[Hemodynamic state at rest and during maximal bicycle exercise in university students with small cardiac silhouettes on chest radiography].

To clarify the hemodynamic state of an apparently small heart; i.e., a small cardiac silhouette on chest radiography, chest radiographic and echocardiographic studies, physical fitness tests (a battery of tests consisting of vertical jump, side step, floor push-up, and modified Harvard step test) and graded uninterrupted bicycle exercise test were performed. 1. The cardiothoracic ratio (CTR) in 3,461 newly-enrolled university students (18.7 +/- 1.2 years old: mean +/- SD) distributed normally and the mean value +/- SD was 40.2 +/- 3.6%. No difference was observed between male and female students. 2. A small heart was defined as one having a cardiothoracic ratio (CTR) less than or equal to 35% which comprised the lower 10% of the normal distribution. There was no significant difference in results of physical fitness tests between students with small heart (n = 134) and normal controls (n = 136, 45% less than or equal to CTR less than or equal to 50%). 3. A maximal bicycle exercise test was performed in 14 male students with small heart (S: CTR = 31.9 +/- 2.1%) and nine normal controls (C: CTR = 46.5 +/- 1.0%). a) Body weight (S: 57 +/- 7, C: 69 +/- 8 kg, p less than 0.001) were less in students with small heart; Body height was similar in both categories (S: 171 +/- 5, C: 175 +/- 7 cm, NS). b) All controls finished 200 W workload, whereas all students with small heart ceased exercise earlier than the control subjects (three at 125 W, three at 150 W, eight at 175 W). c) Resting heart rate was higher in cases with small heart (S: 92 +/- 14, C: 77 +/- 10 beats/min, p less than 0.02). Left ventricular end-diastolic dimension was smaller in small heart (S: 39 +/- 4, C: 48 +/- 4 mm, p less than 0.001). d) During exercise, blood pressure and oxygen intake at the same workload were similar in both groups, but peak oxygen uptake was higher in the controls (S: 43 +/- 5, C: 50 +/- 7 ml/kg/ml, p less than 0.05). Heart rate and blood lactate concentration were higher throughout exercise in students with small heart (lactate at 175 W; S: 12.7 +/- 1.6, C: 7.8 +/- 2.0 mmol/L, p less than 0.001) (heart rate at 175 W; S: 194 +/- 6, C: 173 +/- 21 beats/min, p less than 0.05). We concluded that hemodynamic conditions at rest and during low grade exercise are preserved in students with small heart.(ABSTRACT TRUNCATED AT 400 WORDS)