Background: Ventricular preexcitation is common. Dilated cardiomyopathy is usually the result of longstanding tachyarrhythmia. We demonstrated a causal relationship between ventricular preexcitation and dilated cardiomyopathy in the absence of recorded tachyarrhythmias. This relationship appears to be accessory pathway (AP) location-specific.
Patients and Methods: 10 consecutive children, (age range 0.6 to 17 years) were studied. All had ventricular preexcitation on the ECG, with the vector of the AP suggesting a right sided paraseptal location. None had had a documented tachyarrhythmia; however all had evidence for dilated cardiomyopathy (DCM), with LVEDD>97th centile for weight, and LV FS <25% on M-mode echocardiography. Diagnostic cardiac catheterization was performed in the first 4 patients, in whom the LVEDP was normal. Myocardial biopsy findings did not suggest myocarditis. Metabolic screening, family history and viral screening were negative.
Procedures and results: Eight of the 10 patients underwent EP study, despite the absence of tachyarrhythmia (or symptoms suggestive thereof). The AP had a right sided septal location in 7, and was a fasciculo-ventricular pathway in one(hitherto considered to be a benign finding). All APs were successfully ablated; 2 patients had spontaneous loss of preexcitation during follow-up. Loss of preexcitation (following ablation or spontaneously) was associated with complete recovery of LV function in 9/10 patients, with the most recent patient showing improved function.
Conclusions: Right sided septal APs with overt preexcitation may result in marked ventricular dsysynchrony, which mimics DCM. A causal relationship between such APs and DCM is confirmed by normalisation of ventricular function following loss of preexcitation.