March was a month of notable progress for cardiac MR, with studies demonstrating the impressive prognostic power of adenosine stress perfusion and dobutamine stress wall motion imaging. The combination was nearly perfect in identifying patients who would be safe from cardiac death or myocardial infarction for at least three years. Recent cardiac imaging studies also affirm fusion imaging's value for diagnosing coronary artery disease.

Stress testing

Prognostic value of cardiac magnetic resonance stress tests: adenosine stress perfusion and dobutamine stress wall motion imaging
Circulation 2007; published online before print March 12, 2007
Based on experience with 513 patients with known or suspected coronary disease, researchers at the German Heart Institute in Berlin found that first-pass adenosine stress MR perfusion and dobutamine stress wall motion studies accurately identify patients at high risk for future cardiac death or nonfatal myocardial infarction. Dr. Cosima Jahnke and colleagues in the laboratory of Dr. Eike Nagel learned that patients can be almost guaranteed that they will be safe from a heart attack or cardiac-related death in the next three years when the two tests are normal. The event-free three-year survival rate for these patients was 99.2%.

Echo wall motion scoring

Incremental value of strain rate imaging to wall motion analysis for prediction of outcome in patients undergoing dobutamine stress echocardiography
Circulation 2007;115:1252-1259
Wall motion scores from dobutamine stress echocardiography have been established as an independent predictor of mortality. This study of 646 patients with known or suspected coronary disease found that peak systolic strain rate, derived from an automated analysis of the strain rate, provides additional prognostic information that can aid the evaluation of the standard wall motion score index.

SPECT/CTA

Integrated single-photon emission computed tomography and computed tomography coronary angiography for the assessment of hemodynamically significant coronary artery lesions
J Am Coll Cardiol 2007;49:1059-1067
The old saw about the whole producing more than the sum of the parts applies to Israeli research demonstrating the ability of fusion SPECT/CTA to diagnose coronary artery disease. Dr. Shmuel Rispler and colleagues at Technion-Israel Institute of Technology in Haifa found that fusion images from the two modalities are far more specific for diagnosing CAD than 16-slice CT alone. Rispler evaluated 224 coronary segments in 56 patients. Though 54 segments were set aside for various reasons, the examination of the remaining 170 segments found a 28 percentage point improvement in specificity for SPECT/CTA compared with CTA alone. Both approaches were 96% sensitive to lesions responsible for 50% or greater stenosis. The results initially reported at the 2006 Society of Nuclear Medicine meeting helped lead nuclear physician Dr. Henry Wagner to select SPECT/CTA of coronary artery disease as his image of the year.

PET/CT

Diagnostic accuracy of rubidium-82 myocardial perfusion imaging with hybrid positron emission tomography/computed tomography in the detection of coronary artery disease.
J Am Coll Cardio 2007;49:1052
Dr. Marcelo Di Carli's group in the nuclear medicine division at Brigham and Women's Hospital demonstrated that rubidium-82 perfusion PET is highly sensitive to obstructive coronary artery disease. The researchers looked at the test's ability to detect occlusions using the standard of 70% or greater stenosis for diagnosing CAD. CT was used only for attenuation correction. Compared with coronary angiography, rest-stress rubidium-82 cardiac PET/CT performed on 64 consecutive patients with suspected CAD was 93% sensitive and 83% specific.

Viability assessment

Acute myocardial infarction early viability assessment by 64-slice computed tomography immediately after coronary angiography: comparison with low-dose dobutamine echocardiography
J Am Coll Cardiol 2007;49:1178-1185
A comparison between 64-slice CT and contrast-enhanced x-ray coronary angiography, using dobutamine echocardiography as a gold standard, found few differences in the results from the three modalities. Dr. Michel Habis and colleagues at the Centre Chirurgical Marie Lannelongue Hospital in Le Plessis Robinson, France, performed the two procedures in close succession on 36 patients admitted for a first acute myocardial infarction. Sixteen segments of the left ventricle were graded with echocardiography as having no, subendocardial, or transmural hyperenhancement. The absence of hyperenhancement or the presence of subendocardial hyperenhancement suggested myocardium viability. Of 576 segments evaluated, 64-slice CT and coronary angiography results correlated for 560 segments. The authors concluded that 64-slice CT after coronary angiography for acute MI generated sensitivity, specificity, accuracy, positive predictive value, and negative predictive value rates of 98%, 94%, 97%, 99%, and 79%, respectively. On a per-patient basis, the diagnostic power of 64-slice CT was 92%, 100%, 94%, 100, and 85%, respectively.

In-stent restenosis

Diagnostic accuracy of coronary in-stent restenosis using 64-slice computed tomography
J Am Coll Cardiol 2007;49:951-959
Dr. Mariko Ehara and colleagues in the cardiology department of Toyohashi Heart Center in Japan found that 64-slice CT angiography is more effective than invasive coronary angiography for ruling out in-stent restenosis. Their results were based on coronary CTA and conventional angiography performed on 125 stented lesions in 81 patients. Invasive coronary angiography identified 24 instances of in-stent restenosis producing sensitivity, specificity, positive predictive value, and negative predictive value of 92%, 81%, 54%, and 98%, respectively, for the overall population. CT coronary angiography correctly diagnosed 20 of 22 cases of in-stent restenosis. Six lesions with in-stent restenosis were overestimated with MSCT.

3T versus 1.5T cardiac MRI

Irreversible myocardial injury: assessment with cardiovascular delayed-enhancement MRI and comparison of 1.5 and 3.0 T — initial experience
Radiology 2007;242;735-742
Delayed-enhancement MRI has become the accepted standard for predicting whether revascularization will induce myocardial recovery. Previous research that established the value of delayed enhancement for predicting the value of revascularization following myocardial infarction was based on imaging performed at 1.5T. Dr. Andrian S.H. Cheng and colleagues, including Dr. Stefan Neubauer at the University of Oxford Center for Clinical Magnetic Resonance Research, demonstrated that by using the same turbo-FLASH pulse sequence, a high degree of agreement was achieved for the delayed-enhancement imaging performed at 1.5T and 3T field strengths.