ISCHEMIC HEART DISEASE Flashcards
risk factors for development of CAD
**male gender
**increasing age
hypercholesterolemia
HTN
cigarette smoking
DM
obesity
sedentary lifestyle
family hx
personality (stress, type A)
stable angina
partial occlusion or chronic narrowing of a segment of coronary artery
- no change in frequency, severity, or duration x2months
- occurs in a predictable pattern, predictably relieved
angina pectoris
imbalance between myocardial oxygen supply & demand
- release of adenosine & bradykinin = pain, slowing of AV conduction rate, decreased contractility
unstable angina
- angina at rest
- angina of new onset
- increase in severity or frequency of previously stable angina
major treatment categories of CAD
- lifestyle modification
- pharmacologic therapy
- revascularization
pharmacologic therapy for CAD
- antiplatelet drugs (aspirin 81mg, plavix/ticlid if indicated)
- BB (decrease O2 demand via decreased HR & contractility, increased supply via increased coronary perfusion time)
- CCB (long acting); uniquely effective in variant angina
- nitrates (dilate coronaries & collaterals –> increased supply)
- ACEI/ARBs
ACS pathophysiology
hypercoaguable state: - focal disruption of plaque susceptible plaques = fibrous cap + lipid-rich core - triggers coagulation cascade: -- thombus formation -- vasoconstriction
diagnosis of acute MI
2 of:
- chest pain
- serial EKG changes indicative of MI
- increase & decrease of serum cardiac enzymes
MI treatment
- evaluate hemodynamic stability/tx if necessary
- 12 lead EKG
- administer O2
- pain relief: IV morphine (reduce catechol)
- nitroglycerin (dilate)
- aspirin/plavix (decrease further thrombus formation)
- reperfusion therapy (tPA, streptokinase) w/in 30-60mins of arrival (RISK: ICH)
- coronary angioplasty (preferred to reperfusion) w/in 90mins of arrival
acute MI complications
- cardiac dysrhythmias (including vfib, vtach, afib, HB)
- pericarditis (px worse w/ inspiration & lying down; auscultate friction rub)
- mitral regurg (ischemia of papillary m. or vent m. @ attachment point) –> papillary m. rupture?
- ventricular septal rupture
- CHF & cardiogenic shock (hypotension/oliguria)
- myocardial rupture
- RV infarction (isolated RV infarct is unusual)
- CVA
preoperative MI factors that change incidence
- preoperative medical condition
- specific surgical procedure
- surgeon skill
surgery-induced risk factors of MI
- inflammatory response = hypercoaguable state (lead to decreased O2 supply)
- neuroendocrine response = increased HR/BP (increased O2 demand)
- postop shivering = increased O2 demand
- decreased Hct = decreased O2 supply
- hypoxia = decreased O2 supply
major clinical predicators of increased perioperative CV risk
- unstable coronary syndromes (acute/recent MI, unstable or severe angina)
- decompensated HF
- significant dysrhythmias (AVB, symptomatic ventricular dysrhythmias, supraventricular dysrhythmias w/ rapid ventricular rate)
- severe valvular heart dz
intermediate clinical predictors of increased perioperative CV rsik
- mild angina
- h/o MI
- compensated or h/o HF
- DM
- renal insufficiency
minor clinical predictors of increased perioperative CV risk
- advanced age (>70)
- abnormal EKG (LV hypertrophy, LBBB, ST abnormalities)
- rhythm other than SR
- low functional capacity
- h/o CVA
- uncontrolled HTN
best evidence of decreased cardiac reserve (in the absence of significant lung disease)
exercise tolerance
- if pt can climb 2-3 flights of stairs w/out symptoms, it is likely that cardiac reserve is adequate
elective surgery after angioplasty?
- wait 4-6 weeks
- 6 weeks after bare metal stent placement
- 12 months after drug-eluting stent placement
high risk surgery
- emergency major surgery
- AAA repair or other major vascular surgery
- peripheral vascular operation
- prolonged procedures w/ large fluid shifts/blood loss:
- thoracotomy
- major abdominal operation
preoperative management goals w/ ischemic heart disease patient
- determining the extent of ischemic heart disease & any previous interventions
- determining severity & stability of the disease
- reviewing medical therapy & noting any drugs that can increase bleeding/contraindicate a particular anesthetic technique
Lee Revised Cardiac Risk Index
PREOP
(6 independent predictors of major cardiac complications)
- high risk surgery
- ischemic heart disease
- CHF
- cerebrovascular disease
- IDDM
- creatinine >2.0mg/dL
preop algorithm for pts with ischemic heart disease
- emergent/urgent surgery?
