P3108Microcirculation injury is involved in anthracycline-induced cardiac toxicity

Background/Introduction

Cardiotoxicity (CT) is a major concern for cancer patients receiving anthracyclines. While the effect of anthracyclines on cardiomyocytes is well established, its impact on myocardial microcirculation has not been characterized.

Purpose

To evaluate the effect of low and high cumulative doses of doxorubicin (doxo) on anatomical and functional vasculature status evaluated by serial invasive Coronary Flow Reserve (CFR) and Cardiac Magnetic Resonance (CMR)-based quantitative perfusion in a large animal model.

Methods

Large-white male pigs (n=15, 30 kg) were distributed in 2 doxo regimes: Group 1) high cumulative dose (5 biweekly intracoronary (i.c) injections of 0.45 mg/kg of doxo) followed-up until week 16 (a time when severe left ventricular systolic dysfunction is present) and then sacrificed (N=5); Group 2) low cumulative dose of doxo (3 biweekly i.c. doses) followed-up until week 16 and then sacrificed (N=5)). Group 3) pigs sacrificed at 6 weeks (2 weeks after third doxo dose), N=5. Invasive catheter-based CFR was evaluated after i.c papaverine (0.5 mg/kg) while CMR quantitative rest perfusion maps were obtained after intravenous injection of gadolinium. CFR and CMR were performed before doxo, and at 0, 2, 4, 6 and 16 weeks thereafter. Cardiac vessels were evaluated ex vivo with trichrome staining. Statistical analysis was performed using one-way ANOVA with multiple pairwise comparisons (vs. baseline) and Bonferroni corrected p-value.

Results

CFR and CMR-quantitative myocardial perfusion were non-significantly reduced after 3 doxo doses despite myocardial vasculature was overtly injured on histology at this timepoint. Animals receiving 5 doxo doses suffered a progressive deterioration of CFR and CMR-perfusion until week 16 (1.41±0.23 vs 3.71±0.94 at baseline [p=0.014] and 65.4±18.2 ml/100g/min vs 154.9±56.3 ml/100g/min at baseline [p=0.046], respectively). At 16 weeks histology revealed extensive microvascular damage with media layer involvement and perivascular fibrosis. Pigs receiving 3 doxo doses showed less pronounced CFR reduction on long-term follow-up (3.13±0.82 vs 3.69±1.57 at baseline [p>0.05] but overt CMR-perfusion reduction (138.3±11.9 vs 197.8±37.1 at baseline [p=0.045]). On histology, damage of vasculature including arterioles was evidenced to a lesser extent than in the high cumulative doxo dose group with mild microvascular disruption and smooth muscle vacuolization.

Conclusions

Doxorubicin results in a progressive damage of the myocardial microcirculation. Even low cumulative doxo doses (resulting in no overt left ventricular dysfunction) results in vascular damage. The microcirculation status may serve as an early marker of doxorubicin cardiotoxicity.

P5999Heart failure rescue by high fat diet in a porcine model of hibernated myocardium

Background

Extensive coronary artery disease without revascularization options results in ischemic hibernated myocardium and ultimately heart failure (HF). A metabolic reprogramming of the heart characterized by a shift from fatty acids (FFA) to glucose as the preferential metabolic substrate is frequent in HF and hibernated myocardium. Previous studies in mouse models of HF have shown that high fat diet (HFD) is able to reverse the metabolic reprogramming of the heart and improve cardiac function. Here we used a translational large animal model of ischemic HF evaluated by state-of-the-art imaging modalities

Methods

IHM was generated in Yucatan minipigs (N=50) by progressive stenosis of the proximal left anterior descending (LAD) after surgical insertion of a casein ameroid around the artery. Pigs underwent a serial multimodality imaging study including magnetic resonance imaging (MRI), multi-tracer PET/CT (18FDG & 14(R,S)-[18F]Fluoro-6-thia-heptadecanoic acid (18F-FTHA) 19F-palmitate in-house synthetized), and invasive coronary angiography (ICA). Once hibernated myocardium with metabolic switch was documented (complete occlusion of LAD, LVEF<50% on MRI, viable myocardium with dobutamine/MRI- evaluated contractile reserve, and metabolic substrate utilization shift towards glucose on PET/CT), animals were randomized to HFD or regular diet for 3 months

