Cardiac structure discontinuities revealed by ex-vivo microstructural characterization. A focus on the basal inferoseptal left ventricle region.

BACKGROUND: While the microstructure of the left ventricle (LV) has been largely described, only a few studies investigated the right ventricular insertion point (RVIP). It was accepted that the aggregate cardiomyocytes organization was much more complex due to the intersection of the ventricular cavities but a precise structural characterization in the human heart was lacking even if clinical phenotypes related to right ventricular wall stress or arrhythmia were observed in this region. METHODS: MRI-derived anatomical imaging (150 µm3) and diffusion tensor imaging (600 µm3) were performed in large mammalian whole hearts (human: N = 5, sheep: N = 5). Fractional anisotropy, aggregate cardiomyocytes orientations and tractography were compared within both species. Aggregate cardiomyocytes orientation on one ex-vivo sheep whole heart was then computed using structure tensor imaging (STI) from 21 µm isotropic acquisition acquired with micro computed tomography (MicroCT) imaging. Macroscopic and histological examination were performed. Lastly, experimental cardiomyocytes orientation distribution was then compared to the usual rule-based model using electrophysiological (EP) modeling. Electrical activity was modeled with the monodomain formulation. RESULTS: The RVIP at the level of the inferior ventricular septum presented a unique arrangement of aggregate cardiomyocytes. An abrupt, mid-myocardial change in cardiomyocytes orientation was observed, delimiting a triangle-shaped region, present in both sheep and human hearts. FA's histogram distribution (mean ± std: 0.29 ± 0.06) of the identified region as well as the main dimension (22.2 mm ± 5.6 mm) was found homogeneous across samples and species. Averaged volume is 0.34 cm3 ± 0.15 cm3. Both local activation time (LAT) and morphology of pseudo-ECGs were strongly impacted with delayed LAT and change in peak-to-peak amplitude in the simulated wedge model. CONCLUSION: The study was the first to describe the 3D cardiomyocytes architecture of the basal inferoseptal left ventricle region in human hearts and identify the presence of a well-organized aggregate cardiomyocytes arrangement and cardiac structural discontinuities. The results might offer a better appreciation of clinical phenotypes like RVIP-late gadolinium enhancement or uncommon idiopathic ventricular arrhythmias (VA) originating from this region.

Comparison of survival for cardiac resynchronization therapy in atrial fibrillation patients with or without atrio-ventricular junction ablation and patients in sinus rhythm: a systematic review and network meta-analysis.

Cardiac resynchronization therapy (CRT) has been established to improve prognosis for patients with heart failure and SR. Whether the benefit observed with CRT on survival was similar in AF patients receiving atrio-ventricular junction ablation (AVJA) or not and patients in SR remains uncertain. The primary purpose of this study was to comprehensively evaluate the impact of CRT on the outcome of survival in atrial fibrillation (AF) patients with or without AVJA and patients in sinus rhythm (SR). Medline, Embase, and the Cochrane Library were searched for inception through June 31, 2018. Two reviewers independently evaluated and extracted data from 4 studies, including a total of 7896 CRT recipients, composed of 554 AF with AVJA (CRT+AF+AVJA), 1071 AF without AVJA (CRT+AF-AVJA), and 6244 SR (CRT+SR). The benefit on survival was comparable between CRT+AF+AVJA and CRT+SR (HR = 1.00; 95% CI, 0.73-1.40). CRT+AF+AVJA and CRT+SR both were associated with significantly higher survival compared with CRT+AF-AVJA, with hazard ratio of 0.64 (95% CI, 0.46-0.91) and 0.63 (95% CI, 0.53-0.75), respectively. The survival benefit was similar for patients with CRT+AF+AVJA and CRT+SR, while it was 36-37% high as compared to CRT+AF-AVJA. Whether aggressive intervention with AVJA in AF should be routinely combined with CRT despite rate-slowing drug treatment is helpful deserves further studies.

Internal circular suture annuloplasty for aortic valve repair.

Stabilizing the aorto-ventricular junction is integral in aortic valve repair. We report our technique of internal circular suture annuloplasty. We used a continuous horizontal mattress suture of a single thick expanded polytetrafluoroethylene suture (CV-3). We put 4 stitches per sinus, so the suture was below the cusp attachment line at the nadirs and passed through the interleaflet triangle at the upper aorto-ventricular junction level. The suture was reinforced with pericardial pledgets on both sides of each commissure. We used this technique in 12 patients. The diameter of aorto-ventricular junction was reduced from 25 ± 2 mm to 22 ± 1 mm (n = 11) and was 22 ± 1 mm at the latest follow-up (4-74 months, median 41, n = 10). In 2 patients with large aorto-ventricular junction (27 mm or more), expected annular reduction was not achieved. Our modified technique is simple and seems durable. It may be useful for mild annular dilatation.