HEART BLOCK | SA BLOCK
HEART BLOCK | SA BLOCK…Improper formation of sinoatrial impulse and its propagation through the junctional tissues of the heart iss called Heart Block. In fact any defect in the conducting system of the heart is known as Heart block.HEART BLOCK | SA BLOCK
- SA block.
- AV block.
- Bundle branch block.
- Arborisation or Purkinjee block.
HEART BLOCK | SA BLOCK……..It is due to excessive vagal tone from different neurohumoral factors. Ischaemia, fibrosis or calcification of SA node and drugs, e.g. Ca-channel blockers, Digitalis, Antiarrhythmic drugs or Sympatholytic drugs are also responsible. As no impulse is generated in the SA node, heart as a whole will miss a beat. Therefore, there is dropped beat in the pulse and during this period no heart sounds are audible and no pulsation in jugular vein is seen. ECG is diagnostic which shows complete absence of all complexes provided no escape beats occur and the P-P interval is usually multiple of previous P- P interval. This is also known as Mobitz type II SA block. Sometimes there is progressive shortening of sinus P-P interval before the long pause. This is called Sinoatrial Wenckebach or Mobitz type ISA block. In Mobitz type II SA block, sinus impulse transmission is blocked at the SA junction leading to absence of P waves of sinus origin.) SA block should be differentiated from sinoatrial arrest or sinus pause where P-P interval is simply prolonged. SA block is actually included under sick sinus syndrome (SSS). HEART BLOCK | SA BLOCK
In many cases no treatment is necessary, The offending drug (usually Digitalis) if in use should be withdrawn. Atropine sulphate 0,6 mg four times daily or Ephedrine sulphate 25 mg four times daily may be given. Atropine may also be given intravenously in the dose of 0.5 to 1 mg. When Sick sinus syndrome is associated it should be treated accordingly. Sometimes permanent pacing is required when ventricular asystole is greater than 3 seconds.