Diagnostic Accuracy of Clinical Assessment of the Heart Murmur of Pulmonary Stenosis

Abstract & Commentary

Synopsis: Although expert clinical examination is highly accurate for distinguishing pulmonary stenosis from non-pulmonary stenosis cardiac murmurs in pediatric patients, it is imperfect in assessing severity of stenosis.

Source: Danford DA, et al. Pulmonary stenosis: Defect-specific diagnostic accuracy of heart murmurs in children. J Pediatr 1999;134:76-81.

In order to determine whether echocardiographic studies are necessary to confirm a diagnosis of pulmonary valve stenosis (PVS) made on the basis of physical examination by an expert pediatric cardiologist, Danford and associates enrolled 521 previously unevaluated patients who were referred for evaluation of a heart murmur. Sixty-two of these patients were ultimately proven by echocardiographic examination to have PVS (mild, 29; moderate, 27; and severe, 6). Specific difficulties in discriminating PVS from small ventriculoseptal defect (VSD) aortic valve disease, atrial septal defect, and innocent murmurs were identified. There was not a good ability to assess the severity of PVS or the presence of other cardiac defects on the basis of physical examination. Echocardiographic studies are indicated in children with a heart murmur suggestive of PVS.

Comment by Alan H. Friedman, MD, FAAP

This study is a well-constructed assessment of the ability of a clinical expert (in this case a board-certified pediatric cardiologist) to accurately diagnose pulmonary stenosis without using echocardiography. PS is one of the more commonly encountered cardiac pathologies leading to a heart murmur. The physical examination findings are usually marked by the auscultatory findings, which are typically distinctive: a systolic ejection-quality murmur at the upper left sternal border with variable radiation to the back. In addition, a systolic click is frequently appreciated. The echocardiogram is also a sensitive diagnostic tool for PS, and with the use of Doppler and color flow mapping techniques, detailed morphologic and hemodynamic information can be obtained. For example, Doppler tracings across the pulmonary valve can be used in the classification of PS in mild (< 25 mmHg) gradient across the valve, moderate (25 mmHg = valve gradient = 49 mmHg) or severe (= 50 mmHg valve gradient). Danford et al set out to determine the sensitivity and specificity of the expert clinical examination, presumably in part to determine if the relatively high cost of the echocardiographic study could be obviated.

Seven board-certified pediatric cardiologists enrolled a total of 521 consecutive, previously unevaluated pediatric patients who were referred because of a heart murmur in the study. The investigators prospectively recorded their clinical diagnosis and level of confidence in the diagnosis. When PS was suspected, the investigator committed to a pre-echo classification of mild to severe. Each subject then underwent a complete echocardio-graphic study with Doppler tracings.

The median age for all subjects was 2.87 years and there was a slight female predominance (52%). A total of 62 subjects (12%) were found to have PS, and of these, 29 (47%) had mild PS. The more severe the PS, the younger the patient tended to be at the time of first evaluation. Sixteen (26%) of the PS subjects had additional defects found at echocardiography, including atrial septal defects, ventricular septal defects, aortic valve disease, patent ductus arteriosus, and double-outlet right ventricle, among others. These concomitant defects were not recognized prior to the echo. Of the 62

PS patients, 31 (50%) were thought to have PS as the sole pathology prior to echo, yielding a sensitivity of 50%. However, PS appeared on the differential diagnosis list of 14 additional subjects, where the cardiologist was less certain. Of the 459 subjects without PS, 15 were thought to have had PS by the pediatric cardiologist before the echocardiogram, yielding a specificity of nearly 97%.

Several interesting findings came to light when the ability of the cardiologist to accurately classify the PS severity based on the physical examination was examined. Of the four cases of severe PS in which the cardiologist included PS in the differential diagnosis, two were thought to be severe and two were thought to be mild. The majority of cases of mild PS and, for that matter, moderate PS were thought to be mild by the cardiologist when PS appeared on the pre-echo differential diagnosis list. Thus, there was not great success in differentiating whether PS was mild, moderate, or severe based on exam alone.

As Danford et al correctly point out, in order to conclude that echocardiography is not required to support or confirm a diagnosis made by a pediatric cardiologist, the expert examination: 1) must have a high sensitivity and specificity for the diagnosis; 2) errors resulting from reliance on the exam alone must not lead to harmful mismanagement; and 3) the severity of the disease must be graded accurately. It appears as if several of these criteria were not met in this study, most notably the inability to clinically grade the degree of PS. The cardiologists were good at recognizing that mild PS was mild, but much less accurate in discriminating moderate and severe PS from mild cases.

Other studies have shown that an expert clinical examination is effective in discriminating congenital heart disease from an innocent murmur. However, the results from this study suggest that recognizing concomitant heart disease in PS and distinguishing severe PS from mild PS can be difficult when the clinical examination is used in isolation. Thus, Danford et al conclude that an echocardiogram is justified and important in evaluating the child thought to have PS on the basis of physical examination. Incidentally, this study supports the published guidelines of the American Heart Association for the management of PS, which suggest that the echocardiogram provides vital information upon which plans for care and follow-up should be based.1

Reference

1. Driscoll D, et al. Guidelines for evaluation and management of common congenital cardiac problems in infants, children, and adolescents. A statement for healthcare professionals form the Committee on Congenital Cardiac Defects of the Council on Cardiovascular Disease in the Young, American Heart Association. Circulation 1994;90:2180-2188.

Clinical assessment of a heart murmur that has the characteristics of pulmonary stenosis (PS):

    a. is highly reliable in distinguishing PS from other cardiac lesions.
    b. is highly reliable in assessing the severity of pulmonary stenosis.
    c. does not require further assessment with ultrasonography and Doppler.
    d. usually results in a cardiac diagnosis in addition to PS.