Perioperative myocardial infarction ppt

Perioperative myocardial infarction
( PMI ) is the common cause of
morbidity and mortality in patients
who have had noncardiac surgery.

INCIDENCE
5.8% overall risk of postoperative major cardiac
complications in patients undergoing
major noncardiac surgical procedures.
Defining PMI, is often difficult :
 Most PMIs occur without symptoms in anesthetized or
sedated patients.
 The creatine kinase-MB isoenzyme has limited
sensitivity and specificity because of coexisting skeletal
muscle injury.
Consequently, PMI was often recognized late
(postoperative day 3 to 5), resulting in high (30% to
70%) mortality.

Two distinct mechanisms may lead to PMI:
 Acute coronary syndrome.
 Prolonged myocardial oxygen supply-
demand imbalance in the presence of stable
coronary artery disease (CAD).

 Acute coronary syndrome occurs when an
unstable or vulnerable plaque undergoes
spontaneous rupture, fissuring, or erosion,
leading to acute coronary thrombosis,
ischemia, and infarction.
 External stressors ,those occurring
postoperatively are believed to contribute.

 The sympathetic induced Tachycardia and
Hypertension, common in the perioperative
period, may exert shear stress, leading to rupture
of plaques.
 Increased postoperative procoagulants
(fibrinogen, factor VIII coagulant, von Willebrand
factor, α1-antitrypsin), increased platelet
reactivity, decreased endogenous anticoagulants
(protein C, antithrombin III), and decreased
fibrinolysis have been reported.

 Tachycardia is the most common cause of
postoperative oxygen supply-demand
imbalance.
 Heart rates >80 bpm in patients with
significant CAD can lead to prolonged
ischemia and PMI.

 Postoperative hypotension
(hypovolemia, bleeding, or systemic
vasodilatation), hypertension (elevated stress
hormones, vasoconstriction), anemia, hypoxe
mia, and hypercarbia aggravate ischemia.
 Stress-induced and ischemia-induced
coronary vasoconstriction impairs coronary
perfusion.

The 2007 ACC/AHA guidelines on cardiovascular
evaluation for noncardiac surgery concluded that
three elements must be assessed to determine the
risk of cardiac events :
 Patient specific clinical variables.
 Exercise capacity.
 Surgery-specific risk.

Major predictors that require intensive management
and may lead to delay in or cancellation of the
operative procedure.
 Unstable coronary syndromes including unstable
angina or recent MI.
 Decompensated heart failure including NYHA
functional class IV or worsening or new-onset HF
 Significant arrhythmias
 Valvular heart disease-severe AS/ severe MS

Other clinical predictors that warrant careful
assessment of current status.
 History of ischemic heart disease
 History of cerebrovascular disease
 History of compensated heart failure or prior
heart failure
 Diabetes mellitus
 Renal insufficiency

 Patients with good functional status have a lower
risk of complications.
 Functional status can be expressed in metabolic
equivalents (MET).
 1 MET is defined as the oxygen uptake in a sitting
position (3.5 mL O2 uptake/kg per min).
 Perioperative cardiac risk is increased in patients
unable to meet a 4-MET demand during most
normal daily activities.

Indicators of functional status :
 Can walk up a flight of steps = 4 METs
 Can do heavy work around the house such as
scrubbing floors or lifting or moving heavy
furniture = between 4 and 10 METs
 Can participate in strenuous sports such as
swimming, singles tennis, football, basketball
= = >10 METs

The type and timing of surgery significantly
affects the patient's risk of perioperative cardiac
complications.
 High-risk procedures - Rate of cardiac death
or nonfatal MI is > 5%
 Intermediate-risk procedures – 1% - 5%
 Low-risk procedures - < 1%

Perioperative myocardial infarction ppt

 Institutional and/or individual surgeon
experience with the procedure may increase
or lower the risk.
 Emergency surgery is associated with
particularly high risk (5 times) than with
elective procedures.

 Multivariable analyses, identified combinations of
factors, based upon routine clinical information
and laboratory tests, that used to estimate the risk
of cardiac complications.
 It was developed by Goldman, Detsky, and Eagle

 High-risk type of surgery ( vascular surgery and
open intraperitoneal or intrathoracic procedures)
 History of ischemic heart disease.
 History of HF.
 History of cerebrovascular disease.
 Diabetes mellitus requiring treatment with insulin.
 Preoperative serum creatinine >2.0 mg/dL (177
µmol/L).

