Incremental importance of peak-exercise plasma levels of endothelin-1 and natriuretic peptides in chronic heart failure

Prognostic Importance of Exercise Brain Natriuretic Peptide in Asymptomatic Chronic Organic Severe Mitral Regurgitation: An Observational Study

BACKGROUND

The optimal timing of surgery in patients with chronic organic severe mitral regurgitation (MR) continues to be debated, especially for those who are asymptomatic. The aim of the study was to determine independent and additive prognostic value of exercise brain natriuretic peptide (eBNP) in patients with severe asymptomatic MR and normal left ventricular ejection fraction (LVEF).

METHODS

Two hundred twenty-three consecutive patients with severe MR defined by effective regurgitant orifice (ERO) area ≥ 40 mm² and/or residual volume ≥ 60 mL, LVEF > 60%, and normal LV end-systolic diameter < 40 mm underwent symptom limited exercise treadmill test (TMT). Echocardiography was done immediately after exercise. Data were obtained within 3 minutes of peak exercise. BNP levels were assessed before echo (after 30 minutes of supine rest) and at exercise (i.e., within the 3 minutes of the end of effort). Patients were followed up every 3 months up to 15 months for major adverse cardiac events (MACEs) (cardiovascular death, need for mitral valve surgery and hospitalization for acute pulmonary edema or heart failure).

RESULTS

Mean age was 31.2 ± 9 years (range: 18 - 40) with majority being male (n = 153; 68%). Etiologies were rheumatic (n = 201; 90%), mitral valve prolapse (n = 17; 7.6%) and hypertrophic cardiomyopathy (n = 5; 2.4%). BNP level significantly increased from rest (65.24 ± 43.92 pg/mL; median: 43.5 pg/mL) to exercise (100.24 ± 98.24 pg/mL; median: 66.5 pg/mL; P < 0.001). Patients were divided into three tertiles according to eBNP levels (T₁ = 15 - 44; T₂ = 45 - 104; T₃ = 105 - 400). There was trend for significantly lower exercise time in T₃. During TMT, 66 (29.5%) stopped exercise due to dyspnea. They had similar resting BNP level compared with others but had significantly higher eBNP level (136 ± 109.7 pg/mL vs. 84.88 ± 90.2 pg/mL; P < 0.001). During follow-up (15 months), MACE occurred in 83 patients (37.2%): mitral valve replacement (MVR) in 59 patients (symptomatic: 43; LV dilatation or dysfunction: 9; both symptoms and dilatation/dysfunction: 7), 17 hospitalizations for congestive heart failure, five patients developing acute pulmonary edema and atrial fibrillation in remaining two patients. This was 7.6%, 35% and 69% in T₁, T₂ and T₃, respectively and had significantly higher eBNP level than without any event (165 ± 119 pg/mL vs. 57 ± 48 pg/mL; P < 0.001). Using receiver operating characteristic curve analysis, the best cut-off value of eBNP level to predict cardiac events was 90 pg/mL (sensitivity: 75%; specificity: 88.6%; positive predictive value: 79%; negative predictive value: 83.9%).

CONCLUSION

In asymptomatic patients, eBNP level provides incremental prognostic value beyond echocardiographic data and those with elevated eBNP should be considered at high risk for reduced event-free survival and might be considered for early MVR.

Myocardial performance after successful intervention for native aortic coarctation

