Hi, as what I understand we are dealing with two Co existing conditions, copd affecting your lung and rca block as you say affecting your heart, mostly pneumonia must have predicated a copd exaberation which would have brought your oxygenation down temporarily leading to arrest, if as you that point of time arterial sample had normal oxygenation, we should think of some arrhythmia which can cause cardiac arrest because of ischaemia heart, however in most possibility pneumonia may have precipitated arrhythmia. I do suggest heart check up and appropriate meds for heart and copd to be taken religiously, also lifestyle precautions, immunisation to prevent recurrence of another infection should be top priority Regards Dr priyank mody