Larry Langdon
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Lyme Carditis

Lyme Carditis

Lyme carditis has been recorded in 1%-5% of patients diagnosed with Lyme disease. Conduction system abnormalities affecting the atrioventricular (AV) node are the most common manifestations. Early detection and antibiotic therapy are keys to reducing the risk for cardiovascular problems, avoiding sequelae, and shortening the disease's duration. This activity examines the diagnosis and treatment of Lyme carditis, emphasizing the importance of a multidisciplinary team in assessing and treating individuals with this illness.

In the United States, Lyme disease is the most frequent tick-borne sickness. It is a multisystem disease induced by a Borrelia burgdorferi infection. Carditis is one of the consequences, which affects between 1% and 10% of all patients with Lyme disease and develops within weeks to months of the illness. It appears in the early disseminated stage of the disease, which is the second phase. Conduction system abnormalities affecting the AV node are the most common manifestations. This causes various degrees of cardiac block, which in some circumstances necessitates the implantation of a temporary pacemaker.

Myocarditis, endocarditis, valvular heart disease, pericarditis, and myopericarditis are some of the other manifestations. Such diseases, on the other hand, are less common than conventional conduction system anomalies.

 

What causes Lyme disease?

Lyme disease is caused by the spirochete Borrelia burgdorferi (B. burgdorferi), which was named after Dr. Willy Burgdorfer, a microbiologist who discovered it in 1982. Mice, chipmunks, and other small mammals are natural reservoirs for the spirochete. Although deer are not adequate hosts for B. burgdorferi, they play a crucial role in the life cycle of the spirochete's vector, the Ixodes tick. By feeding on an infected animal, this tick carries B. burgdorferi, which it can then pass on to a human during a blood meal.

The Epidemiology

In the United States, about 30,000 cases of Lyme disease are reported each year; however, the true number could be substantially higher.

In 2015, 95% of cases were found in the Northeast, mid-Atlantic, and upper Midwest areas, with males aged 5-9 and 45-59 years being the most affected groups.

Lyme disease is most typically diagnosed between March and October, with 60% of cases occurring in June and July.

In the United States, cardiovascular symptoms are present in about 1.5%-10% of reported cases. Cases have also been discovered to be more common among young adult males, with a male-to-female ratio of approximately 3:1.

 

What happens in Lyme carditis?

After a tick bite, B. burgdorferi replicates at the site of its inoculation. The innate and adaptive cellular immune responses emerge locally at the site of spirochete entry during a period of a few days to a month after this incidence. Following these events, the spirochete travels to other tissues, including the central nervous system, eye, muscle, liver, spleen, and heart, with the support of various proteins and other chemicals found in the body.

Before and during the spread of the organism, the immune response is activated. To combat the invasion, the body first activates B-cell clones, which leads to an increase in IgM levels. Complement fixation and opsonization, as well as bactericidal death, are induced by the synthesis of IgG directed against distinct components of B. burgdorferi weeks to months later.

The specific mechanism that causes cardiac symptoms is still unknown. The defects that induce AV block appear to be caused by an autoimmune inflammatory response to spirochetes found in heart tissue. Cross-reactive IgM antibodies have the potential to react with heart tissue, resulting in damage and functional problems. According to researchers, there is also a substantial link among the number of spirochetes in cardiac tissue, myocardial inflammation, and the severity of conduction problems.

Even less is known about the pathophysiologic events that lead to Lyme endocarditis. Because tissue samples rarely contain bacteria, diagnostic confirmation must rely on other methods such as serologic testing and polymerase chain reaction (PCR).

 

Microscopic changes that occur in Lyme carditis

An interstitial inflammatory infiltration containing lymphocytes, histiocytes, and plasma cells is the most common histological finding. These infiltrates can be found all the way from the endocardium to the epicardium. Neutrophils and eosinophils don't show up in large numbers. Spirochetes have been seen using Warthin-Starry dye and immunohistochemistry in the epicardium, myocardium, and endocardium. B. burgdorferi, on the other hand, is not always identified. Bacteria seem absent in tissue samples in some cases of Lyme endocarditis, necessitating the use of alternative diagnostic procedures such as PCR to confirm the diagnosis.

In less severe cases or during the early phases of infection in people, the pathology and localization of infiltrates are unknown.

 

Clinical signs and symptoms of Lyme carditis

Lyme carditis should be examined in individuals who have the typical clinical signs of Lyme disease, which can happen at any time. The typical erythema migrans of the first phase, an early localized infection, can be identified. As the spirochete spreads, patients may experience nonspecific symptoms such as malaise, fever, chills, headache, myalgias, arthralgias, and dizziness. Cardiac signs are more likely to occur at this time. Lyme carditis is most commonly seen between June and December. The onset of symptoms can occur anywhere from 4 days to 7 months following the initial presentation (such as a rash), with a median of 21 days. Patients may exhibit the normal signs and symptoms of the disease at first; however, data indicate that many patients do not recall a tick bite, and the typical rash is seen in just 40% of patients with Lyme carditis. The most common symptoms include heart block, light-headedness, syncope, shortness of breath, palpitations, and/or chest discomfort, which are all associated with the most prevalent cardiac presentations.

AV conduction block is the most prevalent objective sign of Lyme carditis. The degree of AV block can change quickly, going from first degree to second degree or complete AV block and then back to first degree AV block in minutes.

Endocarditis with valve involvement, pericarditis, and myocarditis have all been linked to Lyme disease in the literature. These manifestations, on the other hand, are less common than the typical conduction delay anomalies.

