Canine Cardiac Emergencies
Pathogenesis
Cardiac emergencies in dogs occur when the heart cannot maintain adequate circulation, fluid accumulates because of cardiac dysfunction, or abnormal electrical activity interferes with effective heart contractions. These problems may occur independently or together, producing respiratory distress, poor tissue perfusion, abnormal heart rhythms, and circulatory shock.
The major emergencies include congestive heart failure, low-output heart failure, and clinically significant arrhythmias. Understanding which process is occurring is essential because treatments that benefit one cardiac emergency may worsen another.
Congestive heart failure and pulmonary edema
Congestive heart failure (CHF) occurs when cardiac dysfunction results in fluid accumulation. One important manifestation is pulmonary edema, the accumulation of fluid within the lungs.
Dogs with pulmonary edema commonly develop coughing and difficulty breathing, also called dyspnea. Coughing may be particularly noticeable at night. Affected dogs may also have tachycardia (an abnormally rapid heart rate), hypothermia (low body temperature), and a heart murmur.
Not every dog with respiratory distress has congestive heart failure. A dog experiencing respiratory difficulty without tachycardia or a heart murmur may have a primary respiratory disorder instead.
Some dogs develop a congestive crisis following corticosteroid administration. When steroid exposure precipitates an episode, the long-term course may differ from that of dogs with progressive underlying cardiac disease.
Low-output heart failure
Low-output heart failure develops when the heart cannot generate enough forward blood flow to maintain adequate circulation.
This form of failure is associated with dilated cardiomyopathy (DCM), a condition involving cardiac dilation and impaired contractility, meaning the heart muscle cannot contract effectively.
These dogs can experience congestion and circulatory shock simultaneously. Poor blood flow may produce cold extremities, hypothermia, and decreased mentation or alertness.
This combination creates a treatment challenge. Medications used to remove excess fluid can help congestion, but excessive fluid removal may further compromise circulation when cardiac output is already inadequate.
Some cases of dilated cardiomyopathy may respond to taurine supplementation.
Pleural effusion
Pleural effusion is the accumulation of fluid within the space surrounding the lungs.
Although pleural effusion can occur with cardiac disease, dogs presenting with this finding are more likely to have a condition other than primary cardiac disease. Identifying the underlying cause is therefore important rather than automatically attributing the fluid to heart failure.
Cardiac arrhythmias
Arrhythmias occur when the heart's electrical activity produces an abnormal rhythm. Depending on the disturbance, the heart may beat too slowly, too rapidly, or irregularly.
Several categories of underlying causes can contribute:
Cardiac disease. Myocarditis (inflammation of the heart muscle), endocarditis, advanced valvular disease, cardiomyopathy, congenital heart disease, cardiac tumors, fibrosis, ischemic injury, and inherited electrical abnormalities can produce arrhythmias.
Electrolyte disturbances. Abnormal potassium, magnesium, or calcium concentrations can disrupt cardiac electrical activity.
Autonomic influences. Pain, anxiety, stress, and conditions such as pheochromocytoma may contribute to abnormal rhythms.
Drugs and toxins. Albuterol, chocolate, Proin, and certain antiarrhythmic medications can be associated with arrhythmias.
Systemic disease. Sepsis, shock, hypoxia (inadequate oxygen availability), immune-mediated hemolytic anemia, pancreatitis, trauma, gastric dilatation-volvulus, splenic neoplasia, uremia, envenomation, and thyroid disease may produce secondary cardiac rhythm disturbances.
Bradyarrhythmias
Bradyarrhythmias are abnormally slow heart rhythms.
Second- and third-degree atrioventricular (AV) block occur when electrical conduction between the upper and lower chambers of the heart is impaired.
Another important cause is hyperkalemia, an abnormally elevated blood potassium concentration. Severe hyperkalemia can produce atrial standstill, in which normal atrial electrical activity disappears, accompanied by abnormal ventricular electrical activity.
Supraventricular tachycardia and atrial fibrillation
Supraventricular tachycardia (SVT) is a rapid, abnormal rhythm arising from electrical activity in the atria or atrioventricular junction.
SVT may result from a primary conduction abnormality, structural heart disease, or noncardiac conditions such as sepsis, pancreatitis, gastric dilatation-volvulus, or splenic torsion.
