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Case Reports  |   May 2007
Etomidate-induced Pacemaker-mediated Ventricular Tachycardia
Author Affiliations & Notes
  • Michael D. Altose, M.D., Ph.D.
    *
  • Elias León-Ruiz, M.D.
  • * Resident, † Assistant Professor.
Article Information
Case Reports / Cardiovascular Anesthesia / Pharmacology / Technology / Equipment / Monitoring
Case Reports   |   May 2007
Etomidate-induced Pacemaker-mediated Ventricular Tachycardia
Anesthesiology 5 2007, Vol.106, 1059-1060. doi:10.1097/01.anes.0000265169.60124.15
Anesthesiology 5 2007, Vol.106, 1059-1060. doi:10.1097/01.anes.0000265169.60124.15
ETOMIDATE is a hypnotic drug used for both induction and maintenance of anesthesia. An induction dose typically has little effect on cardiovascular performance, and its rapid onset, quick recovery, and maintenance of blood pressure make etomidate a good choice for ambulatory external cardioversion.1,2 Some consider this drug to be the agent of choice in patients who may become hemodynamically unstable.3,4 One of the most common side effects of etomidate is transient skeletal muscle movements, particularly myoclonus.1–5 Although arrhythmias are rarely encountered with etomidate, we present a case of etomidate-induced pacemaker-mediated ventricular tachycardia.
Case Report
A 27-yr-old woman presented for cardioversion during general anesthesia. Her medical history was remarkable for multiple congenital heart defects, including subaortic stenosis, coarctation of the aorta, ventricular septal defect, and anomalous return of the left superior vena cava to the coronary sinus. Previous surgeries included repair of coarctation of the aorta and pulmonary artery banding (in infancy); repair of ventricular septal defect, subaortic resection, and tricuspid valvuloplasty (age 7 yr); and aortic valve replacement with a St. Jude valve (age 14 yr). The patient underwent pacemaker placement at age 7 yr due to postsurgical complete heart block, with several subsequent revisions. She presented in atrial fibrillation that had been unresponsive to previous attempts at electrical direct current cardioversion. Her medications were lisinopril, furosemide, warfarin, and digoxin. There were no known allergies and no history of adverse reaction to anesthetic agents. Vital signs and serum electrolytes were within normal limits, and the electrocardiogram showed atrial fibrillation with normal ventricle capture at a rate of 70 beats/min (fig. 1).
Fig. 1. The patient’s baseline electrocardiogram showed atrial fibrillation with normal ventricle capture by the pacemaker at a rate of 70 beats/min. 
Fig. 1. The patient’s baseline electrocardiogram showed atrial fibrillation with normal ventricle capture by the pacemaker at a rate of 70 beats/min. 
Fig. 1. The patient’s baseline electrocardiogram showed atrial fibrillation with normal ventricle capture by the pacemaker at a rate of 70 beats/min. 
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Before the procedure, the pacemaker (Prodigy Model DR 7860; Medtronic Inc, Minneapolis, MN) was found to be operating normally with ventricular pacing at 70 beats/min in a rate-responsive mode. The responsive function was then disabled. After preoxygenating the patient with 100% O2by facemask, she was given 10 mg intravenous etomidate and cardioversion (200 J) was attempted, without success. Severe myoclonic activity was observed immediately. When it was confirmed that the patient was still properly anesthetized, cardioversion was attempted a second time, but the atrial fibrillation could not be resolved. At this point, the cardiology team decided to make no further attempts at cardioversion, and the procedure was terminated. When the responsive function on the pacemaker was restored, the patient’s electrocardiogram immediately showed pacemaker-mediated ventricular tachycardia with a rate of 140 beats/min (fig. 2). After the responsive function was disabled again, the electrocardiogram resolved to the patient’s preprocedure rhythm at a rate of 70 beats/min. The patient was observed closely until there were no traces of myoclonic activity; then, the pacemaker was restored to its precardioversion settings once again, without any further disturbances in rhythm. The patient was subsequently noted to be feeling well and talking comfortably.
Fig. 2. The patient’s electrocardiogram showed pacemaker-mediated ventricular tachycardia at a rate of 140 beats/min. The rhythm returned to the preprocedure rate of 70 beats/min when the responsive function was disabled again, at the point indicated by the asterisk (*). 
Fig. 2. The patient’s electrocardiogram showed pacemaker-mediated ventricular tachycardia at a rate of 140 beats/min. The rhythm returned to the preprocedure rate of 70 beats/min when the responsive function was disabled again, at the point indicated by the asterisk (*). 
Fig. 2. The patient’s electrocardiogram showed pacemaker-mediated ventricular tachycardia at a rate of 140 beats/min. The rhythm returned to the preprocedure rate of 70 beats/min when the responsive function was disabled again, at the point indicated by the asterisk (*). 
