TEST D

D-1

NARRATIVE INTERPRETATION

Abnormalities

Broad, notched QRS complex with ST depression and T-wave inversion leads I, aVL, V4–V6.

Synthesis

Sinus rhythm. Left bundle branch block with associated ST-T wave abnormalities.

TEST ANSWERS

1, 74, 104.

Comment: Most individuals with LBBB have underlying cardiovascular disease. One study of 25,522 patients who underwent cardiac catheterization found 550 with LBBB. The most common diagnoses in patients with LBBB were coronary heart disease (49 percent), valvular and congenital heart disease (9 percent), cardiomyopathy (8.5 percent), and hypertension (8 percent). In this angiographic study, 12 percent of patients had no demonstrable cardiovascular abnormalities.

FURTHER READING

Clinical History

An 89-year-old asymptomatic woman.

D-2

NARRATIVE INTERPRETATION

Abnormalities

Heart rate less than 60 bpm. APC followed by second premature complex and sinus pause. AV junctional escape complexes (rhythm). ST depression leads V4–V5. T-wave inversion leads II, III, aVF, V4–V6.

Synthesis

Sinus bradycardia. APC with probable reciprocal (echo) complex. Sinus pause with AV junctional escape complexes (rhythm). Period of isorhythmic AV dissociation on rhythm strip. Nonspecific ST-T-wave abnormalities.

TEST ANSWERS

3, 7, 10, (22), 24, 53, 54, 106.

Comment: When first looking at the rhythm strip, one could easily mistake this rhythm as a wandering atrial pacemaker to the AV junction. This is probably not the case. The more likely mechanism is explained by an intrinsic rhythm of sinus bradycardia at a rate of 50 and junctional escape complexes. Note the atrial premature in the fifth complex of the tracing, followed by a reciprocal, "echo" beat. The sinus node is depolarized in a retrograde fashion and is temporarily suppressed. A subsidiary pacemaker in the AV junction then takes over until the sinus pacemaker recovers and regains control. A period of isorhythmic AV dissociation is evident on the rhythm strip where the P waves and QRS complexes occur in close proximity, but are unrelated.

Clinical History

A 68-year-old asymptomatic man.

D-3

NARRATIVE INTERPRETATION

Abnormalities

Axis rightward of +90 degrees. qR pattern V1. R-wave voltage less than 3 mm leads V1–V3. T-wave inversion leads II, ...