In this series of patients who sustained out-of-hospital cardiac arrest, acute catheterization (defined as the procedure performed within the first 6 hours) was associated with improved survival in bivariate and multivariate analyses compared to the group receiving no catheterization or after 6 hours. Additionally, using propensity scoring to identify patients with a higher likelihood of receiving acute catheterization identified a sub-population of patients in which acute catheterization was greatly associated with improved survival. Most survivors in both groups were neurologically intact upon hospital discharge. Despite this report, the rSCA patient population still presents a difficult clinical dilemma. Namely, should cardiac catheterization be regularly performed, and if so, within what time frame?
It was previously shown in an angiographic study of patients with rSCA that 94% of these patients had at least 1 epicardial coronary artery with > 70% reduction in vessel diameter. 2
Autopsy studies have also shown a large ischemic burden in this population. Farb et. al. demonstrated that 57% of patients who succumbed to SCA had active coronary lesions (as defined by the presence of platelet and fibrin thrombi) at autopsy. This finding was present even in the absence of acute myocardial infarction. Furthermore, many patients without active coronary lesions or myocardial infarction still had epicardial coronary stenosis in excess of 70% diameter reduction. 3
Given that the majority of rSCA is secondary to coronary artery disease, and that a significant number of these patients have active coronary lesions, we hypothesized and demonstrated that early catheterization and coronary intervention were associated with decreased mortality in this patient population. It has been well demonstrated that delay to coronary revascularization, whether pharmacologic4
or via PCI5
is associated with decreased survival. Despite these facts, there has been limited published research into the use of early catheterization in patients with rSCA. The majority of research has focused on patients with ST-segment elevation on the ECG after resuscitation.
The “acute catheterization” strategy was first shown to be feasible in patients with rSCA in 1995.6
Despite this, subsequent studies, all in patients with ST-segment elevation on post-resuscitation ECGs have reported mixed success. Bendz et al. concluded that although PCI in this population was feasible and safe, it was associated with an increased
mortality as compared with matched patients with ST-segment elevation myocardial infarction.7
Furthermore, in a multivariate retrospective analysis of 186 patients with rSCA, PCI was not a predictor of 6-month survival.8
These studies were limited by small sample sizes. Our findings are in contrast to these and suggest a beneficial influence of early PCI.
What is the value, then, of ST-segment elevation in predicting those patients who would benefit from acute reperfusion in the rSCA setting? The presence of ST-segment elevation was a strong predictor of acute coronary occlusion in a series of 186 consecutive cases of rSCA, with an odds ratio of 4.5 for acute coronary occlusion (p=0.004)9
. Presumably, these patients would be likely to benefit from acute catheterization and PCI. In a recent retrospective study from Paris10
, the predictive value of ST elevation for coronary occlusion in the setting of rSCA was poor, suggesting that immediate catheterization regardless of the presence or absence of ST elevation was warranted.
If the ECG is suboptimal to detect those patients with acute coronary occlusion, what other diagnostics are available to the clinician faced with the rSCA patient? Gorjup et al correlated presenting neurologic status with outcomes of rSCA in 135 consecutive patients. While a poor presenting neurologic status predicted a poor final neurologic status, approximately 25% of initially comatose patients recovered with either no or minimal neurologic deficits.11
This would argue that using neurologic status upon presentation as a determinant of which patients receive acute catheterization is not well founded.
The correlation of presenting cardiac biomarkers with acute coronary occlusion in patients with SCA is not well established. One small postmortem analysis showed that patients with cardiac death had statistically higher CK-MB than patients with non-cardiac deaths. There was also a trend toward higher troponin I in these patients, but this did not reach statistical significance.12
Given the relatively high frequency of acute coronary occlusions, inherent flaws in relying on the ECG for diagnosis in the rSCA patient, and imperfections in the other clinical tools usually used for diagnosis of myocardial infarction, perhaps all patients with rSCA should receive acute catheterization. Keelen et al published a long-term survival rate of greater than 60% in a series of 15 patients with rSCA and early coronary angioplasty within 8 hours. 80% of these patients had ST-segment elevation.13
Spaulding et al published the largest series of rSCA patients to date. Of 186 consecutive cases of rSCA, only 43% had ST-segment elevation on their post-resuscitation ECG. In this population of all-comers, successful PCI was markedly associated with survival with an odds ratio of 5.2 (p=0.03). 9
Our findings suggesting improved survival with acute catheterization lend credence to the idea that all patients resuscitated from out-of-hospital ventricular fibrillation should receive early catheterization and revascularization if indicated. Our study is in agreement with a recent study, which also used a propensity-adjusted analysis that demonstrated a beneficial effect of acute catheterization following rSCA.14
The authors also pointed out that there is a bias for taking patients with better neurologic status (normal eye, verbal, and Glasgow Coma Scores) acutely for cardiac catheterization. The risk of diagnostic catheterization and coronary angiography can be considered low in these patients, and even a negative coronary angiogram would provide useful diagnostic information.
This study has several limitations. First, it is retrospective and based upon chart review. Second, selection bias is inherent in a physician’s decision to perform cardiac catheterization. We have attempted to minimize such biases through the use of statistical adjustment, although we recognize biases cannot be completely eliminated with these methods. The only way to truly eliminate these biases would be to perform a randomized controlled trial of acute catheterization and PCI in this population.