When You Hear Hoofbeats, Look for Horses, Not Zebras.

Abstract

HomeCirculationVol. 143, No. 8When You Hear Hoofbeats, Look for Horses, Not Zebras Free AccessCase ReportPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyRedditDiggEmail Jump toFree AccessCase ReportPDF/EPUBWhen You Hear Hoofbeats, Look for Horses, Not Zebras Dursun Aras, MD, Ozcan Ozeke, MD and Serkan Topaloglu, MD Dursun ArasDursun Aras University of Health Sciences, Ankara City Hospital, Department of Cardiology, Turkey. Search for more papers by this author , Ozcan OzekeOzcan Ozeke Ozcan Ozeke, MD, Sağlik Bilimleri Üniversitesi, Ankara Şehir Hastanesi, Kardiyoloji Klinigi, Bilkent, 06800, Ankara, TURKIYE. Email E-mail Address: [email protected] https://orcid.org/0000-0002-4770-8159 University of Health Sciences, Ankara City Hospital, Department of Cardiology, Turkey. Search for more papers by this author and Serkan TopalogluSerkan Topaloglu University of Health Sciences, Ankara City Hospital, Department of Cardiology, Turkey. Search for more papers by this author Originally published22 Feb 2021https://doi.org/10.1161/CIRCULATIONAHA.120.052468Circulation. 2021;143:862–864ECG ChallengeA 62-year-old woman with nonischemic cardiomyopathy was referred for cardiac resynchronization therapy for heart failure and left bundle-branch block (Figure 1). She had New York Heart Association Class III exertional dyspnea and easy fatiguability for 3 months. Her heart rate was 119 beats/min and blood pressure was 120/70 mm Hg, with no significant murmurs on cardiac auscultation. Would you recommend or consider a cardiac resynchronization therapy device based on these clinical and electrocardiographic findings?Download figureDownload PowerPointFigure 1. Twelve-lead ECG taken in the outpatient clinic from the patient referred for cardiac resynchronization therapy defibrillator implantation.Please turn the page to read the diagnosis.Response to ECG ChallengeApparently, at first glance, the patient had a sinus tachycardia with left bundle-branch block and was a suitable cardiac resynchronization therapy. The difference of apparent P waves in V1 was misinterpreted as being consistent with sinus rhythm at the initial assessment, but clear atrioventricular dissociation in other leads like V2 was recognized when reviewed by a senior clinician (note arrows in Figure 2). Then the ventricular tachycardia (VT) with left bundle-branch block morphology was diagnosed. Epicardial mapping and ablation were performed because no abnormal substrate was found on the endocardial mapping. After ablation, true sinus rhythm with left bundle-branch block was provided (Figure 3), and a cardiac resynchronization therapy device was implanted thereafter.Download figureDownload PowerPointFigure 2. Closer inspection of the anterior precordial leads of Figure. Note the true (arrows) and pseudo P waves (arrowheads) as the evidence of atrioventricular dissociation. Compare the initial component of the QRS complexes in V1–3 leads (dashed lines) to determine whether the pseudo P wave is part of the QRS.Download figureDownload PowerPointFigure 3. Twelve-lead ECG taken after successful ventricular tachycardia ablation.Although the similarity of QRS morphology in tachycardia and sinus rhythm suggests a supraventricular origin, in occasional circumstances the onset of VT may produce no apparent change in QRS morphology, thus making the diagnosis by conventional electrocardiographic criteria difficult.1,2 However, the presence of either atrioventricular dissociation or capture/fusion beats in the 12-lead ECG during the wide QRS tachycardia (WCT) are key diagnostic features of VT. Therefore, it is appropriate to “cherchez le P” to look for the relationship between atrial and ventricular activity as an initial step in the differential diagnosis of WCT.3 The use of Lewis leads may also improve the detection of P waves. This patient’s ECG was particularly interesting because the atrioventricular dissociation and superior/inferior axis changes were present in the same patient at approximately the same time and established the VT mechanism of wide QRS complexes. The patient had also pseudotwin-peaked P waves in lead V1 (note arrowheads in Figure 2). Comparing the initial component of the QRS complexes can be examined to determine whether the pseudo P wave is part of the QRS (Figure 2, dashed line).A variety of criteria have been proposed for the differentiation of WCT, such as the Wellens, Kindwall, Brugada, Bayesian, Griffith, Pava, Jastrzebski, and Vereckei algorithms.2 However, the very philosophy of making a WCT diagnosis based on a single criterion is erroneous because it is clinically and diagnostically futile.2 Therefore, physicians should be cautioned against overreliance on these ECG algorithms. This case illustrates that pseudo P waves may be present on the surface ECG and lead to diagnostic confusion. The presence of atrioventricular dissociation and a prolonged QRS (0.16 s or more) confirmed that the arrhythmia was VT. Even if all conventional algorithms for the differentiation of WCT fail, it is wisest to treat the patient with WCT initially as though the diagnosis was VT (which is correct about 80% of the time) and leave the fine-tuning of diagnosis and long-term management plan for later.2 A wise man once said, “When you hear hoofbeats, look for horses, not zebras.”Disclosures None.Footnoteshttps://www.ahajournals.org/journal/circOzcan Ozeke, MD, Sağlik Bilimleri Üniversitesi, Ankara Şehir Hastanesi, Kardiyoloji Klinigi, Bilkent, 06800, Ankara, TURKIYE. Email [email protected]com