Recurrent syncope associated with paroxysmal supraventricular tachycardia in a Devon Rex cat diagnosed by implantable loop recorder

Abstract

A 9-year-old male neutered Devon Rex cat was presented for continued investigations following a 7-year history of recurrent syncope. Previous diagnostic tests, including 24h (Holter) electrocardiographic monitoring, had failed to identify the aetiology of such episodes, and former empirical treatment with atenolol had not provided satisfactory control of the clinical signs. A conclusive diagnosis was eventually achieved using an implantable loop recorder (Reveal), which identified paroxysmal supraventricular tachycardia (SVT) associated with a syncopal episode. Treatment with oral sotalol was instituted and, 18 months after initiation of anti-arrhythmic therapy, no further syncopal episodes have been observed by the cat's owners.

Fig 1.

Resting ECG (lead II, 10 mm/mV, 25 mm/s) recorded as a part of the initial diagnostic investigation for recurrent syncope. The trace shows a normal sinus rhythm with a heart rate of approximately 170 bpm. There is no clear evidence of ventricular pre-excitation (short PR intervals) that would suggest the presence of an accessory conduction pathway.

Fig 2.

(A) The ILR (Reveal Plus 9526) and (B) final phase of the surgical implantation in a subcutaneous pocket created at the level of the cranio-ventral region of the left side of the thorax.

Fig 3.

(A) ECG strip obtained from the interrogation of the ILR after surgical implant in the patient. The trace shows a normal sinus rhythm with heart rate of approximately 180 bpm. (B and C) Two samples of ECG trace recorded by the ILR during a syncopal episode. The arrowhead indicates the manual activation operated by the owner during the episode. The traces show SVT with a heart rate of approximately 420 bpm. The presence of QRS alternans would suggest retrograde conduction.