N305: Myocardial Infarction Heart Attack

1
N305 Myocardial InfarctionHeart Attack

• A life-threatening condition characterized by the
  formation of localized tissue necrosis within the
  myocardium
• usually caused by reduced blood flow in a
  coronary artery d/t atherosclerosis and a
  complete occlusion of an artery by an embolus or
  thrombus
• other causes vasospasm, ?O2 supply, ?O2
  demand

2

• Ischemia can lead to myocardial cell death within
  30 minutes (50 of the involved myocardium dies
  within two hours!)
• As the myocardial cells necrose (die),
  intracellular enzymes and cardiac muscle
  proteins are introduced into the blood stream
• The most common site of infarction is the
  anterior wall of the left ventricle, due to
  occlusion in the LAD branch of the LCA (referred
  to as an anterior MI)

3

• Other sites
• L circumflex (posterior or lateral MI)
• RCA (inferior MI, 25 of the time in RV)
• MI may also be classified according to depth of
  infarct
• subendocardial, intramural, or subepicardial
  (involving one layer) - non-Q wave
• transmural (all three layers of myocardial tissue
  involved) - Q wave (see abnormal Q wave within 3
  days)
• ST segment elevation MI (STEMI)
• Non-ST segment elevation MI (NSTEMI)

4
(No Transcript)
5

• Infarct site known as zone of infarction
• Next zone, zone of hypoxic injury
• Outermost zone, zone of ischemia, a zone of
  reversible damage
• Each zone is associated with corresponding time
  mediated EKG changes
• infarct zone (Q wave within 1-3 days)
• hypoxic injury zone (ST segment elevation
  immediately)
• ischemic zone (inverted T wave within 1-2 days)

6
- The first six hours after the onset of pain is
the crucial time frame for salvage of the
myocardium time is muscle in relation to
outcomes - The first 24 hours after an MI is the
time of highest risk for sudden death
7
Prognosis

• 70-80 survive the initial attack
• chances for survival diminish with age (gt80yrs.
  60 mortality rate)
• the co-existence of another cardiovascular
  disease, respiratory disease, or uncontrolled
  diabetes carries a mortality rate above 30
• 30 mortality rate with anterior MI
• 60 mortality rate if hypotensive (SBP lt55) on
  admission

8
Non life threatening complications

• Pericarditis r/t inflammation (28 of clients
  with Q wave infarct, within 2-4 days)
• Mitral valve insufficiency (d/t rupture of
  papillary muscle of the LV, a complication of
  myocardial necrosis) within 2-7 days

9
Life-threatening complications

• severe dysrhythmias (40-50 of all deaths)
• cardiogenic shock (9 with 80 fatality rate)
• heart failure (1/3 of in-hospital deaths)
• heart (ventricular) rupture (d/t myocardial
  necrosis)
• pulmonary embolism (10-20, secondary to DVT or
  atrial flutter or fibrillation)
• recurrent MI
• Extent of damage determined by the size of the
  infarct and the amount of collateral circulation
• Complete recovery may take anywhere from 6-12
  weeks

10
Clinical Manifestations See chart 28-6, p. 729,
in course text

• Chest pain
• of sudden onset (unlike angina, no precipitating
  event), lasting longer than 20 minutes
• similar to, but more severe than, anginal pain
• not relieved by rest or nitroglycerine
• may radiate to the neck, jaw, shoulder, back, or
  left arm
• may also be associated with nausea or dizziness,
  SOB, anxiety, weakness or fatigue, palpitations,
  cold sweat, or paleness (pallor)

11
(No Transcript)
12
Diagnosis

• history of present illness/presenting symptoms
• past hx. (known hx. of CAD)
• family history
• baseline EKG (within 10 minutes on arrival)
• laboratory tests (cardiac enzymes/cardiac
  biomarkers)
• physical exam insufficient on its own

13
EKG changes (time mediated)

• occur in the leads that view the involved
  surfaces of the heart
• due to ischemia, injury, and necrosis
• T wave inversion (ischemia) 2
• ST segment elevation (injury) 1
• Q wave ?er than 25 of the R wave in depth
  (infarct) 3
• T wave ST segment changes eventually revert to
  normal Q wave change persists

14
Serum Markers of AMI see Table 28-5, p. 731, in
course text

• Enzymes are proteins inside all living cells
• CK-MB (one of three isoenzymes of CK)
• increase 4-8 hrs. after pain onset, peaks in
  12-24 hrs., return to normal levels in 3 days
• Myoglobin (a heme protein that helps to
  transport oxygen, found in cardiac and skeletal
  muscle)
• rapidly released into bloodstream, detected
  within 1-3 hrs., peaks within 4-12 hours, not
  diagnostic after 12 hrs.
• lacks specificity, therefore useful only to R/O
  MI

15

• Troponin (a protein and a basic component
  involved in myocardial contraction, isomers T I
  are cardiac specific)
• Troponin preferred biomarker for MI (more
  sensitive and more specific than the others)
• increase 3-4 hrs, peak in 4-24 hrs., remains
  elevated for 1-3 weeks (avg. 10 days), ? in
  unstable angina
• enables late diagnosis (24 hours after the event)
• may mask reinfarction occuring in 5-7 days

16
(No Transcript)
17
Other Lab tests

• Leukocytosis
• appears on the second day post MI, disappears in
  one week
• radionuclide imaging
• Thallium scan (cold spots)
• Technetium 99 (hot spots)
• echocardiography (transthoracic)
• wall motion and ejection fraction
• transesophageal echocardiography (TEE)
• wall motion
• stress testing (ETT)

