Can pro-brain natriuretic peptide be used as a noninvasive predictor of elevated left ventricular diastolic pressures in patients with normal systolic function?

Clinical Application of Biomarkers in Heart Failure with a Preserved Ejection Fraction: A Review

Heart failure with a preserved ejection fraction (HFpEF) is increasingly prevalent and a leading cause of morbidity and mortality worldwide. HFpEF has a complex pathophysiology, with recent evidence suggesting that an interaction of cardiovascular and noncardiovascular comorbidities (e.g. obesity, hypertension, diabetes, coronary artery disease, and chronic kidney disease) induces an inflammatory state that eventually leads to myocardial structural and functional alterations. Current ACCF/AHA guidelines suggest incorporation of biomarkers along with clinical and imaging tools to establish the diagnosis and disease severity in heart failure (HF). However, the majority of data on biomarkers relating to their levels, or their role in accurate diagnosis, prognostication, and disease activity, has been derived from studies in undifferentiated HF or HF with a reduced EF (HFrEF). As the understanding of the mechanisms underlying HFpEF continues to evolve, biomarkers reflecting different pathways including neurohormonal activation, myocardial injury, inflammation, and fibrosis have a clinical utility beyond the diagnostic scope. Accordingly, in this review article we describe the various established and novel plasma biomarkers and their emerging value in diagnosis, prognosis, response, and guiding of targeted therapy in patients with HFpEF.

Can biomarkers help to diagnose early heart failure with preserved ejection fraction?

Early heart failure with preserved ejection fraction (HFpEF) is a frequent disease, but its diagnosis is difficult and relies mostly on the evidence of left ventricular filling pressure (LVFP) elevation during exercise. Several reports have suggested that natriuretic peptides plasma levels reflect exercise-induced increase in LVFP, but they still have significant limitations. In this context, any new laboratory biomarker that can accurately reflect LVFP elevation during exercise is desirable. Recently, cardiotrophin-1, soluble endoglin, ST2, growth differentiation factor 15, galectin-3, and other new laboratory markers associated with LVFP have emerged. However, the current data on the relationship of these biomarkers and diastolic dysfunction are limited to resting conditions. Therefore, their secretion deserves to be tested under the exercise to determine their potential role in making a diagnosis of early HFpEF.

Usefulness of pulmonary capillary wedge pressure as a correlate of left ventricular filling pressures in pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is characterized by a pulmonary capillary wedge pressure (PCWP) of ≤15 mm Hg, given a normal left ventricular filling pressure (LVFP). However, recent studies have shown that, in PAH patients, diagnosis based on PCWP can erroneously classify a significant number of patients compared with diagnosis based on left ventricular end-diastolic pressure (LVEDP). Therefore, we sought to compare the diagnostic accuracy of end-expiratory PCWP and LVEDP measurements in patients suspected of having pulmonary hypertension (PH).

METHODS

We reviewed the hemodynamic data from 122 patients suspected of having PH who underwent simultaneous right- and left-side heart catheterizations at a PH referral center from 2006 to 2011.

RESULTS

PH was diagnosed in 105 patients, 79% of whom (n = 83) showed a pre-capillary pattern according to the LVEDP measurement. Ninety percent of patients with PCWP ≤15 mm Hg were correctly classified as having pre-capillary PH. However, 39% of patients with a PCWP >15 mm Hg had LVEDP ≤15 mm Hg and would have been erroneously diagnosed with pulmonary venous hypertension based on their PCWP measurements alone. The sensitivity and specificity was 0.89 and 0.64, respectively. A Bland-Altman analysis of the PCWP and LVEDP measurements revealed a mean bias of 0.3 mm Hg with 95% limits of agreement of -7.2 to 7.8 mm Hg.

CONCLUSIONS

A PCWP ≤15 mm Hg was found to be a reliable indicator of normal LVFP in pre-capillary PH patients. When measured properly and analyzed in the clinical context, PCWP is a valuable tool for accurate diagnosis of PAH.

