Peri-infarct zone pacing to prevent adverse left ventricular remodelling in patients with large myocardial infarction

MSC exosome-mediated cardioprotection in ischemic mouse heart comparative proteomics of infarct and peri-infarct areas

Mesenchymal stem cell (MSC) exosomes may limit cardiac injury, and even reverse cardiac damage in animal models of ischemia. To understand exosome-mediated improvement in cardiac function we examined the proteomic alternations in the MSC exosome-treated mice hearts subjected to left coronary artery (LCA) ligation, with particular emphasis on peri-infarct areas. At 7 days after LCA ligation, left ventricular end systolic thickness, infarct size and survival of mice were studied. Mass spectrometric analysis of infarct and peri-infarct areas was carried out. Expression of inflammatory markers (LOX-1 and NLRP3) and cell death markers (Bax, Bcl-2, Caspases 1 and 3 and GSDMD) were investigated by Western blots and immunofluorescence. Proteomic analysis of the infarct and peri-infarct areas in saline-treated hearts revealed differentially expressed proteins involved in inflammation and apoptotic cell death, while showing depletion of processes governing cell death. Exosome treatment significantly improved the proteomic profile in both infarct and peri-infarct areas, more so in the peri-infarct areas. The infarct size was smaller (9 ± 1%), and cardiac contractile function (fractional shortening) was preserved in the exosome-treated mice (28 ± 2%). Survival of exosome-treated mice was also better. White blood cell accumulation in and around the infarct area, expression of LOX-1 and NLRP3 inflammasome, and markers of cell death (cleaved Caspase-3, Caspase-1, GSDMD, Bcl-2 and Bax) were dramatically reduced by MSC exosome treatment (all p < 0.01). In cultured primary mouse cardiomyocytes, treatment with MSC exosomes essentially reversed inflammation-induced pro-apoptotic and inflammatory signals (p < 0.01). MSC exosomes exert their cardioprotective effects by suppressing inflammation and pro-apoptotic processes, particularly in the peri-infarct areas, resulting in preservation of cardiac function after LCA ligation.

Prognostic implications of left ventricular global longitudinal strain in heart failure patients with narrow QRS complex treated with cardiac resynchronization therapy: a subanalysis of the randomized EchoCRT trial

Aim

Left ventricular (LV) global longitudinal strain (GLS) reflects LV systolic function and correlates inversely with the extent of LV myocardial scar and fibrosis. The present subanalysis of the Echocardiography Guided CRT trial investigated the prognostic value of LV GLS in patients with narrow QRS complex.

Methods and results

Left ventricular (LV) global longitudinal strain (GLS) was measured on the apical 2-, 4- and 3-chamber views using speckle tracking analysis. Measurement of baseline LV GLS was feasible in 755 patients (374 with cardiac resynchronization therapy (CRT)-ON and 381 with CRT-OFF). The median value of LV GLS in the overall population was 7.9%, interquartile range 6.2-10.1%. After a mean follow-up period of 19.4 months, 95 patients in the CRT-OFF group and 111 in the CRT-ON group reached the combined primary endpoint of all-cause mortality and heart failure hospitalization. Each 1% absolute unit decrease in LV GLS was independently associated with 11% increase in the risk to reach the primary endpoint (Hazard ratio 1.11; 95% confidence interval 95% 1.04-1.17, P < 0.001), after adjusting for ischaemic cardiomyopathy and randomization treatment among other clinically relevant variables. When categorizing patients according to quartiles of LV GLS, the primary endpoint occurred more frequently in patients in the lowest quartile (<6.2%) treated with CRT-ON vs. CRT-OFF (45.6% vs. 28.7%, P = 0.009) whereas, no differences were observed in patients with LV GLS ≥6.2% treated with CRT-OFF vs. CRT-ON (23.7% vs. 24.5%, respectively; P  = 0.62).

Conclusion

Low LV GLS is associated with poor outcome in heart failure patients with QRS width <130 ms, independent of randomization to CRT or not. Importantly, in the group of patients with the lowest LV GLS quartile, CRT may have a detrimental effect on clinical outcomes.

