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J Am Coll Cardiol, 2000; 35:1638-1646 © 2000 by the American College of Cardiology Foundation |
a Division of Internal Medicine, Nishida Hospital, Oita, Japan
Manuscript received August 13, 1999; revised manuscript received November 11, 1999, accepted January 21, 2000.
Reprint requests and correspondence: Dr. Hajime Kataoka, Division of Internal Medicine, Nishida Hospital, 3-3-24 Ohte-machi, Saiki-city, Oita 876-0831, Japan
| Abstract |
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This study examined the usefulness of thoracic ultrasonography for evaluation of fluid accumulation in patients with decompensated chronic heart failure (CHF) in comparison with physical signs, upright posteroanterior chest X-ray and echocardiography.
BACKGROUND
Decompensated CHF is frequently accompanied by pleural effusion, suggesting that pleural effusion is a useful marker for confirming the diagnosis of the uncontrolled stage of CHF. Thoracic ultrasonography seems to be adequate for this purpose.
METHODS
Patients with uncontrolled CHF and an interpretable physical examination, chest X-ray, ultrasonogram for the heart and thorax and thoracic X-ray computed tomographic (CT) scan were enrolled in the study (n = 60). Patients free from thoracic and cardiovascular diseases served as a control (n = 22). Thoracic CT scan was used as the gold standard for the presence or absence of pleural effusion. Variables used to predict body fluid accumulation included the following: pulmonary rales, jugular venous distension or peripheral edema, roentgenographic evidence of pulmonary edema or pleural fluid, pericardial or pleural effusion on ultrasonographic study.
RESULTS
The reported incidence of pleural effusion detected by thoracic ultrasonography was high (91%). The incidence of physical signs and roentgenographic signs of body fluid accumulation, however, was modest (56%) to low (33%). The best clinical variable for identifying patients with decompensated CHF was the detection of pleural fluid by thoracic ultrasonography (91% predictive accuracy). This variable also had high interobserver agreement (95% overall agreement, kappa = 0.70). There was only 41% to 65% predictive accuracy of other clinical variables, with 72% to 95% agreement (kappa = 0.4000.848).
CONCLUSIONS
Thoracic ultrasonography is a simple, sensitive and accurate method for the evaluation of body fluid accumulation in patients with decompensated CHF. This technique can be used to assist in making the diagnosis of decompensated CHF if other causes of pleural effusion have been clinically ruled out.
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Thoracic CT in the supine position is the method of choice for accurate diagnosis of the presence or absence of pleural effusion. As a rule, however, CT study cannot be emergently performed in orthopneic patients with uncontrolled CHF. In emergency situations in which CT study is not available or is not available quickly enough, ultrasonography might make a crucial contribution to the diagnosis of pleural effusion. Some previous studies (6,7) used thoracic ultrasonography for detection of pleural effusion in heart failure patients, but these reports did not define the accuracy of thoracic ultrasonography for evaluation of such patients. Furthermore, there is no comparative study on the evaluation of body fluid accumulation in uncontrolled CHF patients among thoracic ultrasonography and traditional clinical tests. Thus, this study was performed to ascertain the accuracy and usefulness of thoracic ultrasonography for evaluation of fluid accumulation in patients with decompensated CHF in comparison with physical signs, upright posteroanterior chest X-ray and echocardiography.
| Methods |
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Methodology.
Detailed data were collected prospectively at the time of the diagnosis in study patients meeting criteria for heart failure. Each patient provided written informed consent before participating in the study. Data obtained immediately after admission included a thorough cardiovascular history and physical findings, blood chemistry, electrocardiogram (ECG), upright posteroanterior chest X-ray and ultrasonographic examination for the heart and thorax. To confirm myocardial failure, a serum assay for atrial (normal range:
43 pg/ml) and brain natriuretic peptide (
18.4 pg/ml) was performed (9,10). After completion of admission data collection, all subjects underwent chest X-ray CT study as early as possible (41 [68%] within 2 h, 12 [20%] within 12 h and 7 [12%] within 24 h after admission). Diagnostic thoracentesis and pericardiocentesis were performed appropriately to confirm the cause of effusion (11). Patients were initially treated with some combination of oxygen, digoxin, nitrate, diuretics, sympathomimetic agents and synthetic human alpha atrial natriuretic peptide. Clinical, serum natriuretic peptides, ECG, plain chest X-ray and ultrasonographic examinations were repeated during a follow-up period.
