Prof. Albert C Van Rossum,
View the Slides from this session in ESC Congress 365
The first presentation by Juerg Schwitter (Lausanne, CH) focussed on the strengths and weaknesses of myocardial perfusion stress CMR. The diagnostic performance of adenosine induced myocardial stress perfusion CMR was illustrated by the results of the Impact I and II studies, and the CE-MARC study, demonstrating non-inferiority and superiority to nuclear imaging with SPECT in the detection of hypoperfused myocardium. Owing to the high spatial resolution of CMR (1.5-2.5 mm) endocardial hypoperfusion may be differentiated from epicardial perfusion, allowing to identify balanced ischemia in three-vessel disease. Other strengths include rapid assessment of both stress and rest perfusion, combined with ejection fraction and scar imaging within 45 minutes, and the absence of X-ray exposure. Weaknesses include the relatively low availability of CMR equipment and the lack of specific expertise. Absolute contra indications are ferromagnetic implants, aneurysm clips of unknown material, and implantable cardiac devices. With recently introduced new generation MRI conditional pacemakers, patients may undergo CMR in a controlled situation if the benefit of imaging outweighs possible adverse events. Conditional ICD’s will soon be introduced. Nephrogenic Systemic Fibrosis, a rare complication of gadolinium contrast agents, is virtually absent if these contrast agents are avoided in patients with eGFR < 30 ml/min/ 1.72 m2.
Andrew Arai (Bethesda, US) discussed the role of CMR in acute coronary syndromes. According to the guidelines coronary angiography and echocardiography, but not CMR, have a role in the initial presentation of ACS. Nevertheless, using a very specific set-up of MRI equipment directly next to the Emergency Department (ED), his group demonstrated the capability of CMR to early detect NSTEMI missed by ECG and initial Troponine. In patients presenting to the ED with chest pain, a negative adenosine stress perfusion CMR was prognostically favourable, the negative predictive value for MACE being 100%. It then is cost-effective, since it reduces unnecessary coronary angiography, hospital readmission, and recurrent cardiac testing in intermediate-risk patients with acute chest pain. Using gadolinium late enhancement CMR within the first week of infarction, the presence of microvascular obstruction has a prognostic significance worse than merely infarct size. Finally, adding T2-weighted imaging detects myocardial edema that has been associated with the area at risk. According to the guidelines however, the role of CMR in ACS starts before or after discharge when patients with multivessel disease require additional testing for ischemia or viability that may need revascularization. Probably current guidelines under represent the power of what CMR can do.
James Moon (London, UK) discussed the role of gadolinium late enhancement (LE) in the pre-interventional assessment of ischemic cardiomyopathy. He stressed the multimodality information obtained in one scan, consisting of cine imaging for measuring volumes and ejection fraction, scar imaging by LE, and myocardial perfusion imaging. Also, there may be a future role for T1-mapping to assess diffuse fibrosis. The LE technique for scar imaging has been extremely well validated. When used in a quantitative manner it has incremental value over EF. The pattern of enhancement is helpful to discern CAD from myocarditis, from atypical chest pain in hypertrophic cardiomyopathy, and to assess `dual pathology’, e.g. `bystander’ myocardial infarction in a patient with a dilated cardiomyopathy. Although after results from the STITCH trial - with all its limitations – the role of assessing non-scarred but dysfunctional (hibernating) myocardium to guide revascularization has become debatable, it is clear that patients with extreme 3 vessel coronary disease and only little subendocardial scar clearly benefit form revascularization with considerable improvement of their LVEF. Also, the localization and transmural extent of scar is helpful in guiding PCI of chronic total occlusions.
Finally, Esther Perez David (Madrid, ES) gave an overview of the incremental prognostic information of CMR in ischemic heart disease. In both acute and chronic ischemic heart disease the prognostic value is derived from the multiple prognostic parameters obtained by cine, gadolinium LE, and stress imaging (either adenosine perfusion or dobutamine wall motion). In the chronic situation, scar imaging by LE CMR detected previously unrecognized myocardial infarction in 20% of 1000 unselected patients > 70 yrs, thereby identifying a group at risk. In patients presenting with signs or symptoms of CAD the hazard ratio for MACE or mortality of unrecognized scar was shown to be 6 and 9.4 respectively. Scar also predicts adverse remodelling after healed myocardial infarction, the likelihood of recovery of myocardial dysfunction after revascularization, and the response to cardiac resynchronization therapy in patients with dyssynchrony. In patients with known or suspected CAD, stress myocardial perfusion and LE imaging had complementary adverse prognostic value. LE tissue heterogeneity or `grey zone’ identifies arrhythmia susceptibility in patients with LV dysfunction (EF < 35%). In patients with monomorphic VT and VF, RF ablation was successful in 77% of cases when performed within 5 mm of intrascar heterogeneous tissue channels. Thus, LE CMR signal intensity mapping may become a helpful tool in guidance of VT ablation.
Overall, the greatest incremental value of CMR over other imaging techniques is its capability to directly obtain information on the composition of the myocardial tissue. As such it offers unique information on myocardial pathology that can not, or only indirectly be obtained by other imaging modalities.
Role of cardiovascular magnetic resonance in the ischaemic heart disease: from diagnosis to prognosis
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