The use of echocardiography in diagnosing culture-negative endocarditis

Utilization of echocardiography by internists and cardiologists: a comparative study

OBJECTIVE

To compare the utilization of echocardiography as a diagnostic tool by internists and cardiologists.

DESIGN

Retrospective study.

SETTING

Tertiary care university hospital.

METHODS

Indications and clinical utility of echocardiographic studies ordered by cardiologists (group A, n = 301) and internists (group B, n = 297) were compared by chart review. The two groups of patients were analyzed to determine if the studies detected new cardiac pathology and/or altered patient management.

RESULTS

The proportion of studies with abnormal results were similar in both groups (19% versus 14%, P > 0.05). The results of echocardiography, however, led to a change in management more often when the study was ordered by cardiologists (16% versus 10%, P < 0.05). A significantly greater proportion of studies were ordered for evaluation of valvular function by internists (44% versus 33%, P < 0.05). Echocardiography detected valvular abnormalities in a similar proportion of cases in groups A and B (14% versus 10%, P > 0.05). However, diagnostic yield was very poor when the study was performed in patients with suspected mitral valve prolapse in both groups. Cardiologists utilized echocardiography more often for evaluation of left ventricular function (35% versus 18%, P < 0.01) and in the setting of atherosclerotic heart disease for detecting wall motion abnormalities (14% versus 5%, P < 0.01).

CONCLUSION

Diagnostic yield of echocardiography is similar when ordered by internists and cardiologists. With the information obtained, management is altered in a slightly greater proportion of cases involving a cardiologist. This may be due to utilization of echocardiography more often for estimating left ventricular function and for detecting wall motion abnormalities by cardiologists.

Early identification of patients with native valve infectious endocarditis at risk for major complications by initial clinical presentation and baseline echocardiography

Early identification of a high risk patient subgroup with infective endocarditis which develops a major complication (emboli, congestive heart failure, surgery for valve replacement, or death) during hospitalization would reduce morbidity, mortality and cost. Thus, for 74 patients with native valve infective endocarditis with documented vegetation by transthoracic two-dimensional echocardiogram, we reviewed 67 variables: history (15), physical examination (9), hematology/miscellaneous (7), chest X-ray (2), electrocardiogram (4), transthoracic two-dimensional echocardiograms (15) and hospital course (15). There were 48 men and 26 women, ages 45 +/- 19 years: 35 intravenous drug abusers and 39 non-users. There were 32 mitral, 21 tricuspid, 20 aortic, and 1 pulmonic valve vegetations; mean vegetation size was 1.4 +/- 0.9 cm2. Over the course of their hospitalization, 14 patients died (19%), 27 developed congestive heart failure (36%), 27 had systemic emboli (36%), and 22 required surgery (30%). The incidence of complications (death, heart failure or embolic events) did not differ between the drug abusers and non-users. Initial complaint of dyspnea on admission predicted the subsequent development of heart failure (P < 0.001), and a pre-admission embolus predicted a second in-hospital embolus (P < 0.001). Left atrial size, ventricular systolic or diastolic dimension did not effect prognosis. Importantly, a vegetation > 1.8 cm2 was 100% specific but only 30% sensitive for predicting the development of a complication. Vegetation mobility, shape, and number of cusps involved were not predictive. However, aortic valve vegetations had significantly more complications than those on the mitral valve (P < 0.03). By discriminant function analysis, 87% of major complications were predicted with the patient profile of having aortic valve vegetation, dyspnea on admission, prolonged preadmission fever, and no history of drug abuse; 75% of patients who developed heart failure were predicted by their having aortic valve vegetation, dyspnea, hypotension (systolic < 90 mm Hg), and no history of drug abuse; and 77% of patients requiring surgery were predicted by their having larger vegetation size, rales, and leftward shift of white blood cells. Thus, in native valve bacterial endocarditis with transthoracic echocardiographic documented vegetations, non-drug abusers with aortic vegetations, preadmission prolonged fevers, dyspnea, emboli and larger sized vegetations are at high risk for developing a major complication during their hospitalization.

