Historical Perspective: Harvey's epoch-making discovery of the Circulation, its historical antecedents, and some initial consequences on medical practice

Perspectives on the History of Coronary Physiology: Discovery of Major Principles and Their Clinical Correlates

Coronary circulation plays an essential role in delivering oxygen and metabolic substrates to satisfy the considerable energy demand of the heart. This article reviews the history that led to the current understanding of coronary physiology, beginning with William Harvey's revolutionary discovery of systemic blood circulation in the 17th century, and extending through the 20th century when the major mechanisms regulating coronary blood flow (CBF) were elucidated: extravascular compressive forces, metabolic control, pressure-flow autoregulation, and neural pathways. Pivotal research studies providing evidence for each of these mechanisms are described, along with their clinical correlates. The authors describe the major role played by researchers in the 19th century, who formulated basic principles of hemodynamics, such as Poiseuille's law, which provided the conceptual foundation for experimental studies of CBF regulation. Targeted research studies in coronary physiology began in earnest around the turn of the 20th century. Despite reliance on crude experimental techniques, the pioneers in coronary physiology made groundbreaking discoveries upon which our current knowledge is predicated. Further advances in coronary physiology were facilitated by technological developments, including methods to measure phasic CBF and its regional distribution, and by biochemical discoveries, including endothelial vasoactive molecules and adrenergic receptor subtypes. The authors recognize the invaluable contribution made by basic scientists toward the understanding of CBF regulation, and the enormous impact that this fundamental information has had on improving clinical diagnosis, decision-making, and patient care.

Right ventricle: current knowledge of echocardiographic evaluation of this "forgotten" chamber

In the past the right ventricle (RV) has been traditionally regarded as a simple conduit between the venous system and the pulmonary circulation and it has aroused little interest in both clinical and echocardiographic cardiologists to such an extent that it has been defined as the "forgotten chamber." Subsequently it was clearly shown that the right heart (RH) plays an important physiologic role in cardiac activity, and that congenital or acquired alterations in its structure and function have an important prognostic value. Aim of this review is to shed the light on the echocardiographic approach to this cardiac chamber. In this narrative review we critically explored the most recent literature on this topic using PubMed and Medline and examining the most recent guidelines on the echocardiographic approach to the RV. Echocardiographic approach to RV presents some technical difficulties, which stem from the position of the RV inside the thorax and around the LV and from its particular anatomy, which precludes geometric assumptions. However, RV may now be evaluated quantitatively and qualitatively in many ways, and some new methods can partially overcome some of the limits imposed by its complex anatomy, thereby yielding a quantitative evaluation. Furthermore, due to the wide range of pathologies which may involve the RV a disease-oriented approach should be considered in the echocardiographic investigation of right heart disease.

Hyperviscosity syndromes; hemorheology for physicians and the use of microfluidic devices

PURPOSE OF REVIEW

Hyperviscosity syndromes can lead to significant morbidity and mortality. Existing methods to measure microcirculatory rheology are not readily available and limited in relevance and accuracy at this level. In this review, we review selected hyperviscosity syndromes and the advancement of their knowledge using microfluidic platforms.

RECENT FINDINGS

Viscosity changes drastically at the microvascular level as the physical properties of the cells themselves become the major determinants of resistance to blood flow. Current, outdated viscosity measurements only quantify whole blood or serum. Changes in blood composition, cell number, or the physical properties themselves lead to increased blood viscosity. Given the significant morbidity and mortality from hyperviscosity syndromes, new biophysical tools are needed and being developed to study microvascular biophysical and hemodynamic conditions at this microvascular level to help predict those at risk and guide therapeutic treatment.

SUMMARY

The use of 'lab-on-a-chip' technology continues to rise to relevance with point of care, personalized testing and medicine as customizable microfluidic platforms enable independent control of many in vivo factors and are a powerful tool to study microcirculatory hemorheology.

