Pre-excitation induced left ventricular dysfunction: A less known cause of cardiomyopathy in children.

A 7-year-old boy was diagnosed to have dilated cardiomyopathy with severe left ventricular (LV) dysfunction at 1 year of age. Although well compensated, his LV function remained impaired over the follow-up years. His electrocardiogram (ECG) was initially misinterpreted as left bundle branch block. However, on follow-up, it was recognized as a pre-excited ECG. The accessory pathway causing pre-excitation was implicated as the cause of LV dysfunction and dysynchrony as the mechanism. Radiofrequency ablation was done. His LV function and dimensions improved significantly over 6 months follow up.

INTRODUCTION

Ventricular pre-excitation through accessory pathways is being recognized to cause left ventricular (LV) dysfunction. Dysynchrony is hypothesized to be the possible mechanism. Pre-excited electrocardiogram (ECG), especially the posteroseptal accessory pathways can masquerade an ECG with Left bundle branch block (LBBB) pattern. Radiofrequency ablation of the accessory pathway may reverse the LV dysfunction.

CASE REPORT

A 7-year-old boy was diagnosed to have dilated cardiomyopathy (DCM) at the age of 1 year. Medical attention was sought then for lethargy, poor feeding, and rapid breathing. His echocardiography reportedly showed dilated ventricles and a LV ejection fraction of 25%. He had no preceding febrile illness. His ECG was misinterpreted as LBBB pattern. He was initiated on beta-blockers and angiotensin-converting enzyme inhibitors. He responded and had been on regular follow-up.

On the last several follow-ups at the centre where he was initially evaluated, he stayed symptom free but his LV dilatation or LV function did not improve. At 7 years of age, the family chose to have further follow-up at our center. In their visit, records were reviewed. ECG revealed short PR interval with delta wave [Figure 1], the accessory pathway was localized to right posterolateral area possibly. He had no history of palpitation; the echocardiogram showed the LV dilated with ejection fraction of 40% [Video 1].

Figure 1

Baseline electrocardiogram showing pre-excitation

On tissue doppler imaging (TDI), there was delay of 60-70 ms from the septal to lateral wall [Figure 2]. There was no paradoxical septal motion. The septal to posterior wall motion delay (SPWMD) was not significant. A possibility of accessory pathway induced dysynchrony was considered that could have possibly caused LV dysfunction.

Figure 2

Echocardiography before ablation showing dilation of left ventricle and dysynchrony between septal and lateral wall on the apical four chamber view

An electrophysiological study confirmed pre-excitation. The pathway effective refractory period was 250 ms. No attempt was made to induce tachycardia. The pathway was mapped to the posteroseptal area of the tricuspid annulus and was successfully eliminated [Figure 3]. The local atrial (A) Ventricular (V) electrograms were fused. The A and V separated in 6 s into delivery. The current was delivered for 60 s and the temperature and power achieved were 55°C and 30 watts, respectively. The immediate post-procedure echocardiogram revealed that there was no dysynchrony between the septal and lateral wall [Figure 4]. His follow-up echo showed that his ventricular dimensions normalized (from 48 to 42 diastolic and 38 to 28 mm end systolic after one year) and function was normal [Video 2].

Figure 3

Electrocardiogram after ablation showing normal PR segment

Figure 4

Echocardiography post ablation showing synchrony between the septal and lateral wall in the apical four chamber view

DISCUSSION

DCM in childhood is a diverse disorder with outcomes that depend on cause and age at presentation, as well as heart failure status. The annual incidence of DCM in children younger than 18 years was 0.57 cases per 100,000 per year.[1] In the cohort, the etiology could not be identified in majority of children (66%). In the remaining 34%, myocarditis (46%) and neuromuscular disease (26%) were the common causes. Etiology of DCM was an independent risk factor for subsequent events.

Accessory pathways causing ventricular dilatation and dysfunction were initially recognized in 2004 and subsequently in 2007.[23] This is distinct from tachyarrhythmia-induced cardiomyopathy which is better recognized and is most often seen with atrial tachycardia. Dysynchronous activation of the LV is implicated as the cause for LV dysfunction.

The exact prevalence of LV dysfunction in asymptomatic Wolff–Parkinson–White (WPW) is not systematically studied. Population-based studies that examined the natural history of asymptomatic WPW syndrome report a low prevalence. Moreover, the LV dysfunction was incidentally associated and not caused by pre-excitation.[4] However, studies specifically examining LV function in asymptomatic WPW report higher prevalence of LV dysfunction.[5] Tachyarrhythmia-related cardiomyopathy due to recurrent atrioventricular reciprocating tachycardia is uncommon. It is more often seen secondary to atrial tachycardia.

The reason why minor subsets of children with accessory pathway develop LV dysfunction is not known. Varied degree of pre-excitation may be a factor. Of the accessory pathways, right posteroseptal pathway is more commonly associated with LV dysfunction.[56] Moreover, manifest right posteroseptal ECG masquerades LBBB pattern. Recognizing pre-excitation as a cause for LV dysfunction is pertinent as it is reversible. Most reports have shown reversal of LV dilatation and restoration of LV function.[37] Recovery of cardiac function after radiofrequency ablation occurs over a variable period. Recovery as early as weeks to as late as 1.5 years has been reported.

In conclusion, ventricular dysfunction from preexcitation, distinct from tachycardiomyopathy, needs to be recognized. Ablation of the accessory pathway may improve the ventricular function. Further characterization of this phenomenon is warranted.