Transesophageal echocardiographic recognition of subaortic complications in aortic valve endocarditis. Clinical and surgical implications

Evaluation of prosthetic valve function and associated complications

Significant advances in imaging modalities have occurred to evaluate prosthetic valve function and associated complications. These developments involve predominantly the introduction of Doppler technology for the non-invasive determination of gradients and valve areas and TEE for an improved assessment of valve structure, function, and associated complications. The current role of cinefluoroscopy is mostly to complement TEE in the evaluation of motion of mechanical prosthetic valves in the aortic position. Cardiac catheterization is now rarely needed to assess valve function. Diagnosis of prosthetic valve obstruction can be performed in the majority of cases with transthoracic Doppler echocardiography. Differentiation of valve obstruction from normal valve function in small valves with high flow conditions, however, may be difficult. Because of this and the variability in normal valves among different prostheses, knowledge of the type and size of the implanted valve is essential. Patients and ultrasound laboratories are encouraged to seek and provide this information on a routine basis. Although transthoracic echocardiography is the main diagnostic modality for the serial evaluation of prosthetic valve function, it is important to recognize its limitations in assessing prosthetic mitral regurgitation and evaluating structural abnormalities of prosthetic valves. These are the situations in which TEE has the most impact. A summary of general indications of TEE in prosthetic valves is provided in Table 6. Finally, a baseline transthoracic Doppler study is essential in the overall follow-up and serial evaluation of valve function. For future comparisons, the best indices of valve functions are those obtained for patients as their own control, from a baseline Doppler echocardiographic study performed early after the operation.

Aneurysms in the left ventricular outflow tract: clinical presentation, causes, and echocardiographic features

We present a descriptive compendium of anatomically interrelated aneurysms and aneurysmal-like structures arising in and around the left ventricular outflow tract. Images selected from the Mayo Clinic echocardiography database illustrate classic or typical examples of each entity. Essential morphologic features of each lesion are described. Clinical presentation, causes, and diagnostic echocardiographic features taken together can improve recognition and clinical management of this diverse group of anomalies.

Aneurysm of the mitral-aortic intervalvular fibrosa as a rare cause of angina pectoris: angiographic demonstration

Aneurysms of the mitral-aortic interventricular fibrosa (MAIF) are exceptionally rare complications, commonly following aortic valve endocarditis. This report describes the angiographic findings of such an aneurysm, in a patient who developed an uncommon symptomatology of unstable angina pectoris, caused by the aneurysm's expansion against the coronary arteries. Surgical treatment is also discussed.

Valvular perforation in left-sided infective endocarditis: a prospective echocardiographic evaluation and clinical outcome

We undertook this study to determine the use of transthoracic and transesophageal echocardiography in detecting valvular perforation and the clinical impact of the latter on the outcome of left-sided infective endocarditis. Transthoracic echocardiography was performed in 58 consecutive patients with infective endocarditis. According to the study protocol, a subgroup of 42 patients also underwent transesophageal echocardiogrophy. At referral, 20 (34%) of 58 patients had echocardiographic evidence of valvular perforation (group A). No valvular perforations were found in the remaining 38 patients (group B). During a follow-up period of 27 +/- 16 months, a major complication occurred in 18 of 20 patients in group A and in 11 of 38 patients in group B (p < 0.0001). Univariate analysis indicated previous infective endocarditis, aortic involvement, and New York Heart Association functional class had a predictive value for valvular perforation (p < 0.001). Stepwise regression analysis confirmed aortic valve perforation as the only independent predictive variable for surgery and death. Valvular perforation is a common complication of infective endocarditis and is associated with an adverse outcome. Transthoracic echocardiography can detect or suggest valvular perforation in infective endocarditis, but transesophageal echocardiography better defines this complication and predicts severe heart failure or the need for early surgical management.

