- Email: [email protected]
Now You See It; Now You Don’t
The American Journal of Medicine (2007) 120, 512-514
ECG IMAGE OF THE MONTH Julia H. Indik, MD, PhD, Section Editor
Now You See It; Now You Don’t Norman C. Wang, MD Division of Cardiology, Feinberg School of Medicine, Northwestern University, Chicago, Ill.
PRESENTATION The following case illustrates the importance of thinking outside the box. A 92-year-old man arrived in the emergency department with fever, cough, shortness of breath, and hypoxia. He had a history of coronary artery disease, ischemic cardiomyopathy, atrial fibrillation and atrial flutter, and complete heart block; a dual-chamber pacemaker was in place. Significant findings included a temperature of 101° F (38.3°C), an oxygen saturation of 88% on room air, a white blood cell count of 15.7 x 103 cells/mm3, and a chest x-ray revealing pleural effusions and possible pulmonary infiltrates. The patient was admitted to the telemetry unit and treated for pneumonia. On hospital day 2, the managing internal medicine team noted atrial beats at a fast rate on his telemetry recording that, inexplicably, were not seen on a 12-lead surface ECG (Figures 1 and 2). The team members, suspecting atrial flutter and/or pacemaker malfunction, consulted the electrophysiology service on hospital day 4.
ASSESSMENT A physical examination of the patient uncovered a significant tremor of his upper extremities, with a relatively stable torso. While the smaller spikes were seen on telemetry, his pacemaker was interrogated, and a real-time intracardiac electrogram was recorded (Figures 3 and 4). The pacemaker data clearly demonstrated sinus rhythm with ventricularpaced beats tracking the patient’s native P waves (ie, they were atrially-sensed and ventricularly paced.)
DIAGNOSIS The arrhythmia seen on telemetry was an artifact generated by the patient’s tremor. Because the right-arm electrode was Requests for reprints should be addressed to Norman C. Wang, MD, Fellow, Cardiac Electrophysiology, Northwestern Memorial Hospital, 251 East Huron Street, Feinberg 8-542, Chicago, IL 60611. E-mail address: [email protected].
0002-9343/$ -see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.amjmed.2007.03.004
the most distally placed on the upper arm, it was subjected to the greatest movement. This explains why the artifact was most pronounced in leads I, II and aVR. A diagnosis of electrocardiographic artifact could be made on the basis of the telemetry strip alone. The top recording showed a ventricularly-paced rhythm at a rate of approximately 75 beats per minute, with smaller spikes at a rate of approximately 250 beats per minute; the ventricular pacing spikes and the smaller spikes are dissociated from one another. At the same time, the bottom recording is virtually free of the smaller spikes, and clear P waves can be seen preceding each ventricular-pacing spike by approximately 120 milliseconds. A review of the 12-lead ECG confirms P waves in lead V1. While the presence of a fine-tremor artifact can be appreciated, the pronounced spikes seen on the telemetry strip are not present. Pacing spikes can be difficult to see when the leads are of bipolar configuration, as they were in this case. Small pacing artifacts were evident preceding several QRS complexes. The left bundle branch block morphology with a superiorly directed QRS axis suggested ventricular lead placement in the right ventricular apex.1
MANAGEMENT It is essential to recognize an ECG artifact so that the true underlying rhythm can be determined. Muscle tremors causing ECG artifact are known to simulate atrial flutter.2 The problem can be avoided by placing the brachial electrodes on the deltoid areas instead of the arms. Although cardiologists and electrophysiologists are better able to discriminate artifact than are internists, they also can miss a significant number.3 Failing to detect an artifact can lead to undesired clinical consequences, especially when it is mistaken for ventricular arrhythmia.4 In our case, the patient had his hospital stay prolonged by 1 day. Satisfactory improvement in his pneumonia would have allowed for discharge on day 3, had it not been for the supposed cardiac abnormalities.
Wang
ECG Artifact
513
Figure 1 (A) The top recording in this representative telemetry strip obtained on hospital day 4 is from lead II, and (B) the bottom recording is from a center chest lead.
Figure 2
A 12-lead ECG was obtained simultaneously with the telemetry strip depicted in Figure 1.
Figure 3 A standard “full disclosure” telemetry strip depicts the 7 leads recorded with 4 surface electrodes. Seen here, in order from top to bottom, are leads I, II, III, V, aVR, aVL, and aVF.
514
The American Journal of Medicine, Vol 120, No 6, June 2007
Figure 4 A real-time intracardiac recording was taken from the patient’s pacemaker. (A) At top is the surface recording; (B) the middle recording is from the atrial lead; and (C) the bottom recording is from the ventricular lead. Atrially-sensed beats are designated AS, while ventricularly-paced beat are marked VP.
References 1. Wood MA, Ellenbogen KA. Temporary cardiac pacing. In: Ellenbogen KA, Wood MA, eds. Cardiac Pacing and ICDs. 4th ed. Malden, Mass: Blackwell Publishing; 2005:163-195. 2. Saint-Pierre A. ECG artifacts simulating atrial flutter. JAMA. 1973;224: 1534.
3. Knight BP, Pelosi F, Michaud GF, et al. Physician interpretation of electrocardiographic artifact that mimics ventricular tachycardia. Am J Med. 2001;110:335-8. 4. Knight BP, Pelosi F, Michaud GF, et al. Clinical consequences of electrocardiographic artifact mimicking ventricular tachycardia. N Engl J Med. 1999;341:1270-1274.
