What Is Endocarditis? Causes, Symptoms, Risk Factors & Treatment: A Cardiologist's Guide

Most people have heard of a heart attack. Most people know what a stroke is. But endocarditis, an infection of the heart's inner lining  is something that flies completely under the public radar, often until it has already done serious damage.

Endocarditis can destroy a heart valve within days. It can send infected clots to the brain, the kidneys, and the lungs. It can mimic a dozen other illnesses for weeks before anyone suspects the heart is involved. And by the time it is correctly identified in patients who are delayed, the window for straightforward treatment has often already closed.

At Felix Hospital, recognized as one of the best cardiology hospitals in Noida, our team of senior cardiologists and cardiovascular surgeons manages infective endocarditis with the urgency and precision this condition demands. Our best cardiologists in Noida understand that endocarditis is not a condition that waits  and neither should the people who have it or are at risk of it.

This guide covers everything about what endocarditis is, what it looks like, who is most vulnerable, how it is diagnosed and treated, and what happens when it is missed.

What Is Endocarditis?

The heart is lined on the inside by a thin, smooth layer of tissue called the endocardium. It covers the inner walls of the heart chambers and, critically, the surfaces of the four heart valves, the mitral, aortic, tricuspid, and pulmonary valves  which open and close with every heartbeat to keep blood moving in the right direction.

Endocarditis is inflammation of the inner lining  almost always caused by infection.

When bacteria, fungi, or other microorganisms enter the bloodstream and reach the heart, they can adhere to the endocardial surface  particularly to the valves, where the mechanical stress of constant opening and closing creates small irregularities that act as attachment sites. Once attached, they multiply and trigger an immune response. The body's attempt to fight the infection produces deposits of platelets, fibrin, and bacteria clumped together  called vegetations  on the valve surface.

These vegetations are the hallmark of infective endocarditis. They are not benign growths. They interfere with valve function, they can break off and travel through the bloodstream as infected emboli  causing strokes, kidney damage, or abscesses anywhere in the body  and they progressively damage and destroy the valve they sit on.

Left untreated, infective endocarditis is almost universally fatal. Even with treatment, it remains one of the most serious infections in cardiovascular medicine  carrying an in-hospital mortality of 15 to 30 percent in many published series.

Types of Endocarditis

Endocarditis is not a single, uniform disease. It presents differently depending on the causative organism, the speed of onset, and the underlying condition of the heart valves.

Infective Endocarditis (IE)

This is the most common and clinically significant form. It is caused by a microbial infection, most often bacterial. Infective endocarditis is further categorized by its course:

• Acute Infective Endocarditis Caused by highly virulent organisms  most commonly Staphylococcus aureus (including MRSA). It progresses rapidly  over days  destroying valves, causing high fever, sepsis, and haemodynamic deterioration within a short time. Acute IE is a medical emergency from day one.

• Subacute Infective Endocarditis (SBE  Subacute Bacterial Endocarditis) Caused by less virulent organisms  classically Streptococcus viridans, which normally lives harmlessly in the mouth. It progresses slowly  over weeks to months  with insidious, low-grade symptoms that mimic many other conditions. This is the form that is most frequently diagnosed late, because for weeks it may look like a viral illness, fatigue syndrome, or early rheumatic disease.

Non-Infective (Sterile) Endocarditis

Less common but worth understanding:

• Libman-Sacks Endocarditis  associated with systemic lupus erythematosus (SLE). Non-infective vegetations form on both surfaces of the mitral valve. Not caused by bacteria but can mimic infective endocarditis.

• Marantic (Thrombotic) Endocarditis  seen in patients with advanced cancer or other chronic debilitating illnesses. Sterile vegetations form on valves, often as a paraneoplastic phenomenon, and can embolise.

• Rheumatic Endocarditis  a consequence of acute rheumatic fever following streptococcal throat infection. Inflammation of the valve leaflets  particularly the mitral valve  can lead to long-term scarring and rheumatic heart disease. Historically a leading cause of heart valve disease in India.

