Author + information
- Hamza El Aidi, MD∗ (, )
- Arthur Adams, MD, PhD,
- Pieter Doevendans, MD, PhD,
- Eike Nagel, PhD and
- Tim Leiner, MD, PhD
- ↵∗Department of Cardiology, University Medical Center Utrecht, Heidelberglaan 100, P.O. Box 85500 HP E01.132, 3508 GA Utrecht, the Netherlands
We thank Drs. Eitel and Thiele for the interest in our work (1). They highlight some possible limitations of our approach on several points that merit discussion.
Cardiovascular magnetic resonance imaging (CMR) is a continuously evolving technique, which leads to new opportunities and the expansion of indications. In our systematic review, we summarized all published papers regarding the prognostic value of CMR findings in patients with a recent myocardial infarction (MI) or suspected or known coronary artery disease.
As mentioned in our study, if the CMR finding was studied in <1,000 patients, it was classified as “not enough evidence to make inference about its prognostic value” (1). Although this value is arbitrarily chosen, lowering this threshold would lead to more CMR findings incorrectly being classified as an independent prognostic marker. In the majority of studies, the number of events/variable in multivariable analyses was less than 10, leading to a possible overestimation or underestimation of the reported hazard ratios in those studies (2). Although there is no established threshold, we considered the value of 1,000 patients to be appropriate.
We concluded that none of the CMR findings, including left ventricular ejection fraction (LVEF), was studied in more than 1,000 patients with an MI, and therefore no inferences could be made about its independent prognostic value to predict hard clinical events. The prognostic value of late microvascular obstruction (MVO) was assessed in 2 papers, including 624 patients, and 1 of the studies showed a significant result.
We found that LVEF is an independent prognostic CMR finding to predict major adverse cardiovascular events in patients with a recent MI. As for late MVO, all 3 studies including 668 patients showed a significant result. This shows that late MVO is a promising CMR finding to predict future events but is not studied in enough patients yet. Due to the difference between studies in CMR findings included in the multivariable analyses, we were not able to directly compare the prognostic value of the CMR findings. Therefore, we can conclude that LVEF is an independent CMR finding, but its relative value with respect to (other) CMR findings, such as late MVO, could not be studied.
We agree that heterogeneity in reporting and statistical analyses is an important limitation of the results presented in systematic reviews. We therefore could not aggregate the results of the individual studies. As discussed in our paper (1) and the associated editorial (3), a large individual patient data meta-analysis can provide more information on the relative prognostic value of CMR findings. We recently started the PROMISE collaboration (4) to collect data from published studies assessing the prognostic value of CMR. By analyzing data from previously published studies that might be underpowered themselves on the patient level and by accounting for differences in patient and study characteristics, the incremental value of the CMR findings, in addition to already known risk factors, can be assessed. In this way, readily available data can be used, and it might not be necessary to spend costly resources to perform multicenter studies that require a large number of patients and long-term follow-up, as suggested by Drs. Eitel and Thiele.
- American College of Cardiology Foundation
- El Aidi H.,
- Adams A.,
- Moons K.G.,
- et al.
- Gottlieb I.,
- Camargo G.
- ↵PROMISE. Available at: http://www.promise-ipd.com. Accessed September 9, 2014.