Aortic root abscess with fistula formation

Aortic root abscess is a common complication of aortic valve endocarditis. However, aortic root abscess and formation of a fistula from the aortic root to the right ventricular outflow tract in the setting of a native aortic valve and previous repair of an aortic dissection with a Dacron graft is an uncommon event. Transesophageal echocardiography is superior to transthoracic echocardiography for the diagnosis of aortic root abscess. To our knowledge, no studies have compared the diagnostic value of cardiac MRI with transesophageal echocardiography for this condition.

Mitral and tricuspid valve aneurysms evaluated by transesophageal echocardiography

This report describes the clinical and transesophageal echocardiographic findings in 2 patients with mitral and 2 with tricuspid valve aneurysms and reviews the 19 published echo-diagnosed cases. One of our patients with a mitral valve aneurysm and 12 of those in the published reports had associated aortic valve endocarditis.

Gonococcal endocarditis: assessment by transesophageal echocardiography

Gonococcal endocarditis is a rare but aggressive infection that has an alarming rate of perivalvular abscess and mortality. We present a case of gonococcal endocarditis with intracardiac abscess and fistula diagnosed by transesophageal echocardiography. Given the often acute nature of gonococcal endocarditis and its propensity toward abscess formation, transesophageal echocardiography should be considered early in the course of this infection.

Aorto-left atrial fistula. A reversible cause of acute refractory heart failure

Fistulas between the aorta and left atrium, invariably a complication of aortic valvular endocarditis, are rare and infrequently diagnosed premortem. We describe a patient who presented with this entity and review the reports of five other patients for whom a diagnosis was made premortem. A number of causative organisms have been identified. The clinical course is characteristically one of rapidly progressive heart failure. Notably, only half of these fistulas were detected by transthoracic echocardiography, whereas all were identified by transesophageal echocardiography when utilized. Once the diagnosis is made, prompt surgical repair is required to avert the high mortality from rapidly developing refractory congestive heart failure.

Ruptured aortic cusp aneurysm in infective endocarditis

We describe a patient affected by infective endocarditis with aortic aneurysm, waiting for valve replacement, in which aortic cusp rupture determined sudden heart failure. Diagnosis was performed by serial transthoracic echocardiograms and successful surgical valve replacement was performed in emergency.

Cardiac, cerebral, and vascular complications of infective endocarditis

The complications of IE may involve any organ system. Cardiac complications are frequently present, and heart failure remains a leading cause of death. Abscess formation in the surrounding cardiac tissues may result in myocardial or pericardial disease, and cardiac conduction abnormalities may develop. Extracardiac complications, including neurologic, vascular, and renal diseases, are also common and are usually caused by either embolization of vegetations or deposition of immune complexes. Despite many advancements in the detection and treatment of the complications of IE, management of these problems remains a challenging endeavor.

Indications for and timing of surgical intervention in infective endocarditis

Infective endocarditis, especially when it involves prosthetic valves, is a serious, often fatal illness. Although antibiotics are essential in management, surgery is required in many patients who develop even incipient heart failure and structural complications. Early identification and referral results in improved mortality and morbidity rates, and there is evidence that surgery should play a larger role in managing infective endocarditis. Patients with intracardiac pacemakers and cardioverting devices represent a growing reservoir of patients with the potential to develop endocarditis.

Role of transthoracic and transesophageal echocardiography in diagnosis and management of infective endocarditis

Echocardiography has become a mainstay in the diagnosis of endocarditis. Vegetations were first visualized noninvasively beginning with M-mode echocardiography in the mid-1970s. The evolution of echocardiography, to include first two-dimensional imaging and then Doppler imaging in the 1980s, established echocardiography as the noninvasive test of choice to evaluate for the presence of vegetations as well as for their sequelae. Most recently, the addition of transesophageal echocardiography has expanded the role and yield of echocardiography in diagnosing endocarditis as well as in guiding management.

