P1594Ventricular fibrosis spatial distribution and quantity is a key mechanistic determinant of ventricular fibrillation mechanisms

Background

Ventricular fibrosis is known to play a critical role in initiation and maintenance of ventricular fibrillation (VF). Post myocardial infarction the quantity of fibrosis negatively correlates with survival. There is a lack of data on how the quantity and degree of fibrosis influences the mechanisms of VF itself. VF mechanisms remain debated, there are data to support both critical areas sustaining rotational drivers (RDs) and the contrary hypothesis of disorganized myocardial activation driving VF.

Purpose

We hypothesized that the underlying mechanism of VF is influenced by the spatial distribution and quantity of ventricular fibrosis.

Methods

Thirty-five Sprague-Dawley rats underwent permanent left anterior descending (LAD) ligation (n=11), 20mins LAD territory ischaemia-reperfusion (n=13) or in-vivo angiotensin infusion (500ng/kg/min, n=11) to generate compact (CF), patchy (PF) and diffuse fibrosis (DF) models respectively. After a 4-week maturation period, the hearts were explanted, Langendorff perfused and VF induced with burst pacing and 30μM pinacidil. Fibrillation dynamics were quantified using phase analysis, phase singularity (PS) tracking and our novel method of global fibrillation organisation quantification, frequency dominance index (FDI), which is a power ratio of highest amplitude dominant frequency in the frequency spectrum.

Results

Ventricular fibrosis for each group was characterized and quantified (CF: 22.3±3.2%, PF: 18.4±4.2%, DF: 5.8±1.3%, p=0.046). VF was driven predominantly by disorganised activity in CF, PSs were detected 26±7% of time comparative to 51.2±4% in DF and 69.5±8% in PF group (p=0.001). PF stabilised RDs, average maximum rotations for a single RD in PF were 31.6±7.1 comparative to 12.5±1.7 in DF and 6.4±1.1 in CF, p<0.001. The average maximum duration for a single RDs was significantly longer in PF (PF: 1231±365ms, DF: 568±68ms, CF: 363±41ms, p=0.014). Similarly, average rotations per RD were greater in the PF group (PF: 4.5±0.7, DF: 3.3±0.2, CF: 2.41±0.3 rotations, p=0.013). Total number of RDs/second were much greater with PF (PF: 12.4±2.0, DF: 5.4±0.8, CF: 3.1±1.1, p<0.001). VF organisation measured by FDI was higher in PF (PF: 0.61±0.07, DF: 0.47±0.04, CF: 0.33±0.03, p=0.004). RDs in DF showed a greater degree of meander comparative to PF (DF: 12.6±1.4 vs PF: 9.3±0.8 pixels, p=0.024).

Conclusion

VF mechanisms occur along a spectrum between organised activity sustained by discrete drivers and disorganised myocardial activation. The underlying VF mechanism can differ significantly dependent on the quantity and pattern of fibrosis. Patchy fibrosis stabilises RDs with localization to discrete areas and sustains an organised form of VF comparative to CF where VF is largely disorganised. Characterising the degree and pattern of fibrosis in patient groups vulnerable to VF might be beneficial in identifying patients with suitable targets for ablation.

Acknowledgement/Funding

BHF Programme Grant PG/16/17/32069

Abstract P3-08-08: Preferences for breast cancer risk reduction among BRCA1 and BRCA2 mutation carriers: A discrete choice experiment

This abstract was withdrawn by the authors.

Abstract P2-09-09: Risk-reducing surgery and cancer-related distress among female BRCA1 and BRCA2 mutation carriers

Background: Distress levels among female BRCA1 and BRCA2 mutation carriers can be similar to levels reported among breast cancer patients. However, there is a lack of data on long-term psychosocial functioning, and it is not known if uptake of risk-reducing surgery influences long-term cancer related distress in women with a BRCA mutation who are unaffected with cancer. The objective of this study was to evaluate long-term cancer-related distress in women with a BRCA mutation, and to evaluate predictors of distress, including uptake of cancer risk reducing surgery.

Methods: Female BRCA1 or BRCA2 mutation carriers, ages 25-55, and without cancer were eligible to complete the survey online. A validated instrument, Impact of Events Scale (IES)-Revised (Horowitz 1979, Weis & Marmar 1995; 0-80 overall scale), was used to assess current levels of cancer risk-related psychological distress. Respondents were recruited through the Facing Our Risk of Cancer Empowered (FORCE) advocacy organization, which includes women at high risk of breast cancer. This interim analysis is part of a larger multi-center patient preference study of BRCA mutation carriers designed to assess women's willingness to adopt hypothetical treatments to prevent breast cancer. Linear regression was used to evaluate predictors of IES distress levels.

Results: Between January and April 2015, 259 women completed the survey. The mean age of the participants was 41 years, and the mean time since receipt of genetic test results was 3.5 years (range 0-16; median 2 years). One hundred thirty-six (52%) women elected for prophylactic bilateral mastectomy (PBM), 139 (54%) elected for bilateral salpingo oophorectomy (BSO) (93 [36%] women had both surgeries), and 77 (30%) had not undergone risk-reducing surgery. The mean total IES score was 15.1 (range 0-72; median 11). Overall, 54 (21%) women reported moderate or severe cancer-related distress, and those who had undergone risk-reducing surgery reported lower perceived risk of developing breast cancer. Results to date indicate that shorter time since notification of mutation status, not having PBM (with or without BSO) (table), and not completing post-secondary education were independent predictors of higher IES distress scores.

IES severityNo prophylactic surgeryPBM onlyBSO onlyPBM and BSOn (%)77434693Subclinical27 (35)23 (54)16 (35)44 (47)Mild26 (34)13 (30)21 (46)35 (38)Moderate18 (23)5 (12)6 (13)11 (12)Severe6 (8)2 (5)3 (6)3 (3)

Conclusions: This study measured cancer-related distress in a large population of women with BRCA mutations who participate in the FORCE online support community. Higher levels of distress were associated with not having PBM and more recent genetic test disclosure. These findings are specific to a more informed community of women with high levels of understanding of cancer risk than may be seen in the clinical setting.

Citation Format: Liede A, Fairchild A, Friedman S, Amelio J, Hallett DC, Mansfield CA, Metcalfe KA. Risk-reducing surgery and cancer-related distress among female BRCA1 and BRCA2 mutation carriers. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-09-09.