Current practice for determining pulmonary capillary wedge pressure predisposes to serious errors in the classification of patients with pulmonary hypertension

BACKGROUND

Accurate measurement of left ventricular filling pressure is important to distinguish between category 1 pulmonary arterial hypertension (PAH) and category 2 pulmonary hypertension (PH) from left heart diseases (PH-HFpEF). We hypothesized that the common practice of relying on the digitized mean pulmonary capillary wedge pressure (PCWP-digital) results in erroneous recordings, whereas end-expiratory PCWP measurements (PCWP-end Exp) provide a reliable surrogate measurement for end-expiratory left ventricular end-diastolic pressure (LVEDP-end Exp-end Exp).

METHODS

We prospectively performed left and right cardiac catheterization on 61 patients referred for evaluation of PH and compared the LVEDP-end Exp to end-expiration to the (a) PCWP-end Exp and (b) PCWP-digital.

RESULTS

The PCWP-end Exp was a more reliable reflection of LVEDP-end Exp (mean 13.2 mm Hg vs 12.4 mm Hg; P, nonsignificant) than PCWP-digital (mean 8.0 mm Hg vs 12.4 mm Hg, P < .05). Bland-Altman analysis of PCWP-digital and LVEDP-end Exp revealed a mean bias of -4.4 mm Hg with 95% limits of agreement of -11.3 to 2.5 mm Hg. Bland-Altman analysis of PCWP-end Exp and LVEDP-end Exp revealed a mean bias of 0.9 mm Hg with 95% limits of agreement of -5.2 to 6.9 mm Hg. If PCWP-digital were used to define LVEDP-end Exp, 14 (27%) of 52 patients would have been misclassified as having PAH rather than PH-HFpEF. Patients with obesity and hypoxia were particularly more likely to be misclassified as PAH instead of PH-HFpEF if PCWP-digital was used to define LVEDP-end Exp (odds ratio 8.1, 95% CI 1.644-40.04, P = .01).

CONCLUSIONS

The common practice of using PCWP-digital instead of PCWP-end Exp results in a significant underestimation of LVEDP-end Exp. In our study, this translated to nearly 30% of patients being misclassified as having PAH rather than PH from HFpEF.

Prognostic value of B-type natriuretic peptide for cardiovascular events independent of left ventricular end-diastolic pressure

BACKGROUND

B-type natriuretic peptide (BNP) correlates with left ventricular (LV) end-diastolic pressure (LVEDP) and predicts cardiovascular events. We sought to determine whether BNP has prognostic value independent of LVEDP.

METHODS

Eligible patients were referred for coronary angiography between March 15, 2002, and April 30, 2008, at a single institution. Inclusion criteria were having BNP, LV ejection fraction (EF), and LVEDP measured within 24 hours of the angiogram. The predictive value of BNP for events independent of LVEDP, EF, and other confounders was determined.

RESULTS

The study population (n = 1,059) was followed for a mean of 1.8 +/- 1.7 years. The mean age was 63 +/- 13 years. The median BNP value was 182 pg/mL; 59% of patients had LVEDP > or =16 mm Hg. B-type natriuretic peptide and LVEDP had a modest but statistically significant correlation (r = 0.24, P < .0001). After adjustment for LVEDP and EF, the hazard ratio for the composite outcome of heart failure admissions and death was 1.37 (1.21-1.55, P < .0001) per unit increase in log BNP. After adjustment for BNP and EF, LVEDP did not predict heart failure admissions and death (hazard ratio 1.05 [0.95-1.10], per 5-mm Hg increase, P = .30). Those with BNP value below the median had longer event-free survival as compared to those with BNP value above the median, regardless of the LVEDP strata (log-rank P < .0001 for LVEDP > or =16 and <16 mm Hg).

CONCLUSION

B-type natriuretic peptide has prognostic value independent of LVEDP in this cohort with suspected coronary artery disease, suggesting this biomarker is not just a prognostic surrogate for elevated LV filling pressure.

Natriuretic peptides and filling pressure at rest and stress

The natriuretic peptides are a family of compounds secreted from the atria and ventricles in response to a variety of stimuli, including increased wall stress, tachycardia, and myocardial ischemia. Increases in the levels of these compounds correlate with increased left-ventricular filling pressure in patients with systolic dysfunction, although the production of the compounds from severely impaired ventricles may be reduced, leading to lower than anticipated levels in severe heart failure. The association of increased natriuretic peptides with diastolic dysfunction has been variable, with no elevation reported in many patients with mild dysfunction. These patients with mild diastolic dysfunction become symptomatic with exercise, in association with increased filling pressure with stress, which may be documented using echocardiography or possibly the natriuretic peptide response. However, the variability of peptide levels within individuals may pose a problem to the interpretation of sequential data in response to exercise or therapies.

