Leadless pacemaker implant in patients with a history of open heart surgery: experience with the Micra transcatheter pacemaker

Background

The Micra transcatheter pacemaker has demonstrated a favorable safety and efficacy profile relative to transvenous pacing. Patients with a history of open heart surgery have a higher risk of complications with transvenous pacemakers during follow-up. The experience with leadless pacemakers among a large cohort of patients with a history of open heart surgery has not been reported.

Objective

To report outcomes in patients with a history of open heart surgery undergoing Micra implant.

Methods

Patients undergoing Micra implant from the Micra Transcatheter Pacing Post-Approval Registry (PAR) were included in the analysis. Baseline and procedural characteristics, major complications, and electrical performance were compared among patients with vs. without history of cardiac surgery.

Results

A total of 331 out of 1815 (18.2%) patients had a history of open heart surgery, underwent Micra implant, and were followed for 19.4±10.4 months. The mean age was 74.6±13.5 years, 40% were female. The most common cardiac surgery was aortic valve surgery (71%) followed by mitral valve surgery (39%). Patients with prior open-heart surgery were more likely to have contraindications to transvenous pacing, were more likely to be on oral anticoagulants, and had more co-morbidities including atrial fibrillation, heart failure, and coronary artery disease (all p<0.005). Implantation was successful in 327 of 331 patients (98.8%) with a median procedure time of 29 minutes. Mean pacing capture thresholds (PCTs) at implant were 0.66±0.51V and remained stable through follow-up. There were 11 major complications in 10 cardiac surgery patients, with no device or procedure-related infections reported. The major complication rate was 3.1% (Figure) and was not significantly different than that of patients without a history of open heart surgery (HR: 0.85, P=0.640). There was 1 cardiac perforation (with no intervention required) in the open heart surgery group (0.3%) and there were 14 cardiac perforations (0.94%, P=0.332) in the non-open heart surgery group of which 10 required intervention.

Conclusion

The Micra transcatheter pacemaker can be safely implanted in patients with a history of open heart surgery, with a similar long-term safety profile to patients without a history of open heart surgery. Importantly, there were no device-related infections reported in either group.

Risk of Major Complication

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): Medtronic, Inc.

Long-term follow-up of persisting mixed chimerism after partially T cell-depleted allogeneic stem cell transplantation

Using red cell phenotyping (RCP) and/or cytogenetics (CYT) we identified 19 patients with persisting mixed chimerism (MC) among 231 patients transplanted with partially T cell-depleted stem cell grafts from HLA-identical siblings. Persisting MC is defined as MC for more than 2 years in patients without any evidence of relapse. Median leukemia-free survival in these patients was 150 (range, 50-218) months. Diagnoses were ALL (n= 10); AML (n = 2); CML (n = 2); NHL (n = 2); MDS (n= 1); MM (n = 1) and SAA (n = 1). Purpose of this study was the long-term follow-up of MC and definition of patterns of chimerism in the various subsets of PBMCs and granulocytes. Using a PCR-STR technique CD3(+)/CD4(+) (T4 lymphocytes), CD3(+)/CD8(+) (T8 lymphocytes), CD45(+)/CD19(+) (B lymphocytes), CD45(+)/CD14(+) (monocytes), CD45(+)/CD15(+) (granulocytes) and CD3(-)/CD56(+) (NK-cells) were analyzed. The majority of patients with persisting MC were conditioned with a less intensive conditioning regimen and had little GVHD. Sequential monitoring of the chimerism resulted in a group of patients (n = 7) with very slow transient mixed chimerism that resulted in complete DC after median 7 years. Another nine patients had a relatively high percentage of persisting autologous cells for a median of 12 years and in three patients we observed a stable low percentage of autologous cells. Only two out of 19 patients (AML-CR1, CML-CP1) relapsed during follow-up. Both patients had a relatively high percentage of autologous cells. Chimerism in granulocytes and PBMC subsets was analyzed at a median of 8 years after SCT in nine patients. In five patients mixed chimerism simultaneously detected by RCP and CYT was associated with MC in all subsets. Within each individual patient the percentages of donor and recipient cells were very different between the different subsets. Two CML-CP1 patients were mixed chimera in only two subsets and in one patient these subsets represented pending relapse. In another two patients mixed chimerism with a very low number of autologous red cells was not found in the PBMCs because of the different sensitivity level of the RCP and the PCR-STR technique. We conclude that in patients with persisting mixed chimerism after partially T cell-depleted SCT a remarkable number of patients had lymphoid malignancies, the majority of the patients were conditioned with less intensive conditioning regimens and the mixed chimerism was not correlated with relapse. Chimerism in granulocytes and PBMC subsets did show great intra-individual differences in the subsets and these data correlated well with RCP and CYT data with the exception of the NK cells.