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Discussion
Although tachycardia, bradycardia, and other arrhythmias have occasionally been observed during induction and maintenance of anesthesia, there have been no published reports of etomidate-induced arrhythmias in patients with pacemakers. However, it is well known that adaptive-rate devices that sense vibration, impedance changes, or the QT interval may be triggered by mechanical or physiologic interference, leading to inappropriate high-rate pacing. This sensor-driven pacemaker-mediated tachycardia can be precipitated by such mechanical factors as direct pressure on the device (e.g.  , prone position), bone hammers and saws, or even a bumpy ride in a stretcher or hospital bed.6 Postoperative shivering could also trigger this phenomenon.7 
The most frequent adverse reaction associated with use of intravenous etomidate (other than brief venous pain on injection) is transient skeletal muscle movements, including myoclonus. In our case, it is likely that the etomidate caused the patient’s myoclonic activity, which then triggered the pacemaker’s responsive function, leading to a ventricular paced rate of 140 beats/min, which is by definition ventricular tachycardia.
The effect we report here would be rare with most uses of etomidate because myoclonus has either resolved or been blocked by muscle relaxants before the end of the surgical procedure. Only in ultrashort cases such as cardioversion would there be a significant risk of postprocedural myoclonus. Given that several studies have demonstrated the utility and safety of etomidate for use during ambulatory external electrical cardioversion, we can recommend two steps to minimize the incidence of this adverse effect in the future. First, the incidence of myoclonus associated with etomidate administration can be reduced by giving the drug as an infusion instead of an intravenous bolus. Second, premedicating the patient with a narcotic or benzodiazepine can minimize the occurrence of myoclonic activity.5 However, these recommendations may not always be feasible in the context of the ambulatory setting, and the advantages and disadvantages must be considered.
There are several standard precautions that can help to minimize the incidence of any mechanically induced pacemaker-mediated tachycardia. It is essential that the pacemaker should be programmed to an asynchronous mode, preferably one that maintains atrial–ventricular sequence, especially in patients with impaired ventricular function.6 We also stress the importance of carefully evaluating the patient for any signs of myoclonic activity before restoring the pacemaker to its responsive setting. Similarly, any other external mechanical disturbances must also be resolved before returning the device to normal operation. Following these recommendations may help to decrease the incidence of etomidate-induced or any other mechanically induced pacemaker-mediated ventricular tachycardia and allow for rapid and effective diagnosis and treatment of this rhythm.
References
Herregods LL, Bossuyt GP, De Baerdemaeker LE, Moerman AT, Struys MM, Den Blauwen NM, Tavernier RM, Mortier E: Ambulatory electrical external cardioversion with propofol or etomidate. J Clin Anesth 2003; 15:91–6Herregods, LL Bossuyt, GP De Baerdemaeker, LE Moerman, AT Struys, MM Den Blauwen, NM Tavernier, RM Mortier, E
Coll-Vinent B, Sala X, Fernandez C, Bragulat E, Espinosa G, Miro O, Milla J, Sanchez M: Sedation for cardioversion in the emergency department: Analysis of effectiveness in four protocols. Ann Emerg Med 2003; 42:792–7Coll-Vinent, B Sala, X Fernandez, C Bragulat, E Espinosa, G Miro, O Milla, J Sanchez, M
Canessa R, Lema G, Urzua J, Dagnino J, Concha M: Anesthesia for elective cardioversion: A comparison of four anesthetic agents. J Cardiothorac Vasc Anesth 1991; 5:566–8Canessa, R Lema, G Urzua, J Dagnino, J Concha, M
Hullander RM, Leivers D, Wingler K: A comparison of propofol and etomidate for cardioversion. Anesth Analg 1993; 77:690–4Hullander, RM Leivers, D Wingler, K
Reves JG, Glass PSA, Lubarsky DA, McEvoy MD: Etomidate, Anesthesia, 6th edition. Edited by Miller RD. Philadelphia, Elsevier, 2005, pp 350–5Reves, JG Glass, PSA Lubarsky, DA McEvoy, MD Miller RD Philadelphia Elsevier
Atlee JL, Bernstein AD: Cardiac rhythm management devices: II. Perioperative management. Anesthesiology 2001; 95:1492–506Atlee, JL Bernstein, AD
Anand NK, Maguire DP: Anesthetic implications for patients with rate-responsive pacemakers. Semin Cardiothorac Vasc Anesth 2005; 9:251–9Anand, NK Maguire, DP
Fig. 1. The patient’s baseline electrocardiogram showed atrial fibrillation with normal ventricle capture by the pacemaker at a rate of 70 beats/min. 
Fig. 1. The patient’s baseline electrocardiogram showed atrial fibrillation with normal ventricle capture by the pacemaker at a rate of 70 beats/min. 
Fig. 1. The patient’s baseline electrocardiogram showed atrial fibrillation with normal ventricle capture by the pacemaker at a rate of 70 beats/min. 
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Fig. 2. The patient’s electrocardiogram showed pacemaker-mediated ventricular tachycardia at a rate of 140 beats/min. The rhythm returned to the preprocedure rate of 70 beats/min when the responsive function was disabled again, at the point indicated by the asterisk (*). 
Fig. 2. The patient’s electrocardiogram showed pacemaker-mediated ventricular tachycardia at a rate of 140 beats/min. The rhythm returned to the preprocedure rate of 70 beats/min when the responsive function was disabled again, at the point indicated by the asterisk (*). 
Fig. 2. The patient’s electrocardiogram showed pacemaker-mediated ventricular tachycardia at a rate of 140 beats/min. The rhythm returned to the preprocedure rate of 70 beats/min when the responsive function was disabled again, at the point indicated by the asterisk (*). 
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