Prosthetic Valve Endocarditis (PVE)

A distinct and particularly serious category  endocarditis occurring on an artificial (prosthetic) heart valve. It is divided into:

• Early PVE  occurring within 60 days of valve surgery; usually caused by organisms introduced at the time of surgery

• Late PVE  occurring after 60 days; pathogenesis similar to native valve endocarditis

Prosthetic valve endocarditis is harder to treat, more likely to require surgery, and carries a higher mortality than native valve disease.

Right-Sided vs Left-Sided Endocarditis

Left-sided endocarditis (affecting the mitral and aortic valves) is far more common and generally more dangerous because these valves handle the systemic circulation.

Right-sided endocarditis (affecting the tricuspid valve) is strongly associated with intravenous drug use and typically presents with pulmonary complications  septic pulmonary emboli, lung abscesses  rather than systemic embolisation.

Causes of Endocarditis

The root cause of infective endocarditis is always the same: microorganisms entering the bloodstream (a process called bacteraemia) and successfully colonising the heart's inner surfaces.

Bacterial causes  the overwhelming majority:

• Staphylococcus aureus  the most common cause of acute endocarditis globally; associated with healthcare-related infections, IV drug use, skin infections, and indwelling catheters

• Streptococcus viridans group  historically the most common cause of subacute endocarditis; bacteria that normally inhabit the mouth and enter the bloodstream during dental procedures or poor oral hygiene

• Enterococcus faecalis  associated with gastrointestinal and urinary tract procedures; often affecting older adults

• Streptococcus bovis (gallolyticus)  associated with colorectal polyps and colon cancer; a diagnosis of endocarditis with this organism should prompt colonoscopy

• HACEK group organisms (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella)  slow-growing mouth bacteria causing a small but recognised proportion of cases

• Coagulase-negative staphylococci  particularly relevant in prosthetic valve endocarditis

Fungal endocarditis: Far less common but significantly more difficult to treat. Caused by Candida and Aspergillus species  most often in immunocompromised patients, those on prolonged IV nutrition, or those with prosthetic valves. Carries an extremely high mortality.

How do bacteria reach the heart?

Bacteraemia  the presence of bacteria in the bloodstream  occurs more frequently than most people realise:

• Dental procedures  particularly those involving manipulation of gum tissue

• Routine daily activities in people with poor oral hygiene  even vigorous toothbrushing or chewing food can cause transient bacteraemia

• Urological procedures  catheterisation, cystoscopy

• Gastrointestinal endoscopy with biopsy

• Skin infections  boils, cellulitis, infected wounds

• Intravenous drug injection  using non-sterile needles introduces skin bacteria directly into the bloodstream

• Indwelling venous catheters, pacemaker leads, dialysis access

• Respiratory tract procedures

In most people, transient bacteraemia is cleared by the immune system without any consequence. In people with vulnerable hearts  damaged valves, prosthetic valves, congenital abnormalities  the bacteria find a foothold and the infection takes hold.

Risk Factors for Endocarditis

Not everyone who develops bacteraemia gets endocarditis. The risk is substantially concentrated in specific groups whose hearts are more susceptible to colonisation.

High-risk cardiac conditions:

• Prosthetic heart valves  mechanical or bioprosthetic; the surface of an artificial valve is a more hospitable attachment site for bacteria

• Previous episode of infective endocarditis  prior infection leaves scarring that increases the risk of recurrence significantly

• Congenital heart disease  particularly unrepaired cyanotic defects, repaired defects with residual abnormalities near prosthetic material, and specific repaired defects in the first 6 months after surgery

• Rheumatic heart disease  scarred, damaged valves from prior rheumatic fever are more vulnerable; this is particularly relevant in India, where rheumatic heart disease remains common

• Degenerative valve disease  calcific aortic stenosis and mitral valve prolapse with regurgitation

• Bicuspid aortic valve  congenital two-leaflet valve with abnormal blood flow dynamics

Lifestyle and exposure-related risk factors:

• Intravenous drug use  the single most significant lifestyle risk factor; introduces skin flora directly into the bloodstream repeatedly

• Poor dental hygiene  chronic periodontal disease creates sustained, low-level bacteraemia

• Indwelling intravascular devices central venous catheters, haemodialysis catheters, pacemaker and defibrillator leads

• Recent dental or surgical procedures in high-risk individuals

Immune and systemic risk factors:

• Diabetes mellitus  impairs immune response and increases susceptibility to infection generally.

