Advanced Veterinary Nursing: Cardiovascular & Circulatory System Disorders

Session Objectives

  • LO2 - Appraise the impact and effects of a range of diseases and disorders on body systems
  • By the end of the session, you should be able to:
    • Define terms associated with abnormalities of the circulatory system
    • Describe possible causes, clinical signs, treatment and diagnostic tests for congenital or acquired heart disease
    • Describe possible causes, clinical signs, treatment, diagnostic tests and nursing care for heart failure

Terms Associated with Functional Abnormalities

  • Myocarditis: Inflammation of the myocardium.
  • Pericarditis: Inflammation of the pericardium.
  • Cardiomyopathy: Degeneration of the heart muscles.
  • Bradycardia: Slow heart rate.
  • Endocardiosis: Thickening of the heart valves.
  • Endocarditis: Infection of the endocardium.
  • Tachycardia: Fast heart rate.
  • Cardiac tamponade: Compression of the heart due to pericardial effusion.

Congenital Heart Diseases

Patent Ductus Arteriosus (PDA)

  • Most common congenital heart defect in dogs (GSD, Collies, Poodles).
  • The ductus arteriosus (embryonic duct) connects the pulmonary artery and aorta (enabling blood to bypass the lungs) remains patent.
  • Results in the shunting of blood from the aorta into the pulmonary artery therefore diminishing cardiac output to the rest of the body leading to left sided heart failure.
  • Clinical signs:
    • Depends on extent of shunting
  • Treatment:
    • Surgery to ligate the duct.
  • Prognosis is good following surgery.

Aortic or Pulmonic Stenosis

  • Narrowing of the aortic or pulmonary valve, which obstructs the flow of blood leaving the ventricle.
  • Leads to hypertrophy of the ventricle as the heart tries to maintain cardiac output.
  • Clinical signs:
    • A murmur is likely to be detected on auscultation.
    • Exercise intolerance, syncope, heart failure, collapse, sudden death.
  • Treatment:
    • Surgery to dilate pulmonary artery using a balloon (balloon valvuloplasty).

Ventricular/Atrial Septal Defects

  • A hole exists in the septum between the right and left ventricles/atria allowing blood to pass from one side to the other.
  • Ventricular septal defects are the most common congenital defects in cats.
  • Clinical signs:
    • A murmur may be detected on auscultation.
    • Asymptomatic or congestive heart failure.
  • Treatment:
    • Surgery to correct large defects.
    • Symptomatic treatment for heart failure.

Persistent Right Aortic Arch (PRAA)

  • The oesophagus is trapped between the ligamentum arteriosus, aorta, pulmonary artery, and heart base.
  • Clinical signs:
    • Stunted growth, megaoesophagus, regurgitation of food, aspiration pneumonia.
  • Treatment:
    • Surgery to cut the ligamentum arteriosus.
    • Elevated feeding if megaoesophagus.

Tetralogy of Fallot

  • This is the combination of ventricular septal defect, pulmonic stenosis, compensatory right-sided hypertrophy and an overriding aorta.
  • Prognosis is very guarded.
  • Four components:
    1. Ventricular septal defect
    2. Pulmonic stenosis
    3. Right-sided hypertrophy
    4. Overriding aorta

Acquired Heart Diseases

Endocardiosis

  • Chronic degeneration of the heart valves especially the mitral valve leaving them thickened and nodular.
  • This causes blood to regurgitate into the atria, increasing their workload causing congestion and heart failure.
  • Common in dogs (CKCS) but rare in cats.
  • Clinical signs:
    • A murmur is detected on auscultation.
    • Can progress to left or right-sided heart failure.
  • Treatment:
    • Symptomatic treatment for left or right-sided heart failure.

Endocarditis

  • Inflammation of the endocardium caused by bacterial infection which travels to the heart via blood.
  • Clinical signs:
    • Pyrexia, lethargy, anorexia, shifting lameness, murmur
  • Treatment:
    • Broad-spectrum antibiotics.

Dilated Cardiomyopathy (DCM)

  • The myocardium becomes thinner and loses its ability to contract efficiently causing the heart to become enlarged.
  • Mainly seen in large/giant breeds e.g. Dobermann Pinschers, Boxers, Great Danes, Irish Wolfhounds, Newfoundlands.
  • In cats, can be the result of either taurine deficiency or idiopathic.
  • Clinical signs:
    • Anorexia, weight loss, reduced exercise tolerance, lethargy, sudden death.
    • Signs of left-sided heart failure (+/- right)
  • Treatment:
    • Symptomatic treatment for heart failure.
    • Correct taurine deficiency in cats.