Echocardiography and Doppler assessment of prosthetic heart valves with transesophageal echocardiography

This article examines the use of transesophageal echocardiography (TEE) in the assessment of prosthetic heart valves. A summary of the commonly used artificial valves and their physiologic regurgitant flow patterns, as identified by color Doppler imaging, is presented. The hemodynamic evaluation of prosthetic valve stenosis using Doppler techniques is reviewed, and the diagnostic utility of TEE in identifying the complications of cardiac prostheses is discussed.

Assessment of endocarditis and associated complications with transesophageal echocardiography

TEE offers many benefits in the evaluation of patients with IE. It provides increased sensitivity as compared to TTE in the detection of this disease, and is better able to identify and delineate many of the associated complications and hemodynamic aberrancies. TEE also has helped expand our knowledge of the pathophysiology and natural history of IE. Continued advances in the technology of TEE instrumentation undoubtedly will lead to further improvements in our ability to assess and to treat patients stricken with this serious infection. Nevertheless, IE continues to exact a significant toll on its victims, and our efforts to diagnose, to treat, and to prevent it must not weaken.

Transesophageal echocardiographic diagnosis of eustachian valve endocarditis

A 33-year-old man with a history of intravenous drug abuse was seen with fever, septic pulmonary embolization, and Staphylococcus aureus bacteremia. Transthoracic echocardiography was nondiagnostic. Transesophageal echocardiography showed a large, pedunculated, and highly mobile vegetation attached to the eustachian valve.

Role of echocardiography in perioperative management of patients undergoing open heart surgery

TEE has assumed a pivotal role in the perioperative management of patients undergoing open-heart surgery. The information obtained influences important therapeutic decisions in thoracic aortic surgery, valvular surgery, and coronary artery bypass surgery. TEE also assists in determining the reason for failure to wean from cardiopulmonary bypass and allows rapid detection of the etiology of hypotension in the patient after surgery. Advances in technology have resulted in three-dimensional images of cardiac structures, and this will further enhance the usefulness of echocardiography for the surgeon. TEE should no longer be regarded as an imaging tool available only in academic centers, but should be routinely used by qualified operators in centers performing open-heart surgery.

Transesophageal echocardiography in critical care units: Henry Ford Hospital experience and review of the literature

Transthoracic echocardiography is of limited value in intensive care units primarily because of mechanical ventilators, surgical wounds, and the inability to position the patient to his left side. Imaging from the transesophageal window overcomes these problems, resulting in good-quality study in these patients subsets. We performed both transthoracic and transesophageal echocardiography with color-flow Doppler tests in 121 patients in various critical care units. The transesophageal ultrasound test was valuable in identifying patients with suspected left-sided native and prosthetic valve vegetations, prosthetic mitral but not aortic valve regurgitation, native mitral and aortic valve pathoogy, and aortic dissection and in determining cardiac etiology of systemic emboli, hypotension, hypoxia, and heart failure. Based on transesophageal echocardiographic findings, additional information was provided in 38 (32%) patients, resulting in appropriate surgery in 22 instances. In conclusion, transesophageal echocardiography is a useful tool in evaluating critically ill patients.

Echocardiographic assessment of vegetations in patients with infective endocarditis: prognostic implications

Today, echocardiography is the most important technique next to clinical findings and blood cultures in the diagnosis of infective endocarditis. The sensitivity of echocardiography, particularly the transesophageal approach, for detection of vegetations and endocarditis related valvular destructions is high. In addition, echocardiographic findings may have some prognostic implications. The size and mobility of vegetations stratifies endocarditis patients into a high risk group for arterial embolism. In particular, mobile vegetations attached to the mitral valve with a maximal diameter > 10 mm may be prone to embolic events. Furthermore, increase in size of vegetations during antimicrobial treatment may identify patients with no, or at least a prolonged, healing process. Also, a lack of increase in the echo density of vegetations under adequate antibiotic treatment may indicate a poor healing process and may necessitate more aggressive management. The demonstration of paravalvular abscesses by echocardiography, particularly by transesophageal echocardiography, identifies a subgroup of patients who will need urgent cardiac surgery before widespread tissue destruction has occurred.

