Physiology Flashcards
Heart failure (HF)
Inability of the heart to pump blood out into the systemic
circulation (cardiac output) at a level proportional to the body’s metabolic needs.
Cardiac fatigue
A temporary decrease in the heart’s ability to maintain normal function during or after prolonged exercise. (Transient Myocardial Dysfunction)
Why does cardiac fatigue occur?
- Due to prolonged aerobic exercise
- Supra-physiological stress
(homeostasis disturbance) - Prolonged pressure & volume overload
- Substrate depletion
What is the other name used for acute heart failure?
De Novo Heart Failure
What are the possible pathophysiological causes of acute heart failure?
- Biomarkers increased (NT-proBNP)
- Structural underlying pathology (cardiomyopathy, valve problems) *
- Inflammation (Myocarditis)
- Cardiac overload (high blood pressure, heat + exercise, high hematocrit)
- Hyponatremia (low levels of sodium / higher amount of water in the body)
What are the main characteristics of left-sided heart failure?
- Weakened left ventricle that cannot eject the blood efficiently into systemic circulation.
- Decreased ejection fraction.
- Blood backing to pulmonary circulation.
What are the main characteristics of right-sided heart failure?
- Weakened right ventricle that cannot eject the blood efficiently into pulmonary circulation.
- Preserved or slightly increased ejection fraction.
- Blood backing to systemic circulation (body).
Common compensations of left and right-sided HF
- Tachycardia (increased heart rate).
- Pallor.
- Secondary polycythemia (overproduction of red blood cells, leading to increased viscosity of the blood).
- Daytime oliguria (low urinary output) due to reduced blood flow to the kidney.
Common backup effects of right-sided HF
- Peripheral oedema.
- Hepatomegaly (enlargement of the liver).
- Splenomegaly (enlargement of the spleen due to reduced blood flow).
- Ascites (accumulation of fluid in the abdomen area).
- Distended neck veins.
Common backup effects of left-sided HF
- Orthopnea (difficulty breathing lying flat).
- Cough producing white or pink tinged phlegm (due to the presence of blood, indicating that small blood vessels in the lungs may be leaking).
- Shortness of breath.
- Paroxysmal nocturnal dyspnea (sudden shortness of breath that awakens a person from sleep).
- Hemoptysis (coughing up blood).
What are the most important clinical signs of heart failure?
- Exercise intolerance.
- Dyspnea on exertion.
Explain the Class I NYHA
- NO limitation of physical activity.
- Ordinary physical activity DOES NOT cause undue fatigue, palpitation, dyspnea (shortness of breath).
Explain the Class II NYHA
- SLIGHT limitation of physical activity.
- Comfortable at rest.
- Ordinary physical activity results in fatigue, palpitation, dyspnea (shortness of breath).
Explain the Class III NYHA
- MARKED limitation of physical activity.
- Comfortable at rest.
- Less than ordinary activity causes fatigue, palpitation, or dyspnea.
Explain the Class VI NYHA
- UNABLE to carry on any physical activity without discomfort.
- Symptoms of heart failure at rest.
- If any physical activity is undertaken, discomfort increases.
Signs and symptoms HR
- Change in fatigue level or dyspnea
- Paroxysmal nocturnal dyspnea (severe shortness of breath and cough that usually occurs at night).
- Orthopnea (dyspnea that occurs when lying flat).
- Dyspnea with fluid retention in the form of peripheral oedema or significant weight gain.
DECOMPENSATION signs
- Weight gain 1,5 -2 kg in 2-3 days.
- Increase in shortness of breath.
- Palpitations, tachycardia.
- Cognitive impairment.
Decompensation
Occurs when the heart’s ability to compensate for its reduced pumping function is overwhelmed, leading to a worsening of symptoms and signs of heart failure.
Decompensated heart failure is often characterized by a sudden deterioration in the patient’s clinical status.
What are the signs of ISCHEMIA during exercise?
- Drop of blood pressure (cave: not always, sometimes extreme hypertension occurs).
- Fatigue not matching the effort.
- Shortness of breath not matching the effort.
- Chest pain.
- Fast heart rate, weak pulse, increasing irregularities.
BNP levels
- BNP levels (>100 mg/dL can be a sensitive index of decompensated HF).
- Protein in the blood that tells hows hard the heart is working.
What are the 2 main pathophysiological causes of heart failure?
- Structural abnormalities.
- Failure of the compensatory mechanisms.
Explain the negative effect on CO:
Muscle loss ➔ Contractility ➔ Ejection fraction
After a heart attack, a portion of the heart muscle may be damaged or lost (infarcted). The affected area may not contract normally, leading to a decrease in contractility. The reduction in contractility contributes to a decrease in ejection fraction, which is the percentage of blood ejected from the heart with each contraction. A lower ejection fraction means the heart pumps out less blood per beat.
Explain the negative effect on CO:
Scar tissue ➔ Stiffness ➔ Ejection fraction
Scar tissue forms in the area of the infarction as part of the healing process. Scar tissue is less elastic and more rigid than healthy heart muscle.
The stiffness of the scar tissue affects the heart’s ability to contract and relax properly, leading to reduced compliance. This stiffness contributes to a decrease in ejection fraction, as the heart has difficulty pumping blood effectively.
Explain the negative effect on CO:
Conduction system
The electrical conduction system of the heart may be affected by the infarction. Damaged or compromised conduction pathways can lead to arrhythmias (abnormal heart rhythms) that further impact the coordination of heart contractions.
Arrhythmias can disrupt the synchronised pumping of the heart chambers, affecting cardiac output.
Explain the negative effect on CO:
Dyskinesia ventricular wall during contraction
Dyskinesia refers to abnormal movement. In the context of a heart attack, the affected portion of the ventricular wall may exhibit abnormal contractions during systole (contraction phase).
Dyskinesia can lead to inefficient pumping and a decrease in the overall effectiveness of the heart’s contractions, contributing to a reduction in cardiac output.
Explain the negative effect on CO:
Damage papillary muscle ➔ Valve leakage
The papillary muscles are responsible for anchoring the heart valves (particularly the mitral valve). If these muscles are damaged during a heart attack, the valves may not close properly.
Valve leakage, known as regurgitation, can occur, allowing blood to flow backward during the cardiac cycle. This leads to a decrease in forward blood flow and a reduction in cardiac output.
Explain the negative effect on CO:
Dilation ➔ Valve leakage
Dilation refers to the enlargement of the heart chambers, often as a compensatory response to reduced contractility or increased workload.
As the heart chambers dilate, the valve leaflets may not come together properly, leading to valve leakage and regurgitation.
What are the 3 causes of cardiomyopathy?
- Genetic.
- Ischemic.
- Enduring pressure or volume overload.
How does enduring pressure or volume overload lead to cardiomyopathy?
Due to years of hypertension or valve leakage or extreme volume aerobic exercise, ‘adverse remodelling’ takes place (hypertrophy and/or dilation).
How do genetic mutations lead to cardiomyopathy?
Gene mutations cause morphological and structural abnormalities that eventually lead to heart failure.
How does ischemia lead to cardiomyopathy?
Insufficient oxygen and nutrients initiate changes at the cellular level that cause the heart muscle to weaken and eventually dilate. This is an ischemic cardiomyopathy.
What are the normal values of EDL, ESV, EF and SV?
- End-diastolic volume (EDV): 120 mL.
- End-systolic volume (ESV): 55 mL.
- Ejection fraction (EF): 65 mL.
- Stroke volume (SV): 55%