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Electrical Alternans: Alternating r-wave amplitudes. This suggests excessive movement of the heart, and is associated with pericardial effusion.
Antiarrhythmic medications have the potential for inducing arrhythmias, or worsening arrhythmias. Treatment of arrhythmias is indicated to alleviate cardiovascular compromise, reduce the risk for potentially life-threatening arrhythmias, and to reduce the risk of myocardial damage. Oxygen is administered. Electrolyte imbalances, severe acidemia, hypoxemia, hypoglycemia and exposure to drugs/toxins that affect myocardial function are immediately addressed. It is not unusual for ventricular arrhythmias in the dog to
be associated with abdominal organ dysfunction such as hepatic or splenic masses. Hyperthyroidism should be investigated for when an older cat presents with a tachycardia.
Supraventricular tachyarrhythmias may be manipulated by inducing a vagal maneuver (gently pressing in on the eyes or carotid artery). For acute therapy, IV calcium channel blockers and beta blockers may be used. Life-threatening refractory SVT may be treated with adenosine, digoxin, phenylephrine or edrophonium. Chronic therapy may include oral digoxin +/- beta- blocker or calcium channel blocker.
Ventricular tachyarrhythmias are generally not treated unless they are electrically unstable or promote hemodynamic instability. Examples include multiform complexes, r on t phenomenon, rapid tachycardia (>180- 200 bpm). In acute situations lidocaine is administered
IV. Additional medication may include IV procainamide, amiodarone, esmolol or sotalol. Cardioversion in some instances is necessary. Chronic therapy may include treatment with oral sotalol, atenolol, mexiletine, or procainamide.
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