The conduction system of heart is the electrical conduction system that controls or regulates the heart rate. It generates the electrical signals and passes them to every muscle of the heart, stimulating contraction of the heart and pump the blood throughout the body (Chen, 2016). The elements of the conduction system include sinus node, autonomic nervous system, and the atrioventricular node. Supraventricular tachycardia (SVT) is the tachycardia where the heart beats are become faster suddenly due to the improper activity of electrical system that controls the heart rhythm (NHS, 2018). It is also called paroxysmal supraventricular tachycardia (Sics editore, 2014). The estimated incidents of SVT are 35 people per 10000 persons each year with the prevalence of 2.29 per thousand persons (Sohinki, & Obel, 2014). Most common types of SVT are: Atrioventricular Reciprocating Tachycardia (AVRT), Atrioventricular Nodal Re-entrant Tachycardia (AVNRT), and Atrial Tachycardia (AT). The differential diagnosis of different types of supraventricular tachycardia will be discussed in this report.
Some of the hemodynamic measurements used in the diagnosis of SVT are stroke volume (SV) with the normal range of 40 to 80 ml, and cardiac index (CI). Other measurement like Pulmonary Vascular Resistance (PVR), and systemic vascular resistance (SVR) are also included in this list. A 12-lead electrocardiogram should be used in the patients, who are stable hemodynamically, with the special attention to the rhythm and rate, AV conduction (PR intervals), RP intervals, pathologic Q waves, hypertrophy, prolongations of QT intervals, any signs of pre-excitation. Most of the supraventricular tachycardia has narrow QRS complexes. The wide complexes may also occur (Bibas, Levi, & Essebag, 2016). The patient with the history of coronary artery disease or the myocardial infarction, the wide complex tachycardia should be considered to be of ventricular origin. And the patient should be referred to the cardiologist or electrophysiologist if pre-excitation is there on resting 12 lead electrocardiograms.
To diagnose the cardiac diseases various methods can be used such as diagnostic imaging, stress electrocardiogram testing, ambulatory monitoring, electrophysiological testing and the cardiac angiography. The cardiac imaging important to monitor patients with the known pathology in different cardiovascular diseases, for example, X-ray is used in the preliminary assessment of cardiovascular diseases and helps to exclude pathology such as infection, fibrosis or malignancy (Jang, 2017). The coronary angiography is helpful to directly visualize the coronary arteries for both obstructive and non-obstructive coronary artery disease. However, it is not able to tell about whether a coronary stenosis is hemodynamically significant or not. Stress echocardiography provides an effective and non-invasive assessment of the person with chest pain. It avoids radiation exposure and has a great specificity. It is less costly than other imaging methods such as stress perfusion. Stress ECG is a safe, cost-effective and accessible test. However, it has less sensitivity and specificity for the coronary artery disease. Therefore it has a limited role in chest pain assessment (Stokes, & Roberts-Thomson, 2017).
The Atrioventricular nodal re-entry tachycardia (ANVRT) is considered the most common type of SVT. Majority of the patients with AVNRT do not have the structural heart disease; the most affected group is youth, healthy females. This focal tachycardia originated in the atria. The ECG findings may display evidence of pre-excitation. In orthodromic tachycardia, after the QRS complex, the P wave falls typically while in AVNRT, after QRS complex p waves appear immediately. The AVRT is likely to occur at the young age and more frequently in men than AVNRT. The sensation of neck pulsation is another distinguishing factor in AVNRT which is more common in AVRT due to their simultaneous ventricular and atrial contraction and activation. The flutter waves are present in the case of AVNRT. There may be a variation in ventricular rate but without the treatment, it is nearly 150 bpm with a ratio of 2; 1 AV block (Lelakowski, Rydlewska, & Kuniewicz, 2010).
