1. Which of the following is the earliest EKG finding in acute MI?
A. hyperacute T waves
B. ST elevation
C. ST depression
D. T wave inversion
E. Q wave
2. Which of the followingis true regarding pediatric EKG analysis?
(A) Left axis deviation is normal in healthy neonates.
(B) Atrial fibrillation is the most common pediatric dysrhythmia.
(C) T-wave inversion in the anterior precordial leads (V1–V3) is a normal finding in school-aged children.
(D) Cardiac dysrhythmias are the most common electrocardiographic manifestation of underlying congenital heart disease.
(E) ST elevation is most commonly associated with myocardial injury.
3. Which of the following is useful as a sensitive screening test for clinically significant complications of blunt cardiac injury?
(A) Creatine kinase, MB isoenzyme (CK–MB)
(B) Troponin I
(C) Troponin T
(E) Exercise stress test
4. What is the most common dysrhythmia in hypothyroid cardiovascular disease?
(A) Atrial fibrillation
(B) Long QT syndrome
(C) Junctional escape rhythm
(D) Sinus rhythm with left or right bundle branch block
(E) Sinus bradycardia
5. When beta-blocker therapy is contraindicated, which of the following calcium channel blockers (CCBs) can be given as a substitute in case of NSTEMI?
(E) All of the above
1. Answer A. The temporal sequence of EKG morphologies in acute MI is generally hyperacute T waves, ST elevation, T-wave inversion, and Q waves. Hyperacute T waves may also be seen in hyperkalemia and (along with ST elevation) in benign early repolarization,acute pericarditis, and left ventricular hypertrophy. ST elevation may also be seen in bundle branch block and ventricular aneurysms. The evolution in the preceding sequence in the appropriate clinical setting usually points to STEMI. This is a strong argument for performing repeated EKGs in the evaluation of acute coronary syndrome in the ED.
2 .Answer C. T-wave examination has limited utility in pediatric EKG analysis. Upright T waves in the anterior precordial leads (V1–V3) are normal in the neonate, but they invert after the first week of life and remain inverted until early adolescence, at which time they take on the typical adult, upright appearance.
3. Answer D. Any abnormality on the EKG in the setting of blunt trauma should prompt further work up and evaluation, along with admission to the hospital.
4. Answer E. The most common dysrhythmia in hypothyroid cardiac disease is sinus bradycardia. Cardiomegaly and depressed cardiac contractility are other manifestations.
5. AnswerB. The majority of CCBs used in human pharmacology are dihydropyridines, which are relatively vascular selective with minimal effects on cardiac contractility and conduction. In contrast, verapamil and diltiazem are nondihydropyridines and are less potent vasodilators with more pronounced depressive effects on cardiac contractility and conduction. The use of beta-blockers in patients with NSTEMI is a class I recommendation due to their demonstrated benefit in reducing mortality among patients with acute myocardial infarction. This is primarily based on their ability to limit myocardial oxygen demand by reducing the heart rate as well as the force with which the heart contracts. In patients who are unable to tolerate beta-blockers, nondihydropyridine CCBs, such as verapamil or diltiazem, can be used instead. Each of the other listed CCBs is a dihydropyridines with limited cardiac effects. Nimodipine has a specific affinity for the cerebral vasculature and is used clinically only in patients with subarachnoid hemorrhage to limit vasospasm.