Rate of cardiac death, nonfatal myocardial
infarction, and nonfatal cardiac arrest according to
the number of predictors.
 No risk factors - 0.4 %
 One risk factor - 1.0 %
 Two risk factors - 2.4 %
 Three or more risk factors - 5.4 %

RECOMMENDATIONS CLASS LEVEL
For patients with cardiac risk factor (s)
undergoing inter meadiate or high – risk
surgery
I B
For patients with cardiac risk factor (s)
undergoing low - risk surgery
IIa B
For patients with no cardiac risk factors
undergoing high / intermediate risk surgery
IIb B

RECOMMENDATIONS CLASS LEVEL
For patients with severe valvular heart
disease.
I C
In patients undergoing high-risk
surgery for LV assessment.
IIa C

RECOMMENDATION CLASS LEVEL
For patients with > 2 cardiac risk factors
undergoing high risk surgery
I B
For patients with < 3 cardiac risk factors
undergoing high risk surgery
IIb B
For patients undergoing intermediate risk
surgery
IIb C

RECOMMENDATION CLASS LEVEL
Acute STEMI / NON-STEMI /Unstable angina
Angina unresponsive to medical treatment
I A
Cardiac stable patients undergoing high risk surgery IIb B
Cardiac stable patients undergoing intermediate risk
surgery
IIb C

 Diagnosis complicated by lack of symptomatic
presentation in about half of patients with perioperative
MI.
Deveraux et al, proposed the following diagnostic criteria:
Rise in troponin (or fall after an elevated value) plus one or
more of following.
Ischemic signs or symptoms (e.g., SOB)
New pathologic Q waves on ECG.
New wall motion abnormality or fixed defect on echo.

BETA BLOCKERS
 Beta blockers have been used in patients undergoing
noncardiac sx, in those at high risk.
Possible mechanisms for such a benefit include
 Reduction in myocardial oxygen demand
 Increase in myocardial oxygen delivery due to
prolongation of coronary diastolic filling time.
 Prevention of fatal ventricular arrhythmias,
 protection against plaque rupture in the setting of
increased sympathetic activity .

 The large Perioperative Ischemic Evaluation (POISE)
trial reported increased mortality and, mostly in
association with hypotension in patients treated
with metoprolol.
 The evidence does not support the initiation of
prophylactic perioperative beta blocker therapy in
most patients undergoing noncardiac surgery (RCRI
≤2).
 POISE does not exclude benefit in high risk patients
(RCRI ≥3)

If beta blockers are used
 Beta-1 selective agent, begin as an outpatient up
to 30 days prior to operation, titrating to HR 50-60
BPM.
 Longer-acting agent (atenolol or bisoprolol) may
be more effective than shorter-acting agent
(metoprolol).
 Benefit was demonstrated when therapy was
begun one month before surgery.

Statins
 Recommend in those already being treated or with
other indications for treatment.
 There is no convincing evidence of benefit of
starting therapy in those patients who otherwise do
not meet accepted criteria for initiation of statin
therapy.

Aspirin
 The accepted practice is to discontinue aspirin 5 to
7 days before a surgical procedure to prevent
bleeding.
 Recent analyses suggest that there is only a mild
increase in the frequency of bleeding with aspirin
and no increase in mortality.
 Possible exceptions are intracranial and prostate
surgery.

 Two recent prospective randomized trials
(Coronary Artery Revascularization Prophylaxis
[CARP] and Dutch Echographic Cardiac Risk
Evaluation Applying Stress Echo [DECREASE] failed
to show such benefit.
 Revascularization prior to noncardiac surgery
should only be performed in patients who have
high-risk coronary anatomy that fulfill current
criteria applicable to all patients with coronary
disease.

 European Heart Journal (2009)
 British journal of Anaesthesia 107; 83-96 (2011)
 Up Todate 2011 (19.3)
 Medscape

Perioperative myocardial infarction ppt

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Perioperative myocardial infarction ppt