Exam 2: Cardiac Flashcards
Myocardial ischemia is characterized by:
Metabolic O2 demand that exceeds supply
Most common cause of myocardial ischemia:
Narrowing of coronary arteries d/t atherosclerosis
Secondary causes of myocardial ischemia:
HTN or tachycardia (severe) Coronary vasospasm Hypotension (severe) Hypoxia Anemia Aortic insufficiency/stenosis (severe)
Mortality rate of myocardial infarction:
1/3rd
Incidence of myocardial ischemia in surgical patients:
5-10% (estimated)
Major risk factors for myocardial ischemia:
Age (75+) Male ↑LDL Diabetes Hypertension Smoking \+ family hx
Minor risk factors for myocardial ischemia:
Obesity CV disease PVD Menopause Use of estrogen BCPs Sedentary lifestyle High stress/type A personality
Describe how atherosclerosis leads to myocardial damage:
Plaque partially obstructs blood flow
Unstable plaque ruptures/thromboses
Transient ischemia leads to unstable angina; sustained ischemia leads to myocardial infarction/inflammation/necrosis
Effects of sustained ischemia on myocytes:
Stunned/hibernating myocytes
Effects of myocardial infarction/inflammation on myocytes:
Myocardial remodeling
Characteristics of plaques prone to rupture:
Lipid rich core
Thin, fibrous cap
Factors that lead to plaque rupture:
Shear forces
Inflammation
Apoptosis
Macrophage enzymes
Results of plaque rupture:
Inflammation and cytokine release, platelet activation, thrombin production
Thrombus forms over lesion; vasoconstriction of vessel
Results of thrombus formation d/t atherosclerotic plaque rupture:
Acute decrease in coronary blood flow
Unstable angina or myocardial infarction
Cells that infiltrate atherosclerotic plaques:
T cells and macrophages
Six characteristics of rupture-prone plaques:
- T cells in the shoulder region
- Macrophages clustered around T cells
- Thin, fibrous cap
- Lipid rich core
- Newly formed capillaries within the wall
- Lymphocyte/mast cell infiltration
More significant to plaque: size or instability?
Instability
Substances that degrade the collagen plaque cap:
Metalloproteinases
Mechanical stress on plaques maximal at this point:
Junction of fibrous cap and plaque-free vessel wall
Physiologic responses to stress (4):
↑ catecholamines, HR, BP
↓ plasma volume
↑ coronary constriction
↑ platelet activity
Cardiac changes due to physiologic responses to stress (3):
↑ electrical instability
↑ demand
↓ supply
Pathologic effects of stress on cardiac function (4):
VF/VT
Ischemia
Plaque rupture
Coronary thrombosis
Surgical stressors that can impact cardiac function:
Pain
Anxiety
Hypovolemia
Describe stable angina:
No change in precipitating factors for 60+ days
No change in frequency, duration of pain
Describe unstable angina:
Caused by less than normal activity
Prolonged duration
Increasing frequency
Unstable angina signals:
Impending MI
Physiological changes associated with stable angina:
Fixed narrowing: 75% or greater
O2 demand close to normal at baseline
Relieved by rest, reducing demand, or NTG
Physiological changes associated with unstable angina:
Acute plaque changes
Partial thrombosis
Crescendo-ing intensity
↑ frequency, duration, etc
Can cause infarction!
Describe Prinzmetal angina:
Occurs at rest
Coronary spasm
In plaque area or normal vessel
Can be associated with other vasospastic diseases (Reynaud’s)
Define infarction:
Necrosis caused by ischemia
Where and when does infarction occur?
Within 20-30 mins of ischemia
Subendocardial regions
Reaches full size in 3-6 hrs
Size of infarction depends on:
Proximity of lesion
Collateral circulation
Complications of myocardial infarction:
Papillary muscle dysfunction & valvular disease Rupture of infarct Mural thrombi Acute pericarditis Ventricular aneurysm Arrythmias LV failure & pulmonary edema Cardiogenic shock Rupture of wall/septum/papillary muscle Thromboembolism
Describe rupture of myocardial infarct:
Occurs day 4-7
Followed by tamponade and death
Sequelae of mural thrombi:
Stroke
Timing of post-MI pericarditis:
Day 2-4
Most common site for ventricular aneurysm:
Anteroapical region
Incidence of cardiogenic shock post-MI:
10%
Leads which look at LV:
II, V5
Define vascular hypertension:
Diastolic > 90mmHg
Systolic > 140mmHg
Incidence of HTN:
25%
↑ in black pts
HTN is a primary risk factor in:
CAD CVA Cardiac hypertrophy Renal failure Aortic dissection
Causes of HTN:
90-95% idiopathic
5-10% secondary to renal disease
Causes of secondary HTN:
Renal
Endocrine
Cardiovascular
Neurologic
BP = ? x ?
BP = CO x PVR
CO factors that ↑ BP:
Blood volume
Contracility
PVR factors that ↑ BP:
Constrictors/dilators in bloodstream
Neural influences
Local factors
Genetic risk factors for HTN:
Polygenic and heterogenous
Polymorphisms at several different gene loci
Environmental risk factors for HTN:
Stress Obesity Smoking Salt consumption Sedentary lifestyle
Renal theory of HTN:
↓ renal excretion of Na+ leads to ↑ fluid volume/CO
Vasoconstriction d/t autoregulation leads to ↑ BP