All Animal Cardiac Diseases

Canine Dilated Cardiomyopathy: Path

Definition: A primary myocardial disease characterized by cardiac enlargement and impaired systolic function.

The breeds prone to develop DCM are mainly large breed dogs: Doberman, Irish Wolfhound, Great Dane, St. Bernard, Newfoundland, Leonberger, Boxer, Giant Schnauzer, Cocker Spaniel, Flat Coat Retriever.

Canine Dilated Cardiomyopathy: Clinical Signs

Early signs include:

1. Fainting, lethargy, exercise intolerance.

2. Many dogs are asymptomatic until they suddenly have symptoms associated with heart failure; onset of symptoms may be extremely rapid (a few days).

Signs of heart failure

1. Respiratory distress from left-sided congestive heart failure.

2. Abdominal distention from ascites from right-sided congestive heart failure.

Canine Dilated Cardiomyopathy: Diagnosis

• Made based on echocardiography which should be performed if there is clinical suspicion based on clinical signs, auscultation, and radiographic findings.

• Echocardiogram will show predominantly systolic cardiac dysfunction (poor contractility and shortening fraction).

Canine Dilated Cardiomyopathy: Treatment

Treatment of subclinical dogs (controversial; you are less likely to be asked about this).

1. Some cardiologists recommend ACE inhibitors and/or pimobendan for dogs with early stage cardiac dilatation.

2. For dogs with arrhythmias, therapy should be instituted.

   1. For ventricular tachycardia (especially in Boxers and Dobermans), options include sotalol, amiodarone, mexilitine, and very low dose atenolol.

Canine Familial Arrhythmic Cardiomyopathy: Path + C.S

a.k.a. Arrythmogenic Right Ventricular Cardiomyopathy - ARVC

This disease appears to be an autosomal dominant trait, primarily of Boxer dogs, of variable penetrance ranging from mild to severe forms. As the name implies, VPCs occur and when severe,

can cause sudden cardiac death, even at a young age. Major clinical sign is syncope.

Canine Familial Arrhythmic Cardiomyopathy:D.X

• Diagnosis typically requires a 24 hour Holter monitor to assess the severity and response to treatment because a brief ECG may dramatically overestimate or underestimate the frequency of VPCs due to their intermittent nature.

Canine Familial Arrhythmic Cardiomyopathy:T.X

The disease can be classified with 3 levels of severity:

1. Asymptomatic dogs with VPCs

   1. While strict diagnostic criteria do not exist, >100 VPCs per 24 hours or runs of couplets, triplets, or

   2. ventricular tachycardia is consistent with disease and >1000 VPCs per 24 hours, runs of ventricular tachycardia, or evidence of R on T warrant treatment.

2. Symptomatic dogs (dogs with syncope)

   1. Two options are sotalol or the combination of mexilitine and atenolol

      1. If a poor response is seen with one option, the other may be more effective

3. Dogs with systolic dysfunction and heart failure.

   1. Should be treated as dogs with DCM

   2. Also, some cardiologists advocate supplementing L-carnitine.

Commonly Used Cardiovascular Medications in Small Animal General Practice

Amlodipine

1. Brand Name: Norvasc

2. Drug class/Use: Calcium channel blocking agent/vasodilator

3. MOA: Inhibits calcium entry into smooth muscle

4. Route: PO

5. Common Indications: Used to tx systemic hypertension

6. Special Considerations: Monitor for signs of hypotension and bradycardia

Enalapril

1. Brand Name: Vasotec, Enacard

2. Drug class/Use: Angiotensin-converting enzyme (ACE) inhibitor

3. MOA: Blocks angiotensin II formation causing vasodilation of glomerular efferent arterioles, decreased intraglomerular pressure and decreased GFR

4. Route: PO

5. Common Indications: Commonly used as a vasodilator

   • Used in congestive heart failure cases

   • Used for treatment of systemic hypertension

   Can also be used in the treatment of CRF and PLN

6. Special Considerations: Monitor for signs of hypotension, monitor blood work regularly for renal fx and electrolytes

Furosemide

1. Brand Name: Lasix

2. Drug class/Use: Loop diuretic

3. MOA: Acts in the thick ascending loop of henle to inhibit reabsorption of NA and CL

4. Route: PO and IV

5. Common Indications: Commonly Used diurectic

   1. Used in chf or oliguria/anuria

6. Special Considerations: Can cause fluid and electrolyte changes and azotemia

   1. Monitor hydration status and blood work values closely

   2. Clinical Tip: advise owners that pets will likely urinate more often. Ensure that pets have access to fresh water at all times.

