Real-time myocardial contrast stress echocardiography using bolus application

A minimally-invasive closed chest myocardial occlusion-reperfusion model in rhesus monkeys (Macaca mulatta): monitoring by contrast-enhanced ultrasound imaging

Myocardial infarction is frequently developed in canine and porcine models but exceptionally in non-human primates. The aim of this study was to develop a minimally invasive myocardial ischemic/reperfusion model in the monkey intended to be combined with imaging techniques, in particular myocardial contrast echocardiography (MCE). A balloon-tipped catheter was advanced via the femoral artery into the left anterior descending artery (LAD) under fluoroscopic guidance in ten anaesthetized male rhesus monkeys (Macaca mulatta). The balloon was inflated to completely occlude the vessel. Coronary angiography (CA) was performed to control the reality of the LAD occlusion/reperfusion. The ischemia period was followed by 3-6 h of reperfusion. Myocardial perfusion was evaluated during ischemia and at reperfusion by MCE using a novel ultrasound contrast agent (BR38). Occlusion was successfully induced during 18-50 min in nine out of the ten evaluated monkeys. ST segment elevation indicated myocardial ischemia. MCE showed complete transmural arrest of myocardial blood flow during the ischemia period and no persistent microvascular perfusion defects during reperfusion. A minimally invasive closed-chest model was successfully developed for creating myocardial ischemia in the rhesus monkey (Macaca mulatta). This technique could have an important role in mimicking acute coronary syndrome under physiologically and ethically-acceptable conditions. MCE provides non-invasively information on myocardial perfusion status, information not available from CA.

Myocardial perfusion imaging with contrast ultrasound

This report reviews the development and clinical application of myocardial perfusion imaging with myocardial contrast echocardiography (MCE). This includes the development of microbubble formulations that permit the detection of left ventricular contrast from venous injection and the imaging techniques that have been invented to detect the transit of these microbubbles through the microcirculation. The methods used to quantify myocardial perfusion during a continuous infusion of microbubbles are described. A review of the clinical studies that have examined the clinical utility of myocardial perfusion imaging with MCE during rest and stress echocardiography is then presented. The limitations of MCE are also discussed.

Evaluation of short-axis and long-axis myocardial function with two-dimensional strain echocardiography in patients with different degrees of coronary artery stenosis

This study was designed to characterize the changes in the peak systolic longitudinal, circumferential and radial strains by using 2-D strain echocardiography in patients with coronary artery stenosis without segmental wall motion abnormalities on conventional 2-D echocardiography. 2D strain echocardiography was performed in 44 patients with different degrees of coronary artery stenosis. Myocardial longitudinal, circumferential and radial strain profiles were obtained and peak systolic strain values were measured. The peak systolic longitudinal strain was significantly reduced in myocardial segments subtended by coronary arteries with greater than 75% stenosis when compared with those subtended by coronary artery with less than 75% stenosis and those in control. Sensitivity and specificity were 74% and 72%, respectively, for peak systolic longitudinal strain to predict segments subtended by coronary arteries with greater than 75% stenosis (cutoff value--17.7%; area under the receiver operating characteristic curve, 0.825). There were no significant differences in circumferential and radial strains among myocardial segments subtended by coronary arteries with greater than 75% stenosis and those with less than 75% stenosis and in control. In conclusion, our study suggests that analysis of long-axis cardiac function by using the 2-D strain echocardiography may help to identify the myocardial segments subtended by coronary arteries with severe stenosis.

Quantitative detection of myocardial ischaemia by stress echocardiography; a comparison with SPECT

Aims

Real-time perfusion (RTP) adenosine stress echocardiography (ASE) can be used to visually evaluate myocardial ischaemia. The RTP power modulation technique angio-mode (AM), provides images for off-line perfusion quantification using Qontrast^® software, generating values of peak signal intensity (A), myocardial blood flow velocity (β) and myocardial blood flow (Axβ). By comparing rest and stress values, their respective reserve values (A-r, β-r, Axβ-r) are generated. We evaluated myocardial ischaemia by RTP-ASE Qontrast^® quantification, compared to visual perfusion evaluation with ^99mTc-tetrofosmin single-photon emission computed tomography (SPECT).

Methods and Results

Patients admitted to SPECT underwent RTP-ASE (SONOS 5500) using AM during Sonovue^® infusion, before and throughout adenosine stress, also used for SPECT. Visual myocardial perfusion and wall motion analysis, and Qontrast^® quantification, were blindly compared to one another and to SPECT, at different time points off-line.

We analyzed 201 coronary territories (left anterior descendent [LAD], left circumflex [LCx] and right coronary [RCA] artery territories) in 67 patients. SPECT showed ischaemia in 18 patients and 19 territories. Receiver operator characteristics and kappa values showed significant agreement with SPECT only for β-r and Axβ-r in all segments: area under the curve 0.678 and 0.665; P < 0.001 and < 0.01, respectively. The closest agreements were seen in the LAD territory: kappa 0.442 for both β-r and Axβ-r; P < 0.01. Visual evaluation of ischaemia showed good agreement with SPECT: accuracy 93%; kappa 0.67; P < 0.001; without non-interpretable territories.

Conclusion

In this agreement study with SPECT, RTP-ASE Qontrast^® quantification of myocardial ischaemia was less accurate and less feasible than visual evaluation and needs further development to be clinically useful.

Head to head comparisons of two modalities of perfusion adenosine stress echocardiography with simultaneous SPECT

BACKGROUND

Real-time perfusion (RTP) contrast echocardiography can be used during adenosine stress echocardiography (ASE) to evaluate myocardial ischemia. We compared two different types of RTP power modulation techniques, angiomode (AM) and high-resolution grayscale (HR), with 99mTc-tetrofosmin single-photon emission computed tomography (SPECT) for the detection of myocardial ischemia.

METHODS

Patients with known or suspected coronary artery disease (CAD), admitted to SPECT, were prospectively invited to participate. Patients underwent RTP imaging (SONOS 5500) using AM and HR during Sonovue(R) infusion, before and throughout the adenosine stress, also used for SPECT. Analysis of myocardial perfusion and wall motion by RTP-ASE were done for AM and HR at different time points, blinded to one another and to SPECT. Each segment was attributed to one of the three main coronary vessel areas of interest.

RESULTS

In 50 patients, 150 coronary areas were analyzed by SPECT and RTP-ASE AM and HR. SPECT showed evidence of ischemia in 13 out of 50 patients. There was no significant difference between AM and HR in detecting ischemia (p = 0.08). The agreement for AM and HR, compared to SPECT, was 93% and 96%, with Kappa values of 0.67 and 0.75, respectively (p < 0.001).

CONCLUSION

There was no significant difference between AM and HR in correctly detecting myocardial ischemia as judged by SPECT. This suggests that different types of RTP modalities give comparable data during RTP-ASE in patients with known or suspected CAD.