Can you explain how triglycerides affect your heart?

High LDL-P. High triglyceride (tg) is a common marker for high LDL particle number (ldl-p). As tg rise ldl-p rises. However, when tg is high the amount of cholesterol carried by LDL particles goes down. This often results in "normal" LDL cholesterol (ldl-c) and low hdl-c levels despite high (ldl-p). When ldl-p is high cardiovascular risk is high independent of ldl-c, hdl-c, or tg levels.
Atherosclerosis. Triglycerides is essentially fat, which can cause atherosclerosis along with cholesterol and cause blockage in the coronary arteries that feed heart muscle.
Atherogenic. Triglycerides like cholesterol are a fatty substance in the blood which if abnormally elevated lead arterial atherosclerosis. The levels of triglycerides are related to dietary intake of carbohydrates and sugars and are often elevated in diabetics or obese individuals. Diet, exercise, and weight loss will usually brings levels to normal. If not then fish oil, Niacin or fenofibrates are added.