Electrophysiological effects of adipose graft transposition procedure (AGTP) on the post-myocardial infarction scar: A multimodal characterization of arrhythmogenic substrate

Objective

To assess the arrhythmic safety profile of the adipose graft transposition procedure (AGTP) and its electrophysiological effects on post-myocardial infarction (MI) scar.

Background

Myocardial repair is a promising treatment for patients with MI. The AGTP is a cardiac reparative therapy that reduces infarct size and improves cardiac function. The impact of AGTP on arrhythmogenesis has not been addressed.

Methods

MI was induced in 20 swine. Contrast-enhanced magnetic resonance (ce-MRI), electrophysiological study (EPS), and left-ventricular endocardial high-density mapping were performed 15 days post-MI. Animals were randomized 1:1 to AGTP or sham-surgery group and monitored with ECG-Holter. Repeat EPS, endocardial mapping, and ce-MRI were performed 30 days post-intervention. Myocardial SERCA2, Connexin-43 (Cx43), Ryanodine receptor-2 (RyR2), and cardiac troponin-I (cTnI) gene and protein expression were evaluated.

Results

The AGTP group showed a significant reduction of the total infarct scar, border zone and dense scar mass by ce-MRI (p = 0.04), and a decreased total scar and border zone area in bipolar voltage mapping (p < 0.001). AGTP treatment significantly reduced the area of very-slow conduction velocity (<0.2 m/s) (p = 0.002), the number of deceleration zones (p = 0.029), and the area of fractionated electrograms (p = 0.005). No differences were detected in number of induced or spontaneous ventricular arrhythmias at EPS and Holter-monitoring. SERCA2, Cx43, and RyR2 gene expression were decreased in the infarct core of AGTP-treated animals (p = 0.021, p = 0.018, p = 0.051, respectively).

Conclusion

AGTP is a safe reparative therapy in terms of arrhythmic risk and provides additional protective effect against adverse electrophysiological remodeling in ischemic heart disease.

Cardiac reparative therapy with adipose graft transposition procedure (AGTP) improves electrophysiological remodeling of chronic myocardial infarction

Background

Cardiac regeneration is a promising therapeutic option for patients with prior myocardial infarction (MI). Adipose graft transposition procedure (AGTP) is a cardiac reparative therapy consisting of the transposition of a vascularized adipose flap from the autologous pericardium over the epicardial scar area, which has shown to reduce the infarct size and improve the left ventricular function.

Purpose

To assess the impact of the AGTP on the electrophysiological remodeling of the post-MI scar by means of electrophysiological study (EPS), high density (HD) mapping, and 3D contrast-enhanced MRI (ceMRI).

Methods

A lateral MI was induced in 14 Landrace X Large White pigs by coil deployment at the first marginal branch of the circumflex artery. A 3D ceMRI, EPS and endocardial HD mapping were performed 2 (baseline) and 6 weeks post-MI (30 day post-treatment). Subjects were randomized to AGTP (n=8) or sham surgery (n=6) following baseline tests. Voltage and activation maps were blindly analyzed off-line with self-customized ParaView-based software. ceMRI was post-processed with ADAS3D. Conventional bipolar and unipolar voltage cut-offs were used (0.5–1.5mV and 6.7mV, respectively). Conduction velocity (CV) was determined for every pair of contiguous points. Areas of CV were quantified for every 0.2m/s steps (&lt;0.2 - 4 m/s).

Results

At follow-up, and compared to the sham group, the AGTP group showed a significant reduction of the border zone area in both bipolar voltage mapping (−18±50% vs +10±144%, p=0.043) and ceMRI (−2.0±1.7 vs +1.1±2.8g; p=0.047), as well as a reduction in dense scar mass by ceMRI (−1.1±0.7g vs. +0.6±0.9 g, p=0.001). The AGTP group had a significant reduction of the size of very-slow CV areas (&lt;0.2 m/s), compared to the sham group (−3.5±3.4 vs. +1.5±3.8 mm2, p=0.022), without differences in other CV ranges. EPS did not induce ventricular tachycardia in any subject at baseline, and only in 1 of the sham group at the follow-up.

