The Relationship between Plasma Natriuretic Peptide Levels and Left Ventricular Function in Hypertrophic Cardiomyopathy at Rest and Peak Stress

Abstract

Background: It has been shown that resting plasma levels of atrial natriuretic peptide (ANP) relate to exercise capacity in patients with hypertrophic cardiomyopathy (HCM). However, the relationship between natriuretic peptides and carQac structure and physiology, particularly with stress has not been determined in such patients. Methods: The relationships between plasma ANP and B-type natriuretic peptide (BNP) and left ventricular (LV) cavity measurements and function were investigated in 21 patients with HCM (age 54k16 years, 11 male), using Doppler echocardiography at rest and peak dobutamine stress (conventional protocol). All patients had normal LV systolic function (FS>30%). Results: All patients developed left ventricular outflow tract (LVOT) obstruction and dyspncea at peak stress (LVOT gradient at rest 31*24 mmHg. peak stress 1082.32, p<O.OOOI). Stress resulted in an increase in plasma levels of ANP (rest vs peak, 20.9k21.1 vs 31.a33.5 pmoVL) and BNP (31.2244.0 vs 45.368.6 pmoVL, both ~ 4 . 0 5 ) . AT REST levels of ANP and BNP were strongly correlated (Rz0.88, p<O.OOOI); ANP levels also correlated with LV dimensions (end diastolic R4.61; end systolic R4.45) and resting LVOT gradient (R=0.44, all p<0.05); BNP levels showed a similar correlation with LV dimensions (end diastolic R=0.67; end systolic R a . 4 9 , p<0.05) but not with LVOT gradient. AT STRESS: The two peptides remained closely related (R=0.91, p<O.OOOI). However, the association with LV measurements was lost. No association was found between peptide level and LVOT gradient at peak stress. Conclusion: Our results confirm previous findings in patients with heart failure, where resting natriuretic peptide levels correlate with ventricular function. It appears that the development of LVOT obstruction in patients with HCM severs this relationship. Despite this, ANP and BNP levels remain closely related. Further assessment of possible links with other indices of LV function is needed.