Role of Electrocardiogram (EKG) in Kawasaki Disease
The EKG has limited diagnostic and prognostic value in Kawasaki disease and should not be used as a primary tool for detecting coronary artery involvement; echocardiography is the imaging modality of choice for cardiac assessment. 1, 2
Primary Cardiac Assessment Strategy
Echocardiography, not EKG, should be the initial imaging modality for cardiac assessment in children with Kawasaki disease due to its high sensitivity and specificity for detecting abnormalities of the proximal coronary artery segments. 2
The initial echocardiogram should be performed as soon as Kawasaki disease is suspected, though treatment should not be delayed by the timing of the study. 2
For uncomplicated cases, echocardiographic evaluation should be performed at diagnosis, at 2 weeks, and at 6-8 weeks after onset of disease. 1, 2
EKG Findings in Kawasaki Disease
While EKG abnormalities are common in Kawasaki disease, they lack specificity and predictive value:
EKG abnormalities occur in approximately 80% of patients with Kawasaki disease, with the most common findings being ST segment changes, increased Q/R ratio, and prolonged corrected QT interval. 3
Other EKG findings may include PR prolongation, relative low voltage, ST depression or elevation, increased T wave height, and relative T wave flattening. 4
EKG changes do not reliably predict coronary artery involvement. Studies show that EKG abnormalities suggestive of carditis occur in 74% of patients with normal coronary arteries, with no significant difference compared to those with coronary artery dilatation. 3
Limited Predictive Value of EKG Parameters
Recent research has explored specific EKG markers with mixed results:
A QTc interval <385 ms in lead V6 during the acute period was associated with a 2.5-fold increased risk of coronary involvement (OR 2.5; 95% CI 1.2-5.3), though this finding requires validation. 5
Paradoxically, patients with Kawasaki disease and coronary involvement actually have shorter QTc values compared to controls (395 ms vs 410 ms), not prolonged intervals as might be expected. 6
The Tp-Te/QT ratio and other ventricular repolarization parameters have not shown reliable association with coronary involvement in either acute or recovery periods. 5
T-wave vector magnitude (RMS-T) can differentiate Kawasaki disease from normal children but does not distinguish patients with coronary artery anomalies from those without. 6
Clinical Implications and Pitfalls
Common pitfall: Relying on EKG findings to rule out or predict coronary involvement in Kawasaki disease. The EKG should not delay or substitute for echocardiographic evaluation. 1, 2
Guidelines from the American College of Cardiology/American Heart Association classify "most ECG abnormalities" as Class I indications for echocardiography in pediatric patients, reinforcing that EKG abnormalities should prompt echocardiographic assessment rather than serve as standalone diagnostic tools. 1
If ischemic changes are observed on EKG in patients with known coronary lesions, these findings are similar to those seen in adults and warrant immediate echocardiographic and potentially angiographic evaluation. 4
Appropriate Use of EKG
The EKG may be obtained as part of the initial evaluation but should be interpreted in the context of:
Baseline documentation of cardiac electrical activity at diagnosis. 1
Monitoring for arrhythmias in patients with known myocarditis or coronary involvement, as myocarditis is universal in acute Kawasaki disease. 2
Serial assessment in patients with documented coronary abnormalities or ventricular dysfunction requiring more frequent monitoring. 1, 2
The bottom line: Order an echocardiogram, not an EKG, when evaluating for cardiac involvement in Kawasaki disease. The EKG may be obtained for baseline documentation but should never delay echocardiographic assessment or treatment initiation. 1, 2