Table 4. Studies assessing incorrect electrocardiogram diagnoses resulting from electrode misplacement.

mV,: millivolts; Ref: references; <: less than; o: degrees

Year	Comments	Ref
1996	The study included 30 experienced technicians evaluating their placement of precordial electrodes. In more than 50 percent of routine applications of leads V1 and V2, there was superior quadrant displacement of more than 0.625 inch; this was an indication that these electrodes were commonly placed both high and wide of their anatomically defined precordial sites. Similarly, in 30 percent to 50 percent leads of routine application of V4 through V6, there was an inferior and leftward displacement of more than 0.625 inch; therefore, this indicates that these lateral precordial electrodes are commonly placed both low and wide of their respective anatomic sites.	[15]
2007	Investigators evaluated the incidence of lead misplacement in the cardiology outpatient clinic (739 electrocardiograms) and the intensive care unit (99 electrocardiograms). Morphologic changes suggestive of lead misplacement included: abnormal R progression in the precordial leads, negative P waves in lead I and /or II, positive P wave in lead aVR, QRS axis between 180o and -90o, and very low (<0.1 mV) amplitude in an isolated peripheral lead. Based on these criteria, electrode misplacement was suspected in 37 electrocardiograms and confirmed in seven. The frequency of electrocardiogram artifact due to switched electrodes was 4.0 percent (4 electrocardiograms) at the intensive care unit and 0.4 percent (3 electrocardiograms) at the outpatient clinic. Therefore, the frequency of errors in electrocardiogram performance was significantly greater (P-value = 0.005) in an acute medical care setting.	[18]
2008	A total of 119 participants including 72 doctors (20 cardiologists and 52 non-cardiologists), 37 nurses, and 10 cardiac technicians were asked to mark on diagrams the positions of the precordial electrodes V1 to V6. The correct position of V1 was only identified by 90 percent of cardiac technicians, 49 percent of nurses, 31 percent of non-cardiologist physicians, and only 16 percent of cardiologists. In addition, V5 and V6 were also frequently mispositioned on the lateral chest wall.	[14]
2012	The investigators hypothesized that incorrect electrode placement has a reasonable chance of changing the diagnosis of an echocardiogram. The researchers found that displacing leads V1 and V2 in the second intercostal space (instead of the fourth intercostal space) also resulted in offsetting the placement of the other precordial leads. They observed that there was a 17 percent to 24 percent chance that the diagnostic interpretation of the electrocardiogram would be different based on the lead misplacement.	[19]
2020	The incidence and economic burden to healthcare of precordial lead mispositioning were evaluated. During a consecutive period of 12 months, 9,424 outpatient electrocardiograms were performed; 1,018 (10.8 percent) were determined to being possibly being falsely labeled as some type of myocardial infarction suggesting underlying coronary artery disease. The investigators concluded that the abnormal electrocardiograms resulted in false diagnoses and subsequent unnecessary cardiovascular testing with not only increased risk and cost to the patient but also increased financial burden to the national healthcare in other amounts of billions of dollars annually.	[2]