Generally many persons with these tachyarrhythmias have structurally normal hearts [1]. SVT may start and stop quickly, and you may not have symptoms. SVT becomes very complicate when it happens often and lasts for a long time or causes its symptoms.


The overall prevalence of SVT is two or three per 1,000 persons in the general pop- ulation. The mean age of occurrence is 45 years and 62% of cases occur in women [2]. SVT occurs in one per 250 to 1,000 infants and children, with Atrio Ventricular Re-entrant Tachycardia (AVRT) accounting for most cases [3].

The incidence of Atrio Ventricular Nodal Re-entrant Tachycardia (AVNRT) in women is twice than in men [4]. It is correlated with lower estrogen levels and higher progesterone levels, and is therefore more common during the luteal phase of the menstrual cycle and less common during pregnancy [5].

Atrial Fibrillation (AF) and Atrial flutter (AFL) are the most common subtypes of SVT, affecting approximately 2 million patients in the United States. Of the remaining subtypes of SVT, Atrioventricular Nodal Reentrant Tachycardia (AVNRT) is the most common, accounting for approximately 60% of cases [6].

The subtypes of Atrioventricular Reentrant Tachycardia (AVRT) and atrial tachycardia account for approximately 30% and 10% of SVT cases, respectively [6].

The incidence of Paroxysmal Supra Ventricular Tachycardia is approximately 1-3 cases per 1000 persons, with a prevalence of 0.2%. Atrial fibrillation is affecting 3 million people in the United States alone, with prevalence of 0.4-1% in the population. It is estimated that atrial fibrillation will affect more than 7.5 million people by 2050 [7].


SVT and PSVT generally start from either the atria or atrioventricular node. They are triggered due to one of two different mechanisms: one it is reentry or increased automaticity. This may be induced by premature atrial and other type of fast heart rhythm is ventricular arrhythmias- rapid rythms that start within the ventricle.

Some other triggers include hyperthyroidism and stimulants, including caffeine, drugs use such as cocaine and methamphetamines, surgery, pregnancy, which causes SVT [8].

Paroxysmal SVT is observed not only in healthy individuals. It is also common in patients with previous myocardial infarction, mitral valve prolapse, rheumatic Heart Disease, pericarditis, pneumonia, chronic lung disease, and current alcohol intoxication [8]. Digoxin toxicity also may be associated with paroxysmal SVT [9]. Some other health conditions like Wollf-Parkinson-White syndrome also causes the SVT. However majority of cases has no identifiable triggering factors for SVT.

Signs and Symptoms:

PSVT can cause a number of symptoms, depending on a person's overall health and how fast their heart is beating. Compare to healthy persons, patients with heart problems or any other comorbities experience a higher degree of upset or abash and complications. Some individuals may have no symptoms [10].

Symptoms can come on suddenly and may go away by themselves; they can last for a few minutes or as long as 1-2 days. During Paroxysmal SVT, the faster beat of the heart can make the heart less effective pumping, so that the body tissues may not receive sufficient blood to work normally [10].

Palpitations (the sensation of the heart pounding in the chest) Dizziness, light- headedness, fainting, Shortness of breath, Anxiety, chest pain or tightness are the symptoms experienced when the pulse rate is between 140 and 250 beats per minute [10].

SVT Symptoms and Signs in Infants and Children:

In infants and very young children, symptoms are sometimes difficult to identify. Whatever Paroxysmal SVT may have in the infants those with poor feeding, irritability, perspiration, light color of skin, and who reaches a pulse rate of 200-250 beats per minute [11].

To diagnose supraventricular tachycardia, physician reviews the symptoms, medical history and conduct a physical examination. Electrical activity of heart can be detected with the procedures of Electrocardiogram (ECG), sensors (electrodes) which are attached to the chest and sometimes to limbs. An ECG measures the timing and duration of each electrical phase in the heartbeat. Holter monitor is a portable ECG device; this can be worn for a day or more to record the hearts activity.


Event monitor is also a portable ECG device; this is used for the sporadic episodes of SVT [12]. In Echocardiogram, a transducer is placed on the chest; this uses sound waves to produce images of heart’s structure, size and motion. Implantable loop recorder detects abnormal heart rhythms and is implanted under the skin in the chest area [12].


The treatment goal is to slow down the rate and convert to sinus rhythm by increasing the refractoriness of the AV node or blocking of the AV node. This is accomplished with vagal maneuvers, medications, or cardioversion [13].

