Myocardial perfusion imaging (MPI) of patients with negative troponins and low TIMI scores did not detect greater risk of adverse events in a study published online Oct. 1 in Circulation: Cardiovascular Imaging. Likewise, the research team found no benefit in early revascularization of patients with low scores and no detectable ischemia on imaging.

The research team from the Heart and Vascular Institute at the Cleveland Clinic found a very low mortality rate in patients with TIMI scores of 2 or less, regardless of whether or not revascularization was performed. Lead author Paul C. Cremer, MD, and colleagues noted that although abnormal MPI was found in 19.7 percent of the 5,354 patients who were part of the study, of those, ischemic burden was low.

Less than 5 percent ischemia was detected in 9 percent of patients. Ischemia greater than 10 percent was found in 3.6 percent of patients.

Most patients had TIMI scores of 0 or 1 (58.8 percent). Patients with TIMI scores of 2 made up 19.9 percent of the cohort. Fewer patients (14.3 percent) had TIMI of 3. TIMI scores of 4 or 5 comprised the smallest group at only 7 percent of patients.

Inducible ischemia with MPI was low at the lower end of TIMI scores. Ischemic myocardium of at least 5 percent was seen in 4.9 percent of patients with TIMI scores of 1 or less and 9.5 percent of patients with TIMI of 2. Patients with higher TIMI scores were more likely to have at least 5 percent ischemic myocardium.

Very few of those patients with TIMI scores of 2 or less had 10 percent ischemic myocardium (2.3 percent), whereas 8.3 percent of patients with scores of 3 or higher had 10 percent involvement.

While most patients with more than 5 percent ischemia had coronary angiography after these findings (74.4 percent), only little more than half of the patients who underwent more invasive testing were found to have obstructive coronary artery disease or stenosis of 50 percent or more. Most of those patients had TIMI scores in the upper range.

At 30 days, very few patients had died (0.1 percent) and 3.5 percent of patients had revascularizations. Over the intervening follow-up of approximately 3.4 years, 6.5 percent of all patients died, including 11.2 percent of patients who had undergone early revascularization.

Due to overall low detection of increased risk in ischemic patients with low TIMI scores and no significant association with increased mortality in a multivariable model, Cremer et al recommended that MPI prior to discharge after two negative troponin tests be considered only in patients with TIMI of 3 or more.

“These findings make it difficult to justify routine provocative testing for all patients presenting to the ED with chest pain,” Cremer et al wrote. “Selective provocative testing may be considered in patients with negative troponins and TIMI scores > 3, though the benefit of intensive inpatient treatment and early revascularization in any patient with resolved chest pain, non-diagnostic ECGs [echocardiograms], and negative serial troponins is uncertain.”