AVRT or Atrio-Ventricular Reciprocating Tachycardia is the 2nd most common type of SVT. Patient with AVRT typically presents at the early age than the patient with AVNRT. This type of SVT is caused by bypass tracts that serve as the aberrant conduits for the impulses that pass from the Sino-atrial node and travels through to the tracts establishing the re-entry circuit. The main ECG findings include delta wave, which is not always apparent due to the concealed accessory pathway. The ventricular rate is between 124 to 256 bpm. The regular rhythm is narrow in QRS complex and wide QRS complex are uncommon in AVRT if the aberrancy is present. In orthodromic AVRT the PR intervals are greater than PR intervals with delta waves with normal sinus rhythm and retrograde p wave. In antidromic AVRT have short RP interval (less than 100 msec) and wide QRS complex, the delta waves are seen with the normal sinus rhythm and the pathways that are concealed do not display delta waves (Josephson, 2008).
The atrial tachycardia is the supraventricular tachycardia in which the AV junctions, accessory pathway are not required for the initiation. It is of two types: focal AT and multifocal AT. The multifocal atrial tachycardia is more likely to occur in the middle aged people and/or in the individual with heart failure and the chronic obstructive pulmonary disease. It occurs in healthy persons and in people with structurally abnormal hearts such as a person with congenital heart disease. The symptoms of AT includes episodic occurrence, sudden palpitations, dyspnoea, dizziness, fatigue and heart failure. A twelve-lead ECG with the rhythm strip should be used to identify, differentiate and locate atrial tachycardia. Most SVTs ECG (electrocardiogram) typically display a narrow QRS complex tachycardia. The heart rate is variable rages from 100 to 250 bpm. The p wave morphology may provide information about the site of origin and the mechanism of AT. The focal atrial tachycardia shows long RP intervals and P wave shape. The multifocal AT shows 3 different p wave morphologies that are not related to each other and irregular RR intervals (Morris, Brady, & Camm, 2009).
The conduction system of the heart is basically the electrical conduction system that monitors the heart rate. It provides the electrical messages and passes them to the muscle of the heart, stimulating the heart contraction and pumping the blood. The supraventricular tachycardia is the tachycardia in which the heart rate is exceeding more than 100 beats per minute. A 12 lead electrocardiogram should be used to diagnose the SVTs. Some of the measurements of SVT diagnosis are stroke volume, cardiac index, and pulmonary vascular resistance. There are mainly three types of SVTs: Atrioventricular nodal re-entry tachycardia, atrioventricular reciprocating tachycardia, and atrial tachycardia. Each of them has different RP PR intervals, waves, QRS complex and ventricular rate.
Bibas, L., Levi, M., & Essebag, V. (2016). Diagnosis and management of supraventricular tachycardias. CMAJ: Canadian Medical Association Journal, 188(17-18), E466.
Chen, M. A. (2016). Cardiac conduction system. Retrieved from:
Jang, S. W. (2017). Differential Diagnosis of Supraventricular Tachycardia. International Journal of Arrhythmia, 18(1), 43-47.
Josephson, M. E. (2008). Clinical cardiac electrophysiology: techniques and interpretations. (4th ed.). Philadelphia: Lippincott Williams & Wilkins.
Lelakowski, J., Rydlewska, A., & Kuniewicz, M. (2010). Atrioventricular nodal reentrant tachycardia--arrhythmias mechanism, clinical feature and electrocardiographic recordings.Europe PMC, 28(168), 429-437.
Morris, F., Brady, W. J., & Camm, A. J. (Eds.). (2009). ABC of clinical electrocardiography. (2nd ed.). Singapore: John Wiley & Sons.
NHS (2018). Supraventricular tachycardia (SVT). Retrieved from:
Sics editore (2014). Supraventricular tachycardia. Milan, Italy: SICS Editore
Sohinki, D., & Obel, O. A. (2014). Current trends in supraventricular tachycardia management. The Ochsner Journal, 14(4), 586-595.
Stokes, M. B., & Roberts-Thomson, R. (2017). The role of cardiac imaging in clinical practice. Australian Prescriber, 40(4), 151.