Effect of cardiac tamponade on atrial natriuretic peptide concentrations: influence of stretch and pressure

Neuroendocrine changes in chronic cardiac failure

Numerous hormonal and neuroendocrine changes have been described in patients with chronic cardiac failure. These affect the balance of vasodilator and vasoconstrictor factors in favour of the latter, to the detriment of the circulation. Whether this is a reaction to central cardiac (haemodynamic) abnormalities, or is an integral part of the syndrome of heart failure, remains to be determined. Catecholamine levels are increased, especially in severe heart failure, and contribute to the vasoconstriction and probably also to lethal ventricular arrhythmias. The renin-angiotensin-aldosterone system (RAAS) is also activated, causing fluid retention and further vasoconstriction. In the earlier stages, some of this increase may be iatrogenic due to the use of loop diuretics or inhibitors of angiotensin converting enzyme, but there is evidence for independent RAAS activation in more severe grades of heart failure. The role of vasoconstrictor peptides such as neuropeptide Y and endothelin is briefly considered. Counterbalancing these are vasodilator peptides, in particular atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP). The possibility of therapeutic interventions to increase circulating natriuretic hormone levels is discussed.

Atrial wall tension changes and the release of atrial natriuretic factor on relief of cardiac tamponade

Cardiac tamponade causes elevation and equalization of cardiac filling pressures, sodium and water retention, and a paradoxically low plasma atrial natriuretic factor (ANF) concentration despite increased intraatrial pressures. Recent reports suggested that plasma ANF concentrations rise after relief of tamponade. The purposes of the present study were (1) to determine the time course and extent of ANF release on relief of cardiac tamponade; (2) to measure the atrial transmural wall pressures, atrial sizes, and atrial wall tension changes associated with relief of tamponade; and (3) to determine the biologic activity of elevated plasma ANF during and after relief of tamponade. We sampled blood for ANF and cyclic guanosine monophosphate (cGMP) immediately before and up to 24 hours after relief of cardiac tamponade in 10 patients. Atrial and pericardial pressures were measured immediately before and shortly after pericardiocentesis, and atrial dimensions were determined by two-dimensional echocardiography before and within 1 hour after the tap. Urine volumes were measured in 8-hour increments before and after the procedure. Relief of cardiac tamponade was associated with a prompt and massive increase in plasma ANF concentrations, reaching pharmacologically active levels. The rise in ANF was negatively correlated with atrial pressures but positively correlated with atrial transmural pressures, atrial size, and calculated wall tension. Plasma ANF levels peaked at 515 +/- 95 pg/ml 40 minutes after relief of tamponade and leveled off at 140% to 180% of the pretap concentrations. Plasma cGMP exhibited a slightly delayed but similar time course to the rise in ANF levels, and urine flow rate increased fourfold in the 8 hours after relief of tamponade.(ABSTRACT TRUNCATED AT 250 WORDS)

Response of atrial natriuretic factor to surgical pericardial drainage in patients with chronic pericardial effusion

Previous studies have demonstrated the importance of atrial transmural pressure in the secretion of atrial natriuretic peptide. These studies have been performed in patients with pericardial effusion and hemodynamic compromise. The response of atrial natriuretic peptide to the drainage of chronic pericardial effusion without clinical evidence of tamponade is unknown. We studied 13 patients with chronic abundant pericardial effusion but without hemodynamic compromise. Blood samples for hormonal determinations were drawn before and after surgical pericardiocentesis. Right atrial pressure was measured during the procedure. Drainage induced a significant increase of atrial natriuretic peptide (from 12 +/- 3.9 to 105 +/- 22.8 pmol/l, P < 0.001, mean +/- S.E.M.), correlated with the fall in right atrial pressure (from 7.65 +/- 1.18 to 4.31 +/- 1.46 mmHg, P < 0.05, r = 0.68, P = 0.01). This increase was inversely correlated with the rise of mean blood pressure after surgery (from 84 +/- 2.37 to 100 +/- 5.3 mmHg, P < 0.05, r = 0.65, P < 0.02). Plasma renin activity decreased after drainage (from 8.12 +/- 2.57 to 3.27 +/- 0.65 ng/ml/h, P < 0.05). Surgery induced an increase of plasma levels of aldosterone (from 811 +/- 241 to 1199 +/- 249 pmol/l, P < 0.05), which were reduced after pericardiocentesis (371 +/- 102 pmol/l, P < 0.02). In patients with chronic abundant pericardial effusion, surgical pericardiocentesis induced a significant increase of atrial natriuretic peptide, correlated with a fall in right atrial pressure. The increase of atrial natriuretic peptide was similar than in patients with tamponade, despite a moderate fall in right atrial pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