The patients with frequent episodes, some studies suggest nondiydropyridine calcium channel blockers or beta blockers. This can correct the conduction across the AV node and decrease the number and duration of episodes. The class I C antiarrhythmics flecainide and propafenone depress conduction across an accessory pathway and suppress episodes in most patients. In patient with atrial tachycardia these medications can be suggested.

The class I A medications quinidine, procainamide, and disopyramide are less commonly used because of their modest effectiveness, and adverse and proarrhythmic effects. The drugs like amiodarone, dofetilide and sotalol which belongs to class III medications are effective in management. These medications can have adverse events, so they should be taken with the reference from cardiologist [14].

Carotid sinus massage may show a gentle pressure on the neck, in which the carotid artery divides into two branches to release some chemicals that can slow the rate of heart.

Vagal maneuvers may be able to stop an episode of SVT by using particular maneuvers that include holding breath and straining, dunking face in ice water, or coughing. This procedure of management shows its affect on the nervous system that controls heartbeat, and it often leads to become slow heart rate of the patient [15].

Cardioversion is the process of delivering shock to the heart by placing patches or paddles on the chest. This current affects the electrical impulses in your heart and can restore a normal heart rhythm.

Catheter ablation is the process of threading one or more catheters through blood vessels to the heart. Catheter tips of the electrodes uses heat or radiofrequency energy or extreme heat to destroy a part of heart tissue and generates an electrical block along the pathway which causes arrhythmia [16].

Risk Factors:

SVT is a common type of arrhythmia in infants and children. Although it occurs in either sex, it tends to occur more often in women, especially in pregnant women.

There are some risk factors which may increase the risk of SVT

- Age: In middle aged or older some types of supraventricular are more common.
- Congenital heart disease: Born with an abnormal heart during birth may affect your hearts rhythm.
- Coronary artery disease: Other heart problems and previous heart surgery: Narrowed coronary arteries, a heart attack, abnormal heart valves, History of heart surgery, congestive heart failure, cardiomyopathy and other damages of heart increase the risk of occuring SVT.
- Thyroid problems: Patient with an overactive or underactive thyroid gland can develop the risk of SVT.
- Drugs and supplements: Over-the-counter drugs related to cough and cold and some other prescription drugs may lead to an episode of SVT.
- Nicotine and illegal drug use: Nicotine and illegal drugs, such as cocaine and ampetamines, may have great intense to affect the heart and trigger an episode of SVT.
- Physical fatigue
- Anxiety or emotional stress
- Diabetes: Risk of developing coronary artery disease and hypertension greatly elevates with uncontrolled diabetes.
- Obstructive sleep apnea: Breathing interrupttion during sleep, can increase your risk of developing SVT.

Prevention of SVT:

An episode of SVT can prevent by knowing the triggering factor and the episodes to occur SVT triggering factor should avoid. Keep noting the causative things to identify triggering factor and track the rate of heart, activity and symptoms during the time of SVT episodes [17]. Following are the things to follow to avoid from SVT.

- Increase the physical activity
- Have an heart-healthy diet
- Avoid smoking
- Maintain a healthy weight
- Limit or avoid alcohol
- Reduce stress
- Get the plenty of rest
- OTC medications usage should be with caution, as some drugs contain stimulants that may trigger a faster heartbeat
- Avoid stimulant drugs like as cocaine and methamphetamines

For most people with SVT, moderate amounts of caffeine do not affect an episode. Large amounts of caffeine should avoid.


Over time, untreated and frequent episodes of supraventricular tachycardia may depress the heart and lead to heart failure, particularly if the patients have other comorbidities. In extreme cases, an episode of SVT may cause unconsciousness or cardiac arrest.

Life Style Modifications:

Life style modifications like eating healty foods (low in salt, solid fats and rich in fruits, vegetables and whole grains), increasing physical activity, reducing and eventuelly avoiding alcohol intake, quitting smoking, maintaining Ideal Body Weight (IBW), mainitaing normal levels of cholesterol and Blood Pressure (BP), following prescription orders etc helps in improving your health condition [18].

