About Congenital Heart Disease in Dogs and Cats

ACVIM CVHD Consensus Statement Summary

This is a modified recapitulation of an ACVIM consensus statement from the following article published in the Journal of Veterinary Internal Medicine Volume 23, Issue 6, Pages 1142-1150:
Guidelines for the Diagnosis and Treatment of Canine Chronic Valvular Heart Disease
C. Atkins 1 , J. Bonagura 2 , S. Ettinger 4 , P. Fox 5 , S. Gordon 6 , J. Haggstrom 7 , R. Hamlin 3 , B. Keene (Chair) 1 , V. Luis-Fuentes 8 , and R. Stepien 9  
While minor modifications have been made, no attempt was made to change the meaning of the text or editorialize on the statements of the authors.  Nevertheless, you are encouraged to consult the original publication. 

CVHD - Chronic Valvular Heart Disease

Staging system

  • Stage A -  Patients at high risk for developing heart disease but without current identifiable structural disorders ( e.g. cavalier King Charles spaniel without a heart murmur).
  • Stage B -  Patients with structural heart disease that have not developed clinical signs caused by heart failure.
    • B1 – Asymptomatic patients with no radiographic or echocardiographic evidence of cardiac remodeling in response to CVHD
    • B2 – Asymptomatic patients with hemodynamically significant valvular regurgitation as evidenced by radiographic or echocardiographic findings of left-sided heart enlargement
  • Stage C – Patients with past or current clinical signs of heart failure associated with structural heart disease.
    May or may not require hospitalization and aggressive anti-congestive therapy
  • Stage D – Patients with end-stage disease with clinical signs of heart failure caused by CVHD that are refractory to “standard therapy” (defined later).   Such patients may require advanced or specialized treatment strategies in order to remain clinically comfortable ( quality of life ).  May or may not require hospitalization and aggressive anti-congestive therapy.

Uniformity of panelist opinion on diagnostic and treatment recommendations

  • “Consensus” – panelists were unanimous in their opinion on the potential benefit of the approach relative to risk.
  • “NO Consensus” – Available evidence regarding the efficacy of a diagnostic or therapeutic maneuver was conflicting, weak, or absent, and no consensus could be reached by the panelists.

Stage A Consensus Recommendations

  • Small breed dogs ( e.g. Cavalier King Charles spaniels, dachshunds, miniature and toy poodles) should undergo regular evaluations ( yearly examination by the family veterinarian) as part of routine health care.
  • Owners of breeding dogs or those at especially high risk ( e.g. Cavalier King Charles spaniels)  may choose to participate in yearly screening events (dog shows, breed  association  or kennel club events) by board-certified cardiologists participating in an ACVIM approved disease registry.
  • No drug therapy is recommended for any patient.
  • No dietary therapy is recommended for any patient.
  • Potential breeding stock should no longer be bred if mitral regurgitation is identified early, during their normal breeding age (< 6-8 years).

Stage B Consensus Recommendations

  • Thoracic radiography is recommended in all patients to assess hemodynamic significance and obtain baseline images at a time when the patient is asymptomatic.
  • Blood pressure measurement is recommended for all patients.
  • In small breed dogs with typical murmurs, echocardiography is recommended to answer specific questions regarding cardiac chamber enlargement or cause of murmur if those questions were not answered by auscultation or CXR.
     Echocardiography generally is indicated in larger breed dogs because the murmur of MR is more likely to be related to other causes such as dilated cardiomyopathy.
  • Basic laboratory work  is indicated in all patients ( minimum of hematocrit, total protein, serum creatinine, urinalysis)

Stage B1 Therapeutic Recommendations Consensus

  • No drug or dietary therapy is recommended.
  • Reevaluation is suggested by either radiography or echocardiography with Doppler studies in 12 months ( some panelists recommended more frequent follow-up for large breed dogs).

