Important case by Dawn — that illustrates a number of KEY concepts regarding evaluation and management of a regular WCT ( = Wide-Complex Tachycardia).

As per Dawn — the history is that of a 78-year old woman who called EMS for palpitations — but who otherwise appeared to be hemodynamically stable. No information regarding her previous health status.

The “good news” — is that this patient was hemodynamically stable with today’s initial ECG. The “other news” — is that given her age, our “threshold” to consider emergency cardioversion will be immediately lowered.

For clarity — I’ve put ECG #1 together with ECG #3, with a few added labels. I interpreted ECG #1 as showing a regular WCT at ~225/minute, without clear sign of P waves. To EMPHASIZE — identifying sinus P waves in a rhythm this fast is difficult, because of how short R-R intervals are. But I thought the PR interval would be too short if the upright deflection I’ve labeled with a RED line were to be a sinus P wave. In my experience — you’ll virtually never see P waves in lead V5 but not in leads V1, III, aVF — so I do not think there are sinus P waves, but instead just prominent T waves that simulate P waves because the rate is so fast. (NOTE: Against the RED lines being P waves is the reality that sinus tachycardia will not attain a rate of 225/minute in a 78 year woman …).

Instead — I suspected in my initial review of ECG #1 that the BLUE lines in ECG #1 represented retrograde P waves. I fully acknowledge it is impossible to prove this — but I believe the course of events in today’s case IS consistent with my assumption of retrograde P waves with a short RP’ interval in this patient with AVNRT.

As per Dawn — the computerized interpretation suggested a “normal” PR interval in ECG #1. That said — my 1st PEARL is to IGNORE the computer interpretation for ANY complex arrhythmia, because there are just too many false positives and false negatives for computerized ECG rhythm interpretation. In my opinion (based on 40+ years of careful observation) — there will NEVER be a sufficiently accurate computer ECG program for complex cardiac arrhythmias. Instead — the responsibility for the interpretation of complex arrhythmias lies with us! I say this with full appreciation and acknowledgment of the wonderful work that Drs. Stephen Smith and Pendell Meyers are accomplishing for attaining highly accurate computerized interpretations in the Queen Of Hearts application for identification of acute OMI ( = acute coronary occlusion MIs). That said — accurate computerized interpretation of complex arrhythmias is a completely other story (in my opinion).

I completely agree with Dawn that QRS morphology in ECG #1 is perfectly consistent with LBBB conduction. Not only are monophasic all upright R waves present in lateral leads I,aVL,V6 — and a predominantly negative QRS complex in right-sided lead V1 — but predominant negativity of the QRS extends to lead V5 — and the SLOPE of the downslope of the S waves in V1-thru-V4 is very steep, all consistent with supraventricular LBBB conduction.

BOTTOM LINE: Nothing is 100% — but given such typical QRS morphology for LBBB conduction AND what I perceive as 1:1 retrograde (V:A) conduction — I thought the rhythm diagnosis of ECG #1 most likely to be AVNRT with QRS widening manifesting LBBB conduction due EITHER to preexisting LBBB — OR — to LBBB aberration.

What to do depends. Again — a rate of 225/minute in a 78 year old person is not something I would want to leave for a long time. As to whether I would try Adenosine or Amiodarone before cardioverting — would depend. Either action might be reasonable — and “Ya just gotta be there” to know what you feel would be best “at the bedside”, given the circumstances.

NOTE: The reason I would consider Adenosine — is that this drug in my opinion, would have highest chance of prompt success in converting this rhythm that I suspect is AVNRT with LBBB conduction. I realize and accept that others may disagree — and I don’t think anyone can know with certainty what the rhythm is in ECG #1 from this single tracing.

The patient was electrically cardioverted — and sinus rhythm was restored. Note that the PR interval is clearly longer in the post-conversion tracing than in ECG #1 (GREEN lines). Note also that with sinus rhythm — definite sinus P waves are also seen in leads III,aVF and V1. While true that the PR interval does shorten with tachycardia — it does not usually shorten as much as it would have to if the RED arrows in lead II of ECG #1 were P waves.

As per Dawn — a PVC is seen at the end of the post-conversion tracing — with a different QRS morphology than for the WCT (ie, the QRS is all positive in leads V4,5,6 for this PVC — whereas there should be predominant negativity in leads V4,V5 if there was LBBB conduction).

NOTE: The fact that with sinus rhythm in the post-conversion tracing the QRS is narrow — tells us that the reason for LBBB conduction during the tachycardia was not “preexisting BBB” — but rather rate-related LBBB aberration.

FINAL THOUGHT: In the post-conversion ECG — there is nonspecific ST segment flattening in multiple leads, with some ST depression in a number of leads — and with ST elevation in lead aVR. This is not a “normal” ECG — and in a 78 year old woman, it may represent underlying coronary disease. While true that it is common to see ST-T wave abnormalities following a sustained tachycardia — it should be kept in mind that further evaluation of this 78 year old patient will be important for determing longterm management (ie, Potential need to consider a rate-slowing medication to prevent SVT recurrence and/or possible need to evaluate for underlying coronary disease).