Has transesophageal echocardiography changed the approach to patients with suspected or known infective endocarditis?

Infective endocarditis is still a great clinical challenge. Its diagnosis is difficult to establish, and mortality has remained around 30%. Early diagnosis and optimal treatment are crucial fo prognosis improvement. Echocardiography plays an indispensable role in the management of this disease, especially with the recently introduced approach, transesophageal echocardiography (TEE). TEE can overcome the limitations of transthoracic echocardiography (TTE) and is superior to TTE in almost every way in providing earlier and more information for the diagnosis and treatment of infective endocarditis. TEE detects valve vegetations with much higher sensitivity and specificity than TTE. It can demonstrate smaller vegetations in the early stage of the disease and vegetations on atypical locations (e.g., mitral valve annulus), and provides detailed characterization of vegetations (e.g., location, size, mobility, and changes during treatment). Such information is of great prognostic value and may help in selecting proper treatment. TEE is more sensitive for detecting complications, such as mitral valve perforation, abscess, and subaortic complications, which respond poorly to medicine and for which timely surgery may be the best treatment. For those with prosthetic valve endocarditis, TEE is especially useful because TTE is greatly limited by the acoustic shadow of prostheses. Both positive and negative results of TEE examination are valuable for confirming or excluding infective endocarditis. TEE also plays a unique role in intraoperative monitoring and can assess surgical results before the chest is closed. TEE has become an invaluable tool for the diagnosis and management of patients with suspected or known infective endocarditis.

Criteria for the diagnosis of endocarditis and the role of echocardiography

When infective endocarditis is a diagnostic possibility, echocardiography permits noninvasive imaging of cardiac structures. As involvement of the endocardium is a sine qua non of endocarditis, echocardiography may assist in its diagnosis by demonstrating such involvement. The ability of echocardiography to detect the intracardiac manifestations of infective endocarditis has continued to improve, especially with the introduction of transesophageal imaging. This article will discuss some of the echocardiographic findings in endocarditis and elucidate the incorporation of these findings in the new Duke criteria for the diagnosis of endocarditis.

Coronary artery compression caused by a large pseudoaneurysm of the mitral-aortic intervalvular fibrosa

An unusual late complication of bacterial endocarditis is described. Four years after diagnosis and treatment, a patient is seen with coronary artery compression caused by a large pseudoaneurysm of the mitral-aortic intervalvular fibrosa. The utility of transesophageal echocardiography in diagnosis and surgical management is emphasized.

Infective endocarditis

IE is a fascinating disease that continues to challenge the clinicians. Over the last several decades, there have been marked changes in its presentation. The morbidity and mortality have markedly improved by early diagnosis and prompt treatment using highly effective antibiotic regimens and early valve replacement surgery whenever necessary. Early diagnosis is possible by improvement in blood culture techniques and advances in transthoracic and transesophageal echocardiographic approaches. This article has reviewed the pathogenesis, microbiology, clinical presentation, diagnostic methodology, treatment, and prevention of IE.

A rare complication of aortic valve endocarditis: diagnosis with transesophageal echocardiography

Rupture of the membranous interventricular septum resulting in a left ventricular to right atrial shunt is a rare complication of endocarditis. Early recognition of this complication is essential because these patients require early surgical intervention. We report a case of a left ventricular-right atrial shunt complicating aortic valve endocarditis in which transesophageal echocardiography was used to accurately diagnose the lesion before surgery. We will discuss the role of transesophageal echocardiography in the diagnosis of this lesion and will review the existing literature pertaining to this rare complication.

