Monday, March 19, 2012
For most fans, sudden death is part of the game that is settled on the field; next score wins. In medicine, sudden death occurs when the heart short circuits, stops beating and causes unexpected collapse and death. This weekend, during a soccer match in England, the medical term played out in front of a packed stadium. Spectators watched as Fabrice Muamba collapsed and then witnessed paramedics began CPR and attempted to restart his heart with an AED.
Mr. Muamba wasn‘t as fortunate as some with sudden cardiac death where the AED recognizes the fatal rhythm, ventricular fibrillation, and delivers an electric shock and restarts the heart’s ability to beat. Muamba’s heart didn’t start right away and it took two hours of work in the hospital for a spontaneous heart beat to return. Medications were likely used to help restart the heart while paramedics, nurses CPR was continued, trying to keep blood circulating to his brain and organs. The final result of this sudden death won’t be known for some time. It only counts as a win if Mr. Muamba leaves the hospital as a person, not as a body.
Two hours is a long time to continue CPR but heroic efforts are often performed on infants, children and young adults because there is potential for a save. They usually have normal heart muscle but some glitch has caused the electrical system to fail. In babies, that glitch is usually a breathing complication that decreases oxygen supply to the heart muscles and in young adults it may be spontaneous onset of ventricular fibrillation where the electrical system short circuits. In older patients, the heart isn’t as resilient and the longer the CPR, the less likely that a spontaneous heart beat will return.
In sudden cardiac death the ventricle, or lower pumping chamber of the heart, develops a disorganized rhythm called fibrillation. The electrical impulses aren’t occurring at the same time and each heart muscle fiber contracts at a different time. The ventricle muscle isn’t coordinated and is unable to generate a squeeze to push blood out to the body. This is different than the commonly seen and not life threatening atrial fibrillation, where the upper chambers of the heart lack coordination but this does not stop the heart for circulating blood to the body (A fib has its own complication though and should not be ignored).
With prolonged CPR, there may be some minor victories where the heart restarts. A pulse can be felt, but is there a blood pressure. What is the rhythm on the monitor and is it one that can sustain itself or will it degenerate into something that can’t produce a pulse. This is a critical time for the resuscitated heart and the electrical rhythm can change quickly, literally second by second. And if the pulse goes away, regardless of what the monitor shows, CPR needs to start again. A little success spurs the team to try harder and longer and hope that the next round of drugs or the next shock will work…and sometimes it does.
If the cause of sudden death was ventricular fibrillation, then an implantable defibrillator may be the next step. It’s about the size of a pacemaker and is placed the same way in a small skin pocket in the chest wall. If another episode of ventricular fibrillation is detected, it can fire immediately and hopefully return the heart to a normal electrical state. The device also allows patients to return to a normal life and even an athletic one. Medtronics, a company that makes defibrillators, is also a sponsor of the Twin Cities Marathon and their foundation honors people who have returned to running (http://www.medtronic.com/2011globalheroes/our_heroes.html)
Victory in the ER is only one battle and many more need to be fought before the war can be won. The patient needs to be cooled since studies suggest that lower body temperature allows some increased brain recovery. The patient needs to wake up enough to breathe on their own and then, if they are fortunate, they regain consciousness and are able to return to normal like. Mr. Muamba has survived the first battle. His heartbeat has been restored. We hope that he is able to win in sudden death.