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CHAPTER 12
PCI Strategies in Acute Coronary Syndromes without ST Segment Elevation (NSTE‐ACS)
Anastasios Roumeliotis and Emmanouil S. Brilakis
Acute coronary syndromes (ACS) include both ST elevation myocardial infarction (STEMI) and non‐ST‐ elevation ACS (NSTE‐ACS). NSTE‐ACS are is subdivided in non‐ST‐elevation myocardial infarction (NSTEMI) and unstable angina (UA). Pathophysiologically, STEMI correlates with vessel occlusion, NSTEMI with critical vessel stenosis and UA with vulnerable atheromatous plaque, partially obstructing the coronary lumen [1]. While emergent myocardial revascularization has been well established in STEMI, it is not needed in NSTE‐ACS except for unstable patients. This chapter reviews risk stratification, emergency department (ED) diagnosis, revascularization strategies and adjunctive pharmacologic therapies for patients presenting with NSTE‐ACS.
Emergency department diagnosis and risk stratification
According to the most recent European Society of Cardiology (ESC) guidelines on the management of NSTE‐ACS, chest pain evaluation in the ED should be primarily based on the characteristics of the pain, electrocardiographic findings, and myocardial enzyme measurements [2]. Recently, the Rapid Assessment of Possible ACS In the Emergency Department With High Sensitivity Troponin T (RAPID‐TnT) study demonstrated that high‐sensitivity cardiac troponin T (hs‐TNT) can expedite the discharge of patients with suspected ACS [3]. In the High‐Sensitivity Cardiac Troponin on Presentation to Rule Out Myocardial Infarction (HISTORIC) trial use of high sensitivity troponin was associated with shorter length of stay at the ED and fewer hospital admissions, without compromising subsequent clinical outcomes [4]. Among 15 international cohorts of patients, high‐sensitivity troponin I concentrations of less than 6 ng per liter and an absolute change of less than 4 ng per liter after 45 to 120 minutes (early serial sampling) resulted in a negative predictive value of 99.5% for myocardial infarction, with an associated 30‐day risk of subsequent myocardial infarction or death of 0.2%; 56.5% of the patients were classified as low risk [5]. The advantages and disadvantages of widely adopting high‐sensitivity cardiac troponin are depicted in Figure 12.1.
Figure 12.1 Advantages and disadvantages or high sensitivity cardiac troponin.
AMI, acute myocardial infarction; CKD, chronic kidney disease; ED, emergency department.
Once the diagnosis of NSTE‐ACS has been established, risk stratification should guide management strategy (early invasive vs ischemia‐driven) and timing (urgent, early, or delayed). Several risk scores are available to assess patient risk, such as the Global Registry of Acute Coronary Events (GRACE) score and the Thrombolysis in Myocardial Infarction (TIMI) score. The GRACE score is calculated using eight readily identifiable variables and help estimate the cumulative six month risk of death or myocardial infarction [5], while the TIMI score utilizes seven predictor variables and estimates all‐cause mortality, recurrent MI, or severe recurrent ischemia requiring urgent revascularization through the first 14 days [6] (Table 12.1). In general, high risk patients are more likely to suffer from complications, such as prolonged myocardial ischemia and extensive subsequent myocardial injury, decreased left ventricular ejection fraction and life‐threatening arrhythmias (ventricular tachycardia or fibrillation). Such patients may derive maximum benefit from an early invasive approach.
Table 12.1 The GRACE and TIMI scores for assessing the prognosis of patients presenting with NSTE‐ACS.
| GRACE score | TIMI score | ||
|---|---|---|---|
| Variables | Prognosis(6‐month death/MI) | Variables | Prognosis(14‐day MACE*) |
| AgeHeart rateSystolic BPCreatinineCHFCardiac arrest on admissionST‐segment deviationElevated cardiac enzymes | 0‐85 → 0‐2%86‐153 → 3‐10%154‐190 → 11‐20%191‐204 → 21‐25%205‐235 → 26‐30%236‐255 → 40%>255 → 50% | Age ≥653 or more CAD risk factors**Preexisting CAD (≥50% stenosis)Aspirin use in the past 7 daysSevere angina (≥2 episodes in 24 hours)EKG ST changes ≥0.5mmPositive cardiac biomarkers | 10/1 → 4.7%1121→ 8.3%1113 → 13.2%1114 → 19.9%1115 → 26.2%16/7 → 40.9% |
BP, blood pressure; CHF, congestive heart failure; CAD, coronary artery disease; EKG, electrocardiogram; MI, myocardial infarction; MACE, major adverse cardiac events. * MACE is a composite of all‐cause mortality, recurrent MI, or severe recurrent ischemia requiring urgent revascularization. ** Hypertension, hypercholesterolemia, diabetes, family history of CAD, or current smoker.
Early invasive versus ischemia‐guided strategy
When evaluating patients with definite or likely NSTE‐ACS, an early invasive strategy should be weighed against an ischemia‐guided strategy [7]. A more