Physical Address

304 North Cardinal St.
Dorchester Center, MA 02124

Microbiology of endocarditis

Introduction With significant changes to the epidemiology of infective endocarditis (IE) in recent years, it is important to highlight which pathogens are the major causes of this disease. In the United States, Staphylococcus aureus has overtaken Streptococcus species as the most common etiology for IE, contributing approximately 30% of all cases. This shift has resulted from a combination of increased use of prosthetic valves, cardiac devices…

General approach to the clinical diagnosis of endocarditis

Introduction The diagnosis of infectious endocarditis is quite often complex and may be among the most challenging diagnoses facing today's medical providers. Patients can present with a multitude of clinical signs and symptoms and existing diagnostic testing and criteria are imperfect. Although early diagnosis and intervention are clearly associated with improved outcomes, in nearly 25% of endocarditis cases the diagnosis is made >1 month after onset of…

Epidemiology and pathophysiology of infective endocarditis

Epidemiology Introduction The clinical features of infective endocarditis were first described in the 16th century by Jean François Fernel, a French physician who first introduced the term ‘physiology’ to describe the study of the function of living things [ ]. Over the next few centuries, through astute observations of human physiology and pathophysiology, several preeminent figures laid the foundations of our fundamental knowledge of infective endocarditis,…

IBC

You’re Reading a Preview Become a Clinical Tree membership for Full access and enjoy Unlimited articles Become membership If you are a member. Log in here

Hypertension – Origins

Questions 1 When did hypertension enter medical nosography as a disease? It all started in antiquity with the recognition of the pulse as a sign of life, death, and disease. The Mesopotamian epic of Gilgamesh (c. 2600 BCE) records the lament of its protagonist, Gilgamesh, at the death of his best friend, Enkidu, “I touch his heart but it does not beat at all.” How he…

Baroreflex Dysfunction

Questions 1 What is the baroreflex? The baroreflex is a critical mechanism in the homeostatic regulation of blood pressure. Blood pressure is monitored continually by receptors located in the carotid arteries, aorta, lungs, coronary arteries, and the splanchnic vasculature of the gut, termed “baroreceptors.” These receptors consist of mechanosensory neurons that form macroscopic “claws” that circumnavigate large arteries, and are activated when increased blood pressure causes…

Orthostatic Hypotension

Questions 1 What physiologic responses prevent blood pressure from decreasing acutely when we stand? After assuming the upright position, gravitational forces shift ∼700 mL of blood volume to the lower part of the body, mostly in the splanchnic vascular circulation. This fluid shift is detected by the baroreceptors in the carotid sinus and aortic arch This information is transmitted through the glossopharyngeal and vagus nerves to the…

Role of Device Therapy

Questions 1 What do we mean by device therapies in hypertension? Device therapies refers to interventions that are used to reduce blood pressure (BP). These interventions can be surgical, or with interventional angiographic procedures targeting the mechanism of hypertension. The device therapies that have undergone research in this area include Renal denervation Baroreceptor activation or modulation Central arteriovenous fistula (AVF) creation A brief summary of the…

Drug-Drug and Pharmacogenetic Interactions

Questions 1 What are the possible mechanisms by which medications or supplements affect antihypertensive medication effectiveness? The mechanisms by which medications or supplements may impact antihypertensive effectiveness include modulating the metabolism of the antihypertensive medication and activating molecular mechanisms which counteract the targeted blood pressure–lowering mechanisms. Drug metabolism is mediated, in part, by the cytochrome P450 proteins, which are monooxygenases which participate in activation, inactivation, and…

Alpha-2 Agonists

Questions 1 How do alpha-2 agonists reduce blood pressure? Norepinephrine activates the alpha-2 adrenergic receptor in the brain, which serves as a negative feedback mechanism to suppress the sympathetic nervous system. Drugs with alpha-2 agonist activity mimic this effect centrally, resulting in suppression of peripheral norepinephrine release and subsequently lowering blood pressure. As a result, efficacy of these drugs is reflected by the suppression of circulating…

Beta-Blockers

Questions 1 What is the clinical pharmacology of β-adrenergic receptor blockers? β-Adrenergic receptor blockers (beta-blockers) competitively inhibit the β-adrenergic receptors and by doing so act as antihypertensive drugs. Although the exact mechanisms through which these agents lower systemic blood pressure (BP) remain unclear, it is the blockade of the β 1 -adrenergic receptor that appears to be the predominant mechanism by which these drugs reduce heart…

