Unstable Angina Management

 

NSTEMI & Unstable Angina Management

 

—  NSTEMI or EKG changes suggest ischemia with high risk:

¡ Aspirin

¡ Beta blocker

¡ Nitrates

¡ Heparin (UFH or LMWH)

¡ ACE-I/ARB

¡ Statin

¡ Consider GP IIb/IIIa inhibitor and clopidogrel

—  EKG normal or non-specific changes with intermediate or low risk:

¡ Rule out ACS with 3 sets of troponin, EKG

¡ Consider pre-discharge stress test

 

Early Treatment

q MONA

•         Morphine- for analgesia

•         Oxygen- sPO₂ >94%

•         Sublingual nitroglycerin

•         Aspirin, 160 to 325 mg

•         Clopidogrel

•         Adjunct therapy

 

Acute MI:  Outcome

•         Outcome after acute myocardial infarction is a function of vessel patency rate and time from occlusion to reperfusion

•         Benefits of Rapid Reperfusion

–        Decreased mortality

–        Decreased morbidity

–        Increased myocardial salvage

–        Increased left ventricular function

 

•         Preferred therapy if performed in a timely fashion by skilled individuals in high-volume centers

•         Reperfusion strategy in patients with risk of bleeding contraindications to thrombolytic therapy

Acute MI:  Thrombolysis

•         Benefit greatest if therapy initiated early

•         Highly significant reduction in mortality

•         Benefits patients irrespective of age, gender, and comorbid conditions

•         Slightly increased risk of intracerebral hemorrhage

•         Candidates

Ø Time to therapy 12 hours or less

Ø Acute ST-segment elevation

Ø Symptoms consistent with acute MI and presence of Left Bundle Branch Block

Ø Patients without ST-segment elevation should not receive thrombolytic therapy

Thrombolytic Therapy

 

Contraindications

•         Active bleeding

•         Recent major trauma/surgery in 3 weeks

•         Recent GI bleed in 1 month

•         Ischemic stroke within 6 months

•         Haemorrhagic stroke at any time

•         Markedly elevated blood pressure

•         Significant bleeding diathesis

•         Pregnancy or post partum

 

Thrombolytic Agents

•         Nonspecific agents deplete coagulation factors

            A.  Streptokinase

            B.  Anistreplase

            C.  Urokinase

•         Specific agents do not deplete coagulation factors

            A.  Alteplase (tPA)

            B.  Reteplase

 

Thrombolytic Agents:
Comparative Pharmacologic Features

     Feature                     SK         APSAC       UK       SCUPA      rtPA

Half-Life (min)                 18             90           20             7              5

Fibrin-Selective                +               +           ++         ++++          +++

Duration of

  Infusion                    60 min        2-5 m      5-15 m    Hours      Hours

Antigenicity                    Yes           Yes          No          No?        No?

Incidence of

  Reperfusion (%)         60-70         60-70      60-70       60-70       60-70

Frequency of

  Reocclusion (%)           15              10            10           NA           20

Fibrinogenolysis          ++++          ++++        +++          ++            ++

Platelet Activation         +++            +++           0             ?           ++++

Acute MI
Adjunct Drug Therapy

 

Aspirin

•         Inhibition of Thromboxane A2 formation

•         Blockage of platelet aggregation and thrombus propagation

•         Prevention of coronary re-occlusion after successful thrombolysis

•         Potential Benefits

Ø Mortality decreased 23%

Ø Non-fatal MI decreased 44%

Ø Non-fatal stroke decreased 46%

Ø 42% reduction in mortality when added to Streptokinase

 

Heparin

•         Post thrombolytic therapy, heparin administration based more on current practice than on evidence

•         Intravenously in patients receiving alteplase/retaplase

•         Subcutaneously in all patients not treated with thrombolytic therapy

•         Should be used in large AWMI or in patients with LV mural thrombus to reduce risk of stroke

•         Potential Benefits

Ø Prevention of venous thrombosis

Ø Decrease left ventricular mural thrombus

Ø Decrease arterial embolization

Ø Decrease re-infarction or extension of infarct

 

Beta Blockers

•         Patients without contraindications should receive intravenous beta blockers when acute infarction is suspected, followed by oral agents when they are hemodynamically stable

•         All patients within 12 hours of myocardial infarction

•         Continuing or recurrent ischemic pain

•         Tachyarrhythmias

•         Potential Benefits

Ø 13% reduction in mortality in the pre-thrombolytic trials

Ø Reduce chest pain

Ø Reduce myocardial-wall stress

Ø Reduce infarct size

 

Contraindications

•         Bradycardia

•         Second- or third-degree AV block

•         Hypotension

•         Clinical evidence of congestive heart failure

•         Cardiogenic shock

•         Active bronchospasm

 

Nitrates

•         Intravenously for first 24 to 48 hours

            A.  Acute MI and CHF

            B.  Large anterior infarction

            C.  Persistent ischemia

            D.  Hypertension

•         Beyond 48 hours in patients with recurrent angina or persistent pulmonary congestion

•         Potential Benefits

Ø Primary action is vasodilation

Ø May increase myocardial perfusion

Ø May increase peri-infarct ischemia

Ø Systemic arterial vasodilation decreases blood pressure and decreases myocardial oxygen demand

Ø Increased venous capacitance decreases preload

 

ACE Inhibitors

 

•         Potential Benefits

Ø Mortality benefit when administered within 24 hours of MI

Ø Systemic and coronary vasodilation may:

Ø             A.  Reduce peri-infarct ischemia

Ø             B.  Limit infarct expansion

Ø             C.  Prevent early remodeling

Ø May have some antithrombotic properties 

 

Calcium Channel Blockers

 

•         Reduce angina

•         Reduce blood pressure

•         Reduce coronary spasm

•         No reduction in mortality

•         Short-acting nifedipine may increase mortality (TRENT, SPRINT II)

Ø Not recommended as standard first-line therapy

Ø May be used for significant hypertension or refractory ischemia

 

Rhythm Disturbances
Atrial Fibrillation

 

•         Electrical cardioversion for unstable patients (ischemic chest pain, hypotension, congestive heart failure)

•         Slow the ventricular response:

            A.  IV Digitalis

            B.  IV Beta Blockers

            C.  IV Diltiazem or Verapamil

Post discharge Care

A – Antiplatelets & Antianginals

B – Beta blocker, Blood pressure control

C – Cholesterol lowering, Cigarettes cessation

D – Diabetes control, Diet

E – Education & Exercise

 

Thrombolytic drugs

•         Depletion of fibrinogen, reduction in factor II, V, and VIII levels, impairment of platelet aggregation, and the appearance of fibrin split products.

•         If surgery is required for persistent ischemia after failed thrombolytic therapy, it should be delayed by at least 12–24 hours.

•         If it is required emergently, plasma and cryoprecipitate will probably be necessary to correct the anticipated coagulopathy.