Hypertrophic Cardiomyopathy (HCM)

  • The myocardium becomes thicker which leads to reduced myocardial relaxation, inadequate cardiac output and heart failure.
  • Can be the result of hypertension, hyperthyroidism or idiopathic.
  • More common in small breeds of dogs and cats.
  • Clinical signs:
    • Asymptomatic or if in heart failure (dyspnoea, tachypnoea, tachycardia, murmur)
    • Common complication is aortic thromboembolism.
  • Treatment:
    • Treat underlying cause.
    • Symptomatic treatment for heart failure.

Pericardial Effusion

  • The accumulation of fluid in the pericardial sac.
  • Cardiac tamponade.
  • Clinical signs:
    • Lethargy, muffled heart sounds, tachycardia, pale mucous membranes, exercise intolerance, collapse, signs of heart failure.
  • Treatment:
    • Pericardiocentesis.

Heart Failure

  • The heart is unable to maintain an adequate circulation causing a reduction in cardiac output and the development of heart failure.
  • Blood pools in the lungs or body tissues (congestion).
  • The location of the congestion depends upon which side of the heart is failing.
  • Causes:
    • Myocardial disease - HCM or DCM
    • Pressure overload
    • Volume overload
    • Mechanical problems

Clinical Signs

  • Acute:
    • Collapse, slow CRT, weak pulse, severe dyspnoea, cyanosis or pallor mucous membranes
  • General:
    • Tachycardia, weak pulse, tachypnoea, dyspnoea, murmur, dysrhythmias, exercise intolerance, lethargy
  • Right-sided heart failure:
    • The right ventricle of the heart is too weak to pump enough blood to the lungs. This causes blood to build up in the veins (the blood vessels that carry blood from the organs and tissue back to the heart). The increased pressure inside the veins can push fluid out of the veins into surrounding tissue. This leads to a build-up of fluid in body tissues.
  • Left-sided heart failure:
    • The left ventricle of the heart no longer pumps enough blood around the body. As a result, blood builds up in the pulmonary veins (the blood vessels that carry blood away from the lungs). This causes shortness of breath, trouble breathing or coughing – especially during physical activity.
    • Left-sided heart failure is the most common type.

Diagnostic Procedures

  • History and a full physical examination
  • Blood tests for routine biochemistry or culture
  • Fluid sample for culture and cytology
  • Blood pressure
  • Thoracic radiographs
  • Echocardiography
  • Electrocardiogram
Echocardiography
  • Ultrasound examination of the heart to assess the structure and function of the heart.
  • The thickness and contractility of the ventricular walls and septum can be assessed.
  • Abnormal soft tissue masses and pericardial effusions can be seen.
  • Cardiac tamponade is caused by the accumulation of fluid in the pericardial space, resulting in reduced ventricular filling and compression of the heart.
Electrocardiogram (ECG)
  • An ECG measures the electrical activity of the heart.
  • It is used to diagnose arrhythmias.
  • Chamber enlargement can be detected when used in conjunction with other tests.

Treatment

  • Acute
    • CPR
    • Treat as an emergency
  • Chronic
    • Identify and treat underlying cause
    • Positive inotropes - increases contractions Vetmedin, Cardisure
    • Angiotensin converting enzyme (ACE) inhibitors - Lower Blood pressure, Vasodilation
      • Enacard, Fortekor, Nelio, Benefortin, Cardalis
    • Diuretics - Frusemide, Libeo
    • Beta blockers - Reduce heart rate, antiarrhythmic Sotalol, Propranolol (both off license, also act as an antiarrhythmic), Ventipulmin (equine)
    • Anti-arrhythmic drugs Hypercard for cats, Amiodarone (off license), lignocaine (IV, specific conditions, not routine)

Nursing Care

  • Acute
    • Monitor vital and clinical signs
    • Cage rest with minimal stress and movement
    • Administer drugs (fluids) as prescribed by the vet
    • Perform cardiopulmonary resuscitation (CPR)
  • Chronic
    • Monitor vital and clinical signs
    • Administer drugs as prescribed by the vet
    • Cage rest with minimal stress
    • Controlled exercise
    • Feed a low sodium diet or low calorie diet

Pro-BNP

  • Blood tests - Haematology and biochemistry to exclude other causes
  • Assess the hormone level called Brain natriuretic peptide (BNP) ; a protein that's a type of hormone. (BNP has brain in its name as that is where it was discovered)!
  • The heart makes and releases BNP into the bloodstream when it's working harder than normal to pump blood.
  • BNP dilates blood vessels which will cause kidneys to remove water and salt through urine faster, helping reduce the workload on the heart by lowering blood pressure and reducing the amount of blood the heart has to pump
  • N-terminal pro b-type natriuretic peptide (NT-proBNP) is a protein that forms part of BNP. Like BNP, the heart makes larger amounts of NT-proBNP when it has to work harder to pump blood.