Dear Jaz,
In response to your question about how quickly heart problems can manifest themselves the answer is very rapidly. The onset of an MI or even sudden death can occur without warning. The real question is whether your symptoms are due to your heart or something else. There are many potential causes of chest pain. The one that doctors worry about the most is cardiac because it has the potential to be life-threatening. Once this is ruled out the work-up can proceed at a more leisurely pace.
Amongst the cardiac causes of chest pain are: ischemia (due to blockages - including both stable and unstable angina and acute heart attack and coronary artery spasm), pericarditis (inflammation of the sack around the heart), myocarditis (inflammation of the heart), cardiomyopathy (heart failure) and rarer causes such as coronary artery dissection, acute rupture of the heart and valves and infections of the pericardium.
Gastrointestinal causes of chest pain include reflux (acid from the stomach washing back into the esophagus), gallstones, esophageal spasm, esophageal rupture, varicose veins of the esophagus, strictures of the esophagus, tumors of the esophagus and other less common GI problems.
Pulmonary (lung) causes include pneumonia, pulmonary embolus, pneumothorax, pleuritis and bleb rupture.
Other potential causes are aortic dissection, back and spine problems and musculoskeletal (muscle strain, rib fracture, etc.).
Psychological causes of chest pain are common and include panic attacks, anxiety, stress and mental duress.
As you can see the list of potential causes in long and may take a little bit of time to determine the precise cause. A good Internal Medicine doctor should be able to work through the potential causes of your symptoms.
I hope you find this information useful. Information provided in the heart forum is for general purposes only. Only your physician can provide specific diagnoses and therapies.