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Myocardial perfusion imaging: state of the art

Non-Invasive Imaging


Webcast Echocardiography
by Petros Nihoyannopoulos (UK)

WebcastCardiovascular magnetic resonance
by Dudley Pennell (UK)
 

WebcastSingle-photon emission computed tomography
by Marco Mazzanti (IT)

WebcastPositron emission tomography
by Thomas Hellmut Schindler (CH)

I had the pleasure to chair the session entitled “Myocardial Perfusion Imaging: State of The Heart”. The session was a pleasant overview of the field done by four remarkable Speakers, each of them with long and consolidated experience in the imaging modality they were requested to discuss.

The first speaker (Dr D. Pennell form London - UK) showed the great potential of cardiac MR (CMR) in the assessment of myocardial perfusion. He started from the consolidated results of multicenter trials such as IMPACT I where CMR showed a pretty high level of diagnostic accuracy even superior to that shown by SPECT in the detection of Coronary Artery Disease (CAD). Dr Pennell also showed the unexplored possibilities that the use of innovative contrast agents can make available for the cardiologist in the future. He also addressed the unique possibility of CMR in evaluating myocardial perfusion without the use of contrast agent based on the oxygen extraction fraction (oxygenated/de-oxygenated haemoglobin, BOLD-OEF technology). He concluded by mentioning the development of new technological developments (more rapid sequences for acquiring images, scanners equipped with magnets operating at higher strength field (3T).etc ).

The second Speaker (Dr Mazzanti from Ancona – Italy) underlined the enormous amount of data available on the value of SPECT imaging in the field of CAD for the detection of inducible ischemia, viability, ventricular function, etc. Furthermore, he also mentioned the capability of SPECT to obtain quantitative measurements of myocardial perfusion as clearly shown by different groups. Among the already proposed application of SPECT he mentioned the capability to evaluate LV Dyssynchrony.

Finally, in the last part of his talk, special attention was given to the new generation of gamma-Cameras equipped with hyper efficient crystals (CZT technology) which significantly reduce the time requested for acquisition and the dosage of radioisotopes to be administered. This latter aspect has been extensively commented by the Speaker who namely showed nice images obtained with a dosage of one/third of the dosage used with a “traditional” gamma-Camera.

The third speaker (P. Nihoyannopoulos from London – UK) nicely reported to the audience the extreme flexibility of Echocardiography and the added values of ultrasound contrast agent (microbubbles) which can be used either to further increase the quality of images with the aim of a better definition of endocardial borders or to evaluate myocardial perfusion. The latter takes advantage of the high spatial and temporal resolution of Echocardiography. Over the years, both the equipment (second harmonic, pulsed power etc.) and the contrast agents (stability, dimension of microbubbles, etc) have been progressively improved in such a way that nowadays, it is realistic to envisage the use of contrast echocardiography to assess myocardial perfusion either in baseline condition (myocardial infarction, etc) or during stress. In the latter case, the use of contrast agent can improve both the evaluation of functional reserve and the presence of underperfused area and in such a way further improve the already high diagnostic accuracy.

The speaker also addressed the safety issue. Several multicenter trials enrolling tens of thousands of patients have shown that these contrast agents, if used properly, have an extremely high level of safety. Finally, the speaker opened the new window of 3D Echocardiography which looks extremely promising for the evaluation of regional myocardial perfusion partially reducing the operator dependency in acquiring images.

The fourth speaker (Dr Schindler form Geneva – Switzerland) had the responsibility of defending Positron Emission Tomography (PET) which is considered the gold standard in the clinical evaluation of myocardial perfusion. After many years, in fact, PET is still the only method systematically used for evaluating myocardial Blood Flow in a quantitative manner (ml/min/g). The use of tracers such as Oxigen-15 water, Nitrogen-13 ammonia, Rubidium-82 Chloride have proven to give such realistic results to have a sensitivity and specificity of 92-91 % in detecting underperfused myocardium due to coronary atherosclerosis, even when the stenosis is far from being significant.

Furthermore, combining PET perfusion images and the morphologic images of coronary arteries by CT-PET, a comprehensive evaluation of the underlying pathophyisiology can be achieved by the same method.

In conclusion, one can expect that after a session such this, a winner is identified. However, the pathophysiology of CAD, of ischemia and the clinical situation are so different for each patient that none of the methods discussed fulfils all the expectations. Better to havemore than one method available and select the best fitting approach in each patient. The more methods that are available, the more perfusion is evaluated in the patients so achieving a better understanding of underlying pathology.

References


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SessionTitle:

Myocardial perfusion imaging: state of the art

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.