sinus tachy - just means your heart is beating at regular intervals (regular rhythm) but faster than normal (60-100bpm)
poor r wave progression can refer to many issues but may also be from poor placement of electrodes or their conduction.
low qrs voltage can be due to heart disease but you cannot diagnose it from an ecg alone.
Sinus tachycardia
Poor R wave progression
Low QRS voltages in precordial leads
Abnormal ECG