Anatomical definition of aortic root abscesses by transesophageal echocardiography: planning a surgical strategy using homograft valves

Infective endocarditis of the native or a prosthetic aortic valve may be complicated by abscess cavity development in the aortic root, and successful treatment depends upon early diagnosis, clear anatomical definition preoperatively, and maintaining sterility of the second implant. Homograft valves offer many advantages in this setting. Timing of surgery and the choice of the particular technique depends on accurate characterization of the anatomical details of the abscess. Five cases of paravalvular aortic root abscess in the setting of prosthetic valve endocarditis are described. In each case the diagnosis was made with transesophageal echocardiography, and the information was used in planning the operative procedure of homograft valve replacement. This strategy is proposed as optimal management of this potentially lethal condition.

Endocarditis-associated paravalvular abscesses. Do clinical parameters predict the presence of abscess?

STUDY OBJECTIVE

To determine whether standard clinical and transthoracic echocardiographic criteria considered to be suggestive of the presence of endocarditis-associated paravalvular abscess are predictive of which patients would benefit from reliable but invasive transesophageal echocardiographic investigations for abscess.

DESIGN

Retrospective chart review.

SETTING

A 630-bed university hospital.

PATIENTS

Forty-eight patients with 51 episodes of definite endocarditis and 24 paravalvular abscesses.

MEASUREMENTS AND RESULTS

A comparison of abscess and nonabscess populations revealed that clinical parameters (patient demographics, valvular involvement, presence of a prosthesis, infection with a virulent organism, pericarditis, persistent fever, persistent bacteremia, congestive heart failure, history of intravenous drug use, embolization) and transthoracic echocardiographic parameters were insensitive predictors of the presence of abscess. The only statistically significant correlate was the presence of previously undetected atrioventricular or bundle branch block. Paravalvular abscesses were common in our population and were associated with increased mortality. Improved survival correlated with the absence of mitral valve involvement and the absence of moderate-to-severe congestive heart failure.

CONCLUSIONS

Given the accuracy and safety of transesophageal echocardiography and the unreliability of clinical and transthoracic echocardiographic criteria, we recommend that transesophageal echocardiography be considered in all endocarditis patients with previously unrecognized conduction disturbances, aortic or prosthetic valve involvement, or both, or indications for valve replacement, or all of the foregoing.

A case of mitral-aortic intervalvular fibrosa aneurysm with unique flow patterns and long-term natural survival

We report a patient with a large aneurysm of mitral-aortic intervalvular fibrosa as a complication of prosthetic aortic valve endocarditis diagnosed on transthoracic echocardiography. This aneurysm began to expand with atrial systole, filled fully during ventricular systole, and collapsed in diastole on transesophageal examination. The patient refused corrective surgery and has survived on medical treatment for close to 2 years.

Transesophageal echocardiography and adult cardiac operations

Transesophageal echocardiography (TEE) now is used widely as a monitoring technique during and after cardiac operations. Widespread adoption of the technique has provided a wealth of new information. This review analyzes the influence of TEE on the routine conduct of cardiac operations and on surgical decision making in specific areas. Its use in routine hemodynamic monitoring and problem solving, both intraoperatively and postoperatively, is discussed. Transesophageal echocardiography has a particular role in valve operations, in guiding and assessing the immediate results of mitral valve repair. It also has found application in the grading and operative management of the severely atheromatous aorta, the diagnosis and management of aortic dissection, and other aspects of surgery of the thoracic aorta. In addition, management in specialized areas, such as cardiopulmonary transplantation and the insertion and monitoring of ventricular assist devices, have also been helped by the information provided by TEE.

Pseudoaneurysms of the mitral-aortic intervalvular fibrosa: dynamic characterization using transesophageal echocardiographic and Doppler techniques

OBJECTIVES

The aim of this study was to provide a detailed description of echocardiographic and Doppler features of pseudoaneurysms involving the mitral-aortic intervalvular fibrosa and to compare echocardiographic and aortographic findings.

BACKGROUND

Infection of the aortic valve may spread to the aortic annulus, resulting in ring abscesses or pseudoaneurysms, or both, of the intervalvular fibrosa, which can alter patient management and prognosis.

