It might be due to early onset of dementia or you might have been in depression
secondary to your cardiac problems. Analyze yourself properly that you are suffering with the symptoms of depression or it is purely forgetting.
A few tips to reduce memory deterioration in case of dementia is that a research says that taking almonds on a regular basis will keep your brain healthy that in turn stops fading memory. Taking a spoon of turmeric powder in a glass of water or in any form of food will help your memory stops fading.