Right coronary artery ligation in mice: a novel method to investigate right ventricular dysfunction and biventricular interaction

Computational modeling of ventricular-ventricular interactions suggest a role in clinical conditions involving heart failure

Introduction: The left (LV) and right (RV) ventricles are linked biologically, hemodynamically, and mechanically, a phenomenon known as ventricular interdependence. While LV function has long been known to impact RV function, the reverse is increasingly being realized to have clinical importance. Investigating ventricular interdependence clinically is challenging given the invasive measurements required, including biventricular catheterization, and confounding factors such as comorbidities, volume status, and other aspects of subject variability. Methods: Computational modeling allows investigation of mechanical and hemodynamic interactions in the absence of these confounding factors. Here, we use a threesegment biventricular heart model and simple circulatory system to investigate ventricular interdependence under conditions of systolic and diastolic dysfunction of the LV and RV in the presence of compensatory volume loading. We use the end-diastolic pressure-volume relationship, end-systolic pressure-volume relationship, Frank Starling curves, and cardiac power output as metrics. Results: The results demonstrate that LV systolic and diastolic dysfunction lead to RV compensation as indicated by increases in RV power. Additionally, RV systolic and diastolic dysfunction lead to impaired LV filling, interpretable as LV stiffening especially with volume loading to maintain systemic pressure. Discussion: These results suggest that a subset of patients with intact LV systolic function and diagnosed to have impaired LV diastolic function, categorized as heart failure with preserved ejection fraction (HFpEF), may in fact have primary RV failure. Application of this computational approach to clinical data sets, especially for HFpEF, may lead to improved diagnosis and treatment strategies and consequently improved outcomes.

Neurovascular hypoxia after mild traumatic brain injury in juvenile mice correlates with heart-brain dysfunctions in adulthood

AIM

Retrospective studies suggest that mild traumatic brain injury (mTBI) in pediatric patients may lead to an increased risk of cardiac events. However, the exact functional and temporal dynamics and the associations between heart and brain pathophysiological trajectories are not understood.

METHODS

A single impact to the left somatosensory cortical area of the intact skull was performed on juvenile mice (17 days postnatal). Cerebral 3D photoacoustic imaging was used to measure the oxygen saturation (sO₂ ) in the impacted area 4 h after mTBI followed by 2D and 4D echocardiography at days 7, 30, 90, and 190 post-impact. At 8 months, we performed a dobutamine stress test to evaluate cardiac function. Lastly, behavioral analyses were conducted 1 year after initial injury.

RESULTS

We report a rapid and transient decrease in cerebrovascular sO₂ and increased hemoglobin in the impacted left brain cortex. Cardiac analyses showed long-term diastolic dysfunction and a diminished systolic strain response under stress in the mTBI group. At the molecular level, cardiac T-p38MAPK and troponin I expression was pathologic modified post-mTBI. We found linear correlations between brain sO₂ measured immediately post-mTBI and long-term cardiac strain after 8 months. We report that initial cerebrovascular hypoxia and chronic cardiac dysfunction correlated with long-term behavioral changes hinting at anxiety-like and memory maladaptation.

CONCLUSION

Experimental juvenile mTBI induces time-dependent cardiac dysfunction that corresponds to the initial neurovascular sO₂ dip and is associated with long-term behavioral modifications. These imaging biomarkers of the heart-brain axis could be applied to improve clinical pediatric mTBI management.

Primary isolated right ventricular failure after heart transplantation: prevalence, right ventricular characteristics, and outcomes

