Hello,
If you have a history of high blood pressure, the Left ventricular thicking aka Left Ventricular Hypertrophy (LVH) is most likely a result of your heart thickening due to elevated blood pressure.If blood pressure is not well controlled, the heart muscle can thicken as a result of having to pump against higher pressures. The best thing to do for this is to make sure that your blood pressure is well controlled. There are other causes of thickening of the ventricle like hypertrophic cardiomyopathy and aortic valve stenosis, but those things would have likely be seen on the echocardiogram and would have been mentioned by your doctor. The best thing you can do to decrease your chance of having heart problems in the futre would be to stop smoking, control your blood pressure and diabetes, and lose weight if obesity is an issue.
Coming from someone who has walked the walk of cardiac issues for 25 years, and is currently back in college concentrating on the heart and in the radiology area, all I can say is have faith. :) Take a deep breath and relax and be in peace. You need to discuss with your Dr what if anything you need to be doing for this. There have been many advances in the last 25 + years and it may not be as bad as what you may think. I would recommend that you do stop smoking, and loose wt. Keep your diabetes in check and ask the Dr. how he wants you to manage your BP and Cholesterol.
As far as getting worse, you need to see your Dr regarding that. With me, I needed a heart transplant at the age of 28 and now at 53 with grand-kids, I am a grandma college student. I still have the same heart. I actually got better with the help of God and medical therapy. I personally never had a heart attack from occluding vessels. But I did have other issues that they and I have been able to manage.