positive sinoatrial chronotropic effect

例句：

1. 1. The drug has a positive inotropic effect on the heart.
   这种药物对心脏有正性肌力作用。
2. 2. The study found that exercise had a positive inotropic effect on the heart.
   研究发现，锻炼对心脏有正性肌力作用。
3. 3. The medication was effective in treating patients with heart failure, due to its positive inotropic effect.
   该药物对患有心力衰竭的患者有效，因为它具有正性肌力作用。