18
Goals of treatment

• initiating prompt care to minimize damage,
  preserve function, and prevent complications
  (improve outcomes)
• reperfusion of the myocardium is the ideal
• aim for door-to-needle time of 30 min (ideally
  within 1 hour but can be given within 12 hours)
• reducing pain
• rehabilitating and educating the client and
  significant others (secondary prevention)

19
Medical Management

• Treat acute attack
• Immediate care (prehospital)
• CPR (defibrillation) if unconscious
• keep client quiet and calm/rest
• ASA 162-325 mg. (non-enteric coated/chew
  swallow)
• elevate head, loosen clothing
• oxygen
• IV insertion

Goldick, G. (2005). Myocardial infarction
Getting in line with the new guidelines.
Nursing, 35(9), 32cc1-32cc6
20

• Reduce pain (upon admission)
• administer oxygen therapy (NP _at_ 4L/min X 6
  hours)
• initiate cardiac monitoring
• assure/obtain IV access
• draw serum cardiac markers/troponin
• do a 12 Lead EKG
• nitro SL X 3, institute Nitrodrip as ordered
• pain control with IV morphine (drug of choice -
  ? pain, ? anxiety, vasodilator, bronchodilator)
• example of dose for morphine is 2-4 mg q 5-15 min
  until pain is relieved (up to a maximum dose of
  15 mg/event.), monitor closely
• admin antidysrhythmic medications as needed

21

• Improve perfusion
• administer anti-ischemic therapy (e.g., beta
  blockers, IV nitroglycerin)
• administer thrombolytic therapy (STEMI only)
• thrombolytic agents (thrombolytics), if not
  contraindicated - see Chart 28-7, p. 731, in
  course text)
• streptokinase, tenecteplase (TNK), t-PA
  (alteplase)
• may be given within 12 hours after the onset of
  chest pain (preferably within one, ideally within
  30 minutes)
• ? infarct size, preserve LV function, ?survival
• administer according to protocol (e.g., with
  heparin)
• institute bleeding precautions

22

• Other
• ACE inhibitors (within first 24 hours of a STEMI)
• prevent heart failure/decrease mortality rate
• closely monitor BP, urine output, serum sodium,
  potassium, and creatinine
• contraindicated with hypotension, hypovolemia,
  hyponatremia, or hyperkalemia
• PCI (percutaneous intervention)/PCTA
• door-to-balloon time 60-90 min
• be prepared for emergency CABG

23

• Monitor for complications
• dysrhythmias
• ectopic rhythms (esp. ventricular), conduction
  disturbances (heart blocks)
• cardiogenic shock
• heart failure and pulmonary edema
• pulmonary embolism
• recurrent MI
• mitral valve regurgitation r/t myocardial
  necrosis (within 2-7 days)
• Dresslers syndrome, a form of pericarditis,
  within 6 weeks to months after AMI may be
  autoimmune in nature

24

• Rehabilitation and Education
• bedrest (Level 1) for less than 24 hrs. unless
  complications arise
• bedside commode for BM
• ? 2 gm. sodium diet
• start passive exercises
• gradually increase (level) exercise to target
  heart rate or as tolerated (remain asymptomatic)
• home by end of second week (after stress test,
  cardiac catheterization)

25

• resume sexual intercourse within 4-8 weeks (if
  able to walk _at_ a rate of 3-4 mph without pain,
  wait 1 hour after eating or drinking, resume
  usual positions, caution against anal
  intercourse)
• stop smoking
• avoid strenuous activities (e.g., shoveling,
  activity requiring a sudden burst of energy)
• walk daily, aiming for 2 miles in less than 60
  min
• if asymtomatic, return to work at the end of week
  8 or 9
• complete medical evaluation between weeks 8 10

26
Nursing Management

• Goals
• recognize and treat cardiac ischemia
• administer thrombolytic therapy as ordered, and
  observe for complications
• recognize and treat potentially life-threatening
  dysrhythmias
• monitor for complications of reduced CO
• see standing/routine coronary care orders
  handout
• maintain a therapeutic critical care environment
• identify the psychosocial impact of MI on the
  client and family
• educate the client in lifestyle changes and
  rehabilitation

27
Prevent complications

• no leg crossing
• position changes/passive exercises
• monitor fluid balance
• control nausea vomiting

28
Activity progression

• increase activity as tolerated (METS)
• HR increase less than 25 of resting rate or
  120/min., no more than a 25mm Hg rise in BP, no
  dyspnea, chest pain, fatigue, or dysrhythmias, O2
  sat gt93 or a drop less than 3, a return to
  resting pulse within 3 minutes
• get adequate rest
• avoid valsalva (vasovagal) maneuver (e.g.,
  isometric exercise, weight lifting, constipation)
• avoid arms above head (e.g., washing walls)
• adoption of supervised exercise program
  (including a warm up and a cool down)
• resumption of normal activities
• sexual activity
• return to work
• drive car (3-4 weeks)

29
Education

• cardiac anatomy physiology
• the nature of MI
• management of chest pain
• drugs (action, dose, side effects, etc.)
• ASA, nitroglycerine, ß blockers, Ca channel
  blockers, ACE inhibitors, antilipidemics)
• need for follow-up
• when to seek help (e.g., call 911)
• benefits of exercise
• other risk factor modification

30
Tailored risk factor modification

• smoking cessation
• diet (?Na, ?cholesterol saturated fats, ?fiber)
• achieve and maintain ideal weight
• blood sugar control
• control of hypertension
• moderate caffeine
• HRT
• stress management

31
(No Transcript)