There is a significant latent phase of left ventricular dysfunction during which patients are asymptomatic. Recent advances in medicine have been shown to decrease mortality and slow the progression of left ventricular dysfunction. To accomplish this during the latent phase, identification of those with left ventricular dysfunction is important. The use of cardiac imaging can identify this problem, but it is limited as a screening tool. Brain natriuretic peptide (BNP) is a serum compound that is elevated in patients with chronic heart failure or asymptomatic left ventricular systolic dysfunction. It has been shown that BNP can accurately indicate left ventricular systolic dysfunction in the general population. However, there are conflicting data on the diagnostic value of a BNP test. In addition, the cost-effectiveness of using BNP levels as a screen for this dysfunction has not been established. Nielsen and colleagues assessed the cost-effectiveness of using BNP levels with other clinical parameters as a screening tool for identifying left ventricular systolic dysfunction in the general population.
The participants in the study were a random sample of the general population who attended the Third Glasgow Monica Risk Factor Survey. The population that attended was similar to those who were invited except they tended to be more affluent and smoked less. The prevalence of hypertension and coronary heart disease was similar to that in the general population. Information obtained during the session included a self-reported questionnaire, blood pressure measurement, electrocardiography, echocardiography, and BNP level. The participants were then divided into three risk groups: group 1, those with symptomatic heart disease; group 2, those with blood pressure greater than 160/95 mm Hg and/or abnormal electrocardiogram (high risk); and group 3, those with no risk factors (low risk). The BNP test was adjusted to provide high sensitivity.
Left ventricular systolic dysfunction was identified in 0.7 percent of group 3, 6 percent of group 2, and 19 percent of group 1. Sensitivity of BNP testing in identifying left ventricular systolic dysfunction was 83 percent in the low-risk group, 94 percent in the high-risk group, and 92 percent in the symptomatic group. The negative predictive value was 99.8, 99.0, and 95.1 percent in each group, respectively. In low-risk subjects, the concentration of BNP was not associated with left ventricular systolic dysfunction, but in the high-risk and symptomatic patients it had a significant association. Using BNP levels as a screen for high-risk patients before echocardiography could reduce the cost per detected case by 26 percent.
The authors conclude that a simple questionnaire and blood pressure measurements can be used as the first rule-out test for identifying patients at risk for left ventricular systolic dysfunction. BNP testing can be used in patients at high risk for this dysfunction, and when BNP levels are elevated, it should be followed with echocardiography. In those at high risk with a normal BNP level, an echocardiogram is not necessary. This strategy is also cost-effective and could reduce unnecessary testing.