Cardiac arrhythmias

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  1. Arrythmia is a generalized term used to denote disturbances in the heart's rhythm. Normal sinus rhythm is characterized by a regular rhythm and PR interval duration range of 0.12 sec - 0.20 sec.
  2. Tachyarrhythmias (HR > 100) – result from either increased automaticity in the pacemaker cells, triggered activity from ectopic impulses, or reentry
    1. Narrow-complex tachycardia (QRS < .12 seconds): Algorhythm – if R-R interval is regular then sinus tach, atrial flutter of fibrillation with fixed AV block, or AV nodal re-entrant tachycardia; if R-R interval is irregular then it is multifocal atrial tachycardia or atrial fibrillation
      1. Sinus tachycardia
        1. Uniform p waves and uniform PR interval
        2. Treatment: usually self-limited but may use beta-blocker
      2. Atrial tachycardia
      3. AV nodal tachycardia
        1. Regular rate – due to reentry through the AV node
        2. No identifiable atrial activity
        3. Treatment: verapamil or diltiazem
      4. Atrial flutter
        1. ‘Sawtooth’ wave form
        2. risk is from inadequate atrial contraction and possible mural thrombus formation
        3. treatment: control ventricular rate with DC cardioversion or digoxin, diltiazem, verapamil, procainamide
        4. NOTE: Wolf-Parkinson-White syndrom is a condition where an accessory, re-entrant pathway in the AV node exists that predispose to recurrent tachycardias both narrow and wide complex. Treatment with digoxin or verapamil that block AV conduction can paradoxically accelerate the ventricular rate by blocking the wrong pathway. These patients should be treated with cardioversion
      5. Atrial fibrillation
        1. Multifocal atrial tachycardia: multiple P wave morphologies and variable P-R interval
          1. usually due to theophylline or electrolyte imbalance or chronic lung disease
          2. treatment: correct electrolytes, stop theophylline, verapamil
    2. Wide-complex tachycardia (QRS > .12 seconds): Algorhythm – if R-R interval is regular then ventricular tachycardia or regular SVT with prolonged AV conduction; if R-R interval is irregular then irregular SVT with prolonged AV conduction
      1. Ventricular tachycardia
        1. Wide complex tachycardia should be treated as probable VT
        2. Treatment: cardioversion immediately then lidocaine 1 mg/kg immediately if no response, the procainamide, magnesium, bretylium
        3. NOTE: Torsade De Pointes (twisting around the points) is a ventricular tachycardia with phasic changes in amplitude and polarity
      2. Ventricular fibrillation is an almost invariable fatal condition that occurs when parts of the ventricles depolarize repeatedly in an erratic, uncoordinated manner
      3. Treatment: electrical defibrillation, epinephrine, vasopressin, amiodarone, lidocaine, magnesium sulfate
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