Predictors of Left Ventricular Remodeling After Myocardial Infarction in Patients With a Patent Infarct Related Coronary Artery After Percutaneous Coronary Intervention (from the Post-Myocardial Infarction Remodeling Prevention Therapy [PRomPT] Trial)

Left ventricular (LV) remodeling after myocardial infarction (MI) is a strong predictor of heart failure and mortality. The predictors of long-term remodeling after MI have been incompletely studied. We therefore examined the correlates of LV remodeling in patients with large ST-segment elevation myocardial infarction and a patent infarct artery after percutaneous 2coronary intervention (PCI) from the randomized Post-Myocardial Infarction Remodeling Prevention Therapy trial. Peri-infarct pacing had a neutral effect on long-term remodeling in patients with large first MI. The present analysis includes 109 patients in whom an open artery was restored after PCI, and in whom LV end-diastolic volume (LVEDV) at baseline and 18 months was assessed by transthoracic echocardiography. Multivariable models were fit to identify the independent predictors of LVEDV at baseline and 18 months. By multivariable analysis, male sex (p = 0.004) and anterior MI location (p = 0.03) were independently associated with baseline LVEDV. The following variables were independent predictors of increased LVEDV at 18 months: younger age (p = 0.01), male sex (p = 0.03), peak creatine phosphokinase (p = 0.03), shorter time from MI to baseline transthoracic echocardiography (p = 0.04), baseline LVEDV (p < 0.0001), and lack of statin use (p = 0.03). In conclusion, patients with large MI and an open infarct artery after PCI, anterior MI location, and male sex were associated with greater baseline LVEDV, but MI location was not associated with 18-month LVEDV. In contrast, younger age, peak creatine phosphokinase, male sex, baseline LVEDV, and lack of statin use were associated with long-term LV remodeling.

Institution of localized high-frequency electrical stimulation targeting early myocardial infarction: Effects on left ventricle function and geometry

BACKGROUND

Although strategies have focused on myocardial salvage/regeneration in the context of an acute coronary syndrome and a myocardial infarction (MI), interventions targeting the formed MI region and altering the course of the post-MI remodeling process have not been as well studied. This study tested the hypothesis that localized high-frequency stimulation instituted within a formed MI region using low-amplitude electrical pulses would favorably change the trajectory of changes in left ventricle geometry and function.

METHODS

At 7 days following MI induction, pigs were randomized for localized high-frequency stimulation (n = 5, 240 bpm, 0.8 V, and 0.05 ms pulses) or unstimulated (n = 6). Left ventricle geometry and function were measured at baseline (pre-MI) and at 7, 14, 21, and 28 days post-MI using echocardiography. MI size at 28 days post-MI was determined by histochemical staining and planimetry.

RESULTS

At 7 days post-MI and before randomization to localized high-frequency stimulation, left ventricular ejection fraction and end-diastolic volume was equivalent. However, when compared with 7-day post-MI values, left ventricle end-diastolic volume increased in a time-dependent manner in the MI unstimulated group, but the relative increase in left ventricle end-diastolic volume was reduced in the MI localized high-frequency stimulation group. For example, by 28 days post-MI, left ventricle end-diastolic volume increased by 32% in the MI unstimulated group but only by 12% in the MI localized high-frequency stimulation group (P < .05). Whereas left ventricular ejection fraction appeared unchanged between MI groups, estimates of pulmonary capillary wedge pressure, a marker of adverse left ventricle performance and progression to failure, increased by 62% in the MI unstimulated group and actually decreased by 17% in the MI localized high-frequency stimulation group when compared with 7-day post-MI values (P < .05). MI size was equivalent between the MI groups, indicative of no difference in the extent of absolute myocardial injury.