Bedside physical examinations. Pulmonary crackles or rales were recorded as present or absent. Jugular venous distension was deemed present if venous pulsations were visible at 45° from the horizontal plane (12). The presence or absence of peripheral edema and of a third heart sound was also noted.
Chest radiography. All radiographs were evaluated for the presence or absence of cardiomegaly (cardiothoracic ratio more than 0.5), venous redistribution (upper lobe vessels more prominent than lower), interstitial edema (hilar haziness, peribronchial cuffing, Kerley B lines) or alveolar pulmonary edema and pleural effusion (1315).
Cardiac ultrasonography. Echocardiography was performed using a commercially available real-time wide-angle phased-array system incorporated with a color-Doppler system (Aloka SSD-2000, Aloka Co. Ltd., Tokyo, Japan). Standard imaging views were obtained with the patient lying in the left lateral decubitus position. Full two-dimensional, M mode, color flow and Doppler studies were performed on each patient. Pericardial effusion was defined to be present when an echo-free space was clearly visualized between the epicardium and pericardium and was associated with flattening of the pericardial echo relative to the epicardial echo (16). An anterior echo-free space in the absence of a significant posterior echo-free space was not considered indicative of pericardial effusion (16).
Thoracic ultrasonography. After completion of the echocardiography, the patient was asked to assume a sitting position. The thoracic ultrasonographic study (6,7,1721) consisted of echographic investigation of each hemithorax using a 3.5 MHz sector transducer through the intercostal space avoiding the ribs. The liver and spleen, and occasionally the kidney, were used as guides to thoracic ultrasonography for the detection of pleural fluid. The ribs and the interface of lung and pleura are readily identified, with the latter reflecting most of the acoustic energy and appearing as a bright white line often associated with distal reverberation echoes. Identification of a smaller amount of the pleural fluid in heart failure patients is ordinarily accomplished by applying the transducer on the posterolateral thoracic wall where the most dependent portion of the costophrenic sulcus in the pleural space can be detected in the upright position. As the pleural effusion accumulates, it gradually extends from this portion to the lateral and eventually reaches the anterior costophrenic sulcus. Shallow respiration enhances the ability of ultrasonography to detect fluid collection, which appears as an echo free space between the lung and the adjacent abdominal organ (i.e., the liver in the right hemithorax and the spleen in the left hemithorax). Figure 1 shows a representative example of thoracic ultrasonographic findings in a CHF patient with bilateral pleural effusion.
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Study variables. Variables used to predict body fluid accumulation included the following: presence of pulmonary crackles, rales or wheezing, jugular venous distension or peripheral edema on bedside physical examination, roentgenographic evidence of pulmonary interstitial and alveolar edema or pleural fluid and presence of pericardial effusion or pleural effusion on ultrasonographic study for the heart and thorax. Two observers independently evaluated each patient for the presence or absence of these study variables. Consensus agreements were reached when there was disagreement between two observers.
Statistical analysis. Continuous variables were reported as mean ± SD and compared using Student t test. Categorical variables were expressed as the percentage and compared using the chi-square test or McNemars test, appropriately. The agreement between two clinicians was assessed by calculating the Kappa value; the strength of agreement is "poor" when the value of kappa is less than zero, "slight" from 0 to 0.20, "fair" from 0.21 to 0.40, "moderate" from 0.41 to 0.60, "substantial" from 0.61 to 0.80 and "almost perfect" from 0.81 to 1.00 (23). Sensitivity was defined as 1 number of false negatives/number of true negatives; specificity was defined as 1 number of false positives/number of true negatives; and predictive accuracy was defined as number of correct tests/number of patients tested (24). A p value of less than 0.05 was considered to be statistically significant.
