Lyme Carditis
Do you know Lyme carditis occurs in approximately one out of every hundred Lyme disease cases reported to CDC? Moreover, it has been reported in 1 to 5% of diagnosed patients with Lyme disease. It means the patients with Lyme disease have more chances to suffer from Lyme Carditis. Therefore, it is important to know all about this disease especially for the Lyme disease patients.
Today, we will dive deep into the epidemiology of Lyme Carditis and discuss the diagnosis techniques along with treatment to save patients' lives.
What is Lyme Carditis?
Lyme disease, caused by an infection transmitted through ticks, is the most common tick-borne illness worldwide. It can lead to carditis that typically occurs within weeks to months after infection. The main cardiac complication involves the atrioventricular (AV) node, resulting in various degrees of heart block, sometimes necessitating temporary pacemaker placement.
Other cardiac manifestations like myocarditis, endocarditis, valvular heart disease, pericarditis, and myopericarditis are less common. B. burgdorferi's natural reservoir includes small mammals, and its transmission to humans primarily occurs through the Ixodes tick, which relies on deer for its life cycle.
The disease is most prevalent in the Northeast, mid-Atlantic, and upper Midwest states, with approximately 30,000 reported cases annually in the US, though the actual number may be higher. It predominantly affects young adult males with a 3 to 1 male-to-female ratio.
The Link between Lyme Disease and Cardiac Involvement
After a tick bite, B. burgdorferi replicates at the entry site, triggering the body's immune response. Within days to a month, the innate and adaptive immune system reacts locally. The spirochete then spreads to various tissues, including the central nervous system, eye, muscle, liver, spleen, and heart, aided by certain proteins.
The immune response activates B-cell clones and raises IgM levels initially to combat the invasion. Later, IgG antibodies target B. burgdorferi components, leading to complement fixation and bactericidal killing.
Cardiac manifestations, like AV block, occur due to an autoimmune inflammatory response against spirochetes in the heart tissue. Cross-reactive IgM antibodies may cause tissue injury and functional abnormalities. The severity of conduction issues correlates with the number of spirochetes and myocardial inflammation.
Lyme endocarditis remains unclear as no microorganisms are usually found in tissue samples. Diagnosis is confirmed using serologic tests and PCR. The immune system's role in combating the spirochetes is vital, but it can also lead to cardiac complications, making timely diagnosis and management crucial.
Recognizing the Signs and Symptoms of Lyme Carditis
Lyme carditis should be considered in patients with typical Lyme disease clinical manifestations that occur in various stages. The early localized infection is marked by erythema migrans (only present 50% of the time), followed by generalized symptoms like malaise, fever, headache, flu-like symptoms, joint pain, and dizziness as the spirochete spreads.
The primary cardiac manifestation is atrioventricular (AV) conduction block, which can fluctuate rapidly from first degree to complete AV block and back to first degree AV block within minutes. Symptoms include heart block, light-headedness, syncope, shortness of breath, palpitations, and chest pain.
While cases of endocarditis, valvular involvement, pericarditis, and myocarditis linked to Lyme disease exist, they are less common than the characteristic conduction abnormalities. Prompt recognition of Lyme carditis is crucial for appropriate management.
Diagnosing Lyme Carditis: Tests and Procedures
Lyme carditis is diagnosed based on a combination of clinical suspicion, supporting laboratory tests, and imaging studies. The diagnosis can be challenging since the causative pathogen, Borrelia burgdorferi, cannot be cultured. Therefore, a two-step method of serologic testing is commonly used:
Electrocardiogram (ECG)
As mentioned in the initial information, careful evaluation of an ECG is essential in patients presenting with characteristic demographic and clinical manifestations, including bradycardia. AV block of varying degrees is a frequent manifestation of Lyme carditis, and the degree of AV block may change over time.
Chest X-ray
A chest X-ray may reveal bilateral infiltrates or pleural effusions, which can be suggestive of Lyme carditis or other cardiac involvement.
Echocardiography
Echocardiography may show mild left ventricular or right ventricular dilation in cases with predominant conduction abnormalities. However, most of the time, the ventricle size remains preserved. Echocardiography can also help differentiate Lyme carditis from other cardiac conditions such as myocarditis or myocardial infarction.
Cardiac MRI
In certain cases where differentiation between myocarditis and acute coronary syndrome is challenging, cardiac MRI can be considered. MRI may show specific patterns of contrast enhancement that can aid in distinguishing between these conditions.
Ultimately, the diagnosis of Lyme carditis relies on a combination of clinical findings, imaging studies, and laboratory tests. In cases where there is a high suspicion of Lyme carditis, antibiotic treatment may be initiated even before test results are available to prevent further complications. Early diagnosis and treatment are crucial to avoid potential serious cardiac complications associated with Lyme carditis.
Differential Diagnosis: Distinguishing Lyme Carditis from Other Heart Conditions
Distinguishing Lyme carditis from other heart conditions can be challenging due to the variability of clinical presentations and symptoms. However, there are specific features that can help differentiate Lyme carditis from other heart conditions. Here are some key points:
Demographic and Clinical Manifestations
Lyme carditis is more commonly observed in young men, especially those with early Lyme disease. The characteristic clinical manifestation is bradycardia, which may be accompanied by other symptoms such as fatigue, chest pain, and shortness of breath.
Electrocardiogram (ECG) Findings
The most important diagnostic tool for Lyme carditis is an ECG. AV block of varying degrees, ranging from first-degree to complete heart block (third-degree AV block), is the most frequent manifestation of Lyme carditis. The AV block may be transient and can change over minutes, hours, or days.
