Table 1.

Participant Characteristics and Frailty-Outcome Results From Included Studies

Author (year)	Study type	Study question	Population	Frailty definition	Mortality definition	Sample size	Age	Follow-up time	Frailty findings
Piotrowicz et al. (2007)	RCT	Association of physical functioning and mental well-being with ICD outcomes	Multicenter ICD Trial II USA	Low physical component summary (PCS) score on SF-12	All-cause mortality	638	Mean 64 years	12 months	Patients with a baseline PCS score below 35 had a mortality rate twice as high as patients with a score above 35 (HR 1.89, 95% CI 1.34–2.65, p < 0.001)
Schernthaner et al. (2007)	Retrospective cohort	Risk factors related to mortality in patients with ICD	Single institution: Paracelsus Private Medical University, Salzburg, Austria	“Low BMI”	All-cause mortality	77	Median 67 years	4 years Mean 24.5 months	Non-survivors had significantly lower BMI (23.5 ± 3.5) vs survivors (26.9 ± 4.3) (p = 0.015). Those with BMI less than the median (26.1 kg/m2) were more likely to die during follow-up (log rank p = 0.024)
Zhan et al. (2007)	Retrospective cohort	Incidence of peri-operative outcomes following cardiac device implantation	Registry: Healthcare Cost and Utilization Project (HCUP) Nationwide Inpatient Samples (NIS) USA	“Advanced age,” ≥ 3 comorbid conditions	Peri-operative, in-hospital mortality	13,577	58% were > 65 years, 3% were > 85 years	1997–2004	Rates of in-hospital mortality were higher in those at advanced age (75–84, OR 1.18, p < 0.01) and who had ≥ 3 comorbid conditions (OR 2.97, p < 0.01). Results were not significant in those > 85 years (OR 0.85, CI not reported)
Hsu et al. (2012)	Retrospective cohort	Association between BMI and outcomes following ICD implantation	Registry: National Cardiovascular Data Registry (NCDR) USA	Underweight BMI category (≤ 18.5 kg/m2)	Peri-operative, in-hospital mortality	83,312 (1.7% underweight) n = 1434	Mean age by BMI category: 65 (underweight); 66 (normal weight); 61 (obese)	April 2010–June 2011	Compared to normal weight ICD recipients, those who were underweight had a greater odds of in-hospital death (adjusted OR 2.27, 95% CI 1.21–4.27, p = 0.011)
Fishbein et al. (2014)	RCT	ICD vs standard medical therapy	Pre-specified subgroup of SCD-HEFT USA	6-min walk test	All-cause mortality	2397	Median age reported according to tertiles of walking speed: 64 (lowest), 59 (mid), 57 (fastest)	45.5 months (median)	Compared to those who received medical therapy only, those who received an ICD and were in the top (HR: 0.42, 95% CI 0.26–0.66, p = 0.0002) and middle (HR 0.57, 95% CI 0.39–0.83, p = 0.0035) tertiles of walking speed had a lower risk of mortality. In the lowest tertile of walking speed the benefit was null (HR 1.02, 95%CI 0.75–1.39, p = 0.90)
Kramer et al. (2015)	Retrospective cohort	Association between physical activity and survival following ICD USA	Boston Scientific LATITUDE remote monitoring system USA	Mean daily activity captured by the accelerometer in the ICD, reported in quintiles	All-cause mortality	98,437	Mean age 68, mean age 74.6 in the lowest	2.2 years (median)	Lower baseline activity was independently associated with an increased risk of death (adjusted HR 1.44, 95% CI 1.427–1.462)
Green et al. (2016)	Retrospective cohort	Association between frailty and dementia on 1 year mortality following ICD USA	Registry: NCDR and Medicare USA	Variation of the cumulative deficit method: Johns Hopkins coding algorithm incorporating 99 ICD-9 codes indicating 10 geriatric diagnostic clusters	All-cause mortality	83,972	Mean age 75	1 year	Individuals with frailty had a higher mortality rate compared to the overall cohort (22% vs 12%) Patients with frailty alone had an increased odds of mortality (adjusted OR 4.00 [95% CI not reported]) while those with frailty and dementia had the highest odds of death (adjusted OR 8.68, 95% CI 7.33–10.27) compared to those with no comorbidity
Gostoli et al. (2016)	Prospective cohort	Association between allostatic overload and ICD mortality	Department of Cardiology, University of Bologna, Bologna, Italy	Allostatic overload: poor baseline psychological and psychosomatic profile	All-cause mortality	117	Mean age 63.1	Up to 24 months	Patients with severe allostatic overload are less likely to survive (HR 0.18, 95% CI 0.06–0.51, p < 0.001)
Jahangir et al. (2017)	Retrospective cohort	Association between BMI and outcomes following ICD implantation	Aurora Health Care system in Milwaukee, Wisconsin USA	Low BMI	All-cause mortality	904	Mean age 67	Mean 2.6 years	Obese (10.1%, OR 0.35, 95% CI 0.21–0.58) and overweight (7.9%, OR 0.25, 95% CI 0.13–0.40) groups had lower mortality than the normal group (22.9%, p < 0.001)

ICD implantable cardioverter defibrillator, BMI body mass index, OR odds ratio, CI confidence interval, RCT randomized controlled trial, SCD-HEFT Sudden Cardiac Death in Heart Failure Trial, HR hazard ratio