Lyme Carditis is heart disease which is caused secondary to infection with lyme bacteria. Borreliosis is the most common tickborne disease in the United States. It is caused by the spirochete Borrelia burgdorferi, and is transmitted by the common deer tick.
The species of deer tick varies by location with Ixodes scapularis being found in the mid-Atlantic states and Ixodes pacificus on the West Coast. In 2009, the federal Centers for Disease Control and Prevention reported 29,959 cases in the contiguous 48 states. It has been widely suggested the actual number of cases is more than 10 times this official figure. This would mean that almost 300,000 people across the USA have had been infected with lyme disease in 2009. This is an extraordinarily high number of cases, making this disease an epidemic.
Of those infected, approximately 8-10 percent will develop cardiac manifestations. Cardiac involvement typically occurs during the second (early disseminated) phase of the infection, weeks to months after the tick bite or initial infection, at a mean of 21 days after the development of erythema migrans (EM) (Rostoff et al, 2009).
The carditis can occur at the same time as the musculo-skeletal and neurological symptoms, however it may occur very early on (4 days) or even very late (7 months) after the tick bite or EM (Fish et al, 2008).
Biopsies of heart tissue in patients with this problem have shown spirochetes within the heart tissues (Reznick et al, 1986, Hajjar and Kradin, 2002).
They have also indicated inflammation within the endocardium, mycocardium, epicardium and pericardium.
Lymphocyte and monocyte white blood cell infiltration is also commonly seen.
Lyme Carditis may present with symptoms ranging from palpitations, chest pain or dyspnea (shortness of breath), lightheadedness, fatigue and fainting.
The carditis is typically present along with other signs of lyme disease (EM, arthritis, or neurological signs) but it may also be the only sign of the disease.
Cardiac Conduction Abnormalities
Cardiac conduction abnormalities are the most common form of lyme carditis.
They can range from asymptomatic first-degree heart block to complete heart block.
When cardiac involvement does occur, it is not uncommon to have mild and self-limited myocardial involvement. This manifests as subtle and nonspecific ST-T wave abnormalities on the ECG.
In a study of 105 cases of lyme carditis, 49% had complete heart block, while 16% had second degree AV block, and 12% had first degree AV block (Van der Linde, 1991, Fish et al, 2008).
The diagnosis of Lyme carditis can be relatively straightforward when new onset conduction abnormalities occur simultaneously with other signs and symptoms of disseminated Lyme disease, as was the case with this patient. If the cardiac manifestations occur in isolation, however, a high index of suspicion is necessary to make the diagnosis. Eliciting a history of tick exposure, erythema migrans rash, or outdoor activities in an endemic area is important when considering the diagnosis.
Lyme carditis may also manifiest as myopericarditis. This occurs when the Borrelia bacteria invades into heart tissue, following which the immune system tries to attack it by sending immune cells into the heart to kill the parasite. The influx of these immune cells causes the heart to swell leading to inflammation. The swelling of the heart can affect the ability of the heart to beat properly. In some cases, even after the parasite has been killed, the immune system continues to overreact, causing the heart to remain swollen. Myocarditis has been shown to occur in up to 10% of cases of Lyme carditis.
Congestive Heart Failure
If Lyme disease remains untreated for a long time, some evidence suggests it may slowly cause heart failure, which is also known as cardiomyopathy. It has been shown by some studies to occur in up to 5% of those suffering from Lyme carditis.
In this condition the heart becomes dilated and its contractile strength is weakened.
Symptoms of cardiomyopathy include: fatigue, shortness of breath, orthopnea (shortness of breath when laying flat), nocturnal shortness of breath, and edema or swelling of the feet, legs or abdomen.
Recent reports suggest that B. burgdorferi may, in some cases, be a cause of chronic cardiomyopathy in patients with no prior evidence of Lyme disease.
Some studies have found that patients infected with Lyme disease tend to have a higher incidence of cardiomyopathy than uninfected patients, reports the" Candian Journal of Cardiology."
It is believed that the ongoing damage to the cardiac tissue caused by the Lyme bacteria slowly weakens the ability of the heart to pump blood properly.
The diagnosis of Lyme carditis can often be simple when new onset conduction abnormalities occur simultaneously with other signs and symptoms of disseminated Lyme disease.
If the cardiac manifestations occur in isolation, it is up to the doctor to have a high index of suspicion that lyme borrelia bacteria could well be the cause of the of the carditis.
Eliciting a history of tick exposure, erythema migrans rash, or outdoor activities in an endemic area is important when considering the diagnosis.
Treatment of Lyme Disease
Once the diagnosis of Lyme carditis is made, antibiotics effective against Borrelia burgdorferi are often the first line of treatment initiated.
Antibiotics can be very effective very early in the disease process, however for chronic lyme disease there is still much controversy over their effectiveness to effectively treat this condition.
The Infectious Diseases Society of America recommends oral therapy with doxycycline or amoxicillin for asymptomatic 1st or 2nd degree heart block.
However, there is no evidence that treatment with antibiotics alters the course of the conduction abnormalities seen in Lyme carditis.
The prognosis for patients with Lyme disease and cardiac involvement is very good. Most conduction abnormalities will resolve within three to six days. Occasionally a persistent 1st degree AV block persists for several months after treatment, but these are typically well tolerated and also will resolve spontaneously. Very rarely, patients can have a persistent high-grade block that necessitates pacemaker placement.
Lyme carditis often can present a challenging diagnostic dilemma, particularly when the cardiac manifestations of this infection present in isolation.
It is important therefore to make sure the patient is thoroughly interviewed and examined focusing on risk factors and subtle sings and symptoms combined with a high index of suspicion in order to make a definitive diagnosis of Lyme carditis.