The pericardium acts as a restricting factor on the release of ANF (1-98) and ANF (99-126) after volume loading in pigs

The stimulus for secretion of the atrial peptides from the heart is a mechanical distension of the atria. We studied the changes in plasma levels of immunoreactive ANF (1-98) and ANF (99-126) after volume loading (NaCl 0.9%, 50 ml/kg in 10 min) in pigs that had their pericardium opened (peric-, n = 8) and compared these changes to those of pigs subjected to sham operation (peric+, n = 8). For irANF (99-126), the maximum increase was achieved 10 min after the start of loading: 18.6 +/- 5.5 pmol/l to 31.4 +/- 15.6 pmol/l. (P < 0.05) in peric+ and 23.9 +/- 6.5 pmol/l to 110.2 +/- 46.2 pmol/l (P < 0.05) in peric-. The maximum increase in irANF (1-98) took place after 15 min: 658.8 +/- 223.9 pmol/l to 791.0 +/- 229.4 pmol/l (P < 0.05) in peric+ and 769.9 +/- 228.5 pmol/l to 1136.7 +/- 348.6 pmol/l (P < 0.05) in peric-. For both peptides the maximal increase after loading was significantly greater when the pericardium had been removed. The results demonstrate that the intact pericardium restricts peptide release secondary to volume infusion in closed-chest pigs.

Atrial natriuretic peptide in stable and decompensated chronic obstructive pulmonary disease

BACKGROUND

Plasma levels of atrial natriuretic peptide (ANP) are elevated in patients with chronic obstructive pulmonary disease (COPD) and may have a role in preventing oedema formation in these patients.

METHODS

Plasma ANP levels were measured in 60 patients with COPD and these measurements were related to pulmonary haemodynamics, response to treatment during exacerbations, and clinical patterns of the stable disease.

RESULTS

Plasma ANP levels did not correlate significantly with right atrial or pulmonary arterial pressures but did correlate significantly with both the right ventricular end diastolic volume and right ventricular wall volume measured by magnetic resonance imaging. Oxygen (2 1/min by nasal prongs for 30 minutes) did not change the mean pulmonary arterial pressure or the level of plasma ANP. In 20 patients with an acute exacerbation of COPD plasma ANP levels were higher in those with oedema (302 (185) pg/ml) than in those without oedema (87 (43) pg/ml). Oxygen given for one hour had no effect on plasma levels of ANP. However, plasma ANP levels fell over the first three days during treatment in those with oedema, the fall correlating with the change in body weight. In a further 20 stable patients with hypoxic COPD, those with hypercapnia and previous episodes of oedema had higher levels of plasma ANP (120 (50) pg/ml) than normocapnic patients with no previous oedema (54 (15) pg/ml).

CONCLUSIONS

The level of ANP is high in the plasma of patients with COPD, particularly during exacerbations in those with oedema. The association of a high plasma ANP level and volume overload is shown by the fall in ANP levels with treatment of the oedema, and the correlation between levels of ANP and right ventricular end diastolic or wall volumes.

Regional differences of atrial natriuretic factors in humans

During sinus coronarius catheterization in humans undergoing diagnostic right-sided cardiac catheterization, levels of atrial natriuretic factor (ANF) measured in sinus coronarius (n = 12) were four times higher than in peripheral arterial blood. Atrial natriuretic factor underwent average extractions of 0.57, 0.40, and 0.28 in the kidneys (n = 14), liver (n = 15), and forearm (n = 15) respectively. However, a close relationship was observed between arterial and peripheral venous concentrations. The substantial clearance of ANF even over the forearm indicates that arterial sampling may be preferred in conditions with altered peripheral vascular resistance, since an uptake of ANF in the peripheral vascular bed is likely to have occurred.