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Questions and Answers
What is a significant consequence of untreated GABHS infection?
Which of the following is NOT a proper treatment for GABHS infections?
According to the JONES criteria, how many major criteria must be present to confirm rheumatic fever?
Which test can be performed if a patient cannot recall a recent GABHS infection?
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What does the presence of 3 or more premature ventricular contractions (PVCs) in a row indicate?
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What layer of the heart is susceptible to infection and requires prophylactic medications for patients with metal implants or artificial valves?
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Which structure in the heart produces the primary pacemaker activity?
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What condition occurs when there is an excess amount of pericardial fluid compressing the heart?
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Which heart sound corresponds to the closure of the semilunar valves?
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What sound is produced when there is valvular insufficiency involving the AV valves?
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Where is the point of maximal impulse typically located?
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Which artery supplies blood to the left ventricle anteriorly?
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What triggers the heart to contract?
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What is the function of the coronary arteries?
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What causes the heart rate to increase under sympathetic nervous stimulation?
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Which of the following is a complication resulting from myocardial infarction?
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What represents the electrical system component responsible for relaying impulses to the ventricles?
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Which branch of the autonomic nervous system decreases heart rate?
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Study Notes
Anatomy of the Heart
- Heart is the vital pumping organ responsible for circulating blood throughout the body
- Normal heart rate ranges from 60 to 100 beats per minute (bpm)
- Heart pumps approximately 4-5 liters of blood per minute
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Factors influencing heart rate:
- Autonomic nervous system regulation:
- Sympathetic branch increases heart rate.
- Parasympathetic branch decreases heart rate.
- Autonomic nervous system regulation:
- Heart muscle contraction is triggered by electrical impulses traveling through the heart.
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Electrical system of the heart:
- Sinoatrial (SA) node: The primary pacemaker, generating 60 to 100 bpm.
- Atrioventricular (AV) node: Secondary pacemaker, producing 40 to 60 bpm.
- Bundle of His: Divides into left and right branches, transmitting electrical impulses to ventricles.
- Purkinje fibers: Distribute electrical impulses throughout the ventricle walls.
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Location:
- Located in the thoracic cavity, between the lungs and above the diaphragm, within the mediastinum.
- Heart is levorotatory (rotated slightly to the left).
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Parts of the heart:
- Base: The upper portion of the heart.
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Apex: The lower portion of the heart.
- Also known as the point of maximal impulse (PMI).
- Found in the 5th intercostal space.
- Critical for auscultation, as heart sounds are most audible here.
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Blood Supply to the Heart:
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Coronary arteries:
- Right coronary artery: Supplies blood to the right atrium and ventricle.
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Left coronary artery:
- Circumflex coronary artery: Supplies blood to the left atrium and posterior left ventricle.
- Left anterior descending (LAD) artery: Supplies blood to the anterior left ventricle.
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Coronary arteries:
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Muscle Layers:
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Endocardium: Innermost layer.
- Infection susceptible.
- Patients with metal implants or artificial valves require prophylactic antibiotics.
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Myocardium: Middle layer (heart muscle).
- Susceptible to infarction (heart attack).
- Reduced blood flow can lead to necrosis (tissue death) of this layer.
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Pericardium: Outer layer.
- Composed of two layers:
- Outer fibrous layer: Attaches the heart to the chest wall.
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Inner serous layer: Produces pericardial fluid to provide lubrication and prevent friction.
- Normal fluid volume: 30 milliliters (ml)
- Cardiac tamponade: Excess fluid accumulation in the pericardium (more than 30 ml) compresses the heart, hindering its contraction.
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Pericarditis: Inflammation of the pericardium, often with less than 30 ml of fluid.
- Can be diagnosed by listening for a pericardial friction rub (sounds like two pieces of leather rubbing together).
- Composed of two layers:
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Endocardium: Innermost layer.
Rheumatic Fever
- Affects connective tissues.
- Caused by Group A beta-hemolytic streptococcus (GABHS) infection.
- NOT caused by GABHS: No rheumatic fever.
- Common causes of GABHS infection: Tonsillitis, pharyngitis, hay fever etc.
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Treatment:
- Amoxicillin and penicillin: Recommended for eliminating GABHS.
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Traditional remedies: (Although not wrong) only target the surface levels of bacteria.
- Gargling with warm salt water.
- Using lozenges like Strepsils.
- Bactidox.
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Untreated GABHS infection:
- can lead to complications affecting the heart, kidneys, and joints (HKJ mnemonic).
- To assess for previous GABHS infection: 询问病人是否患有扁桃体炎或咽炎（2-3周前）.
- If patient is unsure, perform an antistreptolysin O titer (ASO) test.
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Diagnosis:
- Requires two major or one major and two minor criteria (JONES criteria) for diagnosis.
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Major criteria (JONES):
- Joints/Polyarthritis: Inflammation of multiple joints.
- Heart/carditis: Inflammation of the heart.
- Nodules: subcutaneous nodules on the skin.
- Erythema marginatum: Rash with a red center and a clear border.
- Sydenham's chorea: Involuntary movements (jerking motions).
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