Your heart was pounding because Churrascos (Brazilian Steakhouses) are notoriously high in sodium and you did a 9 mile hike before hand.

You heat up because of the TEF (Thermic Effect Of Food) being much higher for meat than for anything else.

do you have a hiatal hernia? could be a large amount of food pressing on that opening. this can cause your heart to feel like that...look up symptoms of hiatial hernia.

When you overeat you stimulate two competing systems in the central nervous system. The parasympathetic and the sympathetic. The sensation of heart pounding is due to the increased demand placed upon the heart to deliver more blood flow to your gut to deliver the nutrients to the brain. The signal the brain received initially was parasympathetic as soon as the food was smelled or touched your lips and vagus nerve. The vagus nerve is the tenth cranial nerve and it carries parasympathetic fibers from the organs in your mouth and entire GI tract to your transverse mesocolon. This is the basis of the brain gut axis. It's how the brain senses what is occurring in the gut and how it should respond.....so when you eat a lot.....you need more blood flow in your gut. So heart gets more sympathetic flow to increase it's heart rate and less parasympathetic input to slow it. Disease states screw that normal response up.

The heart poundage almost certainly came from the salt in the meat increasing your blood pressure. Increased blood pressure means more force must be generated in the left ventricle to expel blood into the aorta, thus a "pounding".

I sometimes get the same effect. I have noted that eating gelatin balances out the effect.