To determine the prevalence, right ventricular (RV) characteristics, and outcomes of primary isolated RV failure (PI-RVF) after heart transplant (HTX). PI-RVF was defined as (1) the need for mechanical circulatory support post-transplant, or (2) evidence of RVF post-transplant as measured by right atrial pressure (RAP) > 15 mmHg, cardiac index of < 2.0 L/min/m² or inotrope support for < 72 h, pulmonary capillary wedge pressure < 18 mmHg, and transpulmonary gradient < 15 mmHg with pulmonary systolic pressure < 50 mmHg. PI-RVF can be diagnosed from the first 24-72 h after completion of heart transplantation. A total of 122 consecutive patients who underwent HTX were reviewed. Of these, 11 were excluded because of secondary causes of graft dysfunction (GD). PI-RVF was present in 65 of 111 patients (59%) and 31 (48%) met the criteria for PGD-RV. Severity of patients with PI-RVF included 41(37%) mild, 14 (13%) moderate, and 10 (9%) severe. The median onset of PI-RVF was 14 (0-49) h and RV recovery occurred 5 (3-14) days after HTX. Severe RV failure was a predictor of 30-day mortality (HR 13.2, 95% CI 1.6-124.5%, p < 0.001) and post-transplant dialysis (HR 6.9, 95% CI 2.0-257.4%, p = 0.001). Patients with moderate PI-RVF had a higher rate of 30-day mortality (14% vs. 0%, p = 0.014) and post-operative dialysis (21% vs. 2%, p = 0.016) than those with mild PI-RVF. Among patients with mild and moderate PI-RVF, patients who did not meet the criteria of PGD-RV had worsening BUN/creatinine than those who met the PGD-RV criteria (p < 0.05 for all). PI-RVF was common and can occur after 24 h post-HTX. The median RV recovery time was 5 (2-14) days after HTX. Severe PI-RVF was associated with increased rates of 30-day mortality and post-operative dialysis. Moderate PI-RVF was also associated with post-operative dialysis. A revised definition of PGD-RV may be needed since patients who had adverse outcomes did not meet the criteria of PGD-RV.

High-impact opportunities to address ischemia: a focus on heart and circulatory research

Myocardial ischemic injury and its resolution are the key determinants of morbidity or mortality in heart failure. The cause and duration of ischemia in patients vary. Numerous experimental models and methods have been developed to define genetic, metabolic, molecular, cellular, and pathophysiological mechanisms, in addition to defining structural and functional deterioration of cardiovascular performance. The rapid rise of big data, such as single-cell analysis techniques with bioinformatics, machine learning, and neural networking, brings a new level of sophistication to our understanding of myocardial ischemia. This mini-review explores the multifaceted nature of ischemic injury in the myocardium. We highlight recent state-of-the-art findings and strategies to show new directions of high-impact approach to understanding myocardial tissue remodeling. This next age of heart and circulatory physiology research will be more comprehensive and collaborative to uncover the origin, progression, and manifestation of heart failure while strengthening novel treatment strategies.

Guidelines for in vivo mouse models of myocardial infarction

Despite significant improvements in reperfusion strategies, acute coronary syndromes all too often culminate in a myocardial infarction (MI). The consequent MI can, in turn, lead to remodeling of the left ventricle (LV), the development of LV dysfunction, and ultimately progression to heart failure (HF). Accordingly, an improved understanding of the underlying mechanisms of MI remodeling and progression to HF is necessary. One common approach to examine MI pathology is with murine models that recapitulate components of the clinical context of acute coronary syndrome and subsequent MI. We evaluated the different approaches used to produce MI in mouse models and identified opportunities to consolidate methods, recognizing that reperfused and nonreperfused MI yield different responses. The overall goal in compiling this consensus statement is to unify best practices regarding mouse MI models to improve interpretation and allow comparative examination across studies and laboratories. These guidelines will help to establish rigor and reproducibility and provide increased potential for clinical translation.

pH-sensitive doxorubicin-tocopherol succinate prodrug encapsulated in docosahexaenoic acid-based nanostructured lipid carriers: An effective strategy to improve pharmacokinetics and reduce toxic effects

Side effects often limit the use of doxorubicin (DOX) in cancer treatment. We have recently developed a nanostructured lipid carrier (NLC) formulation for synergistic chemotherapy, encapsulating DOX and the anticancer adjuvants docosahexaenoic acid (DHA) and α-tocopherol succinate (TS). Hydrophobic ion-pairing with TS allowed a high DOX entrapment in the nanocarrier. In this work, we investigated the pharmacokinetics of this formulation after intravenous administration in mice. The first data obtained led us to propose synthesizing covalent DOX-TS conjugates to increase DOX retention in the NLC. We successfully conjugated DOX to TS via an amide or hydrazone bond. In vitro studies in 4T1 tumor cells indicated low cytotoxicity of the amide derivative, while the hydrazone conjugate was effective in killing cancer cells. We encapsulated the hydrazone derivative in a DHA-based nanocarrier (DOX-hyd-TS/NLC), which had reduced particle size and high drug encapsulation efficiency. The pH-sensitive hydrazone bond allowed controlled DOX release from the NLC, with increased drug release at acidic conditions. In vivo studies revealed that DOX-hyd-TS/NLC had a better pharmacokinetic profile than free DOX and attenuated the short-term cardiotoxic effects caused by DOX, such as QT prolongation and impaired left ventricular systolic function. Moreover, this formulation showed excellent therapeutic performance by reducing tumor growth in 4T1 tumor-bearing mice and decreasing DOX-induced toxicity to the heart and liver, demonstrated by hematologic, biochemical, and histologic analyses. These results indicate that DOX-hyd-TS/NLC may be a promising nanocarrier for breast cancer treatment.

