Identification of multivessel coronary artery disease by exercise echocardiography

OBJECTIVES

This study examined the ability of exercise echocardiography to identify multivessel coronary artery disease and ascertain its incremental value when combined with clinical and exercise test variables.

BACKGROUND

Although exercise echocardiography has been shown to be accurate for the detection of coronary artery disease, little is known about its utility for identifying multivessel involvement, and its incremental value when combined with clinical and exercise test variables has not been studied.

METHODS

One hundred fifty consecutive patients were selected on the basis of having had an exercise echocardiographic and a coronary angiographic study within 6 months without any revascularization procedure. Significant coronary artery disease (> or = 50% diameter stenosis in any major coronary artery) was present in 117 patients, and multivessel (two- or three-vessel) disease was present in 90 patients. The exercise echocardiographic studies were reviewed by an experienced observer unaware of the results of the coronary angiogram.

RESULTS

The overall sensitivity and specificity of exercise echocardiography for the identification of multivessel disease were 73% and 70%, respectively. A stepwise logistic regression analysis identified the number of abnormal regions on the postexercise images as the strongest independent predictor of multivessel disease; also significant were a history of myocardial infarction and ST segment depression of at least 2 mm on the peak exercise electrocardiogram.

CONCLUSIONS

Exercise echocardiography adds independent and incremental information to clinical and exercise test variables for identifying multivessel coronary artery disease.

Diagnostic role of Doppler echocardiography in constrictive pericarditis

OBJECTIVES

This study was conducted to assess the diagnostic role of Doppler echocardiography in constrictive pericarditis.

BACKGROUND

It has been observed that patients with constrictive pericarditis have a characteristic Doppler pattern of respiratory variation in ventricular filling and central venous flow velocities. However, the observation was based on a small number of patients with known diagnosis.

METHODS

We reviewed the echocardiographic features of 28 patients (21 men and 7 women; mean age +/- SD 55 +/- 15 years) with suspected constrictive pericarditis who underwent exploratory thoracotomy or pericardiectomy.

RESULTS

At operation, constrictive pericarditis was diagnosed in 25 patients, restriction in 1 and normal pericardium in 2. Of the 25 patients with constriction, correct preoperative Doppler diagnosis was made in 22 (88%) and Doppler echocardiography showed restriction in 3. In two patients with a normal pericardium, Doppler features were consistent with constriction in one patient and were normal in the other. In the one patient with restriction, Doppler echocardiography showed restriction. In 19 patients with surgically proved constriction, repeat Doppler study after pericardiectomy showed normal findings in 14 and restriction in 5. Twelve of the 14 patients with normalized Doppler findings became asymptomatic, whereas all 5 with restrictive Doppler features remained symptomatic.

CONCLUSIONS

Doppler echocardiography performed simultaneously with respiratory recording is highly sensitive for diagnosing constrictive pericarditis, and it appears to predict functional response to pericardiectomy.

Transient constrictive pericarditis: diagnosis by two-dimensional Doppler echocardiography

Patients with constrictive pericarditis usually require pericardiectomy to relieve their symptoms. In some patients, however, constrictive pericarditis may resolve spontaneously or with medical treatment. Four patients with transient constrictive pericarditis are described in this report. Although the cause of pericarditis differed, all patients had a small to large amount of pericardial effusion, followed by symptoms, signs, and Doppler features typical of constrictive pericarditis. Symptomatic improvement occurred after treatment with some combination of nonsteroidal anti-inflammatory agents, corticosteroids, and antibiotics. The resolution of the symptoms paralleled the normalization of characteristic respiratory changes in Doppler flow velocities. The condition of our patients most likely was related to a transient inflammation (or thickening) of the pericardium due to viral, bacterial, or immunologically mediated pericarditis. Resolution of the thickened pericardium was documented by magnetic resonance imaging in one patient. Awareness of the possible transient nature of constrictive pericarditis in a subgroup of patients with constriction has important clinical implications when pericardiectomy is considered. The resolution of constrictive pericarditis can be documented by serial Doppler echocardiographic examination.

