■ A normal ST segment represents early ventricular repolarization.
■ Displacement of the ST segment can be caused by various conditions listed below.
ST segment is at baseline.
ST segment is elevated.
ST segment is depressed. Primary Causes of ST Segment Elevation
■ ST segment elevation >1 mm in the limb leads and >2 mm in the chest leads indicates an evolving acute MI until there is proof to the contrary. Other primary causes:
♦ Early repolarization (normal variant in young adults)
♦ Ventricular aneurysm
♦ Pulmonary embolism
♦ Intracranial hemorrhage
Primary Causes of ST Segment Depression
■ Myocardial ischemia
■ Left ventricular hypertrophy
■ Intraventricular conduction defects
■ Reciprocal changes in leads opposite the area of acute injury
■ Occlusion of the left coronary artery — left anterior descending branch
■ ECG changes: ST segment elevation with tall T waves and taller-than-normal R waves in leads V3 and V4
y Clinical Tip: Anterior MI frequently involves a large area of the myocardium and can present with cardiogenic shock, second-degree AV block type II, or third-degree AV block.
■ Occlusion of the right coronary artery—posterior descending branch
■ ECG changes: ST segment elevation in leads II, III, and aVF
y Clinical Tip: Be alert for symptomatic sinus bradycardia, AV blocks, hypotension, and hypoperfusion.
Copyright'£'2005 F A Davis
| Lateral Myocardial Infarction
■ Occlusion of the left coronary artery—circumflex branch
■ ECG changes: ST segment elevation in leads I, aVL, V5/ and V6
y Clinical Tip: Lateral MI is often associated with anterior or inferior wall MI. Be alert for changes that may indicate cardiogenic shock or congestive heart failure.
■ Occlusion of the left coronary artery — left anterior descending branch
■ ECG changes: pathological Q waves; absence of normal R waves in leads V1 and V2
y Clinical Tip: Septal MI is often associated with an anterior wall MI.
Copyright'E'2005 F A Davis
1 Posterior Myocardial Infarction
■ Occlusion of the right coronary artery (posterior descending branch) or the left circumflex artery
■ Tall R waves and ST segment depression possible in leads V1,
■ ST segment elevation in true posterior leads, V8 and V9
V Clinical Tip: Diagnosis may require a 15-lead ECG because a standard 12-lead does not look directly at the posterior wall.
■ QRS predominantly negative in leads Vi and V2
■ QRS predominantly positive in V5 and V6 and often notched
■ Absence of small, normal Q waves in I, aVL, V5, and V6
■ Wide monophasic R waves in I, aVL, Vi, V5, and V6
Y Clinical Tip: Patients may have underlying heart disease, including coronary artery disease, hypertension, cardiomyopathy, and ischemia.
■ QRS normal or deviated to the right
y Clinical Tip: Patients may have underlying right ventricular hypertrophy, pulmonary edema, cardiomyopathy, congenital heart disease, or rheumatic heart disease.
This list is a reference list only. It is not meant to be exhaustive in clinical content.
Y Clinical Tip: Always consult an authoritative, current reference about dose, dilution, route and rate of administration, and interactions before administering medications, especially IV medications. Have a second licensed person independently check dose calculations, preparation, original orders, and infusion pump programming.
MCaiNlillsBUlMsS (Angiotensin-converting Enzyme Inhibitors) (Antihypertensive)
Common Agents: Captopril, enalapril, lisinopril, ramipril.
Indications: MI, hypertension (HTN), congestive heart failure (CHF), heart failure without hypotension, ST segment elevation, left ventricular dysfunction after MI.
Dose: See individual order and drug for route and dosage. Usually not started in emergency department, but within 24 hr after fibrinolytic therapy has been completed and blood pressure (BP) has stabilized.
Contraindications: Lactation, pregnancy, angioedema, hypersensitivity to ACE inhibitors, serum potassium >5 mEq/L.
Side Effects: Tachycardia, dizziness, headache, fatigue, hypotension, hyperkalemia.
Precautions: Reduce dose in renal failure.
(Adenocard, Adenoscan) (Antiarrhythmic) Indications: Narrow-complex tachycardias and PSVT Dose: 6 mg rapid intravenous push (IVP) over 1-3 sec followed by a 20-mL bolus of normal saline. Give 12 mg by IVP in 1-2 min if needed. A third dose of 12 mg IVP may be given in 1-2 min, max. 30 mg.
Contraindications: Hypersensitivity, sick sinus syndrome, 2nd-or 3rd-degree AV block (unless a functional artificial pacemaker is present), drug- or poison-induced tachycardia.
