ECG Review
How Many PVCs?
By Ken Grauer, MD, Professor, Assistant Director, Family Practice Residency Program, University of Florida. Dr. Grauer reports no financial relationship to this field of study.
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Figure. 12-lead ECG obtained from a 47-year-old woman with palpitations. |
Clinical Scenario: The 12-lead ECG in the Figure was obtained from a 47 year old woman with palpitations. How many PVCs (premature ventricular contractions) do you see? Is there ECG evidence of acute ischemic change on this tracing?
Interpretation/Answer: The ECG in the Figure shows simultaneous recording of 3 leads at one time (leads I, II, III; aVR, aVL, aVF; V1, V2, V3; and V4,V5,V6 are each recorded at the same instant in time). Thus, there are a total of 13 beats on the tracing. None of these are PVCs.
The underlying rhythm in the tracing is sinus, as evidenced by the upright P wave in lead II (seen preceding beats #1 and 3). Beats #2, 8, and 13 look different. These beats are early and widened, however they are not PVCs. Instead, each of these beats is preceded by a premature P wave that peaks the preceding T wave (best seen in the preceding T wave of beat #1 in lead II and beat #12 in lead V5. Thus, beats #2, 8, and 13 are PACs (premature atrial contractions) that are conducted with aberration.
Note the slight pause following beat #10. Close inspection of the T wave of beat #10 with the T wave of normally conducted beat #9 confirms a slight change in shape that results from the deformity produced by the PAC. This PAC in the T wave of beat #10 occurs so early that it is blocked (ie, not conducted to the ventricles). Thus, the patient in this case has normal sinus rhythm with very frequent PACs, some of which are conducted with aberration, and some of which are blocked. Her 12-lead ECG otherwise shows early transition (between leads V1-V2) in the precordial leads, and some non-specific ST-T wave changes that do not appear to be acute. Assessment of ST-T wave morphology in patients such as this who have frequent ectopy can be tricky, as one has to be very careful not to include ST segments of the ectopic beats or of beats with T waves deformed by PACs in one’s analysis. In addition, the ST segment of beats immediately following a PAC or PVC may sometimes manifest ST-T wave changes that are not necessarily reflective of underlying ischemia. For the tracing shown here, assessment of ST-T wave changes is therefore problematic, and can confidently be made only for the ST segments of beats #4, 5, 6. That said, it is unlikely that the ST segment flattening and slight T wave inversion seen in beats #3, 9, and 11 in various leads is indicative of acute ischemic change.
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