Reprinted by permission from Primary Cardiology, April 1994.
Rama Garimella M.D., Leonard Moss D.O., Daniel Shindler M.D.
We became interested in the potential diagnostic utility of echocardiography in Lyme carditis when a young medical student with Lyme disease presented with erythema chronicum migrans, syncope, meningitis and an abnormal electrocardiogram demonstrating second degree Mobitz I heart block. This resolved over a period of several days with a residual first degree heart block. An echocardiogram revealed normal myocardial function. There was no evidence of pericardial effusion. The left ventricular function was normal. The only abnormal echocardiographic findings were a consequence of the conduction abnormalities.
In the original description of 20 patients with Lyme carditis (1) one patient had a pericardial friction rub on auscultation and another had a small pericardial effusion. Otherwise all patients tested had normal valvular structure, normal cardiac chamber dimensions and no hypertrophy. In another report (2) 4 patients were described. Three of the echocardiograms in these patients were normal. One showed slight hypokinesis of the proximal portion of the interventricular septum but there was no uptake on a gallium scan, therefore, no clinical evidence of inflammation.
There are two reported cases of death associated with lyme carditis. One did not undergo echocardiographic evaluation and was found dead after admission without evidence of agonal struggle, suggesting death due to arrhythmia. Although an echocardiogram was not performed, there was autopsy evidence of left ventricular hypertrophy and focal calcification at the base of his aortic valve. More importantly, there was also evidence of myocarditis involving myocardium, endocardium and pericardium. The findings are not specific for Lyme carditis but are certainly diagnosable to some extent by echocardiography.(3)
A second patient with fatal carditis presented a provocative finding which may or may not have been related to the Lyme disease. This patient had endodermal heterotopia (mesothelioma) of the atrio ventricular node.(4) The authors raised the possibility that this may somehow be related to the infection, and may account for the frequent occurrence of atrio ventricular block in Lyme disease. Inclusion cysts have been reported in autopsies of patients dying from heart block.(5) They, in essence, indicated the possibility of a pathological substrate for heart block in Lyme carditis. Recently it was actually possible to successfully excise a mesothelioma of the atrio ventricular node, making this a treatable entity if it is diagnosed.(6) In this particular patient it was an incidental finding during open heart surgery for a secundum atrial septal defect. However, with the increasing sophistication of echocardiographic tissue characterization techniques and with the availability of high resolution echo images from the esophagus it is conceivable that infiltration of the atrioventricular node by abnormal tissue may be diagnosable premortem.
It is already possible to diagnose in vivo the presence of myocardial fibrosis (reported in some patients with Lyme carditis) by the use of myocardial biopsy. It has also been shown that therapy will reverse some of this process. Echocardiographic tissue characterization techniques are being developed for this same purpose. One manufacturer already provides videodensitometry on ultrasound equipment for this purpose. Patients who live in endemic Lyme areas may present with ventricular arrhythmias.(7) Tissue characterization with echocardiography may, in the future, be useful in identifying cardiac involvement after the acute phase of the disease in these people.
Long term Lyme carditis has been associated with pericardial effusions as well as left ventricular hypertrophy (both diagnosable with the use of echocardiography).(8) Since many patients with Lyme disease are young, it is also worthwhile to comment on the known manifestations of this disease in children. In 32 randomly selected patients ages 1-17 presenting with Lyme disease, cardiac evaluation, including echocardiography, was performed. Cardiac evaluation was felt to be beneficial in diagnosing the presence of myocarditis and pericarditis both in symptomatic and asymptomatic children.(9)
Lyme Disease has been implicated as a possible etiologic agent in dilated cardiomyopathy.(12,13,14) It is, therefore, fitting to describe the multitude of information that can be gained about cardiac function using echocardiography combined with Doppler. Dilated cardiomyopathy is manifested by both left ventricular cavity dilatation as well as hypokinesis of the left ventricular walls. Since there are often electrocardiographic conduction abnormalities as well, the decreased overall left ventricular contractility may sometimes mimic regional wall motion abnormality. Digital techniques may be needed to generate a regional wall motion analysis. On color Doppler, one finds slow blood velocities with delayed displacement of the color from the mitral annulus to the left ventricular apex, giving the color pattern a puff like appearance. (15)
The mitral Doppler inflow velocity abnormalities associated with left ventricular dysfunction can be stratified into one of three patterns. In one pattern, there is acceleration of the inflow velocity through the mitral valve following atrial contraction with relatively slower velocity in the early phase of diastole. In an intermediate stage, there can actually be a normal mitral inflow pattern. This is referred to as pseudonormalization. The pulmonary venous inflow pattern however, may remain abnormal manifesting predominant filling in diastole rather than systole. Finally, the most ominous pattern is one of a brief inflow in early diastole with short deceleration of flows and little if any flow in late diastole. This pattern is ominous and has been associated with decreased longevity in patients with dilated cardiomyopathy.(16)
Additional findings not to be overlooked are the classic M- mode observations of decreased mitral leaflet excursion with increased diastolic separation of the anterior mitral leaflet away from the left ventricular septum. Left ventricular dilatation may distort the mitral annulus, giving rise to mitral insufficiency. Often, mitral insufficiency appears moderate rather than severe and the color flow jet appears central rather than impinging on one of the left atrial walls. Once the patient progresses to biventricular failure, there may be dilatation of the tricuspid annulus with tricuspid insufficiency as well. Eventually, one also may observe increases in tricuspid insufficiency velocities indicating evidence of pulmonary hypertension.
Since echocardiography is non-invasive it can be used serially to follow the evolution of any observed findings. Thus, although echocardiography does not provide pathognomonic findings in patients with Lyme carditis it is non-invasive and should be part of the initial evaluation. In our patient, the echocardiographic findings were related to the conduction abnormality rather than to actual myocardial involvement. As echocardiographic imaging improves and transesophageal echo probes get smaller, the tissue characteristics provided by high resolution echocardiography may be clinically useful in the evaluation of this important complication of Lyme disease.
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15. Shindler D,Shindler OI,Kostis JB. Color Doppler diastolic "smoke puff" in decreased left ventricular function, incidence and interobserver variability. Chest 96(2):201s, August 1989.
16. Pinamonti B,Lenarda A DI,Sinagara G,Camerini F and the Heart Muscle Group. Restrictive left ventricular filling pattern in dilated cardiomyopathy assessed by Doppler echocardiography: clinical, echocardiographic and hemodynamic correlations and prognostic implications. JACC 1993;22:808-15.
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