The correct answer is (B). The myocardium is the actual muscle layer of the heart, and it is the part of the heart that is damaged during a heart attack. The epicardium (A) and endocardium (C) are fibrous layers that are not generally damaged during a heart attack.
The correct answer is (D). The ECG shows ST segment elevation in leads II, III, and aVF, which indicates an inferior wall MI. The RCA services the inferior wall of the heart in most of the population.
The correct answer is (A). The mitral valve is the valve between the left atrium and the left ventricle. During systole, this valve ordinarily prevents backflow of blood from the left ventricle into the left atrium. This is not the case in mitral valve regurgitation.
The correct answer is (B). When myocytes are polarized just prior to contraction, the resting potential is approximately -90 mV. During contraction, the myocytes depolarize, which means the potential becomes approximately 0 mV. This means that the cell potential has become more positive.
The correct answer is (C). First-degree heart block (A) would not typically drop a complex after a P wave. Second-degree heart block, Mobitz type I (B) does not have a consistent PR. Sinus arrest (D) would drop the entire complex, including the P wave, not just the QRS complexes.
The correct answer is (C). Intubation attempts in patients with a pulse often can lead to a bradycardic rhythm because of stimulation of the vagus nerve. Administration of a parasympatholytic such as atropine should be the next step. Fluid (B) will not improve the situation. Epinephrine (D) is a little too aggressive a treatment for this. CPR (A) could be appropriate in a child but not an adult.
The correct answer is (A). The rhythm is SVT, and the low blood pressure combined with mentation changes illustrated by the syncope and ongoing dizziness indicate that the rhythm is hemodynamically unstable. The initial treatment for this is synchronized cardioversion at 50–100J. (B) is correct for a wide, complex tachycardia. If the rhythm was stable and not associated with hypotension or mentation changes, then (C) would be correct, followed by (D) if not successful.
The correct answer is (D). Magnesium sulfate is the definitive treatment for torsades de pointes or polymorphic VT. Treatment with amiodarone (A) and epinephrine (C) are secondary to magnesium because polymorphic VT is refractory to treatments typically used with monomorphic VT. Calcium chloride (B) is a tertiary treatment in cases that may have resulted from hyperkalemia.
The correct answer is (B). The QRS up in lead I and down in lead aVF indicates a left axis deviation and the RSRʹ pattern in lead V1 indicates a right bundle branch block.
The correct answer is (C). Although the rhythm is a bradycardic rhythm, because there is no pulse, pacing is not an appropriate treatment. Once pulses return, pacing can then be an option.