Value of transthoracic echocardiography in predicting embolic events in active infective endocarditis. Duke Endocarditis Service

The purpose of this study was twofold: (1) to determine interobserver variability of echocardiographic characteristics of vegetations in patients with infective endocarditis, and (2) to assess the value of these vegetation characteristics in predicting embolic events. Although echocardiography contributes to the diagnosis of patients with infective endocarditis, its prognostic role in predicting embolic events is controversial. The echocardiograms of 41 patients with infective endocarditis were independently reviewed by 4 echocardiographers blinded to the clinical data. If a vegetation was present, the following characteristics were analyzed: involved site, size, mobility, shape, and pedunculated or sessile attachment. Each echocardiographer also made a "gestalt" estimate of embolic risk based on these vegetation characteristics. Interobserver agreement on vegetation characteristics and their relation to embolic events was then determined using kappa statistics and logistic regression analysis. Interobserver agreement was 98% with regard to echocardiographic vegetation presence and 97% with regard to the involved site. Of the 30 patients in whom vegetations were observed, complete observer agreement was achieved with regard to size in 22 (73%), mobility in 17 (57%), shape in 11 (37%), and attachment in 12 (40%). Vegetations with a maximal diameter of > 10 mm were associated with a 50% incidence of embolic events, compared with a 42% incidence of emboli in patients with vegetations measuring < or = 10 mm. Interobserver variability was great with respect to vegetation shape, mobility, and attachment characteristics. Echocardiographic vegetation characteristics were not helpful in defining the risk of embolic complications in patients with endocarditis.

Immunoscintigraphy using technetium-99m-labeled anti-NCA-95 antigranulocyte antibodies as an adjunct to echocardiography in subacute infective endocarditis

OBJECTIVES

This study was performed to assess the clinical value of immunoscintigraphy in subacute infective endocarditis.

BACKGROUND

Radiolabeled granulocytes can reveal inflammatory lesions.

METHODS

Using technetium-99m-labeled anti-NCA-95 anti-granulocyte antibodies, planar scintigraphy and single-photon emission computed tomography of the thorax were performed in 72 consecutive patients with suspected endocarditis. Each patient also underwent transthoracic and, if findings were negative, transesophageal echocardiography.

RESULTS

Thirty-three patients were found to have endocarditis on the basis of clinical criteria (surgical confirmation in 17 patients), and the remaining 39 served as control subjects. Initial scintigraphy was true positive in 26 patients (sensitivity 79%) and false positive in 7 (specificity 82%). Echocardiography was true positive in 29 patients (sensitivity 88%) and false positive in 1 (specificity 97%). Scintigraphy was positive in the four patients with false negative echocardiography, and echocardiography was positive in the seven patients with false negative scintigraphy. Thus, the combination of scintigraphy and echocardiography yielded a sensitivity of 100% and a specificity of 82%. In 10 of the 11 patients with two to three follow-up studies, scintigraphy became negative parallel to clinical improvement, indicating decreasing floridity of the inflammatory process.

CONCLUSIONS

Immunoscintigraphy in patients with subacute infective endocarditis provides valuable diagnostic information in equivocal echocardiographic findings and may be used to monitor antibiotic therapy.

Echocardiographic assessment of patients with infectious endocarditis: prediction of risk for complications

To enhance the echocardiographic identification of high risk lesions in patients with infectious endocarditis, the medical records and two-dimensional echocardiograms of 204 patients with this condition were analyzed. The occurrence of specific clinical complications was recorded and vegetations were assessed with respect to predetermined morphologic characteristics. The overall complication rates were roughly equivalent for patients with mitral (53%), aortic (62%), tricuspid (77%) and prosthetic valve (61%) vegetations, as well as for those with nonspecific valvular changes but no discrete vegetations (57%), although the distribution of specific complications varied considerably among these groups. There were significantly fewer complications in patients without discernible valvular abnormalities (27%). In native left-sided valve endocarditis, vegetation size, extent, mobility and consistency were all found to be significant univariate predictors of complications. In multivariate analysis, vegetation size, extent and mobility emerged as optimal predictors and an echocardiographic score based on these factors predicted the occurrence of complications with 70% sensitivity and 92% specificity in mitral valve endocarditis and with 76% sensitivity and 62% specificity in aortic valve endocarditis.

