Elevation of the plasma concentrations of immunoreactive atrial natriuretic peptide (ANP) was observed in canine chronic right heart failure (RHF) secondary to right ventricular (RV) pressure overload. Pressure overload on the right heart was gradually increased using an inflatable cuff. The interval between banding and the onset of RHF was 152 ± 52 days. Seventeen RHF dogs were produced and divided into Group I (n = 11) and Group II (n = 6). At the onset of RHF, Group I dogs were either sacrificed for study of the heart, or unbanded to allow recovery from RHF. The dogs in Group II were maintained in RHF for 3 additional months before being either sacrificed or unbanded. Following unbanding, the ANP level of Group I recovered from 108 ± 36 (n = 11) to 20 ± 6 pg/ml (n = 6) at 1 month and was maintained at 27 ± 7 pg/ml (baseline, 21 ± 5 pg/ml, n = 11) at 4 months. ANP levels of Group II declined from 165 ± 55 (n = 6) to 87 ± 2 pg/ml (n = 3) at 1 month and further decreased to 42 ± 14 pg/ml (n = 3) 4 months after unbanding. Thus, compared to Group I, Group II had a high ANP level before unbanding and a delay in recovery of the ANP levels despite normalization of the right atrial pressure (RAP). Four months after release of pressure overload, the right atrial hypertrophy persisted in the unbanded dogs; however, Group I unbanded dogs showed a better reversal of the right atrial hypertrophy than Group II unbanded dogs. We concluded that in chronic RHF, decrease of the elevated ANP levels depends on normalization of the right atrial pressure and persistent mild increase of ANP levels may correlate with the remaining hypertrophy of the right atrium.
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