CTA and stress perfusion imaging play complementary roles in the diagnosis of ischemic heart disease

Research studies published in November and December demonstrate there are no one-stop radiologic shops for the diagnosis of cardiovascular disease. Each modality is endowed with specific strengths that recommend it as the instrument of choice in specific clinical situations.

Ischemic heart disease

Relationship between CT coronary angiography and stress perfusion imaging in patients with suspected ischemic heart disease assessed by integrated PET-CT imaging

J Nucl Cardio 2007; 14(6): 799-809

Dr. Marcelo Di Carli, director of nuclear medicine at Brigham and Women's Hospital, and colleagues investigated the complementary roles of multislice CT angiography and stress rubidium-82 PET perfusion imaging for diagnosing myocardial ischemia. In a series of 110 consecutive patients with suspected coronary artery disease, they demonstrated that CTA is a poor discriminator of patients with myocardial ischemia, while Rb-82 PET perfusion is extremely sensitive for this role. Rb-82 PET, however, is not adept at ruling out the presence of coronary atherosclerosis, a role that CTA plays extremely well. Together the two modalities generate diagnostically powerful information.

Coronary artery stenosis

Comparison of 3D free-breathing coronary MR angiography and 64-MDCT angiography for detection of coronary stenosis in patients with high calcium scores

AJR 2007; 189: 1326-1332

Dr. Xin Liu and colleagues at Northwestern University found that coronary MRA is diagnostically superior to 64-slice CTA for detecting significant coronary artery stenoses in patients with high calcium scores. Eighteen patients who had at least one calcified plaque with a calcium score over 100 were imaged with MSCT, coronary MRA, and coronary angiography. Two observers reached consensus, using a four-point scale, on the MRA image quality of the calcified segments. Three experienced radiologists, blinded to the CAG results, assessed the MSCT and MRA images for significant stenosis and found 33 calcified plaques with a high calcium score. Within those 33 segments, 12 significant stenoses were identified with x-ray angiography. The researchers concluded that sensitivity, specificity, and area under the ROC curve were consistently higher for MRA than the multislice CTA.

Stroke penumbra

Magnetization transfer imaging shows tissue abnormalities in the reversible penumbra

Stroke 2007; 38: 3165

A prospective trial involving 30 patients with acute middle cerebral artery stroke suggests a role for magnetization transfer MRI to evaluate the effectiveness of neuroprotection or reperfusion therapy in the salvageable penumbra after acute ischemic stroke. Dr. Thomas Tourdias and colleagues from the CHU of Bordeaux at the Université Victor Segalen in France performed diffusion- and perfusion-weighted in imaging within 12 hours after stroke onset to measure the presence and extent of diffusion-perfusion mismatch. The final infarct size was established after a month with FLAIR and magnetization transfer MRI. The investigators found that magnetization transfer ratio of normal to abnormal tissue after one month detected the presence of microstructural damage in the salvageable penumbra. Compared with normal tissue, the magnetization transfer ratio was significantly decreased in reversible perfusion (PDual-source CT

Effectiveness of dual-source CT coronary angiography for the evaluation of coronary artery disease in patients with atrial fibrillation: initial experience

Radiology 2007: 245:703-711

A preliminary study involving 15 consecutive patients with suspected coronary artery disease suggests that dual-source CT delivers diagnostic-quality CT coronary angiography for patients with high heart rates including instances of atrial fibrillation. The subjects' mean heart rate was 83.7 bpm (range: 69 to 131 bpm). All patients had an irregular heart rate. Two radiologists blinded to the results of conventional x-ray angiography evaluated the studies. A significant stenosis was defined as greater than 50% coronary occlusion. Retrospective ECG-gated reconstruction was performed during systole. Of 225 segments evaluated, one reader set aside 16 segments as nondiagnostic, and the other reader set aside 13 segments, also because of excess motion. Both readers correctly diagnosed all readable segments. Dr. Dilek Oncel and colleagues at the Sifa Medical Center in Basmane Izmir, Turkey, found that the overall sensitivity, specificity, positive predictive value, and negative predictive of dual-source CT were 87%, 98%, 77%, and 99% for the first reader and 80%, 99%, 80%, and 99% for the second reader.

Tachycardia

Enhanced infarct border zone function and altered mechanical activation predict inducibility of monomorphic ventricular tachycardia in patient with ischemic cardiomyopathy

Radiology 2007; 245; 712-719

A team of cardiologists and bioengineers led by Dr. João A.C. Lima at Johns Hopkins Hospital established that the mechanical behavior of left ventricular wall segments interrogated with tagged contrast-enhanced perfusion MRI helps predict the inducibility of monomorphic ventricular tachycardia in patients with ischemic cardiomyopathy. They ascertained from this prospective study of 46 subjects that patients in whom VT could be induced had more infarcted and border zone sectors and a shorter peak circumferential shortening strain than was the case for noninducible patients in the border zone and in adjacent and infarcted regions.