Heart block: Failure of the heart's normal rhythm controls leading to arrhythmia. Heart block: Impairment of conduction in heart excitation. It is often applied specifically to atrioventricular heart block. Heart block: recurrent sudden attacks of unconsciousness caused by impaired conduction of the impulse that regulates the heartbeat.
For pet rabbits and show rabbits, pine is completely safe for rabbit litter, especially kiln-dried pine. Kiln-dried pine is also the cheapest rabbit litter on the market. And since it does a comparable job to all the other litters, pine shavings as rabbit litter and rabbit bedding gets our top vote. See Rabbit Bedding for comparisons with several other rabbit bedding materials, and more recommendations.
The floor should be 1/2 x 1 14 gauge galvanized wire (galvanized AFTER weld is best) and the sides and top should be 1 x 2 14 gauge galvanized wire. The door opening should be at least 12 x 12, although bigger is nice. Doors swinging inward will keep the rabbits in just in case you forget to latch the door. Doors that open outward will allow you to more easily get inside the cage without pushing the rabbits aside.