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.

Heart Failure With Preserved Ejection Fraction: A Comprehensive Review and Update of Diagnosis, Pathophysiology, Treatment, and Perioperative Implications.

Almost three-quarters of all heart failure patients who are older than 65 have heart failure with preserved ejection fraction (HFpEF). The proportion and hospitalization rate of patients with HFpEF are increasing steadily relative to patients in whom heart failure occurs as result of reduced ejection fraction. The predominance of the HFpEF phenotype most likely is explained by the prevalence of medical conditions associated with an aging population.

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

The heart, vascular system, and red blood cells play fundamental roles in O transport. The fascinating research history that led to the current understanding of the physiology of O 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 O transport finally emerged.

Right Ventricular Perfusion: Physiology and Clinical Implications.

Regulation of blood flow to the right ventricle differs significantly from that to the left ventricle. The right ventricle develops a lower systolic pressure than the left ventricle, resulting in reduced extravascular compressive forces and myocardial oxygen demand. Right ventricular perfusion has eight major characteristics that distinguish it from left ventricular perfusion: (1) appreciable perfusion throughout the entire cardiac cycle; (2) reduced myocardial oxygen uptake, blood flow, and oxygen extraction; (3) an oxygen extraction reserve that can be recruited to at least partially offset a reduction in coronary blood flow; (4) less effective pressure-flow autoregulation; (5) the ability to downregulate its metabolic demand during coronary hypoperfusion and thereby maintain contractile function and energy stores; (6) a transmurally uniform reduction in myocardial perfusion in the presence of a hemodynamically significant epicardial coronary stenosis; (7) extensive collateral connections from the left coronary circulation; and (8) possible retrograde perfusion from the right ventricular cavity through the Thebesian veins.

Isoflurane and the Coronary Steal Controversy of the 1980s: Origin, Resolution, and Legacy.

Isoflurane was introduced for general clinical use in North America in 1981. Shortly thereafter, in 1983, a study suggested that the anesthetic was a potent coronary vasodilator that could cause coronary steal and myocardial ischemia in patients with coronary artery disease. Myocardial ischemia results from small-vessel dilation which leads to increased blood flow to well-perfused myocardium and decreased blood flow to myocardium with borderline perfusion.

Preoxygenation: Physiologic Basis, Benefits, and Potential Risks.

Preoxygenation before anesthetic induction and tracheal intubation is a widely accepted maneuver, designed to increase the body oxygen stores and thereby delay the onset of arterial hemoglobin desaturation during apnea. Because difficulties with ventilation and intubation are unpredictable, the need for preoxygenation is desirable in all patients. During emergence from anesthesia, residual effects of anesthetics and inadequate reversal of neuromuscular blockade can lead to hypoventilation, hypoxemia, and loss of airway patency.

Cricoid Pressure Controversies: Narrative Review.

Since cricoid pressure was introduced into clinical practice, controversial issues have arisen, including necessity, effectiveness in preventing aspiration, quantifying the cricoid force, and its reliability in certain clinical entities and in the presence of gastric tubes. Cricoid pressure-associated complications have also been alleged, such as airway obstruction leading to interference with manual ventilation, laryngeal visualization, tracheal intubation, placement of supraglottic devices, and relaxation of the lower esophageal sphincter. This review synthesizes available information to identify, address, and attempt to resolve the controversies related to cricoid pressure.

MYOCARDIAL OXYGENATION DURING ACUTE NORMOVOLEMIC HEMODILUTION: IMPACT OF HYPOCAPNIC ALKALOSIS.

Background: Increases in myocardial blood flow preserve myocardial oxygenation during moderate acute normovolemic hemodilution. Hypocapnic alkalosis (HA) is known to cause coronary vasoconstriction and increase hemoglobin-oxygen affinity. We evaluated whether these effects would compromise myocardial oxygenation during hemodilution.