Discussion:
In this investigation of in-hospital SCA patients stratified on the basis of ESRD status or not, we report several key findings. (1) The mortality in patients with in-hospital SCA were similar in PS matched analysis regardless of ESRD status (70.4% vs. 70.7%, p = 0.45). (2) Over the study period from 2007-2017, there was a reduced trend of mortality after a SCA event in both ESRD and non-ESRD patients after an initial spike in the year 2009. (3) ESRD patients who suffered in-hospital SCA were younger and had a higher burden of key co-morbidities when compared to non-ESRD patients with in-hospital SCA. (4) The utilization of invasive procedures was lower in ESRD patients compared to non-ESRD patients after an in-hospital SCA.
In-hospital SCA affects nearly 290,000 adult patients in US each year (12). The clinical trajectory of ESRD patients is frequently complicated by SCA which contributes to nearly a quarter of deaths in this patient population (1). ESRD patients have an underlying vulnerable myocardial substrate for SCA since most of these patients are found to have LVH that can prolong ventricular repolarization, a well-recognized risk factor for induction of malignant arrhythmias (3,4). Additionally, electrolyte fluctuations during dialysis sessions are responsible for triggering a SCA event (5,6). Few earlier studies have reported outcomes of ESRD patients after they sustained in-hospital SCA. In a previous study on outcomes in ESRD patients after in-hospital SCA, Saeed et al. have shown higher adjusted mortality in ESRD patients when compared to non-ESRD group (adjusted OR 1.24, 95% CI 1.11-1.3) (13). While assessing mortality trends over their study period from years 2005-2011, they found improved survival in the year 2011 compared to year 2005 (31% vs. 21%, p < 0.001). In a more recent study from Get with the Guidelines Registry, Starke et al. evaluated 31,144 patients who suffered in-hospital SCA and stratified outcomes based on dialysis status (14). After multivariate adjustment, they found similar odds of survival to discharge (adjusted OR 1.05, 95% CI 0.97-1.13) and survival with a favorable neurologic status (adjusted OR 1.12, 95% CI 1.04-1.22) in ESRD patients when compared to their non-ESRD counterparts. In our study, we also demonstrated similar mortality rates in ESRD and non-ESRD patients after in-hospital SCA in PS matched cohorts. Additionally, in our trend analysis, we have also shown improved mortality in both ESRD and non-ESRD patients after in-hospital SCA over our study years despite an initial spike in year 2009 (figure 3). American Heart Association (AHA)/Emergency Cardiovascular Care (ECC) CPR guidelines were updated in 2010 and focused primarily on early chest compressions (chest compression-airway-breathing rather than airway-breathing-chest compressions as recommended by earlier guidelines), chest compressions of at least 2 inches with a rate of at least 100/minute, eradication of atropine use for non-shockable SCA and prompt institution of targeted temperature management in eligible patients (15,16). It is plausible that improved mortality trend witnessed in our study in both ESRD and non-ESRD patients especially after 2010 may be related to wider application of revised AHA/ECC guidelines across all patient sub-groups.
Our analysis showed mortality was in excess of 70% in ESRD patients who suffered in-hospital SCA. The first step in reducing this mortality in ESRD patients is to adequately identify risk factors that are associated with in-hospital SCA so that targeted risk modification can be done. Shastri et al. assessed 1745 dialysis patients from the noncardiac deaths in the hemodialysis (HEMO) study and found that prior history of diabetes, peripheral vascular disease and ischemic heart disease were independently associated with SCA events in dialysis patients (17). After incorporating these variables in a SCA prediction model, they found good discrimination (C-statistic of 0.75, 95% CI 0.70-0.79) and calibration of the model at 3 years of follow-up. Our study also showed increased prevalence of diabetes (32.5% vs. 8.4%, p < 0.01), peripheral vascular disease (19.9% vs. 9.9%, p < 0.01) and coronary artery disease (39.4% vs. 30.8%, p < 0.01) in ESRD patients who sustained in-hospital SCA when compared to non-ESRD patients. Additionally, in our predictor analysis, both diabetes (OR 1.046, 95% CI 1.009-1.084) and peripheral vascular disease (OR 1.079, 95% CI 1.044-1.115) were associated with increased mortality after in-hospital SCA among ESRD patients.
The current data on therapeutic interventions that can prevent SCA or improve outcomes after a SCA event in ESRD patients are limited. In a randomized, placebo-controlled trial on 114 consecutive dialysis patients with history of dilated cardiomyopathy, carvedilol administration was associated with 24% reduction in mortality at two years and a trend towards reduced incidence of SCA (18). On the contrary, a secondary analysis of HEMO study did not show any benefit of beta-blocker utilization in reducing incidence of SCA (19). The utilization of calcium channel blockers of dihydropyridine class is associated with improved survival at 24 hours after an index SCA event (20). Implantable cardioverter defibrillators have been shown to improve outcomes when utilized for secondary prevention purposes, however, they are often underutilized in ESRD patients due to multitude of factors (21). Additionally, dialysis prescription offers several opportunities to reduce risk of SCA among ESRD patients. Large fluctuations in serum electrolytes and fluids have been demonstrated as inciting factors for initiation of SCA in ESRD patients. Low potassium and calcium dialysates are especially associated with increased SCA as they increase the risk of hypokalemia and hypocalcemia during a dialysis session that disperses myocardial repolarization which is a well-recognized prerequisite for initiation of malignant arrhythmias (5,22,23). Our data, unfortunately, do not inform on these patient and dialysis related characteristics. However, prompt attention to these measures can result in prevention of SCA events in ESRD patients and result in improved outcomes after such events have occurred.