Assessment of flow mismatch with pharmacologic stress test on myocardial contrast echocardiography in a model of critical stenosis: adenosine triphosphate and dipyridamole

The quantification of dipyridamole induced changes in regional deformation in normal, stunned or infarcted myocardium as measured by strain and strain rate: an experimental study

Strain rate imaging (SRI) during dobutamine stress-echocardiography (DSE) has been shown to differentiate between ischemic substrates based on the segmental response. Dipyridamole stress echo (DIPSE) is currently used as an alternative to DSE in detecting coronary artery disease. The aim of this study was: (a) to determine the normal response in peak-systolic myocardial strain (S) and strain-rate (SR) during DIPSE and (b) to compare the S and SR responses of DSE and DIPSE in the same chronically ischemic/infarcted segments in the setting of single vessel disease.

METHODS

The deformation response to DIPSE was studied in 7 normal pigs and in an additional 18 pigs, with a spectrum of ischemic substrates. S and SR data were extracted from a posterior wall "at risk" segment at baseline and during both DSE and DIPSE. The animals were divided into different ischemic substrate (stunning, non-transmural and transmural infarction), based on the DSE response as previously suggested.

RESULTS

In normal myocardium, dipyridamole induced no changes in regional systolic deformation neither during nor after the infusion. Furthermore there was no detectable response in S and SR in segments with either a non-transmural or a transmural infarction. However, in myocardial segments with a DSE "stunning response", both end systolic S and peak-systolic SR tended to "normalize" at peak dipyridamole dose.

CONCLUSIONS

These results suggest that dipyridamole does not induce changes in regional deformation in normal or (partially) infarcted myocardium. Only in stunned myocardium (in the setting of single-vessel disease), dipyridamole tends to normalize deformation.

Correlation between myocardial perfusion abnormalities detected with intermittent imaging using intravenous perfluorocarbon microbubbles and radioisotope imaging during high-dose dipyridamole stress echo

BACKGROUND

The clinical accuracy of myocardial contrast echocardiography (MCE) using intermittent harmonic imaging and intravenous perfluorocarbon containing microbubbles during dipyridamole stress has not been evaluated in a multicenter setting.

HYPOTHESIS

The accuracy of dipyridamole stress contrast echo in the detection of coronary artery disease (CAD) using myocardial perfusion images is high in comparison with technetium-99 (99Tc) sestamibi single-photon emission computed tomography (MIBI SPECT) and increases the accuracy of wall motion data.

METHODS

In 68 consecutive nonselected patients (46 men; mean age 66 years) from three different institutions in two countries. dipyridamole stress echo and SPECT with 99mTc MIBI were compared. Continuous intravenous (IV) infusion of perfluorocarbon exposed sonicated dextrose albumin (PESDA) (2-5 cc/min) was administered for baseline myocardial perfusion using triggered harmonic end systolic frames. Real-time digitized images were used for wall motion analysis. Dipyridamole was then injected in two steps: (1) 0.56 mg/kg for 3 min, (2) 0.28 mg/kg for 1 min, if the first step was negative for an inducible wall motion abnormality. After dipyridamole injection, myocardial contrast enhancement and wall motion were analyzed again by the same methodology.

RESULTS

There were 35 patients with perfusion defects by SPECT. Wall motion was abnormal in 22, while MCE was abnormal in 32. Wall motion and MCE each had one false positive. The proportion of correctly assigned patients was significantly better with MCE than with wall motion (p = 0.03; chi square test).

CONCLUSIONS

Myocardial contrast echocardiography, using intermittent harmonic imaging and intravenous perfluorocarbon containing microbubbles, is a very effective method for detecting coronary artery disease during dipyridamole stress echo.

T2-prepared Steady-State Free Precession Blood Oxygen Level–Dependent MR Imaging of Myocardial Perfusion in a Dog Stenosis Model

PURPOSE

To assess the ability of a T2-prepared steady-state free precession blood oxygen level-dependent (BOLD) magnetic resonance (MR) imaging sequence to depict changes in myocardial perfusion during stress testing in a dog stenosis model.

MATERIALS AND METHODS

Study was approved by the institutional Animal Care and Use Committee. A hydraulic occluder was placed in the left circumflex coronary artery (LCX) in 10 dogs. Adenosine was administered intravenously to increase coronary blood flow, and stenosis was achieved in the LCX with the occluder. A T2-prepared two-dimensional steady-state free precession sequence was used for BOLD imaging at a spatial resolution of 1.5 x 1.2 x 5.0 mm3, and first-pass perfusion images were acquired for visual comparison. Microspheres were injected to provide regional perfusion information. Mixed-effect regression analysis was performed to assess normalized MR signal intensity ratios and microsphere-measured perfusion differences. For the same data, 95% prediction intervals were calculated to determine the smallest perfusion change detectable. Means +/- standard deviations were calculated for myocardial regional comparison data. A two-tailed Student t test was used to determine if significant differences (P < .01) existed between different myocardial regions.

RESULTS

Under maximal adenosine stress, MR clearly depicted stenotic regions and showed regional signal differences between the left anterior descending coronary artery (LAD)-fed myocardium and the stenosed LCX-fed myocardium. Visual comparisons with first-pass images were also excellent. Regional MR signal intensity differences between LAD and LCX-fed myocardium (1.24 +/- 0.08) were significantly different (P < .01) from differences between LAD and septal-fed myocardium (1.02 +/- 0.07), which was in agreement with microsphere-measured flow differences (LAD/LCX, 3.38 +/- 0.83; LAD/septal, 1.26 +/- 0.49). The linear mixed-effect regression model showed good correlation (R = 0.79) between MR differences and microsphere-measured flow differences.

CONCLUSION

On T2-prepared steady-state free precession BOLD MR images in dogs, signal intensity differences were linearly related to flow differences in myocardium, with a high degree of correlation.

SUPPLEMENTAL MATERIAL

radiology.rsnajnls.org/cgi/content/full/236/2/503/DC1