Nanomedicine in Oncocardiology: Contribution and Perspectives of Preclinical Studies

Cancer and cardiovascular diseases are the leading causes of death and morbidity worldwide. Strikingly, cardiovascular disorders are more common and more severe in cancer patients than in the general population, increasing incidence rates. In this context, it is vital to consider the anticancer efficacy of a treatment and the devastating heart complications it could potentially cause. Oncocardiology has emerged as a promising medical and scientific field addressing these aspects from different angles. Interestingly, nanomedicine appears to have great promise in reducing the cardiotoxicity of anticancer drugs, maintaining or even enhancing their efficacy. Several studies have shown the benefits of nanocarriers, although with some flaws when considering the concept of oncocardiology. Herein, we discuss how preclinical studies should be designed as closely as possible to clinical protocols, considering various parameters intrinsic to the animal models used and the experimental protocols. The sex and age of the animals, the size and location of the tumors, the doses of the nanoformulations administered, and the acute vs. the long-term effects of treatments are essential aspects. We also discuss the perspectives offered by non-invasive imaging techniques to simultaneously assess both the anticancer effects of treatment and its potential impact on the heart. The overall objective is to accelerate the development and validation of nanoformulations through high-quality preclinical studies reproducing the clinical conditions.

Cardioprotection in right heart failure

Ischaemic and pharmacological conditioning of the left ventricle is mediated by the activation of signalling cascades, which finally converge at the mitochondria and reduce ischaemia/reperfusion (I/R) injury. Whereas the molecular mechanisms of conditioning in the left ventricle are well characterized, cardioprotection of the right ventricle is principally feasible but less established. Similar to what is known for the left ventricle, a dysregulation in signalling pathways seems to play a role in I/R injury of the healthy and failing right ventricle and in the ability/inability of the right ventricle to respond to a conditioning stimulus. The maintenance of mitochondrial function seems to be crucial in both ventricles to reduce I/R injury. As far as currently known, similar molecular mechanisms mediate ischaemic and pharmacological preconditioning in the left and right ventricles. However, the two ventricles seem to respond differently towards exercise‐induced preconditioning.

LINKED ARTICLES

This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.23/issuetoc

Impact of concurrent right ventricular myocardial infarction on outcomes among patients with left ventricular myocardial infarction

To compare in-hospital outcomes between left ventricular myocardial infarction (LVMI) patients with and without right ventricular myocardial infarction (RVMI). Patients with acute ST-segment elevation MI (STEMI) undergoing primary percutaneous coronary intervention (PCI) were enrolled and divided into LVMI with and without RVMI groups. Between-group differences and in-hospital outcomes were compared. Compared to patients without RVMI, patients with RVMI were more likely to be male, have higher body mass index, serum levels of C-reactive protein (8.9 ± 2.4 vs 6.2 ± 2.1 mg/dL), B-type natriuretic peptide (1295 ± 340 vs 872 ± 166 pg/mL) and cardiac troponin-I (8.6 ± 2.9 vs 5.2 ± 2.1 ng/mL), and have diabetes (36.3% vs 3.4%) and dyslipidemia (53.4% vs 48.1%). Patients with RVMI had lower left and right ventricular ejection fraction (50.5 ± 5.6% vs 53.4 ± 3.8% and 33.6 ± 2.9% vs 45.7 ± 2.0%), but had higher mean pulmonary artery pressure (30.6 ± 3.3 vs 23.8 ± 3.1 mm Hg). Compared to patients without RVMI, patients with RVMI had higher odds of in-hospital all-cause mortality (4.1% vs 1.0%) and new onset acute heart failure (3.4% vs 1.0%). After adjusted for confounding factors, LVMI with RVMI remained independently associated with composite outcomes, with odds ratio 1.66 (95% confidence interval 1.39–2.04). Compared to isolated LVMI patients, those with concomitant RVMI have higher odds of in-hospital complications, particularly all-cause mortality and new onset acute heart failure.