• Chronic kidney disease on dialysis  access creates repeated opportunities for bacteraemia.

• HIV infection with low CD4 counts  reduced immune competence.

• Chronic liver disease and cirrhosis.

• Immunosuppressive therapy  post-transplant patients, those on steroids or biological agents.

• Advanced age  immune function declines with age; degenerative valve disease is more common.

Signs and Symptoms of Endocarditis

Endocarditis is one of medicine's great mimics. It can look like the flu, like rheumatoid arthritis, like a urinary tract infection, like a stroke. This mimicry is the reason diagnosis is so frequently delayed  and why index of suspicion matters enormously in any patient with unexplained fever and a cardiac risk factor.

Classic Symptoms

Fever is the most consistent symptom; present in the vast majority of patients. In acute endocarditis, it is high and spiking. In subacute endocarditis, it may be low-grade  37.5 to 38.5°C  for weeks, with night sweats and chills. The persistence of fever that does not resolve with routine treatments should always raise alarm.

• Constitutional symptoms include fatigue, malaise, generalised weakness, poor appetite, and unintentional weight loss; particularly prominent in subacute presentations.

• Heart murmur  a new or changing heart murmur, caused by the vegetation disrupting normal valve function, is a critical clinical finding. A new regurgitant murmur in a febrile patient with a cardiac risk factor is endocarditis until proven otherwise.

• Joint and muscle pain  arthralgia and myalgia are common, which is why endocarditis is so frequently confused with viral illness or rheumatological conditions in its early stages.

Classic Physical Signs The "Peripheral Stigmata" of Endocarditis

These are findings caused by immune complex deposition and septic or aseptic emboli affecting small vessels throughout the body. They are seen in subacute endocarditis more than acute.

• Petechiae are small, pinpoint red spots that do not blanch on pressure; found on the skin, the conjunctivae (whites of the eyes), and the mucous membranes of the mouth. One of the more common peripheral signs.

• Splinter haemorrhages  thin, linear reddish-brown streaks under the fingernails or toenails, resembling splinters trapped beneath the nail. Caused by tiny emboli in the capillaries of the nail bed. Seen in up to 15 percent of patients.

• Osler's nodes have small, painful, tender lumps on the pads of the fingers and toes; caused by immune complex deposition. Their tenderness distinguishes them from Janeway lesions. Classic but not commonly  seen in approximately 10 to 25 percent of cases.

• Janeway lesions are flat, irregular, painless red or haemorrhagic spots on the palms of the hands and soles of the feet; caused by septic emboli. More common in acute Staphylococcus aureus endocarditis.

• Roth spots  oval, white-centred haemorrhages visible on the retina on eye examination; caused by immune complex vasculitis. Seen in approximately 5 percent of patients but highly specific when present.

• Clubbing of fingers  seen in longstanding endocarditis; indicates chronic disease.

Splenomegaly  an enlarged spleen, palpable on abdominal examination; common in subacute endocarditis because the spleen is chronically filtering septic material from the bloodstream.

Complications as Presenting Features

In many patients  particularly those with acute or advanced endocarditis  the presenting complaint is not fever or malaise, but a complication:

• Stroke or TIA  presenting as sudden weakness, speech disturbance, or facial drooping; caused by cerebral embolisation from cardiac vegetations

• Sudden visual loss  from retinal artery embolism

• Flank pain and haematuria  from renal infarction

• Sudden severe chest pain and breathlessness  from acute heart failure due to valve destruction, or from pulmonary embolism in right-sided disease

• Back pain  from vertebral osteomyelitis seeded by septic emboli

• Abdominal pain  from splenic infarction or mesenteric embolism

How Is Endocarditis Diagnosed?

Diagnosis of endocarditis rests on two pillars: blood cultures and echocardiography  formalised in the internationally used Modified Duke Criteria, which combines clinical, microbiological, and imaging findings to classify cases as definite, possible, or rejected endocarditis.

Blood cultures are the single most important investigation. At least three sets of blood cultures  from different venepuncture sites, at different times, should be drawn before any antibiotics are started. This matters enormously: blood cultures taken after antibiotics have been started are frequently negative, leaving the clinician treating blindly without knowing which organism is responsible or which antibiotics it is sensitive to.