Lidocaine

1. Brand Name: Xylocaine

2. Drug class/Use: Antiarrhythmic, Non - cardiac related use: Local anesthetic

1. MOA: Binds to and inhibits voltage-gated sodium channels

2. Route: IV, regional infusion

3. Common Indications: Used for ventricular tachyarrhythmias

4. Non - cardiac related indication: Used to help with analgesia

5. Special Considerations: Use cautiously in hepatic disease

6. Decreased efficacy with hypokalemia

Pimobendan

1. Brand Name: Vetmedin

2. Drug class/Use: Inotropic drug with vasodilatory properties

3. MOA: Calcium sensitizer and selective inhibitor of phosphodiesterase 3 (PDE3)

4. Route: PO

5. Common Indications: Used as adjunctive therapy in congestive heart failure cases

   • CHF secondary to DCM

   • CHF due to mitral valve disease

6. Special Considerations: Not FDA approved in cats

   Contraindicated in HCM cases

   Use with caution in arrhythmia cases

Spironolactone

1. Brand Name: Aldactone

2. Drug class/Use: Aldosterone competitive antagonist

3. MOA: Competitively inhibits aldosterone at the level of the distal renal tubules

4. Route:

5. Common Indications:

6. Special Considerations:

Heartworm (Dirofilariasis) in Dogs and Cats

Heartworm disease in dogs is a common disease that is likely to appear on board exams. It is less common in cats but has some important differences that you should know about, time permitting. This PowerPage discusses the life cycle of Dirofilaria immitis and the signs it causes in dogs and cats as well as treatment and prevention methods.

Key Points

• Lifecycle of Dirofilaria and transmission depend on mosquito

• Heartworm antigen test is effective in dogs but not all cats

• Treatment with melarsomine in dogs must be done carefully to avoid problems

• Preventions with monthly ivermectin is recommended

Relevant Pathophysiology

Adult Dirofilaria worms can be 15-30 cm long and can live 3-5 years. They reside in the pulmonary artery and right ventricle. This results in right ventricular hypertrophy. The worms are transmitted as L3 larvae through mosquito bites. Dogs develop much higher worm burdens than cats. In recent years, the bacteria, Wohlbachia has been identified in heartworms.

Clinical SignsDogs

• Signs may be consistent with right heart failure

  1. Exercise intolerance, cough, dyspnea, ascites

Cats

2 presentations of heartworm

• Acute (due to worms dying and resulting embolism/inflammation)

  1. Salivation

  2. Tachycardia

  3. Shock

  4. Hemoptysis

  5. Neurologic signs

  6. Acutely dying

• Chronic

  1. HARD (Heartworm associated respiratory disease) is a syndrome in cats that appears similar to asthma (coughing, wheezing) but occurs secondary to heartworm infestation

  2. Cough, dyspnea, exercise intolerance

  3. Vomiting, anorexia, weight loss

DiagnosisDogs

• Heartworm antigen test is the test of choice

  1. Detects Ag from adult female worms

• Modified Knott’s test may detect microfilaria (less sensitive than antigen test)

• Other diagnostic findings may include:

  1. Right sided cardiac enlargement on thoracic radiographs (reverse D appearance), enlarged pulmonary arteries

  2. Proteinuria

  3. Eosinophilia

Cats

• Heartworm antigen test has false negatives from low worm burden or all male infections

• Heartworm antibody test indicates exposure but not necessarily infection

• Thoracic radiographs and/or echocardiography can provide a diagnosis in some cases

NOTE: On echocardiogram, heartworms appear as a distinct “double lined echodensity”

TreatmentDogs

• The treatment of choice for dogs with heartworm is melarsomine.

  1. Currently, no matter the disease stage, the American Heartworm Society recommends the split protocol for adulticide therapy.

     1. A single injection followed in 4-6 weeks by 2 injections 24 hours apart

     2. There is a low risk of thromboembolic disease, and confinement. helps to minimize this.

• Wohlbachia, the bacteria found in heartworm, can be readily treated with doxycyline, azithromycin, or rifampin, which may enhance effectiveness of heartworm treatment.

• An alternative to treatment with melarsomine is the use of monthly heartworm preventative and waiting for adults to die. This is not currently recommended by the American Heartworm Society.

• Other historical treatments include thiacetarsamide and levamisole.

Cats

• Cats do not tolerate melarsomine well.

• Treatment is usually symptomatic with a heartworm preventative, bronchodilators and/or corticosteroids until the worms die (2-3 year life span in cats).

Prevention

Several options are available and effective for heartworm prevention in dogs and cats including:

• Oral

  1. Ivermectin (Heartgard^TM)

  2. Milbemycin (Sentinel^TM)

• Topical

  1. Selamectin (Revolution^TM)

  2. Moxidectin and imidacloprid (Advantage Multi^TM)

Pericardial Effusion

Pericardial effusion is an uncommon but life-threatening clinical condition reported in various species in which the pericardial space is filled with excessive fluid. Subsequently, cardiac function can be compromised and result in decreased or inadequate cardiac output. This PowerPage will cover the basic principles, common causes, and treatment of pericardial effusion.