Figure No-01: Life Style Modifications of SVT (Avoid Smoking and Alcoholism)

Abbildung in dieser Leseprobe nicht enthalten

[Image adapted from http://ddinews.gov.in/health/heavy-drinking-and-smoking-can-age-you-faster-study]

Types of SVT’s:

- Atrial Fibrillation (AF)
- Atrial Flutter (AFL)
- Paroxysmal Supraventricular Tachycardia (PSVT)
- Atrio Ventricular Nodal Re-entrant Tachycardia (AVNRT)
- Atrio Ventricular Re-entrant Tachycardia (AVRT)
- Wolff–Parkinson–White syndrome (WPW)

Atrial Fibrillation:

Atrial fibrillation can be described as an extreme faster (400 to 600 atrial beats/min) and abnormal activation of atria. There is an absence or loss of atrial contraction, and supraventricular impulses generates the atrioventricualr(AV) conduction system in variable degrees, resulting in irregular ventricular activation and irregularly irregular pulse (120 to 180 beats/ min) [19].

Atrial fibrillation is a frequent and unexpected cardiac arrhythmia [20]. Atrial fibrillation is an age dependent affecting 4% older than 60 years and 8% older than 80 years. Almost 25% of the SVT patients aged 40 years and older will develop AF [21]. The prevalence of Atrial Fibrillation is 0.1% in younger than 55 years and 3.8% in 60 years or above and 10% in 80 years or older [22]. Atrial fibrillation incidence significance is higher in men than women [23]. Atrial fibrillation is common in white race than in black race. However atrial fibrillation is often associated with other cardiovascular diseases, only 10-15% cases of atrial fibrillation occur in the absence of comorbidities. The risk of stroke from atrial fibrillation is estimated to be 1.5% for the age group of 50-59 years and it approaches 30% for the age group of 80-90 years [24].

Atrial fibrillation can cause auricular fibrillation by forming blood clots that can traverse to brain from the heart, resulting in stroke. Often it start as short period of abnormal beatings which become longer and stays constant for over time [25]. Often episodes may not have symptoms [26].

Sometimes atrial fibrillation may be with an occurance of palpitations, faint, lightheadedness, breatlessness, or chest pain [27]. The disease has an increased risk of heart failure, dementia and stroke [26]. A history of stroke as well as high blood pressure, diabetes, heart failure, or rheumatic fever may indicate whether someone with AF is at a higher risk of complications [28].

In Atrial Fibrillation, the SA node generates a normal regular electrical impulses generated in the right atrium of the heart and it is excited by disorganized electrical impulses usually originates in the pulmonary veins root. This causes irregular conduction of ventricular impulses which createss the heartbeat [29].

The P wave activity can be observed as “coarse fibrillatory” and it is termed as “coarse atrial fibrillation” although there is no clinical significance.

The atrioventricular node intermittently becomes refractory and allows only a certain atrial action potentials to reach the ventricles. This is the cause where the ventricular rate is not also in between 400 to 600 bpm, but rather around 100 to 200 bpm. The degree of action potential which crosses the AV node to the ventricles is variable and AV blocking medications can decrease the action potential.

As due to AV node is intermittently (not regularly) refractory, when an action potential does reach the ventricles the QRS complexes are produced and will occur an “irregularly irregular” manner as there is no pattern to their frequency. This is usually manifests as varying RR intervals.

Diagnostic investigation of AF requires a complete history and physical examination, transthoracic echocardiogram, ECG, CBC, and serum TSH level [29].

Figure No-02: ECG of Atrial Fibrillation

Abbildung in dieser Leseprobe nicht enthalten

[Image adapted from https://www.quora.com/in/How-do-you-detect-atrial-fibrillation]

In an ECG graph from the Figure no-1 Atrial Fibrillation is understood with Leads V4 and V5. It shows irregular intervals between heartbeats. There are two rhythms that are irregularly irregular are atrial flutter with variable conduction and multifocal atrial tachycardia. Atrial flutter has the typical “sawtooth pattern” whereas multifocal atria tachycardia requires three distinct P wave morphologies in one 12 lead ECG tracing. There are quite few arrhythmias they are regularly irregular, such as 2nd-degree AV block type I (Wenkebach). This indicates atrial fibrillation will be with no P wave and an irregularly irregular QRS complex.



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Supraventricular tachycardia Atrial Flutter Paroxysmal AVNRT AVRT Wolff Parkinson Syndrome Atrial Fibrillation Risk factors Prevention



Title: A Review on Supra Ventricular Tachycardia. An ECG Explanation on Irregular Heart Beats