- optimize & proceed - elective surgery?
- unstable CAD/change in cardiac condition –> get cardiac consult
- stable –> stratify risk further:
risk stratification:
for high/intermiedate risk procedure w/ moderate/minor risk factors:
1. prior revascularization?
- prior CABG w/ stable medical condition = proceed to OR
- prior PCI = consider type of stent & proceed accordingly
2. no prior revascularization?
- stable CAD = proceed to OR
- unstable or unable to assess = obtain noninvasive testing FIRST
functional capacity evaluation & documentation
expressed as metabolic equivalent of task (MET)
- 3.5mL/kg O2 consumption = 1 MET
- increased risk w/ poor functional capacity, <4MET
4MET = baking, dancing, golfing, walking
intermediate risk surgery
- carotid endarterectomy
- head/neck surgery
- orthopedic surgery
- prostate surgery
- intraperitoneal & intrathoracic surgery
low risk surgery
- endoscopic
- superficial
- cataract
- breast
who gets further cardiac evaluation preoperatively?
2 of:
- high risk surgery
- low exercise tolerance
- moderate clinical risk factors
interventions that can modulate triggers of perioperative cardiac events
- statins = decrease plaque buildup
- antiplatelet/angicoagulants = decrease thrombus formation
- oxygen = decrease hypoxia
- transfusion = increase hct/O2 delivery
- nitroglycerin = prevent vasoconstriction
- maintain BP = ensure adequate coronary flow
- alpha2 agonists/analgesics = attenuate neuroendocrine response to surgery (catechol release)
- normothermia = prevent shivering (O2 demand)
- BB = prevent increased O2 demand
intraoperative management goals in those w/ ischemic heart disease
- optimize myocardial O2 supply & keep O2 demand low
2. monitor for ischemia, & tx it if it develops
factors that decrease myocardial O2 supply
- decreased coronary blood flow (patency)
- tachycardia
- diastolic hypotension
- hypocapnia (= coronary artery vasoconstriction)
- coronary artery spasm
- decreased PaO2
- anemia
- arterial hypoxemia
- L shift of oxyhemoglobin dissociation curve
- increased blood viscosity
factors that increase myocardial O2 demand
- SNS stimulation
- tachycardia
- HTN
- increased myocardial contractility
- increased afterload
- increased preload
- shivering
- hyperglycemia
induction of anesthesia in pts w/ ischemic heart disease
- anxiolysis pre-operatively
- no ketamine, preferably etomidate or high opioids
- use NDNMB w/out HR/BP implications (vec, roc, cis)
- be quick w/ DL
- minimize SNS response = lidocaine, esmolol, fentanyl
anesthesia maintenance w/ ischemic heart disease
- AVOID TACHYCARDIA
- NO HYPOTENSION
- keep vitals w/in 20% of pre-op value
- normal preload & afterload
- decrease contractility if LVF is normal (demand)
- maintain NSR
Options
- volatile agent = controlled myocardial depression to avoid increased demand
- opioids for those w/ LVF = avoid myocardial depression w/ volatiles
- regional = avoid hypotension >20% of initial BP –> phenylephrine or ephedrine if bradycaria
EKG monitoring for ischemia perioperatively
- evaluate for ST depression
- II (RCA)
- V5 (LAD)
lead/vessel relationship
RCA = II, III, aVF LCx = I, aVL LAD = V3, V4, V5
perioperative ischemia monitoring options
- EKG (ALWAYS)
- PA cath (not shown to be associated w/ improved outcomes)
- transesophageal echocardiography (evaluate regional wall motions)
- abnormalities occur before EKG changes occur
- abnormalities can be attributed to events other than myocardial ischemia
intraoperative management of MI
- when ST segment changes >1mm on EKG
tx changes in HR/BP
- IV BB
- nitroglycerin if BP elevated
- sympathomimetic to tx hypotension
- inotropes if hemodynamically unstable
- intra-aortic balloon pump may be necessary
- plan for early postop cardiac catheterization if applicable
causes of ischemic heart disease
- atherosclerosis (most common)
- severe HTN or tachycardia
- coronary artery vasospasm
- hypoxia
- anemia
- severe AI or AS
perioperative MI incidence
risk of perioperative death 2/2 cardiac causes = <1% in general population
- most perioperative MIs occur w/in the first 24-48hrs postoperatively
