Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content +++ ECG Findings ++ Wide complex, regular tachycardia (usually > 140 bpm) QRS morphology consistent with one of the bundle branch block patterns +++ Pearls ++ The rapid rate of an SVT may “outrun” the ventricular conducting system’s ability to repolarize quickly, producing a rate-related bundle branch block. The signal then must propagate cell to cell, producing a wide-complex tachycardia. A typical bundle branch pattern usually results. When a person with a chronic wide-complex (aberrant) bundle branch block enters an SVT, the ECG will display a wide-complex, regular tachycardia. However, when the patient does not have prior ECGs, it can be difficult to distinguish SVT with aberrancy from a ventricular tachycardia (VT). Many different criteria have been proposed to distinguish the two, but unfortunately, most are neither extremely sensitive nor specific. When in doubt, treat as a VT, as many of the typical SVT pharmacologic agents are detrimental in patients with VT and can lead to ventricular fibrillation and death. ++ FIGURE 23.32A Supraventricular Tachycardia with Aberrant Conduction, Underlying RBBB. (ECG contributor: Walter Clair, MD.) Graphic Jump LocationView Full Size||Download Slide (.ppt) ++ FIGURE 23.32B Wide-complex tachycardia with a rate of 188 bpm. This patient has sudden onset of SVT with a known underlying RBBB. QRS complexes are wide (lower double arrows) and R-R intervals are regular (upper double arrows). Graphic Jump LocationView Full Size||Download Slide (.ppt) ++ FIGURE 23.32C Wide-complex tachycardia at approximately 150 bpm. The R-R interval is regular, except for one pause, when characteristic atrial flutter waves are apparent (arrowhead). Graphic Jump LocationView Full Size||Download Slide (.ppt) ++ FIGURE 23.32D Irregularity in the R-R interval, as seen most easily in the baseline (double arrows), strongly suggests the presence of rapidly conducted atrial fibrillation with aberrancy. Graphic Jump LocationView Full Size||Download Slide (.ppt) Your Access profile is currently affiliated with [InstitutionA] and is in the process of switching affiliations to [InstitutionB]. Please select how you would like to proceed. Keep the current affiliation with [InstitutionA] and continue with the Access profile sign in process Switch affiliation to [InstitutionB] and continue with the Access profile sign in process Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Error: Incorrect UserName or Password Username Error: Please enter User Name Password Error: Please enter Password Sign in Forgot Password? Forgot Username? Sign in via OpenAthens Sign in via Shibboleth You already have access! Please proceed to your institution's subscription. Create a free profile for additional features.