Key Points

• In health, only a small amount of fluid is present within the pericardial space

• Clinical signs of pericardial effusion arise when the pericardial space becomes filled with excessive amounts of fluid.

  1. The amount of fluid and rate at which the space fills with fluid will dictate the onset, severity and extent of clinical signs (rapid filling of pericardial space will result in more severe and acute clinical signs, whereas slow and progressive filling may result in more subtle signs as the heart is able to compensate over time).

• There are numerous causes of pericardial effusion, depending on the species.

• Cardiac tamponade develops when the intrapericardial pressure equals or exceeds right atrial pressure resulting in cardiovascular and hemodynamic compromise.

• Pericardiocentesis may have to be performed as an emergency and life-saving procedure and/or as a diagnostic procedure to evaluate the pericardial fluid.

Pathogenesis

• In health, the pericardium consists of the outermost fibrous pericardium and the parietal and visceral layers of the serous pericardium.

  1. The pericardial space resides between the parietal and visceral layers of the serous pericardium

• Normally, a minute amount of fluid is present within the pericardial space; pathologic pericardial effusion occurs when abnormal amounts of fluid accumulate within the pericardial space

• As fluid accumulates, the ability of the pericardium to stretch is exceeded, the volume and pressure within the pericardial space continues to increase, and cardiac function is compromised secondary to decreased diastolic filling.

• Cardiac tamponade, a form of cardiogenic shock, develops when the intrapericardial pressure equals or exceeds right atrial pressure.

  1. Cardiac tamponade causes impairment of:

     1. Venous return

     2. Ventricular filling

     3. Stroke volume

     4. Cardiac output

  2. The volume of fluid necessary to cause cardiac tamponade depends of fluid accumulation.

Differential Diagnosis for Causes of Pericardial Effusion

• Causes of pericardial effusion (by species) include:

  1. Dogs:

     1. Cardiac neoplasm:

        • Hemangiosarcoma (most common neoplastic cause of pericardial effusion)

        • Chemodectoma

        • Mesothelioma

        • Lymphosarcoma

        • Thyroid carcinoma

     2. Right-sided heart failure

     3. Atrial rupture

     4. Coagulopathy (rodenticide toxicity)

     5. Bacterial infections

     6. Idiopathic pericardial effusion

  2. Cats:

     1. Congestive heart failure

     2. Feline infectious peritonitis

     3. Cardiac neoplasm

        • Lymphosarcoma (most common neoplasm of heart)

        • Carcinomas

        • Hemangiosarcoma

        • Aortic body tumors

        • Fibrosarcomas

  3. Horse:

     1. Extension of viral infection (i.e. equine viral arteritis, equine influenza)

     2. Septicemia

     3. Extension of bacterial infection from lung

     4. Neoplasia

     5. Idiopathic (most common)

  4. Cattle:

     1. Ingestion and penetration of a foreign object (Traumatic reticuloperitonitis/traumatic pericarditis or Hardware disease).

        • Ingestion of a foreign object may settle in the reticulum; subsequently, the object may penetrate the reticulum and cause localized or generalized peritonitis.

          1. If the pericardium and/or myocardium, which lies just cranial to the reticulum, are penetrated by the foreign body, pericarditis and pericardial effusion may develop.

        • Extension of bacterial or viral infections of lungs.

Clinical Signs

• Non-specific signs may be present including:

  1. Fever, anorexia, depression weight loss

  2. Dyspnea

  3. Abdominal distension (small animals)

  4. Peripheral edema (large animals)

  5. Colic (horses)

• Attenuated heart sounds (muffled from effusion around heart)

• Jugular vein distension (from increased right atrial pressure)

• Poor peripheral pulse quality

• Elevated heart and respiratory rate

• Hepatomegaly and ascites possible

Diagnosis

• Clinicopathologic Findings

  1. Anemia (secondary to blood loss or chronic disease)

  2. Elevations in coagulation parameters (if effusion related to rodenticide toxicity)

  3. Pre-renal azotemia and non-specific electrolyte abnormalities.

  4. Pulsus paradoxus

     1. Exaggeration of the normal inspiratory decrease in systolic blood pressure

• Radiography

  1. Small animals – thoracic radiography may demonstrate:

     1. Enlargement of cardiac silhouette (rounded appearance).

     2. Pleural effusion and enlargement of the caudal vena cava.

     3. Hepatomegaly or decreased abdominal detail (from ascites) may be observed.

• Electrocardiography

  1. Sinus tachycardia

  2. Ventricular premature contractions

  3. Low voltage QRS complexes may be seen

     1. Electrical alternans

        • Pattern of alternating variation in R-wave amplitude.