Coarctation of the aorta is associated with increased risk for hypertension in adulthood, despite successful repair. The intrinsic mechanisms underscoring hypertension and left ventricular performance in these patients, however, remains to be determined. Our objective was to evaluate left ventricular performance by means of echocardiographic and biochemical parameters at midterm follow-up in normotensive children who have had undergone successful surgical or catheter interventional treatment of coarctation with a residual gradient of less than 20 mmHg at rest. We studied prospectively 14 patients with native aortic coarctation who underwent surgery or balloon angioplasty, the cohort made up of equal numbers of boys and girls, and having a mean age of 8.5 plus or minus 4 years. We also studied 30 age-matched healthy subjects, measuring mitral inflow pulsed wave signals, isovolumic relaxation and contraction times, myocardial performance index parameters, and levels of B-type natriuretic peptide and endothelin-1 in both groups. We found no differences in systolic blood pressure at rest between the patients and their controls. The ventricular septal diastolic dimensions, left ventricular posterior wall dimensions, mitral valve E wave, deceleration time, isovolumic relaxation time, isovolumic contraction time and myocardial performance index were all significantly increased in the patients. Levels of plasma B-type natriuretic peptide and endothelin-1 were also significantly higher in the patients when compared to the control group. We conclude that aortic coarctation is a chronic disease characterized by persistency of myocardial and vascular alterations. The elevated levels of plasma b-type natriuretic peptide and endothelin-1 may be indicative of late onset hypertension after successful treatment of native coarctation in early childhood.

Characteristics of the increase in plasma brain natriuretic peptide level in left ventricular systolic dysfunction, associated with muscular dystrophy in comparison with idiopathic dilated cardiomyopathy

To determine whether the plasma brain natriuretic peptide level increases differentially in muscular dystrophy and idiopathic dilated cardiomyopathy, we investigated the plasma brain natriuretic peptide level and echocardiographic parameters in patients with similarly low left ventricular ejection fraction. The plasma brain natriuretic peptide level was lower, and the left ventricular end-diastolic diameter was shorter in the patients with muscular dystrophy than in those with idiopathic dilated cardiomyopathy. The correlation between the plasma brain natriuretic peptide and left ventricular ejection fraction was shifted downward in the patients with muscular dystrophy compared with those with idiopathic dilated cardiomyopathy. Those between the brain natriuretic peptide and left ventricular end-diastolic diameter were superimposable, although the data from the muscular dystrophy patients were located at the shorter left ventricular end-diastolic diameter side. The plasma brain natriuretic peptide level may differentially increase in the two diseases with similar left ventricular systolic dysfunction. Differences in the left ventricular distension and in the physical activity might explain at least partially the different plasma brain natriuretic peptide levels.

Effect of exercise on natriuretic peptides in plasma and urine in chronic heart failure

BACKGROUND

Plasma atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are elevated in chronic heart failure (CHF). ANP is known to be increased during exercise in healthy subjects and CHF, while the response in BNP during exercise is less clear and does not exist in C-type natriuretic peptide (CNP) and aquaporin-2 (AQP2) in either healthy subjects or CHF.

METHODS

Eleven patients with CHF and eleven healthy subjects performed a maximal aerobic exercise test. ANP and BNP in plasma were determined every 3 min and at maximum exercise by radioimmunoassay (RIA) and CNP and AQP2 in urine were determined before and after the exercise test by RIA.

RESULTS

The absolute increase in BNP during exercise was higher in patients with CHF (CHF: 4.1 pmol/l; healthy subjects: 1.3 pmol/l, P<0.05) and was positively correlated to BNP at rest (P<0.05), while the absolute increase in ANP during exercise was the same in the two groups (CHF: 4.2 pmol/l; healthy subjects: 6.8 pmol/l, not significant, NS). In CHF, exercise did not change either u-CNP excretion (rest: 9.8 ng/mmol creatinine; after exercise: 8.8 ng/mmol, NS) or u-AQP2 (rest: 466 ng/mmol creatinine; after exercise: 517 ng/mmol creatinine, NS) as well as in healthy subjects where u-CNP (rest: 9.7 ng/mmol creatinine; after exercise: 9.2 ng/mmol creatinine) and u-AQP2 (rest: 283 ng/mmol creatinine; after exercise: 307 ng/mmol creatinine) were the same at rest and after exercise.

CONCLUSION

The absolute increase in BNP during exercise is higher in patients with CHF compared to healthy subjects. It is suggested that this is a compensatory phenomenon to improve the exercise capacity in CHF, and that BNP is a more important factor in cardiovascular homeostasis during exercise in CHF than ANP.

