JACC: Adenosine stress myocardial contrast echo useful in detecting CAD

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Adenosine myocardial contrast echocardiography (MCE) achieved favorable diagnostic performance in identifying the presence and functional significance of coronary stenosis and may be useful in the clinical setting for evaluating patients with suspected coronary artery disease (CAD), according to a study published in the September issue of the Journal of American College of Cardiology: Cardiovascular Imaging.

"Because contractile dysfunction occurs later in the ischemic cascade, pharmacologic induction of wall motion abnormality presents greater hazard to the patient and results in severe adverse effects in a minority of patients," according to the study.

Therefore, researchers sought to evaluate adenosine in this role as it has a relatively short half-life, "which minimizes adverse effects and facilitates a more time-efficient examination."

The diagnostic performance of combined wall motion/perfusion imaging with adenosine MCE in patients with suspected CAD was evaluated by J. Ranjit Arnold, BMBCh, from University of Oxford Centre for Clinical MR Research, John Radcliffe Hospital in Oxford, England, and colleagues.

They sought to determine the accuracy of adenosine MCE in identifying 1) the presence of anatomic disease, as defined by x-ray angiography, and 2) the functional significance of CAD, as determined by high field strength (3T) multiparametric cardiac MR (CMR) imaging.

The study included 65 patients with suspected CAD who were studied before angiography with MCE and CMR, at stress (140 µg/kg/min intravenous adenosine) and at rest. For MCE, two-, three- and four-chamber long-axis images were acquired during intravenous sulfur hexafluoride infusion. For CMR, short-axis first-pass perfusion and delayed enhancement images were acquired following intravenous gadolinium–diethylenetriaminepentaacetic acid bolus injections (0.05 mmol/kg). Quantitative coronary angiography served as a reference standard for anatomic disease.

Adenosine MCE identified coronary stenosis and its functional significance with favorable diagnostic accuracy. Arnold and colleagues demonstrated that MCE provided diagnostic accuracy of 82 percent, sensitivity of 85 percent and specificity of 76 percent for detecting significant coronary stenosis. Disease location was also identified with reasonable accuracy (diagnostic accuracy 81 percent for left anterior descending disease, 77 percent for left circumflex artery disease, and 84 percent for right CAD).

Moreover, the performance of MCE in diagnosing significant anatomic disease was comparable to that of high-field strength CMR imaging. With CMR as the reference standard for functional assessment, MCE provided diagnostic accuracy of 79 percent, sensitivity of 85 percent and specificity of 74 percent. Interobserver agreement for MCE was 79 percent.

“The results of our small pilot study warrant further confirmation in larger, multicenter studies,” noted the authors. If realized, adenosine MCE could be a useful clinical screening test, combining the favorable diagnostic performance and safety profile of adenosine with the simplicity and bedside convenience of transthoracic echocardiography, concluded Arnold and colleagues.

“Despite the recent setbacks for ultrasound contrast agents and MCE, the study of Arnold et al reminds us that MCE is a technology with great clinical promise. It affirms what many of us who have used MCE in patients have observed for years: it works. This study alerts us that the time is propitious, perhaps more than ever before, to move MCE beyond proof of concept to a place where our patients can genuinely benefit from this imaging technology,” wrote Flordeliza S. Villanueva, MD, director at Center for Ultrasound Molecular Imaging and Therapeutics, Cardiovascular Institute at University of Pittsburgh, in an accompanying editorial.