There is no doubt regarding a higher chance that the next baby may be born with heart disease.
The only drug known to decrease the incidence of birth defect of the heart is Folic acid. But to be effective it should be taken before conception. Get in touch with your obstetrician/gynaecologist doctor for further advice.
You can no doubt attempt another conception provided you are on Folic acid and one should perform a heart scan (Fetal echocardiography) of the fetus between 16-20 weeks of pregnancy. The timing is very important so that decisions on termination of pregnancy can be taken if any complex disease is detected.
There is usually no need for chromosome study unless a routine ultrasound shows something suspicious.