Tramadol is a pretty strong opioid painkiller, and combined with dehydration and alcohol could cause respiratory depression to a degree, which is probably more likely.
Heart attack is a poor, generic term that really doesn't tell us anything. It gets used to cover all sorts - infarcts, cardiac arrest, arrhythmias.
He'd be unlikely to suffer an ischaemic event (myocardial infarct from coronary artery disease) at his age and level of fitness. That said, in those with a strong genetic history of coronary artery disease, apparently fit and sometimes quite young men do sometimes have just that.
A cardiac arrest (i.e. heart stops beating properly or at all) may occur, and in the situation of the other things mentioned above including fatigue, dehydration, medication and alcohol could happen secondary to respiratory depression, or from an arrhythmia, which could happen in young fit blokes.
In any event, it sounds like he's OK, which is the main thing. Scary for him, and his team-mates to witness.