Atrioventricular accessory pathway unmasked by heart valve replacement

Abstract A 50‐year‐old male patient with a history of severe valvular regurgitation underwent mitral and aortic valve replacement surgery 3 months ago. Preoperative 12‐lead electrocardiogram presented atrial flutter (AFL) and atrial fibrillation. AFL complicated with ventricular pre‐excitation was observed on current admission. The potential mechanisms underlying these changes were considered multifaceted, and valve replacement procedure may be a rare incentive factor.


| C A S E PR E S E NTATI O N
indicated atrioventricular association. We considered the diagnosis of ECG was AFL complicated with intermittent ventricular pre-excitation, rather than ventricular tachycardia with exit block. The patient received further electrophysiological (EP) study, and after the AFL ablation, ventricular pre-excitation was observed in sinus rhythm. The AP was finally eliminated at the free wall of mitral valve with no AFL and wide QRS appeared in the Holter test before discharge ( Figure 3b).

| DISCUSS ION
The main finding of this case is that cardiac surgery may be a rare inducing factor to unmask the potential AP in normal heart F I G U R E 1 (a) Electrocardiogram (ECG) taken before valve replacement surgery revealed atrial fibrillation with Q waves in leads V 4 -V 6 . (b) ECG taken on 1 day postoperative indicated atrial flutter (3:1-5:1) Gopinathannair R respectively reported cases of right AP unveiled following tricuspid valve replacement (Gopinathannair et al., 2013;Simmers et al., 2006). In our case, the AP was ablated on the mitral F I G U R E 2 (a) Emergency electrocardiogram (ECG)-presented intermittent wide complex beats as bigeminy. (b) ECG recorded after using metoprolol and deslanoside. Irregular wide complex tachycardia was noted valve, which is consistent with the position of the valve procedure.
Hence, we suspected that the exposure of the AP may be associated with valve replacement surgery. Some potential reasons for the mechanism of pre-excitation following valve replacement procedure could be summarized as follows: First, since most APs were anatomically adjacent to the atrioventricular annulus, surgical procedure, such as innate valve incision and prosthetic valve suture, may change the structure of AP or surrounding tissues. As a result, the anterograde conductivity of AP could be increased by the source-sink relationship improved (Dhein et al., 2014). Moreover, the growth of myocardial cells or the new presence of electrical conduction through the suture line, or so called "acquired bypass tract" (Peinado et al., 2007), is another notable reason, which was mainly observed following Fontan procedure and orthotopic heart transplantation. Furthermore, valve replacement operation, particularly in sutureless AVR procedure, may have potential lesion to atrioventricular conduction system and The inspiration of this case is that making accurate differential diagnosis of wide QRS complex arrhythmia is particularly significant because the therapeutic principle is quite different, even opposite.
If this case was misdiagnosed as ventricular bigeminy or ventricular tachycardia with an exit block while antiarrhythmic drugs were thus administrated, the degree of pre-excitation and rapid ventricular rate may aggravate because of the further suppression of AVN. In our case, duration between the wide QRS complex and the flutter wave proceeded was equal in different ECG segments. Afterward, divider test (Figure 3a) indicated that the relation between the long RR interval and FL-FL interval was integer multiple. None of the above supported atrioventricular dissociation (Surawicz et al., 2001), and thus, ventricular tachycardia with an exit block could be ruled out. However, lacking of the Holter result before valvular surgery could be a flaw during this clinical course.

| CON CLUS ION
We presented a case of accessory pathway unmasking following valve replacement surgery. The mechanisms mainly included changes in source-sink relationship and impairment of conduction system caused by surgical procedure and antiarrhythmic drug use.
Accurate ECG investigation may contribute to make differential diagnosis and appropriate treatment strategy.

CO N FLI C T O F I NTE R E S T
The authors declared that they have no conflicts of interest to this work. We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.

AUTH O R CO NTR I B UTI O N S
Conceptualized the Study, provided software and resources, performed formal analysis, and wrote the original draft: Y. Li. Designed methodology, and wrote and revised the manuscript: ZL. Investigated the study, visualized the data, and administered the project: Y. Long.
Validated and curated data: Y. Li.

E TH I C A L A PPROVA L
The study complied with the edicts of the Declaration of Helsink (World Medical Association, 2013) and was approved by the patient and his family. Given that this is a retrospective case report, informed consent was waived.

DATA AVA I L A B I L I T Y S TAT E M E N T
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