Supraventricular Tachycardia (SVT)

Supraventricular Tachycardia (SVT)

  • SVT, or supraventricular tachycardia, is characterized by episodes of a rapid heart rate originating from areas above the ventricles. The roots of the term are:

    • Supra: meaning above

    • Ventricular: relating to the ventricles of the heart

    • Tachycardia: indicating a heart rate greater than 100 beats per minute.

Pathophysiology of SVT

  • The heart contains one primary pacemaker (the SA node) and two backup pacemakers.

  • In SVT, while the SA node operates normally, irregular conduction occurs around the AV node area, causing electrical signals to return to the atrium instead of progressing to the ventricles.

  • This erroneous conduction mechanism results in a rapid heart rate, analogous to a 'merry-go-round.'

Interpretating the EKG of SVT

  1. Rate: -Heart rate ranges from 150 to 250 beats per minute, indicating a very fast rhythm.

  2. Rhythm: -The rhythm is regular and evenly spaced.

  3. P Wave: -Atrial contractions occur, but the P wave is often hidden within the T wave.

  4. PR Interval: -Typically undetectable due to the fast heart rate.

  5. QRS Complex: -The QRS complex is characterized as normal and narrow.

Causes of SVT

  • The nickname 'merry-go-round from hell' reflects the rapid, looping nature of SVT.

  • Major causes include:

    • Stimulants: Examples include caffeine, cigarettes, alcohol (termed the 'three wise men').

      • Intense exercise can also lead to increased heart rate.

    • Sepsis: An infection in the blood can elevate heart rates due to fever and stress responses.

    • Stress: Everyday emotional stresses can trigger SVT.

    • Heart Diseases: Conditions like coronary artery disease (CAD) and CHF (congestive heart failure) can increase stress on the heart.

    • Inflammatory Diseases: Myocarditis and rheumatic heart disease can contribute to episodes.

    • Chronic Lung Conditions: Diseases like COPD add oxygen deprivation and stress on the cardiovascular system.

Signs and Symptoms of SVT

  • Symptoms primarily result from low oxygen levels and decreased cardiac output. Common complaints include:

    • Chest Pain (C)

    • Low Oxygen Saturation (O)

    • Lethargy or Fatigue (L)

    • Anxiety (A)

    • Palpitations (P): Described as a racing heart or gallops felt in the chest.

    • Shortness of Breath (S): Known as dyspnea, referring to difficulty breathing.

    • Elevated Heart Rate (E): Indicative of SVT.

    • Dizziness/Syncope (D): Fainting or near-fainting episodes can occur.

  • An acronym, COLLASPE, encompasses these symptoms to help remember their relationship to low oxygen conditions.

Nursing Interventions and Treatments for SVT

  • The primary outcome goal is to reset and restore normal electrical function within the heart.

  • Initial interventions consist of non-drug treatments:

    • Valsalva Maneuver: Asking the patient to strain as if having a bowel movement can elicit a vagal response that lowers the heart rate.

    • Cold Application: Ice packs around the neck may also stimulate a vagal response.

  • If non-drug methods fail, pharmacological interventions are undertaken:

    • Adenosine: This medication reduces heart rate.

      • Caution: Requires consent, physician presence, crash cart availability, and EKG monitoring.

      • Given rapid bonus within 2seconds , has a half life less than 10seconds so if not given fast, it will metabolise before reaching the target receptor

      • Immediately flush with 20ml normal saline

      • Given through a vein closer to the heart

      • 6mg/2ml first dose and if it does not treat the tach with 1-2min increase dose to 12mg/4ml then 12ml again for 3rd . Max is 12mg in single dose

      • patient can go into a brief period of transient asystole for about 15seconds therefore resuscitation equipment (crash cart) should be made ready in case heart rhythm do not return to normal

  • If drugs do not resolve the issue, more invasive options become available:

    • Cardiac Ablation: A process of destroying abnormally conducting tissue in the heart through burning or freezing.

    • Electrocardioversion: Involves delivering a controlled shock (between 50 to 200 joules) to reset the SA node.

      • Important to differentiate between cardioversion (for arrhythmias like A fib) and defibrillation (for lethal rhythms such as V fib).

    • Transthoracic Echocardiography (TTE): A procedure conducted to rule out the presence of arterial clots before cardioversion.

Patient Education and Discharge Planning

  • Upon hospital discharge, it is important to educate patients about preventing triggers of SVT:

    • The Three S’s: Stimulants, Stress, and Sepsis.

  • Patients may be prescribed medications for heart rate control, such as:

    • Beta Blockers

    • Calcium Channel Blockers

    • Digoxin: Collectively referred to as negative chronotropic agents, which reduce heart rate by influencing time.

Conclusion

  • Understanding SVT involves comprehending its pathophysiology, symptoms, and management to effectively care for and educate patients regarding their heart health.

  • Careful monitoring, quick intervention, and patient education are essential components of effective treatment practices for managing SVT.

Note for NCLEX Preparation

  • Remember the difference between cardioversion and defibrillation:

    • Cardioversion: lower energy shocks (50-200 joules) for arrhythmias.

    • Defibrillation: higher energy shocks (200-360 joules) for life-threatening rhythms.

Always known treatment is vagal manuevers, then adenosine before cardio version I