Relation of thallium uptake to morphologic features of chronic ischemic heart disease: evidence for myocardial remodeling in noninfarcted myocardium

The role of ferroptosis in cell-to-cell propagation of cell death initiated from focal injury in cardiomyocytes

AIMS

Ferroptosis has grown in importance as a key factor in ischemia-reperfusion (I/R) injury. This study explores the mechanism underlying fibrotic scarring extending along myofibers in cardiac ischemic injury and demonstrates the integral role of ferroptosis in causing a unique cell death pattern linked to I/R injury.

MAIN METHODS

Cadaveric hearts from individuals who had ischemic injury were examined by histological assays. We created a novel model of inducing cell death in H9c2 cells, and used it to demonstrate ferroptotic cell death extending in a cell-to-cell manner. Ex vivo Langendorff-perfused hearts were used alongside the model to replicate cell death extension along myofibers while also demonstrating protective effects of a ferroptosis inhibitor, ferrostatin-1 (Fer-1).

KEY FINDINGS

Human hearts from individuals who had I/R injury demonstrated scarring along myofibers that was consistent with mouse models, suggesting that cell death extended from cell-to-cell. Treatment with Ras-selective lethal 3 (RSL3), a ferroptosis inducer, and exposure to excess iron exacerbated cell death propagation in in vitro models, and inhibition of ferroptosis by Fer-1 blunted this effect in both settings. In ex vivo models, Fer-1 was sufficient to reduce cell death along the myofibers caused by external injury.

SIGNIFICANCE

The unique I/R injury-induced pattern of cell death along myofibers requires novel injury models that mimic this phenomenon, thus we established new methods to replicate it. Ferroptosis is important in propagating injury between cells and better understanding this mechanism may lead to therapeutic responses that limit I/R injury.

The Potential of Clinical Phenotyping of Heart Failure With Imaging Biomarkers for Guiding Therapies: A Focused Update

The need for noninvasive assessment of cardiac volumes and ejection fraction (EF) ushered in the use of cardiac imaging techniques in heart failure (HF) trials that investigated the roles of pharmacological and device-based therapies. However, in contrast to HF with reduced EF (HFrEF), modern HF pharmacotherapy has not improved outcomes in HF with preserved EF (HFpEF), largely attributed to patient heterogeneity and incomplete understanding of pathophysiological insights underlying the clinical presentations of HFpEF. Modern cardiac imaging methods offer insights into many sets of changes in cardiac tissue structure and function that can precisely link cause with cardiac remodeling at organ and tissue levels to clinical presentations in HF. This has inspired investigators to seek a more comprehensive understanding of HF presentations using imaging techniques. This article summarizes the available evidence regarding the role of cardiac imaging in HF. Furthermore, we discuss the value of cardiac imaging techniques in identifying HF patient subtypes who share similar causes and mechanistic pathways that can be targeted using specific HF therapies.

Cardiac molecular imaging to track left ventricular remodeling in heart failure

Cardiac left ventricular (LV) remodeling is the final common pathway of most primary cardiovascular diseases that manifest clinically as heart failure (HF). The more advanced the systolic HF and LV dysfunction, the worse the prognosis. The knowledge of the molecular, cellular, and neurohormonal mechanisms that lead to myocardial dysfunction and symptomatic HF has expanded rapidly and has allowed sophisticated approaches to understanding and management of the disease. New therapeutic targets for pharmacologic intervention in HF have also been identified through discovery of novel cellular and molecular components of membrane-bound receptor-mediated intracellular signal transduction cascades. Despite all advances, however, the prognosis of systolic HF has remained poor in general. This is, at least in part, related to the (1) relatively late institution of treatment due to reliance on gross functional and structural abnormalities that define the "heart failure phenotype" clinically; (2) remarkable genetic-based interindividual variations in the contribution of each of the many molecular components of cardiac remodeling; and (3) inability to monitor the activity of individual pathways to cardiac remodeling in order to estimate the potential benefits of pharmacologic agents, monitor the need for dose titration, and minimize side effects. Imaging of the recognized ultrastructural components of cardiac remodeling can allow redefinition of heart failure based on its "molecular phenotype," and provide a guide to implementation of "personalized" and "evidence-based" evaluation, treatment, and longitudinal monitoring of the disease beyond what is currently available through randomized controlled clinical trials.

Residual stress ischaemia is associated with blood markers of myocardial structural remodelling

BACKGROUND

Long-term prognosis of coronary artery disease (CAD) patients is worsened when stress ischemia persists on treatment, but the relationship with adverse cardiac remodelling had never been investigated.

AIM

To analyze changes in blood markers of fibrosis in patients with chronic CAD exhibiting exercise ischaemia.

METHODS

Circulating markers of collagen: (i) turnover (amino-terminal propeptide of collagen-III [PIIINP]) and (ii) degradation (matrix metalloproteinase 1 [MMP-1]), were obtained in 139 CAD patients referred for exercise 201Tl-SPECT.

RESULTS

In the 57 patients who had SPECT-ischaemia, PIIINP was higher (4.3+/-2.9 microg L-1 vs. 3.1+/-1.5 microg L-1, p=0.002) and MMP-1 lower (3.8+/-2.1 microg L-1 vs. 4.7+/-2.8 microg L-1, p=0.04) than in the 82 patients without SPECT-ischaemia. PIIINP was independently related to LV volume, SPECT-ischaemia and age, whereas MMP-1 was related to current treatment with ACEI and beta-blockers (p<0.05). In the 104 patients with a normal LV ejection fraction, only PIIINP was related to SPECT-ischaemia (4.1+/-2.2 microg L-1 vs. 3.1+/-1.5 microg L-1, p=0.01).

