A woman in her 60s with palpitations

Conclusion:The final tracing in Today ' s Case was obtained the day after the run of ATach that was caught on Telemetry. I found it interesting to compare this last ECG #4  — with the post-cardioversion ECG #2  — and then with QRS morphology in selected leads during full preexcitation that was seen in ECG #1 (these 3 tracings put together in Figure-4):Sinus rhythm is again present in ECG #4 (RED arrows in lead II). However, the PR interval is short — and delta waves are seen.Compared to ECG #2  — there is more preexcitation in ECG #4.And — compared to ECG #2 — the QRS complex in leads aVL and V1 in ECG #4 looks a bit more like the QRS morphology in these same leads during the full preexcitation tracing ECG #1.PEARL #4: The reason for variation in QRS morphology during the supraventricular tachyarrhythmias seen in today ' s case is the result of variation in the relative amount of preexcitation. We saw this best in Figure-3  — in which beats #3-thru-13 showed varying amounts of fusion between normally conducted QRS complexes — and much wider QRS complexes in which impulses were almost entirely conducting over the Accessory Pathway.Figure-4: Comparison of QRS morphology depending on the relative amount of preexcitation (See text).Final INSIGHTS from Today ' s Case:This case i...
Source: Dr. Smith's ECG Blog - Category: Cardiology Authors: Source Type: blogs