Results

The first part of the study was dedicated to establish the model in 42 pigs. Pigs were followed-up for 170±24 days with monthly ICA, MRI and PET/CT. Severe LAD stenosis was documented in all pigs 3–4 weeks after surgery. Mortality during follow-up was 57% (n=24) (15 peri-procedure, 2 between day 1 and 7, seven between day 7 and 45). Among those surviving beyond the sixth week, 90% (16/18) developed hibernated myocardium (mean LVEF 36±10%, absence of transmural delayed enhancement, contractile reserve and metabolic switch on PET/CT).

In the second part of the study, 5 long-term survivors were allocated to receive HFD (20% extra lard), while 3 pigs served as controls. Mean LVEF before HFD initiation was 35±8%, and 36±5% in controls. Three months HFD was associated with a LVEF improvement in all treated animals (mean LVEF at the end of follow-up was 45±9%). Control animals on regular diet did not show any change in LVEF (35±5% at the end of follow-up)

Conclusions

We present a large animal model of HF due hibernated myocardium by placing an ameroid around the LAD. Mortality of this model is high (approx. 55%) but long-term survivors resemble all features seen in patients: LAD progressive stenosis with final occlusion but viable myocardium, LVEF deterioration and metabolic switch

Feeding pigs with HFD to force cardiac reutilization of FFA, results in a consistent and large LVEF improvement in all animals

Cardiac metabolic switch might be implicated in the pathogenesis of systolic dysfunction in hibernated myocardium and is a potential target for nutritional approaches

P6423Cardioprotective effect of metoprolol in myocardial ischemic/reperfusion injury: the role of total ischemic time

Background

Metoprolol administration before reperfusion has shown relevant cardioprotective effect in the AMI in preclinical setting. However, the translation to clinical arena has controversial results. The time at drug administration in the context of total duration of ischemia have been pointed as fundamental aspects to be studied.

Purpose

evaluate the cardioprotective effect of metoprolol administration regarding to the total time of ischemia, using a swine model of reperfused AMI.

Methods

50 pigs were subjected to 3 temporary protocols of left anterior descending (LAD) coronary artery occlusion followed by reperfusion. 30 pigs undergoing 40 minutes of ischemia (T40) were randomized 2:1 to intravenous placebo or metoprolol administrated 20 minutes after LAD occlusion.10 pigs undergoing 20 minutes of ischemia 20 (T20) and 10 pig undergoing 60 minutes of ischemia 60 (T60) were randomized 1:1 to intravenous placebo or metoprolol. Before reperfusion a CT study was performed to stablish the area at risk (AAR). CMR was performed at 7 and 45 days after AMI.

Results

48 subjects comprised the 7-day CMR follow-up (1 dead in the metoprolol T40,1 dead in the placebo T40) while 41 subjects comprised the 45-day CMR follow-up (5 deceases in the placebo T40 group, and 2 in the placebo T60 group). AAR was similar among groups (Table 1, Panel B). At 7-day follow-up, IS washigher in the placebo groups as compared to the metoprolol groups, but only reach significant difference in the T40 (29,67% vs. 22,85%, p=0.04, Table 1, Panel A). LVEF measured at 45-day follow-up was higher in the metoprolol groups vs the control groups, but the differences were statistically significance in the T40 (32,76% vs 39,68% p=0.04, Panel C).

Table 1 20 mins. Ischemia (T20) 40 mins. Ischemia (T40) 60 mins. Ischemia (T60) P PLACEBO METOPROL P value PLACEBO METOPROL P value PLACEBO METOPROL P value AAR 32 (28.14–37.89) 33.41 (28.12–38.32) 0.82 32.99 (29.25–35.83) 31.42 (26.94–37.83) 0.72 33.28 (29.68–41.14) 33.93 (28.17–40.69) 0.80 0.98 IS 1.96 (0.92–3.61) 0 (0–0.65) 0.063 29.67 (27.23–35.35) 22.85 (14.53–28.10) 0.042 36.21 (33.55–40.91) 33.78 (39.36–35.39) 0.31 <0.001 LVEF 54.36 (49.75–58.97) 55.34 (53.14–60.88) 0.66 32.76 (26.91–36.10) 39.68 (35.45–45.28) 0.023 26.13 (22.40–31.25) 32.99 (31.32–35.19) 0.071 <0.001 Values are median (interquartile range). Bold indicates statistical significance. AAR = Area at Risk (% of Left ventricular). IS = Infartc Size (% of Left ventricular). LVEF = Left ventricular ejection fraction (%).