Stage B2 Therapeutic Recommendations NO Consensus (Small Breeds)

  • Angiotensin-Converting Enzyme Inhibitors (ACEI) – For patients with clinically relevant LA enlargement, or those in which the LA has increased in size dramatically on successive examinations, a majority of panelists recommended initiation of ACEI.  Clinical trials addressing efficacy of ACEI for treatment of dogs with stage B2 have had mixed results – either no effect or a small positive effect delaying the onset of CHF. 
  • A minority of panelists recommended no therapy for asymptomatic patients pending further clinical trials.
  • Beta-Blockers – For patients with clinically relevant LA enlargement, or those in which the LA has increased in size dramatically on successive examinations, a minority of panelists recommended initiation of beta-blockers . ( Initiated at a low dosage and titrated upwards to the highest tolerated dosage over 1-2 months) .  
  • A majority  of panelists recommended no beta-blocker therapy for asymptomatic patients pending further clinical trials ( in progress)
  • No other pharmacologic treatments were recommended for Stage B2.  A few panelists consider the use of the following medications for this stage under specific circumstances: pimobendan, digoxin, amlodipine, spironolactone.  Most panelists felt that these treatment strategies need additional investigation into their efficacy and safety for this patient population before a consensus recommendation could be made.
  • Dietary treatment was recommended by a majority of panelists in Stage B2.  A minority of panelists recommended no dietary changes.  Principles guiding dietary treatment at this stage include mild dietary sodium restriction and provision of a highly palatable diet with adequate protein and calories for maintaining optimal body condition.


Stage B2 Therapeutic Recommendations NO Consensus (Large Breeds)

  • Panelists who recommended treatment for smaller breed dogs, strengthened their recommendations for large breeds, promoting the use of both ACEIs and beta blockers.
  • Dietary recommendations for larger breed dogs were the same as those for small breeds, emphasizing mild sodium restriction and adequate protein and caloric intake.

Congestive Heart Failure

  • Acute therapy focuses on regulating hemodynamic status, monitoring and regulating preload, afterload, heart rate, and contractility (the determinants of cardiac performance) to improve cardiac output, decrease the extent of mitral valve regurgitation (if possible), and relieve clinical signs associated with either low cardiac output or excessive venous pressure ( preload, congestion).
  • Chronic therapy focuses on maintaining these hemodynamic improvements while providing treatment aimed at slowing progression, prolonging survival,  and decreasing clinical signs of CHF.

Stage C

  • Includes all patients that have had an episode of clinical heart failure.
    Such patients remain at this stage despite the improvement of clinical signs with standard therapy, even if their clinical signs resolve.
  • Guidelines  differ for in-hospital (acute) versus home care (chronic) management.
    Patients in  either Stage C  or D with acute L-CHF share medical management strategies.

Stage C Diagnosis Consensus

  • The presence of a typical left apical regurgitant murmur in a coughing dog does not necessarily mean that clinical signs are the result of CVHD.
  • A clinical database including CXR, echocardiogram (preferable), and basic laboratory tests must be obtained and examined carefully to accurately determine the cause of clinical signs in dogs with CVHD.
    The signalment and physical examination can be helpful in determining the pretest probability of heart failure as a cause of clinical signs in patients with CVHD.  
    • Obese dogs with no history of weight loss are less likely to be in heart failure.
    • Dogs with marked sinus arrhythmia and relatively slow heart rate also are less likely to have clinical signs attributable to CVHD.
  • Most of these dogs are middle aged or older and it is always prudent to complete the database with a CBC, serum biochemical profile, and urinalysis, especially if therapy for CHF is anticipated.

Stage C Diagnosis NO Consensus

  • Serum NT pro-BNP concentrations should become increasingly useful in determining the cause of clinical signs in dogs with CVHD.   Although there is no doubt that dogs with clinical signs caused by CHF have higher serum BNP concentrations than those with clinical signs caused by primary pulmonary disease, the positive predictive value of an individual BNP concentration has not been adequately characterized at the time of this writing to make a consensus recommendation with regard to BNP testing.