METHODS

The echocardiographic and Doppler findings of 20 patients with pseudoaneurysms or ring abscesses, or both, were reviewed and compared with surgical and aortographic results.

RESULTS

A total of 23 lesions were identified, of which 16 were intervalvular pseudoaneurysms, and 7 were ring abscesses. Transthoracic echocardiography detected 43% of the lesions, whereas transesophageal echocardiography identified 90% (p < 0.01). The most distinct feature of the pseudoaneurysms was marked pulsatility, with systolic expansion and diastolic collapse (mean systolic area [+/- SD] 4.1 +/- 3.4 cm2 vs. diastolic mean area 1.8 +/- 2.2 cm2, p < 0.05). Using color Doppler, two types were identified: unruptured pseudoaneurysms (n = 9), which communicated only with the left ventricular outflow tract and had a distinct flow pattern, and ruptured pseudoaneurysms (n = 7), which, in addition, communicated with the left atrium or aorta. Compared with pseudoaneurysms, ring abscesses were smaller and nonpulsatile and showed either no flow or continuous systolic and diastolic flow, the site of paravalvular aortic insufficiency. In 10 patients who underwent aortography, three lesions were identified, and findings were concordant with echocardiography. However, in seven patients aortographic findings were normal, whereas echocardiography identified intervalvular pseudoaneurysms, all of which were documented at operation.

CONCLUSIONS

Intervalvular pseudoaneurysms are more frequently detected by transesophageal echocardiography than by aortography or transthoracic examination and exhibit distinct dynamic features and Doppler patterns that can further help characterize cavitary lesions in the aortic root and guide appropriate surgical intervention.

Role of transoesophageal echocardiography in the diagnosis and management of aortic root abscess

OBJECTIVE

To assess and compare the roles of transthoracic and transoesophageal echocardiography in the diagnosis and management of an aortic root abscess.

DESIGN

To select patients with echocardiographic diagnosis of aortic valve endocarditis with and without an aortic root abscess and correlate this with a retrospective review of surgical and necropsy data.

SETTING

Tertiary referral centre at a university teaching hospital.

PATIENTS AND METHODS

34 patients with confirmed aortic valve endocarditis were treated over a four and a half year period. All patients underwent both transthoracic and transoesophageal echocardiography with 17 patients having biplane or multiplane imaging.

RESULT

11 patients (32%) had an aortic root abscess. Transthoracic echocardiography identified four cases of aortic root abscess whereas transoesophageal echocardiography correctly detected all 11 cases and also detected complications including mitral aortic intervalvar fibrosa fistula in two patients and right atrial involvement in another two patients. Only biplane imaging was able to show an anterior aortic root abscess in one patient and the circumferential involvement of the aortic annulus in another two patients. All patients with an aortic root abscess were treated surgically after transoesophageal echocardiographic diagnosis. After operation, prosthetic aortic regurgitation was present in seven patients and a repeat operation was performed in three patients. Only transoesophageal echocardiography detected a postoperative aorto-right atrial fistula in two patients and recurrence of the root abscess in another. There were five deaths in hospital (45%).

CONCLUSIONS

Compared with transthoracic echocardiography, transoesophageal echocardiography was more sensitive and more specific for the early diagnosis of aortic root abscess and its complications and facilitated both the preoperative and postoperative management of these patients. Biplane and multiplane imaging provide additional diagnostic information. All patients with suspected aortic valve endocarditis should have an early transoesophageal echocardiographic study.

Echocardiographic identification of infective endocarditis within a congenital left sinus of Valsalva-right atrial communication

A rare case is described of infective endocarditis within a congenital left sinus of Valsalva aneurysm to right atrial communication diagnosed by a combination of precordial and transesophageal echocardiography. The respective roles of precordial and transesophageal echocardiography in this case are discussed with regard to both diagnosis and surgical decision making.