Effect of electrical stimulus parameters on the development and propagation of action potentials in short excitable fibres

Intracellular action potentials (IAPs) produced by short fibres in response to their electrical stimulation were analysed. IAPs were calculated on the basis of the Hodgkin-Huxley (1952) model by the method described by Joyner et al. (1978). Principal differences were found in processes of activation of short (semilength L less than 5 lambda) and long fibres under near-threshold stimulation. The shorter the fibre, the lower was the threshold value (Ithr). Dependence of the latency on the stimulus strength (Ist) was substantially non-linear and was affected by the fibre length. Both fibre length and stimulus strength influenced the IAP amplitude, the instantaneous propagation velocity (IPV) and the site of the first origin of the IAP (and, consequently, excitability of the short fibre membrane). With L less than or equal to 2 lambda and Ithr less than or equal to Ist less than or equal to 1.1Ithr, IPV could reach either very high values (so that all the fibre membrane fired practically simultaneously) or even negative values. The latter corresponded to the first origin of the propagated IAP, not at the site of stimulation but at the fibre termination or at a midpoint. The characters of all the above dependencies were unchanged irrespective of the manner of approaching threshold (variation of stimulus duration or its strength). Reasons for differences in processes of activation of short and long fibres are discussed in terms of electrical load and latency. Applications of the results to explain an increased jitter, velocity recovery function and velocity-diameter relationship are also discussed.

Infective endocarditis in children with congenital heart disease: comparison of selected features in patients with surgical correction or palliation and those without

The diagnostic and prognostic features of 44 episodes of infective endocarditis in 42 children with congenital heart disease were reviewed. Endocarditis occurred in 18 patients who had not had surgical correction or palliation of the defect (non-operated group). There were 26 episodes in 24 patients who had been treated surgically (operated group) (16 open and eight closed cardiac operations). Endocarditis occurred soon after open heart surgery in eight patients and as a late complication in the other 16. It recurred in two patients (operated group). Invasive monitoring and low cardiac output were consistent features in those patients who had endocarditis soon after open heart surgery whereas dental treatment was a common feature in non-operated cases and after closed cardiac operations. Late cases of endocarditis after open heart surgery had various microbiological features that were not typical of infection after dental problems. Gram positive infections occurred in non-operated patients and in those who had had closed cardiac operations. The group that had open heart surgery had infections caused by Gram positive, Gram negative, and anaerobic bacteria and fungi. Fever, anaemia, leucocytosis, and positive blood cultures were the only consistent findings. Vegetations were seen in nine of 12 patients at cross sectional echocardiography. All 12 (four non-operated, one closed, and seven open cases) needed acute surgical treatment. The mortality from infective endocarditis was 17% for non-operated cases, 0% for those who had had closed heart surgery, and 50% for those who had had open heart surgery. Infective endocarditis after open heart surgery differs from that in the other subgroups in terms of microbiology, source of infection, and outcome and its early diagnosis depends on a thorough investigation of minimal symptoms and signs.

Infective endocarditis: a challenging disease

Enhanced clinical awareness of infective endocarditis, along with improved microbiologic methodology and more aggressive surgical intervention, has favorably influenced the outcome of the disease. The evolving nature of infective endocarditis over the past decade is described, as are the changing epidemiologic factors, microbiologic techniques, and echocardiographic contributions in the clinical management of patients with infective endocarditis.

Contribution of echocardiography and immediate surgery to the management of severe aortic regurgitation from active infective endocarditis

The timing of surgery in patients with severe aortic regurgitation and left ventricular (LV) failure, particularly when associated with active infective endocarditis (IE), is of the utmost importance. From July 1982 to May 1984, 34 patients, aged 15 to 60 years, with severe aortic regurgitation underwent immediate (within 24 hours of diagnosis) aortic valve surgery. All patients were in New York Heart Association class IV for LV failure. Eighteen patients had right-sided heart failure. Decision for immediate surgery was based on the echocardiographic demonstration of diastolic closure of the mitral valve or of vegetations on the aortic valve. Premature closure of the mitral valve was demonstrated echocardiographically in 17 patients, 13 of whom had diastolic crossover of LV and left atrial pressure tracings recorded at surgery. IE of the aortic valve was confirmed at surgery in 29 patients, 27 of whom had vegetations on echocardiography. Seven patients required replacement of both aortic and mitral valves. Antibiotic therapy for IE was started immediately after blood cultures were taken and continued for 4 to 6 weeks postoperatively. The mortality rate within 30 days of surgery was 6% for the group as a whole and 7% for those with IE. Mean follow-up period for the 32 survivors was 10.6 months. There were 2 late deaths. No patient had periprosthetic regurgitation or persistence of endocarditis. Procrastination in referral for surgery of these extremely ill patients is not justified and is likely to be associated with higher risks of morbidity and mortality.