Conclusions

Metoprolol administrated early before reperfusion reduced IS and improved medium-term LVEF compared to placebo. But only T40 receiving metoprolol shownsignificant protection vs placebo. These findings suggest a relevant effect of metoprolol ischemic/reperfusion injury, but depending on the total ischemic time, establishing a potential temporary cardioprotection opportunity window.

Traumatic Tracheal Tear Successfully Treated after Remote Area Retrieval

A 44-year-old man injured in a motor vehicle accident in rural Australia was resuscitated at a local hospital 9 hours later. Bronchoscopy revealed a large tracheal tear. After transfer to the regional cardiothoracic center, surgery was performed under cardiopulmonary bypass 18 hours after the injury was sustained. The patient required surgical tracheostomy as well as ventilatory and inotropic support. There were no postoperative complications and he was discharged after 27 days.

Selective transmission of R5-tropic HIV type 1 from dendritic cells to resting CD4+ T cells

In an in vitro coculture model of monocyte-derived, cultured human dendritic cells (DC) with autologous CD4(+) resting T cells, CCR5 (R5)-tropic strains of HIV-1, but not CXCR4 (X4)-tropic strains, were transmitted to resting CD4+ T cells, leading to prolific viral output, although DC were susceptible to infection with either strain. Macrophages, which were also infectable with either R5- or X4-tropic strains, did not transmit infection to CD4+ cells. Highly productive HIV infection in this model appeared to be a consequence of heterokaryotic syncytium formation between infected DC and T cells since syncytia formation developed only in R5-infected DC/CD4+ cocultures. These results suggested that the unique microenvironment derived from the fusion between the infected DC and CD4+ cell was highly permissive and selective for replication of R5-tropic viruses. The apparent selectivity for R5-tropic strains in such syncytia was attributable neither to differential DC-mediated activation nor to selective modulation of induction of alpha- or beta-chemokines in the infected DC. This model of HIV replication may provide useful insights into in vitro correlates of HIV pathogenicity.

Lasting effects of transient postinoculation tenofovir [9-R-(2-Phosphonomethoxypropyl)adenine] treatment on SHIV(KU2) infection of rhesus macaques

SHIV(KU2) replicates to high levels in inoculated macaques and reproducibly causes an acute depletion of CD4(+) T cells. We evaluated the ability of treatment with the antiretroviral drug 9-R-(2-phosphonomethoxypropyl)adenine (PMPA; tenofovir), begun 7 days postinoculation, to inhibit viral replication and associated pathogenesis. Highly productive infection (plasma viral RNA > 10(6) copy eq/mL) was present and CD4 depletion had started when treatment was initiated. PMPA treatment was associated with a rapid decline in plasma viral RNA to undetectable levels, with parallel decreases in the infectivity of plasma and infectious cells in PBMCs and CSF and stabilization of CD4(+)T-cell levels. Viral dynamics parameters were calculated for the initial phase of exponential viral replication and the treatment-related decline in plasma viremia. Following cessation of treatment after 12 weeks, plasma viral RNA was detectable intermittently at low levels, and spliced viral transcripts were detected in lymph nodes. Although treatment was begun after viral dissemination, high viremia, and CD4 decreases had occurred, following withdrawal of PMPA, CD4(+) T-cell counts normalized and stabilized in the normal range, despite persistent low-level infection. No PMPA-resistance mutations were detected. These results validate the similar viral replicative dynamics of SHIV(KU2) and HIV and SIV, and also underscore the potential for long-term modulation of viral replication patterns and clinical course by perturbation of primary infection.