Application of transthoracic and transesophageal echocardiography in the diagnosis and management of infective endocarditis

Infective endocarditis continues to be a cause of significant cardiac morbidity and mortality. To improve the prognosis of patients with this disorder, early diagnosis is crucial but difficult to establish on the basis of clinical parameters alone. Echocardiography, both transthoracic and transesophageal techniques, has a major role in the detection of vegetations that are the hallmark of endocarditis. Valvular and perivalvular complications can also be well assessed by echocardiography. With the improved resolution provided by recent technologic advances in echocardiography, vegetations can be reliably detected in most patients with endocarditis. We propose that present diagnostic criteria for endocarditis be revised to include echocardiographic findings as a major parameter in the diagnosis. Finally, a diagnostic approach incorporating transthoracic and transesophageal echocardiography in these patients will be discussed taking into consideration the different degrees of clinical suspicion for the existence of the disease.

New criteria for diagnosis of infective endocarditis: utilization of specific echocardiographic findings. Duke Endocarditis Service

PURPOSE

This study was designed to develop improved criteria for the diagnosis of infective endocarditis and to compare these criteria with currently accepted criteria in a large series of cases.

PATIENTS AND METHODS

A total of 405 consecutive cases of suspected infective endocarditis in 353 patients evaluated in a tertiary care hospital from 1985 to 1992 were analyzed using new diagnostic criteria for endocarditis. We defined two "major criteria" (typical blood culture and positive echocardiogram) and six "minor criteria" (predisposition, fever, vascular phenomena, immunologic phenomena, suggestive echocardiogram, and suggestive microbiologic findings). We also defined three diagnostic categories: (1) "definite" by pathologic or clinical criteria, (2) "possible," and (3) "rejected." Each suspected case of endocarditis was classified using both old and new criteria. Sixty-nine pathologically proven cases were reclassified after exclusion of the surgical or autopsy findings, enabling comparison of clinical diagnostic criteria in proven cases.

RESULTS

Fifty-five (80%) of the 69 pathologically confirmed cases were classified as clinically definite endocarditis. The older criteria classified only 35 (51%) of the 69 pathologically confirmed cases into the analogous probable category (p < 0.0001). Twelve (17%) pathologically confirmed cases were rejected by older clinical criteria, but none were rejected by the new criteria. Seventy-one (21%) of the remaining 336 cases that were not proven pathologically were probable by older criteria, whereas the new criteria almost doubled the number of definite cases, to 135 (40%, p < 0.01). Of the 150 cases rejected by older criteria, 11 were definite, 87 were possible, and 52 were rejected by the new criteria.

CONCLUSION

Application of the proposed new criteria increases the number of definite diagnoses. This should be useful for more accurate diagnosis and classification of patients with suspected endocarditis and provide better entry criteria for epidemiologic studies and clinical trials.

Southwestern Internal Medicine Conference: clinical applications of transesophageal echocardiography

Transesophageal echocardiography has emerged recently as a powerful cardiac imaging tool. The strengths and limitations of transesophageal echocardiography are reviewed. The clinical use of transesophageal echocardiography in aortic dissection, endocarditis, mitral valve disease, prosthetic heart valves, stroke, and miscellaneous other conditions is discussed.

Transesophageal echocardiographic recognition of an unusual complication of aortic valve endocarditis

Aortic valve endocarditis can cause complications due to involvement of the subaortic structures. These complications include satellite vegetations on the aortic regurgitant jet lesion sites, involvement of the anterior or posterior mitral valve leaflets in the form of aneurysms, perforation, and involvement of the mitral-aortic intervalvular fibrosa, namely abscess, aneurysm, and perforation into the left atrium or the pericardial sac. These complications can be identified accurately by echocardiography. We report an unusual case which demonstrates (1) coexistence of both mitral-aortic intervalvular fibrosa and mitral valve aneurysms, and (2) echocardiographic follow-up of a mitral valve aneurysm to perforation. These complications were recognized by transesophageal echocardiography and verified at surgery.

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.