Evolution of echocardiographic modalities in detection of postmyocardial infarction ventricular septal defect and papillary muscle rupture: study of 62 patients

Diagnostic sensitivity of various echocardiographic modalities was assessed for postinfarct ventricular septal defect (40 patients) and papillary muscle rupture (22 patients). Two-dimensional transthoracic echocardiography enabled direct visualization of ventricular septal defect in 68% and combined two-dimensional Doppler echocardiography was diagnostic in 95%. Papillary muscle rupture was directly visualized in 45%, and severe mitral regurgitation was present on Doppler color flow images in 100%. Transesophageal echocardiography was diagnostic in all nine patients (five with ventricular septal defect and four with papillary muscle rupture) in whom this modality was applied. Thus two-dimensional Doppler echocardiography (transthoracic and transesophageal if necessary) is highly sensitive in detecting postinfarct ventricular septal defect and papillary muscle rupture.

Effect of ambient illumination on the spatial properties of the center and surround of Y-cell receptive fields

The primary goal of this study was to expand the description of the filtering properties of the Y-cell receptive field, by quantitatively characterizing the spatial filtering properties of the receptive field's center-and-surround components as a function of adapting light level. A range of more than five orders of magnitude in retinal illuminance were covered, including the vast majority of the cat's functional range of vision. Recordings were taken from optic tract fibers of Y cells in cats under general anesthesia. Sinusoidal gratings and a stimulus designed to selectively probe the properties of the surround mechanism were used. The cells' responses to these stimuli were fit to a Gaussian center-surround receptive-field model, in which six parameters define the properties of the center and surround. Fits were made independently to data collected at each light level and changes in the values of the model's parameters with illuminance are reported. A set of equations that summarize the changes in parameter values is given. From these summary equations, reasonable estimates of the parameters' values can be determined across a wide range of illuminances. Hence, a quantitative model of the spatial properties of the center and surround of the Y-cell receptive field can now be derived from these equations for most of the levels of retinal illuminance experienced by a Y cell. The consistency between the description provided by our equations and results from earlier work is considered.

Multiplane transesophageal echocardiography: image orientation, examination technique, anatomic correlations, and clinical applications

Multiplane transesophageal echocardiography (TEE) consists of a single ultrasound array or imaging sector that can be rotated around the long axis of the ultrasound beam typically in a 180 degrees arc. This capability produces a circular (conical) continuum of tomographic two-dimensional images. The principal advantage of multiple TEE is that the transducer can be rotated to an image-specific orientation and critically optimized. Thus, manipulation of the transducer is less complex than with the biplane technique, and user adaptation is considerably enhanced. The logical image notation (that is, degrees of rotation) and orientation are described in this report. A step-by-step approach to the multiplane TEE examination, which evolved from our initial experience with 400 consecutive patients, is correlated with accompanying tomographic anatomic corroboration. The unique clinical applications are discussed and related to the amplification of diagnostic information. Although the multiplanar TEE transducer is relatively large, all adult patients who weigh 40 kg or more can be examined. No major complications occurred in our initial experience with this promising new technology.

Echocardiography in valvular heart disease

Clinical applications of echocardiography continue to grow and be refined with the development of newer technology and the resultant increase in clinical studies. The reliability of echocardiography applied to patients with valvular heart disease has been very well established in determining pressure gradient, stenotic valve area, right-sided cardiac pressure, and ventricular responses (dimension and global systolic function) to pressure and volume overload. Less well established are the determination of regurgitation severity, the role of echocardiography in endocarditis, and the use of the echocardiographic information in clinical decision-making. These issues have been dealt with extensively in the most recent literature. Through superb visualization of the native and prosthetic valvular apparatus by transesophageal echocardiography, new morphologic and functional observations continue to be made.

Mitral valve operation in postinfarction rupture of a papillary muscle: immediate results and long-term follow-up of 22 patients

The long-term clinical outcome was assessed in 22 patients (15 men and 7 women; mean age, 68 years) who underwent mitral valve replacement or repair for acute mitral regurgitation due to postinfarction rupture of a papillary muscle during the period 1981 through 1990 at the Mayo Clinic. All but three patients underwent operation within the first 3 weeks after acute myocardial infarction. The perioperative mortality was 27%, and the estimated actuarial survival rate at 7 years postoperatively was 47% and 64% for the entire group and for the patients who survived the operation, respectively. The concomitant performance of a coronary artery bypass grafting procedure was the only factor identified that improved both immediate and long-term survival. Patients with a decreased preoperative left ventricular ejection fraction (less than 45%) had somewhat greater short-term and long-term mortality than did those with a left ventricular ejection fraction of 45% or more, but the difference was only of borderline statistical significance. Other factors such as age, sex, severity of coronary artery disease, preoperative existence of congestive heart failure, and timing of the operation in relationship to occurrence of the infarction had no effect on survival. Of the 13 long-term survivors, 10 had significant clinical improvement in comparison with their preoperative state.