| Results |
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100 ml) of pleural effusion, it was detected by thoracic ultrasonography in as many as 80% (left hemithorax) to 87% (right hemithorax) of the patients. In contrast, plain chest X-ray examination detected only 13% of the cases in which there was a very small amount of pleural effusion in the right hemithorax. In total, thoracic ultrasonography identified significantly more pleural effusion in each hemithorax than did plain chest radiograph: 92% in the right hemithorax and 93% in the left hemithorax and only 48% (p < 0.001) and 26% (p < 0.001) in the plain chest radiograph, respectively. Incidence of clinical signs of body fluid accumulation. Table 4 shows the frequency of clinical signs of body fluid accumulation in 60 patients with decompensated CHF by two clinicians. Reported incidence was excellently high in the variable of the pleural effusion detected by thoracic ultrasonography (90% to 92%). The incidence of rales or wheezing was modest (53% to 58%) but that of other physical signs of jugular venous distension (33% to 42%) and peripheral edema (33%) was low. On chest radiograph, the frequency of the presence of pulmonary edema (43% to 47%) or pleural effusion (38% to 43%) was low, but the presence of two or more variables moderately predicted body fluid accumulation (57% to 65%).
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| Discussion |
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With regard to assessment of the presence and severity of fluid retention, results of this study indicate that thoracic ultrasonography is a simple, sensitive and accurate method for evaluation of patients with decompensated CHF. When compared with traditional physical and chest radiographic examinations, this method proves to be very useful for identifying the signs of body fluid accumulation.
Body fluid retention in CHF. Chronic heart failure resulting from diminished cardiac function is invariably caused by an abnormality of the muscle, rhythm, valves or pericardium. The syndrome of CHF is the response of the body to the hearts inability to maintain an adequate blood supply at a rate commensurate with the requirements of the metabolizing tissues. The primary problem in CHF is cardiac, but the clinical syndrome is characterized by secondary multisystem dysfunction, which ultimately leads to a terminal state of multiorgan failure (25). The reduction in cardiac output that occurs in the failing heart activates the sympathetic nervous system (26,27), resulting in an increased heart rate and vasoconstriction. A decrease in renal perfusion results in activation of the renin-angiotensin-aldosterone system, leading to production of the powerful vasoconstrictor angiotensin II and, ultimately, sodium retention through the actions of aldosterone (28,29). Water retention is also augmented by vasopressin production from the posterior pituitary (30). Other potent vasoconstrictors, such as endothelin, contribute to an increase in peripheral vascular resistance (31,32). These changes might not be sufficiently counteracted by the cardiac endocrine system, which produces natriuretic and vasodilating atrial and brain natriuretic peptides (9,10,33,34). As a result, this sequence of the spiraling course of heart failure induces more and more retention of sodium and water and is ultimately punctuated by acute exacerbations (so-called decompensated CHF) that require hospital admission.
Symptoms of heart failure.
The classical symptoms of heart failure are dyspnea, ankle edema and fatigue. Dyspnea on exertion is common in the general population, particularly in patients with respiratory disease or in the obese, and, therefore, it cannot be used as the selection criterion for the diagnosis of heart failure (25). Orthopnea and paroxysmal nocturnal dyspnea are less common in the general population than dyspnea alone, but less sensitive, for the diagnosis of heart failure (2,25,3538). Additionally, there are many asymptomatic or minimally symptomatic patients who are existing even in the uncontrolled stage of CHF, particularly among aged patients in whom the prevalence increases sharply, affecting perhaps as many as 5% to 10% of individuals over the age of 65 (39,40). In this study, the incidence of mild subjective symptoms of heart failure (NYHA class II) tended to be higher in patients
75 years (15 of 40 patients, 38%) than in younger patients (3 of 20, 15%; p < 0.1). The most probable reasons for the lack of subjective heart failure symptoms in the aged are their low level of daily activity or high rate of complicating cerebrovascular disease, which should obscure complaint of the dyspneic sensation.
Classical clinical signs of body fluid accumulation in CHF. An accurate objective measurement of the presence of body fluid retention is necessary in order to evaluate patients with decompensated CHF. The difficulty in clinically defining such patients, however, stems from the fact that no simpler or more objective sign of body fluid accumulation is currently available because there is no clear cut-off sign of fluid accumulation that can be used reliably to identify subjects with decompensated CHF. Previous experiences indicate that some patients with decompensated CHF have no classical clinical or radiographic signs of congestion, despite markedly elevated pulmonary filling pressures and decreased cardiac output (12,41).