The Physiology of Oxygen Transport by the Cardiovascular System: Evolution of Knowledge

The heart, vascular system, and red blood cells play fundamental roles in O₂ transport. The fascinating research history that led to the current understanding of the physiology of O₂ transport began in ancient Egypt in 3000 BC, when it was postulated that the heart was a pump serving a system of distributing vessels. Over 4 millennia elapsed before William Harvey (1578-1657) made the revolutionary discovery of blood circulation, but it was not until the 20th century that a lucid and integrative picture of O₂ transport finally emerged. This review describes major research achievements contributing to this evolution of knowledge. These achievements include the discovery of the systemic and pulmonary circulations, hemoglobin within red blood cells and its ability to bind O₂, and diffusion of O₂ from the capillary as the final step in its delivery to tissue. The authors also describe the classic studies that provided the initial description of the basic regulatory mechanisms governing heart function (Frank-Starling law) and the flow of blood through blood vessels (Poiseuille's law). The importance of technical advances, such as the pulmonary artery catheter, the blood gas analyzer and oximeter, and the radioactive microsphere technique to measure the regional blood flow in facilitating O₂ transport-related research, is recognized. The authors describe how religious and cultural constraints, as well as superstition-based medical traditions, at times impeded experimentation and the acquisition of knowledge related to O₂ transport.

Right Heart Catheterization-Background, Physiological Basics, and Clinical Implications

The idea of right heart catheterization (RHC) grew in the milieu of modern thinking about the cardiovascular system, influenced by the experiments of William Harvey, which were inspired by the treatises of Greek philosophers like Aristotle and Gallen, who made significant contributions to the subject. RHC was first discovered in the eighteenth century by William Hale and was subsequently systematically improved by outstanding experiments in the field of physiology, led by Cournand and Dickinson Richards, which finally resulted in the implementation of pulmonary artery catheters (PAC) into clinical practice by Jeremy Swan and William Ganz in the early 1970s. Despite its premature euphoric reception, some further analysis seemed not to share the early enthusiasm as far as the safety and effectiveness issues were concerned. Nonetheless, RHC kept its significant role in the diagnosis, prognostic evaluation, and decision-making of pulmonary hypertension and heart failure patients. Its role in the treatment of end-stage heart failure seems not to be fully understood, although it is promising. PAC-guided optimization of the treatment of patients with ventricular assist devices and its beneficial introduction into clinical practice remains a challenge for the near future.

Systemic milieu and age-related deterioration

Aging is a fundamental biological process accompanied by a general decline in tissue function and an increased risk for age-related disease. The risk for cardiovascular, stroke, cancer, and neurodegenerative diseases significantly increases with aging, especially in people aged 60 years and older in the USA. Although the cellular and molecular mechanisms underlying aging and age-related disease are beginning to be unraveled, the role of the systemic milieu remains unknown. Recent studies have shown that systemic factors in young blood can revise age-related impairments and extend organismal lifespan, suggesting that the systemic milieu contains pro-aging and rejuvenating factors that play a critical role in the health and aging phenotype. In this review, we summarize the current knowledge of systemic milieu changes during the aging process and its link to age-related deterioration.

Genomic translational research: Paving the way to individualized cardiac functional analyses and personalized cardiology

For most of Medicine's past, the best that physicians could do to cope with disease prevention and treatment was based on the expected response of an average patient. Currently, however, a more personalized/precise approach to cardiology and medicine in general is becoming possible, as the cost of sequencing a human genome has declined substantially. As a result, we are witnessing an era of precipitous advances in biomedicine and bourgeoning understanding of the genetic basis of cardiovascular and other diseases, reminiscent of the resurgence of innovations in physico-mathematical sciences and biology-anatomy-cardiology in the Renaissance, a parallel time of radical change and reformation of medical knowledge, education and practice. Now on the horizon is an individualized, diverse patient-centered, approach to medical practice that encompasses the development of new, gene-based diagnostics and preventive medicine tactics, and offers the broadest range of personalized therapies based on pharmacogenetics. Over time, translation of genomic and high-tech approaches unquestionably will transform clinical practice in cardiology and medicine as a whole, with the adoption of new personalized medicine approaches and procedures. Clearly, future prospects far outweigh present accomplishments, which are best viewed as a promising start. It is now essential for pluridisciplinary health care providers to examine the drivers and barriers to the clinical adoption of this emerging revolutionary paradigm, in order to expedite the realization of its potential. So, we are not there yet, but we are definitely on our way.

A brief history of topographical anatomy

This brief history of topographical anatomy begins with Egyptian medical papyri and the works known collectively as the Greco-Arabian canon, the time line then moves on to the excitement of discovery that characterised the Renaissance, the increasing regulatory and legislative frameworks introduced in the 18th and 19th centuries, and ends with a consideration of the impact of technology that epitomises the period from the late 19th century to the present day. This paper is based on a lecture I gave at the Winter Meeting of the Anatomical Society in Cambridge in December 2015, when I was awarded the Anatomical Society Medal.

