A 76-year-old male attended clinic for routine annual follow up of a dual chamber pacemaker which was implanted just over 2 years prior for bifascicular block and multiple episodes of syncope. Presenting rhythm over the device lifetime had typically been sinus rhythm with <5% VP. The following lead parameters were measured:
- RV lead impedance – 699 ohms (bipolar), 523 ohms (unipolar);
- R wave amplitude – 6.1 Mv;
- RV lead threshold – 7 V @ 1.5 ms (bipolar), >7.5 V @ 1.5m s (unipolar) (previously 1.4 V @ 0.4 ms bipolar);
- implant parameters;
- RV lead impedance – 1,063 ohms (bipolar);
- R wave amplitude – 17.9 Mv; and
- RV lead threshold – 0.5 V @ 0.4 ms.
The patient was asymptomatic, with a normal echo. Around 1 month later, he presented to clinic with stabbing chest pains following a hip replacement that he was taking prophylactic blood thinners for. Testing showed that the RV lead was not capturing at max output of 7.5 V @ 2 ms and the R wave had dropped to 1.8 Mv. Repeat echo remained normal.
Another month later, the patient presented to A&E with chest pains and a sensation that the pacemaker was delivering shocks. The CT report from the previous week was chased and revealed that the tip of the RV lead was ‘beyond the confines of the myocardium and abutting the pericardium… No evidence of pericardial effusion’.
The patient was admitted to hospital to wait for transfer to a tertiary centre for system extraction. A further pacing check was performed, which found the R wave had deteriorated to the point where the device was no longer able to sense.
We have also seen another patient the same week who again presented 2 years post implant, but with pericardial effusion which required draining. The post-procedure CT showed an RV lead tip perforation and the device was checked. There was no pacing at max output and no sensing. This patient also exhibited a significant impedance drop from 1,600 ohms to 650 ohms, with a bipolar threshold at 6 weeks of 2V @ 1 ms.
It is not clear how many cases there are of perforation in asymptomatic patients or those who do not present with pericardial effusion due to low suspicion or assumption of chronic lead deterioration. However, Sidhu, Ranjani and Rinaldi have presented a case where an asymptomatic patient underwent new RV lead implant due to increased threshold of 1.75 V @ 1 ms.1 The patient was investigated for perforation of the new lead due to new onset of symptoms. It was assumed that the new RV lead had perforated the RV, however it was discovered on CT that the chronic 14-year-old lead was the culprit, which lead to the patient needing a further procedure to extract the lead.
RV lead perforation is mostly expected to be an acute complication leading to pericardial effusion and cardiac tamponade, however there is evidence that some patients are presenting with chronic perforation or microperforation who may exhibit atypical symptoms and lead measurements. If there is a rise in bipolar RV threshold post implant (especially if accompanied by any significant drop in pacing impedance), then unipolar threshold should be tested and documented. Patients with a higher unipolar threshold can then be highlighted to their consultant cardiologist and investigated for suspected lead perforation in the early stages, and potentially avoid a late presentation with patient compromise. ❑