Dynamic intraventricular obstruction during dobutamine stress echocardiography. A new observation

BACKGROUND

The implications of hypotension occurring during dobutamine stress echocardiography have not been elucidated. We observed in some patients that hyperdynamic left ventricular function developed during dobutamine stress echocardiography and hypothesized that intracavitary obstruction was occurring and might account for hypotension in some patients.

METHODS AND RESULTS

Fifty-seven consecutive patients undergoing dobutamine stress echocardiography underwent pulsed-wave and continuous-wave Doppler examination of the left ventricular cavity at rest and at peak dobutamine infusion. The development of an intraventricular gradient with dobutamine stress was defined as a late-peaking left ventricular Doppler velocity profile that exceeded basal velocity by at least 1 m/sec. During dobutamine stress testing, left ventricular outflow velocity or intracavitary velocity increased in all patients. Obstruction occurred in 12 patients (21%, group 1). Group 2 was the remaining 45 patients. Peak velocities in group 1 ranged from 2.0 to 5.0 m/sec (mean, 3.5 m/sec), and the mean increase from velocity at rest was 2.3 m/sec. The mean change in systolic blood pressure was significantly lower in patients in group 1 (-15 versus 4 mm Hg, p = 0.02). When the 18 patients with an ischemic response to stress testing (evidenced by new or worsening wall motion abnormalities) were excluded from analysis, systolic blood pressure response was still significantly different for the two groups (-19 versus 2 mm Hg, p = 0.03).

CONCLUSIONS

Dynamic left ventricular obstruction is a new observation; it may develop frequently in patients undergoing dobutamine stress echocardiography. Obstruction rather than ischemia may explain a decrease in blood pressure during dobutamine stress echocardiography.

Intraoperative evaluation of mitral valve regurgitation and repair by transesophageal echocardiography: incidence and significance of systolic anterior motion

OBJECTIVE

This study was designed to delineate the utility and results of intraoperative transesophageal echocardiography in the evaluation of patients undergoing mitral valve repair for mitral regurgitation.

BACKGROUND

Mitral valve reconstruction offers many advantages over prosthetic valve replacement. Intraoperative assessment of valve competence after repair is vital to the effectiveness of this procedure.

METHODS

Intraoperative transesophageal echocardiography was performed in 143 patients undergoing mitral valve repair over a period of 23 months. Before and after repair, the functional morphology of the mitral apparatus was defined by two-dimensional echocardiography; Doppler color flow imaging was used to clarify the mechanism of mitral regurgitation and to semiquantitate its severity.

RESULTS

There was significant improvement in the mean mitral regurgitation grade by composite intraoperative transesophageal echocardiography after valve repair (3.6 +/- 0.8 to 0.7 +/- 0.7; p less than 0.00001). Excellent results from initial repair with grade less than or equal to 1 residual mitral regurgitation were observed in 88.1% of patients. Significant residual mitral regurgitation (grade greater than or equal to 3) was identified in 11 patients (7.7%); 5 underwent prosthetic valve replacement, 5 had revision of the initial repair and 1 patient had observation only. Of the 100 patients with a myxomatous mitral valve, the risk of grade greater than or equal to 3 mitral regurgitation after initial repair was 1.7% in patients with isolated posterior leaflet disease compared with 22.5% in patients with anterior or bileaflet disease. Severe systolic anterior motion of the mitral apparatus causing grade 2 to 4 mitral regurgitation was present in 13 patients (9.1%) after cardiopulmonary bypass. In 8 patients (5.6%), systolic anterior motion resolved immediately with correction of hyperdynamic hemodynamic status, resulting in grade less than or equal to 1 residual mitral regurgitation without further operative intervention. Transthoracic echocardiography before hospital discharge demonstrated grade less than or equal to 1 residual mitral regurgitation in 86.4% of 132 patients studied. A significant discrepancy (greater than 1 grade) in residual mitral regurgitation by predischarge transthoracic versus intraoperative transesophageal echocardiography was noted in 17 patients (12.9%).