Atrial fibrillation is another supraventricular arrhythmia, characterized by a persistently irregular rhythm. It is usually associated with significant underlying cardiac disease.
When atrial fibrillation produces a rapid ventricular response, the resulting heart rate can interfere with adequate cardiac filling. This is why treatment commonly focuses on slowing the heart rate rather than necessarily restoring a normal rhythm.
Ventricular arrhythmias
Ventricular premature complexes (VPCs) are abnormal electrical beats originating within the ventricles.
Some ventricular rhythms are relatively well tolerated and do not require antiarrhythmic medication. Others can compromise blood pressure and circulation.
The clinical importance depends on the rhythm's persistence, speed, electrical characteristics, and whether it produces weakness, hypotension, or other signs of inadequate circulation.
Common client questions
Why is my dog coughing so much at night?
Coughing, especially at night, is a common finding in dogs with pulmonary edema associated with congestive heart failure. Fluid accumulation in the lungs can interfere with normal breathing, although coughing alone does not establish that heart disease is responsible.
Why is my dog breathing so fast and struggling to breathe?
Pulmonary edema can cause significant respiratory distress when fluid accumulates within the lungs. Other respiratory diseases can produce similar signs, so cardiac assessment and chest imaging help distinguish between these possibilities.
Why does my dog have a heart murmur and suddenly can't breathe?
A heart murmur can accompany cardiac disease and pulmonary edema. When a dog with a murmur develops acute respiratory distress, congestive heart failure becomes an important diagnostic consideration, but additional testing is needed to identify the cause.
Why is my dog so cold and weak with heart disease?
Dogs experiencing low-output heart failure may develop circulatory shock because the heart cannot generate adequate blood flow. Cold extremities, reduced alertness, and hypothermia can indicate impaired circulation.
Why is my dog's heart beating so fast?
Rapid heart rates may occur with congestive heart failure, supraventricular tachycardia, atrial fibrillation, or ventricular tachycardia. An electrocardiogram helps determine whether the rapid rate is a response to another medical problem or an abnormal electrical rhythm requiring specific treatment.
Why is my dog's heartbeat irregular?
An irregular heartbeat can result from abnormal electrical activity, including atrial fibrillation or ventricular premature complexes. Some irregular rhythms require treatment, while others are managed by addressing the underlying medical condition.
Why is there fluid around my dog's lungs?
Fluid surrounding the lungs is called pleural effusion. Although heart disease can be involved, veterinarians also investigate noncardiac causes because pleural effusion is not specific to cardiac failure.
Why did my dog's heart condition get worse after taking steroids?
Corticosteroid administration can precipitate a congestive heart failure crisis in some dogs. If the dog survives the initial episode, some may subsequently require little or no long-term cardiac medication, depending on the underlying disease.
Diagnostics for Canine Cardiac Emergencies
The diagnostic evaluation of a canine cardiac emergency has three primary purposes: determining whether the heart is responsible for the presenting signs, assessing how severely circulation or breathing is compromised, and identifying abnormalities that may change treatment.
Thoracic radiographs
Chest radiographs (X-rays) are used to evaluate dogs with suspected congestive heart failure or pulmonary edema.
Findings may include patchy interstitial lung markings, enlarged pulmonary blood vessels, pleural fissure lines, or pleural fluid.
These findings help assess whether respiratory distress is associated with cardiac congestion and whether additional evaluation is needed.
When pleural effusion is present, radiographs may be repeated after thoracocentesis (removal of fluid from the space surrounding the lungs). Removing the fluid can improve visualization of underlying abnormalities, including masses that were previously obscured.
Echocardiography
Echocardiography uses ultrasound to evaluate cardiac structure and function.
A brief emergency echocardiogram can identify enlargement of the left atrium, assess cardiac contractility, and detect or exclude pericardial effusion (fluid within the sac surrounding the heart).
Contractility is particularly important when distinguishing a primary rapid arrhythmia from a rhythm disturbance associated with dilated cardiomyopathy.
A more comprehensive echocardiogram provides further evaluation of the underlying cardiac disease. In dogs requiring oxygen support, examination may be deferred until respiratory stability allows it.
Electrocardiography
An electrocardiogram (ECG) records the heart's electrical activity and is the principal diagnostic test for identifying arrhythmias.
A lead II ECG helps distinguish rhythms according to their regularity, electrical waveforms, and the width of ventricular electrical complexes.
