Photo by Sage Ross
Aspirin tablets
Researchers believe a new tool could help physicians predict the risks and benefits of extended dual antiplatelet therapy (DAPT) in patients who have undergone percutaneous coronary intervention (PCI).
The team said the tool, known as the DAPT Score, exhibited “modest accuracy” for determining which patients were at high risk for late ischemic events and would therefore benefit most from longer-term DAPT therapy.
The DAPT Score also proved somewhat accurate for identifying patients who were at high risk of late bleeding events and might be harmed by continuing DAPT for more than a year after PCI.
Still, the researchers said the scoring system requires further validation and prospective evaluation to assess its potential effects on patient care.
Robert W. Yeh, MD, of Beth Israel Deaconess Medical Center in Boston, Massachusetts, and his colleagues reported these results in JAMA.
“Dual antiplatelet therapy is standard for patients following coronary stent procedures, but we haven’t had good tools to help us determine how long we should be treating individual patients,” Dr Yeh said.
So he and his colleagues set out to identify factors that would predict whether the expected benefit of reduced ischemia would outweigh the expected increase in bleeding associated with continuing DAPT for more than a year after PCI.
The team used 11,648 patients treated on the DAPT study to create the DAPT Score. Patients in this trial had a drug-eluting stent placed, then received 12 months of open-label thienopyridine plus aspirin. After that, they were randomized to 18 months of continued thienopyridine plus aspirin or placebo plus aspirin.
The DAPT Score was designed to distinguish ischemic and bleeding risk 12 to 30 months after PCI. Patients are given a numerical score (-2 to 10) based on certain risk factors. They receive:
- 1 point each for myocardial infarction at presentation, prior myocardial infarction or PCI, diabetes, stent diameter less than 3 mm, smoking, and paclitaxel-eluting stent
- 2 points each for history of congestive heart failure/low ejection fraction and vein graft intervention
- −1 point for age 65 to younger than 75
- −2 points for age 75 or older.
The researchers validated the DAPT Score in 8136 patients from the PROTECT trial. In this trial, researchers assessed the effect of DAPT on the incidence of stent thrombosis at 3 years in patients randomized to receive the Endeavor zotarolimus-eluting stent or the Cypher sirolimus-eluting stent.
After stent placement, patients were assigned to receive aspirin indefinitely and clopidogrel/ticlopidine for at least 3 months and up to 12 months.
Results in DAPT cohort
In the DAPT cohort, ischemia occurred in 348 patients (3.0%), and bleeding occurred in 215 (1.8%).
The researchers said the derivation cohort models predicting ischemia and bleeding had moderate discrimination, with c statistics of 0.70 and 0.68, respectively. After bootstrap internal validation, optimism-corrected c statistics were 0.68 and 0.66, respectively.
The researchers also compared patients with high DAPT scores (≥2 points) to those with lower scores (<2). As expected, continued DAPT was associated with larger reductions in ischemia and smaller increases in bleeding in the high-score group (n=5917) than in the low-score group (n=5731).
In the high-score group, the incidence of ischemia was 2.7% for continued DAPT and 5.7% for placebo plus aspirin (P<0.001). In the low-score group, the incidence was 1.7% for continued DAPT and 2.3% for placebo plus aspirin (P=0.07; interaction P<0.001).
In the high-score group, the incidence of bleeding was 1.8% for continued DAPT and 1.4% for placebo plus aspirin (P=0.26). In the low-score group, the incidence was 3.0% for continued DAPT and 1.4% for placebo plus aspirin (P<0.001; interaction P=0.02).
Results in PROTECT cohort
In the PROTECT cohort, ischemia occurred in 79 patients (1.0%) and bleeding in 37 patients (0.5%). Again, the models predicting ischemia and bleeding had moderate discrimination, with c statistics of 0.64 for both outcomes.
The rate of ischemia from 12 through 30 months after PCI was greater among the high-score patients (n=2848) than the low-score patients (n=5288). The rates were 1.5% and 0.7%, respectively. The hazard ratio was 2.01 (P=0.002).
Rates of moderate or severe bleeding were not significantly different by DAPT Score. The rates were 0.4% in the high-score patients and 0.5% in the low-score patients. The hazard ratio was 0.69 (P=0.31).
The researchers said that, based on these results, use of the DAPT Score should be cautious pending further validation.
“We haven’t prospectively validated the use of the score, and it’s only applicable to patients similar to those who were randomized in the DAPT study, so we still need to be cautious,” Dr Yeh said. “Nevertheless, we think it represents a significant step forward in understanding benefits and risks of treatment.”