Side Effects: Flushing, dizziness, bronchospasm, chest pain or tightness, bradycardia, AV block, asystole, ventricular ectopic beats, VF.
Precautions: Ineffective in treating A-fib, A-flutter, or VT. Avoid in patients receiving dipyridamole and in patients with asthma or unstable angina.
FAMIWiTASWNIM (Cordarone, Pacerone) (Antiarrhythmic)
Indications: Wide- and narrow-complex tachycardia, polymorphic VT, shock-refractory Vf or pulseless VT, SVT, PSVT.
Dose: Cardiac arrest300 mg (diluted in 20-30 mL D5W) IVP; consider additional 150 mg IVP in 3-5 min. Wide- and narrow-complex tachycardia (stable) 150 mg IVP over first 10 min (15 mg/min) — may repeat infusion of 150 mg IVP every 10 min as needed; slow infusion of 360 mg IV over next 6 hr (1 mg/min); maintenance infusion of 540 mg over next 18 hr (0.5 mg/min). Max. cumulative dose: 2.2 g IV in 24 hr.
Contraindications: Bradycardia, hypersensitivity, cardiogenic shock, 2nd- or 3rd-degree AV block.
Side Effects: Vasodilation, hypotension, visual impairment, hepatotoxicity, pulmonary toxicity, CHF; may prolong QT interval, producing torsade de pointes.
Precautions: Avoid concurrent use with procainamide. Correct hypokalemia and hypomagnesemia if possible before use. Draw up amiodarone through a large-gauge needle to reduce foaming. For slow or maintenance IV infusion, mix medication only in glass bottle containing D5W and administer through an in-line filter.
ftraaiRIB (Acetylsalicylic Acid) (Antiplatelet)
Indications: Acute coronary syndrome, symptoms suggestive of cardiac ischemia.
Dose: 162-325 mg PO non-enteric coated for antiplatelet effect. Give within minutes of onset.
Contraindications: Known allergy to aspirin, pregnancy.
Side Effects: Anorexia, nausea, epigastric pain, anaphylaxis.
Precautions: Active ulcers and asthma, bleeding disorders, or thrombocytopenia.
MIROPIIlJ (Antiarrhythmic, Anticholinergic)
Indications: Symptomatic sinus bradycardia, asystole, PEA with rate <60 bpm, cholinergic drug toxicity and mushroom poisoning (antidote).
Dose: Cardiac arrest 1 mg IVP every 3-5 min (may give through endotracheal (ET) tube at 2.0-3.0 mg diluted in 10 mL normal saline, max. 0.03-0.04 mg/kg. Bradycardia 0.5-1.0 mg IVP every 3-5 min, max. 0.03-0.04 mg/kg.
Contraindications: A-fib, A-flutter, glaucoma, asthma.
Side Effects:Tachycardia, headache, dry mouth, dilated pupils, VF or VT
Precautions: Use caution in myocardial ischemia and hypoxia. Avoid in hypothermic bradycardia and in 2nd-degree (Mobitz type II) and 3rd-degree AV block.
I Ua EilUMIC^asS (Antihypertensive)
Common Agents: Atenolol, esmolol, labetalol, metoprolol, propranolol.
Indications: MI, unstable angina, PSVT, A-fib, A-flutter, HTN.
Dose: See individual order and drug for route and dosage.
Contraindications: HR <60 bpm, systolic BP <100 mm Hg, 2nd- or 3rd-degree AV block, left ventricular failure.
Side Effects: Hypotension, dizziness, bradycardia, headache, nausea and vomiting.
Precautions: Concurrent use with calcium channel blockers, such as verapamil or diltiazem, can cause hypotension. Use caution in patients with a history of bronchospasm or cardiac failure.
WAtCLUMICiUQRUE (Minerals/Electrolytes/Calcium Salt)
Indications: Hyperkalemia, hypocalcemia, hypermagnesemia; antidote to calcium channel blockers and beta blockers; given prophylactically with calcium channel blockers to prevent hypotension.
Dose: Hyperkalemia and antidote to calcium channel blocker 8-16 mg/kg (usually 5-10 mL) slow IVP, may be repeated as needed. Given prophylactically prior to IV calcium channel blockers 2-4 mg/kg (usually 2 mL) slow IVP.
Contraindications: Hypercalcemia, VF, digoxin toxicity, renal calculi.
Side effects: Bradycardia, asystole, hypotension, VF, nausea and vomiting.
Precautions: Incompatible with sodium bicarbonate.
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Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...