Treatment

Goals of therapy:

1. Correct dysrhythmias:
   • Beta blocker therapy
     • Propranolol
     • Metoprolol
     • Atenolol
   • Class I antidysrhythmic therapy
     • Lidocaine analog (tocainide, mexiletine)
     • Procainamide (sustained release)
       
2. Improve left ventricle distensibility:
   • Beta blocker therapy:
     • Propranolol
     • Metoprolol
     • Atenolol

Definitive treatment:

• Surgical correction:
  • Require cardiopulmonary bypass – thus technically challenging
    • Very few centers in North America can address these cases
  • Dilation of the stenosis with a metal dilator – generally not effective
• Balloon Valvuloplasty:
  • Ineffective against the firm fibrotic lesion of SAS
• Thus no definitive treatment is available

Dosages

• Propranolol dog: 0.2-1 mg/kg TID (PO); 0.04-0.06 mg/kg slowly IV
• Metoprolol dog: 0.5-1 mg/kg TID (PO)
• Atenolol dog: 5-12.5 mg SID (PO)
• Lidocaine dog: 2-4 mg/kg slow (IV), repeat q 10 min to max. of 8 mg/kg; 25-75 ug/kg/min (CRI)
• Tocainide dog: 5-10 mg/kg TID-QID (PO); Dr. Hamlin suggests 25 mg/kg QID (PO)
• Mexiletine dog: 2-5 mg/kg BID-TID (PO) we have dosed some dogs at 8-10 mg/kg
• Procainamide dog: 6-8 mg/kg (IV) over 5 min; 25-40 ug/kg/min (CRI); 8-20 mg/kg q 4-6 hr (IM), TID (PO) sustained release

Consequences:

• Congestive heart failure:
  • Uncommon
    • Occurs in older dogs
    • More likely to manifest if moderate to severe MR and/or AI are/is also present
• Syncope/sudden death
  • Ventricular arrhythmias are common
  • Exertional syncope is common
  • Sudden death is the most common outcome with SAS, most occurring by 3 years of age
  • Weakness may also manifest
  • Average survival is 14.4 months