Stage C Acute CHF Therapeutic Recommendations Consensus

  • Furosemide – The specific dosing of furosemide in a dog with CHF should be related to the severity of clinical signs and the response to initial therapy.  (Depends on dosage history also)  Lower or higher doses (e.g. 1-4 mg/kg) may be appropriate in specific cases.  Repeated IV boluses or CRI may be indicated for poorly responsive dogs.
  • For life-threatening pulmonary edema  (expectoration of  froth associated with severe dyspnea; diffuse pulmonary opacity on thoracic radiographs; poor initial response to furosemide bolus with failure of dyspnea and respiratory rate to improve over 2 hours)  furosemide is administered as a CRI at a dosage of 1 mg/kg/hr after the initial bolus.
  • Allow free access to water once diuresis has been initiated.
  • Pimobendan 0.25-0.3 mg/kg PO q12h – Although clinical trial evidence supporting chronic use of pimobendan in the management of Stage C CHF is stronger than for the acute situation, the recommendation to use pimobendan in acute heart failure therapy is strongly supported by hemodynamic and experimental evidence as well as anecdotal experience of the panelists .
  • Oxygen supplementation, if needed, can be administered via a humidity- and temperature-controlled oxygen cage or incubator or via nasal oxygen cannula.
  • Mechanical treatments ( abdominal paracentesis and thoracocentesis)  are recommended to remove effusions judged sufficient to impair ventilation or cause respiratory distress.
  • Provide optimal nursing care including maintenance of appropriate environmental temperature and humidity, head elevation on pillows, and placement of sedated patients in a sternal position.
  • Sedation – anxiety associated with dyspnea should be treated.  Narcotics, or a narcotic combined with an anxiolytic agent, are most often used by panelists.  Butorphenol ( 0.2-0.25 mg/kg) administered IM or IV was the narcotic most often utilized for this purpose; combinations of buprenorphine ( 0.0075-0.01 mg/kg)  and acepromazine (0.01 – 0.03 mg/kg IV, IM, or SQ,  as well as other narcotics including morphine and hydrocodone, also have been utilized.
  • A CRI of sodium nitroprusside for up to 48 hours is often useful for life-threatening, poorly responsive pulmonary edema.

Stage C Acute CHF Therapeutic Recommendations NO Consensus

  • Care must be taken to monitor blood pressure and respiratory response to narcotics and tranquilizers in the setting of acute heart failure.  No specific treatment or dosage regimen was used by all panelists.
  • ACEIs (e.g. enalapril 0.5 mg/kg PO q12h) Although treatment with ACEI is a consensus recommendations for chronic stage C CHF and a majority of panelists also treat acute CHF with ACEI, the evidence supporting ACEI efficacy and safety for acute therapy when combined with furosemide and pimobendan is less clear.  There is, however, clear evidence that the acute administration of enalapril plus furosemide in acute heart failure results in substantial improvement in pulmonary capillary wedge pressure when compared with the administration of furosemide alone (IMPROVE).
  • Nitroglycerin 2 % ointment, ½ inch of paste / 10 kg body weight for 24-36 hours.  Some analysts recommended administering the ointment  in  intervals (12 hours on, 12 off).  Other panelists do not use nitroglycerin in this setting.