Echocardiography:

• Transthoracic Echocardiography (TTE)  an ultrasound of the heart done through the chest wall. Useful for initial assessment and detecting large vegetations, valve dysfunction, and complications like pericardial effusion. Sensitivity is lower  around 60 to 70 percent  for small vegetations.
  
   

• Transoesophageal Echocardiography (TOE/TEE)  an ultrasound probe passed into the oesophagus gives far superior views of the heart valves  particularly the mitral valve and prosthetic valves. Sensitivity exceeds 90 percent. TOE is recommended in virtually all clinically suspected cases, particularly when TTE is negative but suspicion remains high, when prosthetic valves are involved, or when complications are suspected.
   

• Full blood count  typically shows elevated white cell count (leucocytosis), anaemia of chronic disease, and elevated inflammatory markers (CRP, ESR).

• Blood tests  elevated inflammatory markers (CRP, ESR, procalcitonin), anaemia, elevated creatinine (if renal involvement), haematuria on urinalysis.

• Chest X-ray  may show pulmonary infiltrates in right-sided endocarditis, cardiomegaly, or pulmonary oedema from valve dysfunction.

• CT scan  CT of the chest, abdomen, and brain is increasingly performed to look for embolic complications, silent cerebral infarcts, splenic infarcts, renal infarcts, or mycotic aneurysms. CT angiography of the aorta may be needed to assess for periannular extension of infection.

• PET-CT and Cardiac CT are newer imaging modalities that have significantly improved diagnostic sensitivity, particularly for prosthetic valve endocarditis and cardiac device infections, where echocardiography alone is less reliable.

• Dental review is often requested to identify the source of bacteraemia, particularly in streptococcal endocarditis.

Treatment Options for Endocarditis

Endocarditis requires prolonged, high-dose intravenous antibiotic therapy  this is not a condition treated with a short course of oral antibiotics. It is managed in hospital, with close monitoring of clinical response, cardiac function, and complications.

Medical Treatment  Intravenous Antibiotics

The duration of treatment depends on the organism, the valve involved, and whether native or prosthetic valve disease is present:

• Streptococcal native valve endocarditis  4 weeks of IV penicillin or ceftriaxone; may be shortened to 2 weeks with the addition of gentamicin in uncomplicated cases with sensitive organisms

• Staphylococcus aureus native valve endocarditis  4 to 6 weeks of IV flucloxacillin (or vancomycin if MRSA)

• Prosthetic valve endocarditis  minimum 6 weeks of IV antibiotics; regimens are more complex and often involve combination therapy

• Enterococcal endocarditis  4 to 6 weeks of combination therapy (typically ampicillin plus gentamicin, or ampicillin plus ceftriaxone)

• Fungal endocarditis  IV antifungal therapy (amphotericin B or echinocandins); almost always requires surgical valve replacement as antifungals alone are rarely curative

Culture-negative endocarditis  when blood cultures are negative (most commonly because antibiotics were given before cultures were taken, or due to fastidious organisms)  empirical broad-spectrum therapy is used while further diagnostic workup is pursued.

Surgical Treatment

Surgery is required in a significant proportion of endocarditis patients  approximately 40 to 50 percent during the acute hospitalization phase. The decision to operate, and its timing, is one of the most critical and nuanced judgements in cardiovascular medicine.

Indications for surgery in infective endocarditis:

• Heart failure  caused by severe valve regurgitation or obstruction from large vegetations; the most common surgical indication and generally requires urgent or emergency operation

• Uncontrolled infection  persistent fever and positive blood cultures despite appropriate antibiotic therapy; suggests a paravalvular abscess, resistant organism, or fungal infection

• Prevention of embolism  very large vegetations (greater than 10 mm), particularly on the mitral valve, in patients who have already had one embolic event, carry high enough risk of recurrent embolism that surgery is warranted

• Paravalvular extension  abscess formation around the valve annulus; indicates invasive disease and often necessitates extensive reconstruction

• Prosthetic valve endocarditis  particularly early PVE or cases with paravalvular leak or dehiscence

Surgical procedures may include:

• Valve repair  when the valve structure allows, repair is preferred over replacement; avoids the need for lifelong anticoagulation with mechanical prostheses

• Valve replacement  mechanical or bioprosthetic valve; choice depends on patient age, anticoagulation tolerance, and other factors

• Extensive debridement  of infected and necrotic tissue, particularly in paravalvular abscess

• Pacemaker or defibrillator lead removal  when cardiac device infection is involved

The timing of surgery  whether to operate in the acute phase of active infection or to delay  is individualised. Early surgery (within the first week) is associated with better outcomes when heart failure or uncontrolled infection is present. A delay risks further valve destruction and further embolic events.

