Coronary Heart Disease Flashcards
What is coronary heart disease?
Mismatch between myocardial oxygen supply and demand
What is the cardinal symptom of CAD?
retrosternal chest pain
T or F: ischemia in CAD can result in MI
T
T or F: coronary blood flow increases by 4-fold during exertion
T
What are some factors that can reduce oxygen supply?
Coronary atherosclerosis and sequelae:
- Rupture of an unstable atherosclerotic plaque (most common cause)
- Stenosis
- Thromboembolisms
Vasospasms:
↑ HR (lower perfusion to coronaries)
Anemia
Why does a higher HR decreases perfusion to the coronaries?
Perfusion of the coronaries occurs during diastole. Therefore, higher heart rates reduce perfusion by shortening diastole.
List factors that increase O2 demand?
↑ HR
↑ Afterload
Whats the effect of higher HR on O2 demand and supply?
Increases in heart rate (e.g., during physical exertion) both reduce oxygen supply and increase oxygen demand!
When does myocardial ischemia occur in coronary atherosclerosis ?
Depending on the extent of stenoses (and the corresponding ischemia), patients remain asymptomatic or develop angina and other symptoms. Symptoms usually develop if stenosis is ≥ 70%. If ischemia is severe enough, myocardial infarction can occur.
What happens to blood flow in coronary stenosis?
The greater the stenosis, the higher the resistance to blood flow through the blood vessel, provided the length of the vessel and viscosity of blood remain constant.
List the clinical features of CAD:
Typically retrosternal chest pain or pressure:
- Pain can also radiate to left arm, neck, jaw, epigastric region, or back.
- Pain does not depend on body position or respiration
- No chest wall tenderness
- Angina may be absent, particularly in younger patients
- Often gradual progression
- Can also present as gastrointestinal discomfort
Dyspnea
Dizziness, palpitations
Restlessness, anxiety
Autonomic symptoms (e.g., diaphoresis, nausea, vomiting, syncope)
What is the difference between stable and unstable angina?
Stable:
- reproducible/predictable
- chest pain usually subsides within minutes of exercise (due to release of vasodilators like adenosine), with rest or administration of nitroglycerine
- common triggers mental/physical stress or exposure to cold
Unstable:
- occurs at rest, doesnt go away with nitro
- severe, worsening angina (crescendo angina)
What is nitroglycerin?
A peripheral vasodilator that decreases preload through venous dilation (venous pooling), which can reduce myocardial wall tension and improve myocardial perfusion. It is used to treat angina due to coronary syndrome.
True or False: Unstable angina can progress to MI
True:
Unstable angina is a form of acute coronary syndrome and may progress to myocardial infarction. Most patients with CAD first become symptomatic with acute myocardial infarction or sudden cardiac death!
What is vasospatic angina?
Angina caused by transient coronary spasms (usually occurring close to areas of coronary stenosis)
Unrelated to exertion and may even occur at rest (classically at night)
Caused by cigarette smoking, use of stimulants (e.g., cocaine, amphetamines) or sumatriptan, alcohol, stress, hyperventilation, exposure to cold
How to diagnose vasospastic angina?
- Reversible ST elevation on ECG
- No troponin I or T level elevations on serial measurements
- Coronary spasms on angiography confirm the diagnosis
What are some atherosclerotic signs that can be used for CAD?
- lack of foot pulse, carotid bruit
What are some resting ECG features for CAD?
Usually normal in stable angina
Treat as unstable angina if abnormalities (of the ST segment or the T wave) occur during an episode of chest pain
What is the best initial test for angina?
Resting ECG –> Best initial test for both types of angina (and other types of chest pain)
When is a Cardiac Stress used?
Cardiac stress tests are generally most useful in patients with an intermediate pretest probability of coronary artery disease.
What kind of stress test is used for those unable to exercise (ie aortic dissection)?
pharmacologic stress test (ie. adrenaline-type drug)
What type of detection methods are used in stress test and when are they used?