Immunotherapy with monoclonal anti-idiotypic antibodies: tumour reduction and lymphokine production

A patient with a B-cell chronic lymphocytic leukaemia was treated with a murine IgG1 monoclonal anti-idiotypic antibody (MoAb anti-id). After a total of 773.2 mg MoAb anti-id had been administered with a maximum daily dose of 83.2 mg, 90% tumour reduction was established within 2 weeks. Although in vitro the tumour cells were stimulated by MoAb anti-id no signs of tumour cell activation were observed in vivo during therapy with MoAb anti-id. The rapid tumour reduction suggests that the proliferation-enhancing property of anti-id is not a contra-indication for immunotherapy. The FcR II receptors on the patients monocytes could interact with the IgG1 monoclonal used. MoAb anti-id administration induced strongly decreased platelet counts, dependent on the amount of serum idiotype that had to be cleared. Antibody administration activated the macrophage/monocyte system, reflected in the neopterin profile, resulting in TNF alpha production and simultaneously strong reductions of circulating tumour cells. The partial remission lasted 3 months, then the tumour reappeared. These data show that a straightforward therapy with MoAb anti-id, in itself, has a strong potential, but is not sufficient to eradicate the tumour permanently. Further study will be needed to improve the clinical results with this kind of therapy.

Phenotypic and functional changes of tumour cells from patients treated with monoclonal anti-idiotypic antibodies

In this paper data are presented indicating that immunotherapy with monoclonal anti-idiotypic antibodies (MoAb anti-id) can provoke different responses in the B-cell tumour concerned. With respect to the course of disease during and after immunotherapy, the in vitro findings may very well explain the in vivo observations in the two patients (D.E.F., B.O.R.) with B-cell chronic lymphocytic leukaemia (B-CLL) who were treated with MoAb anti-id. After initial tumour reduction, there was a recurrence of tumour cells with altered functional and phenotypic properties. In both cases the recurring tumour cells still expressed the same idiotype. In one patient (D.E.F.) the phenotypic changes (a surface Ig change from IgM, IgG, IgA, and IgD to weakly positive IgM and IgD) and functional changes (a 10-fold increase in [3H]thymidine uptake and a decreased idiotype secretion in vitro), together with the in vivo findings with respect to the course of disease--at relapse an impressive tumour regrowth rate with constant serum idiotype level--suggest that immunoselection might have taken place favouring the survival and relapse of a less mature, more aggressive tumour cell population with a lower idiotype expression. In the second patient (B.O.R.), the phenotypic changes (an isotype change from IgM and IgD to IgM with the loss of IgD, and a gradual decrease in expression of CD19 and CD24) and functional changes (a 10-fold increase of idiotype secretion in vitro), together with the in vivo finding that the serum idiotype level had increased 25-fold compared with the preimmunotherapy serum level with comparable tumour load, strongly suggest an immunotherapy-induced differentiation of the malignant B cell. We also describe an increased expression of CD74, detected by MoAb BoM22, on the recurring tumour cells of patient B.O.R., whereas the expression of HLA-DP, -DQ and -DR did not change. The significance of this finding is unclear.