Culture negative infective endocarditis

Twenty cases of culture negative infective endocarditis admitted to the Cardiology Department of Green Lane Hospital from 1959 to 1980 out of a total of 265 cases (7.5%), were analysed retrospectively. Cases were included only when adequate proof of endocarditis was available at surgery or postmortem. Indiscriminate use of antibiotics before taking blood cultures was the most common association with failure to obtain positive cultures, seen in 16 of the 20 patients described. Failure to obtain positive cultures in four cases was attributed to inadequate bacteriologic techniques before 1967. Where no antibiotics were given prior to collecting blood cultures and bacteriologic techniques were adequate, proven culture negative endocarditis was virtually unknown. When antibiotics have been given, repeated blood cultures are recommended following withdrawal of antibiotic for at least four days.

Two-dimensional echocardiographic assessment of bioprosthetic valve dysfunction and infective endocarditis

Two-dimensional echocardiography of Hancock porcine heterograft valves was evaluated by correlation with clinical, hemodynamic, angiographic and pathologic findings in 80 patients. Ninety-five aortic and mitral bioprostheses were categorized by the type of valvular abnormality: group I, dysfunction due to primary tissue failure (41 valves); group II, dysfunction due to paravalvular leakage without infection (5 valves); group III, infective endocarditis with or without hemodynamic dysfunction (28 valves); and group IV, control cases without dysfunction or infection (21 valves). Increased size of a bioprosthetic leaflet image (minimal dimensions 3 x 5 mm) was observed in 46% (19 of 41) of cases with primary tissue failure and in 62% (10 of 16) of cases with leaflet vegetations due to endocarditis. Prolapse of leaflet echoes to below the level of the bioprosthetic sewing ring occurred in 76% (28 of 37) of cases with torn leaflets and also in 46% (6 of 13) of valves with vegetations on intact leaflets. Antegrade extension of leaflet echoes to beyond the level of the stents, observed in 4 of 16 cases with leaflet vegetations, was the only echocardiographic sign distinguishing leaflet infection from leaflet degeneration. Aortic bioprostheses with ring dehiscence affecting 40 to 90% of the anular circumference showed motion discordant with the motion of the adjacent aortic root and native anulus. Although echocardiographic abnormalities are frequently observed with bioprosthetic leaflet degeneration or infection, the echocardiographic appearance often does not distinguish between these two major complications and is best interpreted concurrently with other clinical and laboratory assessment.

Clinical utility and management impact of M-mode echocardiography

To determine the clinical utility and management impact of M-mode echocardiography, 182 echocardiograms were analyzed at a university teaching hospital. The physicians who ordered the echocardiograms said that 12 percent provided crucial information that was not available from other tests and that 26 percent resulted in a change in patient management. According to two independent board-certified cardiologist-reviewers, 86 percent of echocardiograms were appropriately ordered, but only 15 echocardiograms (8 percent) were actually needed for a change to a new and appropriate management. According to the reviewers, the 77 Group I M-mode echocardiograms (those ordered to evaluate left ventricular function, left atrial size, potential cardiac sources of emboli, or the possibility of bacterial endocarditis, or those ordered in patients who, according to the ordering physician, had undergone or would undergo catheterization regardless of the results of echocardiography) were less likely than the 105 Group II M-mode echocardiograms (those ordered to evaluate possible mitral valve prolapse, hypertrophic cardiomyopathy, valvular function, or the pericardium) to be ordered appropriately, to provide helpful information, or to provide crucial results. Group I echocardiograms had reviewer-assessed appropriate management impact in only one case (1 percent) compared with a 13 percent rate of management impact for Group II M-mode echocardiograms (p less than 0.01). Although echocardiography can be accurate and valuable with yields similar to those of other noninvasive procedures, 77 (42 percent) of 182 M-mode echocardiograms in this hospital could be predicted at the time of ordering to be in a low-yield group.

Culture-negative infective endocarditis

Culture-negative endocarditis is not uncommon; the most frequent causes of the culture negative state are prior antibiotic therapy and problems with or inadequacies in bacteriologic technique. In addition to blood culture, studies that can aid in substantiating a presumptive diagnosis of infective endocarditis include echocardiography. Immunologic tests, and cardiac catheterization. Empiric antibiotic therapy often is necessary and should not be delayed to await positive blood cultures and results of antimicrobial sensitivity studies.