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.