● First-degree AV block: Demonstrates a fixed prolongation of the PR interval (greater than 200 milliseconds).
● Second-degree AV block: Can be further classified into Mobitz type I (progressive prolongation of PR interval followed by a non-conductive P wave) and Mobitz type II (unchanged PR interval followed by a single non-conducted P wave).
● Third-degree AV block: No atrioventricular conduction, leading to dissociation between P waves and QRS complexes.
Supplementary Studies
Chest X-ray may show bilateral infiltrates or pleural effusions, while echocardiography may reveal mild left ventricular or right ventricular dilation in cases with predominant conduction abnormalities. However, most of the time, the ventricle size remains preserved.
Differentiating Myocarditis from Myocardial Infarction
Echocardiography and cardiac MRI may aid in differentiating myocarditis from acute coronary syndrome (myocardial infarction). In myocarditis, cardiac MRI may show areas of increased epicardial contrast enhancement with no subendocardial involvement, which is typically seen in acute coronary syndrome.
Complications and Risks Associated with Lyme Carditis
Lyme carditis, can lead to serious complications and, in some cases, fatal outcomes. However, the mortality rate associated with Lyme carditis is low, and it has declined further with improved early identification and antibiotic treatment. Reports indicate that the mortality rate is around 0.001% of all reported Lyme carditis cases.
Nevertheless, the condition can lead to varying degrees of atrioventricular block (AV block), ranging from first-degree to complete heart block, which can be life-threatening. Patients with Lyme carditis may experience bradycardia and other symptoms, necessitating careful monitoring and prompt treatment with antibiotics to prevent further cardiac complications.
Treatment Approaches for Lyme Carditis
The treatment of Lyme carditis aims to lower the risk of cardiovascular complications, prevent long-term sequelae, and shorten the duration of the disease. While some cases of Lyme carditis can resolve spontaneously, antibiotics are recommended to accelerate recovery and reduce the risk of complications. Beta-lactam antibiotics, such as cephalosporins and tetracyclines, have shown effectiveness against the causative agent, B. burgdorferi.
For mild to moderate Lyme carditis, oral amoxicillin or doxycycline is the usual treatment, administered for a duration of 14 to 21 days. However, more severe cases require hospitalization. Hospital admission criteria include the presence of symptoms like syncope, dyspnea, or chest pain, second or third-degree AV block, or first-degree AV block with a prolonged P-R interval greater than or equal to 300 ms.
In hospitalized patients, initial treatment with parenteral antibiotics is generally recommended. Ceftriaxone or cefotaxime are commonly used intravenous antibiotics. Intravenous antibiotics should be continued until resolution of the high-degree AV block or until the P-R interval shortens to below 300 ms. After this, patients may be transitioned to oral antibiotics to complete the full course.
Temporary pacemaker placement may be necessary in patients with hemodynamic instability and high-grade second or third-degree AV block. The pacemaker can be removed once the heart block has resolved. Although some cases of seronegative Lyme carditis have been reported, patients with new-onset dilated cardiomyopathy may also require treatment with antibiotics as a precaution.
Research and Advances in Lyme Carditis
Recent research by the University of Massachusetts Amherst team at the New England Regional Center of Vector-borne Diseases (NEWVEC) indicates that a medical therapy inhibiting cancer cell growth might be effective in treating Lyme disease. Led by vector-borne disease expert Stephen Rich, the study explored using LDH inhibitors, known for targeting certain cancers, to combat Borrelia burgdorferi, the bacterium causing Lyme disease.
The team found that LDH inhibitors, such as gossypol, AT-101, and oxamate, substantially impacted B. burgdorferi growth in laboratory experiments. These promising results have prompted further research, moving to in vivo experiments using mouse models to assess the inhibitors' effectiveness within a living host.
While the findings are encouraging, researchers emphasize that additional studies, including human clinical trials, are needed to validate the safety and efficacy of LDH inhibitors for Lyme disease treatment. Currently, antibiotics remain the primary treatment for Lyme disease and its complications. Nevertheless, this research opens up a potential new avenue for addressing tick-borne illnesses like Lyme disease and shows promise for future therapies. The work continues at NEWVEC, supported by funding from the CDC, aiming to make a significant impact on public health in regions heavily affected by Lyme infections.
Case Studies and Patient Stories of Lyme Carditis
Dr. Neil Spector
Dr. Neil Spector was a dedicated oncologist and researcher who spent his life helping others. He was not only an expert in cancer therapies but also became an advocate for Lyme disease after suffering from undiagnosed Lyme himself. Living in Florida, where Lyme disease was not well recognized, he struggled to get a proper diagnosis, leading to severe heart damage and diminished heart function.
After finally receiving a Lyme disease diagnosis and a heart transplant, Dr. Spector recognized the failures within the medical community regarding Lyme disease. He saw how patients were often dismissed and left without proper treatment due to a dogmatic approach to the illness. Dr, Neil recovered from Lyme Carditis. However, he passed away on Sunday, June 14, 2020.
Case Study
A 49-year-old male was presented with a two-week history of decreased exercise tolerance and a pulse rate of 40 beats per minute. He experienced pre-syncope with exertion and had a band-like vesicular rash on his thorax five months ago, diagnosed as shingles. An ECG revealed 3rd-degree AV block, which progressed to 2nd-degree Mobitz 2:1 AV block during hospitalization. He had recently traveled to rural England and developed symptoms three days after returning home. The patient was diagnosed with Lyme carditis and started on IV ceftriaxone. His heart rhythm improved to 1st-degree AV block within two days. He was discharged and advised to follow up with cardiology and infectious disease for further treatment.