GB Pant's cardiology team demonstrates novel postural variations in ICD lead parameters, case reported in EHJ.
Figure 1. Electrogram recording showing high frequency, high amplitude noise signal on ventricular electrogram leading to an antitachycardia pacing therapy (shown as STIM annotation) which is then followed by 30 J high voltage shock. No noise is detected on atrial electrogram trace.
Table 1
In a first of its kind case-report, interventional cardiologists from Delhi's GB Pant have described a unique postural variation that can unmask an underlying dysfunction in Riata Implantable-cardioverter-defibrillator (ICD) leads. This interesting case report has report has now been published in the European Heart Journal-Case reports.
Riata implantable cardioverter-defibrillator (ICD) leads are prone to a unique type of mechanical lead failure causing conductor externalization (CE) which may be complicated by a delayed-onset electrical lead failure (ELF).
A 60-year-old male with symptomatic, severe ischaemic cardiomyopathy, and atrial fibrillation following a prior anterior wall myocardial infarction received a dual-chamber ICD with 7F-RiataST ventricular lead as a primary prevention strategy against sudden cardiac death in 2008. In 2017, a pulse generator replacement was performed for elective replacement indicator status.
At that time, CE was noted in the ventricular lead but the electrical lead parameters were normal, hence lead replacement was decided against and the patient was closely followed up thereafter. Four years later, the patient presented with multiple ICD shocks within 48 h.
ICD interrogation showed noise on the ventricular electrogram (EGM) channel that was detected as ventricular fibrillation (VF) episodes, triggering inappropriate ICD therapy (five ICD detected VF events within 24 h triggering three antitachycardia pacing therapies and one shock). (Figure 1)
"What was unique about this case was that the lead impedance was normal when we tested the patient in our OPD although his impedance chart trend chart showed bizzare values over the last 1 week" notes author Dr. Abhimanyu, MBBS, MD, DM.
To address the discrepancy between the recent high impedance values in trend graph and the normal value recorded in supine posture, we performed lead interrogation in the sitting position. The ventricular pacing threshold, lead impedance and R-wave amplitude worsened dramatically in sitting posture while atrial lead parameters remained unchanged. (Table 1)
A new ventricular lead was then implanted and the old lead abandoned. The patient has not experienced any device therapy in the follow-up period. Riata lead electrical dysfunction correlates with time since implant and impaired EF is an independent predictor of ELF in these leads. This is for the first time that a postural variation during ICD interrogation has been reported.
The authors hypothesize that due to gravitational forces acting on the heart in sitting posture, the externalized lead components of the fixed ventricular lead are stretched which causes worsening of electrical parameters. This probably accounted for the discrepancy between impedance values in supine position and impedance trend chart.
"This dynamic manoeuvre during lead interrogation can unmask an underlying conduction abnormality of externalized leads and probably aid in early detection of ELF", concluded the authors.
Chief author of this report Dr. Abhimanyu is a writer for cardiology section in medical dialogues.
Source: European Heart Journal: https://doi.org/10.1093/ehjcr/ytab491
