That is the sound the heart makes as it beats. Or at least if there are no mechanical problems. I got to watch open heart surgery this week. I watched them saw open the sternum, spread the chest cavity, and cut into the pericardium, where inside was the beating heart. Lub dub, lub dub. This patient had an aortic aneurysm and needed an aortic valve replacement. His aorta was huge. I was shocked at how big it was. No wonder people die if they got shot in the aorta!!!! Alright, I watched the beating heart for awhile. Then they put him on the heart-lung machine so that blood could completely bypass the system. After that was done, the doctor paralyzed the heart. So at this point, it's flattened out because of no blood, and not beating. Then the aorta was cut out. I was actually very surprised at the length of aorta removed from the body. He then took the new aorta and put in the new valves. And then the most tedious part of the surgery: sewing the new aorta into the system. Both ends had to be attached plus the coronary arteries had to be routed to the new aorta. He was sewing forever. I think there was something around 160 sutures used throughout the case. After all this is done, they SLOWLY fill the heart with blood, 100 cc at a time, making sure that the system reacted appropriately and that there were no leaks. Then they inserted a chest tube, and began to close him up. They "sew" the sternum back together with thick wire, and then close the outer layers. Sounds easy right? Hah, it was 5.5 hours of stressful surgery.
I was amazed throughout the entire surgery. I'm fairly certain the smile did not leave my face for the first two hours. I think one of the weirdest thoughts was that this man's heart was not beating, his lungs were not inflating, yes his brain was intact and blood was circulating through his system.
This was definitely one of the most memorable days of medical school.