A homozygous DSC2 deletion associated with arrhythmogenic cardiomyopathy is caused by uniparental isodisomy.

AIMS: We aimed to unravel the genetic, molecular and cellular pathomechanisms of DSC2 truncation variants leading to arrhythmogenic cardiomyopathy (ACM). METHODS AND RESULTS: We report a homozygous 4-bp DSC2 deletion variant c.1913_1916delAGAA, p.Q638LfsX647hom causing a frameshift carried by an ACM patient. Whole exome sequencing and comparative genomic hybridization analysis support a loss of heterozygosity in a large segment of chromosome 18 indicating segmental interstitial uniparental isodisomy (UPD). Ultrastructural analysis of the explanted myocardium from a mutation carrier using transmission electron microscopy revealed a partially widening of the intercalated disc. Using qRT-PCR we demonstrated that DSC2 mRNA expression was substantially decreased in the explanted myocardial tissue of the homozygous carrier compared to controls. Western blot analysis revealed absence of both full-length desmocollin-2 isoforms. Only a weak expression of the truncated form of desmocollin-2 was detectable. Immunohistochemistry showed that the truncated form of desmocollin-2 did not localize at the intercalated discs. In vitro, transfection experiments using induced pluripotent stem cell derived cardiomyocytes and HT-1080 cells demonstrated an obvious absence of the mutant truncated desmocollin-2 at the plasma membrane. Immunoprecipitation in combination with fluorescence measurements and Western blot analyses revealed an abnormal secretion of the truncated desmocollin-2. CONCLUSION: In summary, we unraveled segmental UPD as the likely genetic reason for a small homozygous DSC2 deletion. We conclude that a combination of nonsense mediated mRNA decay and extracellular secretion is involved in DSC2 related ACM.

The novel αB-crystallin (CRYAB) mutation p.D109G causes restrictive cardiomyopathy.

Restrictive cardiomyopathy (RCM) is a rare heart disease characterized by diastolic dysfunction and atrial enlargement. The genetic etiology of RCM is not completely known. We identified by a next-generation sequencing panel the novel CRYAB missense mutation c.326A>G, p.D109G in a small family with RCM in combination with skeletal myopathy with an early onset of the disease. CRYAB encodes αB-crystallin, a member of the small heat shock protein family, which is highly expressed in cardiac and skeletal muscle. In addition to in silico prediction analysis, our structural analysis of explanted myocardial tissue of a mutation carrier as well as in vitro cell transfection experiments revealed abnormal protein aggregation of mutant αB-crystallin and desmin, supporting the deleterious effect of this novel mutation. In conclusion, CRYAB appears to be a novel RCM gene, which might have relevance for the molecular diagnosis and the genetic counseling of further affected families in the future.

Noninvasive coronary angiography focusing on calcification: multislice computed tomography compared with magnetic resonance imaging.

OBJECTIVE: Calcification is a principal problem in noninvasive coronary angiography (CA) performed with multislice computed tomography (MSCT). Magnetic resonance imaging (MRI) supposedly neglects calcium. We compared both modalities. METHODS: Sixty-eight patients admitted for CA underwent MSCT- and MRI-based noninvasive CA the day before. Stenosis detection (>or=50%) was visually performed and validated by quantitative CA. RESULTS: The patient-based overall sensitivity, specificity, positive predictive value, and negative predictive value were 96.2%, 95.2%, 92.6%, and 97.6% for MSCT versus 69.2%, 64.3, 54.5%, 64.3%, and 77.1% for MRI, respectively. The segment-based overall results were 74.7%, 97.8%, 75.7%, and 97.6% for MSCT versus 40%, 93.8%, 37.5%, and 94.4% for MRI, respectively. Investigating the impact of coronary calcifications in the patient group with a volume score of 300 microL or greater resulted in 100%, 80%, 92.3%, and 100% for MSCT versus 70.8%, 86.7%, 89.5%, and 65% for MRI, respectively. The segment group with considerable hardening artifacts resulted in 85.3%, 83.9%, 76.3%, and 90.4% for MSCT versus 52.9%, 92.9%, 81.8%, and 76.5% for MRI, respectively. CONCLUSIONS: There are no major advantages of MRI in cases of advanced coronary calcification.

Stratification for noninvasive coronary angiography: patient preselection considering atypical angina pectoris, conventional cardiovascular risk assessment, and calcium scoring.

BACKGROUND: Noninvasive coronary angiography (NCA) is recommended to be applied as a filter before invasive coronary angiography in patients with intermediate cardiovascular risk. DESIGN: In this prospective single-center study, we validated multislice computed tomography (MSCT) and magnetic resonance imaging (MRI)-based NCA by primarily selecting patients with atypical angina pectoris (AAP). METHODS: In 68 patients (63.6+/-11.4 years) with AAP, the Prospective Cardiovascular Muenster Study score and the Agatston score equivalent (ASE; calcium score) were initially determined for cardiovascular risk assessment. Subsequently, MSCT and MRI-based NCA were performed followed by quantitative invasive coronary angiography for validation. All tests were finally analyzed. RESULTS: CAD (prevalence 38.2%) was diagnosed in 67.7% of patients at high, 61.5% at intermediate, and 37.8% at low cardiovascular risk according to the Prospective Cardiovascular Muenster Study. CAD was diagnosed in 88.2% of patients with an ASE >or=75th percentile and in 90.9% with an ASE >or=90th percentile. With regard to NCA, patient-based analysis resulted in a sensitivity of 96.2% for MSCT versus 69.2% for MRI, in a specificity of 95.2 versus 64.3%, in a positive predictive value of 97.6 versus 77.1%, in a negative predictive value of 92.6 versus 54.5%, and a diagnostic accuracy of 95.6 versus 66.2% (P<0.05). CONCLUSION: In a patient group with a heterogeneous cardiovascular risk, primarily considering AAP allows for effective patient preselection for NCA. This may be optimized by precluding patients with an ASE >or=75th percentile. MSCT rather than MRI may then effectively be involved.

