The ECG is an unsensitive tool for diagnosis of left ventricular hyperthrophy. It only detects between 20-50% of LVH. You'll have to keep in mind that sometimes there are false positive or false negative results. There are other and better tests for diagnosing this condition, such as the one you'll be having. Hypertensive people with a target organ damage with heart failure almost always show evidence of LVH.
Did you have a chest x-ray done? If the LVH is present, it will show an abnormal shape of your heart, including any enlargments. However, it is no more reliable as a diagnostic test than an ECG. LVH is often associated with LV diastolic dysfunction.
The LVH is diagnosed if the thickness of myocardium is >1.1cm. The good news is that it is not permanent - it is reversible with a reduction in blood pressure.
The echocardiogram you'll be having will show any remodeling of the LV, overall mass of the LV, valve size and function, chamber sizes and assess the biventricular systolic and left ventricular diastolic functions. It will also determine your ejection fraction. This test is much better than an ECG.
Should you be diagnosed with LVH, it is not such a great concern as long as your blood pressure remains well controlled.
Good luck and try not to worry!