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ECG: Type II Second degree SA Block


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ECG: Type II Second degree SA Block

  1. 1. Prof.S.SUNDAR’s unit Dr.G.Rengaraj.PG ECG OF THE WEEK
  2. 2. History & Exam. <ul><li>A 58 yr. female came with </li></ul><ul><li>c/o chest pain – 1 hr </li></ul><ul><li>no h/o breathelessness, sweating, palpitations,syncope,leg swelling </li></ul><ul><li>Not a known DM/SHT </li></ul><ul><li>O/E pulse- 80/min, BP- 120/80 </li></ul><ul><li>GC fair </li></ul><ul><li>CVS & RS – Normal </li></ul><ul><li>p/a – soft , CNS -NFND </li></ul>
  3. 4. Rhythm strip
  4. 6. <ul><li>IN THIS ECG </li></ul><ul><li>Rate – 74/min </li></ul><ul><li>Rhythm - SINUS rhythm with absent P-QRS-T every 5 th wave </li></ul><ul><li>Axis- LAD </li></ul><ul><li>PR interval – 0.14 s </li></ul><ul><li>P, QRS & T wave morphology – Normal </li></ul><ul><li>The relatively short P-P intervals of 0.68 sec alternate with intervals of 1.36 sec – twice the cycle length of the shorter interval </li></ul>
  5. 7. Ecg <ul><li>This indicates that the long interval is due to the omission of a complete P-QRS-T complex </li></ul><ul><li>Every 5 th impulse is blocked at the SA junction resulting in 5:4 SA block </li></ul><ul><li>Type 2 second-degree SA exit block </li></ul>
  6. 8. Sino-atrial block <ul><li>The sinus impulse is blocked within the SA junction(between SA node–atrial myocardium) </li></ul><ul><li>A complete cardiac cycle ( P-QRS-T ) drops out </li></ul><ul><li>This is a form of exit block, since the impulse cannot exit from its pacemaker site </li></ul><ul><li>There are three types of SA block: </li></ul><ul><li>1. First-degree </li></ul><ul><li>2. second-degree- type 1(wenkebach) </li></ul><ul><li>type 2 </li></ul><ul><li>3. third-degree </li></ul>
  7. 9. SA block <ul><li>First-degree – the SA node impulse is merely slowed. It cannot be recognised on the ECG because SA nodal discharge is not recorded </li></ul><ul><li>Second-degree- </li></ul><ul><li>1. type 1(wenkebach) – the P-R interval progressively lengthens, P-P interval progressively shortens prior to the pause, and the duration of the pause is less than two P-P cycles </li></ul><ul><li>2.type 2 –no change in P-R interval before the pause, an interval without P waves that equals approx. two,three or four times the normal P-P cycle </li></ul><ul><li>Third-degree – complete absence of P waves . Difficult to diagnose without sinus node electrograms </li></ul>
  8. 10. SA node disease <ul><li>SA node dysfunction manifest in ECG as: </li></ul><ul><li>1. sinus bradycardia </li></ul><ul><li>2. sinus pauses </li></ul><ul><li>3. sinus arrest </li></ul><ul><li>4. sinus exit block </li></ul><ul><li>5. chronotropic incompetence </li></ul>
  9. 11. SA Node dysfunction <ul><li>It can be classified as intrinsic or extrinsic </li></ul><ul><li>The distinction is important because extrinsic dysfunction is often reversible and should generally be corrected before considering pacemaker therapy </li></ul><ul><li>The most common causes of extrinsic SA node dysfunction are drugs & ANS influences that suppress automaticity and/or compromise conduction </li></ul><ul><li>Intrinsic sinus node dysfunction is degenerative and often characterised by fibrous replacement of the SA node or its connections to the atrium </li></ul>
  10. 12. Extrinsic causes <ul><li>Autonomic : carotid sinus hypersensitivity </li></ul><ul><li>vasovagal stimulation </li></ul><ul><li>Drugs : beta-blockers, CCB </li></ul><ul><li>digoxin </li></ul><ul><li>anti-arrhythmics( class 1 & 3) </li></ul><ul><li>lithium,amitryptiline </li></ul><ul><li>Hypothyroidism </li></ul><ul><li>Sleep apnea </li></ul><ul><li>Increased ICP </li></ul>
  11. 13. Intrinsic <ul><li>SSS </li></ul><ul><li>CAD ( chronic & acute MI ) </li></ul><ul><li>Inflammatory – pericarditis </li></ul><ul><li>myocarditis </li></ul><ul><li>RHD </li></ul><ul><li>Senile amyloidosis </li></ul><ul><li>Chest trauma </li></ul><ul><li>Iatrogenic- radiation therapy </li></ul>
  12. 14. Diagnosis <ul><li>SA node dysfunction is most commonly a clinical or ECG diagnosis </li></ul><ul><li>Pacemaker implantation is the primary therapeutic intervention in pts with symptomatic SA node dysfuction </li></ul><ul><li>A number of drugs including Beta-blockers & CCB modulate SA node function and such agents should be discontinued prior to making diseases regarding the need for permanent pacing </li></ul>
  13. 15. THANK YOU