Myopericarditis causes symptoms and electrocardiographic alterations that are comparable to those seen in acute coronary syndrome; 60% of patients will have T-wave inversion or ST-segment depression. Patients with elevated troponin levels and/or ST-segment elevation are uncommon. Valvular endocarditis is uncommon, but when it does occur, patients typically show signs of severe heart failure and cardiogenic shock.

 

How is Lyme carditis diagnosed?

The most common symptom of Lyme carditis is an AV block of varied degrees. If a patient exhibits the typical demographic and clinical signs, such as bradycardia, the next step is to carefully assess an electrocardiogram (ECG). In Lyme carditis, AV block can range from mild to total heart block, commonly known as third-degree AV block. The degree of AV block in these patients can change over minutes, hours, or days. Young men with early Lyme illness may benefit from an ECG because they are the demographic group most at risk for high-grade conduction abnormalities.

An improper association between the P wave and the QRS complex is referred to as an AV block. A consistent lengthening of the PR interval is indicative of a first-degree AV block (greater than 200 milliseconds). Second-degree AV block is characterized by a gradual extension of the PR interval followed by a nonconductive P wave (Mobitz type I) or by an unaltered PR interval followed by a single nonconductive P wave (Mobitz type II). There is no AV conduction in the third degree of the AV block, and the ECG displays a dissociation between P waves and QRS complexes. If heart block is the only symptom of Lyme carditis, no further testing is usually required.

When valvular disease or myocarditis is suspected, supplemental investigations are more relevant. An X-ray of the chest may reveal bilateral infiltrates or pleural effusions. When there are major conduction problems, echocardiography may reveal modest left ventricular or right ventricular dilatation. The ventricle size, on the other hand, is usually conserved. Myocarditis and myocardial infarction can be distinguished using echocardiography. Echocardiography indicates generalized ventricular hypokinesis in patients with symptoms and ECG changes consistent with an acute coronary syndrome, as opposed to isolated wall motion abnormalities found in myocarditis. If it's difficult to tell the difference between these two diseases, a cardiac MRI should be considered. As in acute coronary syndrome, cardiac MRI may show areas of enhanced epicardial contrast enhancement with little subendocardial involvement in myocarditis.

The isolation of the bacterium remains the gold standard for diagnosing infectious illnesses; however, B. burgdorferi, like some other spirochetes, cannot be cultured. Indirect serologic assays, as well as clinical suspicion and supportive laboratory and imaging studies, are used to make the diagnosis. Clinical suspicion alone may be enough to warrant antibiotic treatment in many circumstances. Many patients, however, may not show the conventional signs and symptoms, or their symptoms may be vague. It can be diagnosed using a two-step process of serologic testing. The first test to consider is an enzyme-linked immunosorbent assay (ELISA). A Western blot assay is necessary to confirm the diagnosis if IgM or IgG is positive or borderline. PCR has also been used to detect B. burgdorferi DNA in cardiac tissue. If Lyme disease is suspected as the cause of myocarditis or endocarditis and the serologic tests for this condition are negative or inconclusive, PCR can be performed.

 

How is Lyme carditis treated?

Despite the fact that some cases of Lyme carditis can recover without therapy, antibiotics are recommended to reduce the risk for cardiovascular problems, avoid sequelae, and decrease the disease's duration. Cephalosporins and tetracyclines are beta-lactam antibiotics that have been shown to be effective against B. burgdorferi. Oral amoxicillin or doxycycline for 14-21 days is recommended for mild to moderate illnesses.

Patients with more serious illnesses will need to be hospitalized. Patients must meet the following criteria for hospitalization:

1) Symptoms such as syncope, dyspnea, or chest pain are present.

2) A second- or third-degree AV block

3) First-degree AV block with a P-R interval larger than or equal to 300 ms

Although there is no evidence that parenteral antibiotics are preferable to oral antibiotics, parenteral antibiotics are the standard first-line treatment for hospitalized patients. The most commonly prescribed parenteral antibiotics are ceftriaxone or cefotaxime. Intravenous antibiotics should be continued until the second- or third-degree AV block is resolved or the P-R interval is less than 300 ms. Patients may continue oral medication for a total of 14-21 days after that.

In individuals with a combination of hemodynamic instability and high-grade second- or third-degree AV block, a temporary pacemaker is recommended. Once the high-degree heart block has been addressed, the pacemaker can be withdrawn.

Permanent pacemaker placement is not recommended because conduction problems are temporary, improve with antibiotic therapy, and are unlikely to return. Lyme carditis is listed as a class 3 indication in the 2008 American College of Cardiology/American Heart Association/Heart Rhythm Society Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities.

Patients with new-onset dilated cardiomyopathy may require antibiotic treatment because of the presence of seronegative Lyme carditis.

 

What is the prognosis of Lyme carditis?

The prognosis for Lyme carditis is generally favorable. It is frequently accompanied by conduction problems and is curable in most cases. Patients with third-degree heart block recover in 6 days on average when given adequate antibiotic treatment. There are several occurrences of permanent AV blocks; however, they are relatively uncommon. There have been stories of people dying because of severe myocarditis. However, this has only been documented in a few situations. There has been evidence of a relationship between Lyme disease and dilated cardiomyopathy.

What are the complications of Lyme carditis?

Although there have been reports of fatal cases, the mortality rate associated with Lyme carditis has always been low and has continued to fall as early detection and antibiotic treatment have been possible. In 2013, three deaths linked to Lyme carditis were reported in the press. Following the publication of this report, the CDC launched a follow-up examination of 1696 cases recorded between 1995 and 2013. Only two of the three instances were verified as Lyme carditis-related deaths, accounting for 0.001% of the total.

 

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