ECG and imaging (echocardiogram or scintigraphy [radionucleotide scan]) –> echo better for women
ECG used if resting ECG can be interpreted
Imaging if cannot (ie atrial fibrillation)
How long does a patient exercise in a cardiac exercise stress test?
The patient exercises until the target heart rate is achieved (e.g., on a treadmill).
Maximum heart rate = 220 – age (in years) Target heart rate = 85% of the maximum heart rate
What are some contraindications for cardiac exercise stress test?
- Acute myocardial infarction with elevated troponin levels and/or ST elevations (in the past 2 days)
- Unstable angina pectoris or ST depressions at rest
- Decompensated heart failure or severe symptomatic stenosis of one or more heart valves
- Acute endocarditis, myocarditis, or pericarditis
- Hemodynamically significant arrhythmias
- Acute thromboembolic disease
- Acute aortic dissection
- Mental or physical impairment to exercise
What kind of agents are used in a Cardiac pharmacological stress test?
IV administration of positive inotropic/chronotropic substances (e.g., dobutamine) or vasodilators (e.g., dipyridamole or adenosine) to simulate the effect of exercise on the myocardium
What is a chronotropic agent?
An agent with the ability to influence heart rate. Positively chronotropic drugs (e.g., adrenaline) increase heart rate, while negatively chronotropic drugs (e.g., beta blockers) decrease heart rate.
Which patients should undergo cardiac catherization?
Patients with new-onset chest pain, ST segment depression, hypotension or arrhythmias should undergo cardiac catheterization!
What ECG findings in a stress test may indicate CAD?
- Downsloping or horizontal ST depressions of ≥ 0.1 mV in the limb leads and ≥ 0.2 mV in the precordial leads
- ST elevations ≥ 0.1 mV (requires immediate test termination!)
- Excessive or delayed increase in heart rate
- New onset ventricular arrhythmia
What is the purpose of imaging in stress test?
The goal is to distinguish between:
Irreversible ischemia: necrosis (myocardial scars)
Reversible ischemia: tissue that is ischemic (but not yet irreversibly dead) and therefore still potentially salvageable
–> myocardial stunning or hibernating myocardium
What is the treatment approach of CAD?
- -> All patients: risk factor reduction and antiplatelet drugs
- -> Mild CHD: pharmacologic therapy
- -> Moderate CHD: consider coronary angiography and percutaneous transluminal coronary angioplasty (PTCA)/percutaneous coronary intervention (PCI)
- -> Severe CHD: coronary angiography and revascularization or coronary artery bypass grafting
What is coronary angiography?
A procedure that uses contrast dye and radiography to take images of the coronary arteries. Performed via cardiac catheterization by inserting a catheter into an artery of the arm or groin and guiding it to the coronary arteries. –> INVASIVE but GOLD STD
What is percutaneous transluminal coronary angioplasty (PTCA)/percutaneous coronary intervention (PCI)?
An endovascular procedure in which an inflatable balloon is passed over a wire into a narrowed or obstructed artery. Upon inflation, the balloon widens the arterial lumen, which improves perfusion.
What is coronary artery bypass grafting?
A surgical cardiac revascularization technique used to treat patients with significant, symptomatic stenosis of a coronary artery or its branches. The stenosed segment is bypassed using an arterial (e.g., internal thoracic artery) or venous (e.g., great saphenous vein) autograft, re-establishing blood flow to the ischemic areas of the myocardium.
What are the first line agents used for angina?
Beta-blockers (except in vasospastic angina): can reduce the frequency of coronary events [reduces HR and extends diastole]
Nitrates (venous dilator):
Can prevent exertional angina
Suitable for relief of acute angina or for long-term treatment
What are the second line treatment for angina?
- Calcium channel blockers (CCBs): indicated if there are contraindications to beta-blockers or in addition to beta-blockers (if angina or hypertension persist)
- Ranolazine: indicated in stable angina that is refractory to first-line treatment
What are the indications for revascularization techniques (ie. PCI or bypass graft)?
- -> In stable angina: activity-limiting symptoms despite optimal medical treatment, contraindications to medical therapy, stenosis of critical (e.g., LCA) or multiple coronary arteries
- -> Acute coronary syndrome