CONCLUSIONS

Transesophageal echocardiography is a valuable adjunct in the intraoperative assessment of mitral valve repair.

Restrictive left ventricular diastolic filling identifies patients with heart failure after acute myocardial infarction

Left ventricular diastolic filling was characterized by transmitral pulsed-wave Doppler velocities in 62 patients with acute myocardial infarction, and diastolic filling variables were correlated with the presence of clinical heart failure. At the time of admission, 47 patients were free of heart failure and 15 patients were in Killip class II to IV. In the latter group of patients with heart failure, peak velocity of late filling wave caused by atrial contraction (A) was lower (0.48 versus 0.59 m/sec, p < 0.05), ratio of peak velocity of early rapid filling wave to peak velocity of late filling wave caused by atrial contraction (E/A) was higher (1.5 versus 1.1, p < 0.01), and deceleration time (136 versus 196 msec, p = 0.0001) was shorter when compared with the patients not in heart failure after acute myocardial infarction. Multivariate analysis showed that the deceleration time was a powerful independent predictor of presence of heart failure after controlling for systolic functional variables. Therefore, diastolic filling variables can complement systolic functional variables in the identification of the patients with postinfarction left ventricular failure.

Mitral regurgitation due to ruptured chordae tendineae in patients with hypertrophic obstructive cardiomyopathy

Mitral valve regurgitation in association with hypertrophic obstructive cardiomyopathy is usually caused by the systolic anterior motion of the anterior mitral leaflet. Recently, five patients were encountered with hypertrophic obstructive cardiomyopathy who had mitral regurgitation due to ruptured chordae tendineae. The diagnosis was confirmed in all patients during operation for left ventricular septal myectomy-myotomy (Morrow procedure). Preoperative identification of ruptured chordae tendineae as the cause of mitral regurgitation was established by transesophageal echocardiography in the three most recent cases. All patients had successful septal myectomy-myotomy for relief of left ventricular outflow obstruction, and mitral valve competence was restored by valve repair rather than by prosthetic valve replacement. The clinical course of these patients illustrates important management considerations as well as the utility of transesophageal echocardiography for diagnosis. Chordal rupture should be considered in the differential diagnosis of mitral regurgitation in patients with hypertrophic obstructive cardiomyopathy, especially in those with acute hemodynamic deterioration.

Critical appraisal of transesophageal echocardiography: limitations, pitfalls, and complications

Because transesophageal echocardiography is invasive, it has the potential for serious complications. Limitations occur because of the restricted transducer mobility within transducers for special situations. Pitfalls (potential erroneous diagnoses resulting from misinterpretation of normal and abnormal anatomy) are prevalent with this new technology. This report critically reviews transesophageal echocardiography and discusses and illustrates commonly encountered limitations, pitfalls, and complications.

Value and limitations of two-dimensional echocardiography in predicting myocardial infarct size

To investigate the quantitative relations between the severity of regional wall motion abnormalities and segmental infarct size and between the severity of overall left ventricular dysfunction and global infarct size, a clinicopathologic study was undertaken of 30 patients who had a 2-dimensional (2-D) echocardiogram within 7 days before death. The severity of regional wall motion abnormalities was graded for each segment with a 2-D echocardiographic 14-segment model. The severity of global left ventricular dysfunction was calculated as the mean of the visualized regional wall motion scores. On pathologic examination of autopsy specimens, segmental infarct size was estimated as a percentage of the segmental cross-sectional area. The global infarct size was expressed as a percentage of the total left ventricular mass. At the segmental level, regional wall motion score was positively correlated (r = 0.53) with the segmental infarct size. The sensitivity and specificity of detecting infarcted segments by abnormal wall motion scores were 81 and 71%, respectively. All dyskinetic segments revealed infarct size of greater than or equal to 10%. The wall motion score index was positively correlated (r = 0.52) with the global infarct size. The mean global infarct size was 7% for the 8 patients with a wall motion score index of less than 2, which was significantly lower than the mean of 27% for the 22 patients with a wall motion score index of greater than or equal to 2 (p less than 0.001). A 2-D echocardiogram is sensitive and specific in detecting infarcted segments and can be useful in quantitating myocardial damage after myocardial infarction.

