7.10: Acute Coronary Syndromes
- Page ID
- 59713
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Acute coronary syndrome includes unstable angina, non-ST segment elevation (non-Q wave) myocardial infarction and ST segment elevation (Q wave) myocardial infarction. Q wave infarction involves the entire thickness of the myocardial wall; non-Q wave infarction involves only the subendocardial portion of the myocardial wall. These syndromes are associated with an increased risk of death.Acute coronary syndromes are commonly caused by platelet aggregation and thrombus formation at a site where an atherosclerotic plaque in an epicardial artery has ruptured. The changes in blood pressure and heart rate that may occur in the perioperative period may predispose to plaque rupture and the hypercoagulable state may predispose to thrombus formation.
Diagnosis
The diagnosis of acute coronary syndrome includes:
- Angina unresponsive to nitrate treatment
- ST segment elevation
- T wave inversion
- New onset left bundle branch block
- Biochemical markers (may be normal during the first 6 hours)
Management
If the anesthetist suspects the patient has an acute coronary syndrome they must:
- Declare an emergency and call for help.
- Give 100% oxygen and check that the patient is ventilating.
- Check the blood pressure and pulse rate and optimize the blood pressure and pulse (as for myocardial ischaemia).
- Terminate the surgery as soon as possible.
- Give aspirin and beta-blockers if there are no contraindications.
- Obtain a 12 lead ECG and blood test for biochemical markers.
- Organize an urgent consultation with a cardiologist to evaluate the patient for reperfusion (if available).
- Be prepared to treat cardiac arrest or arrhythmias.
Ideally patients should have a 12 lead ECG and blood tests for biochemical markers of myocardial cellular damage (Troponin, CK-MB). If there is ST segment elevation unresponsive to medical treatment or elevation of the biochemical markers the optimal treatment may be reperfusion by thrombolysis, percutaneous transvenous coronary angioplasty or coronary artery bypass grafting. Thrombolysis is contraindicated after recent surgery because of the risk of bleeding.
If reperfusion is not available then the patient’s blood pressure and heart rate must be controlled. They should receive oxygen and be nursed in a high dependency/coronary care unit. They will benefit from aspirin and beta-blockers that both reduce the risk of myocardial infarction and the risk of death after a myocardial infarction.