The lead II rhythm strip shown below was obtained from a patient admitted to the Emergency Department. Interpret the rhythm. How certain are you of your answer? What would you do?
- Scenario #1: The patient is unresponsive with a BP = 60 palpable.
- Scenario #2: The patient is alert and asymptomatic. BP = 120/80 mmHg.
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Figure 1 – Lead II rhythm strip showing tachycardia. What to do? |
INTERPRETATION: The rhythm is fast and fairly (but not completely) regular. The QRS looks to be wide (ie, more than half a large box) and there are no definite P waves. Thus, this appears to be a WCT (Wide Complex Tachycardia) of uncertain etiology. As to the question of What To Do? — the answer depends on the clinical scenario.
- IF the patient is unstable (Scenario #1) — immediately cardiovert. Regardless of whether the rhythm is VT or SVT with bundle branch block or aberrant conduction — hemodynamic instability is an indication for immediate cardioversion.
- On the other hand — IF the patient is stable (Scenario #2) — then by definition, you have at least some time to contemplate treatment (while you work to determine the rhythm). We would obtain more history (previous episodes of WCT?) — look for prior tracings on the patient (either on telemetry or from the patient’s chart) — and get a 12‑lead ECG during tachycardia (Figure 2).
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Figure 2 – 12-lead ECG obtained during tachycardia. Does this help with your answer?
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12-Lead Analysis: The rhythm is rapid and looks to be regular (albeit with occasional minor variation in the R-R interval). The rate is ~150/minute (the R-R is ~2 large boxes in duration).
- The QRS is wide (clearly more than half a large box in leads II,III,V3,V4). That said — overall QRS morphology looks to be supraventricular (in the form of LAHB with LVH and “strain”).
- “Normal atrial activity” is absent in Figure 2 (RED arrow showing no upright P in lead II).
Beyond-the-Core: One wonders if the RED arrow and negative deflections before the QRS in the inferior leads might represent some form of atrial activity … (Figure 3):
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Figure 3 – Short vertical lines have been added to Figure 2 highlighting what might represent underlying atrial activity (See Figure 4).
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IMPRESSION (What to do?): This case illustrates the importance of the clinical situation in the approach to this patient. Whereas immediate cardioversion would be indicated if the rhythm in Figure 1 was associated with hemodynamic instability — additional diagnostic assessment would be appropriate IF the patient is stable (Scenario #2). Clearly — sometimes “ya just gotta be there” to know which approach is best for an individual patient. Our Hunch (based on Figures 1,2,3) — is that the rhythm is supraventricular.
- Slight QRS widening (~0.1-0.2 msec) may be seen with both LVH (it takes longer to get through a thicker ventricle) and with LAHB (conduction is delayed through the left hemifascicle). Thus — QRS widening (as seen in Figure 2) may occur IF there is both LVH and LAHB.
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To PROVE Our Hunch:
- Find a prior ECG on this patient. See IF QRS morphology in the past (during sinus rhythm) is the same as on the Figure 2 12-lead obtained during tachycardia (which shows LAHB; LVH with strain).
- Get more History (prior episodes of WCT that look like Figure 2? )
- Consider a vagal maneuver or “chemical Valsalva” (ie, administration of IV adenosine, which may produce similar effect as carotid massage).
- Treatment will clearly be more effective IF we can be sure of the diagnosis — BUT — IF at any time during the process the patient becomes unstable — Be ready to immediately cardiovert!
Chemical Valsalva in the form of an IV bolus of adenosine was attempted. The result is shown below (Figure 4).
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Figure 4 – Result of “chemical Valsalva”. What does this prove?
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Result of “Chemical Valsalva”: Administration of IV adenosine results in reduced AV conduction with slowing of the ventricular response (RED arrow). This reveals underlying flutter activity at an atrial rate of ~300/minute (sawtooth flutter waves occurring approximately each large box).
- Retrospective review of the 12-lead ECG during tachycardia suggests that the negative deflections previously noted in the inferior leads (and to a lesser extent in lead aVR) were in fact flutter waves (short vertical RED lines in Figure 3).
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KEY Points in this Case:
The 2 scenarios proposed in this case illustrate how to clinically work though assessment and management of a patient with WCT of uncertain etiology.- Always presume VT until proven otherwise. Immediate cardioversion is indicated if the patient is unstable. BUT — IF the patient is stable, there is at least some time to work through the diagnosis.
- Treatment will be much more effective (and you as clinician will be more confident) — IF you are able to determine what the WCT actually is. In this case — Knowing that the rhythm in Figure 1 is atrial flutter with 2:1 AV conduction and QRS widening from LVH/LAHB allows us to treat the patient with IV diltiazem (bolus and drip) — whereas diltiazem would be contraindicated if the rhythm was an ischemic form of VT.
- BOTTOM Line: You will not always know the etiology of a tachycardia at the time you first encounter the patient. No matter — as you can still proceed with an appropriate clinical approach as outlined above.
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- See also ECG Blog #23 -
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