ORLANDO – A novel diagnostic strategy of performing CT angiography or cardiovascular MRI first in patients with suspected non-ST-elevation MI safely improved appropriate selection for invasive coronary angiography in the Dutch randomized CARMENTA trial.
The strategy of using noninvasive imaging first significantly cut down on the high proportion of diagnostic invasive angiography procedures that end up showing no significant obstructive coronary artery disease in the current era of high-sensitivity cardiac troponin assays,, reported at the annual meeting of the American College of Cardiology.
(Cardiovascular Magnetic Resonance Imaging and Computed Tomography Angiography) was a single-center, prospective, randomized trial including 207 patients with suspected NSTEMI on the basis of acute chest pain, an elevated high-sensitivity cardiac troponin level, and an inconclusive ECG. They were randomized to one of three diagnostic strategies: a routine invasive strategy in which they were sent straight to the cardiac catheterization lab for invasive coronary angiography, or either CTA- or CMR-first as gatekeeper strategies in which referral for invasive angiography was reserved for only those patients whose noninvasive imaging demonstrated myocardial ischemia, infarction, or obstructive CAD with at least a 70% stenosis.
The impetus for the trial was the investigators’ concern that widespread embrace of high-sensitivity cardiac troponin assays has resulted in a serious clinical problem: Although these assays offer very high sensitivity for rapid detection of acute MI, their positive predictive value is only 56%, compared with 76% for the older troponin assays.
“That means almost one out of two patients with acute chest pain and an elevated high-sensitivity troponin level does not have a type 1 MI. We see a twofold higher incidence of elevated troponin levels with these assays, so there has been a significant increase in referrals for invasive angiography – and up to one-third of these patients with suspected NSTEMI don’t have an obstructive stenosis. We need a strategy to improve patient selection,” explained Dr. Smulders of Maastricht (the Netherlands) University.
The CARMENTA strategy worked. The primary outcome – the proportion of patients with suspected NSTEMI who underwent invasive coronary angiography during their initial hospitalization – was 65% in the CTA-first group and 77% in the CMR group, compared with 100% in the routine invasive-strategy control group. Moreover, fully 38% of patients in the control group turned out not to have obstructive CAD, compared with 15% who were sent for invasive angiography only after CTA and 31% who first had CMR.