Linking Genes to Cardiovascular Diseases: Gene Action and Gene-Environment Interactions

A unique myocardial characteristic is its ability to grow/remodel in order to adapt; this is determined partly by genes and partly by the environment and the milieu intérieur. In the "post-genomic" era, a need is emerging to elucidate the physiologic functions of myocardial genes, as well as potential adaptive and maladaptive modulations induced by environmental/epigenetic factors. Genome sequencing and analysis advances have become exponential lately, with escalation of our knowledge concerning sometimes controversial genetic underpinnings of cardiovascular diseases. Current technologies can identify candidate genes variously involved in diverse normal/abnormal morphomechanical phenotypes, and offer insights into multiple genetic factors implicated in complex cardiovascular syndromes. The expression profiles of thousands of genes are regularly ascertained under diverse conditions. Global analyses of gene expression levels are useful for cataloging genes and correlated phenotypes, and for elucidating the role of genes in maladies. Comparative expression of gene networks coupled to complex disorders can contribute insights as to how "modifier genes" influence the expressed phenotypes. Increasingly, a more comprehensive and detailed systematic understanding of genetic abnormalities underlying, for example, various genetic cardiomyopathies is emerging. Implementing genomic findings in cardiology practice may well lead directly to better diagnosing and therapeutics. There is currently evolving a strong appreciation for the value of studying gene anomalies, and doing so in a non-disjointed, cohesive manner. However, it is challenging for many-practitioners and investigators-to comprehend, interpret, and utilize the clinically increasingly accessible and affordable cardiovascular genomics studies. This survey addresses the need for fundamental understanding in this vital area.

Galen, father of systematic medicine. An essay on the evolution of modern medicine and cardiology

Galen (129-217) was the ultimate authority on all medical subjects for 15 centuries. His anatomical/physiological concepts remained unchallenged until well into the 17th century. He wrote over 600 treatises, of which less than one-third exist today. The Galenic corpus is stupendous in magnitude; the index of word-entries in it contains 1300 pages. Galen's errors attracted later attention, but we should balance the merits and faults in his work because both exerted profound influences on the advancement of medicine and cardiology. Galen admonished us to embrace truth as identified by experiment, warning that everyone's writings must be corroborated by directly interrogating Nature. His experimental methods' mastery is demonstrated in his researches, spanning every specialty. In his life-sustaining schema, the venous, arterial, and nervous systems, with the liver, heart, and brain as their respective centers, were separate, each distributing through the body one of three pneumata: respectively, the natural, the vital, and the animal spirits. He saw blood carried both within the venous and arterial systems, which communicated by invisible "anastomoses," but circulation eluded him. The "divine Galen's" writings, however, contributed to Harvey's singular ability to see mechanisms completely differently than other researchers, thinkers and experimentalists. Galen was the first physician to use the pulse as a sign of illness. Some representative study areas included embryology, neurology, myology, respiration, reproductive medicine, and urology. He improved the science and use of drugs in therapeutics. Besides his astounding reputation as scientist-author and philosopher, Galen was deemed a highly ethical clinician and brilliant diagnostician.

Historical continuity in the methodology of modern medical science: Leonardo leads the way

Early modern medical science did not arise ex nihilo, but was the culmination of a long history stretching back through the Renaissance, the Middle Ages, Byzantium and Roman times, into Greek Antiquity. The long interval between Aristotle and Galen and Harvey and Descartes was punctuated by outstanding visionaries, including Leonardo, the ultimate Renaissance man. His attitude and mindset were based on Aristotelian pursuit of empirical fact and rational thought. He declared himself to be a "man without letters" to underscore his disdain for those whose culture was only mnemonics and philosophical inferences from authoritative books. Leonardo read the Book of Nature with the immense curiosity of the pioneering scientist, ushering in the methodology of modern medical science with help from forerunners. He left no publications, but extensive personal Notebooks: on his scientific research, hydrodynamics, physiological anatomy, etc. Apparently, numerous successors availed themselves of his methodologies and insights, albeit without attribution. In his Notebooks, disordered and fragmentary, Leonardo manifests the exactitude of the engineer and scientist, the spontaneous freshness of one speaking of what he has at heart and that he knows well. His style is unrefined, but intensely personal, rich with emotion and, sometimes, poetic. Leonardo, the visionary anatomist, strived consistently not merely to imitate nature by depicting body structures, but to perceive through analysis and simulations the intimate physiologic processes; i.e., the biomechanics underlying the workings of all bodily organs and components, even the mysterious beating heart. It is fitting to regard him as the first modern medical scientist.