Effect of sample volume location on Doppler-derived transmitral inflow velocity values

In 25 patients with acute myocardial infarction and in 25 normal subjects, pulsed-wave Doppler echocardiography was performed in the apical four-chamber view with the sample volume first between the mitral leaflet tips and then at the mitral anulus. The early filing wave (E) and late filling wave (A) peak velocities measured from Doppler strip charts were significantly (p less than 0.001) higher at the tips in both groups. E velocity increase was greater than A velocity increase, producing a significantly (p less than 0.001) higher E/A velocity ratio at the tips than at the anulus. The deceleration time was longer at the tips than at the anulus (p less than 0.001) in both groups. Therefore it is important to know sample volume location in the interpretation of mitral inflow velocity. It is critical to maintain the same sample volume location in serial assessments of left ventricular diastolic filling characteristics.

Value and limitations of transesophageal echocardiography in assessment of mitral valve prostheses

BACKGROUND

Transthoracic Doppler echocardiography examination has become an integral part of the investigations performed in patients with mitral valve prostheses. The limitations of the transthoracic approach are well documented. Transesophageal echocardiography provides a unique window for achieving a clear view of the mitral prosthesis.

METHODS AND RESULTS

This study shows the usefulness of transesophageal echocardiography in clinical practice for assessment of patients with a mitral valve prosthesis. This technique demonstrated an abnormality in 48% of patients who had normal results on transthoracic examination. The overall sensitivity of transesophageal echocardiography was 96%.

CONCLUSIONS

Transesophageal echocardiography constitutes an essential part of a comprehensive two-dimensional/Doppler echocardiographic examination in patients with suspected malfunction of mitral prostheses.

Lipomatous hamartoma of the tricuspid valve: echocardiographic-pathologic correlations

We report the eighth example of a cardiac valvular hamartoma (five mitral, three tricuspid). An intracavitary right atrial mass was present in a 76-year-old man and was characterized echocardiographically by a mobile cystic structure involving the septal tricuspid leaflet. Microscopically, the affected leaflet was comprised predominantly of mature adipose tissue. Formation of a valvular windsock in this case was attributed to the chronic effect of right ventricular pressure on tissue that was weaker than a normal leaflet. Valvular hamartomas should be included in the differential diagnosis of lesions that produce prolapsing, cystic, or windsock malformations of atrioventricular valves.

Prognostic significance of Doppler measures of diastolic function in cardiac amyloidosis. A Doppler echocardiography study

BACKGROUND

We have previously characterized the left ventricular diastolic filling abnormalities in cardiac amyloidosis by Doppler methods. The various filling patterns were shown to be related to the degree of cardiac amyloid infiltration. The purpose of this study was to determine the value of Doppler diastolic filling variables for assessing prognosis in cardiac amyloidosis.

METHODS AND RESULTS

We performed pulsed-wave Doppler studies of the left ventricular inflow and obtained clinical follow-up data in 63 consecutive patients with biopsy-proven systemic amyloidosis. All patients had typical echocardiographic features of cardiac involvement. The patients were subdivided into two groups according to deceleration time: Group 1 (33 patients) had a deceleration time of 150 msec or less, indicative of restrictive physiology, and group 2 (30 patients) had a deceleration time of more than 150 msec. Of the 63 patients, 32 (51%) died during a mean follow-up period of 18 +/- 12 months. Of these deaths, 25 (78%) were cardiac deaths, and 19 of the 25 patients (76%) were from group 1. The 1-year probability of survival in group 1 was significantly less than that in group 2 (49% versus 92%, p less than 0.001). Bivariate analysis revealed that the combination of the Doppler variables of shortened deceleration time and increased early diastolic filling velocity to atrial filling velocity ratio were stronger predictors of cardiac death than were the two-dimensional echocardiographic variables of mean left ventricular wall thickness and fractional shortening.

CONCLUSIONS

Doppler-derived left ventricular diastolic filling variables are important predictors of survival in cardiac amyloidosis.

