916The impact of anesthesia choice on subcutaneous implantable cardioverter defibrillator outcomes: acute and one year results from the post approval study

Funding Acknowledgements

This study was financially supported by Boston Scientific

The influence of anesthesia technique on the outcomes of subcutaneous implantable cardioverter defibrillator (SICD) implantation has not been prospectively evaluated.

The aim of the present analysis was to characterize the effect of anesthesia choice acutely and over a year follow-up in the large "real-world" cohort of the SICD Post Approval Study (SICD-PAS).

Patients received either general anesthesia (GA), conscious sedation (CS), or monitored anesthesia care (MAC) at the implanting physicians" discretion.  Acute results and complications over one year were compared between GA, CS and MAC.

1,631 patients were studied.  64.3% received GA , 29.2% received CS and 6.6% received MAC.  Procedure times were shortest for MAC versus GA and CS (Table 1).  Cross-over from CS and MAC to GA occurred in 2.9% and 1.9% of procedures, respectively.  The mean left ventricular ejection fraction (LVEF) was lower in the MAC cohort compared with GA and CS.  GA patients were less often discharged the same day than CS and MAC.  Patients who had GA were more likely to have had intra-operative DFT testing, while successful DFT testing at implant did not differ among groups (Table 1).  At one year, freedom from total complications did not differ between groups (93.3% for GA, 92.9% for CS and 87.8% for MAC, p = 0.095) nor did freedom from inappropriate shocks (94% for GA, 94.2% for CS, 88.9% for MAC, p = 0.138) nor appropriate shocks (95.8% for GA, 95% for CS, 95% for MAC, p = 0.747).

All three anesthesia techniques had similar acute and one year outcomes but, despite having worse LVEF, patients who received MAC had shorter procedure times and infrequently required conversion to GA.  GA was associated with higher rates of next day patient discharge.  These results suggest that MAC may be preferred for the majority of patients. This observation should be confirmed with prospective trials.

Table 1:Characteristics and Outcomes Parameter Conscious Sedation General Anesthesia Monitored Anesthesia Care P value Gender[%(N/Total)] Male 68.1 (324/476) 69.3 (726/1048) 66.4 (71/107) 0.77 Age (years) mean ± SD 54 ± 15 53 ± 15 54 ± 13 0.61 Body Mass Index mean ± SD 30 ± 7 30 ± 8 29 ± 6 0.41 Creatinine (mg/dL) mean ± SD 2 ± 2 2 ± 4 2 ± 2 0.43 LVEF (%) mean ± SD 33 ± 15 32 ± 15 26 ± 9 <0.001 Procedure Time (min) mean ± SD 85 ± 42 75 ± 33 65 ± 30 <0.001 Same Day Discharge % 70.3% 64.3% 72.6% 0.03 DFT Attempted % 84% 89.1% 81.3% 0.004 Successful DFT % 98.7% 98.6% 98.8% 0.97

An approach to salvage a "frozen" pacing lead

We report our experience with the use of an orthopedic drill to remove "frozen" pacemaker leads from the connector block during pacemaker generator replacements. Three cases are reported in which the leads were salvaged successfully using this technique.

Calcium-induced sensitization of the central helix of calmodulin to proteolysis

The rate of proteolysis of trypsin-sensitive bonds was used to examine the nature of the structural changes accompanying Ca2+ and Mg2+ binding to calmodulin. In the Ca(2+)-free form, the rates of proteolysis at Arg-106 and Arg-37 are rapid (greater than 300 and 28 nmol min-1 mL-1, respectively), the bonds at Arg-74, Lys-75, and Lys-77, in the central helix, are cleaved more slowly (10 nmol min-1 mL-1), and a lag in the cleavage at the remaining bonds (Lys-13, Lys-30, Arg-86, Arg-90, and Arg-126) suggests that they are not cleaved in the native protein. High concentrations of Ca2+, but not Mg2+, almost completely abolish proteolysis at Arg-106 and drastically reduce the rate of cleavage at Arg-37. Both Ca2+ and Mg2+ exert a moderate protective effect on the proteolysis of the central helix. These results suggest that the F-helix of domains III and, to a lesser extent, the F-helix of domain I are somewhat flexible in the Ca(2+)-free form and are stabilized by Ca2+. Whereas full occupancy of the four Ca(2+)-binding sites produces little change in the susceptibility of the central helix to proteolytic attack, binding of two Ca2+ produces a 10-fold enhancement of the rate of proteolysis in this part of the molecule. We propose that at intermediate Ca2+ levels the flexibility of the central helix of calmodulin is greatly increased, resulting in the transient formation of intermediates which have not been detected by spectroscopic techniques but are trapped by the irreversible action of trypsin.