Author + information
- Published online September 12, 2018.
- Vicente Bodi, MD, PhD∗ ()
- Department of Cardiology, Hospital Clinico Universitario, INCLIVA, CIBERCV, University of Valencia, Valencia, Spain
- ↵∗Address for correspondence:
Prof. Vicente Bodi, Department of Cardiology, Hospital Clinico Universitario, Instituto de Investigación Sanitaria del Hospital Clínico de Valencia, Centro de Investigación Biomédica en Red de las Enfermedades Cardiovasculares, University of Valencia, Blasco Ibanez 17, 46010, Valencia, Spain.
In patients with ST-segment elevation myocardial infarction (STEMI), cardiovascular magnetic resonance (CMR) allows for a simultaneous state-of-the-art assessment of a variety of indexes including volumes, ejection fraction, contractile reserve, edema, hemorrhage, microvascular obstruction, infarct size, and residual ischemia (1,2). Over the past 2 decades, in parallel with the progressive incorporation of all these indexes, we have witnessed extraordinary progress in diagnosis of structural damage, understanding of pathophysiology, risk stratification, and evaluation of the effect of novel therapies in STEMI patients. The decisive step for the definitive introduction of this technique in clinical practice will be the verification of its value in decision making.
The analysis of myocardial strain by feature tracking (FT)-CMR has encapsulated in a relatively short period the road traveled in the study of STEMI patients by CMR. In the past decade, strain based on speckle tracking echocardiography has emerged as a reliable tool to assess the contractile state of the heart under a range of cardiovascular conditions. Unlike conventional visual assessment of wall motion and changes in volume for determining systolic function, strain measures actual tissue deformation within the myocardium (3). This knowledge has rapidly expanded into the field of CMR. FT-CMR tracks features of interest along contour lines on routinely acquired cine images; thus, it does not interfere with routine logistics. This feature, along with its excellent spatial resolution, makes FT-CMR the potential gold standard technique for quantifying myocardial strain in post-infarction patients. In parallel with conventional CMR parameters, the diagnostic and pathophysiological implications of myocardial strain as derived from FT-CMR have already been reported. The independent prognostic value of this method in STEMI patients has been recently confirmed (2).
In this issue of iJACC, Podlesnikar et al. (4) contribute valuable information, paving the way toward the rapid validation of FT-CMR in STEMI patients. For the first time, the authors have demonstrated the ability of this technique to analyze the effect of a novel therapy. Based on their recently published METOCARD-CNIC (Effect of Metoprolol in Cardioprotection During an Acute Myocardial Infarction) trial (5), the authors have solidly demonstrated that early IV administration of metoprolol therapy in the setting of anterior STEMI is associated with improved left ventricular strain at 1 week and with fewer patients having altered strain at 1-week and at 6-month follow-up than controls (4). This outcome confirms their previous results indicating that metoprolol administration before primary percutaneous intervention reduces the incidence of severe systolic dysfunction, both at short- and long-term follow-up (5). Beyond the beneficial effect of early metoprolol therapy on left ventricular parameters (previously demonstrated by the same group), the effects on strain as derived from sequential FT-CMR represents an original methodology that illustrates the robustness and potential of this approach to accurately follow systolic function and validate novel therapies.
Additionally, the study by Podlesnikar et al. (4) provides novel information regarding the dynamics of strain in the months following STEMI, that is, spontaneous recovery toward values that are normal and occurrence of values identical to the well-known dynamics of ejection fraction. Unlike the significant positive effect of metoprolol on ejection fraction, differences between strain in treated patients and that in controls at 6 months were subtler. This suggests the behavior of both indices is not purely colinear and demands further validation of the long-term effectiveness of the intervention. Given the great need to have complementary therapies beyond reperfusion and the expectation created by the encouraging results of IV metoprolol therapy in conventional CMR parameters, the prognostic outcomes from large ongoing trials can be definitive so that this treatment can be incorporated into routine clinical practice.
With the present study (4), FT-CMR has in a few years completed all the stages that, for the other conventional CMR parameters had taken much longer, that is, diagnosis, pathophysiology, risk stratification, and now also assessment of the effect of a novel therapy. In fact, presently, in the setting of STEMI, it is unthinkable to design assays aimed at evaluating the effect of any intervention on the structural cardiac damage without including a comprehensive approach derived from CMR.
Nevertheless, if CMR, including FT-CMR, aspires to be an indispensable technique in the management of STEMI patients, 1 step remains to be met: to demonstrate a strong impact on decision making. Certain areas such as diagnosis and management of intraventricular thrombi by late gadolinium enhancement (6), the guidance of revascularization by stress-CMR (7), and the differential diagnosis between infarction and myocarditis (8) are examples where this technique could be unbeatable in the near future to guide decisions in patients with ischemic heart disease and acute coronary syndromes. However, further studies will be needed in those directions. Regarding strain by FT-CMR, although its value is indisputable, it will always be necessary to demonstrate that the additional time required for its quantification is worthwhile and significantly improves the information provided by the traditional quantification of systolic function using ejection fraction.
Two more points must be taken into consideration to achieve maximum performance and obtain the best information of this powerful technique in the context of STEMI.
First, cardiology departments, in view of their clinical and healthcare reality, must be allowed to define their protocols for use of CMR, avoiding unnecessary tests but also ensuring that no case of the wide spectrum of patients that could potentially benefit from this tool remains unstudied.
Second, the strength of CMR in STEMI resides not only in the quality and quantity of information it can provide but also on how this information is conveyed. CMR reports must include a certain pathophysiological and clinical touch and not just a mere description of findings. This can only be achieved if studies are carried out and reported by personnel, preferably cardiologists, with previous experience in clinical practice and cardiac imaging.
In summary, in parallel with the use of CMR, impressive advances have been made in the fields of diagnosis, pathophysiology, and risk stratification of STEMI that were unimaginable less than 2 decades ago. FT-CMR has made this trip in a very short space of time. With this publication by Podlesnikar et al. (4), FT-CMR arrives at the next stop, namely its routine use in the evaluation of the effect of a novel therapy. More research supporting its value in decision making will probably allow CMR, with FT-CMR already onboard, to reach the final destination of this fabulous journey.
↵∗ Editorials published in Journal of the American College of Cardiology: Cardiovascular Imaging reflect the views of the authors and do not necessarily represent the views of iJACC or the American College of Cardiology.
Dr. Bodi is supported by the Instituto de Salud Carlos III and by Fondo Europeo de Desarrollo Regional (FEDER) grants PIE15/00013, PI17/01836, and CIBERCV16/11/00486.
- 2018 American College of Cardiology Foundation
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