Paroxysmal Supraventricular Tachycardia (PSVT)
Paroxysmal Supraventricular Tachycardia (PSVT)
The Valsalva Manoeuvre is the first line of treatment for hemodynamically stable patients with PSVT aiming to exhale through a closed airway in order to revert the heart back into its natural rhythm. This manoeuvre involves the patient blowing into a syringe for 15 seconds and aiming to push the plunger along the barrel of the syringe and works in four phases:
Phase 2: The cessation of the transient period causes a decrease in aortic pressure and an increase in heart rate.
Phase 3: Quick release of the strain causes an abrupt aortic pressure drop that has a resultant compensatory increase in heart rate.
Phase 1: The start of the strain results in an increase in intrathroacic pressure which has an effect on the aorta causing aortic pressure to transiently increase.
Phase 4: The increase in venous return, preload and cardiac output cause an increase in aortic pressure with compensatory "overshoot" of blood pressure causing bradycardia.
Coughing while sitting forward
Method used to revert the arrhythmia back to the natural rhythm of the heart by delivering an electric shock. Typically used in PSVT patients that are hemodynamically compromised.
Oxygen, IV fluids and Aspirin (if myocardial ischemia is suspected) should also be considered in the emergency treatment of patients with PSVT.
Drugs (refer to Pharmacology).
PSVT was found to be significantly more common in women with 75% of cases occurring in females.
PSVT is just as likely to occur in young and healthy patients as it is to occur in patients suffering chronic heart disease.
Mostly asymptomatic, short bursts of PSVT were found by 24-hour heart monitoring in over 50% of the elderly population with the incidence increasing in correlation with increasing age.
An SVT and also a PSVT needs to be captured on an electrocardiogram (ECG) to be correctly diagnosed. Without the print-out of the PSVT on the ECG, clinicians can not offer treatment to aim to completely eradicate the arrhythmia by medication or ablation.
Sometimes, a Holter heart monitor is required outside of the pre-hospital and hospital setting in order to capture an SVT.
An ECG machine can be used in the pre-hospital and hospital setting to capture a PSVT if the machine is attached while the paroxysmal arrhythmia is still in progress. To diagnose an SVT or PSVT , the ECG will show a narrow complex tachycardia with a regular rhythm and absent or inverted P waves. The heart rate will be between 150 and 250 beats per minute and the QRS complexes will be normal.
Requires ectopic beat to initiate and is
caused by altered automaticity,
triggered activity or re-entry and
classified by origin and regularity.
If the re-entry mechanism only involves the AV node, it is termed AV Nodal Re-entry Tachycardia or AVNRT. This is a functional re-entry circuit and is the most common type of PSVT's.
If the re-entry mechanism involves the AV node and an accessory pathway or bypass tract that is located in the ventricle it is termed Atrioventricular Re-entry Tachycardia or AVRT. This is an anatomical re-entry circuit commonly linked to the Bundle of Kent.
Atrial Tachycardia is also classified under PSVT however is more commonly seen in patients with cardiomyopathy. It is usually caused by a single site of discharge in left or right atria.
PSVT usually presents with signs and symptoms related to the poor perfusion and excessive heart rate that is characteristic of the condition and occasionally a history of previous PSVT. These signs and symptoms can have a rapid onset and offset just like the condition and may last for several minutes to several hours.
Chest tightness/Chest pain due to the excessive pumping of the heart muscle at the tachycardic rate.
Rapid or no pulse because it is simply too fast to feel or the blood pressure is too low to find one.
Anxiety due to feeling symptoms such as palpitations, chest tightness and shortness of breath.
Dyspnoea due to poor perfusion and lack of blood flow to pulmonary circulation because of restricted ventricular filling.
Dizziness and Syncope due to poor perfusion because of restricted ventricular filling.
Palpitations caused by excessive pumping and contracting of heart due to the arrhythmia.
History of PSVT is important as information can be gathered on how the condition resolved the previous time/s.
Considered if vagal manoeuvres are ineffective at terminating the SVT or if the patient is hemodynamically unstable to use vagal manoeuvres.
Short-term management involves intravenous adenosine or calcium channel blockers. Adenosine the first line of drugs that is used for PSVT and is a short acting medication that inhibits AV node conduction. Statistics show it terminates 90% of tachycardias caused by AVNRT and AVRT. Adenosine can cause chest pain and dizziness and has an extremely short half-life of 10-20 seconds. Calcium channel blockers like verapamil and diltiazem and beta blockers like metoprolol or esmolo are also used. They have a longer half life than adenosine and some also have AV blocking capabilities.
Long-term management involves a medication regime tailored to each patient based on the type of tachyarrhythmia and the length and frequency of PSVT episodes. The regime will also take into consideration the symptoms that are experienced by the patient in order to facilitate the best outcome.
Major risk factors for PSVT include stimulant use which includes alcohol, caffeine, drug use, emotional stress, certain medications and smoking. These are all triggers for PSVT as well as risk factors.
What is it?
PSVT is an episodic condition that involves a rapid onset and termination. Paroxysmal meaning abrupt reoccurances of symptoms and supraventricular meaning above the ventricles. It is a regular, narrow complex tachyarrhythmia with a heart rate over 150 beats per minute.