Methods

Data and cross-sectional analyses were provided by the NCDR ICD Registry. Participating hospitals are required to submit periprocedural data on all Medicare patients receiving primary prevention devices. In addition, >80% of hospitals in the United States routinely submit standardized data on all patients. All procedures performed between April 1, 2010 and June 30, 2011 including single-chamber, dual-chamber, and cardiac resynchronization therapy (CRT) ICDs were screened for patients who underwent reimplant procedures. Patients requiring a thoracotomy were excluded.

Three separate groups consisting of patients who underwent initial ICD implant, repeat procedures with lead revision or replacement, and generator replacement only were analyzed. Initial implants consisted of procedures in patients with no previous pacemaker or ICD. A reoperation procedure with lead implantation or revision consisted of any reoperation procedure involving the implantation of a new lead, such as an upgrade from a previous pacemaker to an ICD requiring a defibrillation lead; upgrade of an ICD to a dual chamber ICD or CRT defibrillator; lead replacement or revision with or without lead extraction; device infection in which the leads are manipulated or replaced; or a malfunction because of a problem with atrial pacing, right ventricular pacing, left ventricular pacing, or lead-related defibrillation function. A reoperation with pocket-only procedure was defined as any reoperation procedure without involvement of a lead, such as a generator change only, a pocket revision, or a procedure to move the generator.

The primary outcome was in-hospital major adverse event during and after device procedure until the end of the hospital stay. These events included cardiac arrest, cardiac perforation, cardiac valve injury, conduction block, hematoma requiring reoperation, evacuation or transfusion, hemothorax, lead dislodgement, myocardial infarction, pericardial tamponade, set screw problem, pneumothorax, transient ischemic attack or stroke, urgent cardiac surgery, drug reaction, coronary venous dissection, infection requiring antibiotics, peripheral embolus, peripheral nerve injury, and venous obstruction. All complications occurred during the hospital stay for the given ICD procedure. Patients could have >1 complication recorded; multiple complications were not considered separately.

Statistical analyses were performed at the NCDR Analysis Center at Yale University. Baseline patient characteristics were compared using independent t tests, analysis of variance, and chi-square tests. Wilcoxon rank sum tests and Kruskal-Wallis tests were used when normality assumptions of continuous variables were violated. Tests comparing characteristics of patients who underwent reimplantation procedures and initial ICD implantation were also performed. Total number of in-hospital complications associated with reimplantation was tabulated according to the subgroups categorized based on the reason for ICD procedure, and simple proportions were calculated. To examine potential predictors of in-hospital complications in patients who underwent reimplantation, univariate hierarchical logistic regression models based on the baseline patient variables adjusting for clustering on center were first fitted. A similar multivariable hierarchical logistic regression model adjusting for clustering was developed by including all variables significant at the univariate level. Each variable was evaluated for significance and confounding. Variables no longer significantly contributing to the overall model and that did not produce confounding of other variables were dropped from the model. Variables having the highest p-values were evaluated first, and this step was performed iteratively until all variables in the model met the inclusion criteria of p <0.05. Before modeling, categorical variable missing data were assumed to represent a “no” response. Continuous variable missing data were imputed with the median. SAS v9.2 was used for the analyses (SAS Institute, Cary, N C).

Results

Our analysis included 174,499 patient hospital visits. This included 92,751 initial ICD implants, 31,057 patients who underwent repeat procedures involving lead revision or replacement, and 50,691 patients who underwent generator-only procedures. A comparison of patient characteristics between patients with initial ICD implantation, repeat procedures involving lead replacement or revision, and repeat procedures involving the generator only are listed in Table 1 . Compared with new ICD implants, patients who underwent repeat procedures were older and more likely to be men; they had more atrial and ventricular arrhythmias and were more likely to have dual chamber or CRT devices with underlying paced cardiac rhythms. Compared with those who had pocket-only procedures, those who underwent repeat procedures involving lead implantation or revision had more heart failure with a lower ejection fraction, valvular heart disease, atrial arrhythmias, and cardiovascular co-morbidities.

