PHTY208 Lecture Notes - Lecture 9: Aortic Dissection, Palpitations, Tachycardia
Disorders of cardiac function
• Ischemic/coronary heart disease
o Refers to an imbalance between myocardial oxygen demand and supply
o Results in myocardial hypoxia and accumulation of waste metabolites
o Ischemic heart disease is often a result of occlusion of the coronary circulation
o Also known as coronary heart disease
o Supplies the myocardium with oxygen and nutrients
o Commonly divided into two disorders
• Chronic ischemic heart disease
▪ Recurrent and transient episodes of myocardial ischemia
▪ Stable angina
• Acute coronary syndromes
▪ Represent the spectrum of ischemic coronary disease, ranging from
unstable angina through myocardial infarction
▪ Results from disruption of plaque
o Classifications
• Angina pectoris
• Stable angina
• Unstable angina
• Myocardial infarction
• Silent ischemia
• Variant angina
o Angina pectoris
• Commonly known as angina
• Chest pain due to ischemia of the heart muscle
• Generally due to obstruction or spasm of the coronary arteries
• Manifestations:
▪ Constricting or squeezing pain in the pericardial or substernal area of
the chest, possibly radiating to the arms, jaw or thorax
▪ Pain is typically relieved by rest
• Causes
▪ Most common cause of angina is atherosclerosis
▪ Two main types of lesions
•
Stable
• Associated with a fixed coronary obstruction
• More common in stable angina
•
Unstable
• Can rupture and cause platelet adhesion and thrombus
formation
• More common in unstable angina and myocardial infarction
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o Stable angina
• Predictable, transient chest discomfort during exertion or emotional stress
• Pattern of symptoms related to degree of occlusion
• When vessel is occluded by approximately 70%
▪ Enough oxygen at rest
▪ Insufficient to compensate with increased oxygen demands
• Manifestations
▪ Often described as pressure, discomfort, tightness, burning or
heaviness in the chest
▪ Rarely described as pain
▪ Sensation is neither sharp nor stabbing
▪ Does not vary significantly with inspiration
▪ Rarely lasts more that 5 – 10 min
▪ Accompanying symptoms
• Tachycardia
• Diaphoresis
• Nausea
• Dyspnoea
• Fatigue and weakness
o Acute coronary syndromes
• Life threatening conditions
• Commonly from a ruptured plaque resulting in coronary thrombosis
• Range of syndromes that include
▪ Unstable angina
▪ Acute myocardial infarction
• Acute MI can be further divided into: (naming from ECG)
▪ Non-ST elevation myocardial infarction
▪ ST elevation myocardial infarction
• Coronary thrombosis
• Pathogenesis of ACS
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• Determinants of ACS
▪ Persons with an ACS are routinely classified as low risk or high risk for
infarction based on
•
Presenting characteristics
•
ECG variables
•
Serum cardiac markers
•
Timing of presentation
• Unstable angina
▪ Considered to be a clinical syndrome of myocardial ischemia
▪ Causes can be divided into 3 phases
•
Atherosclerotic plaque disruption
•
Platelet aggregation
•
Secondary haemostasis
▪ Inflammation also plays a role in plaque instability
▪ Symptoms of unstable angina
•
Worsening angina attacks (from stable angina)
•
Sudden-onset angina at rest
•
Angina lasting more than 20 minutes
•
Occurs at rest or minimal exertion
•
Severe and described as frank pain
•
Occurs with a crescendo pattern (more severe, prolonged, or
increased frequency)
•
Usually due to a trigger event
• Emotional stress, physical activity
•
May herald myocardial infarction
▪ Basis for diagnosis
•
Pain severity and presenting symptoms
•
Haemodynamic stability
•
ECG findings
•
Serum cardiac markers
• Acute myocardial infarction
▪ Heart attack
▪ Myocardial ischemia is sufficiently severe to cause myocyte necrosis
(damage to the muscle cells)
▪ Risk factors
•
Previous cardiovascular disease and high blood pressure
•
Age
•
Tobacco smoking,
•
Lack of physical activity and obesity, excessive alcohol consumption,
the abuse of illicit drugs
•
Diabetes and chronic kidney disease
•
Chronic high stress levels
▪ Non ST-elevation myocardial infarction
•
In a NSTEMI, the blood clot only partly occludes the artery
•
Only a portion of the heart muscle being supplied by the affected
artery dies
•
Does not produce characteristic elevation in the "ST segment"
portion of the ECG
•
Cardiac enzymes determine if event was NSTEMI or unstable angina
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Document Summary
Ischemic/coronary heart disease: refers to an imbalance between myocardial oxygen demand and supply, results in myocardial hypoxia and accumulation of waste metabolites. Stable angina: acute coronary syndromes, represent the spectrum of ischemic coronary disease, ranging from unstable angina through myocardial infarction, results from disruption of plaque, classifications. Stable angina: angina pectoris, unstable angina, myocardial infarction. Insufficient to compensate with increased oxygen demands: manifestations, often described as pressure, discomfort, tightness, burning or heaviness in the chest. Sensation is neither sharp nor stabbing: rarely described as pain, does not vary significantly with inspiration, rarely lasts more that 5 10 min, accompanying symptoms, tachycardia, diaphoresis, nausea, dyspnoea. Life threatening conditions: commonly from a ruptured plaque resulting in coronary thrombosis, range of syndromes that include, unstable angina, acute myocardial infarction, acute mi can be further divided into: (naming from ecg, non-st elevation myocardial infarction. Inflammation also plays a role in plaque instability.