Reference ranges for natriuretic peptides for diagnostic use are dependent on age, gender and heart rate

BACKGROUND

Plasma natriuretic peptide levels may be useful in the diagnosis of heart failure. The available natriuretic peptide assays differ markedly in their performance characteristics. In addition, plasma levels are influenced by a number of factors including age and gender.

AIMS

The aim of this study was to describe, in a healthy population, the influence of clinical and echocardiographic parameters on three natriuretic peptide moieties.

METHODS

1360 individuals were screened for the presence of left ventricular systolic dysfunction. We identified a cohort (n=720) of men aged 45-80 years (n=417) and women aged 55-80 years (n=303). None had history of cardiovascular disease or were taking any cardiovascular medication. All had normal echocardiographic and ECG findings. B-type (BNP), N-terminal pro-B-type (N-BNP) and N-terminal pro-Atrial (N-ANP) natriuretic peptides were assayed using in-house immunoluminometric assays.

RESULTS

Of the considered clinical variables, only gender and heart rate (each P<0.005) were independently associated with levels of all three natriuretic peptides. Plasma levels of N-ANP (15%), BNP (25%) and N-BNP (75%) were higher in women compared to men. An increase in heart rate of 10 bpm corresponded to a reduction of 9% in N-ANP or BNP and a 15% reduction in N-BNP. Each 10 years of age was associated with 16% and 74% increase in ANP and N-BNP levels, respectively, but no increase in plasma BNP. Left ventricular ejection fraction could be assessed in 582 (81%) subjects and correlated positively with N-ANP (r(s)=6.48x10(-3), P<0.001) and BNP (r(s)=2.4x10(-2), P<0.001) but not N-BNP (P=0.405). No parameter of diastolic function was associated with any peptide level.

CONCLUSIONS

In this healthy population, plasma levels of N-ANP, BNP and N-BNP were variably influenced by clinical covariates. While all three peptides were higher in women, only N-ANP and N-BNP were influenced by age. Levels of all peptides were inversely correlated with heart rate. Using this immunoluminometric assay, plasma BNP is not influenced by age, in contrast to N-ANP and N-BNP. In constructing normal ranges for diagnostic use, covariates such as age and gender must be considered, in addition to the format of assay being used.

Plasma endothelin-1 levels and clinical correlates in patients with chronic heart failure

BACKGROUND

Endothelin-1 (ET-1) is a potent vasoconstrictor peptide, and patients with chronic heart failure (CHF) are reported to have high plasma ET-1 levels. The aim of this study was to investigate the relation between plasma ET-1 levels and clinical correlates in patients with CHF. The effects of maximal exercise on plasma ET-1 levels were also investigated.

METHODS

Plasma concentrations of ET-1, norepinephrine, and atrial and brain natriuretic peptide (ANP and BNP) both at rest and after maximal cardiopulmonary exercise test were determined in 100 patients with CHF (60 +/- 12 years, New York Heart Association [NYHA] class I-III, left ventricular ejection fraction [LVEF]=36 +/- 8%, peak oxygen uptake [VO2] = 18.2 +/- 5.0 mL/min/kg) and 27 controls.

RESULTS

Patients with NYHA class II and III CHF had higher ET-1 levels (controls, NYHA class I, II, III: 2.1 +/- 0.6, 2.1 +/- 1.0, 2.6 +/- 0.9, 3.4 +/- 0.8 pg/mL, analysis of variance P <.0001). Maximal exercise did not alter ET-1 levels in controls or in each CHF subgroup. When all CHF patients were analyzed together, cardiothoracic ratio (P<.01), peak VO2 (P<.001), plasma norepinephrine (P<.01), plasma ANP (P<.01), and plasma BNP (P<.001) were significantly related with resting ET-1 levels on univariate analysis. Multivariate analysis revealed peak VO2 and plasma BNP levels showed an independent and significant relationship with the resting plasma ET-1 levels.

CONCLUSIONS

Resting ET-1 levels were increased in symptomatic patients with CHF, and maximal exercise did not increase ET-1 levels. Peak VO2 and plasma BNP levels were independently associated with resting plasma ET-1 levels in patients with CHF.