Ultrafast time-resolved contrast-enhanced 3D pulmonary venous cardiovascular magnetic resonance angiography using SENSE combined with CENTRA-keyhole.

PURPOSE: To evaluate the diagnostic benefit of time-resolved CENTRA-keyhole contrast-enhanced cardiovascular magnetic resonance angiography (CE-CMRA) for improving arterial-venous separation of pulmonary vessels. METHODS: Twenty-three patients (18 males; age = 58 +/- 11y) after radiofrequency pulmonary vein isolation to treat atrial fibrillation were examined using CENTRA-keyhole based multi-phase 3D CE-CMRA yielding 6 near-isotropic 3D datasets every 1.6 s (50-60 coronal partitions, 1.4 x 1.4 x 1.3 mm, SENSE-factor 3). Results were compared with conventional non-keyhole CE-CMRA (identical parameters, SENSE-factor 2). RESULTS: Data acquisition was accelerated by a speedup factor of approximately 9 compared with the reference CE-CMRA (SENSE 1.5*, keyhole 6*). No pulmonary venous stenoses were detected by either method, overall pulmonary venous diameters were 17.1 +/- 3.6 mm. Applying Bland-Altman analysis, vessel diameters differed by a mean of 0.1 mm + 2.1 mm/-2.0 mm (mean +/- 2 SD), indicating close agreement between both techniques. Interobserver variability was higher for CENTRA-keyhole (mean = 0.1 mm; mean +/- 2 SD: +2.5 mm/-2.3 mm) compared to conventional technique (0.0 mm; +1.6 mm/-1.5 mm), corresponding to a percentual deviation (mean +/- 2 SD) of the mean diameter of approximately +/- 15% (keyhole CE-CMRA) and +/- 10% (conventional CE-CMRA), respectively. Using keyhole-based time-resolved CE-CMRA, the contrast between pulmonary veins versus aorta/pulmonary artery was significantly increased (p < 0.05), which improved vessel depiction. In 12 cases, the contrast bolus arrival was delayed in one of the pulmonary veins by 1 dynamic frame (= 1.6 seconds); in 7 cases by 2 frames (= 3.2 seconds) and in 1 subject by 3 frames (= 4.8 seconds). The bolus usually appeared first in the upper right pulmonary vein whereas a delay occurred most often in the lower left pulmonary vein. CONCLUSIONS: Conventional CE-CMRA may be advantageous for accurate vessel size measures as evidenced by superior interobserver reproducibility in this study. Multi-dynamic CE-CMRA using CENTRA-keyhole with SENSE, however, allows for improved arterio-venous separation of pulmonary vessels and additional dynamical information on pulmonary venous perfusion, while maintaining high spatial resolution. Exact bolus timing is no longer needed.

Flow volume and shunt quantification in pediatric congenital heart disease by real-time magnetic resonance velocity mapping: a validation study.

BACKGROUND: Flow quantification in real time by phase-contrast MRI (PC-MRI) may provide unique hemodynamic information in congenital heart disease, but available techniques have important limitations. We sought to validate a novel real-time magnetic resonance flow sequence in children. METHODS AND RESULTS: In 14 pediatric patients (mean age 5.2+/-2.0 years) with cardiac left-to-right shunt, pulmonary (Q(p)) and aortic (Q(s)) flow rates were determined by nontriggered free-breathing real-time PC-MRI with single-shot echo-planar imaging combined with sensitivity encoding, which yielded 25 phase images per second at 2.7x2.7-mm in-plane resolution (field of view 30x34 cm2). Over a 9.5-second period that included 2 to 5 respiratory cycles, 16.6+/-2.6 subsequent stroke volumes (range 13 to 22) were acquired in each vessel. Results were compared with conventional retrospectively ECG-gated PC-MRI. Mean Q(p)/Q(s) by conventional PC-MRI was 1.91+/-0.64, and it was 1.94+/-0.68 (mean+/-SD) by real-time PC-MRI. For blood flow rate through pulmonary artery and aorta, we found differences of 2% to 3% (Bland-Altman analysis), with lower limits of agreement of -11% to -13% (mean-2 SD) and upper limits of 18% to 19% (mean+2 SD), which demonstrated good agreement between both methods. Mean difference for Q(p)/Q(s) was 1%, with limits of agreement ranging between -18% and 22% (mean+/-2 SD). High repeatability but some flow overestimation was observed in vitro (pulsatile flow phantom) with real-time PC-MRI, whereas conventional PC-MRI was accurate. Beat-to-beat stroke-volume variation was 6.1+/-2.3% in vivo and 3.7+/-0.3% in vitro. CONCLUSIONS: Beat-to-beat quantification of pulmonary and aortic flows and hence left-to-right shunt within a few seconds is reliable by nontriggered real-time PC-MRI with echo-planar imaging and sensitivity encoding. Good spatial/temporal resolution and a large field of view may render the sequence valuable for multiple applications in congenital heart disease.