Alpha Antagonists

Questions 1 How do alpha adrenergic receptors contribute to blood pressure regulation? Alpha adrenergic receptors are G protein coupled receptors (GPCR) that are found in various locations in the human body. In the context of hypertension their most important peripheral locations are on smooth muscle cells ( Table 36.1 and Fig. 36.1 ). There are two main types, alpha-1 and alpha-2, both of which have multiple subtypes. The…

Potassium-Sparing Diuretics

Questions 1 How do potassium-sparing diuretics work? Potassium-sparing diuretics block the reabsorption of sodium through the epithelial sodium channel (ENaC) in exchange for potassium in the connecting tubule (CNT) and collecting duct (CD). Traditional potassium-sparing diuretics (amiloride, triamterene) directly block ENaC, and others block the mineralocorticoid receptor (MR [e.g., spironolactone, eplerenone]). Because a major action of the MR is to increase ENaC activity, MR antagonism acts…

Loop and Thiazide Diuretics

Questions 1 What is the mechanism of action of thiazide diuretics? Thiazide diuretics act primarily by inhibiting the sodium chloride cotransporter (NCC) along the distal convoluted tubule, which is responsible for reabsorbing 5% to 10% of the filtered sodium load ( Fig. 34.1 ). They initially require secretion into the nephron lumen via organic anion transporters (OATs) along the proximal convoluted tubule (PCT). NCC inhibition occurs via…

Direct Vasodilators

Questions Direct smooth muscle arterial vasodilators 1 What is a direct smooth muscle arterial vasodilator? Direct arterial vasodilators are blood pressure–lowering medications characterized by a decrease in peripheral resistance mediated by relaxation of smooth muscle in arterioles. Two medications commonly recognized in this class include hydralazine and minoxidil. 2 What is the mechanism of action of direct arterial vasodilators? Hydralazine acts on the arterial vessels, causing…

Calcium Channel Blockers

Questions 1 How do calcium channel blockers exert their antihypertensive effect? Among the many calcium channels found throughout the body, the “L-type” remains the most clinically relevant. All calcium channel blockers (CCBs), whether classified as a dihydro pyridine (e.g., nifedipine, felodipine, amlodipine) or a nondihydropyridine (e.g., diltiazem, verapamil), bind this channel at various sites, thereby preventing cellular calcium entry. Calcium channel inhibitors lower blood pressure (BP)…

Angiotensin-Converting Enzyme Inhibitors and Angiotensin Receptor Blocker

Questions 1 Describe the mechanism of action of antiogensin-converting enzyme inhibitors and angiotensin receptor blockers? The renin-angiotensin-aldosterone system plays an essential role in the maintenance of blood pressure, and hence drugs that target this system are effective antihypertensive agents. In this system, the substrate, angiotensinogen, is cleaved by renin to generate angiotensin-I. Angiotensin-converting enzyme (ACE) converts angiotensin-I to angiotensin-II which then increases blood pressure through effects…

Blood Pressure Treatment Goals

Questions 1 Why is a treatment goal important for hypertension? Hypertension is the most important risk factor for cardiovascular disease (CVD) and stroke worldwide. Epidemiological studies demonstrate that blood pressure (BP) is continuously related to the risk of fatal stroke, ischemic heart disease (IHD), and noncardiac vascular disease well down into the normal range (beginning at 115/75 mm Hg). For example, a 20-mm Hg higher systolic blood…

Lifestyle Modifications for Hypertension Management

Questions 1 What is the role of lifestyle modifications in the treatment of hypertension? The 2017 American College of Cardiology/American Heart Association (ACC/AHA) Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults recommends lifestyle changes that can reduce systolic blood pressure (SBP) by approximately 4 to 11 mm Hg in patients with hypertension. These guidelines stress the importance of maintaining a healthy…

Hyperkalemia in Hypertension

Questions 1 Why is hyperkalemia important to understand in the management of individuals with hypertension? Hyperkalemia is one of the most common electrolyte disorders encountered and affects a disproportionate number of individuals with chronic hypertension. The incidence of hyperkalemia ranges from 1.9% to 38% among participants of prospectively conducted trials examining the effects of renin-angiotensin-aldosterone system (RAAS) inhibitors on blood pressure reduction. In many studies, higher…