Body fluid retention in decompensated CHF is reflected in physical signs of congestion, such as ankle edema, jugular venous distension and pulmonary crackles. Plain chest radiograph is also a traditional standard method of choice to obtain objective evidence of body fluid accumulation. At least seven studies (2,12,3537,42,43) have examined the sensitivity, specificity and predictive value of physical signs for diagnosis of heart failure (25). These studies suggest that none of the signs of fluid retention (i.e., peripheral edema, jugular venous distension and pulmonary rales) is particularly sensitive, though specificity varied among studies (25). Additionally, some studies have shown that there is disagreement among several clinicians regarding recognition of classical physical signs of heart failure (44,45). The results of this study are consistent with these previous observations; the incidence of classical physical signs for identifying body fluid accumulation and the agreement between two observers on these signs, except for pulmonary rales, were only modest.
Radiography is still a standard method for evaluating heart failure patients. Two important specific markers for fluid accumulation on plain chest radiograph are pleural effusion and interstitial edema (hilar haziness, peribronchial cuffing, Kerley B lines) or alveolar pulmonary edema. Radiographic identification of pleural effusion (15,17), however, is reported to be insensitive and detects only moderate to large accumulation of pleural fluid. Indeed, this study demonstrated that detection of the fluid in either hemithorax using plain X-ray occurred in only 38% to 43% of patients and was confirmed by using X-ray thoracic CT, though concordance by two observers in identifying this sign was substantial. The incidence of roentgenographic signs of pulmonary congestion was also not high, and the interobserver agreement of this sign was only modest, which is consistent with previous observations (12,46). Previous reports suggested that chronically high left-sided heart pressures permit compensatory mechanisms to correct the fluid shift that has occurred, which can mask clinical and radiographic evidence of the underlying hemodynamic derangements. Increased lymphatic drainage will clear flooded alveoli, and radiographic evidence of edema might be absent (12,47,48).
Role of ultrasonography for detection of body fluid accumulation. The findings of the X-ray thoracic CT in this study indicated that as many as 90% of decompensated CHF patients have pleural effusion, suggesting that CT scan might be very useful for confirming pleural effusion in the uncontrolled stage of CHF. The most frequently encountered problems with CT scans are, however, difficulty in transporting critically ill patients and compelling the orthopneic patient to assume a supine position during the examination, which makes X-ray thoracic CT scans inconvenient or impractical (19). This study clearly demonstrated that thoracic ultrasonography efficiently supplemented the role of CT scan for the diagnosis of pleural effusion in decompensated CHF. Most importantly, the best clinical sign for identifying patients with decompensated CHF among the study variables was the detection of pleural fluid by thoracic ultrasonography. In our experience, evaluation of CHF patients using this method often revealed unexpected body fluid accumulation and changed patient management. The use of ultrasonography to detect decreased pleural effusion could become one of the most useful markers for confirming the therapeutic effectiveness of decompensated CHF. Of course, it should be kept in mind that the signs of body fluid accumulation, including thoracic ultrasonography, have a limited value for revealing latent myocardial failure or predicting the prognosis of CHF patients, because these markers are evident only with acute exacerbation of CHF. The measurement of one or more natriuretic peptides (9,10,33,34) will be more useful for this purpose.
Echocardiography combined with Doppler study is rapidly establishing itself as the primary investigation in patients with suspected heart failure (4952). Thoracic ultrasonography, however, is not currently used in the routine assessment of heart failure patients. This technique has several advantages: 1) high predictive accuracy in detecting body fluid accumulation, 2) ease of performance at bedside, 3) flexibility and short examination time compared with X-ray thoracic CT scan, and 4) lower cost. These advantages make thoracic ultrasonography a useful diagnostic tool with great potential for assisting decision making and management of patients with decompensated CHF.
Several disadvantages should also be pointed out:
Though recent guidelines for the evaluation and management of heart failure reported from the European Society of Cardiology (51) or from the American College of Cardiology/American Heart Association (52) do not include thoracic ultrasonography as a diagnostic tool for the evaluation of heart failure patients, this technique should be performed at an early stage in the management of any patient with a suspected diagnosis of CHF in order to obtain objective evidence of fluid accumulation in the pleural cavity.
Study limitations. There are important limitations to this study:
Conclusions. Diagnosis of decompensated CHF in general practice is likely to remain haphazard and will continue to require objective substantiation. Results of this study indicated that thoracic ultrasonography is a simple, sensitive and accurate method for evaluation of the body fluid accumulation in patients with decompensated CHF. This technique can be used to assist in making the diagnosis of decompensated CHF and in the investigation of CHF patients during the follow-up period, if other causes of pleural effusion have been clinically ruled out.
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