The patient is a 60-year-old man who presents to the ED (emergency department) with a chief complaint of palpitations and the ECG shown in Figure-1.
- BP = 160/90 mm Hg at the time Figure 1 is recorded.
- You know nothing more than that the patient has a history of "heart disease" — and that he is on a number of medications.
|Figure-1: 12-lead ECG obtained on a 60-year-old man with a history of "heart disease" and palpitations. BP=160/90. (Figure reproduced from Figure 09.5-1 in ACLS-2013-ePub). - NOTE - Enlarge by clicking on Figures - Right-Click to open in a separate window.|
CONSIDER THESE QUESTIONS:
- What is the rhythm in Figure-1? How certain are you of your specific rhythm diagnosis?
- How would you proceed clinically? Do you need to be certain of the rhythm diagnosis before initiating treatment?
- Would you give Adenosine as your 1st drug? If so — What is the response you expect this drug to have?
- What might be done to increase your level of certainty about the specific rhythm diagnosis for the tracing in Figure-1? Would definitive rhythm diagnosis change your therapeutic approach? If so — How?
ANSWERS: A regular WCT is seen at a rate of ~160/minute. There is no clear evidence of atrial activity. The differential diagnosis is that of a regular WCT (Wide-Complex Tachycardia) = VT, VT, VT until proven otherwise.
- Given the patient’s age and history of “heart disease” — statistical likelihood of VT is ~90% without going further.
- The above said — there IS a chance that the rhythm in Figure-1 could be SVT (with either aberrant conduction or preexisting BBB).
The 12-lead tracing in Figure-1 provides an excellent example of how to approach a WCT Rhythm when you do not know for sure what the diagnosis is (See Section 08.0,09.0 in the References below):
- The patient is stable (ie, there is time to look further).
- The WCT is regular. Therefore — the rhythm is not AFib.
- The QRS is monomorphic (all QRS complexes in a given lead look the same). Thus, this is not polymorphic VT/Torsades.
- Assessment of QRS morphology is inconclusive. That is — the ‘3 Simple Rules’ do not suggest VT (discussed in detail in Section 08.0 in the References below). Specifically — the axis during WCT is normal — lead V6 is upright – and – the QRS is not “ugly”, but instead is perfectly consistent with LBBB.
- Failure of Adenosine — to either temporarily slow the rate or convert the rhythm would support the premise that the rhythm in Figure-1 is VT. At this point — We would then move on to Amiodarone (or other VT drug).
- Successful conversion of the rhythm by Adenosine would support (but not definitely prove) a supraventricular etiology.
- Remain ready to cardiovert — IF at any time the patient becomes hemodynamically unstable.
- Ask someone to search this patient’s chart in the hope of finding a prior 12-lead ECG that might tell if this patient had baseline LBBB.
This case highlights a number of important points:
- Definitive diagnosis of the rhythm in Figure-1 is not needed to effectively treat the patient. Instead we follow the course laid out for WCT of Uncertain Etiology (discussed in detail in Section 08.0 in the References below).
- Use of the ‘3 Simple Rules’ does not point toward VT in this case (but these Rules still help as they make an SVT diagnosis more plausible).
- Assessment of more advanced QRS morphologic features likewise fails to yield a definitive answer (See Section 08.0). That is — at least one rS complex is present in precordial leads (seen here in V2,V3,V4) and there is no delay in S wave downslope in V1,V2,V3. The initial r wave in lead V4 is not wide.
Use of the 12-lead during tachycardia is also helpful in clarifying questions about atrial activity. For example — one might wonder IF the upright deflection midway between QRS complexes in lead II (and in other leads) could be a sinus P wave? (arrows in Figure-2).
|Figure-2: We’ve added arrows to Figure-1. There are no definite P waves (unless they could be hidden within the ST-T wave ...).|
- Access to a prior 12-lead ECG on this patient would favor SVT if LBBB with identical morphology was seen.
- IF the patient remained stable — Use of a Lewis Lead might be attempted looking for atrial activity (See Section 10.0 in the References below).
Please Check out the following relevant PDF Sections excerpted from ACLS-2013-ePub:
- Section 06.0 — on Using Adenosine -
- Section 07.0 — on Known VT -
- Sections 08.0, 09.0,10.0 — on The Regular Wide Tachycardia -
- Section 13.0 — on SVT of Uncertain Etiology -