SVT (Supra ventricular tachycardia)

Introduction

Supraventricular tachycardia is a series of rapid heartbeats that begin in or involve the upper chambers (atria) of the heart. Electrical signals in the heart's upper chambers fire abnormally, which interferes with electrical signals coming from the sinoatrial (SA) node the heart's natural pacemaker. A series of early beats in the atria speeds up the heart rate. The rapid heartbeat does not allow enough time for the heart to fill before it contracts so blood flow to the rest of the body is compromised. (Heartorg, 2015)

SVT can cause the heart to beat very rapidly or erratically. As a result, the heart may beat inefficiently, and the body may receive an inadequate blood supply. There are three major types of SVT including:
atrial fibrilation
paroxysmal supraventricular tachycardia (PSVT)
atrial flutter & atrial tachycardia (Patientcouk, 2015)

Presentation

Signs & symptoms 

• Dizziness
• Lightheadedness
• Rapid heartbeat or "palpitations"
• chest pain
• Shortness of breath
• syncope 
• sweating 
• polyuria
• fatigue 

Causes 

SVT is results from reentry mechanism as following conditions:
Premature atrial and ventricular ectopic beats
Hyperthyroidism 
Stimulants such as caffeine, drugs and alcohol
Certain medicines such as Digoxin, theophylline high doses can cause SVT. 
Inherited conditions such as Wolff- Parkinson-white syndrome can cause for SVT (WebMd 2014). 

Risk factors

·         Medications. These include some asthma inhalers, some types of herbal supplements and cold remedies.

·         Drinking large amounts of caffeine or alcohol.

·         Stress or emotional upset.

·         Smoking.

Investigations

ECG allows identifying tachyarrhythmia and any abnormality in heart activity.

FBC to detect precipitating factor

Thyroid function tests

Chest x-ray to detect any pulmonary edema, any infection

Echocardiogram if structural heart disease is suggested

Digoxin levels in blood if the patient is in Digoxin

Cardiac enzymes

Blood tests (WebMd 2014)

Serum electrolytes

Management

• Carotid sinus massage: gentle pressure on the neck, where the carotid artery splits into two branches. Must be performed by a healthcare professional to minimize risk of stroke, heart or lung injury from blood clots.
• Pressing gently on the eyeballs with eyes closed.
• Valsalva maneuver: holding your nostrils closed while blowing air through your nose.
• Dive reflex: the body's response to sudden immersion in water, especially cold water.
• Sedation.
• Cutting down on coffee, alcohol, tobacco use.
• Getting more rest.(Sesupport sesupport, 2015)
• In patients with wolfe parkinson white syndrome, medications or ablation may be needed to control PSVT.

·         Medications: Patients may be given adenosine (Adenocard), a short-acting medication that decreases the heart rate by blocking the SA node conduction for a few seconds. This medication is given by IV to act quickly. Adenosine has some temporary side effects, including facial flushing, chest pain, shortness of breath, nausea, and dizziness. If a single dose does not stop supraventricular tachycardia, then the doctor may give higher doses. Adenosine successfully stops paroxysmal supraventricular tachycardia (PSVT) of all types in more than 90% of cases.

·         Other medications: If adenosine is unsuccessful, other medications can be used, such as calcium channel blockers (diltiazem), digoxin(Lanoxin), or beta-blockers (esmolol). Blood pressure is monitored carefully with these drugs.

·         Pacemaker: A pacemaker is an electronic device that takes over the role of the SA node as pacemaker of the heart. It is often implanted inside the heart by a cardiologist or an electrophysiologist in the cardiac catheter lab, or by a surgeon.

·         Other treatments: In special cases, the source of the arrhythmia or abnormal electrical pathways can be interrupted by chemicals, ablated by high frequency energy through a catheter [such as in patients with regular recurrent PSVT or the Wolff-Parkinson-White (WPW) syndrome], or by a surgeon; but this is done infrequently for PSVT.

References

Heartorg. 2015. Heartorg. [Online]. [8 May 2015]. Available from: http://www.heart.org/HEARTORG/Conditions/Arrhythmia/AboutArrhythmia/Tachycardia-Fast-Heart-Rate_UCM_302018_Article.jsp

Sesupport sesupport. 2015. Hopkinsmedicineorg. [Online]. [8 May 2015]. Available from: http://www.hopkinsmedicine.org/heart_vascular_institute/conditions_treatments/conditions/supraventricular_tachycardia.html

Webmdcom. 2014. Webmdcom. [Online]. [7 May 2015]. Available from: http://www.webmd.com/heart-disease/tc/supraventricular-tachycardia-overview

Patientcouk. 2015. Patientcouk. [Online]. [8 May 2015]. Available from: http://www.patient.co.uk/health/supraventricular-tachycardia