CONCLUSION

In patients with chronic CAD, exercise ischaemia is associated with increased collagen-III turnover, independently of concomitant medications and even when LV ejection fraction is normal. Long-term, this increase might relate to adverse cardiac remodelling even when cardiac function is not clearly affected at baseline.

The accuracy of electrocardiographic Q waves for the detection of prior myocardial infarction as assessed by a novel standard of reference

BACKGROUND

The electrocardiogram (ECG) is valuable for the identification of prior myocardial infarction (MI) in individuals participating in epidemiologic studies or undergoing screening examinations. Although the Minnesota Code, a set of criteria for the interpretation of ECGs in such situations, is commonly used to identify MI in these settings, its accuracy is incompletely understood.

HYPOTHESIS

We sought to test the accuracy of the Minnesota Code Q and QS criteria for MI against a new standard of reference, the presence of a perfusion defect on a resting myocardial scintigraphic image.

METHODS

The resting myocardial scintigrams of all patients studied in our nuclear cardiology laboratory during 7 consecutive months were screened for the presence of perfusion defects. For each patient with such a defect, two individuals examined on the same day, who had no perfusion defect, were selected as controls. Electrocardiograms recorded within 30 days of the scintigraphy were read blindly by two of the authors using the Minnesota Code criteria for Q or QS waves indicative of MI.

RESULTS

For 214 patients selected on the basis of their scintigraphic findings, a satisfactory ECG recorded within a month of the scintigraphy was also available. The overall sensitivity of the Q or QS criteria was 0.58 and the specificity was 0.75. As might be expected when only the most stringent criteria were applied, sensitivity was least and the specificity best.

CONCLUSIONS

As in previous studies, in which necropsy material served as the standard of reference, sensitivity of the Q and QS criteria contained in the Minnesota Code is relatively modest and specificity is reasonable but not outstanding.

Single photon emission computed tomography perfusion imaging for assessment of myocardial viability and management of heart failure

In the setting of coronary artery disease, some areas of dysfunctional myocardium may realize significant improvement in function as a consequence of revascularization. These areas represent viable myocardium, encompassing a spectrum of pathophysiology ranging from chronic stunning, in which resting blood flow is preserved, to hibernating myocardium, in which resting blood flow is decreased. The accurate preoperative evaluation of viable myocardium helps identify those patients with left ventricular dysfunction who will most benefit from coronary revascularization. Of the various modalities available for viability assessment, the nuclear medicine techniques (201)Thallium and (18)Fluorodeoxyglucose positron emission tomography have emerged as the most sensitive. It has been consistently shown that in patients with a significant amount of viable myocardium, there is a substantial survival benefit in revascularization versus medical therapy. The likelihood of affecting a significant improvement decreases with time to revascularization, however, particularly in the setting of an enlarged left ventricle secondary to ventricular remodeling.

Long-term outcome after coronary artery bypass grafting in patients with severe left ventricular dysfunction

BACKGROUND

The aim of this study was to define the potential for long-term survival with severe left ventricular dysfunction after coronary bypass and to quantify any improvement in overall functional status.

METHODS

Left ventricular dysfunction was confirmed preoperatively and the long-term survival and functional outcome after bypass was determined by follow-up studies obtained during the span of a decade.

RESULTS

From 1/1990 to 12/1999, 86 patients with severe left ventricular dysfunction (mean ejection fraction, 0.18 +/- 0.03; range, 0.10 to 0.20) underwent coronary artery bypass grafting. There were 10 perioperative deaths (11% mortality). The mean survival was 55 months (standard deviation +/- 34 months; range, 2 to 141 months) with an actual 5-year survival rate of 59% (actuarial 5-year 65%, 10-year 33%). Echocardiography obtained between 1 and 6 months, 6 months and 1 year, 1 and 2 years, 2 and 4 years, 4 and 6 years, and 6 and 11 years showed the ejection fraction improved to 0.29 +/- 0.08 (p < 0.001), 0.31 +/- 0.14 (p < 0.002), 0.35 +/- 0.08 (p < 0.001), 0.27 +/- 0.10 (p = 0.002), 0.36 +/- 0.14 (p = 0.004), and 0.30 +/- 0.11 (p = 0.004), respectively. At 1 to 6 months, 6 months to 1 year, and 1 to 2 years, the diastolic left ventricular dimension was unchanged, but the systolic left ventricular dimension decreased significantly from 5.02 +/- 0.77 cm to 4.26 +/- 0.91 cm (p = 0.046), 3.98 +/- 1.43 cm (p = 0.08), and 4.10 +/- 1.14 cm (p = 0.07). The preoperative New York Heart Association classification for all patients improved from 2.8 +/- 0.8 to 1.6 +/- 0.7 (p < 0.001) after a mean of 53 months (standard deviation +/- 34 months).

CONCLUSIONS

Patients with severe left ventricular dysfunction can derive long-term benefit from coronary bypass through improved left ventricular contractility as documented by a significantly decreased systolic left ventricular dimension and increased ejection fraction. Successful bypass is associated with a 59% actual 5-year survival rate and significantly improved New York Heart Association functional class.