or nitroglycerin. It is generally treated with CCBs. Patients with Prinzmetal
angina may have ST elevations on their ECG that is indistinguishable from an
acute MI. (b)Stable angina is described as transient episodic chest discomfort
resulting from myocardial ischemia. The discomfort is typically predictable
and reproducible, with the frequency of attacks constant over time. The dis-
comfort is thought to be caused by fixed, stenotic atherosclerotic plaques that
narrow a blood vessel lumen and reduce coronary blood flow (d and e).
Non–ST-elevation MI (NSTEMI) and ST-elevation MI (STEMI) results from
myocardial necrosis with release of cardiac biomarkers (eg, troponin).
44.The answer is b.(Tintinalli, p 194.)The rhythm strip shows second-
degree AV block type II or Mobitz type II.Mobitz II presents with a pro-
longed PR interval (PR > 0.2 seconds) and random dropped beats (ie, P wave
without QRS complex). The PR intervals are always the same duration. The
block is below the level of the AV node, generally the His-Purkinje system.
This heart block reflects serious cardiac pathology and may be seen with an
anterior wall MI, which is the case with this patient.
Mobitz type I (a)(also called Wenckebach phenomenon) shows pro-
gressive prolongation of PR interval with each beat until AV conduction is
lost causing a dropped beat. First-degree AV block (c)presents with pro-
longed PR interval (PR > 0.2 seconds) without loss of AV conduction. This
block is asymptomatic. Atrial flutter (d)is a tachydysrhythmia with rapid
atrial beat and variable AV block. It has a characteristic “sawtooth” appear-
ance of atrial flutter waves. Sinus bradycardia (e)is similar to sinus rhythm
except that the rate is less than 60 and generally greater than 45. There are
several etiologies of sinus bradycardia; some are normal (eg, young person,
well-trained athlete) and some pathologic (eg, β-blocker overdose, cardiac
ischemia).
45.The answer is e.(Tintinalli, p 194.)The rhythm strip findings are con-
sistent with third-degree AV block,also called complete heart block.It is
characterized by absent conduction through the AV node, resulting in the
dissociation of atrial and ventricular rhythms. The ECG shows indepen-
dent P waves and QRS complexes. Mobitz type II often progresses to third-
degree heart block, as seen in this case. The immediate step in managing
complete heart block is applying a transcutaneous pacemakerfor ventric-
ular pacing as a temporizing measure. However, patients need implantable
ventricular pacemakersfor definitive management. In addition, the under-
lying cause of the block needs to be addressed.
Chest Pain and Cardiac Dysrhythmias Answers 47