The present study evaluates the prognostic impact of CKD in consecutive high-risk patients presenting with ES on admission. This data suggests that ES patients reveal a higher long-term mortality at 3 years in the presence of CKD. Respectively, increasing rates of the secondary endpoint MACE were seen in CKD patients. In contrast in-hospital mortality rates, risk of first cardiac rehospitalization, and ES-R were not affected by CKD. Prognostic differences were demonstrated even within the multivariable Cox regression model, where both CKD and LVEF < 35% were still associated with long-term mortality at 3 years. This study identifies the presence of CKD as a robust predictor of adverse prognosis in ES patients.
CKD is an independent predictor of cardiovascular morbidity and mortality [17, 18]. The most common cause of death in hemodialysis patients is sudden cardiac death (SCD) [10]. Although dialysis patients show the highest risk of cardiovascular events, even mild CKD stages are associated with ventricular tachyarrhythmias and SCD [18].
Potential risk factors and the resulting preventive therapeutic options of patients with ventricular tachyarrhythmias have been discussed continuously within the past years [12, 19]. According to international guideline recommendations, the implantation of an ICD is strongly recommended in patients with systolic heart failure defined as LVEF < 35% irrespective of the underlying cardiac disease [20]. However, especially in the presence of ischemic cardiomyopathy, as defined by a history of relevant CAD or prior myocardial infarction, ICD implantation was shown to be associated with reduced all-cause mortality [19]. Although ICD implantation is recommended for patients with systolic heart failure and non-ischemic (dilatative) cardiomyopathy (DCM) [20], the DANISH trial recently reported that primary preventive ICD implantation in patients with non-ischemic cardiomyopathy was not associated with improved long-term prognosis (i.e., death from any cause and cardiovascular death). However, the risk of sudden cardiac death was significantly reduced in the ICD group [12]. We recently demonstrated that neither the presence of ischemic cardiomyopathy compared to non-ischemic cardiomyopathy revealed any differences in prognostic outcomes in ICD recipients presenting with ventricular tachyarrhythmias at index. However, patients with non-ischemic cardiomyopathy showed higher rates of recurrent ventricular tachyarrhythmias at 1 year [21].
Focusing on the prognostic impact of CKD in patients with ventricular tachyarrhythmias—representing a not well-studied risk factor in this subset of patients—it was demonstrated that CKD patients were significantly associated with increased long-term mortality at 2 years, cardiac death, and in-hospital death, which is also reflected within the corresponding RACE-IT CKD risk score [22]. Even in ICD recipients, only CKD was still associated with increased long-term mortality, recurrent ventricular tachyarrhythmias, and appropriate device therapies at 5 years [23].
In clear contrast, data in ES patients with CKD is rare. Potential risk factors for ES are widely discussed, and the specific causative pathology for the development of ES is not yet fully understood, not even in higher-risk patients with relevant comorbidities, such as CKD and heart failure [3, 5]. As demonstrated by the present analysis, the presence of both CKD and LVEF < 35% was shown to be significantly associated with increased all-cause mortality. Both comorbidities may reflect the presence of the cardiorenal syndrome, which is defined as “disorders of the heart and kidneys, whereby acute or chronic dysfunction in one organ may induce acute or chronic dysfunction of the other” [8, 24]. The cardiorenal syndrome is categorized into 5 subtypes based on the organ presumed to be the primary trigger [8, 24]. Although this definition is of clinical importance, it reveals less information about the underlying pathophysiological pathways. Interstitial fibrosis in the heart, vessel wall structure, and kidney has been identified as responsible pathogenetic factors in most types of the cardiorenal syndrome [25]. In the present analysis, CKD patients with ES were older and had a numerically increased cardiovascular risk profile. Aging and risk factors, such as arterial hypertension, dyslipidemia, and diabetes mellitus, may lead to sympathetic neurohumoral activation, chronic inflammation, and oxidative stress related to endothelial dysfunction. In turn, these conditions may alleviate, leading to heart and kidney failure due to the increasing amount of interstitial fibrosis and activation of the renin–angiotensin–aldosterone system (RAAS). Myocardial fibrosis attenuates cardiomyocyte coupling and thereby may enhance arrhythmogenicity [10]. Therefore, interstitial fibrosis may reflect the main causative pathology in cardiorenal syndrome [24, 25].
Furthermore, other explanations for the increased cardiovascular mortality in CKD patients do exist [10]. Myocardial ischemia related to coronary artery disease represents major comorbidity in CKD patients [10]. It has recently been demonstrated that ventricular tachyarrhythmias and SCD after myocardial infarction are more common in the presence of CKD [26]. In the present study, patients with CKD showed significantly higher rates of ischemic cardiomyopathy, which might further confirm these findings and explain the increased long-term mortality and higher rates of MACE in the present study evaluating patients with ES.
The present study demonstrated that CKD patients presenting with ES were associated with increased rates of long-term mortality and MACE compared to non-CKD patients. This negative prognostic impact of CKD in ES patients may be related to the cardiorenal syndrome due to myocardial and renal fibrosis, increased cardiovascular risk profile, and ischemic cardiomyopathy, which may explain the adverse prognostic impact of CKD in ES patients. However, further–at best-randomized controlled trials are needed to investigate the prognostic impact, its pathophysiological pathways, and potential therapeutic options in high-risk ES patients with CKD. The supposed benefit of excluding CKD patients from RCT, especially in high-risk patients with ES, needs to be further debated [1, 8].