Cardiac memory in patients with intermittent Wolff-Parkinson-White syndrome

Pediatric T-wave memory after accessory pathway ablation in Wolff-Parkinson-White syndrome

BACKGROUND

Altered ventricular depolarization due to manifest accessory pathway conduction (ie, Wolff-Parkinson-White syndrome) leads to repolarization abnormalities that persist after pathway ablation. The term T-wave memory (TWM) has been applied to these changes, as the postablation T-wave vector "remembers" the pre-excited QRS vector. In adults, these abnormalities can be misinterpreted as ischemia leading to unnecessary interventions. To date, no comprehensive studies have evaluated this phenomenon in the pediatric population.

OBJECTIVE

The purpose of this study was to define TWM in the pediatric population, identify preablation risk factors, and delineate the timeline of recovery.

METHODS

Pre- and postablation electrocardiograms (ECGs) in patients ≤25 years were analyzed over a 5-year period. Frontal plane QTc interval, T-wave axis, QRST angle, and T-wave inversions were used to identify patients with TWM. Univariate analysis was performed to determine the association of preablation ECG features with the outcome of TWM.

RESULTS

TWM was present in 42% of pediatric patients, with resolution occurring within 3 months of ablation. Preablation QRS axis <0° was a strong predictor of TWM (odds ratio [OR] 15.2; 95% confidence interval [CI] 5.7-40), followed by posteroseptal pathway location (right posteroseptal-OR 8.9; 95% CI 4.2-18.8; left posteroseptal-OR 6.1; 95% CI 1.7-22.3). The degree of pre-excitation had a modest association with the development of TWM. No adverse events were observed.

CONCLUSION

TWM is less common in children compared to adults, and normalization occurred within 3 months postablation. The most predictive features for the development of TWM include a leftward pre-excited QRS axis and posteroseptal pathway location.

Clinical Dilemma - Cardiac Memory vs Myocardial Ischemia

Cardiac memory (CM) is a commonly unrecognized entity in which electrocardiograph (EKG) changes demonstrate T wave inversions (TWI) that appear consistent with ischemia. Inability to recognize and distinguish CM from actual ischemia can be a burden for both patients and hospitals, leading to unnecessary hospital admission, cardiac testing, and cardiac catheterization. Simple EKG analysis and meticulous interpretation of T-wave axis and morphology can help differentiate between the two. We present a case with such a dilemma, and an overview literature and physiology behind this entity.

Cardiac memory-persistent T wave changes after ventricular pacing

Cardiac memory is an uncommonly recognized entity in which T wave inversions on electrocardiogram (EKG) appear consistent with ischemia. Persistent deep T wave inversions are seen after return of normal depolarization in leads where the T waves were normal before pacing. These changes are generally recognized to occur in association with artificial pacemakers but may occur with other entities with intrinsic ventricular ectopic focus of depolarization, such as intermittent left bundle branch block. Although consideration of ischemia should be given priority, awareness of the benign nature of cardiac memory may allow some patients to avoid unnecessary work-up and admission. Sometimes the diagnosis cannot be confirmed definitively in the Emergency Department (ED) because many patients who have pacemakers also have coronary artery disease and only after a negative work-up for ischemia can one retrospectively presume cardiac memory as the likely etiology.