Important findings include:
Atrioventricular block. Abnormal electrical conduction between the atria and ventricles supports the diagnosis of second- or third-degree AV block.
Hyperkalemia-associated atrial standstill. Absent P waves, abnormal widened QRS complexes, and tall, peaked T waves can indicate severe potassium-associated electrical disturbances.
Supraventricular tachycardia. A rapid, generally regular rhythm with abrupt onset or termination supports SVT rather than a normal physiologic increase in heart rate.
Atrial fibrillation. A persistently irregularly irregular rhythm supports the diagnosis.
Ventricular arrhythmias. Abnormal ventricular complexes identify ventricular-origin rhythms. Their electrical characteristics can also help guide investigation of underlying cardiac disease.
Continuous ECG monitoring is also used during treatment when medications or underlying cardiac dysfunction create concern for additional arrhythmias.
NT-proBNP
NT-proBNP is a cardiac biomarker used to help assess whether respiratory signs may be associated with heart failure.
A normal or near-normal result in a dog presenting with cough or dyspnea makes heart failure less likely.
This test helps distinguish cardiac from noncardiac causes of respiratory distress rather than independently establishing a definitive diagnosis.
Blood pressure
Blood pressure measurement evaluates circulatory stability and helps determine whether medications can be used safely.
Hypotension may indicate inadequate cardiac output or impaired circulation. Blood pressure also helps assess the significance of ventricular arrhythmias and the response to cardiovascular medications.
Complete blood count and serum chemistry
A complete blood count (CBC) evaluates blood cell populations, while serum chemistry identifies metabolic abnormalities and assesses organ function.
These tests help identify systemic conditions that may contribute to arrhythmias and establish baseline organ function before or during treatment.
Kidney values are particularly important in dogs receiving furosemide, since removing excess fluid requires attention to renal function.
Electrolytes, blood gases, and acid-base assessment
Blood gas and electrolyte testing helps evaluate potassium, calcium, and other physiologic disturbances that may influence cardiac rhythm and treatment.
Acid-base abnormalities, electrolyte disturbances, and inadequate oxygenation may contribute to ventricular arrhythmias. Correcting these problems can reduce the need for or improve the effectiveness of antiarrhythmic treatment.
Urinalysis and urine specific gravity
Urinalysis helps assess renal and systemic abnormalities.
Urine specific gravity provides information about urine concentration and is particularly useful as a baseline before diuretic treatment changes urine production.
Packed cell volume and total solids
Packed cell volume (PCV) and total solids (TS) provide information about circulating red blood cells and blood protein concentrations.
These values contribute to the initial assessment of a critically ill dog.
When a dog coughs up fluid, the protein concentration of that fluid may also help determine whether cardiac pulmonary edema is likely.
Thyroid testing
Thyroid testing, including T4 and TSH, may be included when evaluating potential underlying contributors to arrhythmias.
Cardiac troponin
Cardiac troponin is a biomarker used to assess evidence of cardiac muscle injury.
An elevated result may prompt further investigation of underlying infectious disease or other causes of cardiac injury.
Infectious disease testing
When myocardial injury or infectious causes of arrhythmia are suspected, testing may include a 4DX panel and evaluation for Chagas disease.
Blood cultures may also be considered when an infectious cause is suspected.
Abdominal ultrasound
Abdominal ultrasound helps investigate noncardiac conditions that can contribute to arrhythmias, including splenic disease and other abdominal abnormalities.
This is particularly relevant when the rhythm disturbance may be secondary to systemic illness rather than a primary cardiac electrical disorder.
Treatment of Canine Cardiac Emergencies
Treatment depends on whether the emergency involves fluid accumulation, inadequate cardiac output, an abnormal rhythm, or a combination of these processes.
Stabilization and identification of the underlying cardiac problem guide subsequent medication choices.
Respiratory stabilization and congestive heart failure
Dogs with pulmonary edema and respiratory distress receive supplemental oxygen to support breathing.
An oxygen cage may reduce handling-related anxiety, which can be important when respiratory effort is already increased.
Furosemide is a diuretic used to remove excess fluid associated with congestive heart failure and pulmonary edema.
Dogs already receiving chronic furosemide treatment, or those with concurrent kidney disease, may respond differently and require individualized treatment.
