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Monday, February 16, 2009

Acute Coronary Syndrome: Drug Induced

Acute Coronary Syndrome: Drug Induced

Imbalance in myocardial blood supply and oxygen requirement
• Sympathomimetics are associated with myocardial oxygen mismatch due to induced vasoconstriction:
o Cocaine
o Cocaethylene is a toxic compound formed by hepatic transesterification of alcohol and cocaine further exacerbates the sympathomimetic effects of cocaine.
o Amphetamines (crank)
o Ephedrine (dietary supplement), pseudoephedrine (decongestant)
o Ma huang (herbal diet supplement)
o Dipivefrin (glaucoma eye drop)
o Phenylpropanolamine (nasal decongestant)
o Epinephrine
o Methylene 3,4 dioxymethamphetamine (ecstasy)
• Cocaine-induced chest pain also caused by:
o Increased myocardial workload
o Accelerated atherosclerosis
o Activation of platelets and promotion of thrombosis
• Antimigraine therapy—sumatriptan, methysergide, ergotamine, and isometheptene:
o Vasoconstrictors
o Particularly with cardiac risk factors or known coronary disease
• Calcium channel blockers—nifedipine:
o Reflex tachycardia and vasoconstriction
• Beta-blockers (metoprolol and propanolol):
o α-adrenergic mediated coronary vasospasm
• Carbon monoxide found with gas heaters, smoke inhalation, furniture stripping with methylene chloride:
o Decreasing oxygen-carrying capacity
o Shifting the oxyhemoglobin dissociation curve to the left
o Binding to myoglobin
• Bromocriptine:
o Vasoconstrictor
o Used for acromegaly, Parkinson disease, hyperprolactinemia, amenorrhea/galactorrhea, lactation cessation
o Risk increased by predisposing conditions:
 Pregnancy-induced hypertension
 Other vasospastic conditions (Raynaud disease or migraine headaches)
• Other dopaminergic agents (dopamine):
o Vasoconstriction and vasospasm
• Sildenafil:
o Vasodilatory properties
o Transient decreases in supine blood pressure
o Increase the risk of cardiac event during sexual activity
• Oral contraceptives:
o Prothrombotic
o Higher incidence of MI in young women with concomitant smoking
Signs and Symptoms
• Chest pain
• Substernal pressure
• Heaviness
• Squeezing
• Burning sensation
• Tightness
• Sympathomimetic toxidrome symptoms:
o Agitation
o Tremulousness
o Tachypnea
o Tachycardia
o Hypertension
o Hyperthermia
o Moist skin
o No urine retention
• Recent ingestion of medication/drug that induces coronary vasospasm
• Cardiac risk factors or known cardiac disease
Physical Exam
• Physical exam is usually unrevealing
• Blood pressure (BP) is usually elevated during symptoms
Essential Workup
History is critical in diagnosing and differentiating drug-induced and unusual causes of acute coronary syndromes.
• ECG:
o Normal approximately 50% of the time
o Compare to prior tracings
o New ST segment changes or T-wave inversions
o 1-mm depression of the ST segment below the baseline
o 80 msec from the J point
o Helpful in diagnosing other etiologies
• ECG in carbon monoxide poisoning:
o Premature ventricular contractions:
o Dysrhythmias
o Tachycardia
o Nonspecific ST-T wave abnormalities
o Acute MI: ST elevation or depression
• Serial cardiac enzymes
• Troponin may be more helpful.
• Creatine kinase may be elevated in cocaine-induced rhabdomyolysis
• Carboxyhemoglobin level for suspected carbon monoxide (CO) toxicity
• Serum toxicology screening
• Chest radiograph:
o Usually normal
o May show cardiomegaly
o Congestive heart failure
o May identify other etiologies of chest pain such as pneumonia
• Exercise stress testing: Identify underlying atherosclerosis.
• A technetium Tc-99m perfusion scan: myocardial damage/MI
• ECG: wall motion abnormalities
Diagnostic Procedures/Surgery
• Gold standard: cardiac catheterization
• Most patients will have angiographically normal coronary arteries.
Differential Diagnosis
• Anxiety
• Aortic dissection
• Biliary colic
• Costochondritis
• Esophageal reflux
• Esophageal spasm
• Herpes zoster
• Hiatal hernia
• Mitral valve prolapse
• Myocardial infarction
• Panic disorder
• Peptic ulcer disease
• Pneumonia
• Psychogenic
• Pulmonary embolus
• Unstable angina
Pre Hospital
• Remove patient from contaminated environment if carbon monoxide toxicity is a consideration.
• IV access
• Oxygen
• Cardiac monitoring
• Sublingual nitroglycerin for symptom relief
• All chest pain should be treated and transported as a possible life-threatening emergency.
• Avoid β-adrenergic antagonists in cases of suspected cocaine use.
Initial Stabilization
• Place patient on a monitor
• IV access should be obtained
• O2: 100% oxygen
• Nitrates

ED Treatment
• Aspirin
• β-adrenergic blockers should be avoided in patients who are suspected to have used cocaine.
• Benzodiazepines: cocaine use
• Reduce BP and heart rate.
• Decreasing myocardial oxygen demand
• Heparin or enoxaparin
• Thrombolytics: Use with caution in suspected vasospasm induces acute coronary syndrome
• Cardiac catheterization: diagnostic and/or therapeutic
• Carbon monoxide toxicity:
o 100% O2
o Hyperbarics if
o Carboxyhemoglobin level is >25–40%.
o Any period of coma
o Neurologic deficits
o Persistent metabolic acidosis
o Pregnant and carboxyhemoglobin level is >15%.
o Cardiac instability
o Acute MI, unless hemodynamically unstable
• Half-life of carboxyhemoglobin:
o Room air: 300 minutes
o 100% O2: 90 minutes
o Hyperbaric chamber at 3 ATM: 20 minutes
Medication (Drugs)
• Aspirin: 160-325 mg PO
• Enoxaparin (Lovenox): 1 mg/kg SC q12h
• Heparin: 80 units/kg IV bolus, then 18 units/kg/hr
• Labetalol: 20 mg IV or 100 mg PO
• Lorazepam: 1-2 mg IV
• Metoprolol: 5 mg IV q5min-q15 min followed by 25-50 mg PO starting dose as tolerated (note: beta-blockers contraindicated in cocaine chest pain)
• Morphine: 2 mg IV, may titrate upward in 2-mg increments for relief of pain assuming no respiratory deterioration and SBP >90 mm Hg
• Nitroglycerin: 0.4 mg sublingual
• Nitroglycerin: IV drip at 5-10 µg/min
• Nitropaste: 1-2 inches transdermal
• Tenecteplase: for 60-kg person, 30 mg; >60-69 kg, 35 mg; 70-79 kg, 40 mg; 80-89 kg, 45 mg, >90 kg, 50 mg given IV; or Reteplase, 10 units IV over 2 minutes, repeat in 30 minutes

Admission Criteria
• Similar to patients with acute coronary syndromes of atherosclerotic origin
• New-onset chest pain
• Rest chest pain
• Accelerated chest pain symptoms
Discharge Criteria
Chronic stable chest pain

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