Stability of pacemaker parameters in cardiac amyloidosis patients

Abstract Cardiac amyloidosis is a rare disease due to the deposition of amyloid fibrils in the heart. Clinical manifestation of the heart includes restrictive heart failure and arrhythmia, when myocardium and conduction system are involved respectively. Arrhythmia can present as atrioventricular block (AVB), and sick sinus syndrome (SSS), therefore cardiac amyloidosis may require permanent pacemaker implantation. However, the stability of pacemaker parameters in cardiac amyloidosis patients remains unknown. We conducted an observational retrospective study of patients diagnosed with cardiac amyloidosis who underwent permanent pacemaker implantation from January 1, 2011 to December 31, 2019. Base-line data were obtained via Medical Record System. Data of pacemaker parameters were obtained via pacemaker programming at the time of implantation and last follow-up at the clinic. A total of 10 patients were included in our study, among which 5 patients underwent cardiac biopsy and showed positive result, 4 patients showed positive biopsy result of other tissue and characteristic echocardiography result of restrictive diastolic dysfunction, 1 patient was diagnosed with primary systematic amyloidosis (AL) involving kidney and advanced atrioventricular block. Amyloidosis type of the 10 patients were primary systemic amyloidosis (AL). Among the 10 patients, 3 were female (30.0%), and the mean age was 61.3±3.9. All patients met the indication for permanent pacemaker implantation, including 9 SSS and 1 advanced AVB. 9 patients were implanted with DDD, and 1 with VVI. The middle survival time was 446 (331, 728) days from the time of implantation to last follow-up (June 30, 2020). Two patients died due to disease progression. As for the 7 patients whose baseline and follow-up data were both obtained, pacemaker parameters at baseline were as followed: Atrial Impedance 477.8±115.0 Ω, Atrial P Wave 1.30±0.70 mV, Atrial Threshold 0.75±0.16 V@0.4ms, Ventricular Impedance 551.3±233.4 Ω, Ventricular R Wave 7.99±4.66 mV, Ventricular Threshold 0.76±0.15 V@0.4ms. Pacemaker parameters at follow-up were as followed: Atrial Impedance 426.2±93.2 Ω, Atrial P Wave 1.34±0.71 mV, Atrial Threshold 1.59±1.51 V@0.4ms, Ventricular Impedance 405.8±41.6 Ω, Ventricular R Wave 10.69±6.53 mV, Ventricular Threshold 1.80±1.88 V@0.4ms. Most patients relieved from cardiac symptoms and severe cardiac complications. A relatively short-term follow-up indicated elevation of Ventricular Threshold (P=0.028), and analysis of other parameters showed insignificant results. Elevation of Ventricular Threshold may be explained by the progression of amyloid fibrils deposition in the heart. Ventricular Threshold of one patient significantly increased from 1.0 V to 6.0 V at 3-month follow-up. Since all patients underwent chemotherapy for the primary amyloidosis, stability of pacemaker parameters may be another way for evaluation. Long-term follow-up is needed for further evaluation. Funding Acknowledgement Type of funding sources: None.