Pimobendan is used to support cardiac function in dogs with congestive heart failure. Published research has also associated pimobendan treatment in dogs with mitral valve disease with reduced recurrence of pulmonary edema.
Butorphanol may be used to reduce anxiety and distress during stabilization. Acepromazine is another option when blood pressure is appropriate.
Blood pressure, respiratory status, and kidney function are assessed throughout treatment to evaluate therapeutic response and identify adverse physiologic effects.
Beta-blockers are generally avoided during active congestive heart failure because reducing heart rate can compromise the cardiac response needed to maintain circulation. Exceptional circumstances involving severe tachycardia may require specialist-directed treatment.
Low-output heart failure
Low-output heart failure requires a balance between reducing congestion and maintaining forward blood flow.
Furosemide may still be needed when pulmonary congestion is present, but excessive diuresis can be problematic in dogs already experiencing circulatory shock.
Pimobendan is used to support cardiac contractility.
When severe hypotension is caused by poor contractility, dobutamine may be used to improve cardiac pumping function.
Dogs receiving dobutamine require continuous ECG monitoring because ventricular ectopy, or abnormal ventricular electrical beats, may develop.
Taurine supplementation may be considered in dogs with cardiac dilation and poor contractility when taurine-responsive cardiomyopathy is suspected.
Pleural effusion
Thoracocentesis removes fluid from the space surrounding the lungs.
Following fluid removal, repeat thoracic radiographs may reveal underlying disease that could not be adequately evaluated before drainage, including thoracic masses.
Further treatment depends on the identified cause of the effusion.
Bradyarrhythmias and atrioventricular block
Atropine may be used in dogs with second- or third-degree atrioventricular block to assess whether the heart rate responds to medication.
When clinically significant conduction abnormalities do not respond, implantation of a cardiac pacemaker may be necessary.
Hyperkalemia-associated atrial standstill
Treatment focuses on correcting the elevated potassium concentration and identifying its underlying cause.
Calcium gluconate is used to address the cardiac effects of hyperkalemia.
Regular insulin and dextrose are used together to reduce circulating potassium while supporting blood glucose.
Fluids may also be needed, depending on the underlying disease and circulatory status.
ECG and blood glucose monitoring help evaluate treatment response and identify complications.
Supraventricular tachycardia
The first step is determining whether the rapid rhythm reflects a primary electrical abnormality, structural cardiac disease, or another systemic illness.
Identifying the underlying cause is particularly important because treatment choices depend on cardiac contractility and the presence or absence of concurrent heart failure.
Vagal maneuvers, which attempt to influence heart rate through autonomic reflexes, may be considered in selected cases.
A precordial thump, a physical maneuver intended to interrupt the arrhythmia while ECG activity is observed, is another described intervention.
Medications used for SVT include:
Diltiazem. Used to slow conduction and control rapid supraventricular rhythms. Its cardiovascular effects require careful administration and monitoring.
Esmolol. A beta-blocker considered for selected rapid supraventricular arrhythmias when appropriate for cardiac function.
Sotalol. An antiarrhythmic option for selected patients, but avoided when cardiac contractile dysfunction makes its use inappropriate.
Digoxin. May be considered for rhythm management when concurrent heart failure is present.
Some dogs with an abnormal accessory electrical pathway may benefit from catheter ablation, a procedure intended to eliminate the pathway responsible for recurrent tachycardia.
Atrial fibrillation
Atrial fibrillation is generally managed by controlling the ventricular rate to improve cardiac filling.
Diltiazem and digoxin are used for rate control. Their combined use can be more effective than either medication alone.
Beta-blockers may be considered in selected cases when adequate rate control is not achieved, although concurrent congestive heart failure significantly influences medication selection.
Digoxin requires careful monitoring because drug interactions and electrolyte abnormalities, particularly hypokalemia (low blood potassium), may increase the risk of toxicity. Serum digoxin concentrations help assess medication exposure.
Electrical cardioversion, a procedure using a controlled electrical shock to restore cardiac rhythm, may be considered in selected dogs with atrial fibrillation without underlying structural heart disease.
Lidocaine is also described as a specific option for atrial fibrillation developing under anesthesia, rather than as routine treatment for atrial fibrillation.
Ventricular tachycardia
Not every ventricular rhythm requires antiarrhythmic medication.
Isolated ventricular premature complexes and accelerated idioventricular rhythm (AIVR), a relatively organized ventricular rhythm without associated pulse deficits, may be managed by addressing the underlying disease.
