Scar on MRI Portends Poor Outcome in Viral Myocarditis

February 23, 2012

February 22, 2012 (Stuttgart, Germany) — The presence of scar indicated by late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) imaging is the best independent predictor of poor outcome in patients with viral myocarditis, a new study has shown [1]. The results also reveal that almost 20% of patients with this condition die over five years of follow-up, say Dr Stefan Grün (Robert-Bosch Medical Center, Stuttgart, Germany) and colleagues in their paper published online February 22, 2012 in the Journal of the American College of Cardiology.

Senior author Dr Heiko Marholdt (Robert-Bosch Medical Center) told heartwire : "Myocarditis is dangerous. I think it's really too early to say that with the late enhancement we can predict who dies; we need additional multicenter data to confirm that. However, I think it's quite safe to say it the other way around: no patient without late enhancement died. So if you have myocarditis and you have a normal MR, you are very likely to have a good prognosis."

If you have myocarditis and you have a normal MR, you are very likely to have a good prognosis.

Marholdt, is "that this is likely to hold true also in the population of patients with clinically suspected myocarditis, which is a major problem, because doctors don't know what to do with them. But now if they have a normal MR, they have a good prognosis, and that gives peace of mind to the patient and the doctor."

 

Late enhancement best predictor of poor outcome in unique population

The researchers explain that viral myocarditis is a common cardiac disease that is identified in up to 9% of postmortem examinations. It can progress to cardiomyopathy and appears to be a major cause of sudden, unexpected death. Advanced diagnostic procedures such as CMR have provided new insights into this condition, but it is still not well characterized, and the clinical management remains difficult, because the long-term mortality and potential risk factors for poor clinical outcome are unknown, say Grün et al.

So they followed a total of 222 consecutive patients to evaluate the long-term mortality of viral myocarditis and to establish the prognostic value of various clinical, functional, and CMR parameters. There were 203 patients available for clinical follow-up, and 77 underwent additional MR.

Marholdt points out that the population in this trial is "unique," because they all had biopsy-proven viral myocarditis and a CMR at inclusion, and the follow-up was long, at almost five years. Most previous myocarditis studies have not biopsied patients and/or there has been a gap between the initial presentation and the CMR, "so it's not clean," he notes.

Long-term mortality over the median of 4.7 years of follow-up was 19.2% for all-cause death, 15% for cardiac mortality, and 9.9% for sudden cardiac death.

We clearly find that the late enhancement is by far the best predictor [of poor outcome] in the multivariate analysis.

LGE was present in 108 of the 203 patients and was usually located in the subepicardial or intramural areas of the left ventricle, the researchers explain. The presence of LGE yielded a hazard ratio of 8.4 for all-cause mortality and a more than 10-fold increase in cardiac mortality (HR 12.8), independent of ejection fraction and clinical symptoms, they add.

"When you look at other studies, they often have LVEF as the best predictor of [poor outcome] with myocarditis, but we clearly find that the late enhancement is by far the best predictor in the multivariate analysis," Marholdt commented.

Could those with LGE be treated with beta blockers?

And although prospectively designed international trials are needed to definitely establish LGE as causally related to death risk in myocarditis, treating all myocarditis patients demonstrating LGE with beta blockers--independent of LV function and size--might prevent potentially lethal arrhythmias, says Marholdt.

He notes, however, that this is purely "speculation" at this point, and he and his colleagues plan to test this intervention in a future study.

The authors report no conflicts of interest.

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