Study Notes on Heart Structure and Disease

External Structures of the Heart

• Structure overview

  • Chordae tendineae:

  • Function: Prevents atrial prolapse for the valves.

  • Connection: Links to papillary muscles, which contract and pull on the chordae to keep valves closed during ventricular contraction.

  • Flow of blood through the heart:

  • Blood enters through the right atrium.

  • Passes to the tricuspid valve into the right ventricle.

  • Blood is then pumped into the pulmonary artery toward the lungs.

Evaluation for Cardiac Issues in Animals

• Key history questions for cardiogenic-related issues:

  • Exercise:

  • Assessment of activity levels.

  • Queries about exercise tolerance or changes in exercise habits (e.g., do they become fatigued more easily?).

  • Dietary Changes:

  • Inquiry about recent dietary changes, specifically grain-free diets.

  • Symptoms:

  • Presence of coughing (considered significant).

  • Noting any changes in breathing patterns (e.g., increased respiratory effort, dyspnea).

  • Observing for exercise intolerance (e.g., panting during activities).

  • Medical History:

  • Queries regarding previous diagnoses.

  • Current medications or any recent changes in medication regimen.

Physical Examination of the Cardiovascular System

• Components of the physical exam:

  • Auscultation:

  • Listening to heart sounds, noting any murmurs.

  • Pulse Examination:

  • Checking the pulse and heart rate; assessing for pulse deficits.

  • Blood Pressure Reading:

  • Taking blood pressure to assess overall cardiovascular health.

  • Mucous Membranes Exam:

  • Changes in the color of mucous membranes can indicate health issues (e.g., paleness relates to anemia or poor perfusion).

  • Lung Auscultation:

  • Listening to lung sounds as a complementary assessment to heart function.

Types of Heart Failure

• Overview of heart failure:

  • Definition: Insufficient blood flow for adequate oxygenation of tissues.

  • Types:

  • Left-Sided Heart Failure:

    • Fluid accumulation in the lungs (pulmonary congestion).

    • Significance of recognizing this condition.

  • Right-Sided Heart Failure:

    • Fluid accumulation in the abdomen (ascites).

  • Causes of Heart Failure:

  • Can result from either:

    • Myocardial failure: Heart muscle itself not functioning properly.

    • Circulatory failure: Issues within the circulatory system affecting blood flow.

Cardiomyopathies

• Definition: Diseases of heart muscle, grouped into different types:

  • Myocarditis and Taurine Deficiency discussed as variations.

• Circulatory failure issues:

  • Hypovolemia: Lack of sufficient blood volume will lead to heart failure.

  • Anemia:

  • Defined as decreased red blood cells or hemoglobin; both forms impact oxygen delivery and cardiac efficiency.

  • Valvular Dysfunction:

  • Conditions like mitral valve disease leading to heart murmurs.

  • Congenital Shunts or Defects in the heart, especially in younger animals.

Dilated Cardiomyopathy (DCM)

• Definition:

  • A condition characterized by dilation of all heart chambers.

• Commonly Affected Groups:

  • Large breed dogs, particularly male dogs (older, more predisposed).

• Clinical Signs:

  • Symptoms include:

  • Weakness

  • Exercise intolerance

  • Syncopal episodes (fainting)

  • Shock

  • Possible atrial fibrillation noted on EKG.

• Dietary Links:

  • Significant findings linking grain-free diets to DCM.

  • Observation that reintroducing grains can potentially reverse the condition.

Hypertrophic Cardiomyopathy (HCM)

• Definition:

  • Characterized by an increase in muscle mass of the left ventricle.

• Common Presentation:

  • More common in cats than in dogs; most prevalent cardiomyopathy in feline populations.

• Pathophysiology:

  • Hypertrophy leads to reduced blood flow due to obstruction during systole.

• Clinical Signs:

  • Symptoms include:

  • Fatigue

  • Cough

  • Increased heart and breathing rates

  • Possible murmurs, though not always present.

  • Potential risk of sudden death at any age.

• Heritability:

  • Condition is often heritable

Feline Dilated Cardiomyopathy (FDCM)

• Cause:

  • Often occurs secondary to taurine deficiency, less common now due to dietary awareness.

• Diagnosis:

  • Primarily diagnosed using echocardiogram as the gold standard.

Importance of Echocardiogram

• Recommended for:

  • Any suspected dilated or hypertrophic myopathies.

  • Sweeping structural view of the heart to assess for dilation and anomalies.

Handling Dyspneic Cats

• Precautions:

  • Special care required when handling cats exhibiting dyspnea (e.g., open mouth breathing).

  • Risk of exacerbating their condition; awareness is critical to prevent adverse outcomes during examination.