ECG IMAGE OF THE MONTH Julia H. Indik, MD, PhD, Section Editor
Now You See It; Now You Don’t Norman C. Wang, MD Division of Cardiology, Feinberg School of Medicine, Northwestern University, Chicago, Ill.
PRESENTATION The following case illustrates the importance of thinking outside the box. A 92-year-old man arrived in the emergency department with fever, cough, shortness of breath, and hypoxia. He had a history of coronary artery disease, ischemic cardiomyopathy, atrial fibrillation and atrial flutter, and complete heart block; a dual-chamber pacemaker was in place. Significant findings included a temperature of 101° F (38.3°C), an oxygen saturation of 88% on room air, a white blood cell count of 15.7 x 103 cells/mm3, and a chest x-ray revealing pleural effusions and possible pulmonary infiltrates. The patient was admitted to the telemetry unit and treated for pneumonia. On hospital day 2, the managing internal medicine team noted atrial beats at a fast rate on his telemetry recording that, inexplicably, were not seen on a 12-lead surface ECG (Figures 1 and 2). The team members, suspecting atrial flutter and/or pacemaker malfunction, consulted the electrophysiology service on hospital day 4.
ASSESSMENT A physical examination of the patient uncovered a significant tremor of his upper extremities, with a relatively stable torso. While the smaller spikes were seen on telemetry, his pacemaker was interrogated, and a real-time intracardiac electrogram was recorded (Figures 3 and 4). The pacemaker data clearly demonstrated sinus rhythm with ventricularpaced beats tracking the patient’s native P waves (ie, they were atrially-sensed and ventricularly paced.)
DIAGNOSIS The arrhythmia seen on telemetry was an artifact generated by the patient’s tremor. Because the right-arm electrode was Requests for reprints should be addressed to Norman C. Wang, MD, Fellow, Cardiac Electrophysiology, Northwestern Memorial Hospital, 251 East Huron Street, Feinberg 8-542, Chicago, IL 60611. E-mail address: [email protected].
0002-9343/$ -see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.amjmed.2007.03.004
the most distally placed on the upper arm, it was subjected to the greatest movement. This explains why the artifact was most pronounced in leads I, II and aVR. A diagnosis of electrocardiographic artifact could be made on the basis of the telemetry strip alone. The top recording showed a ventricularly-paced rhythm at a rate of approximately 75 beats per minute, with smaller spikes at a rate of approximately 250 beats per minute; the ventricular pacing spikes and the smaller spikes are dissociated from one another. At the same time, the bottom recording is virtually free of the smaller spikes, and clear P waves can be seen preceding each ventricular-pacing spike by approximately 120 milliseconds. A review of the 12-lead ECG confirms P waves in lead V1. While the presence of a fine-tremor artifact can be appreciated, the pronounced spikes seen on the telemetry strip are not present. Pacing spikes can be difficult to see when the leads are of bipolar configuration, as they were in this case. Small pacing artifacts were evident preceding several QRS complexes. The left bundle branch block morphology with a superiorly directed QRS axis suggested ventricular lead placement in the right ventricular apex.1
MANAGEMENT It is essential to recognize an ECG artifact so that the true underlying rhythm can be determined. Muscle tremors causing ECG artifact are known to simulate atrial flutter.2 The problem can be avoided by placing the brachial electrodes on the deltoid areas instead of the arms. Although cardiologists and electrophysiologists are better able to discriminate artifact than are internists, they also can miss a significant number.3 Failing to detect an artifact can lead to undesired clinical consequences, especially when it is mistaken for ventricular arrhythmia.4 In our case, the patient had his hospital stay prolonged by 1 day. Satisfactory improvement in his pneumonia would have allowed for discharge on day 3, had it not been for the supposed cardiac abnormalities.
Wang
ECG Artifact
513
Figure 1 (A) The top recording in this representative telemetry strip obtained on hospital day 4 is from lead II, and (B) the bottom recording is from a center chest lead.
Figure 2
A 12-lead ECG was obtained simultaneously with the telemetry strip depicted in Figure 1.
Figure 3 A standard “full disclosure” telemetry strip depicts the 7 leads recorded with 4 surface electrodes. Seen here, in order from top to bottom, are leads I, II, III, V, aVR, aVL, and aVF.
514
The American Journal of Medicine, Vol 120, No 6, June 2007
Figure 4 A real-time intracardiac recording was taken from the patient’s pacemaker. (A) At top is the surface recording; (B) the middle recording is from the atrial lead; and (C) the bottom recording is from the ventricular lead. Atrially-sensed beats are designated AS, while ventricularly-paced beat are marked VP.
References 1. Wood MA, Ellenbogen KA. Temporary cardiac pacing. In: Ellenbogen KA, Wood MA, eds. Cardiac Pacing and ICDs. 4th ed. Malden, Mass: Blackwell Publishing; 2005:163-195. 2. Saint-Pierre A. ECG artifacts simulating atrial flutter. JAMA. 1973;224: 1534.
3. Knight BP, Pelosi F, Michaud GF, et al. Physician interpretation of electrocardiographic artifact that mimics ventricular tachycardia. Am J Med. 2001;110:335-8. 4. Knight BP, Pelosi F, Michaud GF, et al. Clinical consequences of electrocardiographic artifact mimicking ventricular tachycardia. N Engl J Med. 1999;341:1270-1274.