Effects of hemoglobin concentration and creatinine clearance in pro-B-type natriuretic peptide-based left ventricular filling pressure prediction in patients with preserved left ventricular systolic function

Although N-terminal pro-B-type natriuretic peptide (pro-BNP) has been shown to correlate with left ventricular (LV) filling pressure, pro-BNP-based LV filling pressure prediction has some limitations due to several factors that affect pro-BNP. The aim of this study was to evaluate the effects of blood hemoglobin concentration and creatinine clearance (CCr) on pro-BNP-based LV filling pressure prediction in patients with preserved LV systolic function. A total of 421 consecutive patients referred for coronary angiography underwent LV pressure measurement by fluid-filled catheters. Patients with plasma creatinine levels>or=1.5 mg/dl and LV ejection fractions<50% were excluded. LV diastolic pressures and echocardiographic parameters were compared with pro-BNP levels in 281 patients. Blood hemoglobin levels and CCr were measured simultaneously. Log pro-BNP was independently correlated with hemoglobin concentration (beta=-0.261, p<0.001), CCr (beta=-0.230, p<0.001) and LV pre-A-wave pressure (beta=0.384, p<0.001). A pro-BNP level of 124 pg/ml was the optimal cutoff for LV pre-A-wave pressure>15 mm Hg in all patients (sensitivity 67%, specificity 67%, p<0.001). However, by subclassification according to hemoglobin and CCr tertiles, optimal cut-off values varied significantly, and their predictive accuracies could be improved (from 89 to 331 pg/dl, with diagnostic accuracy up to 79%). In conclusion, in the pro-BNP-based prediction of elevated LV filling pressure, subclassification on the basis of hemoglobin concentration and CCr should be considered in patients with preserved LV systolic and renal function.

Combining tissue Doppler echocardiography and B-type natriuretic peptide in the evaluation of left ventricular filling pressures: review of the literature and clinical recommendations

Tissue Doppler imaging is an echocardiographic technique that directly measures myocardial velocities. Diastolic tissue Doppler velocities reflect myocardial relaxation, and in combination with conventional Doppler measurements, ratios (transmitral early diastolic velocity/mitral annular early diastolic velocity [E/Ea]) have been developed to noninvasively estimate left ventricular (LV) filling pressure. Consequently, mitral E/Ea can help to establish the presence of clinical congestive heart failure in patients with dyspnea. However, E/Ea has a significant 'gray zone', and is not well validated in nonsinus rhythm and mitral valve disease. B-type natriuretic peptide (BNP) is a protein released by the ventricles in the presence of myocytic stretch, and has been correlated to LV filling pressure and, independently, to other cardiac morphological abnormalities. In addition, BNP is significantly affected by age, sex, renal function and obesity. Given its correlation with multiple cardiac variables, BNP has high sensitivity, but low specificity, for the detection of elevated LV filling pressures. Taking into account the respective strengths and limitations of BNP and mitral E/Ea, algorithms combining them can be used to more accurately estimate LV filling pressures in patients presenting with dyspnea.

Incremental value of measuring the time difference between onset of mitral inflow and onset of early diastolic mitral annulus velocity for the evaluation of left ventricular diastolic pressures in patients with normal systolic function and an indeterminate E/E'

This study sought to evaluate the incremental value of the time interval between the onset of early transmitral flow velocity (E) and the onset of early diastolic velocity (E') of the mitral annulus for the prediction of left ventricular (LV) end-diastolic pressure (EDP) in the presence of a "gray zone" value for E/E'. An E/E' ratio of 8 to 15 is classified as the "gray zone" for the estimation of LVEDP. Recently, it was suggested that prolongation of the time interval between the onset of E and E' (T(E'-E)) might indicate elevated filling pressure. Simultaneous left-sided cardiac catheterization and Doppler echocardiography were performed in 74 patients with normal systolic function. T(E'-E) was calculated as the time interval between the peak of the R wave and the onset of E' and between the peak of the R wave and the onset of E. Of the 74 patients enrolled, 55 (27 men, mean age 59 years) who had E/E' ratios of 8 to 15 were analyzed. LVEDP was elevated (>18 mm Hg) in 34 patients (62%). There was no significant difference in Doppler echocardiographic parameters and N-terminal pro-brain natriuretic peptide levels between those with normal and high LVEDP, except T(E'-E), which was significantly longer in the latter (19.0 +/- 17.8 vs 35.0 +/- 17.0 ms, p = 0.002). The receiver-operating characteristic curves for the prediction of high LVEDP showed the largest area under the curve (0.760) for T(E'-E). In multivariate analysis, T(E'-E) added significant information to the other parameters in the prediction of high LVEDP (p = 0.029). In conclusion, T(E'-E) may have an incremental value in the estimation of LVEDP in patients with normal systolic function and indeterminate E/E' ratios.

