Level 1

### Case #1

A 47-year-old man presenting for preoperative evaluation prior to knee arthroscopy.

What are the ECG findings?

This tracing demonstrates sinus rhythm at a rate of about 80 beats/min. The axis and intervals are normal. There is no evidence of chamber enlargement, hypertrophy, or ischemia. This is a normal ECG.

What ECG findings would concern you during a preoperative evaluation?

The preoperative ECG should first be assessed for any unstable cardiac conditions that would preclude elective surgery. These include active ischemia, ventricular tachycardia, or uncontrolled atrial arrhythmias such as rapid atrial fibrillation. Other findings of importance may include the presence of Q waves in a coronary distribution suggesting occult coronary disease and prior myocardial infarction, and chamber enlargement possibly suggesting occult valvular disease.

### Case #2

An asymptomatic 56-year-old gentleman presents for routine follow-up.

What abnormalities are present on the ECG?

There is sinus rhythm at 66 beats/min. The axis is deviated leftward, evidenced by the positive QRS complex in lead I and the negative QRS complex in leads II and aVF. This left-axis deviation is associated with small q waves and large R waves in leads I and aVL, and small r waves and large S waves in the inferior leads. There is no evidence of left ventricular hypertrophy or other chamber abnormalities. There are no pathologic Q waves suggesting prior infarction, and no ST-segment or T-wave abnormalities. The presence of leftward axis deviation in the absence of left ventricular hypertrophy or prior infarction with this pattern of qR complexes in leads I and aVL and rS complexes in the inferior leads is consistent with left anterior hemiblock, also known as left anterior fascicular block. Recall that the His bundle bifurcates into the left and right bundle branches. The left bundle branch further branches into the left anterior fascicle and the left posterior fascicle. Block in the left anterior fascicle is more common than block in the left posterior fascicle. Hypertension, ischemic heart disease, cardiomyopathy, and degenerative conduction system disease of the elderly (Lev's syndrome) are all associated with left anterior hemiblock. The QRS duration is normal when left anterior hemiblock alone is present, although a delayed intrinsicoid deflection (the duration between the onset of the QRS and the peak of the R wave) of greater than 45 milliseconds should be observed in lead aVL as is present in this case.

What is the differential diagnosis for left-axis deviation?

Left-axis deviation can be associated with left anterior hemiblock (as in this case), left ventricular hypertrophy, prior myocardial infarction, Wolff-Parkinson-White ...

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