Stage C Chronic (Home) Therapeutic Recommendations Consensus

  • Continue with PO furosemide administration to effect , commonly a dosage of 2 mg/kg q12h. The daily furosemide dosage for dogs with CHF is wide and can be as low as 1-2 mg/kg PO q12h to 4-6 mg/kg q8h.  The dosage must be titrated to maintain patient comfort and with attention to effects on renal function and electrolyte status.
  • Chronic oral furosemide > 6 mg/kg q12h needed to maintain patient comfort in the face of appropriate adjunct therapy indicates disease progression to Stage D.
  • Continue or initiate ACEI (e.g. enalapril 0.5 mg/kg q12h) or equivalent dosage of another ACEI if approved for use.  The labeled dosage range of enalapril is 0.25 – 0.5 mg/kg PO q12h; most analysts treat at the upper end of this range.
  • Measurement of serum creatinine and electrolyte concentrations 3-7 days after beginning an ACEI is recommended for animals with Stage C  CHF.
  • Pimobendan is continued at 0.25-0.3 mg/kg PO q12h.
  • Panelists recommend against starting a beta-blocker in the setting of active clinical signs of heart failure ( e.g. cardiogenic pulmonary edema) caused by CVHD.
  • None of the panelists routinely use nitroglycerin in the chronic treatment of Stage C CHF.
  • Participation in a structured, home-based extended care program to facilitate body weight, appetite, respiratory, and heart rate monitoring while providing client support to enhance medication compliance and dosage adjustments in patients with heart failure is encouraged.

Stage C Chronic (Home) Therapeutic Recommendations NO Consensus

  • Spironolactone ( 0.25-2.0 mg/kg PO q12h – q24h) was recommended by a majority of panelists as an adjunct for chronic therapy of dogs with Stage C heart failure.  The primary purpose of spironolactone in this situation is thought to be aldosterone antagonism.  No clinically relevant diuretic effect should be anticipated.  This treatment is now approved in Europe at a dosage of 2 mg/kg/day.
  • Digoxin (0.0025 – 0.005 mg/kg q12h)  with target plasma concentration 8 hours post pill of 0.8 – 1.5 ng/mL.  For the chronic management of Stage C CHF, majority of panelists recommended the addition of digoxin in cases complicated by persistent atrial fibrillation to slow the ventricular response rate.  Some panelists also prescribed the jocks and at this dosage for patients in Stage C heart failure in the absence of sustained supraventricular tachyarrhythmia, as long as no contraindication to digoxin is evident ( elevated serum creatinine concentration, ventricular ectopy, owner compliance concerns, chronic GI disease resulting in frequent or unpredictable bouts of vomiting or diarrhea).
  • Once heart failure signs have resolved, a stable medication regimen has been instituted, and the patient is eating and apparently feeling well, a minority of panelists recommend attempting a low dose, slow upward titration regimen of a beta-blocker. 
  • There is no clinical trial evidence in dogs to support this recommendation.  If prescribed there is no consensus regarding which specific beta blocker to use ( carvedilol, atenolol, or metoprolol are the most frequently prescribed).  The purpose of beta blockade in this setting is related to potential long-term protective effects on myocardial function and remodeling.  These effects have been demonstrated in some experimental animal models and in humans with heart failure, but not in (canine) clinical trials.
  • The presence of atrial fibrilation should strengthens the indication for beta blockade (to slow the ventricular response to atrial fibrillation) for those panelists who recommend a beta blocker.
    In patients receiving a beta blocker before the onset of Stage C CHF, the majority of panelists continue beta blockade; some panelists would consider dosage reduction if needed clinically because of clinical signs of low cardiac output, hypothermia, or bradycardia.
  • Some panelists preferred administration of oral diltiazem ( several formulations available, some sustained release) for chronic heart rate control in atrial fibrillation.
  • Some panelists find cough suppressants useful in occasional patients in Stage C CHF from CVHD.
  • Some panelists find bronchodilators useful in occasional patients in Stage C heart failure from CVHD.

Stage C Dietary Therapy

  • Cardiac cachexia is defined as the unintentional loss of > 7.5% of the patient’s normal, predisease weight, not including weight loss associated with the resolution of edema or the removal of body cavity effusions.  Cachexia has substantial negative prognostic implications, and is much easier to prevent  than to treat. 

