Risk-adjusted, in-hospital mortality has declined in recent years among patients with cardiogenic shock after acute myocardial infarction (CS-AMI) when taking into account an increase in the number of extreme-risk patients undergoing percutaneous coronary intervention (PCI), according to the results of a retrospective study presented Tuesday at Scientific Sessions.
“Presentation after cardiac arrest is an extreme risk marker in patients with CS-AMI and some mechanism to account for this group is essential to accurately assess mortality trends in this population,” said Udhay Krishnan, MD, of the Division of Cardiology at Weill Cornell Medical College, New York Presbyterian Hospital-Cornell Medical Center in New York. “These results help reconcile the discordance between studies which showed a decline in mortality for the entire CS-AMI population and studies which showed a null effect on mortality for the PCI-only population.”
According to Krishnan, many observational studies have reported a decline in mortality in patients with CS-AMI, a trend attributed to the increasing use of early revascularization. However, other contemporary studies that have focused specifically on patients with cardiogenic shock treated with early PCI have found no improvement in mortality over time.
Krishnan and colleagues hypothesized that sicker patients with CS-AMI with more comorbidities and high clinical acuity were now presenting to the catheterization lab when compared with earlier years, and that certain extreme risk traits may not be properly adjusted for using current mortality models.
With this study, the researchers looked at 59,118 patients with CS-AMI who underwent PCI within 24 hours of hospitalization taken from the 2005-2012 Nationwide Inpatient Sample database. In an unadjusted analysis, there was no change in in-hospital mortality between 2005-2006 and 2011-2012 (30 percent versus 27.8 percent, respectively). There was an increase in the proportion of patients with three or more Elixhauser comorbidities (28.5 percent versus 51.5 percent, respectively) and comorbidity scores of 5 or greater (37.2 percent versus 48.2 percent, respectively).
To better characterize what they considered “extreme risk” patients, such as those with higher clinical acuity on admission, the researchers examined a subgroup of patients whose presentation within the first 24 hours was complicated by cardiac arrest or the need for mechanical ventilation. They found that the population of patients that suffered from cardiac arrest or needed intubation on the first hospital day increased from 27.8 percent in 2005-2006 to 42.6 percent in 2011-2012. In a multivariable analysis that adjusted for these factors as well as clinical comorbidities, mortality rates in 2011-2012 had decreased significantly compared with 2005-2006 (OR=0.75; 95 percent CI, 0.65-0.85; p<.001). “Likely, as a result of broadened use of PCI, growing STEMI systems of care, improved pre-hospital survival and evolving practice guidelines that promote early revascularization, more patients with severe CS complicated by cardiac arrest are being selected for early PCI when compared to previous years,” Krishnan said. “This ‘migration’ of extreme-risk patients into the cath lab over the years likely neutralizes much of the mortality benefit attributable to advances in contemporary invasive management when we restrict our viewpoint to a PCI-only sample.”