Endocarditis-symptoms,diagnosis and treatment

Endocarditis-symptoms, diagnosis and treatment


  • Endocarditis is an inflammation of the endocardium or inner lining of the heart. Most of the time, endocarditis refers to an infection of the valves of the heart, often the mitral or aortic valve.
  • Two variations of infectious endocarditis have been described: acute and subacute. Each has distinct groups of possible causative agents.
  • Rarely, endocarditis can also be caused by vascular trauma or by circulating immune complexes in the absence of infectious agents.
  • The surgical innovation of prosthetic valves presents a new hazard for the development of endocarditis.
  • Patients with prosthetic valves can acquire acute endocarditis if bacteria are introduced during the surgical procedure; alternatively, the prosthetic valves can serve as infection sites for the subacute form of endocarditis long after the surgical procedure.
  • Because the symptoms and the diagnostic procedures are similar for both forms of endocarditis, they are discussed first; then the specific aspects of acute and subacute endocarditis are addressed.

 Signs and Symptoms

  • The signs and symptoms are similar for both types of endocarditis, except that in the subacute condition they develop more slowly and are less pronounced than with the acute disease.
  • Symptoms include fever, anemia, abnormal heartbeat, and sometimes symptoms similar to myocardial infarction(heart attack).
  • Abdominal or side pain is sometimes reported. The patient may look very ill and may have petechiae (small red-to-purple discolorations) over the upper half of the body and under the fingernails.
  • In subacute cases, an enlarged spleen may have developed over time; cases of extremely long duration can lead to clubbed fingers and toes.

Culture and Diagnosis

  • The diagnostic procedures for the two forms of endocarditis are essentially the same. One of the most important diagnostic tools is a high index of suspicion.
  • A history of risk factors, or behaviors, such as abnormal valves, intravenous drug use, recent surgery, or bloodstream infections, should lead one to consider endocarditis when the symptoms just described are observed.
  • Blood cultures, if positive, are the gold standard for diagnosis, but negative blood cultures do not rule out endocarditis.
  • If it is possible to obtain the agent, it is very important to determine its antimicrobial susceptibilities. In acute endocarditis, the symptoms may be magnified.
  • The patient may also display central nervous system symptoms suggestive of meningitis, such as stiff neck or headache.

Endocarditis-symptoms,diagnosis and treatment

Acute Endocarditis

  • Acute endocarditis is most often the result of an overwhelming bloodstream challenge with bacteria. Certain of these bacteria seem to have the ability to colonize normal heart valves.
  • Accumulations of bacteria on the valves (vegetations) hamper their function and can lead directly to cardiac malfunction and death.
  • Alternatively, pieces of the bacterial vegetation can break off and create emboli (blockages) in vital organs.
  • The bacterial colonies can also provide a constant source of blood-borne bacteria, with the accompanying systemic inflammatory response and shock.
  • Bacteria that are attached to surfaces bathed by blood (such as heart valves) quickly become covered with a mesh of fibrin and platelets that protects them from the immune components in the blood.

Causative Agents

 The acute form of endocarditis is most often caused by Staphylococcus aureus. Other agents that cause it are Streptococcus pyogenes, Streptococcus pneumoniae, and Neisseria gonorrhoeae, as well as a host of other bacteria. Each of these bacteria is described elsewhere in this book; all are pathogenic.

Transmission and Epidemiology

The most common route of transmission for acute endocarditis is parenteral—that is, via direct entry into the body. Intravenous or subcutaneous drug users have been a growing risk group for the condition. Traumatic injuries and surgical procedures can also introduce the large number of bacteria required for the acute form of endocarditis.

Prevention and Treatment

Prevention is based on avoiding the introduction of bacteria into the bloodstream during surgical procedures or injections. Untreated, this condition is invariably fatal. Recommended antibiotics are nafcillin or oxacillin with or without gentamicin. Alternatively, vancomycin + gentamicin can be used. High, continuous blood levels of antibiotics are required to resolve the infection because the bacteria exist in biofilm vegetations. In addition to the decreased access of antibiotics to bacteria deep in the biofilm, these bacteria often express a phenotype of lower susceptibility to antibiotics. Surgical debridement of the valves, accompanied by antibiotic therapy, is sometimes required.

Subacute Endocarditis

 Subacute forms of this condition are almost always preceded by some form of damage to the heart valves or by congenital malformation. Irregularities in the valves encourage the attachment of bacteria, which then form biofilms and impede normal function, as well as provide an ongoing source of bacteria to the bloodstream. People who have suffered rheumatic fever and the accompanying damage to heart valves are particularly susceptible to this condition.

Causative Agents

 Most commonly, subacute endocarditis is caused by bacteria of low pathogenicity, often originating in the oral cavity. Alpha-hemolytic streptococci, such as Streptococcus sanguis, S. oralis, and S. mutans, are most often responsible, although normal biota from the skin and other bacteria can also colonize abnormal valves and lead to this condition.

Transmission and Epidemiology

 Minor disruptions in the skin or mucous membranes, such as those induced by vigorous toothbrushing, dental procedures, or relatively minor cuts and lacerations, can introduce bacteria into the bloodstream and lead to valve colonization. The bacteria are not, therefore, transmitted from other people or from the environment. The average age of onset for subacute endocarditis has increased in recent decades from the mid- 20s to the mid-50s. Males are slightly more likely to experience it than females.

Prevention and Treatment

 The practice of prophylactic antibiotic therapy in advance of surgical and dental procedures on patients with underlying valve irregularities has decreased the incidence of this infection. When it occurs, treatment is similar to treatment for the acute form of the disease.

Septicemias

 Septicemia occurs when organisms are actively multiplying in the blood. Many different bacteria (and a few fungi) can cause this condition. Patients suffering from these infections are sometimes described as “septic.” One infection that should be considered in cases of aggressive septicemia, especially if respiratory symptoms are also present, is anthrax.

Signs and Symptoms

 Fever is a prominent feature of septicemia. The patient appears very ill and may have an altered mental state, shaking chills, and gastrointestinal symptoms. Often an increased breathing rate is exhibited, accompanied by respiratory alkalosis (increased tissue pH due to breathing disorder). Low blood pressure is a hallmark of this condition and is caused by the inflammatory response to infectious agents in the bloodstream, which leads to a loss of fluid from the vasculature. This condition is the most dangerous feature of the disease, often culminating in death.

Causative Agents

The vast majority of septicemias are caused by bacteria, and they are approximately evenly divided between gram positives and gram-negatives. Perhaps 10% are caused by fungal infections. Polymicrobial bloodstream infections increasingly are being identified in which more than one microorganism is causing the infection.

Pathogenesis and Virulence Factors

 Gram-negative bacteria multiplying in the blood release large amounts of endotoxin into the bloodstream, stimulating a massive inflammatory response mediated by a host of cytokines. This response invariably leads to a drastic drop in blood pressure, a condition called endotoxic shock. Gram-positive bacteria can instigate a similar cascade of events when fragments of their cell walls are released into the blood.

Endocarditis-symptoms,diagnosis and treatment


REFERENCES

  1. https://journals.lww.com/md-journal/fulltext/2003/07000/A_Clinical_Study_of_Culture_Negative_Endocarditis.5.aspx