April 2018

Tachycardia during an Upgrade to CRT-P

Jason Collinson – Chief Cardiac Physiologist
Essex Cardiothoracic Centre, Basildon and Thurrock University Hospital
Twitter: @cardiacjase


A 68 year old male with a history of coronary artery bypass grafting, moderately impaired left ventricular systolic dysfunction and bradycardia requiring permanent dual chamber pacemaker implantation was referred to our centre for upgrade to a cardiac resynchronisation therapy pacemaker (CRT-P).  Over the last few months he had been complaining of increasing breathlessness on exertion and palpitations.  Interrogation of his device immediately pre implant showed a high ventricular pacing burden at 80%. Lead measurements were satisfactory and there was a good underlying rhythm of sinus bradycardia with occasional ventricular ectopy at 45 bpm.  The intrinsic rhythm was well tolerated and the pacemaker mode was reprogrammed to VVI with a base rate of 40 bpm.  Diathermy was made available at the operators request and the patient was set up in the usual fashion.  Shortly after starting the procedure the following ECG was observed.

Figure 1
Six lead ECG trace observed shortly after starting the procedure. Sweep speed 25 mm/s. Gain at 0.5mm/mV


Which answer best explains the ECG trace?

  • Ventricular Tachycardia

  • Rate adaptive pacing

  • Tracking of atrial fibrillation

  • Rate regularisation algorithm