Original Article
Brief Report
Clinical Consequences of Electrocardiographic Artifact Mimicking Ventricular Tachycardia
N Engl J Med 1999; 341:1270-1274October 21, 1999
- Article
Electrocardiographic artifact can simulate ventricular tachycardia. The literature regarding electrocardiographic artifact is limited to case reports,1-7 proposed classifications,8,9 and diagnostic criteria.10 There is little information regarding the clinical implications of the misdiagnosis of artifact as ventricular tachycardia. We describe 12 patients who underwent unnecessary diagnostic or therapeutic interventions as a result of such a misdiagnosis.
Methods
We included in this series patients who were seen in consultation by a cardiac electrophysiologist at our institution between 1995 and 1999 and who underwent a diagnostic procedure or received treatment unnecessarily, solely as a result of the misdiagnosis of artifact as ventricular tachycardia. We obtained information on the characteristics of the patients, features of the artifact, and the interventions from the medical records. For patients who had more than one documented recording of artifact that simulated ventricular tachycardia, we selected for analysis the longest recording. Continuous variables are presented as means ±SD.
Results
Characteristics of the Patients
Twelve patients received at least one unnecessary intervention solely because of the misdiagnosis of artifact as ventricular tachycardia (Table 1Table 1
Characteristics of the Patients, Features of the Electrocardiographic Artifact, and Consequences to the Patient of the Misdiagnosis of Artifact as Ventricular Tachycardia.). In seven cases, artifact that mimicked ventricular tachycardia was recorded during telemetric monitoring of inpatients. Five of these patients had been admitted to the hospital after presenting with cardiac symptoms (syncope or presyncope in three patients, palpitations in one, and chest pain in one); one patient had been admitted after cardiac arrest, and the remaining patient was recovering from cardiac surgery. Three patients were undergoing electrocardiographic monitoring in the emergency department when the artifact was recorded, after presenting with chest pain (one patient), acute respiratory failure in the context of chronic obstructive pulmonary disease (one patient), or a constellation of neurologic symptoms (one patient). Artifact was also recorded in a patient who was undergoing outpatient 24-hour Holter monitoring for the evaluation of palpitations and in another patient who was undergoing an exercise treadmill test for the evaluation of atypical chest pain.The mean age of the patients was 57±14 years, and 6 of the 12 patients were men. Five patients had structural heart disease. The mean left ventricular ejection fraction was 49±17 percent. When the artifact was recorded, nine patients were asymptomatic, one patient was experiencing chest pain, one patient was unresponsive because of acute respiratory failure, and one patient had paresthesias of the left arm.
Characteristics of the Artifact
Artifact simulated monomorphic ventricular tachycardia in five patients (Figure 1Figure 1
Rhythm Strip of Electrocardiographic Artifact That Mimicked Monomorphic Ventricular Tachycardia and Led to the Patient's Being Treated with Lidocaine.) and polymorphic ventricular tachycardia in seven patients (Figure 2Figure 2
Rhythm Strip of Electrocardiographic Artifact That Mimicked Polymorphic Ventricular Tachycardia and Led to the Patient's Being Treated with Lidocaine.). The mean rate of simulated ventricular tachycardia was 226±35 beats per minute (range, 180 to 280), and the mean number of apparent tachycardia complexes was 22±7 (range, 11 to 33). Six patients had more than one episode of artifact that simulated ventricular tachycardia. The onset of the artifact was recorded in 75 percent of the patients, and the termination was recorded in 92 percent. Each recording could be recognized as artifact by the presence of native QRS complexes at the cycle length of the base-line rhythm within the artifact.Clinical Consequences of Misdiagnosis
Diagnostic cardiac catheterization was performed in three patients solely because of the incorrect diagnosis of ventricular tachycardia. Unnecessary medical therapies included intravenous lidocaine in seven patients, intravenous nitroglycerin in one patient, and sublingual nitroglycerin in one patient. Two patients were given a precordial thump that was interpreted as a successful cardioversion. One patient in whom torsade de pointes was incorrectly diagnosed underwent implantation of a permanent pacemaker to prevent a recurrence by keeping bradycardia, which typically precedes polymorphic ventricular tachycardia, from occurring. One patient underwent placement of an implantable cardioverter–defibrillator after an episode of artifact was misdiagnosed as polymorphic ventricular tachycardia. Another patient was given a blood transfusion because it was thought that his ventricular tachycardia had been caused by anemia.
The misdiagnosis of artifact increased the use of health care resources. Two patients were transferred to a tertiary care institution for electrophysiologic testing, one patient was transferred to an intensive care unit from a telemetry ward, and one patient was admitted to the hospital from home after a Holter-monitor recording was misinterpreted as showing ventricular tachycardia.
Characteristics of the Physicians
An initial misdiagnosis of ventricular tachycardia was made by a cardiologist in four cases, a medical house officer in four, an emergency-medicine physician in three, and an electrophysiologist in one. A board-certified cardiologist agreed with the diagnosis of ventricular tachycardia in 10 cases before an electrophysiologist was consulted. A board-certified cardiologist referred an additional patient for a second opinion several months after the patient underwent placement of an implantable cardioverter–defibrillator by a practicing electrophysiologist.
