TEST C

C-1

NARRATIVE INTERPRETATION

Abnormalities

Rapid heart rate with “sawtooth” configuration. Possible superimposed ST depression, leads II, II, aVF, V6.

Synthesis

Atrial flutter with 2:1 AV conduction. (Nonspecific ST abnormalities.)

TEST ANSWERS

19, 50, (106).

Comment: Atrial flutter may be divided into type I (classic) or type II (very rapid). This tracing demonstrates classic atrial flutter with characteristic sawtoothed flutter waves in leads II, III, and aVF. In type I flutter, the atrial rate is between 240 and 340 bpm and may be interrupted with rapid atrial pacing. Type II atrial flutter is characterized by very rapid atrial rates of 340 to 433 bpm and cannot be controlled by atrial pacing.

It is appropriate to describe the 2:1 ratio of atrial to ventricular impulses as 2:1 AV conduction rather than block. The 2:1 conduction is a physiologic response of the AV node and should not imply a pathologic state, or heart block. Atrial flutter with 1:1 conduction may occur rarely from sympathetic stimulation or when antiarrhythmic agents slow the intrinsic atrial rate. Atrial flutter with 1:1 conduction can be a cardiac emergency because the resulting extremely rapid ventricular rate prevents physiologic cardiac filling and contraction.

It is difficult to exclude the presence of ST abnormalities superimposed on the flutter waves in this example.

Clinical History

A 55-year-old woman with palpitations.

C-2

NARRATIVE INTERPRETATION

Abnormalities

APC. APC conducted aberrantly. ST depression leads I, II, III, aVL, aVF, V4–V6. T-wave inversion leads I, aVL, V4–V6. S wave lead V2 + R wave lead V5 greater than 35 mm. R wave aVL + S wave V3 greater than 20 mm in a woman. Abnormal P terminal force V1.

Synthesis

Sinus rhythm. APCs with normal and aberrant conduction. LVH by voltage criteria. Associated ST-T-wave abnormalities. Left atrial abnormality.

TEST ANSWERS

1, 10, 11, 60, 78, 103.

Comment: This tracing demonstrates a number of findings, most of them related to LVH. A potential pitfall would be characterizing the wide complexes beats as ventricular in origin rather than as an aberrantly conducted atrial complexes. On close examination, a P wave is clearly seen to be deforming the preceding T wave, indicating that the complex is supraventricular. A normally conducted atrial premature complex is seen on the rhythm strip.

The configuration of the ST-T-wave abnormalities suggests they were most likely on the basis of LVH, rather than myocardial ischemia.