title: Characteristic cardiac phenotypes are detected by cardiovascular magnetic resonance in patients with different clinical phenotypes and genotypes of mitochondrial myopathy.
abstract: BACKGROUND
  Mitochondrial myopathies (MM) are a heterogeneous group of inherited conditions resulting from a primary defect in the mitochondrial respiratory chain with consecutively impaired cellular energy metabolism. Small sized studies using mainly electrocardiography (ECG) and echocardiography have revealed cardiac abnormalities ranging from conduction abnormalities and arrhythmias to hypertrophic or dilated cardiomyopathy in these patients. Recently, characteristic patterns of cardiac involvement were documented by cardiovascular magnetic resonance (CMR) in patients with chronic progressive external ophthalmoplegia (CPEO)/Kearns-Sayre syndrome (KSS) and with mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS). The present study aimed to characterize the prevalence and pattern of cardiac abnormalities and to test the additional diagnostic value of CMR in this patient population. The hypothesis that different neuromuscular MM syndromes present with different cardiac disease phenotypes was evaluated.
  
  
  METHODS
  Sixty-four MM patients (50 ± 15 years, 44% male) and 25 matched controls (52 ± 14 years, 36% male) prospectively underwent cardiac evaluations including CMR (comprising cine- and late-gadolinium-enhancement (LGE) imaging). Based on the neuromuscular phenotype and genotype, the patients were grouped: (a) CPEO/KSS (N = 33); (b) MELAS/-like (N = 11); c) myoclonic epilepsy with ragged-red fibers (MERRF) (N = 3) and d) other non-specific MM forms (N = 17).
  
  
  RESULTS
  Among the 64 MM patients, 34 (53%) had at least one abnormal CMR finding: 18 (28%) demonstrated an impaired left ventricular ejection-fraction (LV-EF <60%), 14 (22%) had unexplained LV hypertrophy and 21 (33%) were LGE-positive. Compared to controls, MM patients showed significantly higher maximal wall thickness (10 ± 3 vs. 8 ± 2 mm, p = 0.005) and concentricity (LV mass to end-diastolic volume: 0.84 ± 0.27 vs. 0.67 ± 0.11, p < 0.0001) with frequent presence of non-ischemic LGE (30% vs. 0%, p = 0.001). CPEO/KSS showed a predominantly intramural pattern of LGE mostly confined to the basal LV inferolateral wall (8/10; 80%) in addition to a tendency toward concentric remodelling. MELAS/-like patients showed the highest frequency of cardiac disease (in 10/11 (91%)), a mostly concentric LV hypertrophy (6/9; 67%) with or without LV systolic dysfunction and a predominantly focal, patchy LGE equally distributed among LV segments (8/11; 73%). Patients with MERRF and non-specific MM had no particular findings. Pathological CMR findings indicating cardiac involvement were detected significantly more often than pathological ECG results or elevated cardiac serum biomarkers (34 (53%) vs. 18 (28%) vs. 21 (33%); p = 0.008).
  
  
  CONCLUSIONS
  Cardiac involvement is a frequent finding in MM patients - and particularly present in KSS/CPEO as well as MELAS/-like patients. Despite a high variability in clinical presentation, CPEO/KSS patients typically show an intramural pattern of LGE in the basal inferolateral wall whereas MELAS patients are characterized by overt concentric hypertrophy and a rather unique, focally accentuated and diffusely distributed LGE.
authors.affiliation: Department of Cardiology and Angiology, University Hospital Münster, Albert-Schweitzer-Campus 1, building A1, 48149, Münster, Germany. ancarezeda.florian@ukmuenster.de.
authors.forename: Anca
authors.initials: A
authors.lastname: Florian
authors.affiliation: Division of Cardiology, Robert-Bosch-Krankenhaus, Stuttgart, Germany. anna.ludwig@rbk.de.
authors.forename: Anna
authors.initials: A
authors.lastname: Ludwig
authors.affiliation: Department of Sleep Medicine and Neuromuscular Disorders, University Hospital Münster, Münster, Germany. bianca.draeger@ukmuenster.de.
authors.forename: Bianca
authors.initials: B
authors.lastname: Stubbe-Dräger
authors.affiliation: Department of Sleep Medicine and Neuromuscular Disorders, University Hospital Münster, Münster, Germany. matthias.boentert@ukmuenster.de.
authors.forename: Matthias
authors.initials: M
authors.lastname: Boentert
authors.affiliation: Department of Sleep Medicine and Neuromuscular Disorders, University Hospital Münster, Münster, Germany. peter.young@ukmuenster.de.
authors.forename: Peter
authors.initials: P
authors.lastname: Young
authors.affiliation: Department of Cardiology and Angiology, University Hospital Münster, Albert-Schweitzer-Campus 1, building A1, 48149, Münster, Germany. johannes.waltenberger@ukmuenster.de.
authors.forename: Johannes
authors.initials: J
authors.lastname: Waltenberger
authors.affiliation: Division of Cardiology, Robert-Bosch-Krankenhaus, Stuttgart, Germany. sabine.roesch@rbk.de.
authors.forename: Sabine
authors.initials: S
authors.lastname: Rösch
authors.affiliation: Division of Cardiology, Robert-Bosch-Krankenhaus, Stuttgart, Germany. udo.sechtem@rbk.de.
authors.forename: Udo
authors.initials: U
authors.lastname: Sechtem
authors.affiliation: Department of Cardiology and Angiology, University Hospital Münster, Albert-Schweitzer-Campus 1, building A1, 48149, Münster, Germany. ali.yilmaz@ukmuenster.de.
authors.forename: Ali
authors.initials: A
authors.lastname: Yilmaz
mesh_terms: D000328:Adult; D000368:Aged; D009202:Cardiomyopathies / Q000453:epidemiology / Q000235:genetics / Q000473:pathology* / Q000503:physiopathology; D016022:Case-Control Studies; D005260:Female; D020022:Genetic Predisposition to Disease; D005858:Germany / Q000453:epidemiology; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D007625:Kearns-Sayre Syndrome / Q000235:genetics / Q000473:pathology; D017241:MELAS Syndrome / Q000235:genetics / Q000473:pathology; D017243:MERRF Syndrome / Q000235:genetics / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D017240:Mitochondrial Myopathies / Q000453:epidemiology / Q000235:genetics / Q000473:pathology* / Q000503:physiopathology; D009206:Myocardium / Q000473:pathology*; D017246:Ophthalmoplegia, Chronic Progressive External / Q000235:genetics / Q000473:pathology; D010641:Phenotype; D011237:Predictive Value of Tests; D015995:Prevalence; D011446:Prospective Studies; D013318:Stroke Volume; D016277:Ventricular Function, Left; D020257:Ventricular Remodeling