Stage C Dietary Recommendations Consensus

  • Maintain adequate calorie intake ( approximately 60 kcal/kg BW) to minimize weight loss (specifically muscle mass loss) that often occurs in CHF.
  • Specifically addressed and inquire about the occurrence of anorexia and make efforts to treat any drug induced or other identifiable causes of anorexia that occur.
  • Record the accurate weight of the patient at every clinical visit, and investigate the cause of weight gain or loss.
    Ensure adequate protein intake and avoid low protein diets designed to treat chronic kidney disease, unless severe concurrent renal failure is present.
  • Modestly restrict sodium intake, taking into consideration sodium from all dietary sources ( dog food, treats, table food and foods used to administer medications)  and avoid any process or other salted foods.
    Monitor serum potassium concentrations and supplement the diet with potassium from either natural or commercial sources if hypokalemia is identified.
  • Hyperkalemia is relatively rare in patients treated for heart failure with diuretics, even in those con currently receiving an ACEI in combination with spironolactone.  Diets and foods with high potassium content should be avoided when hyperkalemia has been identified.


Stage C Dietary Recommendations NO Consensus

  • Consider monitoring serum magnesium concentration, especially has CHF progresses and in animals with arrhythmias.  Supplement with magnesium in cases where hypomagnesemia is identified.
  • Consider supplementing with n-3 fatty acids, especially in dogs with decreased appetite, muscle mass loss, or arrhythmias.


Stage D

  • Patients have clinical signs of failure refractory to standard treatment for Stage C heart failure from CVHD.  Stage D CHF patients receive the maximal recommended/tolerated dosage of furosemide, an ACEI, and pimobendan as outlined for Stage C.
  • Any indicated and tolerated anti-arrhythmic medication, needed to maintain sinus rhythm ( if possible) or regulate the ventricular response rate to atrial fibrillation ( target heart rate 80-160/min) also should be used before a patient is considered  “refractory” to standard therapy.

Stage D Acute CHF Therapeutic Recommendations Consensus

  • In the absence of severe renal insufficiency (e.g. serum creatinine > 3mg/dL), additional furosemide is administered IV as a bolus at 2 mg/kg, followed by either additional bolus doses, or a CRI (1 mg/kg/hr) until respiratory distress has decreased, or for a maximum of 4 hours.  As indicated above, the dosage of  furosemide  varies and higher or lower dosage may be appropriate for a given case.
  • Continue to allow patient free access to water once diuresis has begun.
  • Fluid removal ( abdominal paracentesis, thoracocentesis) as needed to relieve respiratory distress or discomfort.
  • In addition to oxygen supplementation as in Stage C, mechanical ventilatory assistance may be useful to make the patient more comfortable, to allow time for medications to have an affect, and to provide time for left atrial dilation to accommodate  any sudden increase in mitral valve regurgitant volume in patients with acute exacerbation of CVHD ( ruptured chordae tendenae)  and impending respiratory failure.
  • More vigorous afterload reduction in patients that can tolerate arterial vasodilation.  Drugs potentially beneficial include sodium nitroprusside ( starting at 0.5-1.0 g/kg/min), hydralazine ( 0.5-2.0 mg/kg PO), or amlodipine ( 0.05-0.1 mg/kg PO).
  • Direct vasodilators should be started at a low dosage and up-titrated hourly until adequate clinical improvement accompanied by a decrease of 5-10% and systolic blood pressure is observed.
  • These drugs are recommended in addition to an ACEI and pimobendan.  The clinician should be mindful that any decline in blood pressure will also depend on the specific vasodilator drug.  For example, vasodilation effects are rapid onset with nitroprusside, but slower with amlodipine.  Caution is warranted to avoid serious, prolonged hypotension ( maintain systolic BP > 85 mmHg or mean BP > 60 mmHg)
  • Serum creatinine concentration should be measured before and 24-72 hours after administration of these drugs.  patients in Stage D  have life-threatening heart failure and a trial of additional afterload reduction is warranted.  The panel emphasized that afterload reduction may increase cardiac output substantially in the setting of severe mitral regurgitation and heart failure (blood pressure does not necessarily decrease).

