coronary artery disease Flashcards
The endothelial cells lining the coronary arteries have
two major roles:
- Regulate vascular tone: vasodilation (e.g., nitric
oxide) and vasoconstriction (e.g., endothelin, angiotensin-converting enzyme [ACE]) - Prevent intravascular thrombosis: (e.g., prostacyclin, plasminogen)
Factors that can impair endothelial function:
- Hemodynamic (e.g., shear stress, hypertension
[HTN]) - Chemical (e.g., low-density lipoprotein [LDL],
modified LDL, homocysteine) - Biologic (e.g., viruses, bacteria, immune complexes)
how does atherosclerotic plaque form
- Begins with disruption of endothelial cell integrity
- Leukocytes, mostly macrophages, are then attracted to the site of disruption, where they collect lipids and coalesce to form a fatty streak
- Fatty streaks mostly consist of lipid-laden macrophages containing cholesterol ester droplets (atheroma)
- Chemoattractants (e.g., platelet-derived growth factor) then cause smooth muscle cells to migrate to the
atheroma, where they produce collagen and fibrous tissue that contribute to plaque formation, covered by a layer of connective tissue called the fibrous cap - Most acute coronary syndromes (ACSs) occur when the
fibrous cap ruptures, leading to thrombus formation
cardiology scale for ACS event
- stable angina
- unstable angina
- Nstemi
- stemi
Plaque characteristics, not size,
determine its vulnerability to rupture
a large, fibrotic plaque with a thick cap is more stable and less prone to
rupture than a small plaque with a soft lipid core and a thin fibrous cap.
- Reproducible angina symptoms (chest pain or pressure) of at least 2 months
- Precipitated by exertion or emotional stress.
- Relived by rest of nitroglycerin
angina pectoris
it is important to recognize that classic symptoms may be absent, and some demographic groups (women and patients with diabetes mellitus) may have atypical symptoms, including exertional dyspnea (if it presents any other way)
atypical angina
Presence of angina during strenuous, rapid, or prolonged ordinary activity
(walking or climbing the stairs).
Angina only with strenuous exertion class 1
tightness, heaviness, or gripping in the chest,
typical angina
white guy angina
Mild myocardial ischemia with no symptoms.
asymptomatic angina class 0
Slight limitation of ordinary activities when they are performed rapidly, after
meals, in cold, in wind, under emotional stress, during the first few hours
after waking up, but also walking uphill, climbing more than one flight of
ordinary stairs at a normal pace and in normal conditions
Angina with moderate exertion class 2
Having difficulties walking one or two blocks or climbing one flight of stairs at
normal pace and conditions.
angina with mild exertion class 3
No exertion needed to trigger angina
angina at rest class 4
- The fundamental problem is an imbalance between myocardial oxygen supply and
demand. - Insufficient coronary blood flow occurs when a plaque leads to arterial stenosis
- Anginal symptoms occur during periods of exercise or stress when increased myocardial
oxygen demand (e.g., from an increase in heart rate, contractility, afterload, or wall
stress) is not met because of impaired coronary blood flow. - There is endothelial dysfunction preventing adequate vasodilation during exercise, which
can occur in the absence of severe luminal narrowing
stable angina
independent risk factor for plaques
diabetes
strong risk factors for CAD
(2 or more, they have it)
1.Older age
2.Male
3.Postmenopausal females
4.Hyperlipidemia (high LDL low
HDL)
5.Cigarette smoking
6.Hypertension
7.Diabetes mellitus
8.Obesity or sedentary lifestyle
9.Family history of early CAD
how to diagnose stable angina
ECG
Approximately 50% of patients with chronic stable angina have a normal resting ECG
* Pathologic Q waves ( Old MI) and conduction system abnormalities (e.g., LBBB, left anterior fascicular block) increase the likelihood of having CAD
stress test
* Stress testing can help risk-stratify patients:
* The sensitivity of an exercise treadmill test is
approximately 70%, the specificity is approximately
80%
* Stress tests add little diagnostic information for
patients with either high or low pretest
probabilities for CAD
* Stress tests are most useful for diagnosing CAD in
patients with intermediate pretest probability
- Typically occur during physical exertion and
gradually resolve with exercise cessation - Symptoms can also occur in conditions that
increase oxygen demand (e.g., anemia, fever,
sepsis, thyrotoxicosis - Substernal chest pressure or burning (less common
to have sharp pain) - Pain may radiate to the upper extremities (left arm
more often than right arm), neck, jaw, or face - Associated symptoms include dyspnea,
diaphoresis, palpitations, and lightheadedness - Women, diabetics, and the elderly are more likely
to have atypical symptoms
symptoms of stable angina
different types of stress tests
- exercise
-meds that mimic exercise (dobutamine, adenosine) - nuclear imaging (thallium 201, technetium 99)
- echocardiography (stressing and doing echo)
- Noninvasive and quantitative assessment of
coronary artery calcification - Higher coronary artery calcium scores are
associated with increased risk of MI and death
Calcium score screening CT:
allows for direct coronary artery visualization of a beating heart with little motion artifact
* Most accurate noninvasive modality in ruling out CAD with a very high negative predictive value
(>95%)
* Less accurate in differentiating degrees of coronary artery stenosis greater than 50%; the positive
predictive value varies between 60 and 90
with dye
Coronary CT
angiography (CCTA):
- Considered the gold standard for diagnosing CAD
- Refer for cardiac catheterization if:
1. Need to confirm or exclude CAD
2. Medical therapy fails to relieve anginal
symptoms
3. History and noninvasive testing suggest high-risk
coronary anatomy
cardiac angiography
