Stress echo is inexpensive, effective way to stratify risk for ACS patients

Stress echocardiography incorporated into a chest pain unit has excellent feasibility, provides rapid assessment and discharge with accurate risk stratification of patients with suspected acute coronary syndrome (ACS) but nondiagnostic ECG and negative 12-hour troponin, based on a retrospective study published January in Circulation: Cardiovascular Imaging.

Patients presenting to the emergency department (ED) with chest pain represent a significant healthcare burden; the estimated annual cost to the U.S. economy is $10 billion to $12 billion (Natl Health Stat Report 2008;7:1-38). A large proportion of ED admissions are patients with suspected ACS, but with a nondiagnostic ECG and a normal 12-hour troponin, though less than half are subsequently diagnosed with ACS, according to the study authors. A retrospective study found that the mean cost per patient was approximately $3,200, with 73 percent of cost attributable to admission time (BMC Emerg Med 2006;6:6).

Even though stress echocardiography is a safe, rapid and reliable investigation that does not involve exposure to ionizing radiation, no studies to date have evaluated the clinical impact of incorporating stress echo, performed early for the assessment of both short- and long-term prediction of hard events (all-cause mortality and acute MI), into a real-world chest pain unit.

Thus, Benoy N. Shah, BSc, MBBS, of the department of cardiovascular medicine at Northwick Park Hospital in Harrow, England, and colleagues assessed the feasibility, safety, impact on patient triaging and discharge times and the accuracy of stress echocardiography in risk stratification for prediction of hard events in 839 consecutive patients who underwent clinical, ECG and stress echocardiography assessments at one chest pain unit within 24 hours of admission.

The researchers sought to assess the feasibility, safety, impact on triaging and discharge, 30-day readmission rate and the patients were followed-up for hard events (all-cause mortality and acute MI [AMI]).

Of the 839 patients, 96.7 percent had conclusive diagnostic stress echocardiography results, and they obtained diagnostic stress echo images in more than 99 percent of the participants. “This is probably because contrast agents were used whenever image quality was deemed suboptimal,” wrote Shah et al. “Utilization of contrast agents was 52 percent. ...This finding is very important because inconclusive or indeterminate tests result in additional investigations and prolonged time in hospital, both of which increase cost.”

The median time to stress echo and median length of stay for normal stress echocardiography patients (77 percent) were both one day. The 30-day readmission rate was 0.5 percent, the researchers reported, and over long-term follow-up of 27 months, 39 hard events occurred (30 deaths and nine AMI events).

Among all prognostic variables, only abnormal stress echocardiography and advancing age predicted hard events in multivariable regression analysis.

The results also showed that stress echocardiography appropriately influences the use of coronary angiography and subsequent revascularization. Only 0.2 percent of patients with a normal stress echo required revascularization with “an excellent outcome” (event free survival, more than 99 percent in the first year), reported the authors. On the other hand, 84 percent of the patients who underwent stress echo with ischemia underwent coronary angiography, with 70 percent of patients demonstrating flow-limiting coronary artery disease.

The researchers acknowledged the limitations of their study; namely, its retrospective nature and nine patients were lost to follow-up. They defended the use of a single, expert reader as a “strength rather weakness as, in routine clinical practice, all such tests would indeed be performed by a staff physician and interpreted with the assistance of an expert.”

The “study highlights the excellent negative predictive value of stress echocardiography and very low 30-day readmission rate,” wrote Shah and colleagues. “In summary, the results of our study—excellent feasibility and safety of SE [stress echo], rapid early triaging and discharge and accurate risk stratification—together with the ubiquitous availability, low cost, portability and excellent prognostic data of stress echocardiography support the wider use and incorporation into chest pain units of stress echocardiography.”