End of expected battery life was the major reason for reimplantation in the pocket-only cohort (95.7%), compared with 28.1% in the lead implantation or revision cohort ( Table 2 ). Thirty-five percentage of the lead-related reimplant group was referred for an upgrade from a pacemaker to an ICD. Other reasons for a reimplantation with lead involvement included lead dislodgement or other reasons for lead revision (12.9%), infection (5.5%), device malfunction (3.2%), and advisory or recall (1.6%).

The incidence of adverse events in those patients who underwent initial ICD implantation was 2.6%. Overall, adverse event rates were significantly higher in patients who underwent reimplantation with lead manipulation (3.2%), compared with those with pocket-only procedures (0.6%) and initial implantation. There were significantly more patient deaths, cardiac events, hematomas, lead dislodgements, pneumothoraces, infections, and venous issues in the reimplant cohort with lead involvement compared with those without lead involvement and with initial implants ( Table 3 and Figure 1 ). Complications with pocket-only reimplantation procedures were significantly lower compared with reimplant procedures requiring a lead implantation or revision and compared with initial ICD implants. For every 100 patients who underwent lead reimplantation or revision instead of a pocket-only procedure, there would be an increase of 2.6 major adverse events.

Table 3

Incidence of in-hospital complications in patients undergoing reoperation procedures

Complication	Initial Implant	Reoperation With Lead Involvement	Pocket Procedure	p-Value
	n = 92571	n = 31057	n = 50691	Initial vs All Repeat Procedures	Reoperation With Lead Involvement vs Pocket-Only Procedure
All events	2382 (2.6%)	994 (3.2%)	302 (0.6%)	<0.001	<0.001
Discharge status—dead	318 (0.34%)	109 (0.35%)	52 (0.1%)	<0.001	<0.001
Cardiac arrest	243 (0.26%)	83 (0.27%)	40 (0.08%)	<0.001	<0.001
Cardiac perforation	67 (0.07%)	22 (0.07%)	2 (0.0%)	<0.001	<0.001
Cardiac valve injury	1 (0.0%)	0	0	NA	NA
Conduction block	38 (0.04%)	5 (0.02%)	1 (0.0%)	<0.001	0.032
Hematoma requiring reoperation, evacuation or transfusion	264 (0.28%)	201 (0.65%)	86 (0.17%)	0.014	<0.001
Hemothorax	24 (0.03%)	21 (0.07%)	5 (0.01%)	0.465	<0.001
Lead dislodgement	869 (0.94%)	349 (1.12%)	29 (0.06%)	<0.001	<0.001
Myocardial infarction	27 (0.03%)	4 (0.01%)	2 (0.0%)	0.001	0.209
Pericardial tamponade	92 (0.1%)	22 (0.07%)	2 (0.0%)	<0.001	<0.001
Set screw problem	33 (0.04%)	17 (0.05%)	5 (0.01%)	0.309	<0.001
Pneumothorax	299 (0.32%)	112 (0.36%)	27 (0.05%)	<0.001	<0.001
Transient ischemic attack or stroke	47 (0.05%)	22 (0.07%)	7 (0.01%)	0.129	<0.001
Urgent cardiac surgery	22 (0.02%)	5 (0.02%)	2 (0.0%)	0.014	0.113
Drug reaction	55 (0.06%)	19 (0.06%)	17 (0.03%)	0.164	0.068
Coronary venous dissection	128 (0.14%)	42 (0.14%)	11 (0.02%)	<0.001	<0.001
Infection requiring antibiotics	85 (0.09%)	44 (0.14%)	16 (0.03%)	0.187	<0.001
Peripheral embolus	12 (0.01%)	10 (0.03%)	0	<0.001	<0.001
Peripheral nerve injury	1 (0.0%)	1 (0.0%)	1 (0.0%)	NA	NA
Venous obstruction	25 (0.03%)	28 (0.09%)	8 (0.02%)	0.057	<0.001

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