ECG Review

A 73-Year-Old Man with Dyspnea

By Ken Grauer, MD

Figure. 12-lead ECG obtained from a 73-year-old man with dyspnea.

Clinical Scenario: The 12-lead ECG in the Figure was obtained from a 73-year-old man with dyspnea. What ECG findings do you see that may account for his symptoms?

Interpretation/Answer: The underlying regular rhythm is interrupted every third or fourth beat. The frequency of this interruption is easy to overlook unless one pays careful attention to QRS morphology in each of the 12 leads. For example, beats #3, 6, and 9 do not look much different from the normal beats in leads III, aVL, and aVF. However, it is obvious that something different is occurring for beat #3 from inspection of leads I and II, and equally obvious from lead aVR that beats #6 and 9 are different. We suspect that the reason QRS morphology is not that different for many of these interrupting beats, is that these widened and only slightly early occurring complexes are fusion beats, produced by near simultaneous occurrence of PVCs (premature ventricular contractions) with the underlying rhythm.

The question remains as to what the underlying rhythm is. The answer almost always can be found in the relative pause that follows the slightly early occurring, abnormal-looking beats. Thus, in leads I and II, a subtle but real notch is seen immediately after the abnormal-looking QRS complex (beat #3). Careful inspection of the baseline in lead I reveals small amplitude but repetitive notching at a regular interval of approximately one large box (corresponding to a rate of 300/minute). Stepping back to look at the ECG from a short distance should now allow appreciation of the underlying "sawtooth" pattern of the baseline in leads II, III, and aVF. Thus, the rhythm is atrial flutter with 2:1 AV conduction, with frequent interruption by PVCs that produce fusion beats. The marked left axis (net negativity of the QRS complex in lead II) suggests LAHB (left anterior hemiblock). Additional findings of relatively low QRS voltage, R wave greater than S in lead V1, and S waves in all precordial leads are consistent with the pulmonary disease (and possible right ventricular hypertrophy) that this patient had, which together with his tachyarrhythmia were responsible for his symptoms of acute dyspnea.