More concerning ventricular rhythms are those that persist, compromise blood pressure, produce clinical weakness, or demonstrate dangerous electrical characteristics such as an R-on-T phenomenon, in which a ventricular beat occurs during a vulnerable portion of the preceding electrical cycle.
Before using antiarrhythmics, treatment includes evaluating and correcting oxygenation, electrolyte concentrations, calcium abnormalities, acid-base disturbances, and circulatory volume status when appropriate.
Pain control with opioid medications may be important when ventricular arrhythmias occur after procedures such as surgery for gastric dilatation-volvulus or splenectomy.
Medications and procedures used for clinically significant ventricular tachycardia include:
Lidocaine. Used to suppress clinically important ventricular arrhythmias.
Mexiletine. A medication with antiarrhythmic effects similar to lidocaine, used for ongoing ventricular rhythm management.
Magnesium sulfate. May be considered for ventricular arrhythmia management, particularly when magnesium abnormalities are relevant.
Sotalol. Used for selected ventricular arrhythmias, including ventricular tachycardia in Boxers when cardiac contractility is adequate.
Procainamide. An alternative when lidocaine is ineffective and potassium and magnesium status have been assessed.
Amiodarone. Another antiarrhythmic option for ventricular tachycardia.
Electrical cardioversion. May be used for selected ventricular arrhythmias under anesthesia.
For German Shepherd Dogs with familial ventricular tachycardia, combined sotalol and mexiletine may be preferred rather than sotalol alone.
Monitoring and hospitalization
Dogs experiencing cardiac emergencies may require hospitalization for respiratory support, cardiovascular medication, serial diagnostic assessment, and observation for recurrent abnormalities.
Monitoring is directed at the primary physiologic problem.
Dogs with pulmonary edema are assessed for improvements in respiratory status and evidence of excessive fluid removal or impaired renal function.
Dogs with low-output failure require close assessment of blood pressure, perfusion, and cardiac rhythm.
Dogs receiving antiarrhythmic medications require ECG monitoring to assess rhythm response and recognize additional electrical abnormalities.
The duration and intensity of hospitalization depend on clinical stability, treatment response, and the underlying disease.
Common complications
Recurrent pulmonary edema
Pulmonary edema can recur in dogs with underlying congestive heart failure.
Recurrence reflects continued difficulty controlling cardiac congestion and may require adjustment of diuretic treatment and other cardiac medications.
Published evidence indicates that pimobendan reduces recurrence of pulmonary edema in dogs with mitral valve disease.
Renal dysfunction during diuretic treatment
Furosemide promotes fluid removal, but the effect of diuresis must be balanced against kidney function and circulating volume.
Renal laboratory values are monitored during treatment because changes may influence subsequent diuretic decisions.
Circulatory shock
Dogs with low-output heart failure may develop shock when poor cardiac contractility prevents adequate forward blood flow.
Clinical findings can include cold extremities, hypothermia, and decreased alertness.
Management may require medication to improve contractility while carefully controlling fluid accumulation.
Hypotension
Low blood pressure may result from poor cardiac output or occur during cardiovascular treatment.
Blood pressure monitoring is important because medications that reduce heart rate or affect circulation may worsen an already unstable patient.
Ventricular ectopy
Ventricular ectopy consists of abnormal electrical beats originating within the ventricles.
It is a particular concern in dogs receiving dobutamine for poor cardiac contractility and is identified through continuous ECG monitoring.
Development of ventricular ectopy may require reassessment of cardiovascular treatment.
Atrial fibrillation complicating congestive heart failure
Atrial fibrillation is associated with a worse prognosis when present alongside congestive heart failure.
Dogs with atrial fibrillation are also more likely to experience right-sided manifestations of heart failure and fluid accumulation within body cavities.
Rate control is important because excessively rapid ventricular contractions can interfere with adequate cardiac filling.
Digoxin toxicity
Digoxin has clinically important interactions and potential toxicity.
Hypokalemia increases susceptibility to digoxin toxicity. Drug concentrations, electrolyte abnormalities, and the development of new rhythm disturbances therefore influence monitoring and treatment decisions.
Antiarrhythmic medication adverse effects
Antiarrhythmic medications can affect heart rate, conduction, contractility, or blood pressure.
