A 60-year-old man with a dual-chamber implantable cardioverter defibrillator and severe dyspnea on exertion due to apical hypertrophic cardiomyopathy underwent a septal myectomy and radiofrequency maze procedure. Following the procedure a persistent delay in atrial sensing was observed and was most likely a result of iatrogenic conduction delay from right atrial ablation lines. These observations suggest that atrial conduction properties can be altered during the surgical maze procedure and should be considered in the differential diagnosis of sensing or pacing malfunction.
A 60-year-old male with apical variant hypertrophic cardiomyopathy and history of dual-chamber implantable cardioverter defibrillator 18 months before, nonsustained ventricular tachycardia and primary prevention of sudden cardiac death was admitted with New York Heart Association class III dyspnea on exertion that was refractory to medical therapy. He underwent an apical myectomy procedure along with left and right atrial radiofrequency maze procedures [
Prior to surgery, his dual chamber Medtronic Secura D224DRG was interrogated, and the device and lead function were found to be functioning normally.
The patient underwent successful cardiac surgery. A device interrogation was performed on postoperative day no. 1 while the patient was in atrial fibrillation/flutter, and atrial lead sensing was observed to be normal. For control of the atrial fibrillation, amiodarone 400 mg P.O. twice daily was initiated and metoprolol increased from 50 mg twice daily to 75 mg twice daily.
Two days following the surgery, the rhythm converted to sinus, and continuous telemetry revealed the following (Figure
A subsequent device interrogation was performed. Native p waves were sensed late, such that atrial sensing occurred 120 ms after the p wave occurred. p wave amplitude was 3.1 mV (Figure
Threshold testing was also performed and found to be normal. A portable chest radiograph was obtained and accounting for differences in technique showed no evidence of atrial lead macrodislodgement compared with preoperative location in the area of the right atrial appendage.
Because pacing requirements were minimal and ventricular pacing, sensing, and defibrillator thresholds adequate, the device mode was set to VVI at 40 bpm to allow for back-up pacing if needed.
Considering the recent radiofrequency maze procedure performed at the time of cardiac surgery, it was determined that the delayed atrial sensing most likely occurred as a result of surgically created conduction delay from ablation lines [
Diagram of right atrial maze ablation lines.
Following the maze procedure, the native p wave typically becomes smaller in amplitude, monophasic and has positive polarity [