• Echocardiography

  1. “Gold standard’ for diagnosing pericardial effusion

  2. Appears as anechoic fluid in pericardial space

• Pericardiocentesis

  1. Rarely may detect neoplastic cells if neoplasia is the primary cause of pericardial effusion.

  2. Fluid is frequently hemorrhagic.

Treatment

• Small Animals:

  1. Pericardiocentesis

     1. Should be implemented immediately if cardiac tamponade is present.

     2. Complications can include ventricular premature complexes, laceration of the coronary artery, and sudden death.

  2. Chemotherapy

     1. If underlying cause of effusion is a treatable neoplasm.

  3. Pericardiectomy

     1. Treatment of choice for idiopathic pericardial effusion.

• Horses:

  1. Idiopathic cases can be treated with placement of an indwelling chest tube into pericardial sac and subsequent drainage and lavage of the pericardial space followed by local infusion of antimicrobials.

• Cattle:

  1. Treatment of traumatic reticuloperitonitis involving the heart is typically unrewarding and is directed at salvage or short-term survival.

  2. Repeated pericardial drainage and lavage can be implemented for short-term management.

Canine Visceral + SubQ Hemangiosarcoma

Canine Hemangiosarcoma

Hemangiosarcoma (HSA) is a malignancy of endothelial cells that normally line blood vessels. It can develop any place in the body that has blood vessels, but most commonly occurs in the spleen of dogs. Another form of the disease is the cutaneous form, which is induced by ultraviolet radiation from the sun. Because of the biological differences between the cutaneous and visceral forms of the disease, we will discuss each of them separately in this PowerPage.

Visceral and Subcutaneous Hemangiosarcoma Key Points

• Most commonly affects large breed dogs such as German Shepherd Dogs, Golden Retrievers, Labrador Retrievers, etc.

  1. Most commonly affected organ is the spleen

     1. Other commonly affected organs include the right atrium (auricle), liver, retroperitoneal space, subcutaneous tissue.

• The most common tumor to metastasize to the brain

• Often present through emergency for acute hemoabdomen and hypovolemic shock, or pericardial. effusion and cardiogenic shock.

  1. May have history of “good days” and “bad days” associated with small bouts of internal hemorrhaging and re-absorption of the blood.

• Highly metastatic via blood vessels and direct contact seeding within the abdomen if tumor ruptures.

• Median survival times generally do not exceed 1 year, regardless of treatment.

Diagnostics

• Abdominal ultrasound

  1. HSA often appears cavitary and fluid-filled

  2. To identify free abdominal fluid, primary and metastatic lesions, especially in the liver, lymph nodes, and serosal surfaces.

• Fine needle aspirate cytology

  1. Often unrewarding as samples are often filled with blood and the tumor is poorly exfoliative.

• Surgical biopsy

  1. Splenectomy recommended for suspected splenic lesions or for those with a chance of rupturing (cavitary, large, fluid-filled).

  2. Incisional biopsies (Tru-cut, punch biopsy, etc.) that do not remove the entire tumor run the risk of hemorrhage.

• Thoracic radiographs

  1. To identify pulmonary metastasis and pericardial effusion.

• Cardiac ultrasound

  1. Sensitivity for finding cardiac masses is questionable unless effusion is present

• CT or MRI

  1. Often recommended for surgical planning for HSA affecting the subcutaneous space or retroperitoneal space.

• CBC, chemistry panel, urinalysis

  1. Common findings: anemia (with or without regenerative response), thrombocytopenia, presence of schistocytes.

• Coagulation panel

  1. Prolonged clotting times if in disseminated intravascular coagulation (DIC).

  2. Rule out rodenticide toxicity for questionable cases of hemoabdomen.

Treatment

• Resuscitate and stabilize with IV fluids and blood products as necessary for hemoabdomen.

• Exploratory surgery to remove the primary tumor and biopsy abnormal tissues.

• Adriamycin-based chemotherapy to help delay development of metastasis and prolonged survival.

Prognosis

Prognosis of the splenic form depends on the stage of the disease and whether or not Adriamycin is administered:

• Surgery alone: median survival time 3 weeks-3 months

• Stage I – single lesion without hemorrhage and treated with surgery and Adriamycin-based chemotherapy: 9 months.

• Stage II – single lesion with hemorrhage and treated with surgery and Adriamycin- based chemotherapy: 5-6 months.

• Stage III – metastasis present treated with Adriamycin chemotherapy: 3.5 months.

Feline HCM

most commonly associated with aortic thromboembolism (saddle thrombus) in cats

The correct answer is hypertrophic cardiomyopathy. This disease tends to lead to dilation of the left atrium with blood stasis in the chamber. Thrombi form there and frequently lodge at the bifurcation of the aorta, leading to acute paraparesis and pain.

It is frequently caused by hyperthyroidism