Original communication

The speed of healing of myocardial infarction: A study of the pathologic anatomy in seventy-two cases☆

Atherosclerotic cardiovascular disease is the number one killer of both men and women in industrialized countries. Occlusion of the arteries to the heart, the coronary arteries, leads to myocardial ischemia, an imbalance between oxygen supply and demand in the heart muscle. If the ischemia is of sufficient severity and duration, death of myocardium, myocardial infarction (MI), occurs. This can lead to failure of the heart as a pump, or to electrical system failure leading to arrhythmias and sudden death. Other complications in individuals who survive, include aneurysms, ruptures, and/or valvular dysfunction of the heart. The only effective early treatment to date is to reperfuse the ischemic muscle. Myocardial conditioning can have a temporizing and partially protective effect on evolving MI. As more is learned about the molecular biology of the ischemic myocardium, there is optimism regarding the potential for novel methods of myocardial preservation and regeneration for those who suffer from this disease. This chapter focuses on the morphologic features of the coronary arteries and the heart in patients with ischemic heart disease.

The mechanical environment and anisotropic structure of the heart modulate cardiac function at the cellular, tissue and organ levels. During myocardial infarction (MI) and subsequent healing, however, this landscape changes significantly. In order to engineer cardiac biomaterials with the appropriate properties to enhance function after MI, the changes in the myocardium induced by MI must be clearly identified. In this review, we focus on the mechanical and structural properties of the healthy and infarcted myocardium in order to gain insight about the environment in which biomaterial-based cardiac therapies are expected to perform and the functional deficiencies caused by MI that the therapy must address. From this understanding, we discuss epicardial therapies for MI inspired by the mechanics and anisotropy of the heart focusing on passive devices, which feature a biomaterials approach, and active devices, which feature robotic and cellular components. Through this review, a detailed analysis is provided in order to inspire further development and translation of epicardial therapies for MI.

Myocardial infarction (MI) is one of leading diseases to contribute to annual death rate of 5% in the world. In the past decades, significant work has been devoted to this subject. Biomechanics of infarcted left ventricle (LV) is associated with MI diagnosis, understanding of remodelling, MI micro-structure and biomechanical property characterizations as well as MI therapy design and optimization, but the subject has not been reviewed presently. In the article, biomechanics of infarcted LV was reviewed in terms of experiments achieved in the subject so far. The concerned content includes experimental remodelling, kinematics and kinetics of infarcted LVs. A few important issues were discussed and several essential topics that need to be investigated further were summarized. Microstructure of MI tissue should be observed even carefully and compared between different methods for producing MI scar in the same animal model, and eventually correlated to passive biomechanical property by establishing innovative constitutive laws. More uniaxial or biaxial tensile tests are desirable on MI, border and remote tissues, and viscoelastic property identification should be performed in various time scales. Active contraction experiments on LV wall with MI should be conducted to clarify impaired LV pumping function and supply necessary data to the function modelling. Pressure-volume curves of LV with MI during diastole and systole for the human are also desirable to propose and validate constitutive laws for LV walls with MI.

The aim of this systematic review was to identify exercise parameters and outcome measures used in cardiac rehabilitation programs following median sternotomy, in the elderly cardiac population.

Five (5) electronic databases were searched for relevant studies published in English after 1997.

The screening process was completed by two independent researchers, with a third independent reviewer for overall agreement. Studies were selected if they included only cardiac patients aged ≥65 years who had undergone valve surgery and/or coronary artery bypass grafting via median sternotomy, and who had undertaken a postoperative cardiac rehabilitation exercise intervention assessing physical function and/or cognitive recovery as outcomes.

Two researchers independently completed the data extraction and quality assessment. Quality was assessed using a modified Downs and Black tool.

In total, 11 articles were included for appraisal with respect to the quality of the study. Only two randomised controlled trials were suitable for meta-analysis. A higher volume of exercise was shown to have a positive effect on functional recovery, assessed using the 6-minute walk test (6MWT) (mean difference = 26.97 m; 95% confidence interval [CI], 6.96–46.97; p = 0.008; I² = 0%). No significant improvement was shown between additional exercise compared to standard care in improving VO_2peak, maximal power output or quality of life. No studies evaluated the effect of exercise on cognitive recovery.

Exercise significantly improves functional recovery in the post-surgical elderly cardiac population, however uncertainty still exists with regard to which modes of exercise and their specific parameters are most effective in improving cognitive recovery.

Cardiovascular magnetic resonance (CMR) provides a variety of methods of obtaining information on residual viability after myocardial infarction. Indirect signs of viability that can be observed by CMR are any sign of wall thickening at rest (which is detectable with high accuracy by cine CMR), wall thickening after stimulation by low-dose dobutamine, preserved wall thickness, and a preserved viable epicardial rim. On the other hand, myocardial necrosis is characterized by late gadolinium enhancement (LGE) (possibly with a low-intensity core region due to no reflow) of the infarct area after injection of gadolinium, reduced wall thickness (in chronic infarcts) without a substantial viable rim, and the absence of a contractile reserve during dobutamine stimulation. Evaluation of viable myocardium is most important in patients with severe left ventricular (LV) dysfunction because these patients can gain most from revascularization if substantial amounts of myocardium are present. Recent data from the Surgical Treatment for Ischemic Heart Failure (STICH) trial questioned the value of viability imaging for improving outcome in these patients. Unfortunately, the information available about the value of CMR techniques in identifying patients with global LV dysfunction who have a high likelihood of profiting from a coronary revascularization is still scarce. Low-dose dobutamine CMR may be less accurate than LGE CMR in this patient group. In patients with regional LV dysfunction, however, in whom the need for revascularization needs to be established, both dobutamine CMR and LGE CMR are well validated and can be used clinically. Depiction of zones of acute necrosis by observing enhancement after gadolinium carries substantial promise for detailed studies of the effects of different treatment strategies for acute myocardial infarction as well as for treatment in the early and late postinfarction phase. In contrast, CMR may not be able to hold its initial promise for identifying the area at risk and distinguish it from the area of infarction.

Coronary atherosclerosis is the leading cause of sudden death in developed nations. Triggers for sudden death include physical and emotional stress. At autopsy coronary artery atheroma is a common finding and may or may not be related to the cause of death. The forensic pathologist must consider the relative significant of disease, trauma and toxicological findings when determining the cause of death. This requires a consideration of evidence beyond the autopsy including the history, scene and ancillary investigations. Certain drugs including cocaine and methamphetamine are known to be atherogenic and acute and chronic use may be a factor in sudden death with underlying coronary artery atherosclerosis. Sudden death may also be associated with criminal conduct, when the scenario of “homicide by heart attack” needs to be considered. This review analyses forensic aspects of coronary artery disease.