Complete revascularisation is rarely achieved in patients with multivessel coronary artery disease (CAD) and cardiogenic shock related to acute myocardial infarction (MI). This is the conclusion of a study evaluating the predictive value of the residual SYNTAX score in patients with cardiogenic shock. Findings from the study were published in the Journal of the American College of Cardiology (JACC) in January, with the authors concluding that the residual SYNTAX score is independently associated with early and late mortality.
The findings were gained through a sub-analysis of the CULPRIT-SHOCK—Culprit lesion only percutaneous coronary intervention (PCI) versus multivessel PCI in cardiogenic shock—trial. The analysis was designed to assess the extent, severity, and prognostic value of remaining coronary stenosis following PCI, by using the residual SYNTAX score in patients with cardiogenic shock related to myocardial infarction, as well as evaluating the impact of the residual SYNTAX score on early and late prognosis.
CULPRIT-SHOCK compared a multivessel PCI (MV-PCI) strategy with a culprit-lesion only PCI (CLO-PCI) strategy in patients with multivessel CAD who presented with MI-related cardiogenic shock. In their analysis of the trial results, Olivier Barthélémy (Cardiology Institute, University of the Sorbonne, Paris, France) and colleagues note that the findings demonstrate that a CLO-PCI strategy with possible staged revascularisation significantly reduced the rates of 30-day death or renal replacement therapy and 30-day mortality compared with an immediate MV-PCI strategy in patients with multivessel CAD and myocardial infarction-related cardiogenic shock.
These results led to current European Society of Cardiology (ESC) guidelines on myocardial revascularisation, which no longer recommend routine non-infarct-related-artery PCI during primary PCI in this situation. This is in contrast to that for haemodynamically-stable patients with MI, in whom immediate or early complete revascularisation following PCI or coronary artery bypass grafting has been shown to be associated with better cardiovascular outcomes, Barthélémy and colleagues write.
In the present study, Barthélémy and colleagues carried out an analysis of coronary angiograms taken from CULPRIT-SHOCK trial, which was conducted from April 2013 through April 2017 at 83 European centres and involved 706 patients. Experienced angiography readers assessed the SYNTAX score visually, and were blinded to the clinical and procedural data. Each lesion that qualified as ≥50% diameter stenosis in a vessel ≥1.5mm was scored using the online SYNTAX score tool. Two readers, each blinded to the other, assessed the baseline and residual SYNTAX scores, and entered the data in a dedicated computerised database.
The baseline SYNTAX score assessment was prespecified and calculated prospectively, while the residual SYNTAX score was calculated on the last frames of the initial PCI angiogram or of the planned PCI angiogram in the CLO-PCI group, if a staged revascularisation of non-culprit lesions was performed during the index hospitalisation.
Outcomes of interest included the 30-day rate of death or renal replacement therapy—the primary endpoint of the CULPRIT-SHOCK trial—as well as 30-day mortality, and one-year mortality rates. The 30-day secondary outcomes of the CULPRIT-SHOCK trial were also reported.
Outlining the results, Barthélémy and colleagues write that, among the 706 patients randomised in the CULPRIT-SHOCK trial, 587 (85.6%) were included in the sub-study. Among these patients, the median baseline SYNTAX score before PCI was 24.5 (interquartile range [IQR]: 17‒32). The study team notes that immediate MV-PCI was performed in 298 patients (50.8%), while among the 289 patients (49.2%) randomised in the CLO-PCI arm of the study, 48 (16.6%) underwent staged PCI within nine days (IQR: four to 18) days after randomisation. In the total study group, the median residual SYNTAX score was 9 (IQR: three to 17) and complete revascularisation was achieved in 102 patients (17.4%). The authors further note that there was a stepwise increase in outcome rates according to increased residual SYNTAX score in the whole study group, as within each randomisation group separately.
Discussing the findings, Barthélémy and colleagues report that the study, the first in a large sample size to evaluate the prognostic value of residual SYNTAX score in cardiogenic shock related to acute MI, found that, despite using an MV-PCI strategy, complete revascularisation is “only” achieved in one-fourth of the patients. Further to this, they note that the residual SYNTAX score is associated with early and late mortality, independently of all clinical characteristics and baseline SYNTAX score.
The authors write: “There is an apparent discrepancy between a high residual SYNTAX score as an independent predictor of cardiovascular outcomes, as shown in our study, and the results of the CULPRIT-SHOCK trial demonstrating a benefit of CLO-PCI in comparison with the MV-PCI strategy. We can speculate about these discrepancies in patients in cardiogenic shock, which may relate to: 1) a more severe CAD pattern at baseline; 2) a less achievable complete revascularisation following PCI; and 3) a higher risk of harmful complementary PCI.”
Further, they note that primary PCI led to a worsening of coronary anatomy in 1‒3% of the patients whose residual SYNTAX score was higher than the baseline SYNTAX score in the CLO-PCI and MV-PCI groups, respectively: a condition that has never been described in haemodynamically-stable patients.
“This finding may be explained by taking into account—for residual SYNTAX score but not baseline SYNTAX score assessment—the hidden stenoses downstream of the culprit coronary total occlusion after they have been revealed following successful PCI. However, management of the non-culprit lesion appears to be a key determinant of prognosis. In the acute setting, there is an obvious risk to overestimate the severity of the non-culprit lesion and thus perform PCI in non-flow limiting stenosis that may even cause harm,” they add.
More complete revascularisation and safer revascularisation may be the goals of future clinical research in this area, they note, adding that mechanical circulatory support devices may provide an answer to this. “Whether these devices should be used in the acute setting for myocardial salvage, in non-acute staged revascularisation, or both, to achieve more complete revascularisation remains a matter of debate,” the study’s authors suggest.
Detailing potential limitations of the study, the authors write that in cardiogenic shock, multivessel CAD is generally observed in three quarters of patients. However, in the CULPRIT-SHOCK trial, they note, cardiogenic shock was part of the inclusion criteria, and led to inclusion of a study group at higher risk by excluding patients with single-vessel CAD. In addition to this some values are missing, including left ventricular ejection fraction, which was available in only half of the patients. Furthermore, they add, the study is outside the scope of functional assessment of non-culprit lesion stenosis using fractional flow reserve, also noting that some potentially unmeasured confounders may remain.
In an analysis of the findings, published alongside the study in JACC, Ajar Kochar (Brigham and Women’s Hospital, Boston, USA) and colleagues note that the sub-study’s conclusions appear to contrast with the overall results of the CULPRIT-SHOCK trial, “in which upfront MV-PCI led to worse outcomes compared with CLO-PCI”. They add: “Alternatively, this analysis reveals that patients with lower residual SYNTAX score are at a lower risk for death events, suggesting that additional interventions to reduce residual SYNTAX score in acute myocardial infarction-related cardiogenic shock (AMI-CS) may plausibly improve survival. Importantly, these findings were derived from a secondary analysis and therefore should be viewed as hypothesis-generating.”
They go on to conclude: “This study by Barthélémy et al is the first large study investigating residual CAD after revascularisation for AMI-CS. The key findings of this study reveal that rates of CR after AMI-CS are low and that higher residual SYNTAX score is associated with increased short- and long-term all-cause mortality. More studies are needed to investigate whether further reduction in residual CAD could lead to improved outcomes for patients with AMI-CS using various revascularisation strategies.”