Discussion
These cases demonstrate that when artifact is misdiagnosed as ventricular tachycardia, patients may be subjected to a broad range of unnecessary diagnostic and therapeutic procedures, including cardiac catheterization and the implantation of cardiac devices.
Arrhythmias are unique among transient pathologic states because, even in the absence of symptoms, they often lead to intensive investigations and treatments that have long-term repercussions. Because unsustained ventricular tachycardia can be a sign of structural heart disease, acute ischemia, electrolyte abnormalities, or drug toxicity, its identification often prompts a thorough cardiac evaluation that includes blood analysis, stress testing, echocardiography, and angiography.
Several therapies may be prescribed for patients in whom transient ventricular tachyarrhythmias are diagnosed. Patients with impaired ventricular function after myocardial infarction who are found to have unsustained ventricular tachycardia are often referred for electrophysiologic testing for risk stratification. If sustained ventricular tachycardia is induced at the time of electrophysiologic testing, a prophylactic implantable cardioverter–defibrillator is usually implanted.11,12 However, the Multicenter Unsustained Tachycardia Trial found a 4 to 5 percent risk of cardiac arrest or death from arrhythmia per year among patients with coronary artery disease, a left ventricular ejection fraction of 40 percent or less, and asymptomatic unsustained ventricular tachycardia who did not have inducible sustained ventricular tachycardia (Buxton A: personal communication). Therefore, unsustained ventricular tachycardia alone, regardless of the results of electrophysiologic testing, may become an indication for an implantable cardioverter–defibrillator. If so, an erroneous diagnosis of unsustained ventricular tachycardia in a patient with ischemic cardiomyopathy may lead to the placement of an implantable cardioverter–defibrillator — a consequence that underscores the importance of correctly identifying artifact that simulates unsustained ventricular tachycardia.
Pacing therapy may also be instituted in some patients who have ventricular tachycardia in the context of bradycardia. For example, a pacemaker is often implanted in patients with torsade de pointes to prevent the bradycardia that typically precedes the polymorphic ventricular tachycardia.13
Episodes of ventricular tachycardia may lead to increased use of health care resources. Patients are often transferred to an intensive care unit for closer monitoring after an episode of ventricular tachycardia. A diagnosis of ventricular tachycardia may also result in transfer to a tertiary care medical center, where electrophysiologic testing and defibrillator therapy are available.
Electrocardiographic artifact with sufficient amplitude and duration can closely simulate ventricular tachycardia. Therefore, artifact can readily lead to unnecessary testing and therapy. The results of this study demonstrate that patients in whom ventricular tachycardia is incorrectly diagnosed on the basis of electrocardiographic artifact may be subjected to much the same testing and treatment as patients with actual ventricular tachycardia.
Characteristics that differentiate artifact from ventricular tachycardia include the absence of hemodynamic deterioration during the event; normal QRS complexes within the artifact; an unstable base line on the electrocardiogram before the event, after the event, or both; and an association with body movement.10 In this study, the cases of artifact that mimicked ventricular tachycardia and resulted in unnecessary interventions were usually not associated with symptoms and could be distinguished from ventricular tachycardia by the presence of QRS complexes that were visible in the electrocardiographic artifact at intervals that coincided with the cycle length of the base-line rhythm.
The phenomenon of electrocardiographic artifact was recognized and categorized shortly after electrocardiographic monitoring became available.1-10 Artifact has been categorized as pseudoarrhythmic and nonarrhythmic.8 Artifact can simulate ventricular tachycardia, supraventricular tachycardia, Mobitz type II atrioventricular block, and sinus arrest. The potential clinical effect of each type of artifact was categorized by one group of researchers as possible, minimal, or serious.8 However, the outcomes of patients in whom arrhythmia is incorrectly diagnosed because of artifact have been unclear.
Previous studies have concluded that the most likely causes of electrocardiographic artifact that mimics ventricular tachycardia are body movement and intermittent skin–electrode contact.8 The rapid manipulation of a recording electrode on the skin has been shown to simulate ventricular tachycardia.7 Although body movement or a poor skin–electrode contact may have caused the electrocardiographic artifacts described in this series, the actual causes of the artifacts could not be determined.
Although the magnitude of the problem remains unclear, the cases in this report demonstrate that physicians with a broad spectrum of expertise in the diagnosis and treatment of arrhythmia, including board-certified cardiologists and practicing electrophysiologists, at times may mistake artifact for ventricular tachycardia. Furthermore, these cases show that the misdiagnosis of electrocardiographic artifact as ventricular tachycardia may lead to unnecessary interventions as drastic as the implantation of a permanent pacemaker or an implantable cardioverter–defibrillator. These findings indicate the importance of improved training in the recognition of artifact and the need for a heightened index of suspicion among physicians who treat patients with arrhythmias.
Source Information
From the Department of Internal Medicine, Division of Cardiology, University of Michigan Medical Center, Ann Arbor.
Address reprint requests to Dr. Knight at the University of Michigan Health System, 1500 E. Medical Center Dr., B1F245, Ann Arbor, MI 48109-0022, or at bpk@umich.edu.
- References
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