Safety first — sedate and shock

Letters

CJEM 2009;11(2):123

To the editor: Mitchell and Lazarenko recently authored a diagnostic challenge in the November 2008 issue of CJEM.1 We thank the authors for providing this worthy topic for discussion and congratulate them on their publication. However, with due respect, we take considerable issue with several of the conclusions reached in this article and ultimately with the answer to the diagnostic challenge. Although it is alluded to as a possible treatment twice in the discussion, we assert that the safest approach for the emergency physician is to treat all wide complex tachycardia as ventricular tachycardia (VT).

As with many situations in emergency medicine, when a patient presents with an unstable wide complex dysrhythmia, we are forced to make decisions without the benefit of much of the information referenced within the article. The assessment for the presence of cannon atrial waves or variability of the first heart sound requires clinical acumen well beyond even the expert emergency physician. In fact, the additional criterion of variability in beat-to-beat systolic blood pressure requires the placement of an arterial catheter, which is impractical and unnecessary in many instances.

Electrolytes are rarely available and toxicology screens are rarely helpful. The authors state that the toxicology screen was negative, which we believe to be relatively unhelpful in this setting (and in many others), as this test is insufficiently sensitive or specific for the presence of tricyclic antidepressants or any other sodium channel blockers that may be important toxicological causes of wide complex dysrhythmia.

In a 45-year-old patient, the authors acknowledge that even if based solely on the criterion of age, one ought to assume this is VT. Although not polymorphic, the addition of sotalol would increase the pretest likelihood of VT as well.

If indeed the authors' logic is correct and the remaining differential includes supraventricular tachycardia (SVT) with aberrancy by way of an accessory pathway, one still ought to avoid adenosine in these instances. There are several reports of ventricular fibrillation associated with adenosine therapy, in both Wolff-Parkinson-White syndrome2-4 and in the treatment of VT.5 The safest approach in this setting would be electrical cardioversion or, in a stable patient, procainamide.6

We thank the authors for their comments regarding the application of the Brugada criteria. The originally reported sensitivity and specificity were 95.7% and 96.5%,7 which have never been externally reproduced. Two reports have failed to replicate these numbers in the hands of cardiologists or emergency physicians, suggesting even less broad applicability in the emergency setting.8,9 These numbers are not sufficient to exclude VT, particularly when considering verapamil or diltiazem as a potential therapy.

Even if these numbers were acceptable to some practitioners (which is where our concerns lie), life-threatening consequences of misdiagnosing VT as SVT with aberrancy are unacceptable when the therapy of choice for VT works equally well for SVT with aberrancy with very little added potential for harm. The authors correctly suggest that when the diagnosis is uncertain, one should treat the dysrhythmia as VT. Arguably, based on the information provided by these 2 papers,8,9 one can rarely be certain of the diagnosis and should routinely proceed with the treatment of wide complex tachycardia as VT.

The lasting impression of the article is one of using a medical treatment that has grave risks associated with its use. We suggest that when an article is published one should concern themselves with the message that is delivered to the typical emergency physician, and therefore should project a message that is safe and effective.

In this case, no one should close the journal thinking that through cannon atrial waves associated with beat-to-beat systolic variability and Brugada criteria that they can differentiate these 2 entities in the chaos of the emergency department. Let us put the safety of our patients first and the vanity of superior academic skills second.

Sedate and shock this rhythm — be safe.

Andrew Healey, MD
PGY5, Emergency Medicine/Critical Care Resident, McMaster University, Hamilton, Ont.

Mark Mensour, MD, FCFP
Assistant Professor, Emergency
Medicine, Northern Ontario School
of Medicine, Huntsville, Ont.

Thomas Marshall, MD
Staff Emergency Physician,
St. Joseph's Healthcare, Hamilton, Ont.

References

1. Mitchell J, Lazarenko G. Wide QRS complex tachycardia. CJEM 2008;6: 572-3.
2. Gupta AK, Shah CP, Maheshwari A, et al. Adenosine induced ventricular fibrillation in Wolff-Parkinson-White syndrome. Pacing Clin Electrophysiol 2002; 25:477-80.
3. Gallagher JJ, Sealy WC, Kasell J, et al. Multiple accessory pathways in patients with the pre-excitation syndrome. Circulation 1976;54:571-91.
4. Exner DV, Muzyka T, Gillis AM. Proarrhythmia in patients with the Wolff-Parkinson-White syndrome after standard doses of intravenous adenosine. Ann Intern Med 1995;122:351-2.
5. Parham WA, Mehdirad AA, Biermann KM, et al. Case report: adenosine induced ventricular fibrillation in a patient with stable ventricular tachycardia. J Interv Card Electrophysiol 2001;5:71-4.
6. Tijunelis MA, Herbert ME. Myth: intravenous amiodarone is safe in patients with atrial fibrillation and Wolff-Parkinson-White syndrome in the emergency department. CJEM 2005;7: 262-5.
7. Brugada P, Brugada J, Mont L, et al. A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex. Circulation 1991; 83: 1649-59.
8. Isenhour JL, Craig S, Gibbs M, et al. Wide-complex tachycardia: continued evaluation of diagnostic criteria. Acad Emerg Med 2000;7:769-73.
9. Herbert ME, Votey SR, Morgan MT, et al. Failure to agree on the electrocardiographic diagnosis of ventricular tachycardia. Ann Emerg Med 1996;27:35-8.