Can you explain the differences between angina, heartburn, and myocardial infarction, as their symptoms can sometimes overlap?

Angina: 
Angina is chest discomfort or pain that occurs when there is a temporary reduction in blood flow to the heart muscle. It's often a sign that the heart isn't getting enough oxygen. Angina typically feels like pressure or squeezing in the chest, and it can radiate to the neck, jaw, shoulder, or arm. It often occurs during physical exertion or stress and usually subsides with rest or medication, which dilates the coronary arteries.

Heartburn:
Heartburn is a burning sensation or discomfort in the chest or throat, often caused by stomach acid refluxing into the esophagus. It can feel like a fiery, acidic discomfort, but it's not related to the heart or the blood vessels. Heartburn usually occurs after eating, when lying down, or during sleep. It can often be relieved by antacids or changes in posture.

Myocardial Infarction (Heart Attack):
A heart attack occurs when there is a blockage in one of the coronary arteries, leading to a significant reduction or complete halt of blood flow to a portion of the heart muscle. The symptoms of a heart attack can be similar to angina but are typically more intense and prolonged. They include severe chest pain or discomfort, shortness of breath, sweating, nausea, and pain that can radiate to the left arm, shoulder, jaw, or back. Unlike angina, rest or medication doesn't usually alleviate the symptoms of a heart attack.