Diltiazem can produce serious cardiovascular effects if administered too rapidly.
Sotalol may be inappropriate in dogs with poor cardiac contractility.
Mexiletine can cause gastrointestinal adverse effects, including nausea, vomiting, and loss of appetite.
These effects can limit medication choices or require treatment modification.
Persistent or hemodynamically significant arrhythmias
Some ventricular arrhythmias persist despite treatment or become clinically significant because they reduce effective circulation.
Weakness, hypotension, and abnormal ECG features can indicate that an arrhythmia is interfering with cardiac function.
Persistent rhythm abnormalities may require additional antiarrhythmic treatment or electrical cardioversion.
Prognosis
The outlook for dogs experiencing cardiac emergencies depends on the underlying disease, the severity of circulatory or respiratory compromise, the presence of concurrent arrhythmias, and the response to stabilization.
A published study of 145 dogs and cats treated for acute congestive heart failure reported that 116 patients, approximately 80%, were discharged from the hospital. This describes a combined canine and feline study population and does not establish an equivalent survival rate for dogs alone or for every type of canine cardiac emergency.
Short-term outlook
Pulmonary edema and congestive heart failure can require substantial respiratory and cardiovascular support during the initial crisis.
Dogs that respond to oxygen, furosemide, and cardiac medication may achieve sufficient respiratory stability to leave the hospital. The underlying cardiac disease and treatment response influence the likelihood of stabilization.
Low-output heart failure is particularly concerning when poor contractility produces shock. These dogs may have inadequate circulation at the same time they are experiencing congestion, complicating treatment decisions.
Dogs with significant arrhythmias have different short-term risks depending on whether the rhythm reduces blood pressure or cardiac output.
An isolated ventricular premature complex or a well-tolerated accelerated idioventricular rhythm does not carry the same immediate clinical significance as sustained ventricular tachycardia associated with weakness or hypotension.
Factors affecting prognosis
Cardiac contractility. Poor contractility can limit blood flow, cause shock, and restrict which cardiac medications can be used safely.
Concurrent atrial fibrillation. Atrial fibrillation worsens the prognosis of dogs with congestive heart failure and is associated with a greater likelihood of right-sided heart failure manifestations and effusions.
Underlying systemic disease. Arrhythmias associated with sepsis, shock, electrolyte abnormalities, or other systemic illness require management of the underlying condition. Rhythm treatment alone may not address the initiating problem.
Response to initial treatment. Improvements in respiratory effort, circulation, and cardiac rhythm provide important evidence of stabilization.
Medication tolerance. Kidney function, blood pressure, electrolyte balance, and cardiac contractility may limit treatment choices.
Nature of the underlying cardiac disease. Progressive structural cardiac disease may require different ongoing management than an arrhythmia associated with a correctable systemic disturbance.
Recovery following congestive heart failure
Dogs recovering from pulmonary edema may require ongoing furosemide and pimobendan treatment.
Follow-up kidney function assessment and echocardiography are important parts of evaluating recovery and continuing cardiac management.
Some dogs whose congestive episode was precipitated by corticosteroids may subsequently do well with little or no long-term medication. This possibility depends on the underlying disease and should not be interpreted as the expected course for all dogs with CHF.
Recurrence and long-term management
Recurrent pulmonary edema remains a concern in dogs with underlying heart failure.
Published evidence indicates that pimobendan treatment in dogs with mitral valve disease reduces recurrence of pulmonary edema.
Torsemide is another diuretic option, with evidence suggesting it is not inferior to furosemide for controlling clinical signs and may provide benefits in preventing worsening heart failure or death. Torsemide may also be associated with substantially greater urination and thirst.
Long-term outlook for arrhythmias
The long-term course of an arrhythmia depends on its cause and whether it can be controlled.
Dogs with primary conduction abnormalities may require ongoing antiarrhythmic treatment or an intervention such as catheter ablation.
Dogs with severe atrioventricular conduction disease that does not respond to atropine may require a pacemaker.
Atrial fibrillation commonly requires continued heart-rate management, particularly when significant structural cardiac disease is present.
Dogs with ventricular arrhythmias may require ongoing medications such as sotalol or mexiletine, with treatment determined by cardiac function, rhythm characteristics, medication tolerance, and underlying disease.
Overall long-term survival estimates are not available for all forms of canine arrhythmia or low-output heart failure.