Coronary artery bypass operation in dialysis patients

To analyze the short- and long-term morbidity and mortality among maintenance dialysis patients who have undergone coronary artery bypass operations, we identified 25 such patients at the Mayo Clinic and three recently published large single-center studies that provided sufficient detail for meaningful comparison. Two independent observers reviewed the new information with regard to pertinent historical, clinical, and laboratory data. The perioperative mortality was 20%. Among the perioperative survivors, 1- and 2-year survival rates were 95% and 77%, respectively. The 3-year actuarial survival was 70%. Uniformly, the symptoms diminished, and the need for antianginal medication was decreased. In the three other large published series, the perioperative mortality ranged from 3 to 20%, and coronary artery bypass performed earlier after the onset of the symptoms seemed to result in a lower perioperative mortality. We conclude that elective coronary artery bypass in dialysis patients is associated with acceptable short-term morbidity and mortality and effective relief of symptoms. Surgically treated patients may have a survival advantage. Thus, we advocate aggressive early investigation and surgical treatment of these patients.

Transesophageal echocardiography in critically ill patients

The feasibility, safety and clinical impact of transesophageal echocardiography were evaluated in 51 critically ill intensive care unit patients (28 men and 23 women; mean age 63 years) in whom transthoracic echocardiography was inadequate. At the time of transesophageal echocardiography, 30 patients (59%) were being mechanically ventilated. Transesophageal echocardiography was performed without significant complications in 49 patients (96%), and 2 patients with heart failure had worsening of hemodynamic and respiratory difficulties after insertion of the transesophageal probe. The most frequent indication, in 25 patients (49%), was unexplained hemodynamic instability. Other indications included evaluation of mitral regurgitation severity, prosthetic valvular dysfunction, endocarditis, aortic dissection and potential donor heart. In 30 patients (59%), transesophageal echocardiography identified cardiovascular problems that could not be clearly diagnosed by transthoracic echocardiography. In the remaining patients, transesophageal echocardiography permitted confident exclusion of suspected abnormalities because of its superior imaging qualities. Cardiac surgery was prompted by transesophageal echocardiographic findings in 12 patients (24%) and these findings were confirmed at operation in all. Therefore, transesophageal echocardiography can be safely performed and has a definite role in the diagnosis and expeditious management of critically ill cardiovascular patients.

The mechanism of blood flow during closed chest cardiac massage in humans: transesophageal echocardiographic observations

Despite years of research, the mechanism of forward blood flow during closed chest cardiac massage remains controversial. Two theories have been suggested: the cardiac pump theory and the thoracic pump theory. Transesophageal echocardiography offers a new approach for study of the flows and cardiac morphologic features during chest compressions in humans. Case reports are presented to illustrate the use of transesophageal echocardiography during cardiopulmonary resuscitation. The findings included right and left ventricular compression, closure of the mitral valve during compression, opening of the mitral valve during the release phase, and atrioventricular valvular regurgitation during compression, indicating a positive ventricular-to-atrial pressure gradient. These findings suggest that direct cardiac compression was the predominant mechanism of forward blood flow during cardiopulmonary resuscitation in these patients. An understanding of the actual mechanisms involved is necessary if improved cardiopulmonary resuscitative techniques or adjuncts are to be rationally developed for enhancing the outcome of resuscitation.

Biplanar transesophageal echocardiography: anatomic correlations, image orientation, and clinical applications

Clinical transesophageal echocardiography is a rapidly expanding diagnostic procedure. Conventional transesophageal endoscopes allow imaging from a single array mounted in the horizontal plane. This article introduces the clinical application of biplanar imaging, which incorporates a second orthogonal longitudinal plane. Our clinical experience with 291 patients who underwent biplanar transesophageal echocardiography is presented. The examination, technique, and resultant anatomic correlations unique to this new examination are discussed and illustrated. The anatomy is displayed in a familiar format comparable to the precordial examination. Biplanar imaging adds substantially to the comprehensive anatomic delineation of certain cardiac structures.

Unstable angina

Unstable angina can manifest as an array of symptom complexes. In some patients, medical therapy will stabilize the episodes of angina, and only predismissal exercise testing or angiography (or both) will be necessary. At the other end of the spectrum are patients with rest angina or multiple episodes of silent ischemia who are refractory to medical therapy and experience undetected microinfarction. Most of these patients require immediate catheterization and subsequent intervention with intra-aortic balloon pulsation, percutaneous transluminal coronary angioplasty, or coronary artery bypass grafting. An entire spectrum of manifestations exists between these two extremes. One challenge during the 1990s will be better stratification of patients with unstable angina so that safe, efficient, cost-effective treatment strategies can be appropriately applied to all patients.