Medications Used in Endocarditis

Beyond the primary antibiotic regimen, several other medications play important roles in management:

• Anticoagulants  the role of anticoagulation in endocarditis is complex and controversial. Patients with mechanical prosthetic valves who are already on anticoagulation present a particular challenge  stopping anticoagulation risks valve thrombosis, but continuing it during active endocarditis increases the risk of haemorrhagic transformation of cerebral emboli. Decisions are made individually, by the treating team.

• Diuretics  in patients with heart failure due to valve regurgitation, diuretics (furosemide) and vasodilators help manage fluid overload and reduce cardiac preload while decisions about surgery are made.

• Vasopressors  in patients with septic shock  which can occur in acute, aggressive endocarditis  vasopressors (noradrenaline) are used to maintain blood pressure in the intensive care unit.

• Antifungal agents  echinocandins (anidulafungin, micafungin) and amphotericin B for fungal endocarditis.

• Analgesics and antipyretics  for symptomatic relief of fever, joint pain, and general malaise.

• Rifampicin  added to the antibiotic regimen in prosthetic valve endocarditis after the bacteraemia is controlled; improves biofilm penetration.

Complications of Untreated Endocarditis

Endocarditis does not plateau. Without treatment, it progresses  and its complications are severe, irreversible, and frequently fatal.

• Embolic stroke is one of the most feared and common complications. Vegetations on left-sided valves  the mitral and aortic  are in the systemic circulation. When fragments break off, they travel to whatever artery is in their path  most catastrophically, the cerebral arteries. Stroke occurs in 15 to 35 percent of endocarditis patients. It can be haemorrhagic (due to a mycotic aneurysm rupturing) or ischaemic (due to vessel occlusion). The resulting neurological damage may be permanent.

• Acute heart failure develops when valve destruction reaches a tipping point  the valve can no longer close properly, causing severe regurgitation. The heart, unable to compensate, fails acutely. In the context of active infection, this is a haemodynamic emergency that carries very high mortality without emergency surgery.

• Paravalvular abscess  infection extending beyond the valve into the surrounding tissue  represents invasive, aggressive disease. It can cause complete heart block (when it involves the conducting system), fistula formation between cardiac chambers, and structural destruction that makes valve repair far more complex.

• Mycotic aneurysms  weaken spots in arterial walls caused by septic emboli seeding the vessel wall, forming aneurysms that can rupture. When this occurs in the brain  a cerebral mycotic aneurysm  rupture causes subarachnoid haemorrhage.

• Renal failure  from immune complex deposition in the kidney (glomerulonephritis), from septic renal emboli causing infarction, or from drug nephrotoxicity (aminoglycosides). Renal failure significantly worsens prognosis.

• Septic emboli to other organs  spleen (infarction, abscess), liver, mesentery (causing severe abdominal pain), and bone (vertebral osteomyelitis  causing back pain that may be the presenting complaint in some patients).

• Cardiac conduction abnormalities  new heart block or bundle branch block developing during endocarditis treatment signals paravalvular extension and is an indication for urgent surgical reassessment.

• Death  in-hospital mortality ranges from 15 to 30 percent in published series, with higher rates in staphylococcal endocarditis, prosthetic valve involvement, elderly patients, and those with embolic complications.

   

Prevention and Lifestyle Measures

Prevention of endocarditis is a conversation that belongs in every cardiology outpatient clinic  because the people most at risk are identifiable, and the preventive measures are largely straightforward.

Antibiotic Prophylaxis for High-Risk Patients

Current international guidelines recommend antibiotic prophylaxis before certain dental procedures specifically for patients in the highest-risk cardiac groups  those with prosthetic heart valves, a previous episode of infective endocarditis, certain congenital heart defects, and cardiac valve disease in heart transplant recipients.

