For overall physio I like Costanzo, the big "Physiology" text. Her BRS physiology book is great too for touch ups.
If you want a dedicated book just for the cardio in CVS, I can't recommend the book "Pathophysiology of Heart Disease" by Lilly enough. Some of it is more advanced than first year physio (Also GREAT for second year and beyond, so you'll have use for it) but I think the easiest way to understand how things work is see how they don't and this book does a fantastic job. This book really makes all those Frank-Starling curves make sense.