Abstract 16544: Focal Fibrosis Predicts Monomorphic VT but Not Polymorphic VT or VF in Nonischemic Dilated Cardiomyopathy

Purpose: This study aimed to analyze the effect of focal myocardial fibrosis, assessed by late gadolinium enhancement MRI (LGE-MRI), on the occurrence and type of ventricular arrhythmia in patients with nonischemic dilated cardiomyopathy (NIDCM). Methods: We included consecutive patients with NIDCM who underwent LGE-MRI before implantable cardioverter-defibrillator (ICD) implantation at two centers. LGE was defined by signal intensity ≥35% of maximal signal intensity and subdivided into core and border zone (≥50% and 35-50% of maximal signal intensity, respectively), and according to (non)basal location and transmurality. ICD recordings and 12-lead ECGs were reviewed to determine the occurrence and type of ventricular arrhythmia during follow-up. Results: Of all 87 patients (62% male, age 56±13 years, LVEF 29±12%), 55 patients (63%) had LGE (median 6.3g, IQR 0.0-13.8g). During a median follow-up of 45 months (interquartile range, 23-67), monomorphic VT occurred in 18 (21%) patients, and polymorphic VT/VF in 10 (11%). LGE predicted monomorphic VT (Log-rank, p<0.001), but not polymorphic VT/VF (Log-rank, p=0.40). The optimal cut-off value for LGE to predict monomorphic VT was 7.2 grams (area under curve 0.84). Features associated with high risk for monomorphic VT were core extent, location in basal segments and area with 51-75% transmurality. Conclusion: Focal fibrosis assessed by LGE-MRI predicts monomorphic VT, but not polymorphic VT/VF. The risk for monomorphic VT was particularly high when the LGE extent was ≥7.2 grams. The differences in underlying substrate and associated types of arrhythmia may have important implications for risk stratification and therapeutic interventions in patients with NIDCM.

The SA/rABC technique: a new ABC procedure for detection of antigens at increased sensitivity.

Since its introduction, the avidin-biotin-peroxidase (ABC) complex has become an invaluable detection system for a wide variety of bioanalytical applications. In these techniques, avidin and biotin-peroxidase are mixed at a pre-determined ratio so that the soluble ABC complex retains biotin binding sites. Consequently, the complex contains an excess of avidin over biotinylated peroxidase residues. On theoretical considerations, however, an ABC complex designed for maximal signal intensity must consist of an excess of peroxidase over avidin molecules. Therefore, ABC complexes with reversed molar ratios of biotinylated peroxidase to avidin (rABC complexes) were prepared and an intermediate streptavidin step was introduced to bind the rABC complexes to biotinylated IgG molecules. The signal generating power of this new streptavidin-rABC sequence proved superior to that of the conventional ABC technique in ELISA assays and in immunostaining of tissue sections.