Conclusions

Cardiac reparative therapy with AGTP of post-MI scar reduced the size of border zone tissue and very-slow conduction zones and could provide a protective effect against arrhythmic events in ischemic heart disease.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): FIS grant - Instituto de Salud Carlos III

Effect of adipose graft transposition procedure (AGTP) on the ischemic arrhythmogenic substrate: an MRI study in a swine model of chronic myocardial infraction

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Instituto de Salud Carlos III

BACKGROUND

Cardiac regenerative therapy is a promising treatment for patients with myocardial infarction (MI) and heart failure. Nevertheless, previous ex-vivo studies have raised concern on the potential increased risk of arrhythmic events following certain cell therapies. Adipose graft transposition procedure (AGTP) is a cardiac reparative therapy consisting in transposing a vascularized adipose flap from the autologous pericardium and placing it over the epicardial scar area and has demonstrated to reduce infarct size and improve the left ventricular ejection fraction in preclinical and human studies.

PURPOSE

To assess the effect of the AGTP on the post-MI scar composition and image-based ventricular tachycardia (VT) corridors detection by means of late gadolinium enhanced cardiac magnetic resonance (LGE-CMR).

METHODS

A left circumflex artery (first marginal branch) MI was induced in 9 Landrace X Large White Pigs by delivering 1-3 coils. Two weeks post-MI, all subjects underwent a 3 Tesla LGE-CMR and randomized to the AGTP or sham group. LGE-CMR was repeated 30 days post-treatment (6 weeks post-MI). The arrhythmogenic substrate was characterized with an advanced image post-processing tool (ADAS 3D) and included quantification of dense scar and border zone (BZ) mass and detection of ventricular tachycardia (VT) corridors (including corridor scar mass).

RESULTS

The overall scar mass did not differ between scans in the overall population (7.6 ± 3.5 g vs 7.5 ± 2.2 g in the baseline and post-treatment scans, respectively; p = 0.9). Compared to the sham subjects, those receiving AGTP showed an absolute reduction of the total (-3.2 ± 1.4 g vs. +2.4 ± 1.7 g, p = 0.04) and dense scar (-0.9 ± 0.4 g vs. +0.7 ± 0.5 g, p = 0.03). BZ mass tended to decrease in the AGTP group (-2.2 vs 1.63 g; p = 0.06). The AGTP group showed a trend to reduce the number of VT corridors (-1 ± 0.7 vs. +0.4 ± 0.2, p = 0.078) and corridor scar mass (-0.3 ± 0.26 g vs. +0.1 ± 0.1 g, p = 0.11) (figure).

CONCLUSIONS

Cardiac reparative therapy of MI with AGTP reduced dense scar mass, compared to the increase observed in the sham group. The trend to reduce the BZ mass and the number/mass of VT corridors suggests a beneficial effect on the arrhythmic remodeling of the post-MI scar. Abstract Figure. Reduction in corridor"s number

Cardiac reparative therapy with adipose graft transposition procedure reduces slow conduction areas in a chronic myocardial infarction swine model

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Insituto de Salud Carlos III

BACKGROUND

Cardiac regenerative therapy is a promising treatment for patients with ischemic heart disease, but there are some concerns on the potential increased risk of arrhythmic events following specific cell therapies. Adipose graft transposition procedure (AGTP) is a cardiac reparative therapy consisting in transposing a vascularized adipose flap from the autologous pericardium and placing it over the epicardial scar area and has demonstrated to reduce infarct size and improve the left ventricular ejection fraction in preclinical and human studies. Specific electrophysiological properties of the scar, (i.e. slow conduction velocity (CV)) have been identified as key features of ventricular tachycardia (VT) isthmuses.

PURPOSE

To assess the effect of the AGTP on VT inducibility and the electrophysiological properties of the post-MI scar with ultra-high density (UHD) mapping.

