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Chapter 5: Cardiac Arrhythmias and Hypertensive Emergencies

A 73-year-old man with prior history of type 2 diabetes mellitus, hypertension, dyslipidemia, and 3-vessel coronary artery bypass grafting (CABG) presented with dizziness, weakness, and shortness of breath. A 12-lead ECG was obtained at the time of arrival (Fig. 5-14). What is the diagnosis?

 

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Figure 5-14. ECG obtained on arrival.

A. Ventricular tachycardia

B. SVT with aberrancy

C. Preexcited tachycardia

D. Pacemaker-mediated tachycardia

A. Ventricular tachycardia

The ECG shows ventricular tachycardia because of absence of classic right or left bundle branch, absence of RS complex in all precordial leads, and northwest axis. The morphology of the wide complex tachycardia is not consistent with a typical right or left bundle branch block; therefore, it is not SVT with aberrancy (choice B). A negative QRS concordance in precordial leads and presence of AV dissociation are against the diagnosis of preexcited tachycardia (choice C). The ECG does not show pacemaker-mediated tachycardia because there are no pacer spikes preceding the QRS complex (choice D).

Differentiating between SVT and VT can be difficult when the QRS complexes are wide (Figs. 5-29 and 5-30). There are multiple criteria that can be used to differentiate between SVT with aberrancy and VT, the most common being the Brugada criteria. The Brugada criteria is a 4-step algorithm to differentiate between SVT and VT with a sensitivity of 98.7% and a specificity of 96.5%.

 

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Figure 5-29. Part 1. Algorithm to distinguish ventricular tachycardia from SVT with aberrancy.

A wide-complex tachycardia without any RS complexes is 100% specific for the diagnosis of VT (only QS, QR, or monophasic R complexes are observed). An RS interval greater than 100 ms is indicative of VT and is independent of the duration of the QRS complex. Atrioventricular dissociation was 100% specific for VT. A more simplified algorithm for distinguishing SVT from VT looks solely at lead aVR. This algorithm has a 96.5% sensitivity and a 94.6% specificity for VT diagnosis (Table 5-30).

 

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Figure 5-30 Part 2. Algorithm to distinguish ventricular tachycardia from SVT with aberrancy.

 

A 69-year-old patient is admitted to medical intensive care unit (MICU) for the management of chronic obstructive pulmonary disease (COPD) exacerbation. Chest radiograph shows multifocal pneumonia. He is toxic appearing and is unable to speak in complete sentences. Pulse is irregular and weak and pulse oximetry shows O2 saturation of 84%. Blood pressure is 100/65 mmHg. Bedside cardiac monitor ...

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