Ischemic Heart Disease Flashcards
What is the leading cause of death in men and women in the US?
CAD
About ___% of our patients will have CAD
30%
Causes of CAD
Narrowing of the arteries due to:
- Atherosclerosis
- Severe HTN or tachycardia
- Coronary vasospasm
- Severe hypotension
- Hypoxia
- Anemia
- Severe AI or AS (these patients will have hypertrophied ventricles and higher O2 demands)
Clinical Manifestations of CAD
- Ischemia
- Angina
- MI
- Arrhythmia
- Ventricular dysfunction (CHF)
- Sudden Death
___% of MIs are silent
70%
Remember that if you suspect your patient has CAD, but no angina, they probably have it. It’s just silent.
Risk factors for CAD
- Age
- Men
- HTN
- DM
- Hyperlipidemia
- Smoking
- Family history
- Obesity and sedentary lifestyle
- PVD
- Menopause
- Use of high estrogen contraceptives
- Psychosocial characteristics (Type A personalities)
What is the source of pain from cardiac ischemia?
Adenosine and bradykinin released during ischemia.
These chemicals stimulate neurons in the heart that produce thalamic and cortical stimulation, resulting in the typical chest pain associated with angina
These substances also slow AV nodal conduction and decrease contractility, improving the O2 supply and demand balance
What is unstable angina?
Angina that has changed its characteristics within the past few weeks of surgery.
Occurring more frequently or more severely
Lasts for long periods
Caused by less than normal activity
Signals impending MI***
Do we take patients to the OR with unstable angina?
FUCK NO
Only exceptions are emergencies
What is stable angina?
No change in pattern for at least 60 days.
What is stunning?
BRIEF periods of ischemia that lead to myocardial dysfunction that can last several hours
What is hibernation?
Impaired myocardial function from ongoing impaired coronary BF, but is relieved following return of normal BF
What is preconditioning?
Brief intermittent periods of ischemia allow for some protection against a subsequent larger ischemic insult, and therefore limits infarct size (I guess because the heart is kind of used to having ischemia on and off)
These things can evoke preconditioning
Exercise, pacing, and opioids. IAs also modulate preconditioning by blocking triggers.
Pharm management of CAD
BBs- reduce HR and contractility CCBs- dilate coronaries, reduce contractility and afterload. Not used for long-term therapy anymore. Nitrates- dilate coronaries and collaterals, decreases preload and afterload (decreases cardiac stretch and force it has to push against) Anti-plts- reduce potential for thrombosis
Procedures we may have to manage for CAD
1) PCI - Balloon angio - Bare metal stenting - Drug eluting stenting 2) CABG - OPCAB (off-pump CABG) - MIDCAB (minimally invasive direct CABG) 3) TMR (transmyocardial revascularization)
Stenting and surgical delays
Will have to delay d/t length of antiplt therapy needed Coronary angioplasty (4-6 weeks) Bare metal stents (30-45 days) Drug eluting stents (1 year)
What is acute coronary syndrome?
An acute decrease in coronary blood flow due to: Plaque rupture triggers coagulation cascade and leads to a hypercoagulable state, platelet accummulation, formation of a thrombus, and acute partial or total occlusion of the coronary artery.
Which is more of a threat to a vessel, a plaque that is large? Or a plaque that is unstable?
A plaque that is unstable.
Characteristics of disrupted plaques
Eccentric (not uniform) Large, necrotic, soft, lipid-rich core (Mmmmm) Covered by a THIN fibrous cap Righ in macrophages and T cells
What happens when a plaque ruptures?
Platelet aggregation at site Release of Thromboane A2 by activated platelets (potent vasoconstrictor) Activation of IIb/IIIa receptors on platelets, which allows plts to stick together and strengthen the thrombus Fibrin is deposited Thrombus is thusly formed. This process can cause angina, infarction, or sudden death. Can dislodge and send microemboli to smaller vessels. Vasospasm can occur.
Infarction begins within __-__ minutes of ischemia
20-30min
Infarction usually reaches its full size in __-__ hours
3-6
Size of an infarction depends on
Location of the lesion Amount of collateral circulation
How is an MI diagnosed?
Requires 2 of these 3 criteria: - Chest pain - EKG changes indicative of MI - Elevated cardiac enzymes Can also get a cardiac MRI to evaluate the extent of the infarction
INITIAL treatment of an MI
Get a BP (how is their pressure holding up with these cardiac changes?) 12 lead-EKG MONA - Morphine - O2 - NTG - ASA or clopidogrel
Reperfusion therapies for MI
1) Thrombolytics - tPa, streptokinase, reteplase, tenecteplase - Begin within 30-60 min of arrival 2) Direct coronary angioplasty - Must be performed within 90 minutes of arrival and 12 hours of onset - About 5% will fail and require surgery 3) CABG - High risk of mortality if performed within 3-7 days after an MI
Adjunct medical treatment for MI after all the initial shit has been done
Heparin BBs Glycemic Control Statins ACE Inhibitors (if anterior wall MI, LV failure, EF
Diagnosis of unstable angina / non-STEMI
Change in angina symptoms EKG changes ST depression in 2 or more contiguous leads and/or symmetrical T wave inversions Troponin Levels
Treatment for unstable angina
Maximize perfusion and minimize O2 consumption! Basically, same as treatment for CAD, but also bed rest, O2, pain control, and possible coronary intervention. Remember that unstable = impending MI! Bed rest Give O2 Give analgesia (decrease SNS response) BBs NTG ASA or plavix or hepatin May require revascularization surgery If this happens in the OR, all we can really do is decrease O2 demand and give O2. So we can give BBs, NTG, and O2.
Complications of infarction
Arrhythmias Thromboembolism (can cause stroke) Cardiogenic Shock LV failure and pulm edema Papillary muscle dysfunction (causes valvular disease) Ventricular aneurysm (fibrous outpouching of the ventricle (most commonly in the anteroapical region) External rupture of infarct (may happen 4-7 days post-MI and cause effusion/tamponade) Acute pericarditis (2-4 days post-MI)
For the general population, risk of peri-op death from cardiac causes is _____
less than 1%
When do most peri-op MIs occur?
24-48 hours AFTER surgery!!
Factors that will decrease O2 supply to the heart
Tachycardia (less time in diastole) Hypotension Vasoconstriction Low O2 carrying capacity (anemia, hypoxia, acid/base balance) High viscosity Arterial patency Coronary spasm