METHODS

A left circumflex artery (first marginal branch) MI was induced in 10 Landrace X Large White pigs by delivering 1-3 coils. Two weeks post-MI, all subjects underwent baseline left ventricular endocardial UHD mapping during right ventricular pacing with 64-electrode basket mapping catheter, as well as electrophysiological study (EPS) to test for VT inducibility.  Following the mapping, subjects were allocated 1:1 to AGTP or sham group. UHD mapping and EPS were repeated 30 days post-treatment (6 weeks after MI). Voltage and activation maps were analyzed off-line with self-customized Paraview-based software. Voltage cut-offs of 1.5 and 0.5mV (bipolar) defined normal tissue, border zone (BZ) and dense scar, respectively, and 6.7mV for unipolar. Conduction velocity (CV) was determined for every pair of contiguous points and areas of similar CV were quantified for every 0.2m/s steps (for up to 4 m/s).

RESULTS

There were no differences between groups with regard of dense scar, BZ an low unipolar voltage areas. The AGTP group had a significant reduction of the size of slow CV (&lt;0.2 m/s) areas, compared to the sham group in whom it increased (-4.1 ± 1.7 vs. +2.4 ± 1.6 mm2, p = 0.028)(Figure). There were no differences in the size of other ranges of CV. EPS did not induce VT in any subject at baseline, and only in 1 of the sham group at the follow-up EPS.

CONCLUSIONS

Cardiac reparative therapy with AGTP of post-MI scar reduced the size of slow conduction areas and could provide a protective effect against arrhythmic events in ischemic heart disease. Abstract Figure.

Association between use of non-steroidal anti-inflammatory drugs (NSAIDs) and statins and the risk of cutaneous melanoma (CM): A case-control study

8500

Background: CM accounts for more than 77% of skin cancer deaths. Chemoprevention strategies have been hampered by the lack of supporting epidemiological data. Methods: A case control study examined the association between statins and NSAIDs use and CM in people over 40 years of age. A total of 400 histologically confirmed CM cases were recruited within 3 months from diagnosis between 3/04 and 12/06. Controls included 600 individuals without history of CM matched for age, gender and neighborhood in a ratio of 1:1.5. All completed a standardized telephone questionnaire that captured demographic characteristics, CM risk factors, and drug exposure history (length and frequency of use). Odds ratios were calculated with testing for statistical significance based on Chi square analysis. Results: To date, all 400 CM cases and 547 controls have been recruited. Interview results out of 387 cases (192 F/195 M) and 505 controls (254 F/251 M) were included for data analysis. Mean age was 58.4 and 58.5 years. The most significant CM risk factors included: red hair phenotype OR: 2.29, history of non-CM skin cancer OR: 2.28, family history of CM OR: 1.76, light complexion OR: 2.7, and history of more than 4 sunburns in childhood OR: 4.06. 100 cases vs. 190 of the controls had been exposed to statins OR 0.58 (CI:0.43–0.78); no greater protective effect was detected with increased duration of statin use (p=0.87 for heterogeneity of ORs for =5 vs. <5 yrs). 238 cases vs. 397 controls reported the use of NSAIDs, OR 0.44 (CI 0.32–0.59). 43 cases reported the use of aspirin-ASA for = 5 years vs. 92 controls OR: 0.37 (CI: 0.20–0.68). Similar results were observed with exposure to other NSAIDs with 38 cases reporting the use for = 5 years vs.109 controls, OR: 0.35 (CI: 0.24- 0.50). Conclusions: This study suggests that extended use of NSAIDs decreases the risk of CM development. Although any statin use demonstrated a decreased risk, the lack of an association between duration of use and protective effect raises questions about a true causal relation. Further analysis with respect to the CM subtype and specific exposure (by dose, and frequency of use) to these groups of drugs may lead to the design of CM chemopreventive clinical trials. Final analysis will be presented at ASCO.

No significant financial relationships to disclose.

