Herein we report the outcomes of CS in a patient population limited exclusively to ADHF in 2 tertiary care centers capable of providing heart replacement therapy. The main finding of this study is that a simple risk score which includes age, serum creatinine and arterial lactates may adequately predict 28-day survival in ADHF-CS patients. In this specific population, this score performed better than a previously validated stratification tool which was derived from a heterogenous population of cardiogenic shock patients.13
Clinical decision-making is challenging in CS patients due to the complexity of the metabolic, hemodynamic and inflammatory pathways which occur once a low output state develops3. Moreover, the epidemiologic changes that occurred in the last decades further require attention6 : data from the collaborative research network of American Heart Association showed a shift from AMI-CS to CS occurring as a consequence of ADHF.3 These two scenarios differ from a pathophysiological and hemodynamic standpoint,28 and this may explain why treatments that are ineffective in the setting of AMI (e.g. IABP) might be beneficial in patients with CS-ADHF.7–24,28
In particular, a favorable profile may emerge from IABP, since the risks of the procedure are low, the limited increase of cardiac output that it provides may be sufficient for improving tissue perfusion in patients with chronic advanced HF, in whom some adaptation to reduced cardiac output exists, and these effects are not blurred or confounded by the effect of an etiology-directed treatment such as reperfusion in CS associated with acute MI.
In an examination of multiple prognostication tools recently published in CS patients, three variables were consistently included10,13,25,27,29 (age, renal function, and lactates,). Ageing and renal failure are associated with worst outcomes in several cardiac and non-cardiac disease states. 30,31,32 Although these characteristics may contribute to contraindications for HT/LVAD, they could be regarded as hallmarks for early decision in favor of surgery (mainly LVAD) as long-term therapy, before deterioration that would reduce the probability of survival, either with or without heart replacement therapy. Elevated arterial lactate is an early marker of the metabolic dysregulation and microcirculatory dysfunction that leads to multiorgan failure.3 Therefore, in patients with acutely decompensated chronic heart failure, these three variables reflect constitutive and contingent factors strongly related to prognosis.
It is important to note that the performance of our score was somewhat reduced when applied to an external validation cohort. However, the derivation and validation population differed in age and risk profile. Furthermore, every patient in the validation cohort was treated with IABP, suggesting a potential impact of this therapy on outcomes. Importantly, when we compared the actual and predicted rates of mortality, the ALC-shock score was well-calibrated for all patients at low and intermediate risk including those in the external validation cohort. The overestimation of mortality rates in the high-risk group could be explained by the early timing of IABP therapy in this latter cohort.
Recent data have focused on the prognostic role of hemodynamic indexes [cardiac power output/index (CPO/CPI) and pulmonary artery pulsatility index (PAPi)] in patients with ADHF-CS.25,28 However, the insertion of a pulmonary artery catheter, though often performed in some centers, is not routinely pursued, involves some risks to the patient, and data are not readily available upon admission. Moreover, patients with chronic AHF may adapt to highly abnormal hemodynamic profile with normal or near normal end-organ function, lactate and minimal symptoms - thus models based on purely hemodynamic parameters may be limited in both prognostic ability and broad application. Indeed, the major strength of this data is the description of a simple and reliable prediction model for ADHF-CS patients, who represent a growing percentage of the overall cohort of CS patients. This tool can be used at bedside upon admission to the ICU to prognosticate and plan the next management strategies in order to identify the right patient to get access to durable surgical solutions such as HT or LVAD.
Our study has several limitations. First, we did not compare our score to others that included hemodynamic data.25 However, as previously discussed, hemodynamic assessment with pulmonary artery catheters is not routinely performed, limiting the widespread applicability of such scores. Second, as noted above, the model had diminished performance in the validation cohort, particularly among the highest risk profile. Third, it is important to note that intermediate and long-term survival often depends on the patient’s candidacy for heart replacement therapies and the criteria for such therapies often differ somewhat between different centers such as the two contributing cohorts for the analysis.