High-dose dobutamine magnetic resonance tomography can be performed with a standard dobutamine/atropine stress protocol. Detection of wall motion abnormalities by DSMR yields a significantly higher diagnostic accuracy in comparison to DSE.

Myocardial infarction is the result of acute thrombotic occlusion of a coronary artery secondary to rupture of an atherosclerotic plaque. Intracoronary ultrasonic examinations (ICUS) were performed in patients with acute myocardial infarction in order to describe intraluminal ultrasonic findings at the site of an acute coronary occlusion. Coronary angiography and ICUS studies were performed consecutively within 6 h after the onset of chest pain in 50 patients with acute myocardial infarction (AMI) prior to percutaneous coronary angioplasty (PTCA). Following angiographic documentation of a proximal occlusion, a 3.5 mechanical ultrasound catheter (30 MHz) was advanced successfully through the lesion in 42 of 50 patients (84%). In 37 of the 42 patients (88.1%), ICUS differentiated between pulsatile, low echogenic, intraluminal material suggesting thrombus, and mural more highly echogenic atherosclerotic plaque. A negative imprint of the ICUS catheter was documented within the low echogenic material in 25 of 42 (60%) patients with AMI. Low echogenic intraluminal material was found in 31 of 42 (73.4%) segments proximal to the highly echogenic plaque and in 28 of 42 (66.7%) segments distal to it, indicating pre- and post-stenotic thrombus in AMI. The plaque appeared eccentric in 32 of 42 patients (76.2%) with AMI. Cross-sectional area stenosis due to highly echogenic plaque averaged 48 +/- 14%. Calcification of plaque was evident in 35 of 42 patients (83.3%) and the surface of the plaque was rough in 30 of 42 (42.4%). Fissures were found in 10 (23.8%) and a dissection was detected in four (9.5%) cases.

For patients after surgical revascularization, the combination of stress perfusion and LGE yields good diagnostic accuracy for the detection and localization of significant stenoses. However, sensitivity is reduced compared with published data in patients without CABG. Prior myocardial infarction can be examined without loss of accuracy.

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BackgroundAdenosine first pass perfusion cardiovascular magnetic resonance (CMR) yields excellent results for the detection of significant coronary artery disease (CAD). In patients with coronary artery bypass grafts (CABG) the kinetics of a contrast bolus may by altered only due to different distances through the bypass grafts compared to native vessels, thereby possibly imitating a perfusion defect. The aim of the study was to evaluate semiquantitative perfusion parameters in order to assess possible differences in epicardial contrast kinetics in areas supplied by native coronaries and CABG, both without significant stenosis.MethodsTwenty patients with invasive exclusion of significant CAD (control group) and 38 patients with CABG without angiographically significant (≥50%) stenosis in unbypassed coronaries or grafts were retrospectively included in the study. They underwent adenosine first pass (0.05 mmol/kg Gd-DTPA) perfusion (3 short axis views/heart beat) and late gadolinium enhancement (LGE) imaging 1 day before invasive coronary angiography. Areas perfused by native coronaries and/or the different bypasses were identified in X-ray angiography using the 16 segment model. In each of these areas upslope and maximal signal intensity (SImax) relative to the left ventricular parameters, time to 50% maximal signal intensity (TSI50%max) and time to maximal signal intensity (TSImax) were calculated.ResultsIn areas perfused by coronary arteries with bypasses compared to native coronaries relative upslope and relative SImax did not show a significant difference. TSI50%max and TSImax in native coronaries and bypasses were 7.2s ± 1.9s vs. 7.5s ± 1.9s (p < 0.05) and 12.6s ± 3.0s vs. 13.1s ± 3.0s (p < 0.05), respectively. The delay in Tmax resulted in a significant (p < 0.05) delay of 0.5 ± 1.1 heart beats (=images) when adjusted to the heart rate. Differences in time were most pronounced in areas perfused by left internal mammary artery grafts rather than by venous CABG, but were also present between native vessel territories in patients without CAD, albeit with smaller variability.ConclusionAdenosine perfusion CMR in patients post CABG may be associated with a short delay in contrast arrival. However, once the contrast is in the myocardium there is similar wash-in kinetics and peak enhancement. Therefore, since the delay is only short, the possibly differing contrast kinetics through grafts and native vessels does not seem to be a limiting factor for the accuracy of first pass adenosine perfusion in patients post CABG.

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Serial intravascular ultrasound measurements are highly reproducible without any evidence of systematic error and a SD of differences of measurements beyond the maximal spatial resolution of currently available intravascular ultrasound catheters.

The analysis of wall motion abnormalities with dobutamine stress echocardiography is an established method for the detection of myocardial ischemia. With ultrafast magnetic resonance tomography, the application of identical stress protocols as used for echocardiography is possible. In 208 consecutive patients (147 M, 61 F) with suspected coronary artery disease, dobutamine stress echocardiography partially using harmonic imaging and dobutamine stress magnetic resonance tomography (DSMR) were performed prior to cardiac catheterization. DSMR images were acquired during short breath holds in 3 short axis-, a 4-, and a 2-chamber view using a turbo gradient echo technique. Patients were examined at rest and during a standard dobutamine-atropine scheme until submaximal heart rate was reached. Regional wall motion was assessed in a 16 segment model. Significant coronary heart disease was defined as angiographic >/=50% diameter stenosis. With DSMR, significantly more patients yielded very good (69%) or good (13%) image quality in comparison with dobutamine stress echocardiography (20% and 31%, p<0. 05). Moderate image quality occurred in 16% with MR and 41% with dobutamine stress echocardiography (p<0.05), 2% and 8% were non-diagnostic. With each technique 18 patients could not be examined (DSE: emphysema: 10, adipositas: 8, DSMR: claustrophobia: 11, adipositas: 6, contraindication: 1). Four patients did not reach target heart rate. In 107 patients, significant coronary artery disease was found. With DSMR sensitivity was 88.7% (dobutamine stress echocardiography: 74.3%; p<0.05) and specificity 85.7% (dobutamine stress echocardiography: 69.8%; p <0.05). This difference was most pronounced in the group with moderate echocardiographic image quality. High dose DSMR is superior to dobutamine stress echocardiography and can replace this technique especially in patients with moderate echocardiographic image quality.