Correlation between left ventricular mass and the resting and post-exercise release of ANP in healthy men.

BACKGROUND

The goal of our study was to assess the impact of left ventricular mass on the resting and post-exercise release of atrial natriuretic peptide (ANP) in healthy young men.

MATERIAL AND METHODS

The study involved 36 young men divided into two groups. Group I consisted of 18 healthy untrained men 20-24 years old (mean 22.1). Group II included 18 healthy men aged 22-27 years (mean 23.4 years) who had been taking regular dynamic and static physical exercise for at least 2 years. Echocardiograms were performed in both groups. The thickness of the posterior wall (PW-d), the thickness of the interventricular septum (IV-d), and the left ventricular end-diastole dimension (DdLV) were measured and used to calculate the left ventricular mass. Subsequently, all the patients underwent an exercise test on a cycloergometer. The workload in both groups was 2 Watts/kg at 60 rpm. The anticipated age-adjusted heart rate values at this workload were 170/min in Group I and 155/min in Group II. Blood samples were collected before the exercise test and 1 minute afterwards. The concentrations of ANP and sodium ions and the hematocrit index were measured.

RESULTS

In Group I the mean left ventricular mass was 193.1 +/- 51.8 g; in Group II, 248.1 x 91.91 g, which is a statistically significant difference. The resting ANP concentration in Group I was higher than in Group II (24.44 +/- 12.35 pg/ml vs 21.39 +/- 11.03 pg/ml), but the difference was not statistically significant. After exercise there was a significant increase in ANP concentration in both groups: 53.89 +/- 39.98 pg/ml and 47.50 +/- 26.67 pg/ml respectively. There was no correlation between the ANP concentration before and after exercise and the left ventricular mass in either group. There were also no differences between the two groups in resting hematocrit: 48% in Group I and 49.5% in Group II. A significant increase in hematocrit was observed in both groups after exercise. Exertion induced a significant decrease in the plasma sodium concentration in both groups. The ratio of mean plasma ANP concentration at rest to left ventricular mass, corrected according to hematocrit values, was 6.10 in Group I and 4.25 in Group II; after exercise, 14.06 and 9.72 respectively. The ratio of post-exercise increase in ANP concentration to left ventricular mass was 7.6 in Group I and 5.32 in Group II. The average left ventricular mass in Group II, although 30% greater than in Group I, did not exceed 259 g, which is considered the upper limit of normal. Despite this difference the ANP concentration in Group II was ca. 20% lower than in Group II, without cardiac hypertrophy. In both groups a significant increase in ANP concentration was observed when the subjects were exposed to submaximal workload. In Group II, however, the increase was markedly lower. No correlation was found between left ventricular mass at rest and post-exercise ANP release, nor between left ventricular mass and ANP secretion. By contrast, a tendency towards lower ANP release was found in Group II, despite the markedly larger left ventricular mass.

CONCLUSIONS

In the evaluation of risk related to left ventricular hypertrophy, both the mass index and cardiac functional efficiency should be taken into account.