Was I responsible for his death?

"Sir, Please come fast your patient Mr K is gasping...."
By the time I reached the ICU the electrocardiographic monitor was showing a flat line. The Cardiologist was there and also the Urologist and a few others.They all were trying their best to revive the patient.I was summoned to talk to the relatives sitting outside. They gave me the hard job.
Yes it was a hard job.Mr K was my patient for a long time. He was suffering from Coronary Artery Disease and Chronic Obstructive Pulmonary Disease. He was in and out of ICU many times. But for the last few years he was doing fairly well.No Hospitalisation for 26 months. He was cheerful and pleasant Along with his Cardiac and Lung diseases he was also suffering from benign Prostatic enlargement. The Prostate was large enough to obstruct free flow of urine from the Urinary Bladder. He thus was able to pass Urine only through a permanent Catheter put inside his Bladder. 2 years ago he was evaluated for Prostatic surgery [so that he can pass Urine normally] but the procedure was deferred in view of his poor Lungs and Heart.
Seeing him come to my Out Patient Department every month with this urinary catheter I was tempted to rethink about Prostatic surgery. As his general condition seems to have improved during last few months,I had hope that the Prostate surgery could be done now. I referred him to Urologist. He did a complete evaluation and told me if I and the Cardiologist could give a certificate of fitness for surgery he will go ahead with the procedure. The Cardiologist gave a guarded certificate saying there is mild risk of complications including death due to the pre existing illness.I also gave such an opinion.
Some of the relatives were not willing for surgery.But his son was ready.He asked me again and again about the risks.I explained everything and said even though there is a risk it is negligible and you can give the consent. The patient was ready to comply with his son's and my decision. Finally all gave consent and surgery was fixed.

Today was the surgery day. All went all right till a few minutes ago when he suddenly suffered a cardiac arrest in the post operative ward. The attempts to revive was failing in front of my face.
What can I tell them? They believed in me and hoped the urinary catheter will go away and their father will be happy. But now the father is no more. Will they feel that I am responsible for his death.
I went out to see the anxious relatives. In a hushed tone I told them what all had happened. I told them that everything possible was done but unfortunately we could not save him.
Are their faces showing anger at me?
No only stunned disbelief.
I explained that his lungs and Heart suddenly gave away and even if it did not happen now it might have happened some days later. They took it well and there were no accusations.
But still I continue to ask the question again and again.
Was I responsible for his death? May be yes in an indirect way.