The regimen is typically a single oral dose of amoxicillin (or clindamycin if penicillin-allergic) taken 30 to 60 minutes before the procedure. It is important to understand that prophylaxis is not recommended before every dental visit; it is reserved for procedures involving manipulation of the gingival (gum) tissue or the periapical region of the teeth.

If you are in a high-risk cardiac group, your cardiologist at Felix Hospital will advise you on when prophylaxis is appropriate. This conversation should happen proactively  not the morning before a dental appointment.

Oral Hygiene  Underestimated and Critical

For people with high-risk hearts, oral hygiene is not just a cosmetic concern. Chronic periodontal disease creates sustained, low-level bacteraemia every time the person chews. Regular brushing, flossing, and six-monthly dental check-ups reduce the bacterial burden in the mouth  and the frequency of oral bacteraemia  significantly.

Encouraging patients with valvular heart disease to maintain excellent oral hygiene is one of the most evidence-based endocarditis prevention strategies available. It costs nothing and requires only habit.

Avoiding IV Drug Use  and Harm Reduction

Right-sided endocarditis caused by intravenous drug use is, in many settings, the fastest-growing subgroup of endocarditis cases. The repeated introduction of skin bacteria directly into the bloodstream with non-sterile needles is an almost direct route to tricuspid valve infection.

Cessation of IV drug use eliminates this risk. For individuals who are not yet able to stop, harm reduction programmes, clean needle exchange, supervised injection facilities, addiction treatment  have a documented impact on endocarditis incidence and are a public health priority.

Skin and Wound Care

Any break in the skin  wounds, ulcers, skin infections  is a potential entry point for bacteria. Prompt treatment of skin infections, proper wound hygiene, and not allowing skin infections to be dismissed or self-treated inadequately reduces bacteraemia risk, particularly in high-risk patients.

Medical Device Care

Patients with indwelling venous catheters, pacemakers, or defibrillators should have these managed with strict aseptic technique at every interaction. Lines that are no longer necessary should be removed. Pacemaker lead infections are a specific and serious subtype of device-related endocarditis that requires complete lead extraction  a complex procedure.

Regular Cardiac Follow-Up

Patients with known valve disease  including those with rheumatic heart disease, bicuspid aortic valve, or mitral valve prolapse with regurgitation  should be under regular cardiology follow-up to monitor valve function over time. A valve that was mildly abnormal five years ago may be significantly more vulnerable today.

Regular echocardiography, guided by clinical assessment, allows the cardiologist to track progression and intervene surgically  with a valve repair or replacement done electively  before the valve becomes so diseased that it is one bacteraemia away from endocarditis.

At Felix Hospital, our cardiologists conduct structured valve disease follow-up programmes  ensuring that patients with known cardiac abnormalities are not lost to follow-up in the years between significant clinical events.

Cardiology Care at Felix Hospital, Noida

Felix Hospital, Sector 137, Noida is recognised as one of the best cardiology hospitals in Noida  with a full-service cardiac unit equipped to diagnose and manage infective endocarditis and its complications.

Our team of best cardiologists in Noida brings together the expertise of senior interventional cardiologists, cardiovascular surgeons, infectious disease specialists, and imaging experts  because endocarditis is a condition that no single specialist can manage in isolation. It demands a team.

Our cardiology facilities include:

• 24-hour cardiac emergency services  with round-the-clock echocardiography capability

• Transoesophageal Echocardiography (TOE)  the gold standard for endocarditis imaging

• Cardiac CT and advanced imaging  for embolic complication assessment and prosthetic valve evaluation

• Cardiac Intensive Care Unit (CICU)  for haemodynamically unstable patients

• Cardiovascular Surgery  for valve repair, valve replacement, and lead extraction

• Microbiology and infectious disease  for culture-guided antibiotic management and complex infection protocols

• Outpatient cardiology  for valve disease surveillance, antibiotic prophylaxis counselling, and endocarditis risk assessment

Whether you are experiencing symptoms that concern you, living with a high-risk cardiac condition and looking for a specialist to manage it proactively, or recovering from an endocarditis episode and needing ongoing cardiac care  the team at Felix Hospital is here.

Call Felix Hospital: +91 9667064100