According to Action on Smoking and Health - UK, one of the immediate effects of secondhand smoke exposure is to reduce coronary blood blow.
ASH UK's main web page about secondhand smoke states: "Exposure to SHS has immediate health effects. It can reduce lung function; exacerbate respiratory problems; trigger asthma attacks; reduce coronary blood flow; irritate eyes; and cause headaches, coughs, sore throats, dizziness and nausea."
ASH UK back up its contention that brief exposure to secondhand smoke reduces coronary blood flow by referring to the 2001 article by Otsuka et al.
The Rest of the Story
The problem is that the 2001 article by Otsuka et al. found the exact opposite of what ASH UK is claiming. That article found that 30 minutes of secondhand smoke exposure had no effect on coronary blood flow in exposed nonsmokers.
All you have to do is read the abstract of the study to find out that: "Passive smoking exposure had no effect on basal coronary flow velocity in either group."
If you look at Table 1, you'll see that the baseline coronary flow velocity in nonsmokers was 20.2, and that after 30 minutes of exposure to secondhand smoke, the coronary flow velocity was 20.7. Thus, there was no difference in baseline coronary blood flow in nonsmokers exposed briefly to secondhand smoke.
The study did find a reduction in coronary flow velocity reserve. This means that after the intravenous infusion of ATP, the coronary flow velocity in nonsmokers was reduced (just as it would be if the subject ate a hamburger, breathed in car fumes, or experienced a stressful task).
By conflating coronary flow velocity reserve with coronary blood flow, ASH UK is able to create the impression that brief exposure to secondhand smoke can reduce the flow of blood through the coronary arteries and thus put a person at risk of a heart attack. This is certainly a lot scarier than telling people that brief tobacco smoke exposure reduces your coronary flow velocity reserve, similar to what would occur if you ate a hamburger or tater tots.
Would anyone credibly argue that eating tots reduces coronary blood flow? Other than the Anti-Tater Tot Coalition, I'm not aware that anyone would make such a claim. But the research supporting such a claim is the same as that being used to support the statement that 30 minutes of tobacco smoke exposure reduces coronary blood flow in nonsmokers.
For more on the issue of conflating coronary flow velocity reserve with coronary blood flow, see my previous post.