Usefulness of serum N-terminal pro-brain natriuretic peptide to predict in-stent restenosis in patients with preserved left ventricular function and normal troponin I levels

The level of N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) is a strong predictor of mortality in patients with acute coronary syndrome and may be a strong prognostic marker in patients with chronic coronary artery disease. We investigated whether NT-pro-BNP could predict in-stent restenosis (ISR) in asymptomatic patients with preserved left ventricular (LV) systolic function who underwent percutaneous coronary intervention. We measured serum NT-pro-BNP levels in 249 patients (61 +/- 9 years of age; 73% men) with preserved LV systolic function (ejection fraction >50%) who underwent follow-up coronary angiography. Initial diagnoses were stable angina in 50 (20%), unstable angina in 133 (53%), and myocardial infarction in 66 (27%). Baseline characteristics between groups with ISR (n = 92) and without ISR (n = 157) were similar. The level of NT-pro-BNP was higher in patients with ISR than in those without ISR (222 +/- 327 vs 94 +/- 136 pg/ml, p = 0.001). In the ISR group, NT-pro-BNP level was higher in patients with left anterior descending coronary artery ISR (n = 53, 312 +/- 479 pg/ml) than in those with left circumflex coronary artery ISR (n = 19, 115 +/- 98 pg/ml, p = 0.018). At the standard cutoff of >200 pg/ml, a high NT-pro-BNP level indicated a high probability of ISR (odds ratio 2.18, 95% confidence interval 1.0 to 4.5, p = 0.038). In multivariate analysis, NT-pro-BNP level was an independent predictor for ISR. In conclusion, NT-pro-BNP could be a predictor of ISR in asymptomatic patients with preserved LV systolic function.

Diastolic stress echocardiography: hemodynamic validation and clinical significance of estimation of ventricular filling pressure with exercise

OBJECTIVES

Our study attempted to validate a Doppler index of diastolic filling (E/E') during exercise with simultaneously measured left ventricular diastolic pressure (LVDP), investigate its association with exercise capacity, and understand which patients to select for testing.

BACKGROUND

The ratio of early diastolic transmitral velocity to early diastolic tissue velocity approximates LVDP at rest, but there is limited validation of exercise E/E' with invasive hemodynamic measurement, and its clinical implications are unclear.

METHODS

The ratio of early diastolic transmitral velocity to early diastolic tissue velocity was measured at rest and during supine cycle ergometry in 37 patients undergoing left heart catheterization. In addition to correlation between invasive and estimated LVDP, the accuracy of different cutoffs for identification of elevated LVDP (>15 mm Hg) was determined at both rest and exercise. Doppler index of diastolic filling was also measured at rest and immediately after maximal treadmill exercise in 166 patients to investigate the association between exercise E/E' and exercise capacity (<8 metabolic equivalents [METs]).

RESULTS

In patients undergoing invasive measurement, nine (24%) had elevation of LVDP only during exercise. There was a good correlation between E/E' and LVDP at rest (r = 0.67) and during exercise (r = 0.59), and the regressions at rest and exercise corresponded closely. Receiver-operator curve analysis indicated that a cutoff value of 13 for exercise E/E' identified patients with an elevated LVDP during exercise. A post-exercise E/E' >13 was highly specific (90%) for reduced exercise capacity, and even after classification of resting E/E', exercise E/E' permitted classification of patients with exercise capacity <8 METs or > or =8 METs.

CONCLUSIONS

The ratio of early diastolic transmitral velocity to early diastolic tissue velocity correlates with invasively measured LVDP during exercise. It can be used to reliably identify patients with elevated LVDP during exercise and reduced exercise capacity.