Effect of blood pH on pulmonary artery pressure, left atrial pressure and fluid filtration rate in isolated rabbit lung

To determine the effects of pH changes on Pulmonary Artery Pressure (PAP), 18 isolated rabbit lung preparations, perfused with autologous blood mixture and constant PaCO2 have been studied. Each preparation was studied under 3 conditions: Baseline: 30 minutes equilibration period. Acidosis: pH was decreased by 0.2 N HCl infusion, the ventilatory rate was changed and different CO2 mixtures were used to maintain the PCO2 within the initial parameters. Compensated Acidosis (CA): pH was returned to normal values by 0.7 N NaHCO3 infusion maintaining PCO2 in its initial values. The decrease in pH (acidosis) from 7.36 +/- 0.05 to 7.18 +/- 0.06 at constant PCO2, generated a significant increase in PAP (13.6 +/- 3.2 cm H2O to 18.8 +/- 5.2 cm H2O, p < 0.01). The pH increase (CA) from 7.18 +/- 0.06 to 7.40 +/- 0.09 caused the PAP to decrease (18.8 +/- 5.2 cm H2O to 15.9 +/- 4.2 cm H2O); the fluid filtration rate remained unchanged during the whole experiment. It is concluded that blood pH changes at constant PCO2 result in significant changes of PAP. Acidemia produces pulmonary vasoconstriction, which may be a contributing factor in the genesis of pulmonary hypertension in clinical conditions with increased hydrogen ion concentration [H+].

Increase in cardiac output and PEEP as mechanism of pulmonary optimization

The influence of cardiac output (CO) and PEEP on pulmonary shunt (Qs/Qt) has been the subjects of considerable investigation but findings are controversial. The role of CO and PEEP on 19 isolated rabbit lung preparations perfused with hypoxic mixture (6% CO2, 10% O2, and 84% N2), which resulted in a constant oxygen venous pressure (64 +/- 5.6 mmHg) has been studied. The first group of 11 preparations were used to study the influence of CO modifications with room air ventilation on the Qs/Qt when the CO rises in 48%; in the second group simultaneous modifications in CO and PEEP (0.5 and 10 cm H2O) were performed. A positive correlation (p < 0.01) in Qs/Qt (0.048 +/- 0.04 to 0.12933 +/- 0.09) was found when the CO increased in the first experimental group, the fluid filtration rate (FFR) also increased and the pulmonary vascular resistance (PVR) remained stable. In the second group an increase of 5 and 10 cm H2O of PEEP at constant CO reduced the Qs/Qt (0.0361 +/- 0.02 to 0.0184 +/- 0.006) while it increased the arterio-venous oxygen difference, PVR and FFR. During high CO conditions increase of 5 and 10 cm H2O of PEEP reduced the Qs/Qt (0.099 +/- 0.03 to 0.027 +/- 0.02) and FFR. These data suggest that when the Qs/Qt is increased, the use of PEEP can compensate the ventilation/perfusion alterations and restore pulmonary gas exchange.

Positive inotropic effects mediated by alpha 1 adrenoceptors in intact human subjects

The role of alpha 1-adrenergic receptors (adrenoceptors) on cardiac contractility was investigated in human subjects. The effect of methoxamine, a selective alpha-adrenoceptor agonist, and angiotensin II, on cardiac contractility was determined by means of noninvasive assessment of the slope of the end-systolic pressure (ESP)/end-systolic dimension (ESD) relationship. The slope (m) of this ratio was significantly higher with methoxamine (17.0; SD = 9.0 mm Hg/mm) than with angiotensin II (4.8; SD = 1.9 mm Hg/mm) (p less than 0.05). Slopes with methoxamine were higher when heart rates (HRs) were reflexly reduced, and were significantly diminished when reflex bradycardia was prevented by atropine (p less than 0.05) or atrial pacing (p less than 0.01). Previous treatment with propranolol did not modify m values with methoxamine (m = 15.5; SD = 4.4 mm Hg/mm). Phentolamine, given at peak methoxamine effect, did not consistently modify m values, resulting in an average slope not significantly different from that obtained with methoxamine alone. However, the addition of phentolamine did not cause an increase in ESDs at each level of ESP with respect to methoxamine. In the same subjects, infusion of phentolamine after angiotensin did not modify ESDs at comparable ESP levels. These findings suggest the existence of a positive inotropic effect mediated by alpha 1 adrenoceptors in the intact human heart.