CORRESPONDENCE: LETTER TO THE EDITOR
Reply
Marly Conceição Silva, MD,
Zilda Maria Alves Meira, MD, PhD,
Juliana Gurgel Giannetti, MD, PhD,
Mayana Zatz, PhD and
Carlos Eduardo Rochitte, MD, PhD*
* Instituto do Coração do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Setor de Ressonância Magnética e Tomografia Cardiovascular, Avenida Dr. Enéas de Carvalho Aguiar, 44, Andar AB, Cerqueira César, São Paulo, SP 05403-000, Brazil (Email: rochitte{at}incor.usp.br).
We appreciate the letter written in response to our recent article (1). We address the questions of Dr. Giglio and colleagues in the following text.
We demonstrated a clear correlation between amount of myocardial delayed enhancement and lower left ventricular ejection fraction (LVEF). Although only Patients #3 and #9 had low LVEF (47% and 42%) by echocardiography, they had even lower LVEF by CMR (36.7% and 33.6%). Additionally, cardiovascular magnetic resonance (CMR) detected 6 patients with mild to moderate LV dysfunction (4 patients) or low-normal LVEF (2 patients).
We disagree that the focus should be on the wide variability of ejection fraction. Despite the variability (small n), we noted a large and significant difference in LVEF by CMR in patients with versus without MF (48.3 ± 11.0% vs. 66.1 ± 0.6%, p = 0.02), whereas no difference was observed by echocardiography (52.4 ± 8.4% vs. 59.6 ± 5.5%, p = NS). Thus, CMR detected subtle LV function changes in patients with myocardial fibrosis (MF). Even in the range of normal to mild dysfunction, the correlation held true: the higher the amount of MF, the lower the LVEF.
We disagree that contractile dysfunction and MF seem ambiguous. Dysfunctional segments can influence adjacent segment contraction, even those without MF, by a complex relationship that depends critically on the amount of segmental MF, global LV function, and remodeling (2,3).
Lack of muscle biopsy did not turn the final diagnosis incomplete. Patients #2 and #3 have a typical clinical course of Duchenne muscular dystrophy, becoming wheelchair bound before 10 years old. Patients #5 and #6 were siblings and have a positive familial history of X-linked inheritance, excluding limb-girdle dystrophy hypothesis (4). All patients were screened for deletions. Seven cases had no deletions found, with 4 positive muscle biopsy (absence of dystrophin, Patients #7, #8, #9, and #10) confirming the diagnosis. We stated that, in only 3 cases (no exon deletions or biopsy), the diagnosis was based on the classical phenotype and typical familial history.
We apologize for not having cited the article by Giglio et al. (5), which has elegantly demonstrated the capability of ultrasonic tissue characterization in Duchenne patients.
Our conclusions are based solely on CMR’s capability of identifying MF in the myocardium of this small, but sufficient, group of patients. Our conclusion was that CMR is able to detect MF in muscular dystrophy patients earlier than routine cardiologic evaluation, not including any widely unavailable sophisticated technology.
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References
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- Silva MC, Meira ZMA, Campos AFO, et al. Myocardial delayed enhancement by magnetic resonance imaging in patients with muscular dystrophy J Am Coll Cardiol 2007;49:1874-1879.[Abstract/Free Full Text]
- Gerber BL, Rochitte CE, Melin JA, et al. Microvascular obstruction and left ventricular remodeling early after acute myocardial infarction Circulation 2000;101:2734-2741.[Abstract/Free Full Text]
- Kim RJ, Wu E, Rafael A, et al. The use of contrast-enhanced magnetic resonance imaging to identify reversible myocardial dysfunction N Engl J Med 2000;343:1445-1453.[Abstract/Free Full Text]
- Mathews KD, Moore SA. Limb-girdle muscular dystrophy Curr Neurol Neurosci Rep 2003;3:78-85.[CrossRef][Medline]
- Giglio V, Pasceri V, Messano L, et al. Ultrasound tissue characterization detects preclinical myocardial structural changes in children affected by Duchenne muscular dystrophy J Am Coll Cardiol 2003;42:309-316.[Abstract/Free Full Text]
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