CONCLUSIONS

The unique findings from this study are 2-fold. First, targeting the MI region following the resolution of the acute event using a localized stimulation approach is feasible. Second, localized stimulation modified a key parameter of adverse post-MI remodeling (dilation) and progression to heart failure. These findings demonstrate that the MI region itself is a modifiable tissue and responsive to localized electrical stimulation.

Correlates and prognostic impact of new-onset heart failure after ST-segment elevation myocardial infarction treated with primary percutaneous coronary intervention: insights from the INFUSE-AMI trial

Background:

The determinants and significance of early (30-day) heart failure symptoms after primary percutaneous coronary intervention for ST-segment elevation myocardial infarction (STEMI) remain unclear. We investigated the clinical and imaging correlates of early post-discharge heart failure in patients with STEMI, and evaluated its impact on clinical outcomes.

Methods:

Patients from the INFUSE-AMI trial were categorized according to New York Heart Association (NYHA) functional classification at their 30-day visit (NYHA class ≥2 versus 1). Independent correlates of NYHA class ≥2 were determined by multivariable logistic regression. A landmark analysis beyond 30 days was performed to assess the impact of 30-day NYHA class ≥2 on 1-year risk of death or hospitalization for heart failure.

Results:

Among 402 patients enrolled in the INFUSE-AMI trial with data on NYHA class at 30 days, 76 (18.9%) had NYHA class ≥2. Independent correlates of 30-day NYHA class ≥2 were age, Killip class ≥2 at presentation, heart rate at presentation, intraprocedural no-reflow, and 30-day infarct size (% total ventricular mass). After adjustment for infarct size, patients with NYHA class ≥2 remained at higher risk of death or hospitalization for heart failure at 1-year follow-up compared to those in NYHA class 1 (11.8% vs. 2.8%, adjusted hazard ratio 3.78, 95% confidence interval 1.16–12.22, P=0.03).

Conclusions:

Clinical, procedural, and imaging variables predict the development of clinical heart failure after primary percutaneous coronary intervention in patients with STEMI. Early post-discharge heart failure symptoms identify a high-risk patient cohort for subsequent heart failure hospitalization and death, independent of infarct size.

Trial Registration:

ClinicalTrials.gov ; NCT00976521

Intermittent pacing therapy favorably modulates infarct remodeling

Despite early revascularization, remodeling and dysfunction of the left ventricle (LV) after acute myocardial infarction (AMI) remain important therapeutic targets. Intermittent pacing therapy (IPT) of the LV can limit infarct size, when applied during early reperfusion. However, the effects of IPT on post-AMI LV remodeling and infarct healing are unknown. We therefore investigated the effects of IPT on global LV remodeling and infarct geometry in swine with a 3-day old AMI. For this purpose, fifteen pigs underwent 2 h ligation of the left circumflex coronary artery followed by reperfusion. An epicardial pacing lead was implanted in the peri-infarct zone. After three days, global LV remodeling and infarct geometry were assessed using magnetic resonance imaging (MRI). Animals were stratified into MI control and IPT groups. Thirty-five days post-AMI, follow-up MRI was obtained and myofibroblast content, markers of extracellular matrix (ECM) turnover and Wnt/frizzled signaling in infarct and non-infarct control tissue were studied. Results showed that IPT had no significant effect on global LV remodeling, function or infarct mass, but modulated infarct healing. In MI control pigs, infarct mass reduction was principally due to a 26.2 ± 4.4% reduction in infarct thickness (P ≤ 0.05), whereas in IPT pigs it was mainly due to a 35.7 ± 4.5% decrease in the number of infarct segments (P ≤ 0.05), with no significant change in infarct thickness. Myofibroblast content of the infarct zone was higher in IPT (10.9 ± 2.1%) compared to MI control (5.4 ± 1.6%; P ≤ 0.05). Higher myofibroblast presence did not coincide with alterations in expression of genes involved in ECM turnover or Wnt/frizzled signaling at 5 weeks follow-up. Taken together, IPT limited infarct expansion and altered infarct composition, showing that IPT influences remodeling of the infarct zone, likely by increasing regional myofibroblast content.