Acute coronary syndrome

A. Presentation

Symptoms

• Chest discomfort, with radiation to the back, jaw, or left arm. (Resting or nitroglycerin relieves angina, but not so much in MI.)
• Dyspnoea
• Sweating
• Apprehension and sense of impending doom (anxiety)
• Nausea and vomiting

Signs

• S4 (almost universal)
• Soft systolic apical murmur (if papillary muscle dysfunction)
• Friction rubs on day 2 or 3 (Friction rubs within a few hours of the onset might suggest pericarditis rather than MI)

Medical emergency if history of:

• Rest of prolonged chest discomfort (>10min, not relieved by sublingual nitrates); OR
• Recurrrent chest discomfort; OR
• Discomfort associated with syncope or heart failure

B. Investigation

Baseline tests

• ECG (within 5 minutes)
• Serum cardiac troponin (I or T) level (or serum CK-MB level if troponin testing is not available)
  ---> repeat in 6 hours if the baseline normal.
• Full blood count
• Serum creatinine
• Electrolyte
• Serial serum CK levels (for 48 hours to provide baseline and allow detection of second infarction)
• Serium lipid levels (within 24 hours of the onset)
• Blood glucose level
• Chest Xray

Other tests

Coronary angiography

- for all high risk and selected intermediate risk patients.

Stress exercise tests (stress radionuclide or stress echocardiography or exercise ECG)

- for intermediate patients who has had normal baseline ECG and normal troponin at baseline and 6 hours.

C. Treatment

Initial management of all patients

Rest and take aspirin 300mg

Also take a short acting nitrate (e.g. glyceryl trinitrate)

Pain relief with morphine

Early management of all patients

• ECG performed immediately
  If ST elevation or left bundle block -> reperfusion.
• Oxygen (watch out for COPD patients underventilating)
• Aspirin 300mg (if hasn't been given already)

• GTN (Glyceryl trinitrate) 600mg sublingual (if SBP>95)
• Morphine 2.5mg-5mg IV PRN

If chest pain persist, move to high risk patient management.

If chest pain disappears, perform risk stratification.

Management of low risk patient

Be referred for cardiac assessment within 2 weeks.

Patient should be given aspirin and beta-blockers.

If beta-blocker is contraindicated

--> diltiazem or verapamil (Non-dihydropyridin calcium channel blockers) instead

(but never together with beta-blocker)

Patient should be provided with buccal nitroglycerine and instructed in its use.

Management of intermediate risk patient

Observation of at least 6-8 hours, during which they would be reclassified into either low or high risk and manage accordingly.

If troponin was still normal at 6 hours, do stress test to reclassify.

If troponin was elevated or abnormal stress test -> Patient becomes high risk, otherwise low risk.

Management of high risk patient (unstable angina or MI)

Acute medical management

• Aspirin
• Beta-blocker
• LMW heparin
  (if it fails or if surgery planned, give IV tirofiban and unfractionate heparin instead)

If chest pain persist with the above 3 medication:

• Switch to tirofiban/heparin
• Consider using amlodipine or long-acting nifedipine
• Nitrate therapy and morphine to maximum
• Consider GTN infusion (see "reperfusion therapy")

Invasive procedure (all high risk patient)

Plan in very near future:

• Coronary angiography AND
• Percutaneous coronary intervention (i.e. ballooning +/- stenting) PCI or coronary artery bypass grafting (CABG).

Reperfusion therapy

Includes thrombolytic therapy and emergency invasive procedure.

Long term management of all patients

• Continue aspirin and beta blockers
• ACE-inhibitors should be considered, particularly if hypertension, heart failure, or diabetes is present.
• Statin therapy should commence during hospital admission for all patients with unstable angina or non-ST elevation myocardial infarction.
• Use calcium-channel blockers only if beta-blocker is contraindicated.
• Nitrate (to relief pain and to prevent pain prophylactically)

All patients with a diagnosis of unstable angina or myocardial infarction should be referred to an appropriate cardiac rehabilitation and prevention program, as well as to the GP for counselling and risk factor management.

Management of stable angina

• Nitrate (to relief pain and to prevent pain prophylactically)
• Aspirin
• Beta-blocker

Calcium channel blocker

If beta-blocker is not enough, add a dihydropyridine calcium channel blocker (e.g. amlodipine, felodipine).

If beta-blocker is contraindicated (and thus not used), substitute a long-acting non-dihydropyridine calcium channel blocker (e.g. diltiazem, verapamil).

NB: Tolerance to all forms of nitrate therapy develops rapidly. Allow a nitrate-free period. (e.g. patches worn for less than 16 hours per day).

D. Other notes

[epidemilogy/risk factors/
causes/mechanisms/compications/ddx/
classification/staging/
followups/prognosis/prognostic factors/prevention]

Simplified risk-assessment algorithm

Pain, but not at rest, repetitive, prolonged, and no ECG or troponin changes

---> low risk

---> <2% 6-month risk of death from MI

Pain at rest, repetitive, or prolonged, but no ECG or troponin changes

---> intermediate risk

---> 2-10% 6-month risk of death from MI

Pain at rest, repetitive, or prolonged, AND ECG or troponin changes

---> high risk

---> >10% 6 month risk of death from MI

Risk stratification of unstable angina

Very high risk features

• Heart failure
• Mitral regurgitation
• Extra heart sound

High risk features

• Prolonged (>10min) chest discomfort and ongoing
• ST changes or deep T wave inversion in 3 or more leads
• Elevated cardiac enzymes (esp troponin)
• Associated syncope
• Associated haemodynamic instability (systolic blood pressure <90mmHg, cool peripheries, diaphoresis)

Intermediate risk features

• Prolonged but resolved chest discomfort
• Nocturnal pain
• New onset grade III or IV chest pain in the previous 2 weeks
• Age > 65 years
• History of MI or revascularisation
• Pathological Q wave
• No significant (<0.5mm) ST deviation, or minor T wave inversion in less than 3 leads.

Low risk features

• Increased angina frequency or severity
• Angina provoked at a lower threshold
• New onset angina more than 2 weeks before presentation
• Normal ECG and negative serum troponin
• No high or intermediate risk features

Q wave vs non-Q wave

Traditionally the distinction between Q wave (transmural) and non-Q wave (subendocardial) infarction are made.

Q wave infarction has been proven to benefit from thrombolytic therapy while non-Q wave infarction has not.

Q waves may take days to develop.

Non-Q wave infarct is management as per unstable angina.

ST depression of 1mm and 0.5mm have the same prognostic value.