Stage D Acute CHF Therapeutic Recommendations NO Consensus

  • Pimobendan dosage may be increased ( off label) to include a third 0.3 mg/kg daily dose.  Some panelists administer an additional dose of pimobendan on admission of Stage D patients with acute pulmonary edema.  Because this recommendation is outside of the FDA approved labeling, this use of the drug should be explained to and approved by the client.
  • In patients judged too sick to wait for the effects of oral afterload reduction or inotropic support, nitroprusside ( for afterload reduction) or dobutamine ( for inotropic support of the hypotensive patient) must be administered by CRI.
    Both drugs can be administered at dosages of 0.5 – 1.0 ug/kg/min  and up titrated every 15-30 minutes to a maximum of 10 ug/kg/min .
  • These drugs can be used separately or in combination for 12-48 hours to improve hemodynamic status and control refractory cardiogenic edema.  Continuous EKG and BP monitoring is recommended to minimize potential risks.
    Sildenafil ( 1-2 mg/kg PO q12h) is used by a minority of panelists to treat acute exacerbations of Stage D heart failure caused by CVHD, even in the absence of confirmed pulmonary hypertension.
  • Bronchodilators are recommended as an adjunct therapy in treating cardiogenic pulmonary edema by a minority of panelists.

Stage D Chronic (Home) Therapeutic Recommendations Consensus

  • Furosemide dosage should be increased as needed to decrease pulmonary edema or body cavity effusions, if use is not limited by renal dysfunction ( which generally should be monitored 12-48 hours after dosage increases). The specific strategy and magnitude of dosage increase  varied widely among the panelists. ( e.g. same dosage increased to TID versus higher dosage BID, substituting a SC dose for a PO dose q48h, or flexible SC dose supplementation based on body weight or girth measurement) .
  • Spironolactone if not already started in Stage C, is indicated for chronic treatment of Stage D patients.
  • Beta blockade generally should not be initiated at this stage unless clinical signs of heart failure can be controlled, as outlined in Stage C.


Stage D Chronic (Home) Therapeutic Recommendations NO Consensus

  • Hydrochlorothiazide was recommended by several panelists as adjunctive therapy with furosemide, utilizing various dosing schedules ( including only intermittent use every 2nd – 4th day).  Some panelists warned of the risk of acute renal failure and marked electrolyte disturbances based on personal experience.
  • Pimobendan dosage is increased by some panelists to include a 3rd 0.3 mg/kg daily dose ( off label use, explanations and cautions apply)
  • Digoxin at the same ( relatively low) dosages recommended for Stage C was recommended for treatment of atrial fibrillation for patients in Stage D.  (Same cautions as listed in Stage C)
  • Digoxin also was recommended by a minority of panelists for all patients in Stage D  in sinus rhythm, assuming no clear contraindication was present.
  • Sildenafil ( 1-2 mg/kg PO q12h)  is used by some panelists to treat Stage D heart failure caused by CVHD or to treat advanced CVHD complicated by pulmonary hypertension.
  • The majority of panelists felt that beta blockade initiated at an earlier stage of heart failure should not be discontinued, but that dosage reduction may be needed if shortness of breath could not be controlled by the addition of other medications or if bradycardia, hypotension, or both were present.  Beta blockade may still be useful to decrease the ventricular response rate in atrial fibrillation after stabilization and digitalization.
  • Cough suppressants are recommended by a minority of panelists to treat chronic, intractable cough in Stage D patients receiving home care.
  • Bronchodilators are recommended by a minority of panelists to treat chronic, intractable cough in Stage D patients receiving home care.

Stage D Dietary Recommendations Consensus

  • All of the dietary considerations for Stage C apply.
  • In patients with refractory fluid accumulation, attempts should be made to further decreased dietary sodium intake if it can be done without compromising appetite or renal function.
     
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